JPH05102009A - Aligner - Google Patents

Abstract

PURPOSE:To correct the inclination of a photosensitive substrate with utmost efficiency and accurately according to the exposure region of a projection optical system, the surface state of the photosensitive substrate and the like when a pattern formed on a reticle is exposed on the photosensitive substrate via the projection optical system. CONSTITUTION:The title aligner is provided with the following: leveling detection optical systems 19 to 22 which measure the inclination of an exposure shot-position designated on the face to be exposed of a wafer 18; an input means 26 which sets a measurement prohibition region for which the actually measured value of the inclination on the face to be exposed of the wafer 18 is not used; and leveling mechanisms 23, 25 which correct the inclination of each exposure shot position on the face to be exposed according to the measured result by the leveling detection optical systems and the measurement prohibition region.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus such as a reduction projection type exposure apparatus for manufacturing integrated circuits, and more particularly to correcting a local inclination of a photosensitive substrate with respect to a projection image plane of a projection optical system for exposure. The present invention relates to an exposure apparatus having a leveling mechanism.

[0002]

2. Description of the Related Art Generally, a projection lens having a large numerical aperture (NA) is used in a reduction projection type exposure apparatus for manufacturing an integrated circuit for reducing and transferring a pattern on a reticle onto a wafer. Therefore, the depth of focus is very shallow. Therefore, the exposure area of the wafer is maintained exactly perpendicular to the optical axis of the projection lens, that is, the wafer surface and the projection image plane are kept strictly parallel, and the wafer is positioned in the optical axis direction by the autofocus mechanism. Need to do. However, since the flatness of the wafer is not always good, a leveling mechanism for locally correcting the inclination of the surface so that the surface to be exposed for each exposure shot is perpendicular to the optical axis of the projection lens. Are provided (see, for example, JP-A-58-113706).

In the conventional leveling mechanism, for example, a circular light beam having a low photosensitivity that is inscribed in a rectangular exposed pattern region on a wafer is obliquely irradiated onto the wafer, and reflected light of the light beam is focused by a focusing lens. The light is collected by the detector and guided to a detector composed of a four-divided light receiving element or the like. Then, the current inclination of the surface to be exposed is measured by the position of the center of gravity of the condensed light on the detector, and the inclination of the surface is corrected so that the inclination becomes a preset value within a predetermined tolerance. Is done. The inclination of the surface is corrected, for example, by supporting the wafer on a leveling stage at three points and adjusting the height of two points out of the three points. After that, the wafer is positioned in the optical axis direction of the projection lens by the autofocus mechanism if necessary.

In the conventional leveling mechanism, the tilt is generally adjusted so that the measured value of the tilt of the exposure target surface is returned to a predetermined value regardless of the exposure shot position in the wafer. In addition, since the peripheral portion of the wafer generally has a poor flatness, a measurement prohibited area should be set in the peripheral portion, and the measured value of the tilt should be used for the surface to be exposed in this area. Instead, a method is also used in which the inclination is considered to be, for example, a predetermined value and the adjustment is performed.

[0005]

However, even when such a measurement prohibited area is provided, the inclination of the exposure target surface is conventionally measured and corrected under a constant condition regardless of the state of the wafer. When the area with poor flatness in the peripheral portion of the wafer is enlarged, the inclination is measured in the area with poor flatness, and there is a possibility that the correction is performed based on the measured value of the inaccurate inclination. There was an inconvenience. As a result, the manufacturing yield of ICs and the like finally decreases.

As an example of such a region in which the flatness of the peripheral portion of the wafer is poor, it is set in order to suppress the generation of foreign matters due to the resist applied to the outer peripheral portion of the wafer,
There is a resist removal range at the peripheral portion of the wafer. That is, FIG.
As shown in (A), when the resist 2 is coated on the wafer 1, the resist 2 wraps around the outer peripheral portion 1 a of the wafer 1. Therefore, if exposed and developed in this state, foreign matters such as dust are generated due to the resist 2 on the outer peripheral portion 1a. Therefore, as shown in FIG. 5B, the region 1b within the range of the distance r from the outer peripheral portion of the wafer 2 is set as the resist removal range, and the resist in the resist removal range 1b is previously set by the peripheral edge exposure (and development). Remove it. However, if such exposure and development of the pattern are repeated by performing such removal, the resist removal area 1b will have a pattern of FIG.
As shown in (C), the inclined region 1c is formed via the step. The inclined region 1c may project onto the surface of the wafer 2.

A case where the inclination of the wafer 1 having the inclined region 1c as shown in FIG. 5C is measured will be described with reference to FIG. In FIG. 6, the exposure area of the wafer 1 by the projection lens 3 is a square area 4, and the exposure area 4 is located in the peripheral portion of the wafer 1. The laser beam emitted from the laser diode 5 as a point light source is collimated by the collimator lens 6 into a parallel light beam L1.
And the parallel light beam L1 is irradiated onto the circle 7 inscribed in the exposure area 4 on the wafer 1 obliquely with respect to the optical axis of the projection lens 3. Then, the reflected light from the circle 7 is condensed by the condenser lens 8 and irradiated onto the detector 9.

In the example of FIG. 6, the area 1 at the center of the wafer 1
If only the reflected light from d is used, the accurate tilt is measured. However, in reality, the reflected light from the inclined region 1c having a step is mixed, and the inclination obtained by processing the output signal of the detector 9 has a value different from the inclination of the region 1d. There is an inconvenience that accurate leveling cannot be performed. In this case, if the sloped area 1c due to the resist removal range is fixed, erroneous measurement can be prevented by designating the vicinity of the area 1c as the measurement prohibited area. However, since the resist removal range changes depending on the wafer and the process, erroneous measurement cannot be prevented even if a predetermined certain area is designated as the measurement prohibited area in advance.

Further, when a certain measurement prohibited area is set and the exposed area of the projection lens (the area corresponding to the exposure area 4 in FIG. 6) is enlarged, the exposure shot area A situation may occur in which the arrangement is changed and the tilt is measured in the state where a part of the measurement light beam is applied to the measurement prohibited area.

Further, conventionally, the exposure area required for the projection lens changes depending on, for example, the type of the pattern transferred from the reticle to the wafer, such as a memory or a central processing unit (CPU). The field of view to be illuminated by the reticle is limited by the illumination field diaphragm). Therefore, if the field of view is limited to a small value by the blinds, the exposure area on the wafer may deviate from the measurement prohibited area. However, even in such an exposure shot, the tilt measurement is uniformly prohibited, and accurate leveling cannot be performed. was there.

In view of the above, the present invention provides an apparatus for exposing a pattern formed on a reticle onto a photosensitive substrate via a projection optical system, depending on the exposure area of the projection optical system and the surface condition of the photosensitive substrate. It is an object of the present invention to enable the most efficient and accurate correction of the tilt of the photosensitive substrate.

[0012]

In an exposure apparatus according to the present invention, for example, as shown in FIG. 1, a pattern formed on a reticle (16) is projected onto a photosensitive substrate (18) via a projection optical system (17). In the exposure apparatus, the photosensitive substrate (1
8) Inclination measuring means (19 to 22) for measuring the inclination of the designated exposure shot position on the exposed surface, and the measurement limitation not using the measured value of the inclination on the exposed surface of the photosensitive substrate (18). A drive mechanism (23) for correcting the inclination of each exposure shot position on the exposed surface according to the measurement result of the input means (26) for setting the area and the inclination measurement means (19 to 22) and the measurement restriction area. , 25), and the drive mechanism (23, 25), at the exposure shot position in the measurement restricted area, measures the tilt at the exposure shot position near the exposure shot position and outside the measurement restricted area. Alternatively, the tilt is corrected according to a preset tilt.

Then, the input means (2
In 6), the measurement restriction area may be set based on information on the maximum exposure range of the projection optical system (17). . Also,
A blind (13) for limiting the illumination range is provided in the illumination optical system for illuminating the reticle (16), and the input means (16) limits the measurement based on the information on the illumination range limited by the blind (13). The area may be set.

Further, as the photosensitive substrate (18), a photosensitive substrate whose peripheral edge is exposed to remove the photosensitive material at the peripheral edge is used, and the input means (26) is a peripheral edge where the photosensitive material is removed. The measurement restriction area may be set based on the information of the section. Further, for example, as shown in FIG. 4, step measuring means (31 to 34) for measuring the step of the peripheral portion (30a) of the photosensitive substrate (30) is provided, and the input means (3).
In 5), the measurement restriction area may be set based on the measurement result of the step measuring means (31 to 34).

[0015]

According to the present invention, the measurement restriction region can be arbitrarily set by the input means (26) without using the measured value of the inclination of the photosensitive substrate (18) on the exposed surface. In order to correct the tilt accurately in a wider range, it is desirable to limit the measurement restriction area to the minimum necessary area. In the present invention, for example, by changing the measurement restriction area according to the exposure shot area of the projection optical system to be used and the arrangement state thereof, the measurement restriction area is changed to the photosensitive substrate (1
It is possible to limit to 6) the area where the surface accuracy is poor, and the inclination can be corrected accurately in a wider range. In this case, at the exposure shot position in the measurement restricted area, the tilt is corrected according to the accurate measurement result of the tilt close to the exposure shot position or a constant tilt which is empirically known in advance. Therefore, it is possible to accurately correct the inclination in the measurement restriction area.

Further, the measurement restricted area is defined by the projection optical system (1
When the information is set from the maximum exposure range of 7), even if the maximum exposure range changes, the measurement restriction area can be set to the narrowest range accordingly. Similarly, when the measurement restriction area is set based on the information of the illumination range restricted by the blind (13), even if the illumination range changes, the measurement restriction area can be set to the narrowest range accordingly. it can.

Similarly, when the measurement restriction area is set based on the information on the removal range of the photosensitive material of the photosensitive substrate (18), the measurement restriction area can be suppressed to the minimum necessary according to the removal range. it can. Further, when a step measuring means for measuring the step of the peripheral portion of the photosensitive substrate (30) is provided, for example, an area outside the step obtained by measuring with the step measuring means should be set as the measurement restriction area. Thus, the measurement restriction area can be set more accurately.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an exposure apparatus according to the present invention will be described below with reference to FIGS. FIG. 1 shows the overall configuration of the exposure apparatus of this example. In FIG. 1, 10 is a lamp house. The exposure light emitted from the light source in the lamp house 10 irradiates the blind 13 with a uniform intensity distribution via the fly-eye lens 11 and the condenser lens 12, and the exposure light whose unnecessary portion is blocked by the blind 13 is The reticle 16 is illuminated through the mirror 14 and the illumination lens 15. A pattern such as a circuit pattern to be transferred is formed on the reticle 16, and a reduced image of this pattern is formed on the wafer 18 by the projection lens 17.

A leveling detection optical system is arranged around the projection lens 17. To describe the leveling detection optical system, light emitted from a light source 19 such as a light emitting diode or a laser diode is converted into a parallel light flux L2 by a collimator lens 20, and the parallel light flux L2 is irradiated onto the wafer 18. The wavelength of the parallel light flux L2 is selected such that the resist coated on the wafer 18 has low photosensitivity. The parallel light flux L2 is obliquely incident on the optical axis 17a of the projection lens 17, and on the wafer 18, the outer shape of the parallel light flux L2 is a circle that is substantially inscribed in the exposure area of the projection lens 17. The reflected light from the wafer 18 of the parallel light flux L2 is divided into four by a condenser lens 21 or a position detection type light receiving element (two-dimensional position sensor).
It irradiates the detector 22 including The detector 22 outputs a detection signal S1 indicating the position of the center of gravity of the detection light.
Since the center of gravity of the detection light on the detector 22 changes according to the inclination of the surface of the wafer 18 irradiated with the parallel light flux L2, the inclination angle of the surface with respect to the optical axis 17a can be measured.

Although not shown, a focusing detection optical system for autofocus is arranged together with the leveling detection optical system. As a method of detecting focusing, 1 in the current exposure shot area on the wafer 18 is used.
There is a method of detecting the positions of points or multiple points in the optical axis 17a direction. This focusing detection optical system may share the lenses 20 and 21 of the leveling detection optical system, or may be provided independently.

23 is a leveling stage, 24 is XYZ
Showing the stage, the wafer 18 leveling stage 23
It is placed on top and the leveling stage 23 is fixed on the XYZ stage. The leveling stage 23 is, for example, 3
Two of the individual support points are moved up and down to level the exposure target surface of the wafer 18. Further, in the present embodiment, focusing on the exposure target surface on the wafer 18 is performed by the Z stage, so that the current exposure target surface of the wafer 18 coincides with the image plane of the projection lens 17. That is, the XY stage of the XYZ stage 24 causes the leveling stage 23 to perform parallel movement or minute rotation in a plane substantially perpendicular to the optical axis 17a of the projection lens 17, and to perform XYZ
The Z stage of the stages 24 performs focusing by moving the leveling stage 23 in the direction of the optical axis 17a.

Reference numeral 25 is a leveling processing system for controlling the operation of the leveling stage 23 using the drive signal DR1.
Indicates input means formed by a computer or the like, the leveling processing system 25 inputs the detection signal S1 of the detector 22, and the input means 26 outputs information IND such as the maximum exposure range of the projection lens 17 via the bus line 27. Supply. Reference numeral 28 denotes a control system that controls the operation of the entire apparatus. The control system 28 controls the operation of the XYZ stage 23 using the drive signal DR2, and at the same time, a position signal that indicates the position of the XYZ stage 23 (for coordinate measurement, for example). The coordinate value S3 measured by the laser interferometer of 3) is supplied to the input means 26.

The input means 26 obtains the measurement prohibited area on the wafer 18 from the input information IND, and when the exposure shot area of the wafer 18 is included in the measurement prohibited area, it is detected by the leveling processing system 25 using the control signal S2. The detection signal S1 obtained from the device 22 is ignored. Therefore, in the measurement prohibited area, the leveling processing system 25 uses, for example, an effective tilt angle one shot before as the tilt angle of the exposure shot area, or a predetermined constant tilt angle (for example, the value of the ideal plane is 0). The tilting angle of (3) is used to perform leveling of the leveling stage 23 so as to cancel the difference between this tilt angle and the target tilt angle. Further, in the measurement prohibited area, the XYZ stage 24 is moved by the control system 28 to irradiate the area near the measurement prohibited area on the wafer 18 where the measurement result is valid with the parallel light beam L2 for leveling. The tilt may be corrected by using the tilt angle as the tilt angle in the measurement prohibited area.

To explain the exposure operation of this example, first, assume that there is no resist removal range on the wafer 18.
Even in this case, in general, the vicinity of the edge portion of the outer periphery of the wafer 18 is often blunt. Therefore, when the tilt angle is measured including the reflected light from that portion and the leveling operation is performed based on this measurement result, the surface to be exposed (correctly, the portion that is not sag in this) is projected onto the projection lens 17 It is conceivable that the image plane deviates from the image plane. Therefore, first, when the exposure range of one shot by the projection lens 17 is a relatively small square area as shown in FIG. 2A, the information of the exposure range of that one shot is used as the input information IND and the input means of FIG. Then, the input means 26 designates a shaded area of 16 blocks including the edge portion of the wafer 18 in each exposure shot range as a measurement prohibited area.

In the area other than the measurement prohibited area, the XYZ stage 24 is moved by the drive signal DR2 from the control system 28 of FIG. 1 to set a predetermined exposure shot area of the wafer 18 under the projection lens 17 for focusing. Is done. After that, or at the same time as the focusing, the leveling processing system 25 drives the leveling stage 23 so that the tilt angle obtained from the detection signal S1 from the detector 22 becomes a predetermined angle, performs the leveling of the wafer 18, and performs the leveling. Pattern of the reticle 16 is
8 is transferred (exposed). After that, XYZ stage 2
By the stepping operation of 4, the next exposure shot area of the wafer 18 is set under the projection lens 17, and the leveling and the exposure are performed similarly.

However, as shown in FIG. 2A, when the exposure shot area of the wafer 18 is the exposure shot area PR1 in the measurement prohibited area, for example, the closest exposure shot area PR2 in the areas where the measurement result is valid. The result of the tilt angle measurement at is used instead.

On the other hand, when the exposure range of one shot by the projection lens 17 is a relatively large square area as shown in FIG. 2B, the input means 26 of FIG.
An area for 12 blocks including the edges of 8 and shaded in FIG. 2B is designated as the measurement prohibited area. As the tilt angle of the shot area PR3 in the measurement prohibited area, for example, the tilt angle of the closest shot area PR4 in the area where the measurement result is valid is used. In addition, for example, a method of shifting the XYZ stage 24 to a region PR5 that does not cover the edge portion of the wafer 18 and regarding the measurement result of the inclination there as the inclination of the region PR3 can be considered.

Input information I to the input means 26 in FIG.
As the ND, information on the outer shape of the pattern formed on the reticle 16 outside the maximum exposure range of the projection lens 17 or information indicating the degree of opening / closing of the blind 13 can be used. Since the outer shape of the pattern of the reticle 16 and the exposure area limited by the blind 13 are smaller than the maximum exposure range (maximum field of view) of the projection lens 17, the measurement prohibited area can be set more finely. Therefore, the area where the measurement result is effective can be expanded, and the leveling of the wafer 16 can be performed more accurately as a whole.

Next, as an example of the case where the measurement prohibited area changes depending on the state of the wafer, a case where the resist removal processing is performed on the wafer will be described. As described above, resist removal is performed in order to suppress the generation of foreign matter caused by the resist and the like that has wrapped around the outer peripheral portion of the wafer, but in the region where this treatment is performed, the inclination of the wafer surface is locally Often changes. First, assuming that the resist removal is performed on a region 18a shaded by a distance r1 from the outer peripheral portion of the wafer 18 as shown in FIG. 3A, the information on the region 18a is input information IND.
Is supplied to the input means 26 of FIG.
Is designated as the measurement prohibited area. When the exposure shot area is the area PR6 that covers the measurement prohibited area 18a, for example, the tilt angle in the exposure shot area PR7 that is the closest to the area in which the measurement result is valid is used as the tilt angle.

In recent years, there are a dedicated machine for performing resist removal processing, an apparatus in which an exposure processing section for resist removal is provided in an exposure apparatus, and the like. Further, the width of resist removal can be adjusted. Therefore, as in the wafer 29 shown in FIG. 3 (B), the width r2 of the resist removal range may be wider than the width r1 in FIG. 3 (A). When exposing such a wafer 29, the information of the resist removal range is supplied to the input means 26 of FIG. 1, the region 29a of the width r2 is designated as the measurement prohibited region, and erroneous measurement of the tilt angle is prevented. To be done. As the inclination angle of the exposure shot area PR8 related to the area 29a, for example, the inclination angle of the area PR9 close to it is used.

Generally, since there is a step between the resist removal range and the other range, by detecting the step, the resist removal range or the range where the state of the surface is locally changed is detected and measured. The prohibited area may be automatically set. A focus detection mechanism can be used to measure such steps.

FIG. 4 shows an example of an exposure apparatus provided with such a focus detection mechanism. In FIG. 4, parts corresponding to those in FIG. 1 are designated by the same reference numerals. In FIG. 4, 30
Is a wafer from which the peripheral resist has been removed in the wafer process up to then, and the step 3
0a remains. The wafer 30 is placed on the leveling stage 23. Reference numeral 31 denotes a point light source such as a light emitting diode or a laser diode having a weak sensitivity to the photosensitive material, and the light emitted from the light source 31 is obliquely formed with respect to the optical axis 17a of the projection lens 17 by the condenser lens 32 by the wafer 30.
Focus on top. The reflected light from this focusing point is focused on the detector 34 for detecting the light receiving position by the condenser lens 33, and the detection signal S4 of this detector 34 is supplied to the input means 35 as the input information IND. The input means 35 obtains the measurement prohibited area from the detection signal S4 and informs the leveling processing system 25 of the measurement prohibited area using the control signal S2. Other configurations are the same as those in FIG.

In FIG. 4, when the XYZ stage 24 is moved, the wafer 30 moves under the projection lens 17,
When the focal point of light by the condenser lens 32 crosses the step 30a, the position of the center of gravity of the detected light on the detector 34 changes.
Therefore, the input unit 35 can detect the step 30a of the wafer 30 from the detection signal S4, and at that time, the area outside the coordinate position of the XY stage is designated as the measurement prohibited area. Thus, for example, even if the width of resist removal changes depending on the process, the measurement prohibited area can be set automatically and accurately. Even when the resist on the peripheral portion is already removed as shown in FIG. 5B at the time of being held on the stage 23, it is possible to similarly measure the step.

The present invention is not limited to the above-described embodiments, and it goes without saying that various configurations can be adopted without departing from the gist of the present invention.

[0035]

According to the present invention, the measurement restriction area can be arbitrarily set by the input means. Therefore, the measurement area can be set most efficiently and accurately according to the exposure area of the projection optical system and the surface condition of the photosensitive substrate. There is an advantage that the inclination of the photosensitive substrate can be corrected.

Further, when the measurement restriction area is set based on the maximum exposure range of the projection optical system, the illumination range restricted by the blinds, or the range where the photosensitive material is removed,
The measurement restriction area can be set as narrow as possible, and the tilt of the photosensitive substrate can be corrected more accurately. Further, when the step measuring means is provided, there is an advantage that the measurement restriction area can be accurately set even when the width of the photosensitive material removal changes.

[Brief description of drawings]

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

FIG. 2 is a plan view of the wafer 18 when the exposure area of the projection lens 17 in FIG. 1 changes.

FIG. 3 is a plan view showing wafers having different resist removal widths.

FIG. 4 is a block diagram showing a main part when a focus detection mechanism is added to the exposure apparatus of FIG.

FIG. 5 is a cross-sectional view for explaining a resist removal range of a wafer.

FIG. 6 is a perspective view of a main part showing a case where the tilt of the wafer surface in the vicinity of the resist removal range is measured by a conventional exposure apparatus.

[Explanation of symbols]

 17 Projection Lens 18 Wafer 19 Light Source 20 Collimator Lens 21 Condenser Lens 22 Detector 23 Leveling Stage 25 Leveling Processing System 26 Input Means 30 Wafer 32, 33 Condenser Lens 35 Input Means

Claims (5)

[Claims] 1. An apparatus for exposing a pattern formed on a reticle onto a photosensitive substrate via a projection optical system, the inclination measurement for measuring an inclination of a designated exposure shot position on an exposed surface of the photosensitive substrate. Means, an input means for setting a measurement restriction area on the exposed surface of the photosensitive substrate that does not use an actual measurement value of the inclination, and a measurement result of the inclination measuring means and the measurement restriction area on the exposed surface. A driving mechanism that corrects the tilt of each exposure shot position, the driving mechanism, at the exposure shot position of the measurement restricted region, the tilt at an exposure shot position outside the measurement restricted region near the exposure shot position. An exposure apparatus, which corrects the inclination according to the measurement result of 1. or the preset inclination. 2. The exposure apparatus according to claim 1, wherein the input unit sets the measurement restriction area based on information on a maximum exposure range of the projection optical system. 3. A blind for limiting an illumination range is provided in an illumination optical system for illuminating the reticle, and the input unit sets the measurement limited area based on information on the illumination range limited by the blind. The exposure apparatus according to claim 1, wherein the exposure apparatus is provided. 4. A photosensitive substrate, the peripheral portion of which is exposed to remove the photosensitive material at the peripheral portion, is used as the photosensitive substrate, and the input means measures the information from the peripheral portion at which the photosensitive material is removed. The exposure apparatus according to claim 1, wherein the exposure apparatus sets a restricted area. 5. A step measuring device for measuring a step of a peripheral portion of the photosensitive substrate is provided, and the input device sets the measurement restriction region based on a measurement result of the step measuring device. The exposure apparatus according to claim 1.