JPH04348019A - Focus position detecting device - Google Patents

Abstract

PURPOSE:To easily determine a focus respectively and to improve its reliability by detecting reflection light of a projection image of an aperture pattern formed in a mask pattern surface by a projection optical system through the projection optical system and the aperture pattern and by detecting change of light amount of the projection image passed through the aperture pattern. CONSTITUTION:A mask 3 with a mask pattern in a lower side is opposite to a stage 12 through a projection optical system 2 and is illuminated by an exposure illumination system 4 during projection exposure. A reference surface on a stage 12 wherein an aperture pattern 1a of a specified shape and illumination light of the aperture pattern 1a are introduced. Reflection light of a projection image of the aperture pattern 1a formed in a master pattern surface by the projection optical system 2 under the illumination light is detected through the projection optical system 2 and the aperture pattern 1a. Then, change of light amount of the projection image passed through the aperture pattern 1a again is detected by a detector 7. A position wherein maximum or minimum change of light amount of the projection image is a focus.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is applicable to a so-called autofocus mechanism, which automatically corrects the focus of a mask pattern and a wafer in a semiconductor projection exposure apparatus. This invention relates to a detection device.

0002

[Prior Art] Projection exposure technology involves arranging a mask pattern and a stage with a projection optical system in between, and transferring the mask pattern onto a sample on the stage using exposure light such as ultraviolet light.
BACKGROUND ART Projection exposure apparatuses have been put to practical use in various precision processing fields including the manufacture of semiconductor devices, and a wide variety of projection exposure apparatuses are on sale according to their respective uses in each field. In these projection exposure devices, it is possible to align the exposed surface of the sample with the conjugate position (height) of the mask pattern with respect to the projection optical system under actual exposure light, that is, to focus the mask pattern on the exposed surface. This is an important requirement. Therefore, a projection exposure apparatus for normal production purposes is equipped with a focusing mechanism that automatically performs this focusing, a so-called autofocus mechanism, in order to achieve both efficiency and reliability of projection exposure.

[0003] As such a focusing mechanism, for example, as shown in Japanese Patent Laid-Open No. 57-212406, a special mark formed on the mask pattern surface is projected directly onto the exposure surface of the sample, and the There have also been reports of a method in which the projected image is detected via a projection optical system and a mark to directly determine the focused point, but in general, A combination of a means for directly detecting the focal point of the image plane using exposure light, and a means for measuring the height on the stage side under the projection optical system, using the means to adjust the origin to the height of the focal point. , a method is adopted in which the height of the exposure surface is indirectly detected using the measuring means and guided to the focal point height. Here, as a means for using the exposure light (2), for example, Japanese Patent Laid-Open No. 1-286418 discloses a method of projecting special marks formed on a mask pattern surface onto a reference surface. In this method, the projected image of the mark formed on the reference plane is observed through the projection optical system and the mark, and the peak of the light intensity of the projected image focused by the mark is detected to determine the focused point. is determined. In addition, as an example of means for measuring the height on the stage side in (2), for example, Japanese Patent Application Laid-Open No. 1-41962 discloses that an optical system fixed obliquely to the outside of the projection optical system is used to expose the area directly below the projection optical system. A method for measuring the height of a surface is shown.

0004

[Problems to be Solved by the Invention] Currently, in the case of semiconductor memory devices with particularly high processing precision,
Projection with a depth of focus of about 1 μm is performed using a line, and the positioning accuracy of the focal point is usually less than 0.1 μm.Special projection using the interference phenomenon of exposure light shown in Japanese Patent Publication No. 62-50811 0.05μm for exposure
The following extremely high precision is required. In order to achieve such high accuracy, minute deflections and inclinations of the mask itself cannot be ignored anymore, and the in-focus point of a mark placed in one corner of the mask pattern must be detected to match the in-focus point of the entire mask pattern. Conventional methods such as There is. Therefore, a method has been devised in which the height of the focal point is determined individually for each portion within the transfer area of the mask pattern, and the variation in the height is absorbed to the maximum extent by tilting the stage.

[0005] In this method, the height of the focal point is naturally determined individually for each part of the actual mask pattern immediately before exposure transfer, but this is difficult to do by directly determining the focal point using conventional exposure light. It is not possible to implement the detection method. For example, in order to implement the method disclosed in Japanese Unexamined Patent Application Publication No. 1-286418, it is necessary to place marks for in-focus point detection in each part of the transfer area of the mask pattern.
This is unrealistic because it adversely affects the degree of integration of the mask pattern.

[0006] Furthermore, in the methods disclosed in Japanese Unexamined Patent Publications Nos. 57-212406 and 1-286418, the optical information from the projected image of the exposed surface is partially traced back along the optical path of the exposure light to the detector. Therefore, the reflected light of the exposure light in the optical path portion, for example, the exposure light reflected from each lens surface of the projection optical system, the back surface of the mask pattern, and both surfaces of the mask, is turned back and reaches the detector as it is. The detector needs to detect the peak of optical information from the projected image by subtracting a huge background caused by the reflected light of the exposure light. Therefore, ■the area of the mark that occupies the illumination field of the exposure light (mask pattern) is small, and ■the light-shielding area that occupies the mask pattern is large (the amount of reflection on the back surface of the mask pattern is large).
,■The output of the light source fluctuates and the intensity of the exposure light changes moment by moment.
In such a case, peak detection becomes difficult, and there is a possibility that the in-focus point determination may not function properly.

[0007]

[Means for Solving the Problems] The present invention makes it easy to individually determine the focal point height for each part of the actual mask pattern immediately before exposure transfer, and it is possible to create a special mark within the transfer area of the mask pattern. - To provide a focus position detection device that does not require the placement of a mask and can determine the focused point with high reliability even when the light-shielding area occupied by the mask pattern is large or when the exposure light intensity changes moment by moment. The purpose is

The focus position detection device according to claim 1 of the present invention is a focus position detection device for detecting a stage-side conjugate position of a mask pattern surface with respect to a projection optical system. A reference surface formed on the stage, an illumination means for guiding illumination light to the aperture pattern, and a projected image of the aperture pattern formed on the mask pattern surface by a projection optical system under the illumination light. and detecting means for detecting the reflected light through the projection optical system and the aperture pattern again, and detecting a change in the amount of light of the projected image that has passed through the aperture pattern.

The focus position detection device according to claim 2 of the present invention is the focus position detection device according to claim 1, in which the focus position detection device according to claim 1 is configured such that the focus position detection device according to claim 1 moves up to a position where the maximum or minimum of the light amount change is obtained based on the output of the detection means. The apparatus includes a position adjusting means for moving the stage, and a measuring means for measuring the direction of positional deviation at an arbitrary location on the stage with reference to the position of the reference plane at the position.

The focus position detection device according to claim 3 of the present invention is the focus position detection device according to claim 2, wherein
The measurement device comprises a scanning mechanism that scans an arbitrary location on the stage under the field of view of the projection optical system, and a measuring device that measures the position on the stage side with respect to the projection optical system using an optical path fixed to the projection optical system. It is something that has the means.

The focus position detection device according to claim 4 of the present invention is the focus position detection device according to any one of claims 1 to 3, in which a plurality of parallel The opening pattern is formed in a linear or checkered pattern.

0012

[Operation] The focal position detection device according to claim 1 of the present invention has the following features:
The aperture pattern formed on the reference surface on the stage is projected onto the mask pattern surface through a projection optical system in the opposite direction to the exposure light, and the reflected image of the projected image from the mask pattern surface is regenerated. The in-focus position is determined by passing through the pattern and detecting changes in the amount of light. In other words, the mask pattern surface is regarded as a projection surface and a projected image of the aperture pattern is formed by the projection optical system, so that the blur of the projected image is minimized and the aperture pattern maximizes the optical information from the projected image. Find the position (height) of the reference plane that can be captured. At this time, if you close the shutter of the exposure light source so that the exposure light does not directly enter the aperture pattern so that the mask pattern surface is not illuminated by the exposure light, the background light for detecting changes in light intensity will be reduced. It's convenient because it's smaller. Also, the opening pattern
The illumination light guided to the pattern may be branched from an exposure light source and guided to the aperture pattern, or a dedicated light source whose output wavelength is approximately the same as that of the exposure light may be provided.

Here, as means for guiding the illumination light to the aperture pattern, a combination of mirrors or a glass fiber bundle can be employed, but the optical information from the projected image is only a part of the optical path of the illumination light. Since the illumination light traces back to reach the detection means, unnecessary reflected light of the illumination light from that part also reaches the detection means and becomes a background when detecting a change in light amount, and becomes an obstacle to detecting a change in light amount of a projected image. However, the degree of damage is much smaller than in the conventional case where the entire mask pattern surface is exposed to exposure light because the illuminated area is smaller. Therefore, in order to more reliably detect changes in the amount of light in a projected image, it is necessary to (1) reduce the reflection rate of illumination light at the relevant portion by devising the surface treatment of the optical element and the arrangement of the optical path; It would be convenient to take measures to prevent this from reaching . By combining these measures,
Even if the area of the aperture pattern is small, the detection background can be kept small and peak detection can be performed with high reliability.

On the other hand, the stage is equipped with a mechanism that can move any location on the stage directly below the projection optical system, and scans the stage within the field of view of the projection optical system to form a mask pattern. The projected image of the aperture pattern can be moved to any location on the screen. This makes it possible to detect the position (height) of the focal point at many locations on the mask pattern, and to know the most convenient position and orientation of the exposure surface of the sample with respect to the entire mask pattern.

The focal position detection device according to claim 2 of the present invention includes: (1) means for directly determining the conjugate plane of the mask pattern with respect to the projection optical system on the reference plane on the stage using illumination light; (2) A means for measuring the position (height) of the exposed surface whose origin has been corrected by the means, and the scale adjustment of the measuring means ( The measuring means determines the positional deviation direction (positive or negative) at any location on the stage compared to the origin.

The focal position detection device according to claim 3 of the present invention uses a combination of an optical measuring device fixed to a projection optical system and a stage scanning mechanism to detect a focal point at any location on the stage. This is to make a determination. The optical measuring device is, for example, composed of a combination of a light projector and a photosensor array in which an optical path is arranged with a reflection point set approximately in the center of the field of view of the projection optical system, and the projection optical system is connected to the position of the reflected light spot on the array. Measure the position (height) directly below.

The focal position detection device according to claim 4 of the present invention is such that the mask pattern interacts with the projected image of the aperture pattern on the mask pattern plane, which has been described as a uniform projection plane. This takes into consideration the possibility that the detection of the maximum or minimum of the change in light intensity may be hindered. In other words, since the local reflectance of the mask pattern surface differs depending on the presence or absence of the mask pattern, if the projected image of the aperture pattern exactly overlaps the mask pattern, the position where the maximum or minimum change in light intensity is obtained is no longer necessarily the focal point. Therefore, it is necessary to select the shape of the aperture pattern so that the reflected light of the projected image does not exactly overlap the mask pattern. Mask patterns for semiconductor integrated circuits are usually composed of a large number of horizontal and vertical parallel lines and a small number of diagonal lines at specific angles. It is convenient to form them in parallel lines. Here, the reason why the parallel line shape is selected is that the amount of light changes sharply depending on the focal point. Furthermore, the parallel lines are made orthogonal to avoid the influence of astigmatism of the projection optical system. A similar effect can also be obtained by using a checkered grid.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram of an automatic focusing device according to an embodiment of the present invention. This is an automatic focusing device installed in a projection exposure system for semiconductor integrated circuits. Prior to projection exposure, this device detects the height of the conjugate plane over the entire mask pattern and places the mask on an XY stage. The height and inclination of the exposed surface on the placed wafer are adjusted so that the exposed surface coincides with the conjugate plane.

In FIG. 1, a mask 3 having a mask pattern on its lower surface faces a stage 12 through a projection lens 2, and is illuminated by an exposure illumination system 4 during projection exposure. The stage 12 on which the wafer 11 is placed can be moved to any position on the stage 12 directly below the projection optical system 2 by an XY drive system 15, and can be moved directly below the projection optical system 2 by a Zθ drive system 9.
The entire table 12 can be adjusted to any desired height and inclination. A fiducial surface 1 having a predetermined aperture pattern 1a is provided on the stage 12, and the aperture pattern 1a includes an illumination light source 8, a glass fiber cable 13, etc. The optical system is connected to a detection optical system including a glass fiber cable 13, a light amount detector 7, a half mirror 14, and the like. Input focus sensors 5 and 6 for detecting the wafer surface are fixed to the projection optical system 2. The outputs of the sensor 6 and the detector 7 are input to a control system 10, and the drive system 9 is controlled by the control system 10.

In the automatic focusing device configured as described above, the illumination light output from the illumination light source 8 is connected to the cable 1.
3, the aperture pattern 1a is emitted upward, and the aperture pattern is formed on the mask pattern surface via the projection optical system 2.
A projected image of the tube 1a is formed. The projected image can be moved to any location on the mask pattern by scanning the fiducial surface 1 within the field of view of the projection optical system 2 using the drive system 15, and can be individually projected at each location. The in-focus point can be determined.

Further, the optical information from the projected image of the mask pattern surface travels back along the optical path of the illumination light and forms an image on the conjugate surface of the mask pattern with respect to the projection optical system 2. At this time, if the height of the reference plane is in a conjugate positional relationship with respect to the mask pattern surface and the projection optical system 2, the projected image of the mask pattern surface will have a clear focused boundary, and the reflection of the projected image will be The second projected image of the light on the reference surface also reveals the in-focus boundary. Here, the second projected image is
Naturally, since it has the same shape, size, and attitude as the aperture pattern 1a, the maximum amount of light information from the projected image of the mask pattern surface enters the aperture pattern 1a and proceeds through the detection optical system. The light reaches the detector 7 and gives a peak in the amount of light received. on the other hand,
If the height of the reference plane deviates from the conjugate plane of the mask pattern plane, the projected image of the mask pattern plane and the second projected image on the reference plane will be out of focus and have blurred boundaries. Therefore, the optical information is impaired to the extent that the second projected image protrudes from the aperture pattern 1a and enters the aperture pattern, reducing the amount of light received reaching the detector 7.

Therefore, the stage 12 is moved by the drive system 15 to sequentially position the projected image at a plurality of locations determined on the mask pattern surface, and the control system 10 is moved at each location.
The height of the stage is adjusted by the drive system 9 to a height at which the detector 7 detects a change in the amount of light, and the height information is accumulated one after another. The optimum inclination angle of the stage is calculated from the height distribution information thus obtained, and the inclination of the stage 12 is corrected by the drive system 9 up to the calculated angle.

On the other hand, after the inclination has been adjusted, the projected image is again moved to approximately the center of the mask pattern, and the stage height is increased by the drive system 9 until the fiducial surface 1 is again at the height of the focal point. Adjust the brightness. Thereafter, the origin of the incident focus sensors 5 and 6 is adjusted using the fiducial surface 1 adjusted to the focal point height. That is, the reflected beam spot height on the fiducial surface 1 is memorized as the origin, and from then on, when the field of view of the projection optical system is scanned to any location on the stage, the incident focus sensor The height of the exposed surface of the sample is measured from the reflected beam spot heights at 5 and 6, and the control system 10 adjusts the stage height by the control system 9 so that the height becomes the origin height.

Next, the detection of the in-focus plane in this embodiment will be explained in more detail in various cases.

FIG. 2 is a diagram of the amount of detected light above and below the in-focus plane. It shows the relationship between focal positions. In this embodiment, if a special light guiding means, which will be described later, is also used, the detection peak/background ratio can be brought close to 50%, and more reliable detection can be achieved.

In FIG. 2, the horizontal axis is the height of the stage 12, with the focal point height Z0 as the center, the one closer to the projection optical system 2 is Z-, and the one farther away is Z+. The vertical axis is the detected amount of light. When the stage 12 is moved up and down, there is a height at which the amount of light reaches a maximum, and this is the focal point height Z0. In order to find this, the incident focus sensor 5,
Based on the signal 6, the stage 12 is moved up and down along the optical axis of the projection optical system 2. If the amount of light from the detector 7 is monitored at the same time, the diagram shown in FIG. 2 can be obtained. Based on this, the in-focus height Z0 is calculated by the autofocus control means 10, and thereafter the detection positions of the incident focus sensors 5 and 6 are made to coincide with it. Even when the stage 12 is moved by the XY drive system 15 and the wafer 11 is moved below the projection optical system 2, the incident focus sensors 5 and 6 bring the wafer to the focal plane of the projection optical system 2. It is possible to locate 11. By the way, it is better for the signal shown in FIG. 2 to have as large a slope as possible. For this purpose, the pattern of the aperture pattern 1a projected by the fiducial plate 1 must be
It is necessary to set the lines to an appropriate line width. For example, the projection pattern
Consider a line and space as shown in Figure 3. Let the pattern part of the fiducial plate 1 be 1a,
Pitch is P, opening width is a, duty ratio (a/p)
Assuming that 50%, the change in the focus position of the detection light in FIG. 2 is approximately as follows.

|Z0 −Z− |=|Z+ −
Z0 |=a/2tanθ...(1)

[0029] However, θ is the inclination angle of the light beam, and is an estimate when diffraction is ignored. For example, NA=0.5, σ=
0.5, when a=2μm, θ=14.5 degrees,
|Z0−Z−| becomes 3.9 μm.

By the way, in the case of a transparent mask 3 without a mask pattern, the lower glass surface of the mask 3 becomes a reflective surface, and its reflectance is about 4%, but since the background is small, the detection sensitivity is It is sufficiently detectable if the value is increased. Further, in the normal case where there is a mask pattern, a reflectance of 10 to 70% on the chrome surface is ensured, and sufficient detection is possible. Even if the chrome surface is coated with a low-reflection AR coating, the reflectance is only a few percent and there is no problem.

By the way, there is a step at the boundary between the chrome pattern and the glass surface, and there are also two conjugate planes on the mask pattern surface, but the thickness of the chrome pattern is 100 nm.
Since the following is true, there is no problem in practice when the projection optical system 2 has a reduced magnification. For example, if the thickness of the chrome pattern is 100 nm and the reduction projection magnification is 1/5, the error in the conjugate plane due to the step of the chrome is 8 nm, which is negligible.

[0032] Next, Japanese Patent Publication No. 1983, filed by the same applicant as the present application,
Consider a case where a so-called phase shift film disclosed in Japanese Patent No. 50811 is formed. The thickness of the phase shift film is d=λ/2(n-1), where n: refractive index, λ
: wavelength, and the reflected light on the surface of the phase shift film is twice the thickness of the phase shift film, that is, 2d=
It has an optical path length shorter than the reflected light on the glass surface of the mask by λ/(n-1). However, n is 1.
Since the value is selected to be about 5, this value is 2λ (an integral multiple of the wavelength), and the reflected light is apparently the same as when there is no phase shift film, so its influence is small.

As described above, since the mask pattern surface can be regarded as an ordinary reflective surface in any case, highly accurate detection is possible.

By the way, in order to further reduce the influence of the chrome pattern of the mask 3 and to eliminate the influence of astigmatism, etc. when detecting the focal point position around the field of view of the projection optical system 2, as shown in FIG. A projection pattern (aperture pattern 1a shape) as shown in FIG. 4 can be considered. Figure 4(a)
is a combination of vertical, horizontal, and diagonal patterns, as shown in Figure 4 (
b) is a checkered flag (checkered lattice) pattern. These are on the fiducial surface 1, 100 μm on each side.
It is formed in a rectangular area of ~500 μm. Furthermore, even in the case of a pattern as shown in FIG. 3, it is effective to tilt the sides of the pattern by 10 to 45 degrees with respect to the sides of the mask pattern. This is because mask patterns used in semiconductor manufacturing often have orthogonal vertical and horizontal patterns (0 degrees, 90 degrees).

FIG. 5 shows a special light guiding means for preventing the reflected light from each element of the illumination optical system including the illumination 8 from entering the detector 7 and causing a phenomenon that becomes a detection background. Give an example. In FIG. 5, the bifurcated fiber
The cable 13b has fibers forming the end face 13d and fibers forming the end face 13c arranged randomly on the end face 13e, so that the illumination optical path and the detection optical path are completely separated from each other, and the fibers forming the end face 13d and the fibers forming the end face 13c are arranged randomly on the end face 13e. The reflected light of the illumination light at does not reach the end surface 13d. Therefore, the end surface 13d is used as the detector 7, the end surface c is used as the light source 8, and the end surface 13e is used as the aperture pattern.
If they are connected to the respective channels 1a, the detection background will be smaller than when the transmitting/receiving system is separated using a half mirror 14 as shown in FIG.

As described above, according to this embodiment, the opening pattern 1 of the fiducial surface 1 provided on the stage 12
a onto the mask pattern surface via the projection optical system 2,
Since the observation is performed again from the aperture pattern 1a on the fiducial surface 1, TTL focusing can be performed directly on the mask pattern surface at any location via the projection optical system 2, which was previously difficult. Focus detection at the center of the screen is also easy. Furthermore, if the end face of the fiber cable 13 is placed conjugate with the exit pupil of the projection optical system 2, and the size of the end face is made equal to the size of the light source of the projection optical system,
It is now possible to detect the focused state of the reflected light of the projected image using the same σ value as when actual exposure transfer is performed.
High focusing accuracy can be expected.

By the way, when loading the wafer 11, the installation location of the fiducial surface 1 is determined by the projection optical system 2.
By placing the lens directly under the lens, focusing can be performed in parallel with loading, which is advantageous because there is no time loss. In this case, TTL focusing for about one minute is possible every time a wafer is replaced, and it is possible to easily cope with changes in the focal point position of the projection optical system 2 over time.

Furthermore, the projection pattern of the fiducial surface 1
(aperture pattern 1a) is incident on the incident focus sensor 5,
However, if the detection range of the incident focus sensors 5 and 6 is small, the incident focus may be detected at a location other than the aperture pattern 1a on the fiducial surface 1.
It is also possible to detect the focal point height by detecting it with the dust sensors 5 and 6. In this case, fiducial surface 1
The flatness and inclination must be sufficiently good, but some errors can be corrected later as offset values.

Furthermore, when the mask 3 is mounted at an angle as shown in FIG. It is possible to calculate the inclination of the wafer surface from the above and drive the leveling device 21 on the stage through the leveling control system 22 to position the wafer on a plane conjugate to the mask.

Furthermore, by providing a highly reflective surface on the outside of the circuit pattern of the mask 3, the amount of light returned to the detector 7 from the reflected light of the projected image of the mask pattern surface can be increased, resulting in high precision. can be expected to be detected.

By the way, the opening pattern 1a of the fiducial plate 1 is not limited to the grating made of slit-shaped openings as described above, but also the fiducial plate 101 made of a phase grating as shown in the plan view of FIG. It is also possible to do so. That is, in the pattern section 101a, 101b
101c and 101c are both transparent regions, but have different thicknesses and are formed to have a phase difference with respect to light passing through them. Specifically, a retardation is provided on a glass plate by etching or vapor deposition of a transparent material. When using such a phase grating, the amount of detected light can be increased because it does not block light compared to the fiducial plate 1 shown in FIG. Since it can be eliminated, detection accuracy can be improved, which is advantageous. By appropriately selecting the phase difference of this phase grating, an output signal as shown in FIG. 8 can be obtained, unlike FIG. 2. In this case, the position where the signal intensity is minimum is detected as the in-focus position, and other processing is the same as in the previous embodiment.

[0042]

Effects of the Invention The focus position detection device of the present invention can easily determine the in-focus point for each part of the actual mask pattern immediately before exposure transfer, and can detect a special mark within the transfer area of the mask pattern. In addition, even when the mask pattern occupies a large light-shielding area or when the exposure light intensity changes moment by moment, the in-focus point can be determined with high reliability.

The focus position detection device according to claim 2 of the present invention is capable of adjusting the exposure surface to coincide with the in-focus position at any location on the stage using a measuring means.

The focus position detection device according to claim 3 of the present invention is capable of adjusting the exposure surface to coincide with the in-focus position at any location on the stage using a measuring instrument.

The focal position detection device according to claim 4 of the present invention can determine the focal point without being influenced by the mask pattern.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a focusing point adjustment mechanism according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining light amount change detection in the embodiment of the present invention.

FIG. 3 is a plan view of a fiducial plate in an embodiment of the present invention.

FIGS. 4(a) and 4(b) are plan views of other examples of opening pattern shapes.

FIG. 5 is a schematic diagram of another example of a light guiding means.

FIG. 6 is a schematic diagram of an example of a leveling mechanism.

FIG. 7 is a plan view of a fiducial plate in another embodiment of the present invention.

8 is a diagram for explaining detection of a change in light amount by the fiducial plate shown in FIG. 7; FIG.

[Explanation of symbols]

1 Fiducial board 2 Projection optical system 3. Mask 4 Exposure light source system 5 Incidence focus sensor 6 Incidence focus sensor 7 Detector 8 Light source 9 Zθ drive system 10 Control system 11 Wafer 12 Stage 13 Fiber cable 14 Half mirror 15 XY drive system 1a Opening pattern

Claims (4)

[Claims] 1. A focal position detection device for detecting a stage-side conjugate position of a mask pattern surface with respect to a projection optical system, which includes: a reference plane on a stage on which an aperture pattern of a predetermined shape is formed; illumination means for guiding illumination light into the pattern;
The reflected light of the projected image of the aperture pattern formed on the mask pattern surface by the projection optical system under the illumination light is detected via the projection optical system and the aperture pattern, and the aperture pattern is detected. 1. A focal position detection device comprising: detection means for detecting a change in the amount of light of a projected image that has passed through the projection image. 2. The focal position detection device according to claim 1, further comprising: position adjustment means for moving the stage to a position where the maximum or minimum change in light quantity is obtained based on the output of the detection means; 1. A focal position detection device comprising: measuring means for measuring a positional shift direction at an arbitrary location on a stage with reference to the position of the reference plane in . 3. The focal position detection device according to claim 2, further comprising: a scanning mechanism that scans an arbitrary location on the stage under the field of view of the projection optical system; A focal position detection device comprising: a measuring device for measuring a position on the stage side with respect to the system; and the measuring means. 4. The focal position detection device according to claim 1, wherein the aperture pattern is formed in a plurality of parallel lines or checkerboard patterns arranged diagonally with respect to the mask pattern. A focal position detection device characterized by: