JPH07183214A - Exposure method, scanning aligner and device manufacturing method using the aligner - Google Patents

Abstract

PURPOSE:To precisely overlap a pattern region on a substrate with an original plate pattern in the scanning aligner. CONSTITUTION:A pattern region on a substrate is precisely overlapped with an original plate pattern by changing the projection magnifying power of a projection optical system by shifting a lens of the system in the direction of an optical axis in the scanning step when the pattern region on a wafer is overlapped with a reticle pattern by projecting the pattern of the reticle 14 illuminated by exposure light from a light source 9 on a wafer 18 using the projection optical system 121 to scan the reticle 14 and the wafer 18 on the exposure light and the projection optical system.

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 type exposure apparatus and a device manufacturing method using the scanning type exposure apparatus, and in particular, semiconductor chips such as IC and LSI, liquid crystal elements, magnetic heads, 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 Demands for overlay accuracy of a reticle and a wafer when exposing a device pattern using a scanning type exposure apparatus are becoming more and more strict. For example, 64
For the manufacture of Mbit DRAM, the line width is 0.35μ
Since it is necessary to form a pattern of about m on the wafer, it is necessary to correct not only the positional deviation in the XYθ directions 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 of the reticle and the wafer during scanning. Since it was not possible to correct the local magnification error in the orthogonal direction, the pattern of the reticle could not be accurately overlaid 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 an exposure method, a scanning type exposure apparatus, and a device manufacturing method using the scanning type exposure apparatus, in which a pattern of an original plate can be accurately superimposed on a pattern area on a substrate. And to provide.

In the exposure method of the present invention, a pattern of an original plate illuminated with exposure light is projected onto a substrate by a projection optical system, and the original plate and the substrate are scanned with respect to the exposure light and the projection optical system. In the exposure method including, the projection magnification of the projection optical system is changed during scanning so that the pattern of the original plate is accurately superimposed on the pattern region on the substrate.

In a preferred mode of the exposure method of the present invention, the pattern of the original plate is formed on the projection optical system in a state where the projection magnification in the scanning direction of the projection optical system and the projection magnification in the direction orthogonal to the scanning direction are different from each other. Is projected onto the substrate by means of.

A preferred form of the exposure method of the present invention is to scan the original plate and the substrate so that the ratio of the scanning speeds of the original plate and the substrate substantially matches the projection magnification of the projection optical system in the scanning direction. Characterize.

In a preferred mode of the exposure method of the present invention, the projection magnification of the projection optical system is obtained as a function of the position in the scanning direction, and the projection magnification of the projection optical system is changed during scanning according to the function. Is characterized by.

A scanning type exposure apparatus using the exposure method of the present invention comprises scanning means for scanning the original plate and the substrate with respect to the exposure light and the projection optical system, and the substrate with respect to an alignment mark of the original plate. It has a position shift detecting means for detecting the position of the alignment mark via the projection optical system, and a magnification control means for changing the projection magnification of the projection optical system during scanning according to the detection result by the position shift detecting means. It is characterized by

According to one aspect of the scanning type exposure apparatus of the present invention, in the scanning type exposure apparatus, the scanning means is controlled so as to change the ratio of the scanning speeds of the original plate and the substrate according to the projection magnification of the projection optical system. It is characterized by comprising scanning control means.

According to one aspect of the scanning type exposure apparatus of the present invention, in the scanning type exposure apparatus, there is provided position detection means for detecting a position in the scanning direction of the original plate and / or the substrate, and the magnification control means is It is characterized in that the projection magnification of the projection optical system is changed according to the detection result by the position shift detection means and the detection result by the position detection means.

In one mode of the scanning type exposure apparatus of the present invention, the magnification control means of the scanning type exposure apparatus uses the detection result of the positional deviation detection means to set the projection magnification of the projection optical system to the position in the scanning direction. And a projection magnification of the projection optical system is changed during scanning according to the function.

In one mode of the scanning exposure apparatus of the present invention, the magnification control means of the scanning exposure apparatus scans the projection magnification of the projection optical system according to a function obtained by multiplying the function by a weighting function. It is characterized by changing inside.

An embodiment of the scanning type exposure apparatus of the present invention is characterized in that, in the scanning type exposure apparatus, the positional deviation detecting means detects the positional deviation before exposure.

An embodiment of the scanning type exposure apparatus of the present invention is characterized in that, in the scanning type exposure apparatus, the positional deviation detecting means detects the positional deviation during exposure.

According to another aspect of the scanning type exposure apparatus of the present invention, in the scanning type exposure apparatus, the projection optical system includes a movable lens that is movable in the optical axis direction, and the magnification control means moves the movable lens. Thus, the projection magnification of the projection optical system is changed.

In one mode of the scanning type exposure apparatus of the present invention, the movable lens of the scanning type exposure apparatus has a cylindrical lens or a cylindrical mirror.

According to another aspect of the scanning exposure apparatus of the present invention, in the scanning exposure apparatus, the projection optical system includes a mirror having a variable curvature, and the magnification control means changes the curvature of the mirror to cause the projection. The feature is that the projection magnification of the optical system is changed.

According to one aspect of the scanning type exposure apparatus of the present invention, the mirror of the scanning type exposure apparatus is a plate-shaped mirror having a surface as a reflecting surface, and the magnification control means changes the curvature of the mirror. It is characterized by having a pressure changing means for changing the pressure difference between the atmosphere on the front side and the atmosphere on the back side of the mirror.

According to one aspect of the scanning type exposure apparatus of the present invention, the pressure changing means of the scanning type exposure apparatus determines an inflow amount and an outflow amount of a fluid accumulated in a closed space provided on the back side of the plate-shaped mirror. It is characterized by having a changing means.

An embodiment of the scanning type exposure apparatus of the present invention is characterized in that the threshold value is variable.

In one aspect of the scanning type exposure apparatus of the present invention, in the scanning type exposure apparatus, the device manufacturing method of the present invention includes the step of transferring the device pattern of the original plate onto the substrate using the scanning type exposure apparatus. It is characterized by

[0023]

FIG. 1 is a schematic view of a step-and-scan type projection exposure apparatus for device manufacturing according to an embodiment of the present invention. In the present exposure apparatus, during scanning exposure, the wafer stage 23 is servo-locked by tracking control with respect to the mask stage 14 which is caused to perform scanning operation with respect to an absolute coordinate system, that is, a mechanical origin 24 on the exposure apparatus. 15a and 15b are the scanning directions of the mask stage 14 and the wafer stage 27 during scanning exposure, respectively. An exposure beam 20 that exposes an exposure area 19 on a wafer 18, which is a photosensitive substrate, is light emitted from a light source 9 and shaped into an elongated shape by a slit 11 via an optical system 10.
The opening width of the slit 11 can be changed according to the scanning speed of the wafer stage 23 and the reticle stage 14 and the intensity of the exposure beam 20. 12L, 12R, 2
2L and 22R are alignment mark groups arranged on the left and right sides of the exposure area on the reticle M and the wafer 18, respectively. The alignment mark groups 12 and 22 are both shown in FIG.
It is composed of a lattice pattern as shown in FIG. With these lattice patterns, the relative displacement of the reticle-wafer in the XY directions can be detected, and the relative displacement of the θ direction, that is, the rotational displacement can also be detected. The relative displacement between the wafer 18 and the reticle M is measured by the alignment measuring 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 mark groups 12 and 22 on the reticle M and the wafer 18, and is reflected and diffracted by the alignment mark groups 12 and 22. The measurement beam 8 that has returned from the optical path of the projection beam through the beam splitter 7 is deflected from the optical path of the projection beam and reaches the photosensor 1. The photosensor 1 converts the alignment measurement destination (interference light) into an electrical signal, and the preamplifier 2 amplifies the electrical signal.
That is, the relative displacement signal 4 is generated.

Reference numerals 27 and 28 are laser interferometers for measuring the position coordinates of the mask stage and the wafer stage, respectively. The mask stage 14 is moved by the laser interferometer 27 to X.
Its position is measured and controlled in the axial direction. The wafer stage 23 is moved by the laser interferometer 28 into X, Y, θ,
The position is measured and controlled in the ω _x and ω _y directions. 1
Reference numerals 7a to 17c are linear motors, which generate thrust in the X, Y, and θ directions for driving the wafer stage 23. The wafer stage 23 is a surface plate 25 that also serves as a plane guide.
The wafer stage 23 is mounted with a tilt stage (not shown) composed of three piezoelectric elements so as to hold the wafer 18. With these configurations, the wafer stage 23 has highly accurate positioning performance that is not easily affected by vibration and friction transmitted from the outside. Reference numeral 16 is a linear motor for driving the mask stage 14. Like the wafer stage 23, the mask stage 14 is also driven in a state of being supported by being floated by a small amount from 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 TV alignment scope for pre-alignment,
Reference numeral 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 previously formed on the wafer 18 is used as the pre-alignment scope 2
The image is picked up at 6 and the 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 which has completed the pre-alignment based on this position shift signal enters the scanning exposure process. The lattice pattern of the alignment marks on the reticle M and the wafer 18 is drawn on the exposure shot at a pitch of about 10 μm (see FIG. 3), and the amount of positional deviation (± 5μ
If there is a deviation of m) and alignment scanning exposure is performed during exposure, the alignment measurement unit 6 cannot perform accurate alignment measurement. 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 the relative positional deviation amount, so that there is a deviation between the marks of one pitch or more in the lattice pattern. This is because it becomes impossible to distinguish if there is. Therefore, the pre-alignment accuracy by the pre-alignment scope is set to ± 1 μm, and the relative positional deviation amount between the image of the reticle M and the exposure shot on the wafer 18 after pre-alignment is specified to be ± 5 μ or less including other error factors. is doing.

FIG. 2 shows the configuration of the projection optical system 21 shown in FIG. In the figure, 201a, 201b and 201c
Is a lens that constitutes the projection optical system. 202a, 20
2b and 202c are lenses 201a and 201c, respectively.
The lens barrel holds b and 201c. Also, 212
Is an air bearing guide for guiding the lens barrel 202b, 21
Reference numeral 3 denotes a static pressure conduit for applying a static pressure to the air bearing guide 212, 204 a driving pressure conduit for supplying a pressure for driving the lens barrel 202b, 206 a driving pressure supply source, and 215 a lens barrel 202.
It is a spring that supports b. Reference numeral 216 is a piezo element that drives the entire projection optical system, 207 is a piezo element drive circuit, and 210
Is an air sensor nozzle which is fixed to the lower end of the projection optical system and measures the distance from the wafer 18, 209 is a pneumatic line for the air sensor, and 208 is a converter which converts 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 air back pressure is used by the air sensor nozzle 12 to detect the distance between the projection optical system 21 and the wafer 18. This distance value is compared with a predetermined target value, and the piezo element 216 is driven so that the distance to the wafer 18 matches the target value, and the focusing operation is completed. 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 this relative shift amount becomes zero.

FIG. 3 is a diagram showing the scanning control system of this embodiment. Reference numeral 211 denotes a projection optical system calculator, which controls the projection magnification of the projection optical system 21 so that the magnification target value 408 is instructed by a host controller (described later), and at the same time corrects defocus. Reference numeral 401 is an alignment system computing 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. Reference numeral 402 denotes a wafer stage control system computing unit, which is an X, Y, θ, ω _x , ω _y component of the wafer stage 23 measured by the laser interferometer 28 and a Z component measured by the gap sensors 208 to 210 of FIG. The operation amount is set to the driver 407 that supplies the drive power to each actuator so that the position coordinates of the target values become the target values 410a, 410b, 410c (only the X, Y, and θ components are shown) instructed by the host controller. Output. Four
Reference numeral 03 denotes a mask stage control system calculator, which outputs a manipulated variable to the driver 407 so that the X component position coordinate measured by the laser interferometer 27 becomes the target value X _M , similarly to the wafer stage control system 402. . Further, the wafer stage control system arithmetic unit 402 and the mask stage control system arithmetic unit 40
3 is a laser interferometer 2 when accelerating both stages before starting the tracking scanning exposure using the alignment measurement signal for feedback and when tracking is not performed because the alignment measurement signal cannot be detected satisfactorily.
It has a high-speed communication path 415 for scanning the reticle and the wafer with the projection magnification ratio of the projection optical system 21 depending on the measured value of 7. Reference numeral 404 is a scanning exposure arithmetic processing device which is a host controller. The scanning exposure arithmetic processing unit 404 performs arithmetic processing to obtain 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, and 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 fixed time, for example, every 0.5 msec. Further, in the above calculation process, the magnification target value 408 is calculated as a function for the alignment detection value or a value quoted from the data table. The same function or data table is used to correct magnification reading errors from the alignment signal caused by the local shape of the pattern formed on the wafer, the tendency of the arrangement, the difference from the ideal shape of the alignment mark, and the like. is there. These function tables can be changed for each process and for each reticle, all are stored in the storage device 405, and are read into the scanning exposure calculation processing device 404 via the communication path 414 as needed.

FIG. 3A shows shots and alignment marks 22 on the wafer 18 exposed in this embodiment, and the displacements in the X direction from the reticle image are measured on both sides of the circuit pattern 301. Lattice patterns 22LX and 22RX are arranged in parallel, and lattice patterns 22LY and 22RY for measuring the shift in the Y direction are arranged in parallel with the pattern. And individual grid patterns 22LX, 22LY, 22RX, 22R
The detected values of the shift amount in Y are ΔX _L , ΔY _L , ΔX _R , Δ
If Y _R is set, the correction amount of the translational component can be obtained in principle by the following equation.

(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 Y-direction alignment pattern 22LY, 22
Shows the distance dimension between RY. Mdx and Mdy are parameters such as a constant or a magnification for correcting an error of the average positional deviation amount in the circuit pattern 301 that occurs when a magnification change occurs within the exposure angle of view, an alignment value of a peripheral exposure shot, a magnification value, and the like. Is a function of. On the other hand, the correction amount of the magnification component is the k-th alignment measurement value ΔX _L (k), ΔY _L (k), ΔX _R (k), Δ under the fixed time interval T.
If Y _R (k) is sampled, it can be obtained by the following equation.

[0030]

[Outer 1]

Here, when calculating the X-direction correction magnification, α is a coefficient for weighting and incorporating it in the magnification correction value because one of the mark 22LX and the mark 22RX is redundant. Vst 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 point. Therefore, the projection magnification of the projection optical system 21 corrected according to the correction magnification obtained by the equations (4) and (5) is matched with 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 equation (5) is changed to (kn) (n
Is an integer).

Further, when the sampling interval T becomes smaller, the S / N ratio of the alignment measurement signal becomes lower, which causes a larger variation in mx (k) and my (k). In the present embodiment, the magnification correction value obtained for each sampling is not immediately output to the projection optical system computing unit 211, but is output after averaging processing using a weighting function. FIG. 6 shows an example of the weighting function. The shape of the envelope 601 of the weighting function W _k can be changed according to the size of the opening of the slit 11 and the response characteristic of the projection optical system 21 with respect to the command magnification. or,

[0033]

[Outside 2] There is a relationship.

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

[0035]

[Outside 3]

If a weighting function W (k) having an 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 becomes the input of the filter function F shown in FIG. 7, and the output of the filter function F finally becomes the magnification target value ΔM to be passed to the projection optical system computing unit 211.

ΔM = F _x {MY (k)} (10) In this embodiment, the magnification target value (relative magnification value) obtained for each sample time by the above equation (10) is immediately calculated by the projection optical system calculator 211. Is input to the projection optical system calculator 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 correction magnification value of the Y component. X
The change in magnification in the direction can be performed by changing the speed ratio of the scanning speed V _M of the mask stage and the scanning speed V _st of the wafer stage. However, the slit width d of the exposure area
Has a value larger than 0, a pattern image is formed on the projection surface while passing through the exposure slit by the difference between the projection magnification N _op of the projection optical system and the scan speed ratio V _st / V _M , and δ _x is represented by the following formula (1).
However, the resolution deteriorates.

(Distance moving on projection plane) δ _x = | N _op −V _st / V _M | · d (11) Therefore, in the present embodiment, δ _x does not exceed a certain threshold value. V _st is finely adjusted, and basically V _st / V _M is operated so as to follow changes in N _op .

The filter function shown in FIG. 7 is caused by the local shape of the pattern formed on the wafer described with reference to FIG. 4, the tendency of arrangement, the difference in the shape of the alignment mark and the circuit pattern, and the like. This is to correct the magnification reading error from the alignment signal that occurs. F _x (M
The input parameters of X) and F _x (MY) can have other than the complementary magnification target values M _X and M _Y.

When the projection magnification changes during the passage of the slit for scanning exposure, even if N _op = V _st / V _M (12) is satisfied, the pattern image on the projection surface is (13) below.
The degradation of resolution occurs due to the movement of δ _x1 shown in the equation.

Δ _x1 ≈V _M · α _op · t ² (13) where α _op is the magnification per unit time when it is assumed that the magnification of the projection optical system 21 increases in proportion to the passage of time. It is an increase. There is an upper limit of the allowable value for the deterioration of the resolution due to the change of the projection magnification. Therefore, in this embodiment, F
_{When the} rate of change of _x {MY (k)} in the sample time interval is small, the relative magnification value is determined by the relationship of equation (10), but when the rate of change is large, the range of change is limited and the relative magnification value is limited. Is output. The contents of this process are shown in FIG.
Shown in.

In FIG. 8, a relative magnification value F sequentially obtained from alignment measurement values measured at each sample time.
_{For x} {MY (k)}, the difference value δF _x is obtained with respect to the relative magnification value ΔM (k−1) output to the projection optical system 21 last time (803). Subsequently, it is determined whether δF _x is greater than the absolute value of the threshold value a derived from the specification defining the resolution deterioration (804). When it does not exceed (808), the process proceeds to step 806, and when it exceeds (801), the upper limit a allowed as the difference value is the above difference value.
Alternatively, the lower limit is replaced with -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) output to the projection optical system 21 last time 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 can be used in the next calculation process. In step 802, the argument indicating the sampling order of parameters is incremented for the next calculation.

Thus, in this embodiment, the projection optical system 2
By limiting the magnification change of 1, the deterioration of resolution
It is intended to stay within the regulations. Step 8
By changing the value of the parameter a in 04
The degree of freedom for changing the projection magnification of the system 21 can be changed.
Yes, the user can set the resolution according to lot or process
Priority scanning exposure or magnification correction (local alignment correction
Positive) priority scanning exposure can be adjusted. On the other hand
ΔF as an application of the present invention in addition to the flow shown in FIG. _xTo
How to limit using a continuous function without a threshold
And so on. Furthermore, the flow shown in FIG.
In addition to the form in which the wafer is exposed while measuring the
A method of performing scanning exposure after performing alignment measurement for
Global alignment method and pre-scan method
It can also be applied to inspection exposure apparatuses.

FIG. 9 shows a block diagram of the projection optical system 21 in another embodiment of the present invention. 201 to 216 are the same members as the constituent members described in 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 piezoelectric elements 90
A minute drive is performed in the optical axis direction by 3, 904.
Piezo elements 903 and 904 are drivers 901 and 901, respectively.
It is controlled under the command of the projection optical system calculator 211 via 902. The cylindrical lenses 905a and 905b are shown in FIG.
Has a power in the Y direction in the other lens 201
The reduction magnification (1/4 in this embodiment) that is uniformly obtained by ac is multiplied by the Y direction bias magnification of several + ppm. The lenses 201a to 201c can change the magnification equally in the XY directions by driving the lens 201b and the lens barrel in the optical axis direction as clarified in the description of FIG. Therefore, the rotationally symmetric lenses 201a-
The X-direction and Y-direction demagnification factors in the vicinity of the projection magnification value of 1/4 can be arbitrarily set by combining the XY-direction equal magnification change amount by c and the Y-direction demagnification factor change amount by the cylindrical lenses 905a and 905b. It is configured to be able to. The relative magnification value (magnification target value) ΔM 408 input to the projection optical system calculator 211 has two parameters of the X component and the Y component in this embodiment. In addition, the filter function described in FIG.
The algorithm shown in 1) is applied to this embodiment in exactly the same way as the previous embodiment. The scanning speed of the wafer stage 23 is finely adjusted substantially according to the change of the X-direction projection magnification of the projection optical system 21. Further, instead of the cylindrical lenses 905a and 905b, a cylindrical mirror is arranged on the optical path of the projection optical system 21, and the relative position or curvature of the mirror with respect to other optical systems (an example of finely adjusting the curvature in the third embodiment is presented. ) Can be finely adjusted.
In any case, a similar 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.

Also, this configuration can be applied to a scanning exposure apparatus of a global alignment method and a pre-scan method, in which an exposure method of exposing a wafer while performing alignment measurement is performed, and then scanning exposure is performed after performing alignment measurement in advance. Is possible.

[Other Embodiments] FIG. 10 shows a third embodiment of the present invention.

In FIG. 10, members having the same numbers as those in FIG. 1 perform the same functions as the members explained in FIG. A mirror 1001 has a closed space 1002 on the back side of the reflecting surface. A fluid is enclosed in the closed space 1002, and the fluid introduction path 10
It is configured to generate a differential pressure with respect to the external atmosphere by pouring or discharging a fluid from 03. Due to the generation of the differential pressure, pressure is applied to the mirror 1001 in a direction perpendicular to the mirror surface, causing slight distortion, and the differential pressure becomes 0
The magnification of the image created by the reflected light changes slightly compared to when it was. Reference numeral 1004 is a valve unit that controls the amount of fluid flowing into the closed space, and 1005 is a controller that controls the valve unit. 1/4 for 1006 and 1007
The wave plate 1008 is a beam splitter. 1009
Is a light-receiving lens for picking up an alignment signal, 1013
Is an alignment signal processing device. Reference numeral 1010 is a mirror, and 1011 is an objective lens group. Objective lens group 10
Reference numeral 11 is controlled by the lens control device 1012, and corrects defocusing 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.
The exposure light transmitted through the reticle is reflected by the mirror 1001, and the quarter wave front plate 1006 and the beam splitter 10 are included.
08, 1/4 wave front plate 1007 is transmitted, and the mirror 1010
Is reflected at. 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, this embodiment can also measure the magnification during the scanning exposure and correct the magnification in real time, as in the first embodiment. 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 is provided with at least one cylindrical lens, thereby providing a demagnification function in the X direction or the Y direction. Is also possible.

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

1. By locally 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. The displacement of the projection pattern is minimized by making the scanning speed of the stage follow the magnification change in the scanning direction of the projection optical system.

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

4. An alignment measurement signal generated according to a process, a circuit pattern, or a position is obtained by adding a conversion based on a function or a data table input in advance to a correction magnification value obtained from the alignment measurement signal to obtain a magnification value of the projection optical system 21. It has become possible to correct the difference between the projection magnification value obtained from the above and the magnification value for aligning the actual pattern.

5. A closed space provided on the back side of the mirror is filled with fluid, and by controlling the amount of fluid, a differential pressure is generated between the closed space and the external atmosphere, and the mirror is slightly distorted to realize a slight change in projection magnification. did.

6. By multiplying a correction magnification value obtained from a plurality of alignment measurement data groups necessary for magnification calculation processing by a weighting function to obtain a local correction magnification value, S / N of alignment measurement signal values, noise, etc. It is possible to calculate a stable correction magnification value that is not easily affected.

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

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 for deteriorating the matching state 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 processing such as oxide film formation, ion implantation and etching. This deformation mainly appears as a change in magnification of the pattern during projection exposure.

The degree of deformation of the wafer is often different in the crystal axis direction of the substrate and in the other direction, and the magnification and orthogonality are not uniform. Further, since the amount of enlargement / reduction due to heat changes depending on the distance from the center of the wafer, the amount of deformation of the pattern near the center of the wafer is different from the amount of deformation of the pattern near the outer periphery, and the wafer has a non-linear shape. There are various patterns.

Moreover, in the semiconductor manufacturing process, all the steps are not always carried out by the same projection exposure apparatus. When it is attempted to align the mask pattern with the pattern exposed in the previous step by another apparatus, the projection optical system is used. If the matching of the distortion aberrations between them and the matching of the bending (in a bow shape) in the scanning direction of the scanning exposure system are not performed, it is recognized as a non-linear shape shift of the substrate pattern.

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

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 on 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, which is an exposure substrate, is supported by the apparatus main body by a wafer stage 23 whose XY drive 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.
The slit-shaped exposure light region 116 from an illumination system (not shown) is placed at an optically conjugate position via the wafer and forms a pattern image of the mask M on the wafer with a size corresponding to the projection magnification of the projection optical system 21. 3 is projected. The scanning exposure is performed by using the exposure light 116 for the mask stage 14 and the wafer stage 2.
The scanning is performed in the X direction at a speed ratio according to the projection magnification of the optical system 21. The entire surface of the pattern area 21 on the mask 1 is transferred to the transfer area 22 on the wafer 3. In this figure, the projection optical system 2 composed of a refraction element such as a lens is shown. However, a projection optical system in which a reflection element and a refraction element as shown in FIG. As shown in this figure, the reduction may be other than the same size. Further, the outer shape of the wafer 18 is not defined in this figure, and when the reduction projection optical system is used, the wafer 1
8 has a plurality of transfer areas 22.

The alignment state 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 means 1103 to the arithmetic processing circuit 1102 and has a shape corresponding to the position information of the mask mark 151. Remembered in. By repeating this measurement for the plurality of mask marks 151 by controlling the mask interferometer (not shown) and driving the mask stage 14, the measurement is repeated.
The drawing state of the original image of the mask M will be known. The mask mark 151 is drawn at the same time as the pattern area 121 on the mask M, and represents the drawing origin, drawing magnification, and drawing orthogonality of the pattern area 121. When measuring the drawing magnification and drawing orthogonality, the mask mark 151 should be at least 3
More than one mask mark 151 is required, and more mask marks 151 are required to measure the non-linear component of the drawing error.

Further, in this figure, the mask mark 151 is arranged so as to sandwich the pattern area 121, but there is no problem even if it is arranged in the pattern area 121, and the shape is not limited to the cross shape. The actual element pattern drawn at 121 may be measured as a mask mark.

Next, the wafer mark 152 arranged around the transfer region 122 of the wafer 18 is observed with the observation microscope 117.
Thus, the image is observed 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.
It is an object that corrects the chromatic aberration of No. 1 and is preferably arranged at a position where it 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 generate the wafer mark 152.
When observing, the correction optical element 8 becomes unnecessary.

A plurality of wafer marks 1 arranged by the observation microscope 117 around the transfer area 122 of the wafer 18.
52 is observed, and the signal from the microscope 117 is processed by the mark detection means 1101 as in the case of the mask mark 151, and the arithmetic processing circuit 1 is used as the position information of the wafer mark 152.
Sent to 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 means 1103 to the arithmetic processing circuit 1102 and has a shape corresponding to the position information of the wafer mark 152. Remembered in. The shape of the transfer area 122 on the wafer 18 can be determined by sequentially repeating this measurement for the plurality of wafer marks 152 by controlling the wafer interferometer (not shown) while driving the wafer stage 23. 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 as including the variation of the projection magnification of 1
17 and the mark detection means 1101.

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

Note that at least three wafer marks 152 are required to measure the magnification and orthogonality as the shape of the transfer area 122.
More wafer marks 152 are required. Further, the location and shape are not limited to those in the present embodiment, and 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 area 122 on the wafer 18 causes an error in the exposure transfer. This error is the arithmetic processing circuit 11 that stores the error during scanning exposure.
02, the drive control unit 1103 is instructed to perform a scanning drive method for correcting an exposure transfer error, and scanning exposure is performed while controlling the positions of the mask stage 4 and the wafer stage 5 using a laser interferometer (not shown), and the projection optical system is used. The pattern area 1 is corrected by driving some optical elements in the system 21.
21 is the transfer area 12 on the wafer 18 with good alignment accuracy.
Transferred to 2.

As a first example, consider a case where a non-linear orthogonality error occurs in the pattern area 121 and the transfer area 122, as shown in FIG. Although the transfer area 122 is deformed in FIG. 12A,
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, according 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 scanning start sides of 2 are 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 an 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 FIG. 12 (B) → (C). At this time, the orthogonality error θ is θ1,
When θ2 and θ3 are not constant values but continuously change, the amount of drive in the oblique direction of the mask stage 14 or the wafer stage 23 is also changed accordingly, so that the nonlinear orthogonal error can be corrected. . As a result, the pattern area 121 can be superposed and transferred onto the transfer area 122 with high accuracy.

As a second example, consider a case where a nonlinear magnification error occurs in the pattern exposure area 121 and the transfer area 122 in the scanning exposure direction, as shown in FIG. Figure 1
In FIG. 3A, the transfer area 122 is deformed, but it is a relative problem even when the pattern area 121 is deformed, and it is considered that the following correction scanning exposure is performed. good.

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 122 are exposed to the exposure light 16 as shown in FIG.
Align the scanning start sides of. Next, the arithmetic processing circuit 1102
To drive control means 1103, scanning direction magnification error βx
As a scanning driving method for correcting (βx = 1wx / 1mx 1wx: inter-mark distance in the scanning direction of the transfer region 122 1mz: inter-mark distance in the scanning direction of the pattern region 121), the mask stage 14 or the wafer stage 23 is magnified in the scanning direction. An instruction is issued to drive while changing the relative speed by the amount of error βx, and the position is controlled using a laser interferometer (not shown), and the exposure light 16 is moved as shown in FIG. 13 (B) → (C). . At this time, the scanning direction magnification error β
When x is not a constant value such as βx1 and βx2 but continuously changes, the relative speed change amount of the mask stage 14 or the wafer stage 23 is also changed accordingly, thereby changing the nonlinear scanning direction. Magnification error 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 the case where a non-linear magnification error occurs in the pattern area 121 and the transfer area 122 in the non-scanning exposure direction, as shown in FIG. Although the transfer area 122 is deformed in FIG. 14A, it is a relative problem even when the pattern area 121 is deformed, and it is considered that the following correction scanning exposure is performed. Good.

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 sides of 2 are aligned with each other. Next, from the arithmetic processing circuit 1102 to the drive control means 1103, the non-scanning direction magnification error βy (βy = 1wy / 1my 1wy: transfer area 1
As a scan driving method for correcting the mark-to-mark distance 22 in the non-scan direction 1 my: the distance between the marks in the pattern area 121 in the non-scan direction, the optical element in the projection optical system 21 is driven by the non-scan direction magnification error βy. From the mask stage 14
Or, an instruction is issued to drive the wafer stage 23,
While controlling the position using a laser interferometer (not shown),
The exposure light 16 is moved as shown in FIG. At this time, the non-scanning direction magnification error βy is βy1, βy2.
If it changes continuously instead of a constant value like
In accordance therewith, the driving amount of the optical element for correcting the optical magnification in the projection optical system 21 is also changed in accordance with the scanning exposure driving of the mask stage 14 or the wafer stage 23, so that a nonlinear magnification error in the non-scanning direction is obtained. Can also be corrected. As a result, the pattern area 121 can be superposed and transferred onto the transfer area 122 with high accuracy.

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

Therefore, the pattern area 121 and the transfer area 1
It is possible to superimpose all 22 non-linear shape deviations with high accuracy.

As described above, the forms of the various scanning exposures shown in FIGS. 12 to 15 can be carried out by the various scanning type exposure apparatuses described in FIGS.

The 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 the wafer marks 22, 152
19 may be configured without the projection optical system 21.

Here, as shown in FIG. 16, the off-axis observation microscope 119 was constructed with the projection optical system 21 adjacent to each other. This enables highly accurate measurement of the wafer marks 22, 152 regardless of the process, and the pattern area 1
Highly accurate correction of the non-linear shape deviation between the transfer area 21 and the transfer area 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 (semiconductor chip such as IC or LSI, liquid crystal panel, CCD or the like). Step 1
In (Circuit design), the circuit of the semiconductor device is designed. In step 2 (mask manufacturing), a mask having the designed circuit pattern is manufactured. 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 the lithography technique using the mask and the wafer prepared above. The next step 5 (assembly) is called a post-process, which is a process of forming a semiconductor chip using the wafer manufactured in step 4, and an assembly process (dicing, bonding),
It includes steps such as packaging (chip encapsulation). In step 6 (inspection), the semiconductor device manufactured in step 5 undergoes inspections such as an operation confirmation test and a durability test. Through these steps, the semiconductor device is completed and shipped (step 7).

FIG. 18 shows the detailed flow of the wafer process. In step 11 (oxidation), the surface of the wafer is oxidized. In step 12 (CVD), an insulating film is formed on the wafer surface. In step 13 (electrode formation), electrodes are formed on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted in the wafer. Step 1
In 5 (resist processing), a photosensitive agent is applied to the wafer. In step 16 (exposure), the circuit pattern of the mask is printed and exposed on the wafer by the exposure apparatus described above. In step 17 (development), the exposed wafer is developed. In step 18 (etching), parts other than the developed resist image are removed. In step 19 (resist stripping), the resist that is no longer needed 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 been difficult to manufacture in the past.

[0085]

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

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a projection optical system in FIG.

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

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

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

FIG. 6 is a diagram showing a weighting function.

FIG. 7 is a diagram showing a filter function.

8 is a flow chart showing an example of a magnification control method of the apparatus of FIG.

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.

12 is a diagram showing a state of scanning exposure using the apparatus of FIG.

13 is a diagram showing a state of scanning exposure using the apparatus of FIG.

14 is a diagram showing a state of scanning exposure using the apparatus of FIG.

FIG. 15 is a diagram showing a state of scanning exposure using the apparatus of FIG.

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

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

FIG. 18 is a diagram 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 driving pressure supply source 211 projection optical system calculator

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location 7352-4M H01L 21/30 515 F 7352-4M 516 7352-4M 520

Claims (18)

[Claims] 1. An exposure method comprising: projecting a pattern of an original plate illuminated with exposure light onto a substrate by a projection optical system, and scanning the original plate and the substrate with respect to the exposure light and the projection optical system. An exposure method characterized in that the pattern of the original plate is accurately superimposed on the pattern area on the substrate by changing the projection magnification of the projection optical system during scanning. 2. The pattern of the original plate is projected onto the substrate by the projection optical system in a state where the projection magnification of the projection optical system in the scanning direction and the projection magnification in the direction orthogonal to the scanning direction are different from each other. The exposure method according to claim 1, wherein 3. The original plate and the substrate are scanned such that the ratio of the scanning speeds of the original plate and the substrate is substantially equal to the projection magnification of the projection optical system in the scanning direction. Exposure method. 4. The projection magnification of the projection optical system is obtained as a function of the position in the scanning direction, and the projection magnification of the projection optical system is changed during scanning according to the function. 2 exposure method. 5. A scanning type exposure apparatus using any one of the exposure methods according to claim 1; scanning means for scanning the original plate and the substrate with respect to the exposure light and the projection optical system; and the original plate. Position detection mark for detecting the position of the alignment mark of the substrate with respect to the alignment mark of the substrate via the projection optical system, and the projection magnification of the projection optical system during scanning according to the detection result of the position displacement detection device. And a magnification control means for changing the scanning magnification. 6. The scanning control means for controlling the scanning means to change the ratio of the scanning speeds of the original plate and the substrate according to the projection magnification of the projection optical system in the scanning direction. Scanning exposure equipment. 7. A position detecting means for detecting a position of the original plate and / or the substrate in a scanning direction, wherein the magnification control means detects a detection result of the position deviation detecting means and a detection result of the position detecting means. 7. The projection magnification of the projection optical system is changed according to
Scanning exposure equipment. 8. The magnification control means obtains the projection magnification of the projection optical system as a function of the position in the scanning direction by using the detection result of the positional deviation detection means, and the projection of the projection optical system according to the function. 8. The scanning exposure apparatus according to claim 7, wherein the magnification is changed during scanning. 9. The scanning exposure apparatus according to claim 8, wherein the magnification control means changes the projection magnification of the projection optical system during scanning in accordance with a function obtained by multiplying the function by a weighting function. . 10. The scanning exposure apparatus according to claim 7, wherein the positional deviation detecting means detects the positional deviation before exposure. 11. The scanning type exposure apparatus according to claim 7, wherein said positional deviation detecting means detects positional deviation during exposure. 12. The projection optical system comprises a movable lens movable in the optical axis direction, and the magnification control means changes the projection magnification of the projection optical system by moving the movable lens. Item 5. The scanning exposure apparatus according to item 5. 13. The scanning exposure apparatus according to claim 12, wherein the movable lens has a cylindrical lens or a cylindrical mirror. 14. The scanning according to claim 5, wherein the projection optical system includes a mirror having a variable curvature, and the magnification control means changes the projection magnification of the projection optical system by changing the curvature of the mirror. Type exposure equipment. 15. The mirror is a plate-shaped mirror having a reflecting surface, and the magnification control means changes the pressure difference between the atmosphere on the front side and the back side of the plate-shaped mirror to change the curvature of the mirror. 15. The scanning exposure apparatus according to claim 14, further comprising a pressure changing unit. 16. The scanning exposure according to claim 15, wherein the pressure changing means has a means for changing an inflow amount and an outflow amount of a fluid accumulated in a closed space provided on the back side of the plate-shaped mirror. apparatus. 17. The scanning type exposure apparatus according to claim 5, wherein the magnification control means changes the magnification of the projection optical system so as not to exceed a predetermined threshold value regarding the amount of change in magnification within a predetermined time. 18. A device manufacturing method comprising the step of transferring a device pattern of an original plate onto a substrate by using the scanning type exposure apparatus according to claim 5.