JP2001250768A - Projection aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection aligner for suppressing the risk of defocusing a pattern image by trimming while excluding the influence of the surface state of a substrate. SOLUTION: The step on a wafer W is detected in advance, and an approximation surface APF that is approximated to the surface of the wafer W is obtained. While detection points AFij ' and AFij" that are located at positions being greatly collapsed or projecting from the approximation plane APF are eliminated, a plurality of detection points AFij near the approximation surface APF are selected, the position in the direction of the light axis of the surface of the wafer W is detected based on the position information, and the approximation plane APF of the wafer W is trimmed to the image surface of a projection optical system based on the detection result.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus used in a lithography process for manufacturing a micro device such as a semiconductor device, a liquid crystal display device, an image pickup device (such as a CCD) and a thin film magnetic head. .

[0002]

2. Description of the Related Art In an exposure apparatus of this type, an image of a circuit pattern on a mask (reticle, photomask, etc.) is applied to a photosensitive material (photoresist, etc.) via a projection optical system by illumination from an illumination optical system. It is projected and transferred onto a substrate (wafer, glass plate, etc.) that has been set. The photosensitive substrate is held on a substrate stage so as to intersect with the optical axis of the projection optical system, and an exposure surface of the substrate is adjusted to a predetermined alignment surface by a focusing mechanism.

As such a focusing mechanism, for example, the following multipoint oblique incidence type focus detection system is known. That is, in this conventional configuration, a pinhole image is projected onto each of a plurality of (for example, five) detection points in a shot area on a substrate by an oblique incidence method without passing through a projection optical system. Each reflection image of the pinhole is converted to a two-dimensional position sensor (C
CD, etc.) and detects how much the exposure surface of the substrate as a whole is in the projection optical axis direction from a virtually set reference plane. Then, from the detection results, an average plane of the plurality of detection points is obtained by least squares approximation or the like, and the average plane is adjusted to the image plane of the projection optical system. Such a conventional configuration is generally called an “oblique incidence type multi-point AF system”, and can perform focus detection and tilt detection with high accuracy.

In this type of focusing mechanism, when aligning a chipped exposure area in which a part of the peripheral portion of the substrate is missing, any one of the plurality of detection points is detected by the photosensitive substrate. May deviate from the focusable area corresponding to. In such a case, for example, the substrate stage is driven to change the correspondence between the substrate and the projection visual field of the projection optical system, for example, by one shot. Then, by making all the detection points enter the focusable area corresponding to the photosensitive substrate,
The above matching operation is performed (first conventional method). Alternatively, for example, the matching operation is performed using only the output of the sensor in the focusable area without using the output from the sensor corresponding to the missing exposure area (second conventional method).

[0005]

However, in the conventional focusing mechanism, when the surface of the substrate is adjusted to the image plane of the projection optical system, the surface state of the substrate to be exposed, for example, step information is not known. Not considered. Here, for example, the peripheral portion of the substrate may be warped, or a large convex portion may be formed on the surface of the substrate. In this state, if the sensor corresponds to a warped portion or a large convex portion on the substrate surface, the fitting surface is greatly inclined from the average surface of the detection points due to the influence of the warp or the convex portion, The offset may be large with respect to the average plane. Then, there has been a problem that the fitting surface may deviate greatly from the average surface, and the image of the circuit pattern may be transferred onto the substrate in a defocused state.

In the first conventional method, the shift focus operation is performed such that all the detection points enter the focusable area by moving the substrate stage during the alignment operation of the missing exposure area. Further, in the second conventional method, the alignment operation is performed using only the output of the sensor in the focusable area. In any of the first and second conventional methods, the state of the surface of the substrate to be exposed is not considered. For this reason, if the sensor in the focusable area corresponds to a warped portion or a large convex portion on the substrate surface, there is a problem that the image of the circuit pattern may be transferred onto the substrate in a defocused state. Was.

The present invention has been made by paying attention to such problems existing in the prior art. An object of the present invention is to provide an exposure apparatus that can perform a matching operation with almost no influence of the surface state of a substrate and can suppress a possibility that an image of a circuit pattern is transferred in a defocused state. .

[0008]

According to a first aspect of the present invention, an image of a predetermined pattern formed on a mask is projected by a projection optical system through a projection optical system. The projection optical system is configured to project and transfer onto a substrate mounted on a substrate stage that is two-dimensionally movable in a plane intersecting the optical axis of the system, and a plurality of projections are set at predetermined positions within a projection field of view of the projection optical system. A detection point, an optical axis direction position detecting means for detecting position information of a surface of the substrate in an optical axis direction of the projection optical system at the detection point, and an optical axis direction of the substrate at at least a part of the detection points Focusing means for adjusting an approximate plane approximating the surface of the substrate to the image plane of the projection optical system based on the position, wherein the focusing means performs the approximation based on a surface state of the substrate. Detect plane Approximation plane detection means, and the detection points used to detect the position of the surface of the substrate in the optical axis direction when the approximation plane is adjusted to the image plane, by using the approximation plane and each of the detection points. A detection point selecting means for selecting according to the positional relationship in the optical axis direction.

According to the first aspect of the invention, the surface state of the substrate is detected in advance, and an approximate plane approximating the surface of the substrate is obtained. Then, according to the positional relationship in the optical axis direction between the approximate plane and a plurality of detection points set at predetermined positions, an actual detection point used to detect the position of the substrate surface in the optical axis direction is selected. Is done. For this reason, when there is a large convex portion or the like on the surface of the substrate, it is almost influenced by the surface state of the substrate by using position information of a plurality of detection points selected avoiding the position of the convex portion. Without this, the position of the surface of the substrate in the optical axis direction can be detected. Therefore, the approximate plane of the substrate can be more accurately aligned with the image plane of the projection optical system.

According to a second aspect of the present invention, in the first aspect of the present invention, the optical axis direction position detecting means constitutes a part of the approximate plane detecting means. is there.

According to the second aspect of the present invention, it is not necessary to separately provide the optical axis direction position detecting means and the approximate plane detecting means, and the configuration can be simplified. According to a third aspect of the present invention, in the first or second aspect of the invention, the approximate plane detecting means is configured to detect at least a part of the plurality of exposure regions partitioned on the substrate. The method is characterized in that the approximate plane is detected based on a surface state.

According to the third aspect of the present invention, an approximate surface of the substrate can be easily and quickly detected by detecting a surface state of at least a part of the plurality of exposure regions defined on the substrate. Can be sought.

According to a fourth aspect of the present invention, in the third aspect of the present invention, the approximate plane detecting means adjusts the position of the entire substrate with respect to the projection optical system. At least a part of the region is used for detecting the approximate plane.

According to the present invention, when adjusting the position of the entire substrate with respect to the projection optical system by using at least a part of the exposure area on the substrate, the part of the exposure area is used. As a result, the approximate plane of the substrate can be easily and quickly detected. In addition, the throughput of the substrate exposure operation can be kept high.

According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, at the time of the aligning operation of the focusing means, the detecting point selecting means is used. The image processing apparatus further includes a correction unit configured to correct a deviation between a position of the selected detection point in the optical axis direction and the approximate plane.

According to the fifth aspect of the present invention, a more accurate alignment operation can be performed by correcting the deviation between the position of the selected detection point in the optical axis direction and the approximate plane of the substrate.

According to a sixth aspect of the present invention, in the first aspect of the present invention, the detection point selection means is detected by the optical axis direction position detection means. The detection point whose optical axis direction position exceeds a predetermined range is invalidated.

According to the present invention, when an uneven portion exceeding a predetermined range exists on the surface of the substrate, the detection point corresponding to the uneven portion is invalidated. Therefore, the aligning operation can be performed more accurately without being substantially affected by the position information of the uneven portion.

According to a seventh aspect of the present invention, in the sixth aspect of the present invention, when the detection point is invalidated at the time of selecting the detection point, the detection point selection means detects the detection point. It is characterized in that a detection point different from the point is selected again.

According to the present invention, when there is an invalidated detection point, for example, a detection point near the invalid detection point is selected again. Then, the alignment operation can be performed more accurately by using a plurality of predetermined detection points.

According to an eighth aspect of the present invention, in the invention of the sixth or seventh aspect, the detection point selecting means adjusts a missing exposure area in which a part of a peripheral portion of the substrate is missing. In the embedding operation, a detection point off the substrate is invalidated.

According to the eighth aspect of the present invention, a detection point off the substrate is invalidated during the aligning operation of the chipped exposure region in which a part of the peripheral edge of the substrate is missing. Then, the alignment operation can be performed accurately without being substantially affected by the position information of the uneven portion on the substrate surface and the position information of the chipped exposure region.

According to a ninth aspect of the present invention, in accordance with the seventh or eighth aspect of the present invention, when the detection point is invalidated by the detection point selection means, Driving a substrate stage to change the correspondence relationship between the substrate and the projection field of view of the projection optical system, and the detection point selection means is provided at a position corresponding to the projection field of view of the projection optical system on the changed substrate. It is characterized in that a detection point is selected again.

According to the ninth aspect of the present invention, when there is a detection point to be invalidated, the substrate stage is driven to change the correspondence between the substrate and the projection visual field of the projection optical system. Then, the detection point is selected again at a position corresponding to the projection visual field of the projection optical system on the substrate after the change. Therefore, the matching operation can be performed more accurately by using a plurality of predetermined detection points.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment in which the present invention is embodied in a step-and-repeat batch exposure apparatus will be described below with reference to FIGS. I do.

As shown in FIG. 1, an exposure apparatus 21 includes an illumination optical system 22, a reticle stage 23 for holding a reticle R as a mask, a projection optical system 24, and a wafer as a substrate stage for holding a wafer W as a substrate. Stage 2
5. The oblique incidence type focusing mechanism 26 which forms the focusing means, the optical axis direction position detecting means and the approximate plane detecting means, and the main control system 27 which constitutes the detecting point selecting means and the correcting means. .

The illumination optical system 22 includes a high-pressure mercury lamp,
rF excimer laser light source, ArF excimer laser light source,
Exposure light EL is incident from a light source 30, such as an F2 laser light source, a light source that oscillates a harmonic of a fiber laser such as a metal vapor laser or a YAG laser, or the like. The illumination optical system 22 includes various lens systems such as a relay lens (not shown), a fly-eye lens (or a lot integrator), and a condenser lens, and a blind disposed at a position conjugate with the aperture stop and the pattern surface of the reticle R. It is comprised including.

The exposure light EL is adjusted so as to uniformly illuminate the circuit pattern formed on the pattern surface of the reticle R by passing through the illumination optical system 22. In this case, while the reticle R and the wafer W are stationary, the image of the circuit pattern on the reticle R is collectively exposed to a shot area SAij as a predetermined exposure area on the exposure surface Wf of the wafer W shown in FIG. The illumination area of the exposure light EL is shaped into a rectangular shape so that the transfer exposure is performed.

The reticle stage 23 is arranged below the illumination optical system 22 such that the reticle mounting surface is orthogonal to the optical axis direction of the projection optical system 24.
On this reticle stage 23, a reticle minute drive stage 33 is mounted on a reticle support table 32, and on this reticle minute drive stage 33, a reticle holder 34 forming the reticle mounting surface is mounted. The reticle holder 34 is provided with a vacuum chuck, and the reticle R is held by the vacuum chuck. The reticle micro-drive stage 33 is located within a plane perpendicular to the optical axis of the projection optical system 24 and is parallel to the plane of FIG.
The position of the reticle R by a very small amount in the direction, the Y direction perpendicular to the plane of FIG. 1, and the rotation direction (θ direction) about the axis parallel to the optical axis of the projection optical system 24, respectively, with high accuracy. Control is performed.

The projection optical system 24 includes a plurality of lenses (not shown) and the like. When the exposure light EL passes through the projection optical system 24, its cross-sectional shape is determined by the size of the illumination area. The reduction ratio is reduced to 1 / n (n is a positive integer). Then, in a state where the circuit pattern on the reticle R is reduced at a predetermined reduction magnification, an exposure surface Wf of the wafer W held on the wafer stage 25 so as to intersect the optical axis of the projection optical system 24 is formed. It is designed to be projected and transferred.

The wafer stage 25 is arranged below the projection optical system 24 such that the wafer mounting surface intersects the optical axis direction of the projection optical system 24. A wafer Y drive stage 40 that can be driven in the Y direction is mounted on the wafer support table 39 of the wafer stage 25, and a wafer X drive stage 41 that can be driven in the X direction is mounted on the wafer Y drive stage 40. Is placed. Also,
On the wafer X drive stage 41, there is provided a Z leveling stage 42 whose upper surface can be slightly tilted with respect to an XY plane orthogonal to the optical axis of the projection optical system 24 and can be finely driven in the Z direction. . And this Z
The wafer W is held on the leveling stage 42 by vacuum suction.

On the Z leveling stage 42, X
L-shaped movable mirror 43 extending along the Y direction and the Y direction
Has been fixed. The pair of interferometers 44 has its movable mirror 4
3 is arranged so as to face the outer side surface. And
The positions of the Z leveling stage 42 in the X, Y, and θ directions are constantly monitored by these interferometers 44, and the position information S 1 obtained by these interferometers 44 is supplied to the main control system 27.

As shown in FIG. 1, the focusing mechanism 26 receives illumination light, which is different from the exposure light EL and does not expose the photoresist on the wafer W, from an illumination light source (not shown) via an optical fiber bundle 47. You are being led. The illumination light emitted from the optical fiber bundle 47 passes through the condenser lens 48,
A large number of slit openings 49-ij (i = 1 to 7, j = 1 to
7, see FIG. 4).

The illumination light transmitted through the pattern forming plate 49 is projected on an exposure surface Wf of the wafer W through a lens 50, a mirror 51, and an irradiation objective lens 52. This allows
An image of the pattern on the pattern forming plate 49 is projected and formed on the exposure surface Wf obliquely with respect to the optical axis of the projection optical system 24. The illumination light reflected on the exposure surface Wf of the wafer W is re-projected on a light receiving surface of a light receiver 56 via a condensing objective lens 53, a rotation direction diaphragm 54, and an imaging lens 55. Thereby, the image of the pattern on the pattern forming plate 49 is re-imaged on the light receiving surface of the light receiver 56.

The vibrating plate 54 is provided with a vibrating device 57.
And is oscillated under the control of the main control system 27 as described later. A large number of light receiving sensors 56-ij (i = 1 to 7, j = 1 to 7,
FIG. 5), and the light receiving sensors 56
The detection signal from −ij is supplied to the signal processing device 58.
The signal processing device 58 performs synchronous detection of the detection signal from each of the light receiving sensors 56-ij with a drive signal of the vibration device 57,
Many focus signals can be obtained. The signal processing device 58 supplies a large number of focus signals to the main control system 27.

As shown in FIG. 1, a reference mark plate 61 having a reticle alignment reference mark is fixed near the wafer W on the Z leveling stage 42. Above the reticle R, a reticle alignment microscope 62 for simultaneously observing the reference mark on the reference mark plate 61 and the measurement mark on the reticle R is provided. Then, the position of the reticle R on the reticle minute drive stage 33 is finely adjusted based on the relative position of the measurement mark with respect to the reference mark. As a result, the pattern on the reticle R is arranged at a predetermined position, and the alignment of the pattern is accurately performed.

On the side of the projection optical system 24, a wafer W
An off-axis type wafer alignment microscope 63 for detecting an alignment mark formed near each shot area SAij is provided. In this case, the distance between the detection center of the wafer alignment microscope 63 and the center of the projection area of the reticle R, that is, the so-called baseline amount is determined in advance. Then, the position of the wafer W on the Z leveling stage is adjusted based on the baseline amount and the position information of the alignment mark detected by the wafer alignment microscope 63. Thereby, the wafer W
Each of the upper shot areas is arranged at a predetermined position, and alignment of the shot areas is performed accurately.

As described above, the main control system 27 performs the positioning operation of the reticle minute drive stage 33 of the reticle stage 23 and the respective stages 40 to 42 of the wafer stage 25, the synchronous exposure operation of the reticle R and the wafer W, and the The operation of the entire exposure apparatus 21 is controlled, including the focusing operation of the focusing mechanism 26 and the like.

Next, the focusing operation of the focusing mechanism 26 will be described in more detail. As shown in FIG. 4, in the pattern forming plate 49, seven slit-like openings 49-11 to 49-17 are formed in the first row, and also in the second to seventh rows. Seven openings 49-21 to 49-77 are formed. That is, a total of 49 slit-shaped openings 49-ij (i = 1 to 7, j =
1 to 7) are formed. The illumination light emitted from the optical fiber bundle 47 causes these openings 49 to be opened.
As shown in FIG. 3, the pattern image formed by −ij is projected obliquely on the exposure surface Wf of the wafer W with respect to the X direction and the Y direction.

In FIG. 3, the circuit pattern of the reticle R shown in FIG. 1 is exposed to the rectangular shot area SAij in the illumination visual field of the projection optical system 24 during the batch exposure. From this, the projected images on the exposure surface Wf of the wafer W are arranged in this shot area SAij in order from the top in the Y direction in FIG.
F11 to AF17, 7 detection points AF21 to A in the second row
F27, detection points AF31 to AF37 in the third row, detection points AF41 to AF47 in the fourth row, detection points AF51 to AF in the fifth row
The AF 57, the detection points AF61 to AF67 in the sixth row, and the detection points AF71 to AF77 in the seventh row are all projected with all the 49 images corresponding to the apertures 49-ij, respectively.

As shown in FIG. 5, seven light receiving sensors 56-11 to 56-
17 are arranged, and seven light receiving sensors 56-21 to 56-77 are also arranged in the second to fifth columns. That is, the light receiver 56 includes 49 light receiving sensors 56 in total.
−ij (i = 1 to 7, j = 1 to 7) are arranged, and a slit-shaped diaphragm (not shown) is arranged on each light receiving sensor 56-ij. Then, each of these light receiving sensors 56
The image of the slit-shaped opening pattern projected on each detection point AFij in FIG. 3 is re-imaged on −ij.

Here, the rotational direction vibration plate 54 shown in FIG.
When the light reflected from the exposure surface Wf is re-imaged on the light receiver 56, the image is rotated and vibrated so as to oscillate the position of each image in the short direction of the aperture width of the stop. The detection signals detected by the respective light receiving sensors 56-ij are output to a signal processing device 58.
Supplied to The signal processing device 58 performs synchronous detection of each detection signal with a signal of the rotational vibration frequency,
For each of the detection points AFij on the wafer W, a position signal corresponding to a position in a direction parallel to the optical axis of the projection optical system 24 is generated and supplied to the main control system 27.

The main control system 27 controls the wafer alignment microscope 6 before projecting and transferring the circuit pattern on the reticle R to each shot area SAij of the wafer W.
In step 3, the position of the entire wafer W with respect to the projection optical system 24 is detected using a part of the plurality of shot areas SAij on the wafer W. Then, based on the detection result, the respective stages 40 to 42 of the wafer stage 25 are driven,
Wafer alignment for adjusting the position of the entire wafer W is performed.

At the time of this wafer alignment, the main control system 27 causes the focusing mechanism 26 to detect the surface state of the wafer W using a part of the shot area SAij. In this case, as shown in FIG. 3, the wafer W is detected at all 49 detection points AFij located in the shot area SAij.
Are detected by the light receiving sensors 56-ij, and their position signals are supplied from the signal processing device 58 to the main control system 27. Then, the main control system 27 determines each detection point AFij
, An approximate plane APF approximating the exposure surface Wf of the wafer W is calculated as shown in FIG.

On the other hand, in this embodiment, when collective exposure is performed in each shot area SAij partitioned on the wafer W, as shown in FIG. 2, a part of the 49 detection points AFij It is set as a detection point for detecting a position (hereinafter, referred to as a “sample detection point”). For example, the first and seventh detection points AF11 and AF17 in the first column, the second and sixth detection points AF22 and AF26 in the second column, and the fourth column Among the detection points in the sixth column, the second and sixth detection points AF62 and AF66 in the sixth column, and the first and seventh detection points AF71 in the seventh column. ,
Nine points of AF77 are set as sample points.

Here, the main control system 27 includes an approximate plane A
PF is compared with the optical axis direction position detected at each sample detection point AFij, and when the position exceeds a predetermined range, the sample detection point AFij is invalidated,
A nearby detection point different from the detection point is used as a sample point AF.
Reselect as ij. That is, as shown in FIG. 6, there is a large concave or convex portion on the exposure surface Wf of the wafer W, and the sample detection point AFij 'corresponding to the concave portion and the sample detection point AFij''corresponding to the convex portion are invalid. And a sample detection point AFij corresponding to a position avoiding the concave portion or the convex portion is selected. If there is a shift between the position of the selected sample detection point AFij in the optical axis direction and the approximate plane APF, the shift is corrected.

Further, the main control system 27 adjusts the approximate plane APF of the wafer W to the image plane of the projection optical system 24 in the missing shot area SAij where a part of the peripheral portion of the wafer W is missing. The sample detection point AFij off the wafer W is invalidated, and a nearby detection point is selected again as the sample point AFij. For example, as shown in FIG. 7, when one sample detection point AF11 is off the wafer W, the detection point AF11 is invalidated, and the nearby detection point AF13 is reselected as a sample point. It is.

The shot area SAij to be detected is
Can be determined based on the position information of the wafer X drive stage 41 and the wafer Y drive stage 40 in a state where the shot area SAij is arranged in the projection area of the projection optical system 24. . Whether or not each detection point AFij exists on the wafer W can be determined based on the position information of each of the stages 41 and 40 and the arrangement of each detection point AFij.

Then, as shown in FIG. 2, in each shot area SAij on the wafer W, the approximate plane A of the wafer W
When adjusting the PF to the image plane of the projection optical system 24, the exposure surface Wf of the wafer W at the selected nine sample detection points AFij by the corresponding light receiving sensors 56-ij.
Are detected in the optical axis direction, and their detection signals are supplied to the signal processing device 58. The signal processing device 58 generates a focus signal corresponding to a position (focus position) in a direction parallel to the optical axis of the projection optical system 24 based on the detection signal from each light receiving sensor 56-ij, and System 27
To supply.

The main control system 27 calculates the inclination angle (leveling angle) of the exposure surface Wf of the wafer W and the average focus position (position of the alignment surface) based on the focus signal. Then, based on the leveling angle and the position of the fitting surface, the Z leveling stage 42 is driven to adjust the inclination of the exposure surface Wf of the wafer W and the height in a direction parallel to the optical axis of the projection optical system 24. . With this adjustment,
Approximate plane AP of wafer W with respect to the image plane of projection optical system 24
The adjustment of F is performed.

Next, the control operation of the Z leveling stage 42 will be described. As shown in FIG. 2, the upper surface member of the Z leveling stage 42 is supported on the lower surface member via three supporting points 66 to 68. Each fulcrum 66-68
Are independent of the focus direction (projection optical system 24
(That is, in the direction parallel to the optical axis, that is, the Z direction). Then, by adjusting the amount of expansion and contraction of each of the fulcrums 66 to 68 via the driving units 69 to 71 under the control of the main control system 27, the position of the exposure surface Wf of the wafer W on the Z leveling stage 42 is adjusted. , X and Y directions are set to desired values. In the vicinity of the fulcrums 66 to 68, height sensors 72 to 74 capable of detecting the displacement amounts of the fulcrums 66 to 68 in the focus direction with a resolution of, for example, about 0.01 μm are attached. As a positioning mechanism in the focus direction, for example, a high-precision mechanism having a longer stroke may be separately provided.

When the positions where the fulcrums 66 to 68 are located are the driving points TL1, TL2 and TL3, respectively, the two driving points TL1 and TL2 are arranged on a straight line parallel to the Y axis. The drive point TL3 is arranged on a perpendicular bisector to a line connecting the two drive points TL1 and TL2.

Then, in the state where the leveling control of the Z leveling stage 42 is completed as described above, the focus control of the stage 42, that is, the operation of aligning the approximate plane APF of the wafer W with the image plane of the projection optical system 24 is performed. Will be In this case, the setting of the alignment position is performed by displacing the three fulcrums 66 to 68 by the same amount.

Therefore, according to the present embodiment, the following effects can be obtained. (A) In the exposure apparatus 21 of this embodiment, the surface condition of the wafer W is determined in advance by using the light receiving sensors 56-ij (all the sensors 56-11 to 56-77) of the light receiver 56 of the focusing mechanism 26. An approximate plane APF that is detected and approximates the surface of the wafer W is obtained. Then, the approximate plane APF and a plurality of detection points AFij (eg, AF
11, AF17, AF22, AF26, AF44, AF
The actual detection point AFij used for detecting the position of the surface of the wafer W in the optical axis direction during the aligning operation is determined according to the positional relationship in the optical axis direction with nine points (62 points, AF66, AF71, and AF77). Selected.

That is, at the time of the aligning operation when there is a large uneven portion on the exposure surface Wf of the wafer W, or the chipped shot area SA in which a part of the peripheral portion of the wafer W is omitted.
At the time of the ij matching operation, a detection point AFij near the detection point AFij corresponding to the uneven portion or the missing shot area SAij is selected. Then, at these selected detection points AFij, the position of the surface of the wafer W in the optical axis direction is detected using the corresponding plurality of light receiving sensors 56-ij. The approximate plane APF of the wafer W is adjusted to the image plane of the projection optical system 24 based on the detection result.

Therefore, it is possible to select a plurality of detection points AFij at the time of the aligning operation while avoiding the large uneven portion on the surface of the wafer W and the missing shot area SAij. Then, at those detection points AFij, the position of the surface of the wafer W in the optical axis direction can be detected almost without being affected by the surface state of the wafer W. Therefore, based on the position detection results of these detection points AFil, the projection optical system 2
4 can be more accurately aligned with the approximate plane APF of the wafer W. And reticle R
The possibility that the upper circuit pattern is projected and transferred onto the wafer W in a defocused state can be suppressed.

(B) In the exposure apparatus 21 of this embodiment, the step mechanism information of the wafer W used when detecting the approximate plane of the wafer W is obtained by the focusing mechanism 26. Therefore, it is not necessary to separately provide a sensor for detecting the step information of the wafer W and a sensor for the focusing mechanism 26, and the configuration can be simplified.

(C) In the exposure apparatus 21 of this embodiment, the step information of the wafer W and the approximate plane APF are detected using a part of the shot area SAij used at the time of wafer alignment. . Therefore, the step information and the approximate plane can be detected together with the wafer alignment, and there is no need to move the wafer stage 25 largely. Therefore, the approximate plane A of the wafer W
PF can be detected easily and quickly, and the throughput of the exposure operation of the wafer W can be maintained at a high level.

(D) In the exposure apparatus 21 of this embodiment, when there is a deviation between the position of the selected detection point AFij in the optical axis direction and the approximate plane APF during the aligning operation of the focusing mechanism 26, The deviation is corrected. Therefore, the position information of the detected detection point AFij is
For example, when an offset occurs, the position information is corrected, and a more accurate alignment operation can be performed.

(E) In the exposure apparatus 21 of this embodiment, when the position in the optical axis direction detected by the light receiving sensor 56-ij at the detection point AFij at a predetermined position exceeds a predetermined range,
The detection point AFij at the predetermined position is invalidated, and a nearby detection point AFij is selected again. For this reason, the sample detection points AFij ′ and AFij ″ that largely depress or protrude from the approximate plane APF on the surface of the wafer W are invalidated, and the sample detection points AFij close to the approximate plane APF are selected. Accordingly, even when the surface of the wafer W has an uneven portion exceeding a predetermined range, the aligning operation can be performed more accurately without being substantially affected by the position information of the uneven portion.

(F) In the exposure apparatus 21 of this embodiment, during the alignment operation of the missing shot area SAij in which a part of the peripheral portion of the wafer W is missing, the detection point AFij that is off the wafer W is invalidated. Then, a nearby detection point AFij is selected again. For this reason,
The aligning operation can be performed more accurately without being substantially affected by the position information of the detection point AFij deviating from the wafer W.

(Second Embodiment) Next, a second embodiment of the present invention will be described focusing on parts different from the first embodiment.

In the second embodiment, as shown in FIG. 8, during the alignment operation of the missing shot area SAij in which a part of the peripheral edge of the wafer W is missing, the wafer W
When the detection point AFij deviating from above is invalidated, the wafer stage 25 is driven and the wafer W and the projection optical system 24 are moved.
Is changed by one shot area SAij. Then, the shot area SA after this change
In ij, the detection point AFij is selected again.

That is, as shown in FIG. 8, when the missing shot area SAij is adjusted, the detection point AF1
1 is off the wafer W, the shot area SA
ij is shifted by one shot in the X direction. In this state,
Complete shot area S adjacent to the missing shot area
At Aij ', nine detection points AFij are selected again. In this state, the wafer W is detected at each detection point AFij.
The position of the exposure plane Wf in the optical axis direction is detected, and the approximate plane APF of the wafer W is aligned with the image plane of the projection optical system 24 based on the position information.

Therefore, according to the present embodiment, in addition to the effects (a) to (e) of the first embodiment,
The following effects can be obtained. (G) In the exposure apparatus 21 of this embodiment, when there is a detection point AFij off the wafer W during the alignment operation of the missing shot area SAij on the wafer W, the shot area SAij is changed by one shot. After that, the detection point AFij is selected again. Therefore, the aligning operation can be performed more accurately without being affected by the position information of the missing shot area SAij.

(Third Embodiment) Next, a third embodiment of the present invention will be described focusing on parts different from the first embodiment.

In the third embodiment, as shown in FIG. 9, in the operation of aligning the missing shot area SAij on the wafer W, the detection point A off the wafer W is set.
When Fij is invalidated, the wafer stage 25 is driven, and the correspondence between the wafer W and the projection field of the projection optical system 24 is changed until the detection point AFij reaches a focusable area on the wafer W. . Then, the detection point AFij is reselected in the shot area SAij after this change.

That is, as shown in FIG. 9, the detecting point AF1
1 is off the wafer W, the detection point AF1
The shot area SAij is shifted substantially in the X direction by, for example, a half shot until the position 1 corresponds to the exposure surface Wf of the wafer W, and the nine detection points AFij are selected again. At this time, the nine detection points AFij are the detection points AFi in which the approximate plane APF is greatly depressed or protruded as shown in FIG.
j ′ and AFij ″ are selected to be avoided.
In this state, the position of the exposure surface Wf of the wafer W in the optical axis direction is detected at each detection point AFij, and the approximate plane APF of the wafer W is aligned with the image plane of the projection optical system 24 based on the position information. Is included.

Therefore, according to the present embodiment, in addition to the effects (a) to (e) of the first embodiment,
The following effects can be obtained. (H) In the exposure apparatus 21 of this embodiment, when the detection point AFij that is off the wafer W exists during the alignment operation of the missing shot area SAij on the wafer W, the position at which the detection point AFij reaches the focusable area. Up to this point, after the shot area SAij is changed, the detection point AFij is selected again. Therefore, the matching operation can be performed more accurately without being affected by the position information of the missing shot area SAij.

Also, the shift distance of the shot area SAij is smaller than in the case of the second embodiment. For this reason, the time required for the shift operation can be shortened, and the throughput of the exposure operation of the wafer W can be further maintained. In addition, each wafer drive stage 4
The influence of the movement of 0 and 41 can be reduced, and a decrease in exposure accuracy can be suppressed.

(Modification) The embodiment of the present invention may be modified as follows. In each of the above-described embodiments, a sensor for detecting the stepped state of the wafer W is provided separately from the focusing mechanism 26, and these sensors are separately used to detect the stepped state of the wafer W and the projection optical system 24. The operation of aligning the surface of the wafer W with the image plane may be performed.

In each of the above embodiments, the step state and the approximation of the wafer W are obtained in one or a plurality of shot areas SAij near the center of the wafer W without using a part of the shot areas SAij used at the time of wafer alignment. You may comprise so that plane APF may be detected.

Even in such a case, substantially the same effects as those in the above embodiments can be obtained. The exposure apparatus of the present invention is not limited to an exposure apparatus for manufacturing a semiconductor device, nor is it limited to a reduction exposure type or a batch exposure type exposure apparatus. That is,
This exposure apparatus includes an exposure apparatus such as a liquid crystal display element, an imaging element, and a thin-film magnetic head. It also includes a 1: 1 exposure type exposure apparatus and a step-and-scan type scanning exposure type exposure apparatus.

[0074]

As described in detail above, according to the first aspect of the present invention, the aligning operation can be performed accurately without being substantially affected by the surface condition of the substrate. Therefore, the possibility that the circuit pattern is projected and transferred on the substrate in a defocused state can be suppressed.

According to the second aspect of the present invention, in addition to the effects of the first aspect, it is not necessary to separately provide the optical axis direction position detecting means and the approximate plane detecting means. The configuration can be simplified.

According to the third aspect of the present invention, in addition to the effects of the first or second aspect,
The approximate surface of the substrate can be easily and quickly determined.
According to the invention described in claim 4 of the present application, in addition to the effect of the invention described in claim 3, it is possible to detect an approximate plane of the substrate more easily and quickly, and it is possible to perform an exposure operation on the substrate. High throughput can be maintained.

According to the invention described in claim 5 of the present application, in addition to the effects of the invention described in any one of claims 1 to 4, a more accurate fitting operation can be performed. .

According to the invention described in claim 6 of the present application, in addition to the effects of the invention described in any one of claims 1 to 5, the influence of the positional information of the concave and convex portions on the substrate surface is also reduced. The alignment operation can be performed more accurately with almost no reception.

According to the seventh aspect of the present invention, in addition to the effect of the sixth aspect of the present invention, it is possible to secure a predetermined plurality of detection points and more accurately perform the alignment operation. it can.

According to the invention described in claim 8 of the present application, in addition to the effects of the invention described in claim 6 or 7,
The alignment operation can be performed more accurately without being affected by the position information of the missing exposure area.

According to the ninth aspect of the present invention, in addition to the effects of the seventh or eighth aspect,
By ensuring a plurality of predetermined detection points, the alignment operation can be performed more accurately.

[Brief description of the drawings]

FIG. 1 is a configuration diagram mainly showing a focusing mechanism of an exposure apparatus according to a first embodiment.

FIG. 2 is a configuration diagram showing a Z leveling stage and a control configuration thereof.

FIG. 3 is a plan view showing an image of an aperture pattern projected on an exposure area by a projection optical system.

FIG. 4 is an explanatory diagram showing an opening pattern on a pattern forming plate of the focusing mechanism.

FIG. 5 is an explanatory diagram showing an array of light receiving sensors of the light receiving device.

FIG. 6 is an explanatory diagram showing an operation of selecting a detection point according to a surface state of a wafer at the time of an aligning operation.

FIG. 7 is an explanatory diagram showing an operation of selecting a detection point at the time of aligning a missing exposure area.

FIG. 8 is an explanatory diagram showing an operation of selecting a detection point during a matching operation of a missing exposure area according to the second embodiment.

FIG. 9 is an explanatory diagram showing a selection operation of a detection point during a matching operation of a missing exposure area according to the third embodiment.

[Explanation of symbols]

21: Exposure device, 24: Projection optical system, 25: Wafer stage as substrate stage, 26: Focusing mechanism that constitutes focusing means, optical axis direction position detecting means and approximate plane detecting means, 27: Detection point selecting means And R, a reticle as a mask, W, a wafer as a substrate, Wf, an exposure surface forming the surface of the substrate, SAij, a shot area as an exposure area, AFij, a detection point, APF,
Approximate plane.

Claims (9)

[Claims] An image of a predetermined pattern formed on a mask is placed on a substrate stage that can move two-dimensionally in a plane intersecting an optical axis of the projection optical system via a projection optical system. A plurality of detection points set at predetermined positions in a projection field of view of the projection optical system, and a surface of the substrate in the optical axis direction of the projection optical system at the detection points. Optical axis direction position detecting means for detecting the position information of the substrate, and an approximate plane approximating the surface of the substrate based on the position of the substrate in the optical axis direction at at least a part of the detection points on the image plane of the projection optical system. In an exposure apparatus including a focusing unit for focusing, the focusing unit includes an approximate plane detection unit that detects the approximate plane based on a surface state of the substrate, and adjusting the approximate plane to an image plane. The board A detection point selection unit that selects the detection point used for detecting the position of the surface in the optical axis direction according to a positional relationship between the approximate plane and each of the detection points in the optical axis direction. Exposure apparatus. 2. An exposure apparatus according to claim 1, wherein said optical axis direction position detecting means forms a part of said approximate plane detecting means. 3. The apparatus according to claim 1, wherein the approximate plane detecting means detects the approximate plane based on a surface state of at least a part of the plurality of exposure areas defined on the substrate. Alternatively, the exposure apparatus according to claim 2. 4. The approximate plane detecting means also uses at least a part of the exposure region used when adjusting the position of the entire substrate with respect to the projection optical system when detecting the approximate plane. 4. The exposure apparatus according to claim 3, wherein: 5. A correction means for correcting a deviation between the position of the detection point selected by the detection point selection means in the optical axis direction and the approximate plane when the focusing means performs the alignment operation. The exposure apparatus according to any one of claims 1 to 4, wherein 6. The apparatus according to claim 1, wherein said detection point selection means invalidates a detection point whose optical axis direction position detected by said optical axis direction position detection means exceeds a predetermined range.
The exposure apparatus according to claim 5. 7. The detection point selecting means, when selecting a detection point, if a certain detection point is invalidated, reselects a detection point different from the detection point. 3. The exposure apparatus according to claim 1. 8. The detecting point selecting means invalidates a detecting point off the substrate at the time of aligning a chipped exposure region in which a part of a peripheral portion of the substrate is missing. An exposure apparatus according to claim 6. 9. The focusing means drives the substrate stage to change the correspondence between the substrate and the projection visual field of the projection optical system when a detection point is invalidated by the detection point selection means. 9. The exposure apparatus according to claim 7, wherein the detection point selection unit reselects a detection point at a position corresponding to a projection visual field of the projection optical system on the changed substrate. apparatus.