JPH0851070A - Light exposure method - Google Patents

Abstract

PURPOSE:To dispense with a process through which the amount of positioning correction is previously obtained by a test exposure by a method wherein a projection optical system is corrected on image formation characteristics first and furthermore corrected on image formation characteristics and positioning errors which occur between a negative plate and the board on the basis of the amount of shrinkage of a board where a first image is projected for light exposure, and a second image is projected onto the board overlapping the first image for exposure. CONSTITUTION:Marks are provided onto a pattern located on a negative plate 20 at prescribed positions, and the positioning errors of the negative plate 20 are corrected and a projection optical system 17 is corrected on image forming characteristics corresponding to the amount of deviation of the positions of the images of the marks projected onto a coordinates system C1 from the designed positions of the images. Then, the first image of a pattern is projected onto a board 11 for light exposure, the amount of shrinkage of the board 11 is obtained, and not only the projection optical system 17 is corrected on image forming characteristics but also the positioning of the negative plate 20 to the board 11 is corrected on the basis of the above amount of deviation. Then, the second image of the pattern is projected onto the board 11 overlapping or joining the first image for light exposure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure method, and is suitable for application to, for example, an exposure apparatus which projects and exposes a liquid crystal display or a semiconductor pattern onto a substrate.

[0002]

2. Description of the Related Art Conventionally, as a projection exposure apparatus for manufacturing a liquid crystal display (LCD), after a pattern formed on a reticle is exposed on a predetermined area of a photosensitive substrate, the photosensitive substrate is stepped by a certain distance, and then the reticle is re-formed. There is a so-called step-and-repeat method in which the exposure of the pattern is repeated.

Such a projection exposure apparatus is mounted on a reticle stage or a substrate stage that moves the reticle in a plane perpendicular to the optical axis of the projection lens in order to accurately align the reticle and the photosensitive substrate. A substrate stage controller is provided to position and control the photosensitive substrate in a plane perpendicular to the optical axis of the projection lens, and the projection magnification of the projection lens is set to project the pattern on the reticle onto the photosensitive substrate at a predetermined magnification. A magnification controller for controlling is provided. The position of the reticle with respect to the optical axis of the projection lens changes each time the reticle is placed on the reticle stage. This change (shift) in position is corrected by the relative movement of the reticle and the photosensitive substrate during exposure.

Further, the exposure of the second layer is usually performed by superposing it on the pattern of the previous layer (first layer), and when the photosensitive substrate is placed on the substrate stage at that time, the first layer is exposed. Therefore, the photosensitive substrate is placed at a position different from the position when the photosensitive substrate is placed on the stage for exposing. This change in position is obtained by detecting the alignment mark on the first layer using an alignment microscope provided in a predetermined positional relationship with the optical axis of the projection lens. Then, when the second layer is exposed, the reticle and the photosensitive substrate are moved relative to each other by the amount of this change so as to be corrected.

[0005]

In the projection exposure apparatus having such a structure, however, in order to accurately align the reticle and the photosensitive substrate, more specifically, the exposure pattern on the reticle and the exposure area on the photosensitive substrate are aligned. In order to align the pattern with high accuracy, the amount of deviation from the designed position of the pattern transferred by actually exposing (test exposure) the pattern on the photosensitive substrate in advance was measured before the actual exposure. . Then, a correction amount for correcting this deviation amount (positioning correction amount when positioning the reticle and the photosensitive substrate)
Must be calculated and the exposure must be performed after correcting the positioning between the reticle and the photosensitive substrate during the actual exposure, and it was unavoidable that the manufacturing process was complicated by that much.

The present invention has been made in view of the above points, and proposes an exposure method capable of highly accurately aligning a reticle and a photosensitive substrate without previously obtaining a positioning correction amount by test exposure. It is a thing.

[0007]

In order to solve such a problem, according to the present invention, a substrate (11) mounted on a stage (19) which can be two-dimensionally moved along a predetermined coordinate system (C1). The master plate (20) is positioned and the master plate (20)
The above pattern (22) is projected onto a predetermined area of the substrate (11) via a projection optical system (17) having a predetermined image forming characteristic, and the pattern (22) is superposed on the predetermined area, or predetermined. In an exposure method in which an area and an area adjacent to each other are exposed, a plurality of marks (51) are provided at predetermined positions with respect to a pattern (22) on an original plate (20), and a coordinate system of images of the plurality of marks is formed. The plurality of marks (51) detected by detecting the positions in (C1) respectively
A plurality of marks (51) at the image position of the projection optical system (1
7) Based on the amount of deviation from the designed position to be projected by means of 7), the positional deviation of the original plate (20) with respect to the coordinate system (C1) and a predetermined combination of the imaging characteristics of the projection optical system (17). The deviation with respect to the image characteristic is obtained, the correction amount of the positioning of the original plate (20) is obtained based on the positional deviation, and the correction amount of the imaging characteristic of the projection optical system (17) is obtained based on the deviation.
The position of the original plate (20) is corrected based on each of the obtained correction amounts, and the imaging characteristics of the projection optical system (17) are corrected to expose the first image of the pattern (22) on the substrate (11). Then, the expansion / contraction amount of the exposed substrate (11) is obtained, and the imaging characteristics and the positioning of the original plate (20) and the substrate (11) are further corrected based on the expansion / contraction amount, and the second pattern of the pattern (22) is corrected. The image is exposed by overlaying or stitching it onto the substrate (11).

Further, according to the present invention, different types of patterns (22) are exposed by superimposing or connecting them. Further, the positioning of the original plate (20) is to position the center of the pattern (22) on the original plate with respect to the substrate (11). Further, the positioning of the original plate (20) corrects at least one of the rotation amount and the shift amount of the original plate (20) with respect to the coordinate system (C1).

[0009]

Operation: A plurality of marks (51) are provided at predetermined positions with respect to the pattern (22) on the original plate (20) (the positions of the marks on the original plate are known) and projected onto the coordinate system (C1). The correction amount of the positioning of the original plate (20) and the imaging characteristic of the projection optical system (17) is obtained and corrected according to the amount of deviation of the positions of the images of the plurality of marks (51) from the designed position. hand,
The first image of the pattern (22) is exposed on the substrate (11) to obtain the expansion / contraction amount of the substrate (11), and the imaging characteristics and the original plate (20) and the substrate (11) are determined based on the expansion / contraction amount. By further correcting the positioning and exposing the second image of the pattern (22) by superimposing it on the substrate (11) or joining it, it is possible to accurately project the projected image without obtaining the correction amount of the positioning in advance. Alignment can be done.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. (1) Principle of Exposure Method In the exposure method according to the present invention, when exposing a layer (referred to as a second layer) that is overlaid on a previously exposed layer and is exposed, a reticle manufacturing error and a projection image of a projection lens The deviation of the projected image caused by the distortion is measured. That is, first, the shift of the projected image is measured by measuring the position of the image of the pattern (or mark) on the reticle projected by the projection lens in the moving coordinate system of the substrate stage. Then, the amount of alignment correction is obtained based on this deviation. Here, as a correction amount (alignment correction amount) for adjusting the projected image of the reticle to a predetermined position (designed position) in the moving coordinate system of the substrate stage, a shift correction amount in the x and y directions of the reticle is η _x , Let η _y [μm], the rotation correction amount of the reticle be ψ [μrad], and the magnification correction amount of the projection lens be m [ppm].

At least one set of alignment marks (at least two marks in each direction) for measuring scaling (magnification error due to expansion and contraction of the substrate) in the x and y directions is provided on the photosensitive substrate. When exposing on the photosensitive substrate, the scaling correction amount in the x and y directions of the photosensitive substrate, which is obtained from the result of detecting the position of the alignment mark on the substrate, is shifted in the x and y directions by γ _x , γ _y [ppm]. When the correction amounts are ε _x and ε _y [μm], the exposure position coordinates (X ₀ ′, Y ₀ ′) on the photosensitive substrate of the reticle center are

[0012]

[Equation 1]

[0013] Note that this exposure position coordinate is not a position in the moving coordinate system of the substrate stage,
It is a position in the array coordinate system defined on the photosensitive substrate. The array coordinate system moves with respect to the moving coordinate system of the substrate stage. In this equation (1),
The coordinate values (X _p , Y _p ) are design coordinate positions on the moving coordinate system C1 of the projected image of the center of the pattern to be exposed,
The coordinate values (x _p , y _p ) are design coordinate positions of the projected image of the center of the pattern with respect to the projected image of the reticle center.
In addition, m [ppm] previously obtained as the lens magnification correction value
And m '[ppm] are used to correct the magnification, and the reticle rotation amount is corrected by ψ [μrad].
Exposure is performed at the exposure position coordinates determined by the equation (1). Thus, if the alignment correction amount is obtained in advance and the expansion / contraction on the photosensitive substrate is measured at the time of alignment, the exposure may be executed by the formula (1), so that the complicated work such as the test exposure is not required. The projected images can be aligned with high accuracy. (2) Exposure method according to the embodiment In FIG. 1, reference numeral 10 denotes an exposure apparatus that uses the exposure method according to the present invention as a whole, in the x and y axis directions orthogonal to each other in a plane perpendicular to the optical axis of the exposure light. A reticle 20 is held on a reticle stage 16 that can move in parallel and can rotate in its plane. The reticle pattern formed on the reticle 20 is projected and exposed on the photosensitive substrate 11 via the projection lens 17.

The photosensitive substrate 11 is a two-dimensional moving coordinate system C1.
Is mounted on a substrate stage 19 which can move in parallel in the X and Y axis directions along. Also, this substrate stage 1
9 is X by a length measuring device 1X, 1Y such as a laser interferometer.
The configuration is such that the position in each direction of the axis and the Y-axis is obtained. The obtained position is the substrate stage controller 15
And the position of the substrate stage is controlled by the stage drive unit 2 including a motor and a ball screw based on this position. The main computer 21
By controlling the substrate stage 19 and the reticle stage 16, a reticle pattern is projected and exposed onto a predetermined area on the photosensitive substrate 11 by a so-called step-and-repeat operation, and the reticle patterns are connected on the photosensitive substrate 11, or the reticle pattern is connected. It is formed by overlapping patterns. The origin of the moving coordinate system C1 is assumed to coincide with the position where the optical axis of the projection lens 17 passes.

An alignment microscope 18 is disposed near the projection lens 17 in a predetermined relationship with the optical axis of the projection lens and at a predetermined position on the moving coordinate system C1, and is mounted on a substrate stage 19. By detecting the mark on the photosensitive substrate 11 that has been formed, the moving coordinate system C of the substrate stage 19 is detected.
The position of the mark on the photosensitive substrate 11 at 1 is detected. still,
The alignment microscope 18 includes a reference mark plate 3 described later.
By detecting the reference mark on 0, the moving coordinate system C
The position of the detection center of the alignment microscope 18 in 1 can be obtained.

Here, the position of the reticle stage 16 is controlled by the reticle stage controller 12. The projection lens 17 has its projection magnification controlled by the magnification controller 13. Further, the position of the substrate stage 19 is controlled by the substrate stage controller 15. When the substrate alignment marks 61 to 68 formed by exposure on the exposed photosensitive substrate 11 are detected by the alignment microscope 18, the detection result is detected by the length measuring instruments 1X and 1Y at that time via the alignment controller 14. It is sent to the main computer 21 together with the result.
The reticle stage controller 12, the magnification controller 13, and the substrate stage controller 15 each send a control command based on a control signal from the main computer 21.

As shown in FIG. 2, a reticle pattern 22 is formed on the reticle 20, and a measurement mark 51 is formed to indicate the position of the reticle pattern 22. Further, on the stage 19, there is a reference mark plate 30 for measuring the position of the measurement mark 51 in the reticle 20 in the moving coordinate system C1. This reference mark plate 30
Has a light source inside, and as shown in FIG. 3, for example, the light from the light source that has passed through the slit-shaped reference mark irradiates the measurement mark 51 in the reticle 20 and, if scanned, is received by the alignment sensor 23. The position of the measurement mark 51 in the moving coordinate system C1 of the substrate stage can be known from the amount of transmitted light. Further, the reticle 20 has an alignment mark 50
Is entered. The positional relationship between the design coordinates of the reticle 20 and the photosensitive substrate 11 is shown in FIG. If the alignment mark 50 of the reticle 20 is designed symmetrically with respect to the reticle center O _R , the respective measured values are (X _ra ′,
Y _ra ′), (X _rb ′, Y _rb ′)

[0018]

[Equation 2]

The (X _rc ′, Y _rc ′) represented by is the reticle center. When a plurality of measurement marks 51 contained in the reticle 20 are measured, the deviation amount (ΔX _ri , ΔY _ri ) from the design value (X _ri , Y _ri ) with the reticle center of each measurement mark 51 as the origin is measured. If the measured value of the mark 51 is (X _ri ′, Y _ri ′),

[0020]

(Equation 3)

Is given by Therefore, in order to match the projected image of the reticle 20 with the moving coordinate system of the substrate stage, for example, the correction amount is obtained so that the sum of squares thereof is minimized.
That is, if the function that gives the sum of squares is S, then

[0022]

[Equation 4]

It becomes The parameters of the correction value are magnification correction amount m [ppm], reticle rotation correction amount ψ [μrad
], As the reticle shift correction amount, the x direction and the y direction,
Since η _x and η _y ,

[0024]

(Equation 5)

From this, a four-dimensional simultaneous linear equation can be obtained. If there are two or more measurement points in each of the x direction and the y direction, these correction amounts can be uniquely obtained. When the first layer is exposed on the photosensitive substrate, the projection lens 17 is corrected by the magnification correction m [ppm] obtained here, and an offset of ψ [μrad] is placed on the reticle rotation during reticle alignment. Then consider the reticle shifts η _x and η _y ,
The substrate stage 19 is moved to expose according to the arrangement of design values.

The reticle shift η _x obtained here
And η _y are for correcting the reticle manufacturing error and the distortion of the projected image due to the projection lens.Regarding the displacement of the reticle with respect to the optical axis of the projection lens that occurs each time the reticle is placed on the reticle stage, As in the conventional case, it is necessary to correct the relative movement between the reticle and the photosensitive substrate.

The second layer is exposed to the photosensitive substrate 11 on which the first layer has been formed through the process. If the photosensitive substrate 11 expands due to the process at this time, the pattern of the first layer is as shown by a broken line 71 in FIG. 5, for example. The photosensitive substrate 11 is aligned. Alignment marks 61 and 62 that were inserted when exposing the first layer
Is detected and the photosensitive substrate 11 is rotated so as to be parallel to the running direction of the substrate stage 19 in the X direction, and then the positions of the alignment marks 61 to 68 are detected by an alignment microscope. The pattern 70 shown by a solid line shows an ideal design position.

In this example, the alignment marks 65, 66 for measuring the left and right x directions as scaling in the x direction,
The scaling in the x direction can be obtained from 67 and 68. In addition, the scaling in the y direction is performed from the alignment marks 61, 62, 63, 64 that measure the upper and lower y directions.
Directional scaling can be determined. If, for example, the alignment mark 61 and the alignment mark 68 are exposed as the reference in the Y direction and the X direction without measuring the scaling, the exposure becomes as shown in FIG. Cannot overlap.
In such a case, a plurality of vernier patterns for measuring the overlay deviation in the first layer and the second layer are appropriately inserted in advance for test exposure, and the correction amount is obtained by analyzing the measured values. It was

However, the scaling is measured, and the correction amounts in the x and y directions are set as γ _x and γ _y , respectively.
In addition to the previously calculated m [ppm] as the magnification correction amount for the projection lens,

[0030]

(Equation 6)

Magnification correction amount m '[ppm]
The reticle center is used as the photosensitive substrate 11 when the pattern is exposed.
The position (X ₀ ′, Y ₀ ′) to be exposed on the

[0032]

(Equation 7)

According to this, the second layer 72 can be made to coincide with the first layer 71 shown by the broken line in FIG. In the equation (7), (X _p , Y _p ) represents the design coordinate position where the center of the pattern to be exposed should be on the photosensitive substrate 11, and (x _p , y _p ) is the pattern to be exposed in the reticle projection image. The center of indicates the design coordinate position that should be seen from the reticle center. Further, ε _x and ε _y are position correction amounts in the x direction and the y direction of the origin of the photosensitive substrate that occur during alignment of the photosensitive substrate. In this example, if the average value of the measurement values of the alignment mark positions in each direction is used, Good.

In order to completely agree with the first layer, the correction of the magnification is given as the average value of γ _x and γ _y.
It is necessary that _x = γ _y holds, and this is the same even when the analysis by test exposure is performed. If there is a priority direction in the alignment direction, the magnification correction amount m '[ppm] to be added may be determined according to the scaling correction amount in the priority direction.

In this exposure method, since the position change of the alignment mark must accurately reflect the expansion and contraction of the photosensitive substrate 11, the alignment mark is the projection lens 1.
It is necessary to put the 7-day distortion in the smallest possible position. Further, it is desirable to use, as the plurality of alignment marks, those that are all in the same position of the reticle 20 in order to improve the alignment accuracy.

When the arrangement of the alignment mark is different from that of this embodiment, each correction amount can be obtained in the same manner as the above-mentioned example of aligning the projected image of the reticle 20 with the moving coordinate system of the substrate stage. That is, an arbitrary alignment mark is used as a temporary reference for each of X and Y, and the deviation amount of the measured value of the position when the other alignment marks are viewed from the temporary reference is ΔX _i (X direction). about,
i is an index for distinguishing marks), ΔY
_j (in the Y direction, j is an index for distinguishing marks), and

[0037]

[Equation 8]

The scaling correction amounts γ _x and γ _y and the rotation correction amount θ of the photosensitive substrate so that the function S of is minimized.
[Μ rad], shift correction amount of photosensitive substrate ε _x [μm], ε
_y [μm] should be calculated. In order to uniquely determine these parameters, it is sufficient that there are three or more measurement points in each of the X direction and the Y direction. The rotation correction amount θ of the photosensitive substrate is to be parallel to the movement of the substrate stage 19 in the X direction, and the photosensitive substrate 11 needs to be rotated by this amount. The photosensitive substrate 11 is attached to the substrate stage 19
If the accuracy of the mechanism for making parallel to the running in the X direction is not good, the correction amount θ is further added as the correction amount of the reticle rotation, and the center of the reticle 20 is exposed on the photosensitive substrate 11 at the time of exposure. Position (X ₀ ′,
Y ₀ ′) is

[0039]

[Equation 9]

According to the above, Where (X ₀ , Y ₀ ) is
The center of the reticle 20 at the time of exposure is the design coordinate position which should be on the photosensitive substrate 11. In the actual manufacturing of the liquid crystal display, a plurality of reticles 20 may be required, but each reticle 20 has the same scale as the moving coordinate system C1 and the coordinate axes are parallel (in other words, For example, a magnification correction amount, a reticle rotation correction amount, and a reticle shift correction amount (based on the moving coordinate system C1) are obtained, and these correction amounts are changed for each reticle 20 at the time of exposure, based on the above-described formula. If the exposure device is determined, accurate alignment can be performed even if there are a plurality of reticles 20.

According to the above configuration, accurate alignment can be achieved by only measuring the alignment mark without performing the test exposure, and the productivity is improved. In addition, if the position to insert the alignment mark is determined, a plurality of alignment microscopes 18 can be installed in accordance with the position, and the substrate stage can be moved once in each of the x and y directions to scan the mark. The value is obtained. This method can be used without taking a long alignment time.

[0042]

As described above, according to the present invention, a plurality of marks are provided at predetermined positions with respect to the pattern on the original plate, and the designed positions of the positions of the images of the plurality of marks projected on the substrate. The amount of correction of the substrate positioning and the imaging characteristics of the projection optical system is determined and corrected according to the amount of deviation from the, and the first image of the pattern is exposed on the substrate to determine the amount of expansion and contraction of the substrate. The image forming characteristics and the positioning between the original plate and the substrate are further corrected based on the amount of expansion and contraction, and the second image of the pattern is superimposed or joined on the substrate to be exposed, so that the positioning correction amount is set in advance. It is possible to realize an exposure method capable of accurately aligning a projected image without obtaining it.

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing a configuration of a projection exposure apparatus using an exposure method according to the present invention.

FIG. 2 is a schematic plan view showing an arrangement of alignment marks and measurement marks on a reticle projected on a photosensitive substrate through a projection lens.

FIG. 3 is a schematic front view for explaining a method of measuring a reticle position in a stage coordinate system.

FIG. 4 is a schematic plan view showing a positional relationship between design coordinates of a reticle and a stage.

FIG. 5 is a schematic plan view showing a pattern on a photosensitive substrate before and after expansion by a process by a solid line and a dotted line, respectively.

FIG. 6 is a schematic plan view showing an exposure result obtained by performing overexposure on an expanded pattern by using alignment marks at one location for each of X and Y.

[Explanation of symbols]

11 ... Photosensitive substrate, 16 ... Reticle stage, 17 ...
… Projection lens, 18 …… Alignment microscope, 19 ……
Substrate stage, 20 ... Reticle, 22 ... Pattern,
30: reference light source, 50: alignment mark, 51
…… Measurement marks, 61-68 …… Alignment marks on the photosensitive substrate.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01L 21/30 525 X 525 D

Claims (4)

[Claims] 1. A substrate and an original plate mounted on a stage which is two-dimensionally movable along a predetermined coordinate system, and a pattern on the original plate is projected through a projection optical system having a predetermined image forming characteristic. An exposure method in which the pattern is projected onto a predetermined area on the substrate, and the pattern is overlapped with the predetermined area, or the area adjacent to the predetermined area is exposed by exposing the pattern on the original plate. A plurality of marks at predetermined positions to detect the positions of the images of the plurality of marks in the coordinate system, and the plurality of marks at the positions of the detected images of the plurality of marks are the projection optical Based on the amount of deviation from the designed position to be projected by the system, the positional deviation of the original plate with respect to the coordinate system and the predetermined imaging characteristics of the imaging characteristics of the projection optical system with respect to the predetermined imaging characteristics. The difference is calculated, the correction amount for positioning the original plate is calculated based on the positional deviation, the correction amount of the imaging characteristic of the projection optical system is calculated based on the deviation, and the correction amount is calculated based on the calculated correction amounts. The position of the original plate is corrected, the imaging characteristic of the projection optical system is corrected, the first image of the pattern is exposed on the substrate, and the expansion / contraction amount of the exposed substrate is calculated. An exposure method, wherein the image formation characteristic and the positioning between the original plate and the substrate are further corrected based on the amount, and the second image of the pattern is exposed by overlapping or joining the substrate. 2. The exposure method according to claim 1, wherein the exposure method is such that the different types of patterns are exposed by overlapping or joining. 3. The exposure method according to claim 1, wherein the positioning of the original plate is performed by positioning the center of the pattern on the original plate with respect to the substrate. 4. The exposure method according to claim 1, wherein the positioning of the original plate corrects at least one of a rotation amount and a shift amount of the original plate with respect to the coordinate system.