JPH11111601A - Method and device for exposure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exposure method by which the manufacturing cost and managing cost of a reticle can be reduced and, at the same time, the throughput can be improved in forming a single-layer pattern through performing multiplex exposures. SOLUTION: Two patterns which are exposed twice are arranged in parallel with each other in the pattern area of a reticle. After partial shot areas 46A and 46B on each row arranged on a wafer W are exposed to the two pattern images of the reticle, next partial shot areas 46B and 46C are exposed to the two pattern images by shifting the wafer W by the width portion of a partial shot area. Thereafter, the operation of exposing partial shot areas on each row to the two pattern images are repeated by shifting the wafer W by the width portion of a shot area. Consequently, the partial shot areas 46B and 46G, excluding the first and last shot areas, are doubly exposed to the two pattern images.

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 apparatus for exposing a mask pattern on a substrate such as a wafer in a lithography process for manufacturing, for example, a semiconductor device, a liquid crystal display device, or a thin film magnetic head. More specifically, the present invention relates to an exposure method for dividing a single mask pattern into a plurality of patterns and performing multiple exposure.

[0002]

2. Description of the Related Art One of exposure methods for transferring a reticle pattern as a mask onto a wafer (or a glass plate or the like) coated with a resist, which is used when manufacturing a semiconductor device or the like, is as follows. There is an exposure method called a double exposure method. This is because, for example, when a pattern in which a periodic pattern and an isolated pattern are mixed is exposed on the same layer on the wafer, the reticle pattern is changed to a first pattern corresponding to the periodic pattern and a second pattern corresponding to the isolated pattern. By dividing these two patterns into double exposures by sequentially optimizing the exposure conditions, high imaging performance is obtained.

Conventionally, when exposure is performed by such a double exposure method, a first exposure is performed using a first reticle having one or a plurality of first patterns formed thereon, and then a reticle is formed. Was replaced with a second reticle on which one or a plurality of the second patterns were formed, and the second exposure was performed. FIG. 6 shows a conventional reticle used when two chip patterns are formed in each shot area on a wafer by a double exposure method (that is, two chips are formed).
The same first pattern A is drawn in each of the two partial pattern areas 51A and 51B on the first reticle RA shown in FIG. 6A, and the second reticle RB shown in FIG.
The same second pattern B is drawn in each of the upper two partial pattern areas 52A and 52B. The reason why two pieces are taken in this way is to secure the throughput and to save the inspection cost and the inspection time by the comparative inspection.

In the exposure process using these reticles,
For example, assuming that a shot area of 3 rows × 5 columns is exposed on the wafer, first, as shown in FIG. 7A, three shots in the first column 54A to the fifth column 54E on the wafer are exposed. In regions 53A to 53C, images of two patterns A in first reticle RA in a predetermined order (this image is also represented by A).
Are exposed under exposure conditions optimized for the pattern A. Thereafter, the reticle RA is replaced with a second reticle RB, and as shown in FIG. 7B, three shot areas 53A to 53A in the first to fifth rows 54A to 54E on the wafer.
The images of the two patterns B in the second reticle RB (each of which is also represented by B) are overlaid and exposed on the 53C in the predetermined order under the exposure conditions optimized for the pattern B. Thereafter, a circuit pattern corresponding to the patterns A and B is formed by developing the wafer. In this case, the line width controllability and the like of the finally obtained circuit pattern are improved as a whole as compared with the method of performing exposure using one reticle on which the original pattern corresponding to the patterns A and B is formed. I have.

[0005]

In the conventional double exposure system as described above, higher image forming characteristics can be obtained as compared with the system in which only one original pattern is exposed. However, in the conventional double exposure method, since the reticle needs to be changed during the exposure process, the throughput of the exposure process (the number of wafers processed per unit time) is higher than when only one original pattern is exposed. There was an inconvenience that it was greatly reduced. In this regard, as can be seen from FIG. 7, in the conventional double exposure method, two shots are required for each shot area.
Since the number of exposures is to be performed, the number of exposures is twice as large as the number of shot areas, and the throughput also decreases in terms of the number of exposures. This is a natural result of double exposure. .

Further, in the conventional double exposure method, two reticles are required for exposing one layer on a wafer, so that there is an inconvenience that reticle manufacturing cost and management cost increase. Furthermore, even if there is a method capable of performing double exposure efficiently without using two reticles, if the finally obtained imaging characteristics are deteriorated, it is meaningful to perform double exposure. Is gone.

In view of the above, the present invention provides a method of manufacturing a reticle, in which a single layer pattern is formed by multiple exposures, as compared with a conventional method in which a plurality of reticle patterns are sequentially superposed and exposed. It is a first object of the present invention to provide an exposure method capable of reducing cost and management cost and improving throughput. A second object of the present invention is to provide an exposure method that can reduce the manufacturing cost of a reticle and obtain high imaging characteristics when a pattern of one layer is formed by multiple exposure.

Another object of the present invention is to provide an exposure apparatus that can use such an exposure method.

[0009]

According to a first exposure method of the present invention, a plurality of exposure areas (46B to 46G) on the same resist (photosensitive material) of a substrate to be exposed are respectively different in N areas (where N is N). In an exposure method in which an image of a mask pattern of (2 or more integers) is overlaid and exposed, N mask pattern regions (4) arranged in a line in a predetermined direction on the mask (R).
5A, 45B), and the images (A1, B1) of the N mask patterns on the mask on the substrate.
And the substrate and the mask are relatively moved in the predetermined direction by a width corresponding to the width of the mask pattern area (45A, 45B) in the predetermined direction, and the substrate and the mask are placed on the substrate. A second step of partially overlaying and exposing the images (A2, B2) of the N mask patterns of the above-mentioned mask patterns, and further comprising at least (N−
2) It repeats twice.

According to the present invention, since a plurality of mask patterns are formed on one mask, only one mask is required and the manufacturing cost of the mask is reduced. Further, as shown in FIG. 4, for example, when double exposure is performed on each of three shot areas (47A to 47C) of two pieces each having a width F, the exposure method of the present invention requires the mask image and the substrate to be exposed. Since it is necessary to perform exposure seven times while shifting by F / 2, the number of exposures is greater than six in the conventional double exposure method. However, in the actual exposure process, the mask exchange time is much longer than the shot exposure time of several shots. Therefore, the present invention improves the throughput as compared with the conventional double exposure method.

When double exposure is performed (when N = 2)
By performing the first step and the second step once, double exposure is performed in at least one exposed region. Further, in the present invention, when exposing the images of the N mask patterns onto the substrate, the mask and the substrate are synchronously exposed to an illumination light beam for illuminating the mask pattern, and the exposure is performed. Those N on that mask
It is desirable that the arrangement direction of the individual mask pattern regions and the scanning direction of the synchronous scanning are set in parallel, and the exposure conditions are changed for each mask pattern.

This means that the present invention is applied to a case where exposure is performed by a scanning exposure method such as a step-and-scan method. When a plurality of mask patterns are exposed as described above, the illumination conditions (normal illumination, deformed illumination, illumination of small σ value, etc.), the focus position, and the exposure conditions such as the exposure amount are optimized for each mask pattern. Is desirable. In this regard, in the case of the simultaneous exposure method, in the case of simultaneously exposing a plurality of mask patterns on one mask, it is necessary to devise the configuration of the exposure apparatus in order to change the illumination conditions and the like for each mask pattern. However, when the arrangement direction of the mask patterns is made parallel to the scanning direction by the scanning exposure method, the illumination conditions and the like can be continuously switched when sequentially exposing a plurality of mask patterns. The effect of improvement can be easily obtained.

In a second exposure method according to the present invention, a pattern of a mask (R) is illuminated by a slit-shaped illumination region, and a plurality of mask patterns are arranged in a scanning direction of the illumination region. An exposure method for projecting an image of a pattern of a mask onto the same resist on the substrate by synchronously scanning the substrate (W), and exposing the mask by changing exposure conditions for each pattern of the mask. .

According to the present invention, after one exposure, the mask (R) and the substrate (W) are shifted by one pattern in the scanning direction to perform the exposure in which the mask (R) and the substrate (W) are partially overlapped. Multiple exposure can be performed using one mask. Further, by switching the exposure condition to a condition optimized for the pattern each time the illumination region moves to another pattern, a high imaging characteristic by multiple exposure can be obtained.

Further, the exposure apparatus according to the present invention illuminates the pattern of the mask (R) with a slit-shaped illumination area, and a plurality of the mask patterns are arranged in the scanning direction of the illumination area. And an exposure apparatus that projects the pattern image of the mask onto the same resist on the substrate by synchronously scanning the mask and the substrate when performing exposure by synchronously scanning the mask and the substrate in the scanning direction.
An exposure condition control system (1) that changes exposure conditions according to the movement of the slit-shaped illumination area to the next pattern area.
1, 12, 41, 43). According to such an exposure apparatus, the first or second exposure method of the present invention can be used.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In this example, the present invention is applied to the case where double exposure is performed using a projection exposure apparatus of a step-and-scan method. FIG. 1 shows a projection exposure apparatus of a step-and-scan method used in this embodiment. In FIG. 1, the projection exposure apparatus comprises ultraviolet pulse light emitted from an exposure light source 1 composed of an excimer laser light source such as KrF or ArF. The exposure light IL is reflected by the mirror 4 for bending the optical path, and then enters the fly-eye lens 10 via the first lens 8A, the mirror 9 for bending the optical path, and the second lens 8B. First lens 8A and second lens
By the beam shaping optical system composed of the lens 8B,
The cross-sectional shape of the exposure light IL is shaped according to the incident surface of the fly-eye lens 10. Note that a mercury lamp or the like can be used as the exposure light source 1.

On the exit surface of the fly-eye lens 10, an aperture stop plate 11 of an illumination system is rotatably arranged. Around the rotation axis of the aperture stop plate 11, a circular aperture stop 13A for normal illumination, a plurality of An aperture stop 13B for deformed illumination composed of a small aperture eccentric, an annular aperture stop 13C for annular illumination,
And small coherence factor of small circle (σ value)
Aperture stop 13D is arranged. Then, a main control system 41 composed of a computer that supervises and controls the operation of the entire apparatus rotates the aperture stop plate 11 via the drive motor 12 so that a desired illumination system aperture stop is formed on the exit surface of the fly-eye lens 10. It is configured so that it can be placed.

A part of the exposure light IL that has passed through the aperture stop on the exit surface of the fly-eye lens 10 is
After being reflected by the, it is incident on an integrator sensor 16 composed of a photoelectric detector via a condenser lens 15. The detection signal of the integrator sensor 16 is supplied to the exposure control system 43. The exposure control system 43 calculates the illuminance (pulse energy) of the exposure light IL on the surface of the wafer W based on the detection signal.
In addition, the integrated exposure amount at each point on the wafer W is indirectly monitored. Then, the exposure control system 43 controls the output of the exposure light source 1 and the output of the light attenuator (not shown) so that the illuminance or the integrated exposure monitored in this manner becomes the value specified by the main control system 41. The decay rate of the exposure light IL is controlled.

On the other hand, the exposure light IL transmitted through the beam splitter 14 passes through a first relay lens 17A and sequentially passes through a fixed field stop (reticle blind) 18A and a movable field stop 18B. The fixed field stop 18A and the movable field stop 18B are arranged close to each other and substantially on a conjugate plane with the pattern surface of the reticle R to be transferred. The fixed field stop 18A is a field stop that defines the shape of a rectangular illumination area on the reticle R, and the movable field stop 18B is configured to prevent unnecessary portions from being exposed at the start and end of scanning exposure. Used to close the lighting area.

Fixed field stop 18A and movable field stop 1
The exposure light IL that has passed through the second relay lens 17B
B, a mirror 19 for bending the optical path, and a condenser lens 20 illuminate a rectangular illumination area 21R in a pattern area 31 provided on the pattern surface (lower surface) of the reticle R. Illumination area 2 of reticle R under exposure light IL
The pattern in 1R is reduced and projected via the projection optical system PL at a predetermined projection magnification β (β is ４ ，, ５, etc.) onto the exposure area 21W on the wafer W coated with the resist. An aperture stop 35 is arranged in an optical Fourier transform plane (pupil plane) with respect to the pattern surface of the reticle R in the projection optical system PL, and the numerical aperture NA is set by the aperture stop 35. Hereinafter, the Z axis is taken in parallel with the optical axis AX of the projection optical system PL, the Y axis is taken along the scanning direction during scanning exposure in a plane perpendicular to the Z axis, and the non-scanning direction is taken perpendicular to the scanning direction. X
A description will be given taking the axis.

The reticle R is held on a reticle stage 22, and the reticle stage 22 is mounted on a reticle base 23 so as to be continuously movable in the Y direction by a linear motor. Further, the reticle stage 22 also incorporates a mechanism for finely moving the reticle R in the X, Y, and rotation directions. On the other hand, the wafer W is
The wafer holder 24 is fixed on a Z tilt stage 25 for controlling the focus position (position in the Z direction) and the tilt angle of the wafer W.
Is fixed on an XY stage 26, and the XY stage 26 is, for example, by a feed screw system or a linear motor system.
Move the Z tilt stage 25 (wafer W) on the base 27 to Y
, And stepping in the X and Y directions. A wafer stage 28 is constituted by the Z tilt stage 25, the XY stage 26, and the base 27. The positions of the reticle stage 22 (reticle R) and the wafer stage 28 (wafer W) are each measured with high precision by a laser interferometer (not shown), and based on the measurement results, the stage drive system 42 causes the reticle stage 22 and the wafer stage to move. Operation 28 is controlled.

The position information of the reticle stage 22 and the wafer stage 28 is supplied from the stage drive system 42 to the main control system 41, and the main control system 41 sends the stage drive system 4.
2 is supplied with alignment information, scanning exposure timing information, and the like. Also, the stage drive system 42
The movable field stop 18B is also opened and closed via a drive system (not shown) according to the synchronization information of each stage from.

At the time of ordinary scanning exposure, the reticle R is moved by + Y to the illumination area 21R via the reticle stage 22.
The wafer W is moved via the XY stage 27 to the exposure area 21 in synchronization with the movement in the direction (or the −Y direction) at the speed VR.
Speed β · VR in the −Y direction (or + Y direction) with respect to W
(Β is the projection magnification from the reticle R to the wafer W), whereby the pattern image in the pattern area 31 of the reticle R is sequentially transferred to one shot area SA on the wafer W. Thereafter, the operation of stepping the XY stage 26 to move the next shot area on the wafer to the scanning start position and performing scanning exposure is repeated in a step-and-scan manner, and each shot area on the wafer W is repeated. Is exposed. At this time, based on the detection signal of the integrator sensor 16, the exposure control system 43 controls the exposure for each point on each shot area to a predetermined target value.

When this exposure is a superposition exposure, it is necessary to previously align the reticle R with the wafer W. Therefore, Z tilt stage 25
A reference mark member 29 made of a glass substrate is fixed near the upper wafer holder 24. Cross reference marks 30A and 30B are formed on the reference mark member 29 by a chrome film or the like, and a wafer is provided on a side surface of the projection optical system PL. An image processing type alignment sensor 36 for detecting the position of a wafer mark attached to each shot area on W is provided. A reference mark (not shown) for the alignment sensor 36 is also formed on the reference mark member 29. The alignment marks 3 are located on both sides of the pattern area 31 of the reticle R in a positional relationship obtained by converting the positional relationship between the reference marks 30A and 30B by the projection magnification from the wafer to the reticle.
2A and 32B are formed, and the alignment mark 3
Image processing type reticle alignment microscopes 34A and 34B are installed on 2A and 32B via a mirror 33A and the like.

When the alignment of the reticle R is performed, as an example, the reference marks 30A and 30B are set to substantially the center of the exposure field of the projection optical system PL and the reference marks 30A and 30B are positioned on the bottom side. Illuminated with illumination light in the same wavelength range as the exposure light IL. The images of the reference marks 30A and 30B are aligned with the alignment marks 32A and 32.
B, formed near reticle alignment microscope 34
A and 34B detect the amount of misalignment of the alignment marks 32A and 32B with respect to the images of the reference marks 30A and 30B, and position the reticle stage 22 so as to correct these amounts of misalignment. Is performed. At this time,
By observing the corresponding reference mark with the alignment sensor 36, the interval (baseline amount) from the detection center of the alignment sensor 36 to the center of the pattern image of the reticle R is calculated. When performing overlay exposure on the wafer W, the wafer stage 28 is driven based on the position obtained by correcting the detection result of the alignment sensor 36 by the baseline amount, so that the reticle R Can be scanned and exposed with high overlay accuracy.

Next, the case where two chip patterns of a predetermined semiconductor device are taken in each shot area on the wafer W and double exposure is performed using the projection exposure apparatus of this embodiment will be described. In the pattern area 31 of the reticle R of this example, two patterns for double exposure are formed along the scanning direction. FIG. 2 is a plan view showing the pattern arrangement of the reticle R used in the present example. In FIG. 2, the pattern region surrounded by the rectangular frame-shaped light-shielding band 44 of the reticle R has two lines in the Y direction. Two identically-sized partial pattern areas 4
The patterns are divided into 5A and 45B, and patterns A and B are drawn in the partial pattern areas 45A and 45B, respectively. Patterns A and B are patterns generated from a circuit pattern transferred to one layer, and
And B are superposed and exposed so that a projected image corresponding to the circuit pattern is exposed. As an example, the pattern A is a periodic pattern, the pattern B is an isolated pattern, and the optimal exposure conditions (the aperture stop of the illumination system, the focus position of the wafer, the exposure amount, etc.) of the pattern A and the pattern B are different from each other. I have.

FIG. 4 shows a shot arrangement on the wafer W of this embodiment. In FIG. 4, the first row 48A to the fifth row 48E arranged at a predetermined pitch in the X direction are arranged in the Y direction. Shot areas 47A to 47C are arranged at a predetermined pitch,
These shot areas are rectangular areas having a width F in the Y direction (scanning direction) and a width E in the X direction, including an area up to the center of the street line area at the boundary between the adjacent shot areas.

These 3 × 5 shot areas 47A
Since two chip patterns of the semiconductor device are formed in the Y direction in the respective Y-directions, these shot areas 47A to 47C are sequentially divided into two partial shot areas 46B, 46C,. , 46G. Furthermore, in this example, the +
The partial shot areas 46A and 46H are added to the end in the Y direction and the end in the −Y direction of the partial shot area 46G, respectively, so that the partial shot area 46 of 8 rows × 5 columns as a whole is obtained.
A to 46H are arranged on the wafer W. The width in the Y direction of the partial shot regions 46A to 46H is F / 2. However, 1
Since the partial shot areas 46A and 46H in the rows and the eighth row are not areas where chip patterns are formed, they may extend outside the effective exposure area of the wafer W.

Next, in the shot arrangement shown in FIG.
The operation when double exposure is performed on the two patterns A and B of the reticle R in FIG. 2 will be described above. [First Step] First, the pattern image of the reticle R of FIG. 2 is exposed to the two partial shot areas 46A and 46B of the first row 48A of FIG. 4 by the scanning exposure method using the projection exposure apparatus of FIG. In this case, as shown in FIG.
The reticle R is scanned, for example, in the + Y direction with respect to the illumination region 21R of L. Therefore, when the first partial pattern area 45A (pattern A) of the reticle R is scanned with respect to the illumination area 21R, the main control system 41 of FIG.
Is to select an aperture stop corresponding to the pattern A in the aperture stop plate 11 via the drive motor 12 in advance, arrange the aperture stop on the exit surface of the fly-eye lens 10, and
3 so that an exposure amount corresponding to the pattern A can be obtained. Then, when a part of the second partial pattern area 45B (pattern B) of the reticle R enters the illumination area 21R, the main control system 41 sets the aperture stop corresponding to the pattern B via the drive motor 12. It is selected and arranged on the exit surface of the fly-eye lens 10, and an exposure amount corresponding to the pattern B is obtained via the exposure amount control system 43.

When the best focus position of the wafer W differs between the pattern A and the pattern B, the focus position of the wafer W is adjusted via the wafer stage 28 when a part of the pattern B enters the illumination area 21R. I do. Thus, the images of the patterns A and B of the reticle R in FIG. 2 are exposed under the optimized exposure conditions.
Although the projection optical system PL of FIG. 1 actually performs reverse projection, an erect image will be projected in the scanning direction in the following for convenience of description. As a result, as shown in FIG.
The images A1 and B1 of the patterns A and B of the reticle R are exposed on the partial shot areas 46A and 46B, respectively.

In the step-and-scan method, in order to eliminate useless movement of the reticle stage 22, it is desirable to reverse the scanning direction for each exposure, and the stepping amount of the wafer stage 28 is small. It is desirable. Therefore, for example, the first columns 48A to 48A in FIG.
The scanning direction of reticle R (and correspondingly wafer W) is set to + Y with respect to partial shot areas 46A and 46B of fifth row 48E.
The images of the patterns A and B of the reticle R may be sequentially exposed while reversing from the direction to the −Y direction or from the −Y direction to the + Y direction. In such an exposure sequence, the exposure in the next row is performed while moving from the fifth column 48E to the first column 48A, but for convenience of explanation, it is assumed that the exposure is performed again in the first column 48A. I do.

[Second Step] Next, in FIG. 4, after the wafer W is shifted by F / 2 in the + Y direction with respect to the exposure in the first step, the partial shot areas 46B and 46C of the first column 48A are The images A2 and B2 of the patterns A and B of the reticle R of FIG. 2 are respectively exposed by the scanning exposure method using the projection exposure apparatus of FIG. Also in this case, exposure is performed by optimizing the exposure conditions for the patterns A and B, respectively. As a result, the image B1 of the pattern B and the image A2 of the pattern A are double-exposed to the second partial shot area 46B of the first column 48A. At this time, if scanning exposure is also performed in the partial shot areas 46B and 46C from the fifth row 48E to the second row 48B while reversing the scanning direction as described above, the partial shot areas 46B in each row are used. That is, the images of the patterns A and B are double-exposed.

[Third Step] Next, in FIG. 4, after the wafer W is shifted by F / 2 in the + Y direction with respect to the previous exposure, the partial shot areas 46C and 46D of the first row 48A are scanned. The images A3 and B3 of the patterns A and B of the reticle R in FIG. 2 are exposed while optimizing the exposure conditions by the exposure method. As a result, the image B2 of the pattern B and the image A3 of the pattern A are also double-exposed to the third partial shot area 46C of the first column 48A. Then, for example, the scanning direction is also sequentially reversed in the partial shot regions 46C and 46D of the second column 48B to the fifth column 48E,
The images A3 and B3 of the patterns A and B are exposed.

In this example, since there are three shot areas 47A to 47C of two pieces to be exposed in each row, the first row 48
In A, the images A4, B4 to A7, and B7 of the patterns A and B are further exposed to the partial shot areas 46D and 46E to the partial shot areas 46G and 46H by the scanning exposure method, and similarly in the other rows 48B to 48E. The images A4 and B4 to A7 and B7 of the patterns A and B are exposed. As a result, the images A2, B1 to A7, and B6 of the patterns A and B are double-exposed to the second partial shot area 46B to the seventh partial shot area 46G in the first row 48A to the fifth row 48E as a whole. You. In this example, the partial shot areas 46B to 46B
Since three shot areas 47A to 47C are formed from 6G, these three shot areas 47A to 47C are formed.
Means that the images of the patterns A and B are double-exposed, respectively. Also, the first partial shot area 46
A and the last partial shot area 46H are each 1
It is a so-called dummy exposure area where only the image of one pattern A or B is exposed.

Thereafter, by developing the wafer W, the shot areas 47A in the first row 48A to the fifth row 48E are developed.
A resist pattern of two pieces is formed on each of the .about.47C, and a target circuit pattern is formed by performing etching or the like using this resist pattern as a mask. At this time, since the images of the patterns A and B are exposed under the optimized exposure conditions, the image forming characteristics (resolution, etc.) of the double-exposed pattern image are extremely good over the entire surface. The line width controllability and the like of a circuit pattern to be formed are also very good.

Next, the throughput of the exposure system of the present embodiment will be compared with the ordinary exposure system and the conventional double exposure system. Therefore, the number of effective shot areas 47A to 47C in FIG. 4 is increased to 6 rows (scanning direction) × 10 rows, that is, 60 rows in FIG. 1 in accordance with the wafer used in normal exposure. When calculating the throughput when performing exposure in each exposure method using a projection exposure apparatus,
Table 1 below.

[0037]

[Table 1]

In Table 1, the normal exposure is a method in which only one exposure is performed for each shot area using one reticle pattern. The reticle exchange method is the conventional double exposure method described with reference to FIGS. The step time in the left column of Table 1 is a stepping time of the wafer stage 28 for moving the next exposure target shot area (or partial shot area) to the scanning start position. This is one scanning exposure time, and the overhead time is the time required for wafer exchange and the like.

Further, in this method, as can be seen from FIG. 4, the number of exposures in each of the columns 48A to 48E is increased by one with respect to twice the number of shot areas 47A to 47C. The number of exposures (first time) when the shot area is 6 rows × 10 columns is 130 (= (2.6+
1) and 10) times. In contrast, the number of exposures in the conventional reticle exchange method is 6 for both the first and second exposures.
0 times. The number of exposures in the normal exposure method is 60, which is the same as the number of shot areas. As a result, the processing time per wafer (the time from loading a wafer to a projection exposure apparatus to unloading it) is 6 times in the normal exposure method.
1 sec, 103 sec with this method, 12 with reticle exchange method
7 seconds, the number of wafers processed per hour (throughput) is 59 in the normal exposure method and 35 in the present method.
The number of sheets is 28 in the reticle exchange method, and it can be seen that this method can achieve higher throughput than the reticle exchange method. According to Table 1, the number of exposures is larger in this method than in the reticle exchange method, but the overall processing time is longer in this method because the reticle exchange time is much longer than one exposure time. Has been shortened.

Furthermore, while the reticle exchange method requires two reticles, the present method requires only one reticle, so that the manufacturing and management costs of the reticle are greatly reduced. It should be noted that the highest throughput is naturally obtained in the normal exposure method, but the imaging characteristics of the projected image on each shot area are inferior to those of the present method and the reticle exchange method. Therefore, the present method is effective for applications requiring high imaging characteristics even if the throughput is slightly reduced.

Further, as can be seen from FIG. 4, in the exposure method of this embodiment, there is a useless exposure area such as the partial shot areas 46A and 46H. In order to eliminate such useless exposed regions, when performing the scanning exposure, the scanning may be performed from the middle of the reticle R. That is, for example, in the step of exposing the images A1 and B1 of the patterns A and B of the reticle R of FIG. 2 to the partial shot areas 46A and 46B of FIG. 4, the exposure of the image B1 of the pattern B only to the lower partial shot area 46B is performed. May be performed.

FIG. 3B shows the reticle R at the start of scanning exposure when only the image of the pattern B is exposed in this manner. In FIG. The partial pattern area 45B of the reticle R is located before the illumination area 21R. Then, after the start of the scanning exposure, the partial pattern area 45B with respect to the illumination area 21R.
Is scanned in the + Y direction, and the partial shot area 46 of the wafer W is scanned.
By scanning B in the corresponding direction, the image B1 of the pattern B is exposed only in the partial shot area 46B.

Similarly, in the step of exposing the images A7 and B7 of the patterns A and B of the reticle R to the lowermost partial shot areas 46G and 46H on the wafer W in FIG. The image A7 of A may be exposed. FIG. 5 shows a shot arrangement in a case where the exposure of the useless partial shot area on the wafer W is omitted as described above. In FIG.
Only the three shot areas 47A to 47C in the row 48E are subjected to double exposure of the images of the patterns A and B by taking two pieces. As a result, the actual number of exposures is closer to that of the conventional reticle exchange method, and the throughput is further improved.

In the above embodiment, since the original circuit pattern is divided into two patterns A and B to perform double exposure, the pattern area of the reticle R is divided into two partial pattern areas 45A and 45A in the scanning direction. 45B. In this case, the image of the target circuit pattern composed of the images of the patterns A and B is exposed on one partial shot area 46B shown in FIG. 4 only by executing the first step and the second step. You.

On the other hand, if the original circuit pattern is divided into N ′ patterns (N ′ is an integer of 3 or more) and multiple exposure is performed, the pattern area of the reticle R in FIG. The pattern is divided into N 'partial pattern areas, and individual patterns for multiple exposure are drawn in these partial pattern areas. At the time of exposure, the first
Subsequent to the step, after the second step is performed with the wafer shifted in the scanning direction by a width corresponding to one partial pattern area, the wafer is further shifted in the scanning direction by a width corresponding to one partial pattern area. By repeating the second step (N′−2) times, the N ′ pattern images are multiple-exposed to one partial shot area on the wafer. In other words, when the original circuit pattern is divided into N ′ patterns and subjected to multiple exposure, the second step is repeated (N′−1) times in total, so that the target circuit pattern is formed in one partial shot area. A complete image of the pattern will be exposed.

In the above embodiment, the steps
Since an AND-scan projection exposure apparatus is used, two patterns for double exposure can be exposed under optimized exposure conditions. However, a batch exposure type projection exposure apparatus such as a stepper may be used as the exposure apparatus. Using a batch exposure type projection exposure system,
For example, the partial shot areas 46A to 46A of the first column 48A in FIG.
In the case of exposing at 46H, it is only necessary to repeat the partially superposed exposure while sequentially performing wafer stepping by F / 2 in the Y direction. When optimizing the exposure condition for each of the two patterns in the batch exposure type, for example, regarding the exposure amount, one of the two pattern regions and one of the conjugate regions is opened and closed at the position of the field stop in the illumination system. A shutter may be provided.

The present invention is not limited to the above-described embodiment, but may take various configurations without departing from the spirit of the present invention.

[0048]

According to the first exposure method of the present invention, a plurality of mask patterns are formed on one mask. (Reticle) manufacturing costs and management costs can be reduced. Further, the mask and the substrate need only be partially overlapped and exposed while gradually moving relative to each other, and there is no need to replace the mask during the exposure. Therefore, there is an advantage that the throughput can be improved as compared with the conventional method of exposing while exchanging a plurality of masks (reticles).

In this case, when exposing the images of the N mask patterns onto the substrate, the mask and the substrate are exposed to an illuminating light beam for illuminating the mask pattern by synchronizing and scanning. The arrangement direction of the above N mask pattern areas and the scanning direction of the synchronous scanning are set in parallel,
When the exposure condition is changed for each mask pattern, the exposure condition can be optimized for each mask pattern to be subjected to multiple exposure, and therefore, there is an advantage that a high imaging characteristic can be obtained in a projected image after multiple exposure.

According to the second exposure method of the present invention,
Since a plurality of mask patterns are formed on one mask, manufacturing costs and management costs of the mask can be reduced. Further, since multiple exposure can be performed by optimizing the exposure condition for each mask pattern, there is an advantage that high imaging characteristics can be obtained. Further, according to the exposure apparatus of the present invention, the exposure method of the present invention can be used.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a projection exposure apparatus used in an example of an embodiment of the present invention.

FIG. 2 is a plan view showing a pattern arrangement of a reticle used in the embodiment.

FIG. 3A is a plan view showing a reticle scanning method during normal scanning exposure, and FIG. 3B is a plan view showing a reticle scanning method when only one pattern on the reticle is exposed.

FIG. 4 is a plan view showing an example of a shot arrangement on a wafer according to the embodiment.

FIG. 5 is a plan view showing a shot arrangement in a case where exposure to a useless partial shot area on a wafer is omitted in the embodiment.

FIG. 6 is a plan view showing two reticles used in a conventional double exposure method.

FIG. 7 is an explanatory diagram in the case of performing exposure by a conventional double exposure method.

[Explanation of symbols]

 Reference Signs List 1 exposure light source 11 aperture stop plate 18A fixed field stop R reticle PL projection optical system W wafer 21R illumination area 21W exposure area 22 reticle stage 28 wafer stage 41 main control system 45A, 45B partial pattern area 46A to 46H partial shot area 47A to 47C Shot area

Claims (4)

[Claims] An exposure method for superposing and exposing different N (N is an integer of 2 or more) mask pattern images on a plurality of regions to be exposed on the same resist of a substrate to be exposed. A first step of forming the N mask pattern regions arranged in a line in a direction, exposing an image of the N mask patterns on the mask on the substrate, Is relatively moved in the predetermined direction by a width corresponding to the width of the mask pattern region in the predetermined direction, and the images of the N mask patterns on the mask are partially overlapped and exposed on the substrate. A second step, wherein the second step is further repeated at least (N-2) times. 2. When exposing the images of the N mask patterns on the substrate, the mask and the substrate are exposed to an illumination light beam for illuminating the mask pattern by synchronously scanning the mask pattern and the substrate. 2. The exposure method according to claim 1, wherein an arrangement direction of the N mask pattern regions on the mask and a scanning direction of the synchronous scanning are set in parallel, and an exposure condition is changed for each mask pattern. . 3. A pattern of a mask is illuminated by a slit-shaped illumination area, a plurality of the patterns of the mask are arranged in a scanning direction of the illumination area, and the mask and the substrate are synchronously scanned. An exposure method for projecting an image onto the same resist on the substrate, wherein the exposure is performed by changing exposure conditions for each pattern of the mask. 4. A pattern image of the mask is formed by illuminating a pattern of a mask with a slit-shaped illumination area, arranging a plurality of mask patterns in a scanning direction of the illumination area, and synchronously scanning the mask and the substrate. An exposure apparatus that projects the mask onto the same resist on the substrate, wherein the mask and the substrate are synchronously scanned in the scanning direction to perform exposure, and the slit-shaped illumination area moves to a next pattern area. An exposure condition control system for changing an exposure condition in accordance with the exposure condition.