JP2002043211A - Aligner and exposure system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aligner which can measure the surface positions of a plurality of marks formed on an object with high accuracy even when the level differences between the surfaces of the marks and the surface of the object differ at every mark. SOLUTION: The aligner measures the surface position of a street line SL with respect to the alignment marks AM formed on the line SL by irradiating the surface of the line SL which is different from the marks AM with light ILX. The aligner also measures the surface position of a wafer by irradiating a device portion DPk on which a pattern is formed with light ILY. Then the aligner finds the surface positions of the marks AM by finding the level difference between the device portion DPk and the line SL from the measured results and subtracting the level difference from the surface position of the wafer, and then, adding the heights of the marks AM to the remainder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alignment apparatus for aligning a photomask and an object such as a substrate in a process of manufacturing a device such as a semiconductor element or a liquid crystal display element, and forming the alignment on the photomask using the apparatus. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus that exposes an image of a set pattern onto an object via a projection optical system, and particularly to an alignment apparatus and an exposure apparatus that perform focusing on the substrate.

[0002]

2. Description of the Related Art In the manufacture of devices such as semiconductor elements and liquid crystal display elements, an image of a fine pattern formed on a photomask or a reticle (hereinafter, these are collectively referred to as a reticle) using an exposure apparatus is exposed to a photoresist. The projection exposure is repeatedly performed on a substrate such as a semiconductor wafer or a glass plate coated with a photosensitive agent such as a photosensitive agent. When performing projection exposure, it is necessary to precisely match the position of the substrate with the position of the pattern image formed on the reticle to be projected. The exposure apparatus is provided with an alignment apparatus for performing this alignment. The alignment apparatus includes an alignment sensor that detects a position of an alignment mark formed on a substrate, and a control system that performs alignment of the substrate based on position information of the alignment mark detected by the alignment sensor.

Since the surface state (roughness) of a substrate to be measured changes during the manufacturing process of a semiconductor element, a liquid crystal display element, or the like, it is difficult to accurately detect the position of the substrate with a single alignment sensor. Generally, different sensors are used according to the surface condition of the substrate. The main alignment sensors are LSA (Laser StepAl).
ignment), FIA (Field Image Alignment), and LIA (Laser Interferometric Alignment). Hereinafter, outlines of these alignment sensors will be described.

An LSA type alignment sensor irradiates a laser beam onto an alignment mark formed on a substrate,
It is an alignment sensor that measures the position of an alignment mark using light that has been diffracted and scattered, and has been widely used for semiconductor wafers in various manufacturing processes. The FIA type alignment sensor is an alignment sensor that illuminates the alignment mark using a light source having a wide wavelength band such as a halogen lamp and performs image processing on an image of the obtained alignment mark to perform position measurement. This is effective for measuring asymmetric marks formed on layers and substrate surfaces. The LIA type alignment sensor irradiates laser beams having slightly different wavelengths from two directions to a diffraction grating alignment mark formed on the substrate surface (two beams incident) and interferes with the two resulting diffracted lights. The alignment sensor detects the position information of the alignment mark from the phase of the interference light.
This LIA type alignment sensor is effective when used for an alignment mark having a low step or a substrate having a large surface roughness. As an LIA type alignment sensor, in addition to the above-described two-beam incidence method, a single beam is irradiated onto a mark, and the resulting two diffracted lights traveling in different directions at the same diffraction angle are caused to interfere with each other. There is also a method for detecting the interference light.

In general, an optical system is provided with an auto-focus mechanism. However, in an alignment sensor, a surface to be detected is set within a predetermined range from the alignment sensor (this is also called "focusing"). An auto focus mechanism is provided. The autofocus mechanism irradiates a light beam for detection onto an alignment mark to be measured, and detects a position (focus position) of the surface to be measured in an optical axis direction from reflected light; And a drive mechanism for setting the position to a predetermined position.

Next, a conventional alignment sensor will be described. FIG. 10 is a diagram showing a configuration of a conventional off-axis type alignment sensor. In FIG. 10, an alignment sensor 100 includes an optical fiber 101.
The illumination light IL10 is guided from an external illumination light source such as a halogen lamp via the. The illumination light IL10 is applied to the field-of-view dividing stop 103 via the condenser lens 102. FIG. 11A is a diagram illustrating an example of the field-of-view dividing stop 103. As shown in the figure, the field division stop 103 has a mark illumination stop 2 having a wide rectangular opening at the center thereof.
00 and focus detection slits 201 and 202 formed by a pair of narrow rectangular openings arranged so as to sandwich the mark illumination stop 200. Illumination light IL10
A first light flux for illuminating a mark that illuminates the alignment mark area on the wafer W by the field-of-view dividing aperture 103;
The light beam is divided into a second light beam for focus position detection prior to alignment.

[0007] The illumination light IL20 divided in this manner is divided into visual fields.
Is transmitted through the lens system 104, reflected by the half mirror 105 and the mirror 106, reflected by the prism mirror 108 via the objective lens 107, and formed in the street line SL on the wafer W as shown in FIG. The mark area including the alignment mark AM and the vicinity thereof are irradiated. FIG. 12 is a diagram for explaining an illumination area on the wafer W of the conventional alignment sensor 100.
The reflected light of the exposure surface of the substrate W when the illumination light IL20 is irradiated is reflected by the prism mirror 108, and is reflected by the objective lens 1
07 and reflected by the mirror 106, and then pass through the half mirror 105.

Thereafter, the light reaches the beam splitter 110 via the lens system 109, and the reflected light is branched in two directions.
The first split light transmitted through the beam splitter 110 forms an image of the alignment mark AM on the index plate 111. Then, this image and light from the index mark on the index plate 111 are incident on the image sensor 112 composed of a two-dimensional CCD, and the alignment mark A is formed on the light receiving surface of the image sensor 112.
An image of M and the index mark is formed. On the other hand, the second split light reflected by the beam splitter 110 is
3 is incident.

FIG. 11B is a diagram showing an example of the light shielding plate 113. As shown in FIG. The light-shielding plate 113 shown in FIG. 11B shields light incident on a rectangular area denoted by reference numeral 205 and transmits light incident on an area 206 other than the rectangular area 205.
Therefore, the light shielding plate 113 blocks the branched light corresponding to the first light flux and transmits the branched light corresponding to the second light flux. The split light transmitted through the light shielding plate 113 is transmitted to the pupil splitting mirror 1
In a state in which the telecentricity is broken by 14, the light enters a line sensor 115 composed of a one-dimensional CCD, and a focus detection slit 201,
An image 202 is formed. Here, the substrate W and the image sensor 1
When the substrate W is displaced in a direction parallel to the optical axis of the illumination light and the reflected light, the image of the alignment mark AM formed on the light receiving surface of the image sensor 112 is secured because the telecentricity is secured between the alignment mark AM and the substrate 12. Is defocused without changing the position on the light receiving surface of the image sensor 112.

On the other hand, since the reflected light incident on the line sensor 115 has lost its telecentricity as described above, when the substrate W is displaced in a direction parallel to the optical axis of the illumination light and the reflected light. The images of the focus detection slits 201 and 202 formed on the light receiving surface of the line sensor 115 are displaced in a direction intersecting the optical axis of the branched light.
By utilizing such properties and measuring the amount of deviation of the image on the line sensor 115 from the reference position, the position (focal position) of the illumination light and reflected light of the substrate W in the optical axis direction is detected. For details of this technology, see, for example,
See U.S. Pat. No. 3,210,030.

[0011]

By the way, taking the production of a semiconductor device as an example, the production is currently carried out with a process rule of about 0.25 μm, but the demand for miniaturization is further increased, and in the future, the production of 0.1 μm CPU (Central Processing Unit) and RAM (RandomAccess)
Memory) is being planned, and in such a situation, further improvement in alignment accuracy is required. Generally, alignment accuracy is 1/3 of required resolution
Therefore, an alignment accuracy of about 30 nm is required for a resolution of about 0.1 μm.

In the above-mentioned conventional alignment apparatus, as shown in FIG.
Mark illumination aperture 20 formed in field division aperture 103
The image of 0 is radiated on the substrate W as an image 210, and the images of the focus detection slits 201 and 202 are radiated on the substrate W as images 211 and 212, respectively. FIG. 12B is a cross-sectional view taken along the line AA in FIG.
Reference numerals 2 and R3 denote regions irradiated with the images 210, 211, and 212, respectively. Here, the mark illumination field stop 200 and the focus detection slits 201 and 202 are provided in the field division stop 103, and an image 210 of the mark illumination field stop 200 is irradiated onto the alignment mark AM as shown in FIG. And focus detection slits 201 and 20
Irradiating the second images 211 and 212 to a position different from the position where the alignment mark AM is formed has an effect when the images 211 and 212 of the focus detection slits 201 and 202 measure the position information of the alignment mark AM. In order not to affect.

When the processing of the substrate W is performed a plurality of times, the device portion DP on which the circuit pattern is formed is formed.
And the step between the alignment mark AM and the surface position of the alignment mark AM increase. That is, when asking the height position of the surface of the device portion DP and the height position of the surface of the alignment mark AM,
A large step occurs. This is because the device portion DP is subjected to a process such as formation of an insulating film, and the street line SL is not subjected to a process, or even if the process is performed, it is removed by etching or the like.

In such a case, the focus position of the alignment optical system detected by the focus position detection operation is not the optimum focus position for the alignment mark AM but the optimum focus position for the device portion DP. Therefore, when the alignment is performed, when the substrate W is positioned based on the detection result detected as described above, the alignment mark AM is formed by the step between the surface of the alignment mark AM and the surface of the device portion DP. Are offset. As a result, the image of the alignment mark AM is formed on the light receiving surface of the image sensor 112 in a state where it is defocused by an amount corresponding to the offset, so that high-precision alignment becomes difficult. Therefore, it is general to add or subtract an appropriate offset value prepared in advance to the detected focus position of the alignment optical system to obtain the focus position on the surface of the alignment mark AM.

In recent years, not only adjustment of the position and rotation of the substrate W, but also adjustment of the position and rotation of each of a plurality of shot regions formed on the substrate W have been performed for each of the plurality of shot regions. A technique called so-called multi-point in-shot alignment measurement, in which a plurality of alignment marks AM are formed by measuring the position information of the plurality of alignment marks AM, is being used. FIG.
(A) shows a state where device parts DP1 to DP5 and two alignment marks AMa and AMb are provided for each shot area on the substrate W. In the in-shot multipoint alignment measurement, for example, with reference to DP1, alignment marks AM1a and AM1a formed at different positions will be described.
1b is to measure the position information. Here, considering the case where the alignment marks AM1a and AM1b are measured by the method shown in FIGS. 11 and 12, the AF measurement position (focus measurement position) when measuring the alignment mark AM1a is AF1a and the alignment mark AM1b. The AF measurement position when measuring is AF1b. AF for both alignment marks AM1a and AM1b
If the device portions at the measurement positions AF1a and AF1b have the same height, there is only one appropriate offset value as described above, but there is no guarantee that the device portions are uniform in height everywhere. Therefore, the AF measurement position AF1
a, when the heights of the AF1b are different, it is possible to obtain accurate height position information of all the alignment marks AM to be measured simply by adjusting an appropriate offset value as in the related art. Can not.

In recent years, a so-called system LSI technology has been developed in which different types of device patterns are formed in a composite manner in the device portion DP. In this system LSI, for example, as shown in FIG. 13 (b), AF measurement positions AFa, A when measuring alignment marks AMa, AMb formed in association with the device portion DP.
The device pattern in Fb is different. Therefore, even in such a system LSI, there is a possibility that accurate height position information of all the alignment marks AM to be measured cannot be obtained simply by adjusting an appropriate offset value as in the related art. .

In FIGS. 13A and 13B described above, FIG.
As shown in 1 and 12, an AF measurement position at the time of alignment measurement is used as a device portion. Apart from this, a technique for performing AF measurement on a street line is also known.
FIG. 13C shows a state where AF measurement is performed on a street line. In the vicinity of each shot area,
Two alignment marks AM to be measured this time
a, AMb, and an alignment mark AMa ′ used during alignment measurement of the previous layer (not a target of measurement this time) are formed together. See Figure 6 below.
When performing alignment measurement using the configuration of FIG. 7, no other alignment mark is formed on the AF measurement position AFb (street line) at the time of measuring the alignment mark AMb. By adjusting the appropriate offset value representing the surface of the alignment mark AMb, accurate height position information of the alignment mark AMb can be obtained. While measuring the alignment mark AMa
On the F measurement position AFa, the alignment mark AMa ′ used in the previous process is formed. Therefore, even if the offset value used as the offset earlier in the measurement result at the AF measurement position AFb is added to or subtracted from the AF measurement result at the AF measurement position AFa, the alignment mark AMa
Cannot obtain accurate height position information.

The present invention has been made in view of the above circumstances, and even if a step between the surface of a plurality of marks formed on an object and the surface of the object is different for each mark, the surface of each mark is different. In addition to providing an alignment device that can measure the position of the mark with high accuracy and can measure the position information of the mark with high accuracy while focusing on the surface of each mark, the alignment device can measure the position information with high accuracy It is an object of the present invention to provide an exposure apparatus that can perform an exposure process in a state where positioning is performed with high accuracy based on position information obtained.

[0019]

In order to solve the above-mentioned problems, an alignment apparatus according to a first aspect of the present invention comprises a plurality of marks (AM, AM1,
AM2), a position information measuring system (24, 25, 38,...) For measuring position information in a predetermined two-dimensional plane (XY plane).
39, 40) and the marks (AM, AM1, AM2)
Focus position information in a direction (Z-axis direction) perpendicular to the two-dimensional plane (XY plane) of the object (W) at a focus measurement position set at a position on the object (W) different from the formation position of the object Position measurement system (24, 2
8, 29, 30, 31, 32, 33, 34, 35, 3,
6, 37), in the vertical direction (Z-axis direction) between the surface of the object (W) at the focus measurement position and the surface of the mark (AM, AM1, AM2). The step information is indicated by the mark (AM,
AM1 and AM2). According to the present invention, since step information in the vertical direction between the surface of the object at the focus measurement position and the surface of the mark is stored for each mark, the focus measurement position at which the focus position information of the object in the vertical direction is measured Is set to a position different from the mark formation position, and the position of each mark surface is obtained based on the step information even when the surface position of the object is changing according to the focus measurement position. be able to. The alignment apparatus according to a second aspect of the present invention is the alignment apparatus according to the first aspect, wherein the focus position measurement system (24, 28, 2) is provided at the focus measurement position.
9, 30, 31, 32, 33, 34, 35, 36, 3,
Based on the focal position information and the step information measured in 7), the position information measurement system (24, 25, 38, 3)
9, 40) according to the mark (AM, AM1, AM2)
And moving control means (6, 10, 11) for controlling the position of the object in the vertical direction (Z-axis direction) when measuring the position information.
According to the present invention, the position of the object in the vertical direction is controlled based on the step information stored in the storage means and the measured focal position information. As a result, the focus position of the alignment device can be adjusted to the mark surface, and the measurement accuracy of position information of each mark in a two-dimensional plane can be improved. In the alignment apparatus according to a third aspect of the present invention, in the alignment apparatus according to the first aspect or the second aspect, the object (W) may be a substrate (SA) on which a plurality of shot areas (SA1 to SAn) are formed. W), and a plurality of the marks (AM, AM1, AM2) are respectively provided in the shot areas (SL1 to SAn).
Is formed. According to the present invention, when performing so-called multi-point intra-shot alignment measurement in which a plurality of marks formed in a shot area are measured to correct a position shift in each shot area in a two-dimensional plane, each mark is Even when the surface of the object at the focus measurement position is changing, the surface of each mark can be adjusted to the focus position of the alignment device, and position information of the mark in a two-dimensional plane can be measured with high accuracy. be able to. As a result, the displacement of each shot area in the two-dimensional plane can be corrected with high accuracy. The alignment apparatus according to a fourth aspect of the present invention is the alignment apparatus according to the third aspect, wherein the mark (AM, AM1, AM2) and the focus measurement position are provided between the shot areas (SA1 to SAn). It is set at different positions on the set street line (SL, SL _X , SL _Y ). Also,
Fifth aspect by the alignment device of the present invention, in the alignment device according to the fourth aspect, the street line _{(SL, SL X, SL Y} ) is, the first direction (X axis direction) and second direction (Y-axis Direction), and the focal position measuring system (24, 28, 29, 30, 31, 32, 3)
3, 34, 35, 36, 37), but the longitudinal direction is the first
A first measurement system (24, 28, 30, 32, 33, 33) for irradiating the first detection light (IL _X ) set in the direction (X-axis direction)
34, 35, 36, and 37) and a second irradiation of the second detection light (IL _Y ) set in the second direction (Y-axis direction).
Measurement system (24, 29, 31, 32, 35, 36, 37)
Are provided. An alignment apparatus according to a sixth aspect of the present invention is the alignment apparatus according to the fifth aspect, wherein the focus position measurement system (2
4, 28, 29, 30, 31, 32, 33, 34, 3
5, 36, 37) compares the intensity of the reflected light of the first detection light (IL _X ) with the intensity of the reflected light of the second detection light (IL _Y ), and according to the comparison result, the first light. Measurement system (24, 2
8, 30, 32, 33, 34, 35, 36, 37) or the second measurement system (24, 29, 31, 32, 35, 3).
6, 37) is selected to perform focus detection. An alignment apparatus according to a seventh aspect of the present invention is the alignment apparatus according to the sixth aspect, wherein the focus position measurement system (24, 28, 29, 3) is used.
0, 31, 32, 33, 34, 35, 36, and 37) The focal position information measured by using the step information is corrected to store focal position information for the mark (AM, AM1, AM2). Focus position storage means (17)
It is characterized by having. An alignment apparatus according to an eighth aspect of the present invention is the alignment apparatus according to the seventh aspect, wherein the corrected focal position storage means (1
7) marks (AM, AM) relating to the shot area to be measured first among the shot areas (SA1 to SAn).
1, AM2) is stored. According to the present invention, the focus position of the mark regarding the shot area to be measured first is stored. Therefore,
For the remaining shot areas, the process of obtaining the focal position information by adjusting the vertical position of the substrate based on the stored focal position information and measuring the positional information in a two-dimensional plane can be omitted, so that the processing for each mark can be omitted. Position information on a two-dimensional plane can be measured with high throughput. Also,
An alignment apparatus according to a ninth aspect of the present invention is the alignment apparatus according to the seventh aspect, wherein the substrate (W)
Are provided in units of lots each including a plurality of sheets, and the correction focal position storage means (17) stores marks (AM, AM1, AM) formed on a substrate (W) to be measured first.
It is characterized in that the focus position information of 2) is stored.
According to the present invention, the focus position information of the mark formed on the substrate to be measured first is stored in the storage means. Therefore, for the remaining substrates, the process of obtaining the focal position information by adjusting the vertical position of the substrate based on the stored focal position information and measuring the positional information in the two-dimensional plane can be omitted. Position information in a two-dimensional plane can be measured with high throughput. Further, an alignment apparatus according to a tenth aspect of the present invention is the alignment apparatus according to the seventh aspect, wherein the corrected focal position storage means (17) includes a plurality of substrates (W) measured from the head of the lot. The average value of the measurement results of the focal position information for each of the corresponding marks (AM, AM1, AM2) respectively formed on the marks (AM, AM1, AM2)
It is characterized in that it is stored every time. According to the present invention, the focal position information for each mark is measured for a plurality of substrates from the beginning of the lot, and the average value of the measurement results is stored for each mark. Therefore, even when the surface flatness varies between the substrates, the position of the substrate in the vertical direction is adjusted based on the average value stored for the remaining substrates to measure the position information in the two-dimensional plane. Thus, position information for each mark can be measured with high throughput. Further, an alignment apparatus according to an eleventh aspect of the present invention includes:
The alignment apparatus according to any one of the seventh to tenth aspects, wherein the corrected focus position storage means (1
7) a vertical movement control means (6, 10, 11) for moving the substrate (W) in the vertical direction (Z-axis direction) based on the focal position information stored in the position information measurement system (24). , 25, 38, 39, 40), after the movement of the substrate (W) by the vertical movement control means (6, 10, 11), the two-dimensional plane (XY plane) of the mark (AM, AM1, AM2). It is characterized by measuring position information in the inside. According to the present invention, the position of the substrate in the vertical direction is controlled based on the corrected focal position information. As a result, the focus position of the alignment device can be adjusted to the mark surface, and the measurement accuracy of position information of each mark in a two-dimensional plane can be improved. Further, the exposure apparatus of the present invention provides a mask (R)
An exposure apparatus for exposing a predetermined pattern formed thereon onto a substrate (W), comprising: an alignment apparatus according to any one of the first to eleventh aspects, wherein the alignment apparatus obtains a measurement result of the alignment apparatus. Relative positioning of the mask (R) and the substrate (W) based on the image and exposing an image of a predetermined pattern formed on the mask (R) to the substrate (W). And According to the present invention, the alignment between the mask and the substrate is performed based on the position information measured with high accuracy by the alignment device. Therefore, since the predetermined pattern formed on the mask is exposed on the substrate in a state where the mask and the substrate are aligned with high precision, a fine pattern can be accurately formed on the substrate.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an alignment apparatus and an exposure apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of an exposure apparatus according to an embodiment of the present invention. In this embodiment, a case will be described in which the present invention is applied to a step-and-repeat type exposure apparatus including an off-axis type alignment sensor. In the following description, the XYZ rectangular coordinate system shown in FIG. 1 is set, and the positional relationship of each member will be described with reference to the XYZ rectangular coordinate system. In the XYZ orthogonal coordinate system, the X axis and the Z axis are set to be parallel to the paper surface, and the Y axis is set to a direction perpendicular to the paper surface. In the XYZ coordinate system in the figure, the XY plane is actually set to a plane parallel to the horizontal plane,
The Z axis is set vertically upward.

In FIG. 1, when a control signal for instructing emission of exposure light is output from a main control system 11, which will be described later, an illumination optical system 1 emits exposure light EL having substantially uniform illuminance to apply a reticle R. Irradiate. The optical axis AX of the exposure light EL is Z
It is set parallel to the axial direction. The above exposure light EL
Are, for example, g-line (436 nm), i-line (365n)
m), KrF excimer laser (248 nm), ArF excimer laser (193 nm), F ₂ excimer laser (1
93 nm). The reticle R has a fine pattern to be transferred onto a wafer (substrate) W coated with a photoresist, and is held on the reticle holder 2.

The reticle holder 2 is supported so that it can move and minutely rotate in the XY plane on the base 3.
A main control system 11, which controls the operation of the entire apparatus, controls the operation of the reticle stage 3 via the driving device 4 on the base 3, and sets the position of the reticle R. When the exposure light EL is emitted from the illumination optical system 1, the pattern image of the reticle R is projected via the projection optical system PL onto each shot area including the device portion on the wafer W. The projection optical system PL has a plurality of optical elements such as lenses, and the glass material of the optical elements is selected from optical materials such as quartz and fluorite according to the wavelength of the exposure light EL.

The wafer W is mounted on a Z stage 6 via a wafer holder 5. Here, the wafer W placed on the wafer holder 5 will be described. FIG. 2 is a top view illustrating an example of the wafer W. As shown in FIG. 2, on the upper surface of the wafer W, for example, a large number of device regions DP1 to DPn (n is a natural number) in which a semiconductor pattern is formed are denoted by X in the figure.
They are arranged at predetermined intervals in the axial direction and the Y-axis direction. Between each device region DP1~DPn formed street line SL _Y the street line SL _X and the length direction set lengthwise direction in the X-axis direction is set in the Y-axis direction. Device parts DP1 to DP shown in FIG.
n each street alignment marks (not shown) corresponding to the line SL _X, are formed on the SL _Y, the shot area including an alignment mark formed on a single device portion and street lines are formed.
The street lines SL _X and SL _Y are collectively referred to as street lines SL.

FIG. 3 is a diagram showing a configuration of one shot area. 3, device portion DPk (k is a natural number) alignment marks AM1~AM3 for X-axis direction measurement in correspondence with is formed on the street line SL _X, the alignment mark AM4 for Y-axis direction measurement is Street It is formed on the line SL _Y, including a device part DPk and the alignment mark AM1~AM4 one shot area SAk is formed. Here, in a device manufacturing process of a semiconductor integrated circuit or the like, in general, a pattern is repeatedly formed on the device region DPk. However, the illustrated alignment mark AM3 shows the position information of the shot region SAk in the previous process. , And the alignment marks AM1, AM2, AM4 are formed to measure the position information of the shot area SAk in the current process.

In FIG. 3, an alignment mark A called a one-dimensional line and space mark is used.
Although M1 to AM4 are illustrated, an alignment mark AM for two-dimensional measurement that can obtain both the position information in the X-axis direction and the position information in the Y-axis direction in one measurement may be used.

FIG. 4 is a top view showing an example of the configuration of an alignment mark AM for two-dimensional measurement. The alignment mark AM for two-dimensional measurement shown in FIG. 4 measures position information in the X-axis direction in which mark elements am1 whose longitudinal directions are set in the Y-axis direction are arranged at regular intervals in the X-axis direction. And a part for measuring position information in the Y-axis direction, in which mark elements am2 whose longitudinal directions are set in the X-axis direction are arranged at regular intervals in the Y-axis direction. By using the alignment mark AM for two-dimensional measurement, the number of alignment marks formed on the street line SL can be reduced, and the time required for measurement can be reduced.

Returning to FIG. 1, the Z stage 6 is a stage for finely adjusting the position of the wafer W in the Z-axis direction. Also,
The Z stage 6 is mounted on an XY stage 7. X
The Y stage 7 is a stage for moving the wafer W within the XY plane. Although not shown, a stage for slightly rotating the wafer W in the XY plane and a stage for changing the angle with respect to the Z axis to adjust the inclination of the wafer W with respect to the XY plane may be provided. An L-shaped movable mirror 8 is attached to one end of the upper surface of the wafer holder 5.
A laser interferometer 9 is arranged at a position facing the mirror surface of the laser interferometer 9.

Although the illustration is simplified in FIG. 1, the movable mirror 8 is composed of a plane mirror having a mirror surface perpendicular to the X axis and a plane mirror having a mirror surface perpendicular to the Y axis. The laser interferometer 9 has two X-axis laser interferometers that irradiate the movable mirror 8 with a laser beam along the X-axis and a Y-axis laser that irradiates the movable mirror 8 with a laser beam along the Y-axis. , One laser interferometer for the X axis and Y
With one laser interferometer for the axis, the X
The coordinates and the Y coordinate are measured. In addition, the difference between the measured values of the two laser interferometers for the X-axis indicates the XY of the wafer holder 5.
The rotation angle in the plane is measured. Information on the X coordinate, the Y coordinate, and the rotation angle measured by the laser interferometer 9 is supplied to the stage drive system 10. These pieces of information are output from the stage drive system 10 to the main control system 11 as position information. The main control system 11 monitors the supplied position information and performs a positioning operation of the wafer holder 5 via the stage drive system 10. Control. Although not shown in FIG. 1, the reticle holder 2 is also provided with a moving mirror and a laser interferometer provided on the wafer holder 5, and information such as the XYZ position of the reticle holder 2 is mainly controlled. Input to the system 11.

An off-axis alignment sensor 12 is provided beside the projection optical system PL. The alignment sensor 12 is a part of the alignment apparatus according to the embodiment of the present invention provided in the exposure apparatus according to the embodiment of the present invention, and is a FIA (Field Image Alig).
This is an alignment device when applied to the nment) method. The alignment sensor 12 is an alignment sensor 12
The position of the alignment mark AM formed on the wafer W with respect to the focal point is detected, and the position information of the alignment mark AM formed on the wafer W in the XY plane is measured. Irradiation light for illuminating the wafer W from the halogen lamp 13 via the optical fiber 14 is incident on the alignment sensor 12.

Here, the reason why the halogen lamp 13 is used as a light source of the illuminating light is that the wavelength range of the light emitted from the halogen lamp 13 is 500 to 800 nm and that the photoresist applied to the upper surface of the wafer W is not exposed to light. Because
This is because the influence of the wavelength characteristic of the reflectance on the surface of the wafer W can be reduced. The illumination light emitted from the alignment sensor 12 is reflected by the prism mirror 15 and irradiates the upper surface of the wafer W. The alignment sensor 12 takes in the reflected light on the upper surface of the wafer W via the prism mirror 15, converts the detection result into an electric signal, and outputs the electric signal to the alignment signal processing system 16.

The alignment signal processing system 16 determines the alignment mark A for the focal position of the alignment sensor 12 based on the detection result from the alignment sensor 12.
The position shift (defocus amount) of M and the position information of the alignment mark AM in the XY plane are obtained, and these are output to the main control system 11 as wafer position information. The main control system 11 controls the overall operation of the exposure apparatus based on the position information output from the stage drive system 10 and the wafer position information output from the alignment signal processing system 16.

More specifically, the main control system 11 outputs a drive control signal to the stage drive system 10 based on the wafer position information output from the alignment signal processing system 16. The stage drive system 10 drives the XY stage 7 and the Z stage 6 based on the drive control signal. When the stage drive system 10 drives the XY stage 7, the detection result of the alignment sensor 12 is output to the alignment signal processing system 16. From this detection result, for example, a baseline amount that is a deviation amount between the detection center of the position detection sensor and the center of the projected image of the reticle R (the optical axis AX of the projection optical system PL) is measured. Then, the X coordinate and the Y coordinate of the wafer W are controlled based on a value obtained by adding the above-described baseline amount to the position of the alignment mark AM measured by the position detection sensor, thereby accurately setting each shot area. To match the exposure position.

Reference numeral 17 in FIG. 1 denotes, for example, a device portion DPk.
The position of the surface in the Z-axis direction and the position of the wafer W in the Z-axis direction (eg, the position of the street line SL in the Z-axis direction)
This is a storage unit that stores step information indicating a difference between the alignment mark and the alignment mark for each alignment mark. The storage unit 17 stores information obtained by correcting information indicating the position in the Z-axis direction of the surface of the device portion DPk measured by the alignment sensor 12 using the above-described step information, as described in detail later.

In this embodiment, in order to improve the detection accuracy of the position information of the alignment mark AM, control is performed to adjust the surface position of the alignment mark AM formed on the wafer W to the focal position of the alignment sensor 12. For this reason, the alignment sensor 12 uses the alignment mark AM
It can be measured positional deviation in the Z-axis direction of the street line SL _X or street line SL _Y with respect to the focal position of the position information and the alignment sensor 12 in the XY plane. Therefore, first, the main control system 11 moves the XY stage 7 via the stage drive system 10 so that the alignment mark AM to be measured is aligned with the alignment sensor 12.
In the measurement field of view.

In this state, the alignment signal processing system 16
Control system 11 based on wafer position information output from
Calculates the positional shift of the surface of the alignment mark AM with respect to the focal position of the alignment sensor 12 in the Z-axis direction. The control signal is output to the controller. Thereafter, the alignment mark A is set at the focal position of the alignment sensor 12.
The position information of the alignment mark AM in the XY plane is measured with the surface of M arranged. Therefore, by improving the accuracy of the focus position detection of the alignment sensor 12, the alignment mark AM can be focused on the focus of the position detection sensor. As a result, the alignment mark A
The measurement accuracy of the position information in the XY plane of M is improved. The main control system 11 emits the exposure light EL to the illumination optical system 1 after performing control to accurately align the shot area to be exposed with the exposure surface based on the position information of the alignment mark AM in the XY plane. Outputs control signal.

The outline of the configuration and operation of the exposure apparatus according to one embodiment of the present invention has been described above. Next, the alignment sensor 12 included in the alignment apparatus according to one embodiment of the present invention will be described in detail. FIG. 5 is a diagram showing a configuration of the alignment sensor 12 forming a part of the alignment apparatus according to the embodiment of the present invention. As shown in FIG. 5, the alignment sensor 12 has the optical fiber 1
The wavelength range from the halogen lamp 13 in FIG.
Illumination light IL1 of 00 to 800 nm is guided. The illumination light IL1 enters the field stop plate 21 via the condenser lens 20. The field stop plate 21 defines the shape of the image of the illumination light IL1 that irradiates the wafer W.

FIG. 6A is a sectional view showing an example of the field stop plate 21. Field stop plate 2 of the example shown in FIG.
Reference numeral 1 denotes a circular plate-like shape, in which a rectangular opening 21a is formed in the vicinity of the center in the Y-axis direction, and a rectangular opening 21b is provided in the vicinity of the center in the X-axis direction. The field stop plate 21 further has an opening 21c having a substantially square cross section. The opening 21c is provided for irradiating the alignment mark AM. Therefore, the illumination light IL1 incident on the field stop plate 21 is transmitted through the field stop plate 21 to form a rectangular illumination light having a longitudinal direction in the X-axis direction, an illumination light having a longitudinal direction in the Y-axis direction, and It is shaped into illumination light having a substantially square cross section. Hereinafter, reference numeral IL _X illumination light of a rectangular shape having a longitudinal direction in the X-axis direction in the case of distinguishing these illumination light, reference numeral IL _Y illumination light of a rectangular shape having a longitudinal direction in the Y-axis direction subjected, it will be described with further reference numeral IL ₀ to illumination light of the cross-sectional shape of substantially square. Further, the illumination light IL _X , IL _Y , and IL ₀ are not distinguished from each other, and when they are described collectively, the description will be given with reference numeral IL2.

Returning to FIG. 5, the illumination light IL2 is
Is reflected by the beam splitter 23, passes through the objective lens 24, and is emitted from the alignment sensor 12. When the illumination light IL2 is emitted from the alignment sensor 12, it is reflected by the prism mirror 15 and illuminates the alignment mark AM formed on the wafer W and its periphery. FIG. 7 is a diagram for explaining an illumination position of the illumination light IL2 on the wafer W. FIG. 7 illustrates a case where the center of the measurement field of view of the alignment sensor 12 is disposed substantially at the center of the alignment mark AM.

As shown, the alignment sensor 12
With the arrangement of the center alignment marks AM of the measurement field, the illumination light IL _X constituting the illumination light IL2 is disposed on the street line SL, the illumination light IL _Y is device portion DP
k. The position of the illumination light IL _X or illumination light IL _Y are arranged is the focus measuring positions. Since in the example shown in FIG. 7 the illumination light IL _Y are arranged on the device part DPk, device portion by the illumination light IL _Y DPk
Can be measured in the Z-axis direction. on the other hand,
Since the illumination light IL _X are arranged on the street line SL, it is possible to measure the position information in the Z axis direction of the street line SL by the illumination light IL _X. In this embodiment, the position information of the alignment mark AM in the Z-axis direction is obtained based on the position information of the surface of the street line SL in the Z-axis direction.

FIG. 7 omits illustration.
Is the illumination light IL₀Is almost centered on the alignment mark AM
It is arranged at the position where. However, the illumination light IL₀Is the lighting
Light IL_XAnd illumination light IL_YWhat is the focus measurement position where is placed
No overlap, IL_XAnd illumination light IL _YIn a different location than
The size is set so that it is placed. Also, in FIG.
Here, the rectangular area denoted by the symbol FL is the alignment sensor.
Rectangle showing the low-magnification field of view of the camera 12 and denoted by the symbol FH.
The area represents the high magnification field of view of the alignment sensor 12.
You. The example shown in FIG. 7 is an alignment method for measuring in the X-axis direction.
State when measuring the mark AM, that is, the illumination light IL_X
Is placed on the street line SL, but Y
When measuring the alignment mark for axial measurement,
Meiko IL_YIs placed on the street line SL
become.

Referring back to FIG. 5, the wafer W
The area where the mark AM is formed is the lens system 22 and the objective lens.
24 is almost conjugate with the field stop plate 21
(Image relation). Illumination light IL_X,
Illumination light IL_Y, And illumination light IL ₀Reflected light by prism
Returning to the alignment sensor 12 via the mirror 15,
Objective lens 24, beam splitter 23, and lens system
25 in order, and is incident on a beam splitter 26.

The transmitted light out of the reflected light incident on the beam splitter 26 is incident on the light shielding plate 27. FIG. 6B is a diagram illustrating an example of the light shielding plate 27. The light shielding plate 27 is for shielding unnecessary light other than the light used for the focus position detection, and specifically, a rectangular area 27a for shielding incident light.
The wafer W passes through the opening 21c of the field stop plate 21
Illumination light for irradiating, ie for shielding only light reflected by the illumination light IL _0. Light reflected by the illumination light IL _X and illumination light IL _Y transmitted through the light shielding plate 27 is incident on and reflected by the reflecting plate 28 or plate 29.

Here, the illumination light IL transmitted through the light shielding plate 27
The reflected light reflected by _X and illumination light IL _Y is a reflection plate 28, 29 in order to change the traveling direction, since by using a line sensor such as a one-dimensional CCD as a light receiving element as described below It is. That is, in order to measure the reflected light from the wafer W, which is a two-dimensional image, using a line sensor having a one-dimensional light detection surface, an optical system including reflecting plates 28 and 29 is devised. The reflection plate 28 is mainly incident light reflected by the illumination light IL _X, the reflected light is incident due mainly illumination light IL _Y is the reflection plate 29. Reflector 28
And the reflected light of the reflector 29 are respectively reflected by the reflector 3
It is incident on 0,31 and reflected.

The light reflected by the reflector 31 enters the lens system 32. On the other hand, the light reflected by the reflector 30 is reflected by the reflectors 33 and 34, respectively. The reflection plates 33 and 34 are provided with illumination light IL.
Provided in the longitudinal direction of the image of the reflected light by _X in order to parallel to the longitudinal direction of the image of the reflected light by the illumination light IL _Y. The light reflected by the reflector 34 enters the lens system 32. Lens system 3
The light transmitted through 2 enters a pupil division mirror 35 as an optical element that breaks telecentricity. When the light transmitted through the lens system 32 enters the pupil division mirror 35, the light is reflected by the pupil division mirror 35 and its telecentricity is lost. Light in the non-telecentricity through the lens system 36 on the line sensor 37 consisting of one-dimensional CCD or the like, and re-imaging the image of the reflected light by the image and the illumination light IL _Y of the reflected light by the illumination light IL _X . Line sensor 3
Reference numeral 7 captures an image formed on the light receiving surface and performs photoelectric conversion. The photoelectrically converted electric signal is output to alignment signal processing system 16.

As described above, the objective lens 24, the reflection plate 2
8, reflector 30, reflector 33, reflector 34, lens system 3
2. The pupil division mirror 35, the lens system 36, and the line sensor 37 form a part of the first measurement system of the focal position measurement system,
Objective lens 24, reflector 29, reflector 31, lens system 3
2. The pupil division mirror 35, the lens system 36, and the line sensor 37 form a part of a second measurement system of the focal position measurement system.
Both the first measurement system and the second measurement system use the pupil division mirror 35
And is non-telecentric.

Accordingly, when the wafer W is displaced in the Z-axis direction with respect to the focal position of the alignment sensor 12, the position of the image re-formed on the line sensor 37 is shifted in the longitudinal direction of the line sensor 37. Utilizing this, the position of the re-imaged image on the line sensor 37 is stored in advance in the alignment signal processing system 16 as a reference position when the alignment mark AM and the image forming plane of the projection optical system PL coincide with each other. Keep it. Then, the alignment signal processing system 1
At 6, the position shift in the Z-axis direction is detected from the lateral shift amount with respect to the stored reference position.

On the other hand, the light reflected by the beam splitter 26 enters the index plate 38. In the confluent state, the index plate 38 is arranged conjugate with the wafer W with respect to the combined system of the objective lens 24 and the lens system 25, and arranged conjugate with the light receiving surface of the image sensor 40 with respect to the relay lens system 39. The index plate 38 is formed by forming an index mark with a chrome layer or the like on a transparent plate, and a portion where the reflection image of the alignment mark AM passes is kept transparent. The index mark is a position reference in a direction conjugate to the X-axis direction or the Y-axis direction on the wafer W.
Of the reflected light incident on the index plate 38, the light reflected by the illumination light IL _X and illumination light IL _Y is shielded, only light reflected by the illumination light IL ₀ is transmitted through the index plate 38. The index mark is formed on the index plate so as to sandwich the image of the alignment mark AM.

The image of the alignment mark AM transmitted through the index plate 38 and the image of the index mark on the index plate 38 are formed on the light receiving surface of the image sensor 40 via the relay lens system 39. The imaging device 40 is composed of, for example, a two-dimensional CCD, etc.
The reflected image of the alignment mark AM and the projected image of the index mark formed on the light receiving surface are picked up and photoelectrically converted. An image signal obtained by the photoelectric conversion is output to an alignment signal processing system 16, and in the alignment signal processing system 16, position information on the wafer W in the X-axis direction and the Y-axis direction is determined based on the image signal. X and Y coordinates of

Objective lens 24, lens system 25, index plate 3
8, the relay lens system 39, and the image sensor 40 form a part of a position information measurement system. Further, the position information measuring system is a telecentric optical system. Therefore, since the position information measurement system constitutes a telecentric system, when the wafer W is displaced in the Z-axis direction from the focus position of the alignment sensor 12, the position of the image formed on the imaging surface of the imaging device 40 is reduced. The position is defocused without changing. Since the focal positions in the Z-axis direction of the position information measurement system and the focal position measurement system are set to be the same, the position deviation of the wafer W is detected by the focal position measurement system. Then, the Z stage 6 is driven to perform alignment, and the focus position of the focus measurement system is set to the street line SL on the wafer W, so that the focus position of the position information measurement system is also set to the street line SL.

Next, the operation of position detection using the alignment sensor 12 of the exposure apparatus of the present embodiment will be described. FIG. 8 is a flowchart illustrating a flow of a measurement process of the alignment apparatus according to the embodiment of the present invention.
Note that the flow illustrated in FIG. 8 is a flow illustrating a measurement processing procedure when measuring a plurality of alignment marks formed in one shot region among a plurality of shot regions set on the wafer W. When the position information needs to be measured for a plurality of shot areas, the following operation is repeatedly performed. In the following description, the alignment mark A provided in the shot area SAk shown in FIG.
A case where the position information of M1 and AM2 is measured will be described.

When the processing is started, the main control system 11 drives the XY stage 7 via the stage drive system 10, and firstly sets the alignment marks AM1, AM2 and AM4 formed in the shot area SAk. The mark AM1 is moved into the measurement visual field of the alignment sensor 12 (Step S10). This alignment mark A
When M1 is located within the measurement field of view of alignment sensor 12, main control system 11 outputs a control signal to halogen lamp 13 to emit illumination light IL1. Illumination light IL
When the light 1 is emitted, it is introduced into the alignment sensor 12 through the optical fiber 14, passes through the condenser lens 20, is shaped by the field stop plate 21, and is illuminated with the illumination light I.
Illumination light I consisting of L _X , illumination light IL _Y , and illumination light IL ₀
L2. The illumination light IL2 passes through the lens system 22, is reflected by the beam splitter 23, and
Is reflected by the prism mirror 15 and is irradiated onto the wafer W. If the alignment mark AM1 as measurement target is in the position of the alignment mark AM shown in Figure 7, the illumination light IL _X and illumination light IL _Y is disposed in the position shown in FIG.

The illumination light IL _X , the illumination light IL _Y , and the illumination light I
The light reflected by L ₀ returns to the alignment sensor 12 via the prism mirror 15, passes through the objective lens 24, the beam splitter 23, and the lens system 25 in order, and enters the beam splitter 26. Light reflected by the illumination light IL _X is reflected sequentially by the reflecting plate 28,30,33,34 incident on the lens system 32, light reflected by the illumination light IL _Y is reflected sequentially by the reflecting plate 29, 31 a lens system 32
Incident on. The images when entering the lens system 32 have their longitudinal directions parallel to each other. Then, the light is received by the line sensor 37 via the pupil division mirror 35 in a state where its telecentricity is broken. These images are formed on the light receiving surface of the line sensor in a state where the images are laterally shifted according to the position of the alignment mark AM in the Z-axis direction.

The photoelectric conversion by the line sensor 37 is performed.
The electric signal is input to the alignment signal processing system 16 and transmitted.
No. processing is performed. At this time, the alignment signal processing system
16 is illumination light IL_XStreet la detected by
Information indicating the position (height position) of the in-SL in the Z-axis direction;
Illumination light IL_YOf the device part DPk detected by
Measures information indicating the position (height position) in the Z-axis direction
(Step S12). The alignment signal processing system 16
These are output to the main control system 11. The main control system 11
Alignment based on information indicating the force height position
The height position of the mark AM1 and the focus detection position (AF detection position)
Step information, which is the difference from the height position in
It is determined by the method described (step S14). First,
When the measurement (AF measurement) in step S12 is completed,
The illumination mark AM1 is the illumination light IL. _XIlluminated by
The XY stage 7 is moved so that the
Then, the XY stage 7 is moved in the -X direction), and the illumination light I
L_XHeight information of the alignment mark AM1
Is measured. Then, on this alignment mark AM1
AF measurement result and the stream obtained in step S12
The difference from the AF measurement result on the line SL is calculated. This
Is the step information in the alignment mark AM1.
You. In step S14, as described later, the same
Other alignments in the shot to be measured (sample shot)
The same measurement was performed for the ment marks AM2 and AM4.
U. Thus, in one sample shot
For each alignment mark AM1, AM2, AM4
Step information for the corresponding step is calculated.

In step S14, the step information is obtained based only on the actual measurement result. In addition, for example, the step information is obtained based on the design value information such as the alignment mark stored in the main control system 11 in advance. It is also possible to calculate information. More specifically, since the information indicating the height of the alignment mark AM formed on the street line from the surface of the street line is stored in advance in the main control system 11 as design value information, for example, FIG.
In the step information on the alignment mark AMb (the difference in surface height between the alignment mark AMb and the AF detection position AFb) shown in FIG. 3C, the previously stored design value information becomes the step information on the alignment mark AMb as it is. . Note that the step information in the alignment mark AMa in FIG. 13C can also be calculated based on the design value. The main control system 11 also stores height position information (height position information from the street line of the alignment mark AMa ') on the design value of the AF detection position AFa. A difference between the height position and the designed height position of the mark AMa is obtained, and this is step information on the alignment mark AMa. As described above, in step S14, the step information of each alignment mark AM may be obtained based on the design value.
The above-described design value information is input by the user using the input device 50 such as the keyboard shown in FIG. 1, and the input information (design value and the like) is displayed on the display device 60 such as a monitor. Will be displayed. Therefore, the user can check on the monitor 60 various information that has been set (height information from the street line of the alignment mark, step information, and the like). Further, the display device 60 is connected to the input device 50.
In addition to the information (design value) input in step (2), the calculated value calculated based on the design value (step information calculated by the above-described calculation method) may be displayed. Alternatively, a measured value (such as the AF measurement result described above in step S14) may be displayed. It is also conceivable to relatively display such measured values (actual measured values) and design values (input values). Further, on the monitor 60, instead of simply displaying a numerical value (a numerical value indicating a height), a numerical value (height information) is added to a cross-sectional view as shown in FIG. And then
The cross-sectional structure of the wafer may be displayed in various display forms that facilitate visual recognition. The input information is also transmitted to the main control system 11, so that the main control system 11
It is also possible to perform various controls (for example, control of the exposure amount) based on the input information.

Next, the main control system 11 is connected to the street line S
By subtracting the above-mentioned (determined in step S14) level information from (AF information obtained by the illumination light IL _X) information indicating the position of the Z-axis direction L, indicating the position in the Z-axis direction of the street line SL The information is corrected (Step S16). Next, the main control system 11 stores the information corrected in step S16 as focal position information in the storage unit 17 (step S18).

Next, based on the focal position information stored in the storage unit 17, the Z stage 6 is driven to move the wafer W in the Z-axis direction, so that the focal position of the alignment sensor 12 is shifted to the surface of the alignment mark AM1. The position is arranged (step S20). In this process, the same effect as the movement of the Z stage 6 may be obtained by changing the magnification of the optical system inside the alignment sensor 12 without driving the Z stage 6.

When the surface position of the alignment mark AM 1 is arranged at the focal position of the alignment sensor 12, the position information measuring system including the objective lens 24, the lens system 25, the index plate 38, the relay lens system 39, and the image sensor 40 can be used. The alignment signal processing system 16 performs various image processing on the output detection signal to perform alignment mark AM.
1 is measured in the XY plane (step S
22). This position information is output from the alignment signal processing system 16 to the main control system 11, and is stored together with the step information and the focal position information described above (step S24). When the above processing is completed, the main control system 11 sets the shot area SA
It is determined whether or not there is still an alignment mark to be measured in k (in the sample shot area) (step S2).
6).

If there is an unmeasured alignment mark in the sample shot (in the example shown in FIG. 3, there are alignment marks AM2 and AM4 which have not been measured yet), the flow returns to step S10 to repeat the above processing. . In this series of processing, in step S14, step information in each of the alignment marks AM2 and AM4 is obtained by the method described above and stored in the storage unit 17. On the other hand, if there is no unmeasured mark in step S26, the process proceeds to step S28. In step S28, it is determined whether or not unmeasured sample shots still remain on the same wafer. If there is an unmeasured sample shot, the process proceeds to step S30. If there is no unmeasured sample shot, the process of this flow ends. Step S30
Then, the position information of a plurality of alignment marks in the next sample shot is measured. Here, the focus alignment (AF) of the plurality of alignment marks is performed by aligning the alignment marks AM1, AM2, and AM4 of the previous sample shots corresponding to the respective alignment marks.
Is performed by using the step information (calculated in step S14). That is, the AF of the mark AM of the present sample shot corresponding to the arrangement of the mark AM1 of the previous shot is:
This is performed based on the result of correcting the AF result of the mark AM based on the step information of the mark AM1. As described above, while performing the AF based on the step information obtained in the previous sample shot, each alignment mark in a plurality of sample shots is obtained.
When the measurement of the marks is completed and the measurement of all the marks to be measured in all the sample shots is completed, the processing of this flow ends.

By the processing described above, the position information of the alignment mark AM is measured with high accuracy. The main control system 11 performs correction by adding the above-described base line amount to the detected X coordinate and Y coordinate of the alignment mark AM having high accuracy. Then, the main control system 11 makes the center of each shot area coincide with the optical axis AX of the projection optical system PL based on the X- and Y-coordinates of the wafer W corrected by the baseline via the stage drive system 10. Then, the XY stage 7 is driven. Alignment mark AM
Is measured with high accuracy, the position information of each shot area is also obtained with high accuracy, and as a result, alignment of each shot area of the wafer W with an accurate exposure position, that is, accurate alignment of the wafer W, is performed. It can be carried out.

In the recent alignment measurement, from the viewpoint of improving the throughput, the position information is not measured for all the shot regions, but the position information of only the shot region selected in advance is measured, and the measurement result is obtained. A so-called enhanced global alignment method is used in which the statistical information is used to measure the position information of all shot areas. The same pattern is formed in each of the above-described shot areas SA1 to SAn. Therefore, when measuring the position information of the selected sample shot area, the step information and the focus information obtained by performing the measurement on the focal position only for a plurality of alignment marks formed in the sample shot area to be measured first. The storage unit 17 stores the position information together with the position information in the XY plane. In the above-described embodiment (FIG. 8), for the remaining sample shot areas, the surface position of the alignment mark AM to be measured is set to the focal position of the alignment sensor 12 based on the focal position information stored in the storage unit 17. Then, the position information in the XY plane is measured. This makes it possible to omit the process of obtaining the focal position information, which can contribute to an improvement in throughput. In the first two or three shots of the sample shots, step information is obtained for each mark, and the step information for each shot is averaged for each mark corresponding to the layout.
The averaged step information for each mark may be used in the remaining sample shots.

Generally, the wafers W are processed in lot units each of which includes a plurality of wafers. In this case, of the plurality of shot areas formed on the wafer W to be measured first,
The focus position information on the alignment marks formed in the preselected sample shot area is stored in the storage unit 17, and when the subsequent measurement of the wafer W is performed, the storage unit 1
The position of the alignment mark AM to be measured is adjusted to the focal position of the alignment sensor 12 based on the focal position information (step information or the like) stored in the memory 7 to measure the positional information in the XY plane, thereby improving the throughput. It is preferable from a viewpoint. If there is variation in the flatness of the surface between the wafers W, the measurement result of the focal position information (step information etc.) for each mark formed on each of the plurality of wafers W measured from the head of the lot Is stored in the storage unit 17 as the focal position information of each alignment mark. For the remaining wafer W, the alignment mark AM to be measured is determined based on the focal position information stored in the storage unit 17. It is preferable to measure the position information in the XY plane by adjusting the surface position to the focal position of the alignment sensor 12. In the above embodiment, the case where the AF detection position is set on the street line SL is described. However, the present invention is also applicable to a method in which the AF detection position is set to the device portion DPk. In this case, the AF position information obtained on the street line SL in the above embodiment of the present application may be replaced with AF information obtained by illuminating the device portion DPk.

In the above embodiment, the illumination light IL
_Although the shape of _X and IL _Y is rectangular, the present invention is not limited to this shape, and can be appropriately changed according to the detection target. When the street line SL is formed on the wafer W without being orthogonal, the optical system or the field stop plates 21 and 5 are aligned with the street line SL.
1 may be changed to illuminate the street line SL.

The exposure apparatus (FIG. 1) according to one embodiment of the present invention can accurately control the position of the wafer W at high speed, and can perform exposure with high exposure accuracy while improving throughput. As described above, a reticle alignment system including the illumination optical system 1, the reticle holder 2, the base 3, and the driving device 4, a wafer alignment system including the wafer holder 5, the Z stage 6, the XY stage 7, the movable mirror 8, and the laser interferometer 9. After the components shown in FIG. 1 such as the projection optical system PL are electrically, mechanically or optically connected and assembled, they are manufactured by performing comprehensive adjustment (electrical adjustment, operation confirmation, etc.). You. It is desirable that the manufacture of the exposure apparatus be performed in a clean room in which the temperature, cleanliness, and the like are controlled.

Next, the manufacture of a device using the exposure apparatus and the exposure method according to one embodiment of the present invention will be described.
FIG. 9 shows a device (a semiconductor chip such as an IC or an LSI, a liquid crystal panel,
3 is a flowchart of production of a CCD, a thin-film magnetic head, a micromachine, and the like. First, as shown in FIG.
In step S30 (design step), a function design of a device (for example, a circuit design of a semiconductor device) is performed, and a pattern design for realizing the function is performed. Subsequently, in step S31 (mask manufacturing step), a mask on which the designed circuit pattern is formed is manufactured. On the other hand, in step S32 (wafer manufacturing step), a wafer is manufactured using a material such as silicon.

Next, in step S33 (wafer process step), an actual circuit or the like is formed on the wafer by lithography using the mask and the wafer prepared in steps S30 to S32. Then
In step S34 (assembly step), step S
The wafer is processed into chips by using the wafer 33.
Step S34 includes processes such as an assembly process (dicing and bonding) and a packaging process (chip encapsulation). Finally, in step S35 (inspection step), inspections such as an operation confirmation test and a durability test of the device manufactured in step S35 are performed. After these steps, the device is completed and shipped.

The exposure apparatus of the present embodiment can be applied to a scanning type exposure apparatus (US Pat. No. 5,473,410) for exposing a mask pattern by synchronously moving a mask and a substrate. Further, the exposure apparatus of the present embodiment can be applied to a proximity exposure apparatus that exposes a mask pattern by bringing a mask and a substrate into close contact without using a projection optical system. Further, the application of the exposure apparatus is not limited to an exposure apparatus for manufacturing a semiconductor. For example, an exposure apparatus for a liquid crystal that exposes a liquid crystal display element pattern to a square glass plate, or a thin film magnetic head is manufactured. Widely applicable to the exposure apparatus. The light source of the exposure apparatus of the present embodiment includes g-line (436 nm), i-line (365 nm), Kr
Not only an F excimer laser (248 nm), an ArF excimer laser (193 nm), and an F ₂ laser (157 nm) but also a charged particle beam such as an X-ray or an electron beam can be used. For example, when an electron beam is used, a thermionic emission type lanthanum hexaborite (LaB ₆ ) or tantalum (Ta) can be used as an electron gun.

The magnification of the projection optical system may be not only the reduction system but also any one of the same magnification and the enlargement system. As the projection optical system,
When far ultraviolet rays such as an excimer laser are used, a material that transmits far ultraviolet rays such as quartz or fluorite is used as the glass material.
_{(2) When a} laser or X-ray is used, a catadioptric or refractive optical system is used (a reticle is also of a reflection type). When an electron beam is used, the optical system includes an electron lens and a deflector. An electron optical system may be used. It goes without saying that the optical path through which the electron beam passes is in a vacuum state.

When a linear motor (see US Pat. No. 5,623,853 or US Pat. No. 5,528,118) is used for the wafer stage or reticle stage, either an air levitation type using an air bearing or a magnetic levitation type using Lorentz force or reactance force is used. May be used. The stage may be of a type that moves along a guide or a guideless type that does not have a guide. As the stage driving device, a planar motor that drives a stage by electromagnetic force with a magnet unit having two-dimensionally arranged magnets and an armature unit having two-dimensionally arranged coils opposed to each other may be used. In this case, one of the magnet unit and the armature unit may be connected to the stage, and the other of the magnet unit and the armature unit may be provided on the moving surface side of the stage.

The reaction force generated by the movement of the wafer stage is disclosed in JP-A-8-166475 (US Pat. Nos. 5,528,118).
As described in the above, a frame member may be used to mechanically escape to the floor (ground). The reaction force generated by the movement of the reticle stage is mechanically released to the floor (ground) by using a frame member as described in JP-A-8-330224 (US S / N 08 / 416,558). Is also good.

[0070]

As described above, according to the alignment apparatus according to the aspect of the present invention, step information in the vertical direction between the surface of the object at the focus measurement position and the surface of the mark is stored for each mark. Therefore, when the focus measurement position for measuring the focus position information in the vertical direction of the object is set to a position different from the mark formation position, and when the surface position of the object changes according to the focus measurement position However, there is an effect that the position of each mark surface can be obtained based on the step information. Also,
According to the alignment device of the second aspect of the present invention,
The position of the object in the vertical direction is controlled based on the step information stored in the storage means and the measured focal position information. As a result, the focus position of the alignment device can be adjusted to the mark surface, and the accuracy of measuring the position information of each mark in a two-dimensional plane can be improved. In addition, according to the alignment apparatus of the third aspect of the present invention, so-called multi-point intra-shot alignment measurement for measuring a plurality of marks formed in the shot area and correcting a positional shift for each shot area in a two-dimensional plane. When performing, even when the surface of the object at the focus measurement position is changing for each mark, the surface of each mark can be adjusted to the focus position of the alignment device, and the accuracy of the mark Position information in a two-dimensional plane can be measured. As a result, there is an effect that the displacement of each shot area in the two-dimensional plane can be corrected with high accuracy. According to the alignment apparatus of the eighth aspect of the present invention, the focus position of the mark related to the shot area to be measured first is stored. Therefore, for the remaining shot areas, the process of obtaining the focal position information by adjusting the vertical position of the substrate based on the stored focal position information and measuring the positional information in the two-dimensional plane can be omitted. There is an effect that position information in each two-dimensional plane can be measured with high throughput. In addition, the ninth aspect of the present invention
According to the alignment apparatus according to the aspect of the present invention, the focus position information of the mark formed on the substrate to be measured first is stored in the storage means. Therefore, for the remaining substrates, the process of obtaining the focal position information by adjusting the vertical position of the substrate based on the stored focal position information and measuring the positional information in the two-dimensional plane can be omitted. There is an effect that position information in a two-dimensional plane can be measured with high throughput. According to the alignment apparatus of the tenth aspect of the present invention, focus position information for each mark is measured for a plurality of substrates from the beginning of the lot, and the average value of the measurement results is stored for each mark. . Therefore, even when the surface flatness varies between the substrates, the vertical position of the substrate is adjusted based on the average value stored for the remaining substrates, and the positional information in the two-dimensional plane is measured. Thus, there is an effect that position information for each mark can be measured with high throughput. Also,
According to the alignment apparatus of the eleventh aspect of the present invention, the position of the substrate in the vertical direction is controlled based on the corrected focal position information. As a result, the focus position of the alignment device can be adjusted to the mark surface,
There is an effect that the accuracy of measuring the position information of each mark in the two-dimensional plane can be improved. Also,
According to the exposure apparatus of the present invention, the alignment between the mask and the substrate is performed based on the position information measured with high accuracy by the alignment apparatus. Therefore, since the predetermined pattern formed on the mask is exposed on the substrate in a state where the mask and the substrate are aligned with high precision, there is an effect that a fine pattern can be accurately formed on the substrate. .

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an exposure apparatus according to an embodiment of the present invention.

FIG. 2 is a top view illustrating an example of a wafer W.

FIG. 3 is a diagram showing a configuration of one shot area.

FIG. 4 is a top view illustrating a configuration of an example of an alignment mark AM for two-dimensional measurement.

FIG. 5 is a diagram showing a configuration of an alignment sensor 12 forming a part of an alignment apparatus according to an embodiment of the present invention.

FIG. 6 is a diagram showing an example of a field stop plate 21 and an example of a light shielding plate 27.

FIG. 7 is a diagram for explaining an irradiation position of illumination light IL2 on a wafer W.

FIG. 8 is a flowchart illustrating a flow of a measurement process of the alignment apparatus according to the embodiment of the present invention.

FIG. 9 is a flowchart when a device is manufactured using the exposure apparatus according to the embodiment of the present invention.

FIG. 10 is a diagram showing a configuration of a conventional alignment sensor.

FIG. 11 shows an example of a field division stop 103 and a light shielding plate 11.
FIG. 3 is a diagram showing an example of No. 3;

FIG. 12 is a diagram for explaining an illumination area on a wafer W of a conventional alignment sensor 100.

FIG. 13 is a diagram for explaining a problem that occurs when measuring position information using a conventional alignment sensor when a position where an alignment mark is formed and a focus detection position are set to different positions.

[Explanation of symbols]

6 Z stage (movement control means, vertical movement control means) 10 Stage drive system (movement control means, vertical movement control means) 11 Main control system (movement control means, vertical movement control means) 17 Storage unit (storage means, correction focus) Position storage means) 24 Objective lens (position information measurement system,
(Focal position measuring system) 25 Lens system (Position information measuring system) 28 Reflector (focal position measuring system) 29 Reflector (focal position measuring system) 30 Reflector (focal position measuring system) 31 Reflector (focal position measuring system) 32 Lens system (focal position measuring system) 33 Reflector (focal position measuring system) 34 Reflector (focal position measuring system) 35 Pupil split mirror (focal position measuring system) 36 Lens system (focal position measuring system) 37 Line sensor ( Focus position measurement system) 38 Index plate (position information measurement system) 39 Relay lens system (position information measurement system) 40 Image sensor (position information measurement system) AM, AM1, AM2 Alignment mark (mark) IL _X illumination light (first) detection light) IL _Y illumination light (second detection light) R reticle (mask) SA1 to SAn shot area SL, SL _X, SL _Y street line W wafer (object, substrate)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/30 525W F-term (Reference) 2F065 AA02 AA03 AA06 AA07 AA14 BB02 CC17 CC20 DD03 FF01 FF04 GG03 JJ25 LL02 LL04 LL12 LL30 LL67 MM03 MM04 QQ13 QQ23 QQ31 5F046 DA14 DB05 DB10 EB01 FB17 FC04

Claims (12)

[Claims] 1. A position information measurement system for measuring position information of a plurality of marks formed on an object in a predetermined two-dimensional plane, and a position information measurement system set at a position on the object different from the mark formation position. A focus position measurement system that measures focus position information in a direction perpendicular to the two-dimensional plane of the object at the focus measurement position, comprising: an object surface and the mark surface at the focus measurement position. Storage means for storing step information in the vertical direction between the marks for each mark. 2. The object when measuring position information of the mark by the position information measurement system based on the focus position information measured by the focus position measurement system and the step information at the focus measurement position. 2. The alignment apparatus according to claim 1, further comprising a movement control means for controlling the position in the vertical direction. 3. The object according to claim 1, wherein the object is a substrate on which a plurality of shot areas are formed, and the plurality of marks are formed on each of the shot areas. Alignment device. 4. The alignment apparatus according to claim 3, wherein the mark and the focus measurement position are set at different positions on a street line provided between the shot areas. 5. The street line is provided in a first direction and a second direction, and the focus position measurement system irradiates a first detection light whose longitudinal direction is set to the first direction. The alignment apparatus according to claim 4, further comprising: a second measurement system configured to irradiate a second detection light set in the second direction. 6. The focus position measuring system compares the intensity of the reflected light of the first detection light with the intensity of the reflected light of the second detection light, and according to the comparison result, the first measurement system or the Second
6. The alignment apparatus according to claim 5, wherein one of the measurement systems is selected to perform focus detection. 7. A correction focus position storage means for storing focus position information for the mark obtained by correcting the focus position information measured by the focus position measurement system using the step information. The alignment device according to any one of claims 3 to 6. 8. The alignment apparatus according to claim 7, wherein said corrected focal position storage means stores focal position information of a mark relating to a shot area to be measured first among said shot areas. 9. The method according to claim 1, wherein the substrate is provided in lot units each including a plurality of substrates, and the corrected focal position storage unit stores focal position information of a mark formed on a substrate to be measured first. The alignment apparatus according to claim 7, wherein: 10. The correction focus position storage means stores, for each mark, an average value of measurement results of focus position information for each corresponding mark formed on a plurality of substrates measured from the beginning of the lot. The alignment apparatus according to claim 7, wherein the alignment is stored. 11. A vertical movement control means for moving the substrate in the vertical direction based on the focus position information stored in the corrected focus position storage means, wherein the position information measurement system is provided by the vertical movement control means. The alignment apparatus according to any one of claims 7 to 10, wherein position information of the mark in the two-dimensional plane is measured after the movement of the substrate. 12. An exposure apparatus for exposing a predetermined pattern formed on a mask onto a substrate, comprising: the alignment apparatus according to claim 1; An exposure apparatus for performing relative positioning between the mask and the substrate on the basis of the pattern and exposing an image of a predetermined pattern formed on the mask onto the substrate.