JP2008171947A - Exposure method and exposure device and device manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a pattern on a body under the state suppressing the dispersion of the line width (such as the dispersion of a hole diameter in the case of a contact-hole pattern) of the pattern. <P>SOLUTION: A first exposure moved in the Y-axis direction while arranging a wafer W at a first place displaced from the best focus place of a projection optical system PL to the -Z side and a second exposure moved in the same direction as the first exposure while arranging the wafer W at a second place from the best focus place to the +Z side are carried out by a main controller 50 by controlling a wafer stage WST through the desired value of a focus sensor AFS and a wafer-stage driving system 56. Accordingly, a target place related to the optic-axis direction of the projection optical system, which must position a wafer surface, is set on one side and the other side of the best focus place respectively by a first scanning exposure and a second scanning exposure, and exposures equalizing the scanning direction are conducted. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exposure method, an exposure apparatus, and a device manufacturing method, and in particular, an exposure method and an exposure apparatus that can be suitably used in a lithography process for manufacturing an electronic device (microdevice) such as a semiconductor element or a liquid crystal display element, The present invention relates to a device manufacturing method using the exposure method.

  In recent years, in a lithography process for manufacturing an electronic device (microdevice) such as a semiconductor element or a liquid crystal display element, a step-and-scan type scanning exposure apparatus (scanning stepper (also referred to as a scanner)) is relatively used. It has been. In this scanning stepper, a method called CDP is adopted as a method for ensuring an effective depth of focus of the projection optical system particularly when an isolated pattern is exposed. This CDP moves the substrate (substrate stage) in the scanning direction in synchronization with the reticle during scanning exposure, and the substrate (substrate stage) in the optical axis direction of the projection optical system during the period from the start of exposure to the end of exposure. This is a method of continuously changing the position (see, for example, Patent Document 1).

  By the way, semiconductor elements have been highly integrated year by year, and accordingly, further improvement in resolving power has been demanded for an exposure apparatus which is a semiconductor element manufacturing apparatus. For this reason, projection optical systems having a large numerical aperture (NA) have come to be used along with shortening of the exposure wavelength.

  Recently, in order to further improve the above-described resolution, a projection optical system having an NA exceeding 1.0 has been realized by a so-called immersion exposure technique.

  On the other hand, recently, when scanning exposure is performed using a contact hole pattern as a target pattern in a scanning exposure apparatus using, for example, an ArF excimer laser as a light source and a projection optical system having a high NA exceeding 0.7, for example, NA. When CDP is performed, it has been found that the variation in the diameter of the contact hole pattern (resist image) formed in the resist layer on the wafer after exposure may become unacceptably large.

JP-A-4-277612

  The inventor has conducted intensive research in order to investigate the cause of the variation in the diameter of the contact hole pattern described above. The main cause of the variation in the diameter of the contact hole pattern is the Z vibration of the wafer when the (periodic) uneven wafer surface is matched with the best focus surface by autofocus / leveling control in CDP. I came to speculate that. Therefore, the inventor performed the following simulation.

A contact hole with a diameter of 160 nm formed on a halftone mask with a transmittance of 6% using ArF excimer laser light (wavelength: 193 nm) as the illumination light for exposure and under normal illumination conditions with a coherence factor (σ value) of 0.85 Using a projection optical system with NA of 0.78 as a pattern to be exposed, the substrate (hereinafter referred to as a wafer) is exposed, and after development, a contact hole pattern (resist image) having a diameter of 110 nm is formed on the wafer. The condition of forming was assumed. Further, from the start of exposure to the end of exposure, CDP for continuously changing the focus position (the position (Z position) of the wafer surface with respect to the optical axis direction of the projection optical system) is performed, and the Z swing width is set to the best focus position Z. as the range of 600nm centered at _best, it was be continuously changed in the Z position of the wafer surface _{(Z best -300nm) ~ (Z} best + 300nm). At this time, a CDP simulation in which the vibration (Z vibration) in the optical axis direction of the projection optical system according to the sine curve Z = Asinωt is superimposed on the change in the Z position of the wafer surface is performed. (Frequency) ω was changed at a predetermined interval, and the measurement was repeated for A = + 40 nm and A = −40 nm. Here, the frequency ω is the number of repetitions of vibration while one point on the wafer crosses the irradiation area of the exposure illumination light (a predetermined width D, for example, a slit-shaped exposure area having a width of 8 mm).

  As a result, when the frequency ω is about 0.75, the error (variation in diameter) from the target value of the diameter of the contact hole (hereinafter simply referred to as “hole diameter” where appropriate) is maximized. Obtained.

  FIG. 4 shows the result of the simulation. In FIG. 4, the horizontal axis represents the frequency ω of Z vibration (Z = Asinωt), and the vertical axis represents the hole diameter CD (nm).

In FIG. 4, the longer curve shows the case of A = + 40 nm, and the shorter curve shows the case of A = −40 nm. In FIG. 4, two straight lines in the vicinity of the target hole diameter of 110 nm are the hole diameter CD when the upper broken line has a high frequency (a high frequency that vibrates several tens of times during scanning exposure). The lower one-dot chain line always shows the hole diameter when there is a defocus of 20 nm and there is no vibration. A straight line (dotted line) substantially coincident with the hole diameter of 114 nm indicates a hole diameter when the Z swing width of the CDP is 40 nm, which is 40 nm less than the target 600 nm, and a straight line near the hole diameter of 106 nm indicates the ZP ZD The hole diameter when the oscillation width is 640 nm, which is 40 nm larger than the target 600 nm, is shown. From the simulation results of FIG. 4, the following a. To c. Can be said.
a. The influence amount of the error of the Z position on the wafer surface with respect to the resist image line width (in this case, the hole diameter) CD depends on the frequency ω of the Z vibration.
b. When the frequency ω is about 0.75, the influence is maximum, and the influence amount is larger than when the ZP width of the CDP is shifted from the target 600 nm by ± 40 nm. When the frequency is about 0.75, a difference in resist image line width (in this case, hole diameter) CD of 11 nm is caused by a Z error of +/− 20 nm between A = + 40 nm and A = −40 nm. .
c. When the frequency ω is 1.5 or more, the influence of the Z vibration is not dominant.

  As a result of the above simulation, the inventor found that when the wafer surface with periodic irregularities was made to coincide with the best focus surface by autofocus / leveling control in CDP, a Z vibration with a frequency smaller than 1.5 was generated on the wafer. It came to judge that.

Accordingly, the inventor also uses the DP method (also referred to as the flex method), which is a technique for ensuring an effective depth of focus, not involving the Z vibration of the wafer, under the above exposure conditions. The simulation was performed to determine the error of the line width (in this case, the hole diameter) CD by giving an amplitude error of 300 nm and giving a defocusing error. In this case, it is not possible to instantaneously move the wafer Z position from the first position (Z _best −150 nm) to the second position (Z _best +150 nm) or from the second position to the first position during scanning exposure. It is not possible, but it is possible with simulation. Therefore, in the DP simulation, the scanning exposure period is divided into the first half and the second half. In the first half, the Z position on the wafer surface is set to the first position (or the second position), and in the second half, the Z position on the wafer surface is set to the second position ( Alternatively, it is assumed that scanning exposure is performed with the first position set.

  And the simulation result of CDP and DP was compared. FIG. 5 shows an example of the comparison result.

  In FIG. 5, “Amp.−20 nm” and “Amp. + 20 nm” indicate a case where the Z swing width is 20 nm less than the target Z swing width and 20 nm greater, respectively. In FIG. 5, “Defocus 20 nm” indicates a case where there is a defocus of 20 nm. Further, in FIG. 5, “Vibration (min)” and “Vibration (max)” are ω = 0 when Z vibration (Z = Asin ωt) of ω = 0.75 and A = + 40 nm is superimposed in CDP. .75 and A = −40 nm vibrations (Z = Asinωt) are respectively superimposed. Further, the Z vibration in the DP is always almost zero.

  As is apparent from the comparison result of FIG. 5, the line width error (in this case, hole diameter error, that is, variation in hole diameter) ΔCD caused by defocus is about the same between CDP and DP. ΔCD generated due to the Z vibration of the wafer during scanning exposure is significantly larger in the case of CDP than in DP. On the other hand, the ΔCD caused by the Z swing width error is smaller in the CDP than in the DP (about half).

  However, in an actual exposure apparatus, it is rare that the Z amplitude error is 20 nm, and the Z amplitude error is different for each exposure apparatus.

  As a result of thinking repeatedly on the premise of the above, the inventors divided the exposure into two times, and the light of the projection optical system to position the wafer surface by the first scanning exposure and the second scanning exposure. Different target positions with respect to the axial direction, for example, by setting the target positions on one side and the other side of the best focus position in the first scanning exposure and the second scanning exposure, respectively, substantially the above DP It has been concluded that exposure with the same effect can be realized, and that variation in hole diameter can be reduced by making the scanning direction the same in the first scanning exposure and the second scanning exposure. The reason why the variation in hole diameter can be reduced is that, in an actual scanning exposure apparatus, the above-described Z vibration occurs during scanning exposure, but the Z vibration is caused by periodic unevenness on the wafer surface. Because it is based on the Z-pitching operation of the wafer during auto-leveling, it should be within the range of measurement reproducibility if autofocus is performed accurately and the scanning direction (wafer movement direction) is the same. It is. Therefore, even if Z vibration with a low frequency (low frequency) occurs, the focus error due to the Z vibration during the first scanning exposure and the focus error due to the second Z vibration are offset. It is possible.

  The present invention has been made on the basis of the novel knowledge obtained by the inventor described above. From the first viewpoint, the object is exposed with a pattern generated through the optical system while moving the object in the scanning direction. A first exposure step of exposing the object in a pattern by moving in the scanning direction while placing the object at a first position shifted to one side from a best focus position of the optical system; An exposure method comprising: a second exposure step of exposing the object in the pattern by moving in the same direction as the first exposure step while disposing the object at a second position shifted from the best focus position to the other side. It is.

  According to this, it is possible to form a pattern on an object in a state where variations in the line width of the pattern (such as variations in hole diameter in the case of a contact hole pattern) are suppressed.

  From a second viewpoint, the present invention is a device manufacturing method including a step of exposing an object with a pattern using the exposure method of the present invention; and a step of processing the object.

  According to a third aspect of the present invention, there is provided an exposure apparatus for exposing an object with a pattern generated via an optical system, the object stage holding the object and movable in at least one axial direction; An adjustment device that adjusts the positional relationship between the pattern and the object in the optical axis direction; and a first position that is shifted to one side from the best focus position of the optical system by controlling the object stage and the adjustment device. A second exposure that moves in the same direction as the first exposure while placing the object at a second position shifted from the best focus position to the other side. And a control device that executes exposure.

  According to this, the control device controls the object stage and the adjustment device, and the first object moves in the uniaxial direction while placing the object at a first position shifted to one side from the best focus position of the optical system. Exposure and second exposure that moves in the same direction as the first exposure while placing the object at a second position shifted to the other side from the best focus position are performed. As a result, in the first scanning exposure and the second scanning exposure, the target position in the optical axis direction of the projection optical system for positioning the object surface is set on one side and the other side of the best focus position, respectively, and scanning is performed. Exposure with the same direction is performed, and a pattern can be formed on an object in a state where variations in the line width of the pattern (such as variations in hole diameter in the case of a contact hole pattern) are suppressed.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a schematic configuration of an exposure apparatus 10 according to an embodiment. The exposure apparatus 10 is a step-and-scan scanning exposure apparatus (so-called scanner).

  The exposure apparatus 10 includes a light source 16, an illumination optical system 12, a reticle stage RST that holds a reticle (mask) R illuminated by exposure illumination light (hereinafter referred to as exposure light) IL from the illumination optical system 12, and a reticle R Projection optical system PL for projecting the exposure light IL through the wafer onto the wafer (object) W, a wafer stage WST for holding the wafer W, a main controller 50 for controlling these, and the like.

  As the light source 16, for example, an excimer laser that emits ultraviolet pulse light having a wavelength of 193.4 nm is used. The output of the beam monitor inside the light source 16 is supplied to a laser controller inside the light source 16. The laser controller controls the light source 16 based on command information from the main controller 50. As a light source, a KrF excimer laser (output wavelength 248 nm) may be used.

  The illumination optical system 12 is connected to the light source 16 via a light transmission optical system including a beam matching unit, for example. The illumination optical system includes, for example, a uniform illumination optical system including a fly-eye lens as an optical integrator as disclosed in Japanese Patent Application Laid-Open No. 2001-313250 (corresponding to US Patent Application Publication No. 2003/0025890). System, reticle blind, etc. (all not shown). Also, for example, in the illumination optical system, for example, an exchangeable diffractive optical element, a plurality of prisms (such as an axicon) whose distance in the optical axis direction is variable, and a zoom optical system are arranged on the incident side of the fly-eye lens A molding optical system is provided. The movement and / or exchange of the optical elements in the shaping optical system is controlled by the main controller 50, so that it is generated on the pupil plane of the illumination optical system 12 (in this example, coincident with the exit-side focal plane of the fly-eye lens). The shape of the secondary light source can be changed, and the size of the secondary light source, that is, the coherence factor (σ value: the ratio of the numerical aperture of the illumination light beam from the secondary light source to the reticle side numerical aperture of the projection optical system) ) Can be continuously variable. Thereby, the illumination condition of the reticle R can be arbitrarily set. As the optical integrator, an internal reflection type integrator (such as a rod integrator) or a diffractive optical element can be used in addition to a fly-eye lens.

  The exposure light IL emitted from the illumination optical system 12 passes through a mirror M and a condenser lens 32, and then has a slit-like shape that extends in the X-axis direction (the direction orthogonal to the plane of FIG. 1) on the reticle R held by the reticle stage RST. The illumination area 42R is irradiated with a uniform illuminance distribution. The illumination optical system described above may also include the mirror M and the condenser lens 32.

  On reticle stage RST, reticle R is placed and held by suction via a vacuum chuck or the like (not shown). Reticle stage RST can be driven minutely in the horizontal plane (XY plane) and is moved within a predetermined stroke range in the scanning direction (here, the Y-axis direction which is the horizontal direction in FIG. 1) by reticle stage driving system 49. Scanned. The position and amount of rotation of reticle stage RST during scanning are measured by laser interferometer 54R via movable mirror 52R (or a reflection surface formed on its side surface) fixed on reticle stage RST, and this laser interference. The measured value of the total 54R is supplied to the main controller 50.

  The projection optical system PL is a double-sided telecentric reduction system, for example, and includes a plurality of lens elements arranged along an optical axis AX parallel to the Z-axis direction. Further, the projection optical system PL has a maximum numerical aperture (NA) (maximum NA) of, for example, 0.85, and the numerical aperture can be adjusted by the main controller 50 via an aperture stop (not shown). . Further, the projection magnification β of the projection optical system PL is, for example, ¼. For this reason, when the illumination area 42R on the reticle R is illuminated by the exposure light IL, the pattern formed on the reticle R is reduced and projected at the projection magnification β by the projection optical system PL, and a reduced image (partial image) of the pattern is obtained. Is formed (formed) in an exposure region 42W conjugate to the illumination region 42R on the wafer W on which a resist (photosensitive material) is applied (resist layer is formed).

  On wafer stage WST, wafer W is held by vacuum suction or the like via a wafer holder (not shown). Wafer stage WST is freely driven in the XY plane by a linear motor or the like constituting wafer stage drive system 56 (including rotation around Z axis (θz rotation)) and constitutes wafer stage drive system 56. For example, three actuators (piezo element, voice coil motor, etc.) finely drive in the Z-axis direction and the tilt direction with respect to the XY plane (rotation direction around the X axis (θx direction), rotation direction around the Y axis (θy direction)) Is done. Position information and rotation information in the XY plane of wafer stage WST (rotation about the X axis (θx rotation), rotation about the Y axis (θy rotation), and rotation about the Z axis (θz rotation)) are determined by wafer stage WST. Is measured by a laser interferometer 54W through a movable mirror 52W fixed to the main body 50, and the measured value of the laser interferometer 54W is supplied to the main controller 50. Instead of the 6-degree-of-freedom stage (wafer stage WST) described above, an XY stage that freely moves in the XY plane, and mounted on the XY stage, can be finely driven in the Z-axis direction and the tilt direction relative to the XY plane A wafer stage including a Z tilt stage may be used. Instead of moving mirror 52W, the end surface of wafer stage WST may be mirror-finished to form a reflecting surface (corresponding to the reflecting surface of moving mirror 52W).

  On the wafer stage WST, a reference plate FP is fixed so that the surface thereof is the same height as the surface of the wafer W. On the surface of the reference plate FP, a reference mark used for baseline measurement or the like of the alignment detection system AS described below is formed.

  The exposure apparatus 10 is provided with an off-axis type alignment detection system AS that detects alignment marks formed on the wafer W. As this alignment detection system AS, for example, an image processing type alignment sensor that illuminates a mark with broadband light such as a halogen lamp and measures the mark position by image processing of the mark image is used. . The detection signal of the alignment detection system AS is supplied to the main controller 50 via an alignment controller (not shown).

  The position and the amount of tilt in the Z-axis direction on the surface of the wafer W are determined by, for example, the light transmission system 90a and the light reception disclosed in Japanese Patent Laid-Open No. 6-283403 (corresponding US Pat. No. 5,448,332). It is measured by a focus sensor AFS comprising an oblique incidence type multipoint focal position detection system having a system 90b. The measurement value of the focus sensor AFS is also supplied to the main controller 50. In the focus sensor AFS, at least some of the plurality of measurement points are set in the exposure area 42W.

  Further, in the exposure apparatus 10 of the present embodiment, although not shown, for example, in JP-A-7-176468 (corresponding to US Pat. No. 5,646,413), etc. above the reticle R. A pair of reticle alignment detection systems comprising a disclosed TTR (Through The Reticle) alignment system using light having an exposure wavelength is provided, and the detection signal of the reticle alignment detection system is sent to the main controller via the alignment controller. 50.

  The main controller 50 includes a so-called microcomputer (or workstation) composed of a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), etc. In addition to performing the various controls described above, for example, synchronous scanning of the reticle R and the wafer W, stepping of the wafer W, exposure timing, and the like are controlled so that the exposure operation is performed accurately. In addition, the main controller 50 performs overall control of the entire apparatus, in addition to controlling the exposure amount at the time of scanning exposure.

Specifically, the main controller 50 scans the reticle R with respect to the illumination area 42R in the + Y direction (or −Y direction) at a speed V _R = V via the reticle stage RST, for example, during scanning exposure. In synchronization with the wafer W, the wafer W is scanned in the −Y direction (or + Y direction) with respect to the exposure area 42W at a speed V _W = β · V (β is the projection magnification from the reticle R to the wafer W) via the wafer stage WST. As described above, the positions and speeds of reticle stage RST and wafer stage WST are controlled via reticle stage drive system 49 and wafer stage drive system 56 based on the measurement values of laser interferometers 54R and 54W, respectively. At the time of stepping, main controller 50 controls the position of wafer stage WST via wafer stage drive system 56 based on the measurement value of laser interferometer 54W.

Next, the processing algorithm of the main controller 50 is used for a series of operations when the exposure apparatus 10 transfers a pattern including an isolated contact hole pattern onto one lot (for example, 25 or 50) of wafers W. It demonstrates along the flowchart of FIG. 3 shown. On each wafer W, one or more layers have already been exposed, and as shown in FIG. 2, a plurality of, here, 76 shot areas S _{1 to} S ₇₆ are formed. relative ₁ to S _76, shall be formed by superimposing a pattern including a contact hole pattern isolated.

  Here, as the reticle R, for example, a halftone reticle having a transmittance of 6% in which a plurality of contact hole patterns having a diameter of 440 nm, for example, are formed at intervals larger than 1.3 μm is used.

  First, at step 102 in FIG. 3, main controller 50 loads reticle R onto reticle stage RST via a reticle loader (not shown).

  In the next step 104, main controller 50 determines the illumination condition corresponding to reticle R, here the normal illumination condition with a coherence factor (σ value) of 0.85, and the above-described shaping optical system in illumination optical system 12. Set through. Further, main controller 50 sets NA of projection optical system PL to 0.78 through the above-described aperture stop.

  In the next step 106, main controller 50 sets the exposure amount target value to ½ of the exposure amount to be applied to wafer W in normal exposure.

  In the next step 108, the main controller 50 uses the reticle alignment detection system, the reference plate FP, the alignment system AS, and the like in the same procedure as that of a normal scanning stepper (scanner), and the reticle alignment and alignment system AS. Perform baseline measurements.

  In the next step 110, the main controller 50 initializes the count value m of the first counter indicating the wafer number in the lot to 1 (m ← 1).

  In the next step 112, the main controller 50 initializes the count value n of the second counter indicating the number of times of exposure for the same layer (layer) to 1 (n ← 1).

  In next step 114, main controller 50 replaces wafer W on wafer stage WST using a wafer unloader and a wafer loader (not shown). However, when there is no wafer W on wafer stage WST, wafer W is simply loaded.

  In the next step 116, the main controller 50 performs wafer alignment (for example, enhanced global alignment (EGA) disclosed in Japanese Patent Laid-Open No. 61-44429).

  In the next step 118, main controller 50 determines whether or not the count value n of the second counter is 1. In this case, since n is initialized to 1, the determination here is affirmed and the routine proceeds to step 120.

In step 120, main controller 50 sets the target focus position at the time of scanning exposure, that is, the target value of the position of the surface of wafer W in the Z-axis direction to (Z _best −ΔZ). Here, Z _best is the best focus position (value obtained in advance) of the projection optical system PL, and ΔZ is 1/2 of the Z swing width, for example, 150 nm when the Z swing width is 300 nm.

  Next, in step 124, a scanning exposure operation in which the above-mentioned reticle stage RST and wafer stage WST are synchronously moved under the illumination conditions, exposure target value, and target focus position set in steps 104, 106, 120, respectively. Step-and-repeat which alternately repeats the movement (stepping) operation between shots in which the wafer stage WST is moved along the path as shown in FIG. 2 after the exposure of the shot area is completed and before the exposure of the next shot area is started. • Perform a scanning exposure operation. Here, at the time of the above-described scanning exposure, the main controller 50 gives a command value such as pulse energy corresponding to the previously set exposure amount target value and a repetition frequency of laser emission to the laser controller in the laser light source 16.

FIG. 2 shows a movement locus (path) of the center of the exposure area 42W with respect to the wafer W (corresponding to the optical axis AX of the projection optical system PL) during the step-and-scan exposure operation. Actually, the exposure area 42W is fixed and the wafer W moves. In FIG. 2, for the sake of convenience, the center of the exposure area 42W moves on the fixed wafer W. In this way, the first scanning exposure using the reticle R is performed on the shot areas S _{1 to} S ₇₆ on the wafer W. During scanning exposure of each shot area S _i (i = 1 to 76), main controller 50 sets the target focus position as (Z _best −ΔZ), and the Z axis of the surface of wafer W based on the measurement value of focus sensor AFS. The direction position and tilt amount are controlled, that is, focus leveling control is performed.

  After completion of the first scanning exposure, the process proceeds to step 126, and main controller 50 determines whether or not count value n described above is two. In this case, since the count value n is 1, the determination here is denied, and the main controller 50 increments the count value n by 1 (n ← n + 1) in step 128, and then returns to step 118 to obtain the second It is determined whether or not the count value n of the counter is 1. In this case, since n is 2, the determination here is denied and the routine proceeds to step 122.

In step 122, main controller 50 sets the target focus position at the time of scanning exposure, that is, the target value of the position in the Z-axis direction on the surface of wafer W to (Z _best + ΔZ).

In step 124, the main controller 50, after returning the wafer stage WST in the scan (acceleration) starting position for exposure of shot areas S _1, respectively set illumination conditions in step 104,106,122, A step-and-scan exposure operation is executed at the exposure amount target value and the target focus position. During the second exposure operation, main controller 50 moves wafer stage WST (wafer W) relative to exposure region 42W along the same movement trajectory (path) as in the first time shown in FIG. The Further, during the scanning exposure of each shot area S _i (i = 1 to 76), main controller 50 sets the target focus position to (Z _best + ΔZ) and Z on the surface of wafer W based on the measurement value of focus sensor AFS. The position and tilt amount in the axial direction are controlled, that is, focus leveling control is performed.

In this way, double exposure of the pattern of the reticle R on the shot areas S _{1 to} S ₇₆ on the wafer W by scanning exposure at different target focus positions is completed.

  After the end of the second exposure operation, that is, after the end of the double exposure operation, main controller 50 determines in step 126 whether or not the aforementioned count value n is 2. In this case, since the count value n is 2, the determination here is affirmed and the routine proceeds to step 130.

  In step 130, main controller 50 determines whether the count value m of the first counter described above is M (M is 25 or 50). In this case, since m is initialized to 1, the determination here is denied, and in step 132, main controller 50 increments count value m by 1 (m ← m + 1), and then returns to step 112. Thereafter, the processing after step 112 is repeated until the determination in step 130 is affirmed. When the second exposure of the Mth wafer W in the lot is completed, the determination in step 130 is affirmed, and a series of processes of this routine is ended.

  As a result, double exposure similar to that described above is performed on the second and subsequent wafers W in the lot, and a plurality of reticle R patterns (patterns including a plurality of isolated contact hole patterns) are formed on the wafer W. Formed in each of the shot regions.

As described above, according to the exposure apparatus 10 of the present embodiment, the main controller 50 controls the wafer stage WST via the focus sensor AFS and the wafer stage drive system 56, and the best focus position of the projection optical system PL. shift first exposure moving the shot area S _i of the exposure target wafer W while the Y-axis direction arranged in a first position displaced in the -Z side (Z _best -ΔZ), from the best focus position on the + Z side from the Further, the second exposure that moves in the same direction as the first exposure while placing the shot area S _i to be exposed on the wafer W at the second position (Z _best + ΔZ) is performed for each shot area S _i . Thereby, the target position regarding the optical axis AX direction (Z-axis direction) of the projection optical system PL where the surface of the wafer W should be positioned is set to one side and the other side of the best focus position in the first exposure and the second exposure, respectively. Each shot on the wafer W having a resist (photosensitive material) coated on the surface is a projection image of the pattern on the reticle R which is set and scanned in the same scanning direction and projected by the projection optical system PL. Regions S ₁ -S ₇₆ can be exposed. In this case, the first exposure and the second exposure are performed with the same scanning direction for each shot area on the wafer W with the first position and the second position as the target focus positions, respectively. High-resolution exposure is possible with a large depth of focus and almost no influence of vibration of the wafer W during focus leveling due to periodic irregularities on the surface of the wafer W. Therefore, by developing the wafer W with the developing device, the pattern (in this case, the resist image) is transferred onto the wafer W in a state where variations in the line width of the pattern (such as variations in the hole diameter in the case of the contact hole pattern) are suppressed. _Can be formed in each shot area S _i .

In the above embodiment, the wafer W is moved with respect to the exposure area 42W along exactly the same movement locus (path) in the first exposure operation and the second exposure operation, and step-and-step Although scanning exposure is performed, the present invention is not limited to this. In short, for each shot area S _i on the wafer W, if the scanning direction is the same for the first exposure and the second exposure, the moving path of the overall wafer, the first exposure and the second The exposure may be different. In the method of the above embodiment, there is no difference in the position of the wafer W in the X-axis direction between the first exposure and the second exposure. Therefore, the Z vibration caused by the Z / pitching operation of the wafer during focus / leveling. Can be reliably kept within the range of measurement reproducibility. Therefore, even if there is a difference in position in the X-axis direction, the movement path of the wafer W is not particularly limited as long as the influence can be ignored.

In the above embodiment, the case where the first position and the second position are shifted from the best focus position Z _best by the same amount ΔZ has been described, but the present invention is not limited to this, and the first position The position and the second position may be shifted from the best focus position to the −Z side and the + Z side, respectively.

  In the above embodiment, the case where the first exposure and the second exposure have the same illumination condition and the same target exposure amount has been described. However, for example, the target exposure amount is not necessarily set to be the same. .

  In the above embodiment, the case where the first exposure and the second exposure are performed, that is, the case where the double exposure using the same pattern is performed has been described. However, the present invention is not limited to this, and the first exposure and the second exposure described above. If multiple exposures using the same pattern as the above are included, multiple exposures of triple exposure or more may be performed. In this case, at least one of the illumination condition and the target exposure amount may be varied by at least one exposure.

  In the above embodiment, the projection optical system of the projection image of the pattern by the projection optical system PL and the surface of the wafer W is adjusted by adjusting the position of the wafer stage WST (wafer W) in the Z-axis direction or the inclination with respect to the XY plane. Although the case where the positional relationship of the PL with respect to the optical axis AX direction (Z-axis direction) is adjusted has been described, at least one of the reticle stage RST (reticle R) and the optical elements of the projection optical system PL instead of or in addition to this. A configuration may be adopted in which the positional relationship in the Z-axis direction between the projection image of the pattern by the projection optical system PL during scanning exposure and the surface of the wafer W is adjusted by driving one of them. Further, the positional relationship between the projected image of the pattern and the surface of the wafer W may be adjusted by slightly shifting the center wavelength of the exposure light IL.

  In the above embodiment, the positional relationship in the Z-axis direction between the projection image of the pattern (image plane of the projection optical system PL) and the surface of the wafer W is adjusted using the measurement value of the focus sensor AFS. Another sensor, for example, an interferometer that measures the positional relationship between the projection optical system PL and the wafer stage WST in the Z-axis direction is provided, and the positional relationship between the projected image and the wafer is adjusted using the measurement value of the interferometer. May be. In this case, the focus sensor AFS need not be provided. For example, the focus sensor AFS is disposed away from the projection optical system PL, and the position information on the surface of the wafer W is measured by the focus sensor AFS prior to the exposure operation. The measured position information is also preferably used in the exposure operation.

  In the above embodiment, the case where 76 shot areas are formed on the wafer W has been described. However, it is sufficient that at least one shot area is formed on an object on which a pattern is formed, for example, a wafer. . In short, it is only necessary that the first position and the second position can be set as the control target position of the wafer in the optical axis direction and the scanning direction can be made the same in the first exposure and the second exposure for the same shot area. .

  In the above embodiment, as exposure light, as disclosed in, for example, International Publication No. 1999/46835 pamphlet and US Pat. No. 7,023,610 corresponding thereto, a DFB semiconductor laser or fiber Infrared or visible single-wavelength laser light oscillated from the laser is amplified by, for example, a fiber amplifier doped with erbium (or both erbium and ytterbium) and converted into ultraviolet light using a nonlinear optical crystal. Harmonic harmonics may be used.

As a light source, a light source that generates vacuum ultraviolet light such as an F ₂ laser beam having a wavelength of 157 nm, a Kr ₂ laser beam having a wavelength of 146 nm, an Ar ₂ laser beam having a wavelength of 126 nm, or a bright line such as g-line or i-line is generated. A mercury lamp or the like may be used.

  Further, the projection optical system may be not only a reduction system but also an equal magnification and an enlargement system. The projection optical system is not only a refractive system but also a reflective system and a catadioptric system (for example, an inline type disclosed in WO 2004/107011 (corresponding US Patent Application Publication No. 2006/0121364)) The projection image may be either an inverted image or an erect image.

  In the above embodiment, the case where the present invention is applied to a step-and-scan type scanning exposure apparatus has been described. However, the present invention is not limited to this, and the present invention is not limited to the step-and-stitch method (step-and-stitch method). The present invention can also be suitably applied to a scanning type exposure apparatus.

  In addition, for example, International Publication No. 2004/053955 (corresponding to US Patent Application Publication No. 2005/0252506), European Patent Publication No. 1,420,298, International Publication No. 2004/055803, US The present invention may also be applied to an immersion type exposure apparatus disclosed in Japanese Patent No. 6,952,253 and the like in which a liquid is filled between the projection optical system and the wafer. Further, for example, JP-A-10-163099 (corresponding US Pat. No. 6,590,634), JP 2000-505958 (corresponding US Pat. No. 5,969,441), US As disclosed in Japanese Patent No. 6,208,407, etc., a multi-stage type exposure apparatus having a plurality of stages, or for example, Japanese Patent Laid-Open No. 11-135400 (corresponding to International Publication No. 1999/23692) As disclosed in JP 2000-164504 A (corresponding US Pat. No. 6,897,963) and the like, an exposure apparatus including a measurement stage having a measurement member (reference mark, sensor, etc.) The present invention can also be applied.

  In the above embodiment, a light transmission type mask (reticle) in which a predetermined light shielding pattern (or phase pattern / dimming pattern) is formed on a light transmissive substrate is used. Instead of this mask, for example, As disclosed in US Pat. No. 6,778,257, an electronic mask (variable molding mask) that forms a transmission pattern, a reflection pattern, or a light emission pattern based on electronic data of a pattern to be exposed is disclosed. It may be used. As the variable shaping mask, for example, a DMD (Digital Micro-mirror Device) which is a kind of non-light-emitting image display element (also referred to as a spatial light modulator) can be used. When a variable molding mask is used, a pattern generator that generates a pattern that includes the variable molding mask and changes in synchronization with the movement of an object such as a wafer (an object stage that holds the object) is configured. The object can be exposed with an image of a pattern generated by and projected by the optical system. The present invention can also be suitably applied to an exposure apparatus provided with such a pattern generator.

  The present invention is also applied to an exposure apparatus (lithography system) that forms a device pattern on a wafer W by forming interference fringes on the wafer W as disclosed in International Publication No. 2001/035168. Can be applied.

  Further, the use of the exposure apparatus is not limited to the exposure apparatus for semiconductor production, but for example, an exposure apparatus for manufacturing a display such as a liquid crystal display element formed on a square glass plate or the like, a thin film magnetic head Also, it can be widely applied to an exposure apparatus for manufacturing micromachines, DNA chips, and the like. Further, in order to manufacture reticles or masks used in not only microdevices such as semiconductor elements but also light exposure apparatuses, EUV exposure apparatuses, X-ray exposure apparatuses, electron beam exposure apparatuses, etc., glass substrates or silicon wafers, etc. The present invention can also be applied to an exposure apparatus that transfers a circuit pattern. The object to be exposed is not limited to a wafer, and may be, for example, a glass plate, a ceramic substrate, a film member, or mask blanks, and the shape is not limited to a circle but may be a rectangle.

  In the semiconductor device, a step of designing a function / performance of the device, a step of manufacturing a reticle based on the design step, a step of manufacturing a wafer from a silicon material, and executing the above-described exposure method by the exposure apparatus of the above-described embodiment. It is manufactured through lithography steps, device assembly steps (including dicing process, bonding process, and packaging process), inspection steps, etc. that expose the wafer with an image of the reticle pattern projection optical system and develop the exposed wafer. The In this case, in the lithography step, the exposure method described above is executed using the exposure apparatus of the above embodiment, and a device pattern is formed on the wafer. Therefore, a highly integrated device can be manufactured with high productivity. In addition, when using the exposure apparatus provided with the variable shaping mask mentioned above as an exposure apparatus, a wafer is exposed by the image by the optical system of the pattern produced | generated with the variable shaping mask. Also in this case, a highly integrated device can be manufactured with high productivity by forming a device pattern on the wafer by two scanning exposures (double exposure) at different target focus positions as described above. it can.

  As described above, the exposure method, the exposure apparatus, and the device manufacturing method of the present invention are suitable for manufacturing an electronic device (microdevice).

It is a figure which shows schematically the structure of the exposure apparatus of one Embodiment. It is a figure which shows arrangement | positioning of the shot area | region on a wafer, and the relative movement locus | trajectory (path | route) of the exposure area | region center with respect to a wafer. 7 is a flowchart showing a processing algorithm of the main controller 50 in a series of operations when a pattern including an isolated contact hole pattern is transferred onto one lot of wafers. It is a figure which shows the simulation result regarding CDP which the inventor performed, Comprising: When changing the position Z regarding the optical axis direction of the projection optical system of a wafer surface continuously with a predetermined Z swing width, Z = Asinωt (A = +40 nm or A = −40 nm) CDP simulation in which the vibration (Z vibration) in the optical axis direction of the projection optical system is superimposed on the change in Z (wafer surface position). It is a figure which shows the result obtained when it changed by. It is a figure which shows an example of the comparison result which compared the simulation result regarding CDP, and the simulation result regarding DP which the inventor performed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Exposure apparatus, 50 ... Main controller, 56 ... Wafer stage drive system, PL ... Projection optical system, W ... Wafer, WST ... Wafer stage, AFS ... Focus sensor, R ... Reticle, RST ... Reticle stage.

Claims (17)

An exposure method for exposing the object with a pattern generated via an optical system while moving the object in a scanning direction,
A first exposure step of exposing the object in a pattern by moving in the scanning direction while disposing the object at a first position shifted to one side from a best focus position of the optical system;
An exposure method comprising: a second exposure step of exposing the object in the pattern by moving in the same direction as the first exposure step while disposing the object at a second position shifted from the best focus position to the other side. .   The exposure method according to claim 1, wherein the first position and the second position are shifted from the best focus position by the same amount.   The exposure method according to claim 1 or 2, wherein a target exposure amount is set to be the same in the first exposure step and the second exposure step.   4. The pattern according to claim 1, wherein the pattern is an image of a pattern formed on a mask moved in the scanning direction in synchronization with the movement of the object and projected by the optical system. 5. Exposure method.   The exposure method according to claim 1, wherein the pattern is an image of a pattern that is generated by a pattern generation device and projected by the optical system in synchronization with the movement of the object.   The exposure method according to claim 1, wherein the pattern includes a contact hole pattern.   The exposure method according to claim 1, wherein the object is subjected to multiple exposure including the first and second exposures.   The exposure method according to any one of claims 1 to 7, wherein the same photosensitive layer on the object is exposed with the pattern in the first exposure step and the second exposure step. A step of exposing an object with a pattern using the exposure method according to claim 1;
A method of manufacturing a device, comprising: a step of processing the object. An exposure apparatus that exposes an object with a pattern generated via an optical system,
An object stage that holds the object and is movable in at least one axis direction;
An adjustment device for adjusting a positional relationship between the pattern and the object in the optical axis direction of the optical system;
A first exposure that controls the object stage and the adjusting device to move in the uniaxial direction while placing the object at a first position shifted to one side from a best focus position of the optical system; and the best focus An exposure apparatus comprising: a control device that executes a second exposure that moves in the same direction as the first exposure while disposing the object at a second position shifted from the position to the other side.   The exposure apparatus according to claim 10, wherein the first position and the second position are shifted from the best focus position by the same amount.   12. The exposure apparatus according to claim 10, wherein the control device sets a target exposure amount to be the same for the first exposure and the second exposure.   The pattern is an image of a pattern formed on the mask that is moved in the uniaxial direction in synchronization with the movement of the object and projected by the optical system, and is movable in the uniaxial direction while holding the mask. The exposure apparatus according to claim 10, further comprising a mask stage.   The image processing apparatus further includes a pattern generation device that generates a pattern that changes in synchronization with the movement of the object, and the pattern is an image of a pattern that is generated by the pattern generation device and projected by the optical system. The exposure apparatus according to any one of 12 above.   The exposure apparatus according to claim 10, wherein the pattern includes a contact hole pattern.   The exposure apparatus according to claim 10, wherein the object is subjected to multiple exposure including the first and second exposures.   The exposure apparatus according to any one of claims 10 to 16, wherein the same photosensitive layer on the object is exposed with the pattern in the first exposure and the second exposure.

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