JPH097933A - Projection aligner and projection exposure method - Google Patents

Abstract

PURPOSE: To improve the throughput of the step-and-scan projection exposure by eliminating the stepping time due to zigzag running of a wafer. CONSTITUTION: A step-and-scan projection aligner exposes a pattern on a mask to a photosensitive substrate by relatively scanning the mask and the wafer. Two masks are alternately illuminated each time scanning exposure is performed for one shot area, and while scanning exposure is performed for one mask, another mask is moved to the scanning start position by using two mask stages 11 and 14, which move the two masks 2A and 2B in a one dimensional direction, and by using two blinds 23 and 25 which permit the illuminating light to be applied only on the mask to be used for scanning exposure. Continuous scanning exposure can be performed in a plurality of shots arranged in the wafer scanning direction by repeating such operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a step-and-scan type projection exposure apparatus and its exposure method, and more specifically, it can continuously scan and expose a plurality of shots arranged in the scanning direction on a wafer. The present invention relates to a step-and-scan type projection exposure apparatus and an exposure method thereof.

[0002]

2. Description of the Related Art A projection exposure apparatus is used for exposing a fine pattern on a wafer in a lithography process for manufacturing a semiconductor device, a liquid crystal display device and the like. In such a projection exposure apparatus, an exposure method by a step-and-repeat method in which a photosensitive substrate such as a wafer is exposed while being stepwise moved for each shot through a projection optical system having an exposure field capable of containing the entire pattern of a mask (reticle). Has been adopted. Since this method can achieve high resolution and high throughput, it is currently the mainstream method for projection exposure.

A so-called step-and-scan method has been developed as another exposure method capable of achieving high resolution. In this method, the reticle is scanned in the scanning direction for each shot, and the wafer is scanned in the opposite direction at a speed synchronized with the reticle, and then the wafer is stepwise moved to move the exposure field to the next shot and the scanning exposure is repeated. .

FIG. 6 shows a traveling path of a wafer when a plurality of shots are scanned and exposed by the step-and-scan method. As shown in FIG. 6, when the three shots S ₁ , S ₂ and S ₃ lined up in the X direction of the wafer 1 were sequentially exposed, the wafer stage had to be moved in a zigzag manner as shown by arrows. This is because if an attempt is made to expose a row of shot areas corresponding to the diameter of the wafer by only one continuous scan in the X direction of the reticle, the reticle and the reticle of a size corresponding to the magnification of the projection lens × the diameter of the wafer. This is because a stage is required, and it has been impractical to manufacture such a long reticle and reticle stage. Therefore, it is necessary to use one reticle multiple times and repeat scanning exposure for each shot.
At this time, since the reticle must be scanned in the opposite direction to the immediately preceding scan in order to prevent the throughput from being lowered due to the reticle being idled, the wafer was stepwise moved in a complicated manner along the path shown in FIG. FIG. 7 shows the movement speed v _R of the reticle stage in the scanning direction (Y direction), the movement speed v _{W1 of} the wafer stage in the scanning direction (Y direction) and the wafer stage in the direction orthogonal thereto at the time t of the exposure operation. The moving speed v _W2 is shown. As can be seen from FIG. 7, shots S ₁ , S ₂ and S ₃ are divided into sections C, F and I.
In, uniform exposure is carried out by constant velocity scanning of the reticle stage. However, since the wafer has to move in a zigzag manner as shown in FIG. 6, the reticle stage and the wafer stage are in the acceleration / deceleration state in the sections A, D, G and J and the reticle stage in the sections B, E and H. It was in the state of waiting for the synchronous control of the stage and the wafer stage. In the acceleration / deceleration state and the control waiting state, the exposure is not performed, and the total time of those sections corresponds to the total time of the sections C, F, and I in which the exposure is performed. Therefore, there is a problem that the throughput of the exposure process per wafer is low due to the existence of such unexposed time.

[0005]

SUMMARY OF THE INVENTION Therefore, the present invention provides a novel projection exposure apparatus and a projection exposure method which can shorten the exposure operation in the conventional step-and-scan method and improve the throughput. With the goal.

It is another object of the present invention to provide a novel projection exposure apparatus and projection exposure method capable of continuously exposing a plurality of shots arranged in the scanning direction on a photosensitive substrate such as a wafer. .

[0007]

According to a first aspect of the present invention, there is provided a projection exposure apparatus for exposing a pattern image on a mask onto a photosensitive substrate while synchronously scanning the mask and the photosensitive substrate in a one-dimensional direction. , Two or more mask stages that respectively move two or more masks in a one-dimensional direction, a projection optical system that projects the pattern image on the mask onto the photosensitive substrate, and the projection optical system that projects the photosensitive substrate. 2 orthogonal to the optical axis of
The photosensitive substrate stage moving in the dimensional direction and the movement of the two or more mask stages are controlled in conjunction with the movement of the photosensitive substrate stage to scan and expose the photosensitive substrate with each pattern image of two or more masks. The projection exposure apparatus is provided with: a mask stage control means for controlling the mask stage; and an illumination system that sequentially illuminates the mask to be scanned and exposed in synchronization with the position of the mask.

In the projection exposure apparatus, the illumination system is capable of opening and closing an illumination optical path to the two or more masks.
It is preferable to provide one or more variable field diaphragms and a variable field diaphragm control means for sequentially opening the variable field diaphragms for the masks to be scanned and exposed among the two or more masks. The two or more variable field diaphragms change the width of the opening in the scanning direction according to the position of the opening having a variable width in the scanning direction and the position of the transfer area of the mask illuminated by the illumination system. Is preferably provided. The two or more masks are in a conjugate relationship with the photosensitive substrate via the projection optical system.

According to a second aspect of the present invention, there is provided a step-and-scan type projection exposure method for sequentially exposing shot areas on a photosensitive substrate by synchronously scanning two or more masks and the photosensitive substrate. And a mask used for scanning exposure, which is substantially parallel to the step A of scanning one of the two or more masks and the photosensitive substrate to perform scanning exposure of a shot area on the photosensitive substrate. Step B of moving at least one mask different from the above to the scanning start position for the next scanning exposure, and the mask different from the mask used in the immediately preceding scanning exposure step and the photosensitive substrate are synchronously scanned and Step C of scanning and exposing the next shot area,
Substantially parallel to the step C, a step D of moving at least one mask different from the mask being subjected to the scanning exposure to a scanning start position for the next scanning exposure, and after the steps A and B, The projection exposure method is provided by repeating steps C and D to continuously scan and expose a plurality of shot areas arranged in the scanning direction on the photosensitive substrate.

According to a third aspect of the present invention, step-and-scan projection exposure is performed in which two masks are used and the mask and the photosensitive substrate are synchronously scanned to sequentially expose the shot areas of the photosensitive substrate. A method of exposing a shot area on the photosensitive substrate by synchronously scanning the first mask and the photosensitive substrate while illuminating the first mask.
In parallel with step A, step B of moving the second mask to the scanning start position, and after step A is completed,
While illuminating the second mask, a step C in which the second mask and the photosensitive substrate are synchronously scanned to expose the next shot area on the photosensitive substrate, and the first mask is exposed almost in parallel with the step C. And the step D of moving to the scanning start position,
The projection exposure method is provided by continuously scanning and exposing a plurality of shots arranged in the scanning direction on the photosensitive substrate by repeating steps D to D.

In the above-mentioned second and third aspects of the present invention, after a plurality of shots arranged in the scanning direction on the photosensitive substrate are continuously scanned and exposed, the photosensitive substrate is moved in a direction orthogonal to the scanning direction. It is preferable to include stepping. Further, it is preferable to illuminate only the mask on which scanning exposure is performed by alternately blocking the illumination light to the first mask and the second mask.

According to a fourth aspect of the present invention, there is provided a step-and-scan projection exposure method for sequentially exposing shot areas of a photosensitive substrate by synchronously scanning the mask and the photosensitive substrate using a plurality of masks. Thus, there is provided the above projection exposure method, wherein the shot areas on the plurality of photosensitive substrates arranged in the scanning direction are exposed with the pattern images of the plurality of masks while continuously moving the photosensitive substrate in the scanning direction.

[0013]

According to the present invention, the illumination for sequentially illuminating two or more reticles in order to eliminate useless stepping time of the wafer when continuously scanning and exposing a plurality of shot areas aligned in the scanning direction on the wafer. Using the system, two or more reticle stages capable of moving each reticle in a one-dimensional direction, and means for controlling the movement of the two or more reticle stages in conjunction with the movement of the wafer stage, The reticle is moved in the direction opposite to the scanning direction during exposure almost in parallel with the reticle performing the exposure operation by constant velocity scanning, and at the end of the exposure by the first reticle, in synchronization with the continuous movement of the wafer stage. The exposure scanning with another reticle is started, and after the exposure scanning is completed, the exposure scanning is performed with another or first reticle in conjunction with the continuous movement of the wafer stage. And so as to start.

The principle of the present invention will be described below by taking the case of using two reticles as an example. FIG. 4 shows a scanning path of the wafer when exposing three shots S ₁ , S ₂ and S ₃ arranged in the Y direction on the wafer 1 using the projection exposure apparatus of the present invention. In the present invention, in order to perform continuous exposure on the wafer in the scanning direction shown by the arrow in FIG. 4, the movement timing and the movement speed v _R1 of the two reticles R1 and R2 are set.
And v _R2 control each reticle stage so that it follows the graph of FIG. FIG. 5 shows the scanning direction (Y direction) of the reticle R1 at time t of the exposure operation on the path shown in FIG.
Moving velocity v _R1, moving velocity v _R2 in the scanning direction (Y direction) of the reticle R2, indicating the moving velocity v _W of the wafer scanning direction (stage) (Y-direction). While the reticle R1 is performing the exposure operation by the constant velocity scanning (mainly the section A), the other reticle R2 is moved on the reticle stage in the direction opposite to the scanning direction during exposure, and when the exposure of the reticle R1 is completed, the reticle R2 is moved. Return to the position where exposure scanning can start. When the exposure of the reticle R1 is completed, the uniform speed scanning by the reticle R2 is started. At this time, since the reticle R1 is at the exposure end position on the reticle stage, the reticle R1 is moved in the direction opposite to the scanning direction during the constant velocity scanning by the reticle R2 (mainly the section B), and the reticle R1 is moved at the end of the exposure of the reticle R2. Return to the position where you can start the exposure scan. Next, after the exposure by the reticle R2 is completed, the scanning exposure by the reticle R1 is started again, and the constant velocity scanning is executed (mainly the period C). In the present invention, when one reticle is in the scanning exposure state, the illumination light that illuminates the other reticle is blocked by using the variable field diaphragm. In the figure, A to C
In this section, the scanning exposure is continuously repeated by one of the reticles in synchronism with the scanning of the wafer, so that the stepping operation of the wafer for each shot becomes unnecessary. Therefore, as shown in FIG. 5 (c), the wafer speed v _w is always constant, and the unexposed time for accelerating, decelerating, and waiting the wafer as in the prior art is not required, resulting in a large exposure time. It can be shortened. That is, if exposure is performed by this method,
As shown in the paths and in FIG. 4, all the shots in an arbitrary row are exposed by unidirectional uniform velocity scanning of the wafer, and then all the shots in an adjacent row are uniformly scanned in the opposite direction. can do. In the present invention, such an exposure operation can significantly improve the throughput of the exposure process.

The present invention will be described below with reference to examples.
These are merely specific examples, and the present invention is not particularly limited thereto.

[0016]

FIG. 1 shows a specific example of the projection exposure apparatus of the present invention. A projection exposure apparatus of the present invention is an apparatus for projecting a pattern image formed on a reticle onto a shot area of a wafer by a step-and-scan method via a projection optical system, and mainly includes an illumination system, a reticle moving mechanism, and a reticle. The projection optical system for projecting the pattern image formed on the wafer 1 onto the wafer 1, the wafer moving mechanism, and the control system. The illumination system includes an excimer laser 37, which is a light source, and an illumination optical system 3.
0, 31, fixed blinds 123, 125 defining the illumination field on the wafer and variable blinds 23, 25 limiting the opening width of such fixed blinds. The excimer laser 37 is adjusted in pulse oscillation and laser power and wavelength by the laser control device 47. Illumination light generated from the excimer laser 37 (for example, KrF excimer laser having a wavelength of 248 nm) is divided into two by the half mirror 36, and the illumination light reflected by the half mirror 36 enters the illumination optical system 30. The illumination optical system 30 is composed of a relay lens, a fly-eye lens, an integrator sensor, a speckle reduction device, etc., which are not shown, and the illumination light is made uniform by the fixed blind 123 and the variable blind 23 described later by passing through these. Becomes, that is,
The reticle 2A is illuminated with a substantially uniform illuminance. On the other hand, the illumination light transmitted through the half mirror 36 enters the illumination optical system 31 via the mirror 35, the relay lenses 34 and 33, and the mirror 32. The illumination optical system 31 is an illumination optical system 30.
It is composed of the same elements as. The illumination light emitted from the illumination optical systems 30 and 31 travels toward the fixed blinds 123 and 125 via the lenses 28 and 29, respectively.

Fixed blinds 123 and 125 are formed with openings 49 and 50, respectively, which define the illumination field for each reticle. The number of scans on a single wafer can be reduced by making the openings 49 and 50 of the fixed blind, that is, the width of the illumination field on the reticle in the direction orthogonal to the scan direction, as large as possible. Fixed blinds 123 and 125
Variable blinds 23 and 25 that can limit the opening width of the blinds are installed below the. Variable blind 23
And 25 function as variable field diaphragms and serve as shutters that close the openings of the fixed blinds corresponding to the reticle not used for scanning exposure. Further, the variable blind reduces the width of the light-shielding band on the scanning start portion and the scanning end portion on the reticle to reduce the overrun of the reticle (illumination light passing outside the light-shielding band on the reticle unnecessarily exposes the wafer 1). The opening width can be appropriately adjusted for the purpose of preventing the above). As a variable blind for executing such a function, for example, Japanese Patent Laid-Open No.
A variable field stop as described in 196513 can be applied.

FIG. 8 is a schematic plan view of the variable blinds 23 and 25 used in this embodiment. The variable blind includes four movable plates BL ₁ , BL ₂ , BL ₃ and B.
The blades BL ₁ and BL ₂ are configured by L ₄ and move in the Y direction (scanning exposure direction) in the drawing to limit the width of the openings 49 and 50 of the fixed blinds 123 and 125 in the scanning direction, and the blade BL ₃ And BL ₄ move in the X direction in the figure to fix the fixed blind 123 or 12
The length (width in the direction orthogonal to the scanning direction) of the openings 49 and 50 of No. 5 is limited. These blades are provided for blind drive mechanisms 24 and 26 of the variable blinds 23 and 25, respectively.
Controlled independently by. If the aperture of the fixed blind is limited by these four blades, the image of the rectangular aperture AP defined by the ends of these blades is imaged on the pattern surface of the lower surface of the reticle. The apertures 49, 50 of the fixed blind, or if the fixed blind is limited by the variable blind, the aperture AP of the variable blind is contained within the circular image field IF of the projection optics. The opening / closing timing and the opening width of the variable blind are controlled by the blind control device 44 through the blind drive mechanisms 24 and 26. The term “variable field stop control means” used in this specification corresponds to the blind control device 44 in this embodiment. Further, the term "means for varying the width of the opening in the scanning direction" used in the present specification refers to the movable plates BL ₁ , BL ₂ , B in this embodiment.
It corresponds to L ₃ and BL ₄ and the blind drive mechanisms 24 and 26.

The illumination light transmitted through the variable blind 23 is
It goes toward the reticle 2A via the lens 19, the mirror 18, the condenser lens 17 and the mirror 16 arranged behind the variable blind 23. Fixed blind 12 by adjusting lens 19 and condenser lens 17
The size of the opening 49 of No. 3 can be finely adjusted. Similarly, the illumination light transmitted through the variable blind 25 illuminates the reticle 2B via the lens 22, the condenser lens 21, and the mirror 20 arranged behind the variable blind 25.

Next, the reticle moving mechanism will be described.
The reticle moving mechanism of the reticle 2A is the stage support 1
0, a reticle XY stage 11 fixed thereon, and a reticle drive mechanism 42. The reticle 2A is supported on the XY stage 11 and moved in the XY directions by the reticle drive mechanism 42, and is scanned in the Y direction (direction perpendicular to the paper surface) particularly during scanning exposure. Similarly, the reticle moving mechanism 43 of the reticle 2B includes a stage support base 13, a vertical ZY stage 14 that moves the reticle 2B in the ZY direction (scans in the Y direction during scanning exposure), and a reticle drive mechanism 43. Moving mirrors 12 and 15 and fixed mirrors (not shown) are mounted on the stages 11 and 14, and the interferometers 39 and 40 monitor the reflected light from the moving mirrors and the fixed mirrors. Movement by the drive mechanisms 42 and 43 is controlled. The control is performed by the control device 100 connected to the drive mechanisms 42 and 43. The reticle 2A supported on the reticle stage 11 is in a conjugate relationship with the variable blind 23 via the mirror 16, the condenser lens 17, the mirror 18, and the lens 19, and the reticle 2B is on the reticle stage 14 with the mirror 20, the condenser lens 21, It is in a conjugate relationship with the variable blind 25 via the lens 22.

The projection optical system in the projection exposure apparatus of the present invention includes a first projection optical system for projecting the pattern image of the reticle 2A onto the wafer 1 and a pattern image of the reticle 2B for the wafer 1.
A second projection optical system for projecting upward is provided, and each is composed of a lens front group 5 and a rear group 3, and a lens front group 6 and a rear group 3 via a beam splitter 4. That is,
In this embodiment, the first and second projection optical systems are divided into a front lens group and a rear lens group with the pupil plane sandwiched therebetween, so that the first and second projection optical systems share the rear lens group. It is the one. In this embodiment, the projection magnification of the projection optical system is 1/5. Therefore, the moving speed in the scanning direction of the XY stage 9 during the scanning exposure is the same as the reticle stage 11,
It becomes 1/5 of the moving speed of 14.

The wafer moving mechanism is mainly composed of an XY stage 9 movable in the XY directions and a Z and tilt stage 8 installed thereon. The wafer 1 is mounted and fixed on the Z, tilt stage 8. The position of the wafer is detected by monitoring the reflected light from the movable mirror 7 and the fixed mirror (not shown) installed on the Z, tilt stage 8 by the interferometer 38, and the X, Y, Z, tilt drive is performed. It is controlled by the mechanism 41 so that it can be moved to any position. Further, during scanning exposure, the synchronization control device, which will be described later, controls so as to synchronize with the scanning of the reticle.

The control system of the projection exposure apparatus of this embodiment includes a control device 100, a blind control device 44, a synchronization control device (not shown) and the like. The control device 100 controls the reticle stage drive mechanisms 42 and 43, the wafer stage drive mechanism 41, and the like to adjust the movement timing between the reticle 2A and the reticle 2B and the relative movement between the reticle and the wafer. The blind control device 44 controls the shutter function and the opening width adjusting function of the blinds 23 and 25. The synchronization controller monitors the difference between the output signals from the interferometers 38, 39, 40 mounted on the wafer stage and the reticle stage, respectively, and detects the speed at which both or one of the reticles is synchronized with the movement of the wafer stage (wafer stage It is controlled to move in synchronization with the scanning speed / magnification of the projection optical system). As a result, the reticle stage and the wafer stage are drive-controlled at a speed ratio according to the projection magnification of the projection optical system.

Next, the operation of the projection exposure apparatus of the present invention constructed as described above will be described. The illumination light emitted from the excimer laser light source 37 is split into two light fluxes by the half mirror 36 toward the illumination optical system 30 and the illumination optical system 31, and travels toward the fixed blinds 123 and 125, respectively. Illumination light passes through apertures 49 and 50 in fixed blinds 123 and 125 to define the illumination field on the reticle, which is then variable blind 2.
Reach 3 and 25. At this time, as described in detail later, one of the openings AP of the variable blinds 23 and 25 is opened and the other is closed every exposure of each shot area on the wafer, and the two reticles 2A and 2B are closed. It will be illuminated alternately. Then, the pattern images of the reticles 2A and 2B are alternately projected onto the wafer 1 by the projection optical system.

At the time of scanning exposure, one of the reticles 2A and 2B and the wafer 1 are relatively scanned with respect to the projection optical system. The situation is shown in FIG. FIG. 2A shows the projection optical system (front group) 5
And illumination fields 149 and 150 projected onto 6
2A and 2B are conceptual diagrams showing the scanning directions of the reticles 2A and 2B, in which stages and the like are omitted. The right side of FIG. 2 (a) shows the illumination field 14 viewed from above the reticle 2A.
9 shows the relationship between 9 and the scanning direction of the reticle 2A. This illumination field 149 has an opening 49 in the fixed blind 123.
Is defined by The left side of FIG. 2A shows the moving directions of the illumination field 150 and the reticle 2B as seen from above the reticle stage 14. In either reticle, during scanning exposure, the wafer 1 is scanned in the same direction (+ Y or −Y direction in this embodiment) with respect to the exposure field (projection area of the reticle pattern) of the projection optical system, in other words, the wafer. A plurality of shots lined up in the scanning direction (Y direction) on 1 are moved so as to be continuously scanned and exposed with each pattern image of the reticles 2A and 2B. FIG. 2B is a diagram showing the scanning direction of the shot 48 on the wafer 1 with respect to the exposure field 51 projected on the wafer by the projection optical system (5, 3) or (6, 3). The wafer 1 is moved with respect to the exposure field 51 in the Y direction (however, the direction opposite to the movement of the reticle). The relative scanning between the reticle 2A, 2B and the wafer 1 is executed by the control of the drive mechanism of the reticle stage 11, 14 and the wafer stage 9 by the control system and the synchronous control device.

Next, the opening / closing operation of the variable blinds 23 and 25 and the scanning timing of the reticles 2A and 2B will be described with reference to FIGS. FIG. 3 shows the fixed blind 12
₃ is a conceptual diagram showing a process of exposing shots S ₁ and S ₂ on a wafer through openings 49 and 50 of 3,125, FIG.
Changes in the relative positions of the openings 49, 50 (to be exact, the exposure field of the projection optical system) and the shots S ₁ , S ₂ accompanying the scanning of the wafer, and the opening / closing state of the fixed blind openings 49, 50 by the variable blinds 23, 25. Are sequentially shown by (1) to (3) in the same figure. Although the reticle is omitted in order to simplify the drawing, the reticle stage 11 that carries the reticles 2A and 2B is synchronized with the movement of the wafer 1 along with the XY stage 9 in the Y direction (the arrow in the figure) during exposure. And 14 move in opposite directions. The shaded portions of the shots S ₁ and S ₂ show the portions exposed through the openings 49 or 50, and the shaded portions in the openings 49 and 50 are the regions through which the illumination light passes, that is, the variable blinds 23, 25 The area not shielded from light is shown. Also, the dashed lines show the blade positions of the variable blinds 23 and 25 on the respective openings 49 and 50, and the blinds 23 and 25.
Depending on the position of the blades, the openings 49 and 50 are totally or partially shaded.

FIG. 3A shows the shot S ₁ exposed from the left end to the right end in the figure by the shot S ₁ passing through the exposure field defined by the opening 49 in the direction of the arrow. Here, the variable blind 23 opens the opening 49 of the fixed blind, and on the reticle 2A,
The pattern image in the illuminated area defined by the aperture 49 is projected and exposed on S ₁ . The state of FIG. 3 (1a) corresponds to the time shown in FIG. 5 (a), and the reticle 2A is in a state of performing constant velocity scanning.

FIG. 3 (1b) shows the positions of the openings 50 and the blades of the variable blind 25 at the same scanning time as in (1a). Since the opening 50 is shielded by the variable blind 25, the illumination light from the opening 50 does not reach the reticle 2B and the shot S1. This state is the time in FIG. 5B, that is, the reticle 2B starts the constant velocity scanning for exposing the pattern on the next shot S2.

Next, FIG. 3 (2a) shows that when the wafer is further scanned in the Y direction by the XY stage from the state of (1a), and the shot to be exposed moves from S ₁ to S ₂ , it is opened by the opening 49. The state where the defined exposure field exists at the boundary between the shots S ₁ and S ₂ is shown. At this time, the variable blind 23 functions as a variable field stop. That is, the variable blind 23 partially covers the opening 49 in synchronization with the movement of the wafer 1 so that the illumination light from the opening 49 does not reach the shot S ₂ . Details of such a variable field diaphragm will be described later. This state corresponds to the time shown in FIG. 5 (a), and the reticle 2A is in the stage of ending the uniform velocity scanning.

FIG. 3B shows the positions of the openings 50 and the blades of the variable blind 25 at the same scanning time as in FIG. 2A. In this case, the variable blind 25 is attached to the wafer 1
In synchronism with the movement in the direction of the arrow, the function of the variable field stop controls the aperture 50 to illuminate only the shot S ₂ . This state is at the time indicated by in FIG. 5 (b), and the reticle 2B is in a state immediately after the start of constant velocity scanning.

When the wafer 1 is further scanned from the state shown in FIGS. 3 (2a) and 3 (2b), the exposure field defined by the opening 49 exists on the shot S ₂ at the position shown in FIG. 3 (a). To do. At this time, the aperture 49 is completely shielded by the variable field diaphragm of the variable blind 23. This state corresponds to the time indicated by in Fig. 5 (a), and the reticle 2
A is in a state where the uniform velocity scanning is completed. Figure 3 (3b) shows (3
Aperture 50 and variable blind 2 at the same scanning time as in a)
The position 5 is shown. The variable blind 25 completely opens the opening 50 of the fixed blind and starts exposing the shot S ₂ with the illumination light passing through the opening 50. This state is at the time shown in FIG. 5B, that is, the reticle 2B is scanning at a constant speed. After that, the reticle 2B continuously scans at a constant speed in synchronization with the scanning of the wafer 1 to expose the shot S ₂ over the entire surface. Even boundary of two shots the above operation, without the pattern image of the reticle 2A to be exposed to the shot S ₁ is projected onto the shot S _2, the reticle 2B is and exposed to the shot S ₂ Pattern image is not projected onto the shot S ₁ .

The same operation as described above is repeated when moving from shot S ₂ to shot S ₃ adjacent thereto. In the exposure of the shot S ₃ , the opening 49 has the variable blind 23.
Is opened to project an image of the pattern of the reticle 2A onto the wafer 1, while the opening 50 is closed by the variable blind 25, and the reticle 2B moves in the direction opposite to the scanning direction. By repeating such an operation, the variable blind is switched for each shot to alternately project the pattern image of the reticle 2A or 2B on the wafer 1. The variable blinds 23 and 25 are simultaneously driven on the shot boundary (street line).
Switching of the variable blind is performed by the blind control device 44.
Controlled by. In the exposure operation, a sequence for continuously controlling each blind, each reticle stage driving device, and the XY stage is incorporated in the control system, and the control device 100 manages a series of operations. The term “mask stage control means” used in this specification corresponds to the control device 100 in this embodiment.

The operation of the blind drive mechanism that appropriately adjusts the opening widths of the variable blinds 23 and 25 will be described below. These operations are performed by the variable blind 23.
And 25 and the combination of the reticles 2A and 2B, they are hereinafter simply referred to as the variable blind and the reticle R. FIG. 9 shows the positional relationship between the reticle R that can be mounted on the projection exposure apparatus of this embodiment and the aperture AP of the variable blind. As an example of the reticle R, one in which four chip patterns CP ₁ , CP ₂ , CP ₃ and CP ₄ are arranged in the scanning direction (Y direction) is used. The four chip patterns CP ₁ , CP ₂ , CP ₃ and CP ₄ are separated by a light-shielding band (hatched portion) corresponding to a street line between adjacent chip patterns, and a collective area formed by these chip patterns. The periphery of the (shot area) is surrounded by a light shield (hatched portion) having a width D _sb wider than the street line. Here, of the light-shielding bands around the shot area, the left and right light-shielding band portions SB
1 and SBr, and reticle alignment marks RM ₁ and RM ₂ are formed on the outer sides thereof. In addition, the opening A formed by the blind blades BL1 to BL4
P is defined by an edge E1 of the blade BL1 and an edge E2 of the blade BL2 extending parallel to the X direction orthogonal to the Y direction which is the scanning direction, and the interval (width in the scanning direction) between the edges E1 and E2 is Dap. . Further, the blades BL3 and BL4 are arranged so that the edge in the X direction of the opening AP exists on the extension of the center line of the light shielding band extending in the Y direction in the periphery. Therefore, the length of the aperture AP in the X direction is approximately (width in the X direction of the shot area on the reticle R) × (relay lens system (imaging system) 17 and 19 arranged between the reticle and the variable blind. , Or 21 and 22).

Next, referring to FIG. 10, the opening / closing operation of the aperture AP in association with the relative change between the reticle R and the illumination area (projected image of the aperture AP) defined by the aperture AP in the scanning exposure of the present embodiment. explain. FIG. 10 is a view of the reticle R viewed from the X direction in FIG. 9. Here, in order to make the operation of the blades BL1 and BL2 of the variable blind easy to understand, the blades BL1 and BL2 are shown just above the reticle R. The reticle R and the wafer W shown in FIG.
It is assumed that relative alignment is performed in advance by using an alignment system, a photoelectric sensor, etc. (not shown). First, as shown in FIG. 10A, the reticle R is aligned with the scanning start point in the Y direction on the reticle stage. Similarly, one corresponding shot area (not shown) on the wafer W is aligned with the scanning start point in the Y direction on the XY stage. At this time, the width Dap of the image of the aperture AP that illuminates the reticle R is ideally zero, but
Depending on the quality of the edges E1 and E2 of the blades BL1 and BL2, it may be difficult to make the edge zero completely. Therefore, in the present embodiment, the width Dap of the image of the aperture AP on the reticle is set to be smaller than the width Dsb of the light-shielding band SBr on the right side of the reticle R. Normally, the width Dsb of the shading band SBr is 4 to
It is about 6 mm and the width Dap of the image of the aperture AP on the reticle
Should be about 1 mm. Further, as shown in FIG. 10A, the center of the opening AP in the Y direction is previously shifted by ΔYS with respect to the optical axis AX in the direction opposite to the scanning traveling direction of the reticle R (left side in the drawing). . The distance .DELTA.YS is set to about half the maximum opening width Dap of the opening AP with respect to the reticle R. More specifically, since the dimension of the opening AP in the longitudinal direction is naturally determined by the width of the shot area of the reticle R in the X direction, the maximum value DAmax of the width Dap of the opening AP in the Y direction is also the image field of the projection optical system ( Projection field) Determined by the diameter of IF. The maximum value is D
Amax is calculated in advance by the control system. Furthermore, FIG.
The width (minimum) of the aperture AP at the scanning start point in (A) is set to DAmi
Letting n be, strictly speaking, DAmin + 2 · ΔYs = DAma
The distance ΔYs is determined so as to satisfy the relationship of x.

Next, from the above state, the reticle stage and the XY stage (not shown) are moved in mutually opposite directions at a speed ratio proportional to the projection magnification. At this time, FIG.
As shown in (B), among the blades of the variable blind, only the blade BL2 in the traveling direction of the reticle R is moved in synchronization with the movement of the reticle R so that the image of the edge E2 of the blade BL2 is on the light-shielding band SBr. To Then, the scanning of the reticle R advances, and the edge E2 of the blade BL2
Reaches a position defining the maximum opening width of the opening AP as shown in FIG. 10C, the movement of the blade BL2 is stopped thereafter. The blind drive mechanism is provided with an encoder that monitors the moving amount and moving speed of each blade, a tacho generator, etc., and position information and speed information from these are sent to a control system to synchronize with the scanning of the reticle stage. Used for.

Thus, the reticle R has the maximum opening AP.
While being irradiated with the illumination light that has passed through, it is sent in the Y direction at a constant speed and reaches the position of FIG. Next, the edge E of the blade BL1 in the direction opposite to the traveling direction of the reticle R
The image of 1 is the light-shielding band S on the left side of the shot area of the reticle R.
As shown in FIG. 10 (E), the image of the edge E1 of the blade BL1 is moved in the same direction in synchronism with the moving speed of the reticle R from the time when it hits Bl. Then, at the time when the left shading band SB1 is shielded by the edge image of the right blade BL2 (at this time, the left blade BL1 also moves, the width Dap of the opening AP becomes the minimum value DAmin), the reticle stage. Stop moving 30 and blade BL1.

By the above operation, the exposure (one shot exposure) of the reticle R by one scanning is completed, and the variable blind is closed. Such an operation is performed for each of the two variable blinds 123 and 125, and the opening / closing timing of the two blinds is controlled by the blind control device 44 so as to have the relationship described with reference to FIG.

By using such a variable blind, the stroke of the reticle stage in the scanning direction can be minimized, and the width Dsb of the light-shielding bands SBl and SBr that define both sides of the shot area in the scanning direction can be reduced (extremely. Does not require the shading bands SB1 and SBr).

As described above, the variable blinds 23 and 25
Instead of functioning as a variable field diaphragm as described in JP-A-4-196513, the width of the light-shielding band on the reticle may be increased. In this case, the variable blinds 23 and 25 act as shutters that alternately shield the illumination light traveling through the fixed blinds 123 and 125 toward the reticles 1 and 2 according to the reticle used for scanning exposure.

In the above embodiment, the case where two reticles are used has been described, but three or more reticles may be used. When using three or more reticles, while one reticle is being used for scanning exposure, at least one reticle of the other reticles is set at the scanning start position for the next scanning exposure. It suffices to perform the setting operation more slowly than when using two reticles.

In the above embodiment, the illumination light from the light source is fixed to the fixed blinds 123 and 12 using the half mirror 36.
The light quantity reaching the wafer is attenuated to 1/4 of the light quantity at the light source because the half mirror 4 is used in the projection optical system. To prevent this, the half mirror 36 and the optical member 4 may be used as a polarization beam splitter to rotate the polarization characteristics of the laser beam in accordance with the exposure conditions. However, in this case, since the imaging characteristics are affected, λ is set on the exit side of the optical member 4.
It is necessary to insert a / 4 plate. Furthermore, in this embodiment,
The projection lens is divided at the pupil position, and requires a relatively large space. Therefore, each aberration becomes large,
Although the optical design may be difficult, the design of the split type projection optical system can be further facilitated by using an aspherical lens.

Further, by the half mirrors 36, 4 etc.,
The intensity of the illumination light on the wafer 1 during scanning exposure is the reticle 2A.
And 2B can be different. Therefore, using the illuminometer 8 (not shown) on the Z-tilt stage 8, the reticle 2 is previously set.
The intensity of the illumination light that reaches the wafer through A and the projection optical system (5, 4, 3) and the reticle 2B and the projection optical system (6, 6).
Intensity of the illumination light that reaches the wafer through 4, 3) is measured in advance, and according to the measured intensity, the proper exposure amount can be given to the wafer for any reticle during scanning exposure. Scan speed of reticle 2A and reticle 2B
It is desirable to fine tune the scanning speed of At this time,
Since the scanning speeds of the reticles 2A and 2B are different, the scanning speed of the wafer 1 is adjusted (changed) for each shot in conjunction with it.

Although the excimer laser is used as the light source in the above embodiment, the same effect can be obtained by using various illumination light sources such as i-line of a mercury lamp. Further, although the split type optical system as described in the embodiment is used as the projection optical system, the projection type optical system can be configured by the reflection type optical system so as to obtain the same effect as the split type optical system.

[0044]

By using the projection exposure apparatus of the present invention, a plurality of shot areas arranged in one direction on the photosensitive substrate can be continuously scanned and exposed. Therefore, the zigzag movement of the wafer at the time of exposure becomes unnecessary, and the throughput of the exposure process can be greatly improved.
Further, since the extra step operation of the wafer stage is removed, the life of the wafer stage is improved. The projection exposure method of the present invention can significantly reduce the exposure time.

[Brief description of drawings]

FIG. 1 is a schematic side view of a specific example of a projection exposure apparatus of the present invention.

2A and 2B show scanning directions of a reticle with respect to an illumination field in the projection exposure apparatus of FIG. 1, FIG. 2A shows a scanning direction of a reticle with respect to an exposure field of a projection optical system, and FIG. It is a figure which shows the scanning direction of the reticle with respect to an exposure field.

FIG. 3 is a conceptual diagram showing a state where scanning exposure is performed using two reticles in the projection exposure apparatus of the present invention, and an opening defined by a fixed blind on a shot of the wafer being exposed. The positional relationship with the variable blind is shown, (1a) and (1b) are the stages at which the exposure by the shot S ₁ is completed, and (2a) and (2b) are the exposure scanning from the shot S ₁ to S _2. Shows the steps, (3a) and
(3b) is a diagram showing a step of starting exposure by the shot S ₁ .

FIG. 4 shows Y on a wafer 1 using the projection exposure apparatus of the present invention.
FIG. 6 is a plan view showing a scanning path of a wafer when exposing three shots S ₁ , S ₂ and S ₃ arranged in a direction.

5 is a moving speed v _R1 of a reticle R1 in a scanning direction (Y direction) and a moving speed v of a reticle R2 in a scanning direction (Y direction) at a time t of an exposure operation on the path shown in FIG.
₆ is a graph showing _R2 and a moving speed v _W of a wafer (stage) in a scanning direction (Y direction).

FIG. 6 is a diagram showing a trajectory of a wafer when a plurality of shots are scanned and exposed by a conventional step-and-scan method, and three shots S ₁ , S _2, and S ₃ arranged in the X direction on the wafer 1 are shown. FIG. 8 is a wafer plan view showing a state in which the wafer stage travels in a zigzag manner when sequentially exposed.

FIG. 7 is a graph showing the movement speed v _R of the reticle stage in the X direction and the movement speed v _{W1 of the} wafer stage in the scanning direction (X direction) at the exposure operation time t when the wafer stage shown in FIG. 6 is moved. 6 is a graph showing the moving speed v _W2 of the wafer stage in the direction orthogonal to it.

FIG. 8: Variable blinds 23 and 2 used in this embodiment
5 is a schematic plan view of FIG.

FIG. 9 is a plan view showing the positional relationship between the reticle R that can be mounted on the projection exposure apparatus of this embodiment and the opening AP of the variable blind.

FIG. 10 is a side view of the reticle R showing an opening / closing operation of the opening AP with respect to the reticle R in the scanning exposure of the present embodiment.

[Explanation of symbols]

 1 Wafer 2A, 2B Reticle 3 Lens Rear Group 4 Beam Splitter 5, 6 Lens Front Group 9 XY Stage 11, 14 Reticle Stage 23, 25 Variable Blind 30, 31 Illumination Optical System 37 Excimer Laser 39, 40 Interferometer 42, 43 Reticle Drive mechanism 44 Blind control device 48 Shot area 49,50 Opening 100 Control device 123,125 Fixed blind 149,150 Illumination field

Claims (9)

[Claims] 1. A projection exposure apparatus for exposing a pattern image on a mask onto a photosensitive substrate while synchronously scanning the mask and the photosensitive substrate in the one-dimensional direction, wherein two or more masks are each moved in the one-dimensional direction. Two or more mask stages, a projection optical system that projects the pattern image on the mask onto the photosensitive substrate, and a photosensitive substrate stage that moves the photosensitive substrate in a two-dimensional direction orthogonal to the optical axis of the projection optical system. And mask stage control means for controlling the movement of the two or more mask stages in conjunction with the movement of the photosensitive substrate stage to scan and expose the photosensitive substrate with each pattern image of two or more masks, The projection exposure apparatus according to claim 1, further comprising: an illumination system that sequentially illuminates a mask on which scanning exposure is performed in synchronization with a position of the mask. 2. The illumination system comprises two or more variable field diaphragms each capable of opening and closing an illumination optical path to the two or more masks, and a variable one for the mask of the two or more masks to be subjected to scanning exposure. The projection exposure apparatus according to claim 1, further comprising a variable field stop control means for sequentially opening the field stop. 3. The two or more variable field diaphragms each have a width in the scanning direction that is variable, and a width in the scanning direction of the opening according to a position of a transfer region of a mask illuminated by the illumination system. The projection exposure apparatus according to claim 2, further comprising: 4. The one or more masks are respectively conjugated with the photosensitive substrate via the projection optical system.
3. The projection exposure apparatus according to any one of 3 above. 5. A step-and-scan projection exposure method for sequentially exposing shot areas on a photosensitive substrate by synchronously scanning two or more masks and the photosensitive substrate, the method comprising the steps of: Step A of exposing one of the masks and the photosensitive substrate by synchronous scanning to expose a shot area on the photosensitive substrate, and at least one mask different from the mask used for scanning exposure is Step B of moving to a scanning start position for scanning exposure, and step of synchronously scanning a mask different from the mask used in the immediately preceding scanning exposure step and the photosensitive substrate to perform scanning exposure of the next shot area on the photosensitive substrate. C, and substantially parallel to step C, a step D of moving at least one mask different from the mask being subjected to scanning exposure to a scanning start position for the next scanning exposure, Extent after the A and B, the projection exposure method of continuously scanning exposure a plurality of shot areas arranged along the scanning direction on the photosensitive substrate by repeating the steps C and D. 6. A step-and-scan projection exposure method for sequentially exposing shot areas of a photosensitive substrate by synchronously scanning the mask and the photosensitive substrate using two masks, the first mask While illuminating, the step A of exposing the shot area on the photosensitive substrate by relatively scanning the first mask and the photosensitive substrate, and the step of moving the second mask to the scanning start position almost in parallel with the step A. A step B, and a step C in which, after the step A is completed, the second mask and the photosensitive substrate are relatively scanned while the second mask is illuminated to expose a next shot area on the photosensitive substrate. In parallel with C, a step D of moving the first mask to the scanning start position is included, and by repeating the steps A to D, a plurality of shots lined up in the scanning direction on the photosensitive substrate are continuously formed. Scanning exposure The projection exposure method that. 7. The method according to claim 5, further comprising stepwise moving the photosensitive substrate stepwise in a direction orthogonal to the scanning direction after continuously scanning and exposing a plurality of shots arranged in the scanning direction on the photosensitive substrate. Projection exposure method. 8. The projection exposure method according to claim 5, wherein the illumination light for the first mask and the second mask is alternately shielded to illuminate only the mask for which scanning exposure is performed. . 9. A step-and-scan projection exposure method for sequentially exposing a shot area of a photosensitive substrate by synchronously scanning the mask and the photosensitive substrate using a plurality of masks, wherein the photosensitive substrate is continuously scanned in a scanning direction. The projection exposure method described above, in which shot areas on a plurality of photosensitive substrates arranged in the scanning direction are exposed with pattern images of a plurality of masks while moving in a moving manner.