JP2002110541A - Scanning type aligner and method for manufacturing device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately superpose a pattern of an original plate on a pattern area of a board in a scanning alignment. SOLUTION: A scanning type aligner comprises a projection optical system 21 for projecting the pattern of the original plate illuminated by an exposure light from a light source 9 on the board 18, and a scanning means (14, 23) for scanning the light on the plate and the board. The aligner further comprises a means for detecting a shape of the pattern area of the plate and a shape of the transfer area of the board.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure method, a scanning exposure apparatus, and a device manufacturing method using the scanning exposure apparatus, and more particularly, to semiconductor chips such as ICs and LSIs, liquid crystal elements, magnetic heads, and CCDs (imaging elements). The present invention relates to an exposure method, a scanning exposure apparatus, and a device manufacturing method using the scanning exposure apparatus for manufacturing a device such as the above.

[0002]

2. Description of the Related Art When exposing a device pattern using a scanning type exposure apparatus, the demand for the accuracy of superposition of a reticle and a wafer is becoming more and more severe. For example, 64
For the manufacture of Mbit DRAMs, a line width of 0.35 μm
Since it is necessary to form a pattern of about m on the wafer, it is necessary to correct not only a positional deviation in the XYθ direction but also a local magnification error of about 0.01 μm.

[0003]

The conventional scanning type exposure apparatus corrects a local magnification error in the scanning direction by changing the ratio of the scanning speed between the reticle and the wafer during scanning. Since a local magnification error could not be corrected in the orthogonal direction, the reticle pattern could not be accurately superimposed on the pattern area on the wafer, which hindered the manufacture of finer devices.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a scanning exposure apparatus capable of accurately superimposing a pattern of an original plate on a pattern area on a substrate, and a device manufacturing method using the scanning exposure apparatus. Is to do.

The scanning exposure apparatus of the present invention has a projection optical system for projecting a pattern of an original illuminated by exposure light onto a substrate, and scanning means for scanning the original and the substrate with the exposure light. The scanning exposure apparatus is characterized in that it has means for detecting the shape of the pattern area of the original plate and the shape of the transfer area of the substrate.

A scanning exposure apparatus according to an embodiment of the present invention includes a projection optical system that projects a pattern of an original illuminated by exposure light onto a substrate, and a scanning unit that scans the original and the substrate with the exposure light. Wherein the scanning direction of the substrate relative to the scanning direction of the original plate is changed based on the shape of the pattern region of the original plate and the shape of the transfer region of the substrate.

In one embodiment of the scanning type exposure apparatus according to the present invention, the projection magnification of the projection optical system is changed based on each of the shapes.

In one embodiment of the scanning exposure apparatus according to the present invention, there is provided a projection optical system for projecting a pattern of an original illuminated by exposure light onto a substrate, and scanning means for scanning the original and the substrate with the exposure light. Wherein the projection magnification of the projection optical system is adjusted based on the shape of the pattern area of the original plate and the shape of the transfer area of the substrate.

In one embodiment of the scanning exposure apparatus according to the present invention, the projection magnification is changed during the scanning.

In one embodiment of the scanning exposure apparatus according to the present invention, there is provided a projection optical system for projecting a pattern of an original illuminated by exposure light onto a substrate, and scanning means for scanning the original and the substrate with the exposure light. Wherein the scanning magnification of the projection optical system is changed during the scanning, and the scanning direction of the substrate with respect to the scanning direction of the original plate is changed.

In one embodiment of the scanning exposure apparatus according to the present invention, the scanning direction of the substrate with respect to the scanning direction of the original plate is changed during the scanning.

[0012] A device manufacturing method according to the present invention includes a step of exposing a substrate to a device pattern by a scanning exposure apparatus according to any one of claims 1 to 5, and a step of developing the exposed substrate. It is characterized by the following.

[0013]

FIG. 1 is a schematic view of a step and scan type projection exposure apparatus for manufacturing a device according to an embodiment of the present invention. In the present exposure apparatus, at the time of scanning exposure, the wafer stage 23 is servo-locked by the tracking control with respect to the absolute coordinate system, that is, the mask stage 14 which is caused to scan with respect to the stationary mechanical origin 24 on the exposure apparatus. Reference numerals 15a and 15b denote scanning directions of the mask stage 14 and the wafer stage 27 during scanning exposure, respectively. An exposure beam 20 for exposing an exposure area 19 on a wafer 18 which is a photosensitive substrate is emitted from a light source 9 to an optical system 10.
The light is shaped into an elongated shape by the slit 11 via the light source. The opening width of the slit 11 is
3 and scanning speed of reticle stage 14, exposure beam 2
It is configured so that it can be changed according to the intensity of 0. 12
L, 12R, 22L, and 22R are alignment marks arranged on the left and right sides of the exposure area on the reticle M and the wafer 18, respectively. Alignment mark groups 12, 22
Are both composed of a grid pattern as shown in FIG. The relative positional deviation between the reticle and the wafer in the X and Y directions can be detected from these lattice patterns, and the relative positional deviation in the θ direction, that is, the rotational deviation can also be detected. The relative displacement between the wafer 18 and the reticle M is measured by the alignment measurement unit 6. That is, the measurement beam 8 emitted from the laser diode 13 driven by the LD driver 5 is irradiated toward the alignment marks 12 and 22 on the reticle M and the wafer 18, and reflected and diffracted by the alignment marks 12 and 22. The measurement beam 8 returning to the optical path of the projection beam by the beam splitter 7
Is deflected from the optical path of the projection beam through the optical sensor 1
Reach The alignment measurement destination (interference light) is converted into an electric signal by the photo sensor 1, amplified by the preamplifier 2, and then the alignment measurement signal, that is, the relative displacement signal 4 is generated by the phase measurement unit 3.

Reference numerals 27 and 28 denote laser interferometers for measuring the position coordinates of the mask stage and the wafer stage, respectively. The mask stage 14 is controlled by the laser interferometer 27
The position is measured and controlled in the axial direction. The wafer stage 23 is controlled by a laser interferometer 28 for X, Y, θ,
The position is measured and controlled in the ω _x and ω _y directions. 1
Reference numerals 7a to 17c denote linear motors which generate thrusts in the X, Y, and θ directions for driving the wafer stage 23. The wafer stage 23 is a surface plate 25 also serving as a planar guide.
, And a tilt stage (not shown) composed of three piezoelectric elements is mounted on the wafer stage 23 so as to hold the wafer 18. With these configurations, the wafer stage 23 achieves high-precision positioning performance that is not easily affected by vibration or friction transmitted from the outside. Reference numeral 16 denotes a linear motor for driving the mask stage 14. Similarly to the wafer stage 23, the mask stage 14 is driven while being floated and supported by a small amount of a static pressure guide (not shown). In this embodiment, the mask stage 14 has a drive stroke only in the X direction. 26 is a television alignment scope for pre-alignment,
32 is a pre-alignment image processing unit. Wafer 1 adsorbed on wafer stage 23 prior to exposure
8 is first pre-aligned by the pre-alignment scope 26. That is, the pre-alignment mark formed in advance on the wafer 18 is
The image is picked up at 6 and an image signal is detected. The image signal output from the pre-alignment scope 26 is converted into a position shift signal by the pre-alignment image processing unit 32,
Is output. The wafer 18 that has been pre-aligned based on the position shift signal enters a scanning exposure process. The lattice pattern of the alignment mark group on the reticle M and the wafer 18 is drawn on the exposure shot at a pitch of about 10 μm (see FIG. 3). 5μ
m), the alignment measurement unit 6 cannot perform accurate alignment measurement if the alignment scanning exposure is performed during the exposure. This is because the alignment measurement unit 6 measures the phase difference of the measurement light 8 (the light from the reticle and the light from the wafer) as a relative position shift amount, so that a shift between marks of one or more pitches of the grid pattern occurs. This is because it becomes impossible to distinguish between them. Therefore, the pre-alignment accuracy of the pre-alignment scope is set to ± 1 μm, and the relative displacement between the image of the reticle M and the exposure shot on the wafer 18 after the pre-alignment is set to ± 5 μm or less including other error factors. are doing.

FIG. 2 shows the configuration of the projection optical system 21 of FIG. In the figure, 201a, 201b and 201c
Denotes a lens constituting the projection optical system. 202a, 20
2b and 202c are lenses 201a and 201c, respectively.
This is a lens barrel holding b and 201c. Also, 212
Denotes an air bearing guide for guiding the lens barrel 202b;
Reference numeral 3 denotes a static pressure pipeline for applying a static pressure to the air bearing guide 212, 204 denotes a driving pressure pipeline for supplying a pressure for driving the lens barrel 202b, 206 denotes a driving pressure supply source, and 215 denotes a lens barrel 202.
It is a spring that supports b. 216 is a piezo element for driving the entire projection optical system, 207 is a piezo element driving circuit, 210
Numeral 209 denotes an air sensor nozzle fixed to the lower end of the projection optical system for measuring the distance from the wafer 18, 209 a pneumatic pipeline for the air sensor, and 208 a converter for converting the back pressure of the air sensor into an electric signal. Reference numeral 203 denotes a projection optical system surface plate that supports the projection optical system.

The space between the projection optical system 21 and the wafer 18 is detected by the air sensor nozzle 210 using the back pressure of air. This interval value is compared with a predetermined target value, and the piezo element 216 is driven so that the interval to the wafer 18 matches the target value, thereby completing the focusing operation. Through the alignment scope 6, the relative displacement between the pair of alignment marks on the reticle M and the pair of alignment marks on the wafer 18 is detected. The lens 201b is finely adjusted so that the magnification error obtained from the relative shift amount becomes zero.

FIG. 4 is a diagram showing a scanning control system of this embodiment. Reference numeral 211 denotes a projection optical system arithmetic unit that controls the projection magnification of the projection optical system 21 so that the magnification target value 408 is instructed by a higher-level controller (described later), and simultaneously corrects defocus. Reference numeral 401 denotes an alignment operation unit,
From the alignment marks on both sides of the exposure shot as shown in FIG. 3, X-direction (scanning direction) component of the alignment detection value 409a ([Delta] X _L) and 409b ([Delta] X _R) and the scanning direction in the Y direction (angle in the plane perpendicular Direction) component alignment detection values 409c (ΔY _L ) and 409d (ΔY _R )
Is output to the host controller. 402 is a wafer stage control system computing unit, X of the wafer stage 23 measured by the laser interferometer _{28, Y, θ, ω x} , Z component measured by the gap sensor 208 to 210 of the omega _y component and 2 The amount of operation is given to the driver 407 that supplies the driving power to each actuator so that the position coordinates of the target controller become target values 410a, 410b, and 410c (only the X, Y, and θ components are indicated) specified by the upper controller. Output. 4
03 is a mask stage control system computing unit, and outputs the operation amount to the driver 407 so that the X component position coordinates measured similarly with the laser interferometer 27 and a wafer stage control system 402 becomes equal to the target value X _M . The wafer stage control system computing unit 402 and the mask stage control system computing unit 40
3 is a laser interferometer 2 in which the two stages are accelerated before the tracking scanning exposure using the alignment measurement signal as feedback and when the tracking is not performed because the alignment measurement signal cannot be detected satisfactorily.
7 has a high-speed communication path 415 for scanning the reticle and the wafer at a projection magnification ratio of the projection optical system 21 based on the measurement value of the measurement optical system 7. Reference numeral 404 denotes a scanning exposure arithmetic processing device which is a higher-level controller. The scanning exposure arithmetic processing unit 404 performs arithmetic processing for obtaining a predetermined operation amount from the alignment detection value 409 from each alignment mark obtained from the alignment system arithmetic unit 401, and performs a magnification target value 408, a wafer stage target value 410, a reticle stage target value. 412
Are sequentially output. The wafer stage target value 410 and the reticle stage target value 412 are updated every predetermined time, for example, every 0.5 msec. In the above-described arithmetic processing, the magnification target value 408 is calculated as a function for the alignment detection value or a value referred from a data table. The function or data table corrects the magnification reading error from the alignment signal caused by the local shape and pattern tendency of the pattern formed on the wafer and the difference from the ideal shape of the alignment mark. is there. These function tables can be changed for each process and each reticle, all of which are stored in the storage device 405 and read into the scanning exposure arithmetic processing device 404 via the communication path 414 as necessary.

FIG. 3 shows a shot and an alignment mark 22 on the wafer 18 to be exposed in the present embodiment. On both sides of the circuit pattern 301, grids for measuring a shift in the X direction from an image of the reticle are respectively provided. Patterns 22LX and 22RX are arranged, and a grid pattern 2 for measuring a shift in the Y direction in parallel with the patterns.
2LY and 22RY are arranged. If the detected values of the shift amounts in the individual lattice patterns 22LX, 22LY, 22RX, and 22RY are ΔX _L , ΔY _L , ΔX _R , and ΔY _R , the correction amount of the translation component is obtained in principle by the following equation. Can be

(X direction correction amount) X _C = (ΔX _L + ΔX _R ) / 2 + Mdx (1) (Y direction correction amount) Y _C = (ΔY _L + ΔY _R ) / 2 + Mdy (2) ( θ direction correction amount) θ _C = (ΔX _L −ΔX _R ) / L (3) where L is the Y direction alignment pattern 22LY, 22
Indicates the distance between RYs. Mdx and Mdy are parameters such as a constant or magnification for correcting an error of the average positional deviation amount in the circuit pattern 301 caused when a magnification change exists within the exposure angle of view, an alignment value of a surrounding exposure shot, a magnification value, and the like. Is a function of On the other hand, the correction amount of the magnification component is calculated at the k-th alignment measurement value ΔX _L (k), ΔY _L (k), ΔX _R (k), Δ
If Y _R (k) is sampled, it can be obtained by the following equation.

[0020]

[Outside 1]

Here, α is a coefficient for calculating the X-direction correction magnification and for weighting the mark 22LX and the mark 22RX for use in the magnification correction value because one of them is redundant. V _st is the scanning speed of the wafer stage. In the present embodiment, as shown in FIG.
3a and 303b are located at the exposure start points. Therefore, the projection magnification of the projection optical system 21 that is corrected according to the correction magnification obtained by the equations (4) and (5) is adjusted to the ideal projection magnification at the exposure start point. Exposure slit 3
If it is desired to bring the correction point of the projection magnification to the center 304 side of 02, (4), k on the right side of the expression (5) is given by (kn) (n
May be replaced by an integer).

The variation in further occur because the S / N ratio of the sampling interval T is smaller alignment measurement signal is lower _m x (k) and _m y (k) is increased. In the present embodiment, the magnification correction value obtained for each sampling is not immediately output to the projection optical system arithmetic unit 211, but is output after averaging using a weighting function. FIG. 6 shows an example of the weighting function. The shape of the envelope 601 of the weighting function Wk can be changed according to the size of the opening of the slit 11 or the response characteristic of the projection optical system 21 to the command magnification. or,

[Outside 2]

There is a relationship as follows.

As a result, the final correction magnification is obtained by the following equation.

[0025]

[Outside 3]

Here, when the weighting function W (k) having the envelope shape as shown in FIG. 6 is used, the correction point of the projection magnification tends to move near the beak position of the envelope 601.
The magnifications MX and MY thus obtained have profiles as shown in FIGS. 5A and 5B in the X direction, which is the scanning direction. This magnification value is input to the filter function F shown in FIG. 7, and the output of the filter function F is the magnification target value ΔM finally passed to the projection optical system calculator 211.
Becomes

ΔM = Fx {MY (k)} (10) In this embodiment, the magnification target value (relative magnification value) obtained for each sampling time by the above equation (10) is immediately used as a projection optical system arithmetic unit. 211 and input to the projection optical system arithmetic unit 21
1 changes the projection magnification so that the projection magnification of the projection optical system 21 follows the magnification target value.

In this embodiment, since the magnification change of the projection optical system 21 is only the same magnification change, the relative magnification value command of the projection optical system 21 is represented by the Y component correction magnification value. X
The magnification change in the direction can be operated by changing the speed ratio between the scanning speed V _M of the mask stage and the scanning speed Vst of the wafer stage. However, the slit width d of the exposure area
Δ pattern image by the difference in projection magnification Nop and scanning speed ratio Vst / V _M of but a projection optical system with a value greater than 0 in passing the exposure slit shown on the projection plane by the following equation (11)
Moves by x, resulting in lower resolution.

(Distance moved on the projection plane) δx = | Nop−Vst / V _M | · d (11) Therefore, in this embodiment, Vst is set within a range where δx does not exceed a certain threshold value. and fine adjustment, Vst / V _M is operating so as to follow with respect to the change basically Nop.

The filter function shown in FIG. 7 is caused by the local shape and arrangement tendency of the pattern formed on the wafer described with reference to FIG. 4, the difference between the alignment mark and the shape of the circuit pattern, and the like. It is for correcting a magnification reading error from the alignment signal that occurs. Fx (M
X), the input parameter of Fx (MY) is the supplementary magnification target value M
It can have other than X and MY.

If the projection magnification changes while the slit for scanning exposure passes, Nop = Vst / V _M (12) Even if the condition is satisfied, the pattern image follows the projection surface on the projection surface (13)
The resolution is degraded due to the movement of Δx1 shown in the equation.

Δx1 ≒ V _M · α op · t ² (13) Here, α op is a magnification increase per unit time on the assumption that the magnification of the projection optical system 21 increases in proportion to the passage of time. Quantity. There is an upper limit of the allowable value for the resolution degradation due to the change in the projection magnification. Therefore, in this embodiment, Fx
When the rate of change of {MY (k)} in the sample time interval is small, the relative magnification value is determined by the relationship of equation (10). It is configured to output. FIG. 8 shows the contents of this processing.
Shown in

In FIG. 8, a relative magnification value F sequentially obtained from alignment measurement values measured at each sample time is shown.
For x {MY (k)}, a difference value δFx is obtained with respect to the relative magnification value ΔM (k−1) previously output to the projection optical system 21 (803). Subsequently, it is determined whether or not δFx exceeds an absolute value of a threshold value a derived from a specification defining resolution degradation (804). If it does not exceed (808), the process proceeds to step 806, and if it does exceed (801), the upper limit a that allows the above difference value as a difference value
Alternatively, it is substituted with the lower limit -a (805). Step 80
In step 6, the above-mentioned difference value or the replaced difference value is added to the relative magnification value ΔM (k−1) previously output to the projection optical system 21 to obtain a new relative magnification value ΔM (k). In step 807, ΔM (k) is stored in the memory so that the relative magnification value is used in the next calculation processing. In step 802, an argument indicating the parameter sampling order is incremented for the next calculation.

As described above, in this embodiment, the projection optical system 2
By limiting the magnification change of 1, the resolution is intended to be kept within the specified range. Step 8
By changing the value of the parameter a in step 04, the degree of freedom of the projection optical system 21 with respect to the change in the projection magnification can be changed. (Alignment correction) It is possible to adjust the priority of scanning exposure. On the other hand, in addition to the flow shown in FIG.
For example, a method of limiting using a continuous function without setting a threshold value can be considered. Further, the flow shown in FIG. 8 is not only a method of exposing a wafer while performing alignment measurement, but also a method of performing scanning exposure after performing alignment measurement in advance.
The present invention can be applied to a scanning exposure apparatus of a global alignment method and a pre-scan method.

FIG. 9 shows a configuration diagram of a projection optical system 21 according to another embodiment of the present invention. Reference numerals 201 to 216 are the same members as those described with reference to FIG. 905a, 905
b is a lens group including a cylindrical lens,
It is supported by lens support members 906a and 906b. These cylindrical lenses are piezo elements 90
3 and 904 minutely drive in the optical axis direction.
Piezo elements 903 and 904 are respectively a driver 901,
It is controlled under the command of the projection optical system arithmetic unit 211 via 902. FIG. 1 shows the cylindrical lenses 905a and 905b.
Has power in the Y direction at the other lens 201
The Y-direction partial magnification of several + ppm is applied to the reduction magnification (１ ／ in this embodiment) uniformly obtained by a to c. The magnification of the lenses 201a to 201c can be changed equally in the XY directions by driving the lens 201b and the lens barrel in the optical axis direction, as is apparent from the description of FIG. Therefore, the rotationally symmetric lenses 201a to 201a
The setting of the magnification in the X direction and the Y direction in the vicinity of the projection magnification value of に よ り can be arbitrarily performed by a combination of the magnification change in the XY direction due to c and the magnification change in the Y magnification by the cylindrical lenses 905a and 905b. It can be configured. The relative magnification value (magnification target value) ΔM 408 input to the projection optical system calculator 211 has two parameters of an X component and a Y component in this embodiment. Further, the filter function described in FIG.
Is applied to this embodiment in exactly the same way as in the previous embodiment. The scanning speed of the wafer stage 23 is finely adjusted substantially according to a change in the X-direction projection magnification of the projection optical system 21. Further, a cylindrical mirror is arranged on the optical path of the projection optical system 21 instead of the cylindrical lenses 905a and 905b, and the relative position or curvature of the mirror to another optical system (an example of finely adjusting the curvature in the third embodiment is presented). ) Can be finely adjusted.
In any case, the same function can be realized by supplying an anamorphic optical system in which a cylindrical element or the like is arranged on the optical path of the projection optical system.

This configuration is also applicable to an exposure method for exposing a wafer while performing alignment measurement, a method for performing scanning exposure after performing alignment measurement in advance, a global alignment method, and a pre-scan type scanning exposure apparatus. Is possible.

FIG. 10 shows a third embodiment of the present invention. FIG.
0, the members having the same numbers as those in FIG. 1 perform the same functions as the members described in FIG. 1001 is a mirror, and the back side of the reflection surface is a closed space 1002. A fluid is sealed in the closed space 1002, and a differential pressure is generated with respect to the external atmosphere by flowing or discharging the fluid from the fluid introduction path 1003. Due to the generation of the differential pressure, pressure is applied to the mirror 1001 in a direction perpendicular to the mirror surface, and the mirror 1001 is slightly distorted, and the magnification of the image formed by the reflected light slightly changes compared to when the differential pressure is 0. 1004 is a valve unit for controlling the amount of fluid flowing into the closed space, and 1005 is a controller for controlling the valve unit. 1006 and 1007 are quarter-wave plates, 100
8 is a beam splitter. 1009 is a light receiving lens for picking up an alignment signal, and 1013 is an alignment signal processing device. 1010 is a mirror and 1011 is an objective lens group. The objective lens group 1011 is controlled by the lens control device 1012 and corrects defocus and the like due to minute distortion of the mirror 1001. With the above configuration, the exposure light emitted from the light source 9 reaches the reticle via the slit 11 and the optical system 10. Exposure light transmitted through the reticle is reflected by a mirror 1001, transmitted through a quarter wave front plate 1006, a beam splitter 1008, and a quarter wave front plate 1007, and reflected by a mirror 1010.
Further, the reflected exposure light is reflected by the thin film 1013 in the beam splitter 1008, passes through the objective lens group 1011 and forms an image on the wafer 18. Since the light receiving element 1 can detect the alignment signal even during the scanning exposure,
In the present embodiment, as in the first embodiment, magnification measurement during scanning exposure and magnification correction in real time are possible. Further, as an application of the present embodiment, the mirror 1001 has a distortion characteristic that produces a cylindrical reflecting surface, and the lens group 1011 has at least one cylindrical lens, thereby providing a magnification function in the X direction or the Y direction. Is also possible.

The effects of the embodiment described above will be listed below.

1. By sequentially reflecting the correction magnification value obtained from the alignment measurement signal during the scanning exposure on the projection magnification value of the projection optical system 21, the local magnification distortion of the exposure shot in the scanning exposure can be corrected for each shot.

2. By making the scanning speed of the stage follow the magnification change in the scanning direction of the projection optical system, the displacement of the projection pattern position is minimized.

3. Further, by configuring the projection optical system to include a cylindrical lens or a cylindrical mirror, the projection magnifications in the X and Y directions can be corrected independently of each other.

4. The correction magnification value obtained from the alignment measurement signal is converted into a magnification value of the projection optical system 21 by converting the correction magnification value obtained from the alignment measurement signal based on a function or a data table input in advance. The difference between the projection magnification value obtained from the above and the magnification value for aligning the actual pattern can be corrected.

5. The closed space provided on the back of the mirror is filled with fluid, and the amount of fluid is controlled to generate a differential pressure between the closed space and the external atmosphere, causing the mirror to be slightly distorted, resulting in a small change in the projection magnification. did.

6. By calculating a local correction magnification value by multiplying a correction magnification value obtained from a plurality of alignment measurement data groups required for the magnification calculation process by a weighting function, the S / N of the alignment measurement signal value, noise, and the like are obtained. A stable correction magnification value that is hardly affected can be calculated.

7. Projection optical system 2 that can change during scanning exposure
By limiting the width of the projection magnification value of 1 for a certain period of time, resolution degradation due to magnification correction was suppressed within limits.

8. By making the change width of the magnification value variable, the user can freely set the magnification (alignment) priority / resolution priority in scanning exposure.

As a factor of deteriorating the alignment between the reticle pattern and the wafer pattern, there is a problem that the wafer is deformed from its initial shape while being subjected to processes such as oxide film formation, ion implantation, and etching. This deformation mainly appears as a change in the magnification of the pattern during projection exposure.

The degree of deformation of the wafer often differs between the direction of the crystal axis of the substrate and the other direction, and the magnification and orthogonality are not uniform. Also, since the amount of expansion and contraction due to heat changes in relation to the distance from the center of the wafer, the amount of deformation of the pattern near the center of the wafer and the amount of deformation of the pattern near the outer periphery are different, and the wafer has a non-linear shape. There are various patterns.

In addition, in the semiconductor manufacturing process, not all the steps are performed by the same projection exposure apparatus. When an attempt is made to match a mask pattern with a pattern exposed in a previous step by another apparatus, a projection optical system is required. If matching between the distortions of the competitors or matching of the bending (bowing) in the scanning direction of the scanning exposure system is not performed, it is recognized as a non-linear shape deviation of the pattern of the substrate.

According to the above-described embodiments and the scanning projection exposure apparatus of each embodiment described below, even if there is a non-linear shape deviation of the wafer pattern of this kind, the reticle pattern and the wafer pattern can be accurately corrected. It is possible to superimpose.

FIG. 11 is a schematic view of a scanning exposure apparatus according to another embodiment of the present invention. The mask M, which is an original image, is supported by the apparatus main body by a mask stage 14 whose driving in the XY directions is controlled based on the output of a laser interferometer (not shown). On the other hand, the wafer 18 as an exposure substrate is supported by the apparatus main body by a wafer stage 23 whose driving in the XY directions is controlled based on the output of a laser interferometer (not shown). The mask M and the wafer 18 are connected to the projection optical system 21.
And a slit-like exposure light area 116 from an illumination system (not shown) is used to project the pattern image of the mask M onto the wafer at a size corresponding to the projection magnification of the projection optical system 21. 3 is projected. The scanning exposure is performed by exposing the exposure light 116 to the mask stage 14 and the wafer stage 2.
3 is performed in the X direction at a speed ratio according to the projection magnification of the optical system 21. The entire pattern area 121 on the mask 1 is transferred to a transfer area 122 on the wafer 3. In this figure, the projection optical system 2 constituted by a refraction element such as a lens is shown, but a projection optical system combining a reflection element and a refraction element as shown in FIG. As shown in this figure, the size may be reduced other than the same size. In addition, the outer shape of the wafer 18 is not specified in this drawing, and when a reduction projection optical system is used, the wafer 18 has a plurality of transfer areas 122.

The alignment between the mask M and the wafer 18 is detected by using the observation microscope 117. First, after supporting the mask M on the main body, the drawing state of the original image of the mask M is measured.
A plurality of mask marks 151 arranged on the mask M are observed by the observation microscope 117, and a signal from the microscope 117 is sent to the arithmetic processing circuit 1102 as position information of the mask mark 151 processed by the mark detection signal 1101. Since the position of the mask stage 14 at the time of the observation is detected by a laser interferometer (not shown), the stage position is sent from the drive control unit 1103 to the arithmetic processing circuit 1102, and the position corresponding to the position information of the mask mark 151 is obtained. Is stored. This measurement is performed on a plurality of mask marks 151 by controlling the mask stage 14 by using a laser interferometer (not shown) to sequentially repeat the measurement.
The drawing state of the original image of the mask M is determined. The mask mark 151 is drawn simultaneously with the pattern area 121 on the mask M, and represents a drawing origin, a drawing magnification, and a drawing orthogonality of the pattern area 121. When measuring the drawing magnification and the drawing orthogonality, the mask mark 151 must be at least 3
More mask marks 151 are needed, and more mask marks 151 are needed to measure the non-linear component of the drawing error.

Although the mask marks 151 are arranged so as to sandwich the pattern area 121 in this figure, there is no problem if they are arranged in the pattern area 121, and the shape is not limited to a cross. The actual element pattern drawn in 121 may be measured as a mask mark.

Next, the wafer mark 152 arranged around the transfer area 122 of the wafer 18 is
To observe through the correction optical element 118 and the projection optical system 21. The correction optical element 118 is a projection optical system 2 generated when the observation light wavelength of the observation microscope 117 is different from the exposure light.
The chromatic aberration corrector 1 is preferably disposed at a position that does not interfere with the optical path of the exposure light 116. The observation microscope 117 uses the light having the same wavelength as the exposure light to produce the wafer mark 152.
When observing, the correction optical element 8 becomes unnecessary.

A plurality of wafer marks 1 arranged around the transfer area 122 of the wafer 18 by the observation microscope 117
52, the signal from the microscope 117 is processed by the mark detecting means 1101 as in the case of the mask mark 151, and is processed by the arithmetic processing circuit 1 as position information of the wafer mark 152.
102. Since the position of the wafer stage 23 at the time of the observation is detected by a laser interference type (not shown), the stage position is sent from the drive control unit 1103 to the arithmetic processing circuit 1102, and the position corresponding to the position information of the wafer mark 152 is obtained. Is stored. This measurement is performed on a plurality of wafer marks 152 by controlling the wafer interferometer (not shown) while sequentially controlling the plurality of wafer marks 152 so that the shape of the transfer area 122 on the wafer 18 is determined. Become. Since the shape of the transfer area 122 is observed through the projection optical system 21, the projection optical system 2
Observation microscope 1 is assumed to include a change in the projection magnification of 1.
17 and the mark detecting means 1101.

When the projection optical system 21 is a reduction projection optical system, a plurality of transfer areas 122 on the wafer 18 are often present. In this case, the position information of the wafer mark 152 is measured for each transfer area 122, and is stored as a shape for each transfer area 122 on the arithmetic processing circuit 1102.

In order to measure the magnification and orthogonality as the shape of the transfer area 122, at least three or more wafer marks 152 are required.
More wafer marks 152 are required. Further, the arrangement place and shape are not limited to the present embodiment, but are arbitrary.

The measured pattern area 12 on the mask M
The deviation between the drawing state shape of No. 1 and the shape of the transfer region 122 on the wafer 18 causes an error during exposure transfer. This error is caused by the arithmetic processing circuit 11 storing the error during the scanning exposure.
02, a scanning drive method for correcting an exposure transfer error is instructed to the drive control unit 1103, and scan exposure is performed while controlling the positions of the mask stage 4 and the wafer stage 5 using a laser interferometer (not shown). It is corrected by driving some optical elements in the system 21 and the pattern area 1
Reference numeral 21 denotes a transfer area 12 on the wafer 18 with good alignment accuracy.
2 is transferred.

As a first example, consider a case where a non-linear orthogonality error occurs between the pattern area 121 and the transfer area 122 as shown in FIG. In FIG. 12A, the transfer area 122 is deformed.
Even if the pattern area 121 is deformed, it is a relative problem, and it can be considered that the following correction scanning exposure is performed.

First, in accordance with an instruction from the arithmetic processing circuit 1102 to the drive control means 1103, the pattern area 121 and the transfer area 12 are exposed to the exposure light 116 as shown in FIG.
The scanning start side 2 is aligned. Next, the arithmetic processing circuit 110
2 instructs the drive control means 1103 to drive the mask stage 14 or the wafer stage 23 in the oblique direction by the orthogonality error θ as a scanning drive method for correcting the orthogonality error θ. While controlling the position using the interference type, the exposure light 116 is moved as shown in FIGS. At this time, the orthogonality error θ is θ1,
In the case of a continuous change rather than a constant value such as θ2 and θ3, the non-linear orthogonality error can be corrected by changing the oblique driving amount of the mask stage 14 or the wafer stage 23 accordingly. . As a result, the pattern area 121 can be transferred onto the transfer area 122 with high accuracy.

As a second example, consider a case where a non-linear magnification error occurs in the scanning exposure direction in the pattern area 121 and the transfer area 122 as shown in FIG. FIG.
In FIG. 3A, the transfer area 122 is deformed, but it is a relative problem even if the pattern area 121 is deformed, and it is considered that the following correction scanning exposure will be performed. good.

First, in response to an instruction from the arithmetic processing circuit 1102 to the drive control means 1103, the pattern area 121 and the transfer area 122 are exposed to the exposure light 16 as shown in FIG.
The scanning start side is adjusted. Next, the arithmetic processing circuit 1102
From the scanning control unit 1103 to the scanning direction magnification error βx
As a scanning drive method for correcting (βx = 1wx / 1mx 1wx: distance between marks in the scanning direction of the transfer area 122, 1mz: distance between marks in the scanning direction of the pattern area 121), the magnification of the mask stage 14 or the wafer stage 23 in the scanning direction is used. An instruction is issued to drive while changing the relative speed by the error βx, and the exposure light 16 is moved with respect to the exposure light 16 as shown in FIGS. 13B to 13C while controlling the position using a laser interferometer (not shown). . At this time, the scanning direction magnification error β
When x is not a constant value but continuously changes like βx1 and βx2, the relative speed change amount of the mask stage 14 or the wafer stage 23 is also changed in accordance therewith, so that the non-linear scanning direction is changed. Magnification errors can also be corrected. As a result, the pattern area 121 can be transferred onto the transfer area 22 with high accuracy.

As a third example, consider a case where a non-linear magnification error occurs in the non-scanning exposure direction in the pattern area 121 and the transfer area 122 as shown in FIG. In FIG. 14A, the transfer region 122 is deformed. However, even if the pattern region 121 is deformed, it is a relative problem, and it is considered that the following correction scanning exposure is performed. Good.

First, in response to an instruction from the arithmetic processing circuit 1102 to the drive control means 1103, the pattern area 121 and the transfer area 12 are exposed to the exposure light 116 as shown in FIG.
The two scan start sides are aligned with each other. Next, the arithmetic processing circuit 1102 sends a non-scanning direction magnification error βy (βy = 1wy / 1my1wy: transfer area 1) to the drive control unit 1103.
As a scanning drive method for correcting the distance 1my between the marks 22 in the non-scanning direction in the non-scanning direction (the distance between marks in the non-scanning direction in the pattern area 121), the optical element in the projection optical system 21 is driven by the magnification error βy in the non-scanning direction. From the mask stage 14
Alternatively, an instruction is issued to drive the wafer stage 23,
While controlling the position using a laser interferometer not shown,
It moves with respect to the exposure light 16 as shown in FIG. At this time, the magnification error βy in the non-scanning direction is βy1, βy2
If the value is not constant but changes continuously,
The driving amount of the optical magnification correcting optical element in the projection optical system 21 is accordingly changed in accordance with the scanning exposure driving of the mask stage 14 or the wafer stage 23, so that a non-linear magnification error in the non-scanning direction is obtained. Can also be corrected. As a result, the pattern area 121 can be transferred onto the transfer area 122 with high accuracy.

It is considered that any shape misalignment between the pattern area 121 and the transfer area 22 occurs in the three examples of the composite element shown in FIGS. FIG. 15 shows a shape shift in which the orthogonality error and the non-scanning direction magnification error are combined. If the orthogonality error correction step and the non-scanning direction magnification error correction step are performed simultaneously, the correction can be performed.

Therefore, the pattern area 121 and the transfer area 1
22 can be superimposed with high accuracy on any of the non-linear shape deviations.

As described above, the various types of scanning exposure shown in FIGS. 12 to 15 can be implemented by the various types of scanning exposure apparatuses described with reference to FIGS.

Observation microscopes 6 and 117 in the above embodiment
Is to measure only the mask marks 12 and 151,
Dedicated observation microscope 1 for measuring wafer marks 22 and 152
19 may be configured without the intervention of the projection optical system 21.

In this case, as shown in FIG. 16, an off-axis observation microscope 119 is constructed so that the projection optical system 21 is adjacent to the projection optical system 21. This enables high-precision measurement of the wafer marks 22 and 152 regardless of the process.
High-precision correction of the non-linear shape misalignment between 21 and the transfer region 122 is realized.

Next, an embodiment of a device manufacturing method using the above-described exposure apparatus will be described. FIG. 17 shows a flow of manufacturing a semiconductor device (a semiconductor chip such as an IC or an LSI, or a liquid crystal panel or a CCD). Step 1
In (circuit design), a circuit of a semiconductor device is designed. Step 2 is a process for making a mask on the basis of the circuit pattern design. On the other hand, in step 3 (wafer manufacturing), a wafer is manufactured using a material such as silicon.
Step 4 (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by lithography using the prepared mask and wafer. The next step 5 (assembly) is called a post-process, and is a process of forming a semiconductor chip using the wafer prepared in step 4, and includes an assembly process (dicing and bonding).
It includes steps such as a packaging step (chip encapsulation). In step 6 (inspection), inspections such as an operation confirmation test and a durability test of the semiconductor device manufactured in step 5 are performed. Through these steps, a semiconductor device is completed and shipped (step 7).

FIG. 18 shows a detailed flow of the wafer process. Step 11 (oxidation) oxidizes the wafer's surface. Step 12 (CVD) forms an insulating film on the wafer surface. Step 13 (electrode formation) forms electrodes on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted into the wafer. Step 1
In 5 (resist processing), a photosensitive agent is applied to the wafer. Step 16 (exposure) uses the above-described exposure apparatus to print and expose the circuit pattern of the mask onto the wafer. Step 17 (development) develops the exposed wafer. In step 18 (etching), portions other than the developed resist image are removed. In step 19 (resist stripping), unnecessary resist after etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer.

By using the manufacturing method of this embodiment, it is possible to manufacture a highly integrated semiconductor device which has conventionally been difficult to manufacture.

[0073]

As described above, according to the present invention, the pattern of the reticle can be accurately superimposed on the pattern area on the wafer, so that a finer device can be manufactured.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing one embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration of a projection optical system in FIG. 1;

FIG. 3 is a plan view showing exposure shots and alignment marks on a wafer.

FIG. 4 is a block diagram showing a scanning control system of the apparatus shown in FIG.

FIG. 5 is a diagram illustrating a function regarding a relationship between a scanning position and a projection magnification.

FIG. 6 is a diagram illustrating a weighting function.

FIG. 7 is a diagram showing a filter function.

FIG. 8 is a flowchart illustrating an example of a magnification control method of the apparatus of FIG. 1;

FIG. 9 is a diagram showing a configuration of a projection optical system according to another embodiment of the present invention.

FIG. 10 is a schematic view showing another embodiment of the present invention.

FIG. 11 is a schematic view showing another embodiment of the present invention.

FIG. 12 is a view showing a state of scanning exposure using the apparatus of FIG. 11;

FIG. 13 is a view showing a state of scanning exposure using the apparatus of FIG. 11;

FIG. 14 is a view showing a state of scanning exposure using the apparatus of FIG. 11;

FIG. 15 is a view showing a state of scanning exposure using the apparatus of FIG. 11;

FIG. 16 is a schematic view showing another embodiment of the present invention.

FIG. 17 is a diagram showing a manufacturing flow of the semiconductor device.

FIG. 18 is a view showing the wafer process of FIG. 11;

[Explanation of symbols]

 M Reticle 6 Alignment measurement unit 18 Wafer 12 Reticle alignment mark 21 Projection optical system 22 Wafer alignment mark 206 Lens drive pressure supply source 211 Projection optical system calculator

Claims (8)

[Claims] 1. A scanning exposure apparatus comprising: a projection optical system for projecting a pattern of an original illuminated by exposure light onto a substrate; and scanning means for scanning the original and the substrate with respect to the exposure light. A scanning exposure apparatus comprising means for detecting a shape of a pattern region of an original plate and a shape of a transfer region of the substrate. 2. A scanning exposure apparatus comprising: a projection optical system for projecting a pattern of an original illuminated by exposure light onto a substrate; and scanning means for scanning the original and the substrate with respect to the exposure light. A scanning exposure apparatus, wherein a scanning direction of the substrate with respect to a scanning direction of the original is changed based on a shape of a pattern region of the original and a shape of a transfer region of the substrate. 3. A projection magnification of the projection optical system is changed based on each of the shapes.
3. The projection exposure apparatus according to claim 1. 4. A scanning exposure apparatus comprising: a projection optical system for projecting a pattern of an original illuminated by exposure light onto a substrate; and scanning means for scanning the original and the substrate with respect to the exposure light. A scanning exposure apparatus, wherein a projection magnification of the projection optical system is adjusted based on a shape of a pattern region of an original plate and a shape of a transfer region of the substrate. 5. The scanning exposure apparatus according to claim 3, wherein the projection magnification is changed during the scanning. 6. A scanning exposure apparatus comprising: a projection optical system for projecting a pattern of an original illuminated by exposure light onto a substrate; and scanning means for scanning the original and the substrate with respect to the exposure light. A scanning exposure apparatus, wherein a scanning magnification of the projection optical system is changed during scanning, and a scanning direction of the substrate is changed with respect to a scanning direction of the original plate. 7. The scanning exposure apparatus according to claim 1, wherein a scanning direction of the substrate with respect to a scanning direction of the original plate is changed during the scanning. 8. A device manufacturing method, comprising: exposing a substrate with a device pattern using the scanning exposure apparatus according to claim 1; and developing the exposed substrate.