JP2674579B2 - Scanning exposure apparatus and scanning exposure method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure apparatus used in a lithography process during manufacturing of semiconductor devices, liquid crystal display devices and the like, and more particularly to a scanning exposure device for performing exposure by relatively moving a mask and a photosensitive substrate. And its exposure method.

[0002]

2. Description of the Related Art Conventionally, there are roughly two types of projection exposure apparatuses of this type. One is a wafer through a projection optical system having an exposure field capable of containing the entire mask (reticle) pattern. This is a method of exposing a photosensitive substrate such as a plate by a step-and-repeat method, and the other is to perform relative scanning under mask illumination of arc-shaped slit illumination light by making a mask and a photosensitive substrate face each other with a projection optical system in between. It is a scanning method of exposing by exposure.

A stepper adopting the former step-and-repeat exposure method is a mainstream apparatus in the recent lithography process, and has a higher resolution, overlay accuracy, throughput, etc. than an aligner employing the latter scan exposure method. Both are getting higher and steppers are considered to be the mainstream for some time to come.

Recently, a new system which achieves a high resolution even in a scan exposure system is disclosed in SPIE Vol.
088 Optical / Laser Microlithography II (198
9), pages 424 to 433, a step-and-scan method was proposed. The step-and-scan method scans a mask (reticle) one-dimensionally,
This is a mixture of a scanning method in which the wafer is scanned one-dimensionally at a speed synchronized with the scanning method and a method in which the wafer is step-moved in a direction orthogonal to the scanning exposure direction.

FIG. 9 is a diagram for explaining the concept of the step-and-scan method. In this case, the arrangement of shot areas (one chip or multi-chip) in the X direction on the wafer W is determined by arc-shaped slit illumination light RIL. Scanning exposure is performed, and the wafer W is stepped in the Y direction. In the drawing, arrows indicated by broken lines indicate exposure routes of step & scan (hereinafter, referred to as S & S), and shot areas SA1, SA2, ...
S & S exposure is performed in the order of SA6, and then the shot areas SA7, SA8,.
The same S & S exposure is performed in the order of A12.

In the S & S type aligner disclosed in the above document, the image of the reticle pattern illuminated by the arc-shaped slit illumination light RIL is formed on the wafer W via a 1/4 reduction projection optical system. Therefore, the scanning speed of the reticle stage in the X direction is precisely controlled to be four times the scanning speed of the wafer stage in the X direction. The arc-shaped slit illumination light RIL is used for a projection optical system using a reduction system in which a refraction element and a reflection element are combined, and in a narrow range of an image height point (a ring shape) separated from the optical axis by a certain distance. This is to obtain an advantage that various aberrations become almost zero. One example of such a reflection reduction projection system is disclosed in, for example, USP. 4,747,678
Is disclosed.

[0007] S using such arc-shaped slit illumination light
In addition to the & S exposure method, a normal projection optical system (full field type) having a circular image field
Attempts to apply the S exposure method have been disclosed in, for example,
No. 423. This publication discloses that a shape of exposure light for illuminating a reticle (mask) is a regular hexagon inscribed in a circular field of a projection lens system, and two opposite edges of the regular hexagon are oriented in a direction orthogonal to a scanning exposure direction. It is disclosed that by extending the length, S & S exposure with further improved throughput is realized.

That is, in this publication, the reticle (mask) illuminating area in the scanning exposure direction is made as large as possible so that the scanning speed of the reticle stage and the wafer stage can be reduced as compared with the S & S exposure method using the arc-shaped slit illumination light. It shows that it can be significantly higher.

[0009]

SUMMARY OF THE INVENTION The above-mentioned JP-A-2-22
According to the conventional technique disclosed in Japanese Patent No. 9423, the mask illumination area in the scanning exposure direction is made as large as possible, which is advantageous in throughput. However, in consideration of the actual scanning sequence of the mask stage and the wafer stage, the apparatus disclosed in the above-mentioned Japanese Patent Laid-Open Publication No.
There is no choice but to use the zigzag S & S method.

This is because the diameter of the wafer W is set to 150 mm (6
Inch), in order to complete the exposure of a row of shot areas corresponding to the diameter of the wafer by only one continuous X-direction scan, the reticle is assumed to use a 1 / 5-fold projection lens system. Is 7 in the scanning direction (X direction)
This is because it has reached 50 mm (30 inches), and it is extremely difficult to manufacture such a reticle.

Even if such a reticle can be manufactured, a stroke of a reticle stage for scanning the reticle in the X direction needs to be 750 mm or more.
It is essential that the device be extremely large. For this reason,
Even a device such as the one disclosed in the above publication has no choice but to perform zigzag scanning. Therefore, shot areas adjacent to each other in the scanning exposure direction, for example, shot areas SA1 and SA in FIG.
With No. 12, it was necessary to widely cover the periphery of the pattern area on the reticle with a light shield so that the reticle pattern was not transferred to the adjacent shot area.

FIG. 10 shows a hexagonal illumination area HIL, a circular image field IF of a projection lens system, and a reticle R.
FIG. 10A shows a state where the hexagonal illumination area HIL is set at the scan start position on the reticle R, and from this state, only the reticle R moves rightward in FIG. Move one dimension. At the end of one scan, the result is as shown in FIG.

In FIG. 10, CP1, CP2, ... CP
Each of 6 is a chip pattern formed side by side in the X direction on the reticle R, and the array of these 6 chip patterns corresponds to the shot area to be exposed by one scan in the X direction. In the figure, the hexagonal illumination area HI
The center point of L substantially coincides with the center of the image field IF, that is, the optical axis AX of the projection lens system.

As is apparent from FIG. 10, at the scanning start portion and the scanning end portion on the reticle R, a light shield having at least the width dimension of the hexagonal illumination area HIL in the scanning direction is required outside the pattern area. And At the same time, the reticle R itself has a large dimension in the scanning direction, and the moving stroke in the X direction of the reticle stage is the sum of the dimension in the X direction of the chip patterns CP1 to CP6 as a whole and the dimension in the scanning direction of the hexagonal illumination area HIL. There may be some problems in making it into a device, such as the fact that only the amount required.

A more important problem is that the projection optical system has a 1/4
In the case of the reduction, the scanning speed of the reticle R becomes four times as fast as the scanning speed of the wafer W, and it is necessary to adopt a reticle stage having a high-speed moving performance while maintaining sufficient straightness. is there. In particular, as the movement stroke required for one scanning exposure becomes larger, it becomes more difficult to maintain the straightness of the reticle stage (so-called yawing characteristic) with sufficient accuracy.

In the case of the reduced projection system, the minute displacements of the reticle in the X and Y directions are reduced by the projection magnification on the wafer, but the relative rotational displacements of the reticle and the wafer are not reduced, but on the wafer. It is reflected as it is as the rotation of the image transferred to. Therefore, in view of such a problem, the present invention reduces the relative rotation error between the reticle (mask) and the wafer (substrate) during scanning exposure, and improves the quality of the transferred image by the scanning method (or S & S). Method) and a scanning exposure method.

[0017]

According to the present invention, a part of the circuit pattern (CPn) formed on the mask (reticle R) is illuminated with illumination light limited to a predetermined shape (shape of the opening AP of the blind mechanism 20). An illuminating means (lamp 2 to condenser lens 28) for irradiating, a projection optical system (PL) for projecting an image of a part of the circuit pattern illuminated by the illuminating light onto the photosensitive substrate (W), and a mask are held. A mask stage (30) that moves in at least a first direction (X direction) and a substrate stage (44, 46, 48) that holds a photosensitive substrate and moves in at least a first direction, and includes a mask stage and a substrate stage. It is applied to an apparatus for scanning and exposing the entire image of a circuit pattern on a photosensitive substrate by synchronous scanning of.

The characteristic configuration of the apparatus according to the present invention is that the first interferometer (38) for sequentially measuring the yawing amount of the mask stage (30) generated during the scanning exposure and the substrate stage generated during the scanning exposure. The second interferometer (50) that sequentially measures the yawing amount of (48) and the first interferometer (3
8) and the second interferometer (50) so that the difference in each yawing amount is constant, at least one of the mask and the photosensitive substrate is irradiated with illumination light on the mask or on the photosensitive substrate. Control means (34, 54, 10) for correcting minute rotation during scanning exposure while centering on the projection area of the circuit pattern of
0) and are provided.

Further, according to the present invention, a reduced projection optical system (PL) is provided for a part of the image of the circuit pattern (CPn) on the mask (reticle R) irradiated with illumination light having a predetermined shape (rectangular shape or slit shape). The mask stage (30) for holding the mask and the substrate stage (44, 46, 48) for holding the photosensitive substrate are projected on the photosensitive substrate (wafer W) via the above according to the projection magnification of the reduction projection optical system. This method is applied to a method of scanning and exposing the entire image of the circuit pattern on the photosensitive substrate by moving the image in one dimension relatively at a speed ratio (for example, 1: 5).

The characteristic configuration of the method according to the present invention is that the minute difference between the mask and the photosensitive substrate caused by each yawing of the mask stage (30) and the substrate stage (48) during scanning exposure. Relative rotation error is measured by interferometer (3
(8, 50) and the reduction projection optics during the scanning exposure of either the mask or the photosensitive substrate so that the relative rotation error measured during the scanning exposure is maintained at a predetermined value. Projection field of view (PL) (Image field I
F) is a step of performing a minute rotation correction around a predetermined area in F).

As described above, according to the present invention, when the mask or the like is slightly rotated during the scanning exposure so that the relative rotation error between the mask and the photosensitive substrate that occurs during the scanning exposure is corrected, the center of rotation of the mask is always projected. It is characterized in that it is set in a predetermined area within the projection visual field of, for example, the center (optical axis position) of the illumination light irradiation area on the mask.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Now, each embodiment of the present invention will be described with reference to the drawings. First, FIG. 1 shows the structure of a projection exposure apparatus according to a first embodiment of the present invention. In this embodiment, a bilateral telecentric 1/5 reduction refracting element alone or a combination of a refracting element and a reflecting element is used. The projection optical system PL (hereinafter simply referred to as a projection lens for simplicity) PL is used.

The exposure illumination light from the mercury lamp 2 is focused on the second focus by the elliptical mirror 4. At this second focal point, a rotary shutter 6 that switches between blocking and transmission of illumination light by a motor 8 is arranged. The illumination light flux passing through the shutter 6 is reflected by the mirror 10 and is reflected by the input lens 12.
, And enters the fly-eye lens system 14. Many secondary light source images are formed on the exit side of the fly-eye lens system 14, and illumination light from each secondary light source image is
The light is incident on a lens system (condenser lens) 18 through 6.

On the rear focal plane of the lens system 18, movable blades BL1, BL2, B of the reticle blind mechanism 20 are provided.
L3 and BL4 are arranged as shown in FIG. Each of the four blades BL1, BL2, BL3, BL4 has a drive system 2
2 are moved independently. In this embodiment, blade B
X direction (scanning exposure direction) depending on the edges of L1 and BL2
Of the opening AP of the blades BL3 and BL4 is determined by the edges of the blades BL3 and BL4.
Shall be determined.

The shape of the aperture AP defined by the edges of the four blades BL1 to BL4 is the projection lens PL.
Of the circular image field IF. Now, at the position of the blind mechanism 20, the illumination light has a uniform illuminance distribution, and the opening A of the blind mechanism 20
The illumination light that has passed through P illuminates the reticle R via the lens system 24, the mirror 26, and the main condenser lens 28.

At this time, the image of the aperture AP defined by the four blades BL1 to BL4 of the blind mechanism 20 is formed on the pattern surface of the lower surface of the reticle R. The lens system 24
Although an arbitrary imaging magnification can be given by the condenser lens 28 and the condenser lens 28, it is assumed here that the aperture AP of the blind mechanism 20 is enlarged by about 2 times and projected onto the reticle R. Therefore, the scanning speed Vrs of the reticle R during scan exposure and the blind mechanism 2 projected on the reticle R
In order to match the moving speed of the edge image of the blades BL1 and BL2 of 0, the moving speed Vbl of the blades BL1 and BL2 in the X direction may be set to Vrs / 2.

The reticle R that has received the illumination light defined by the opening AP is held on the column 32 by the reticle stage 30 that is movable at a constant speed in at least the X direction. Although not shown, the column 32 is integrated with a column for fixing the lens barrel of the projection lens PL. Reticle stage 3
In the case of 0, the drive system 34 performs one-dimensional scanning movement in the X direction, fine rotation movement for yawing correction, and the like.

A movable mirror 36 for reflecting the length measuring beam from the laser interferometer 38 is fixed to one end of the reticle stage 30, and the position of the reticle R in the X direction and the yawing amount (minute rotation amount) are measured by the laser interferometer 38. Is measured in real time by. A fixed mirror (reference mirror) 40 for the laser interferometer 38 is fixed to the upper end of the lens barrel of the projection lens PL.

The image of the pattern formed on the reticle R is reduced to 1/5 by the projection lens PL and imaged on the wafer W. The wafer W is a micro-rotatable wafer holder 4
4 is held together with the reference mark plate FM. Holder 44
Is a Z that can be finely moved in the direction of the optical axis AX (Z) of the projection lens PL.
It is provided on the stage 46. The Z stage 46 is provided on an XY stage 48 that two-dimensionally moves in the X and Y directions, and the XY stage 48 is driven by a drive system 54.

The coordinate position of the XY stage 48 and the yawing amount (minute rotation amount) are measured by the laser interferometer 50, and the fixed mirror 42 for the laser interferometer 50 is fixed to the lower end of the lens barrel of the projection lens PL. And the moving mirror 52 moves to Z
It is fixed to one end of the stage 46. Since the projection magnification is set to 1/5 in the present embodiment, the moving speed Vws of the XY stage 48 in the X direction during scan exposure is determined by the reticle stage 3.
It is ⅕ of zero velocity Vrs. Further, in the present embodiment, the TT for detecting the alignment mark (or the reference mark FM) on the wafer W via the reticle R and the projection lens PL.
R (through the reticle) type alignment system 6
0 and the alignment mark (or the reference mark F) on the wafer W from the space below the reticle R via the projection lens PL.
Alignment system 62 of the TTL (through the lens) system for detecting M) is provided, and the relative alignment between reticle R and wafer W is performed before the start of S & S exposure or during scan exposure.

The photoelectric sensor 64 shown in FIG.
When the reference mark FM is of a light emission type, the light from the light emission mark is received through the projection lens PL, reticle R, condenser lens 28, lens systems 24 and 18, and beam splitter 16, and the XY stage 48 It is used when defining the position of the reticle R in the coordinate system or when defining the position of the detection center of each alignment system 60, 62.

By the way, the opening AP of the blind mechanism 20
Is a rectangular shape (slit shape) that is as long as possible in the Y direction orthogonal to the scanning direction (X direction).
The number of times of scanning in the direction, that is, the number of times of stepping the wafer W in the Y direction can be reduced. However, depending on the size, shape, and arrangement of the chip pattern on the reticle R, the length of the opening AP in the Y direction may be set to the blades BL3 and BL4.
It may be better to change at each edge of. For example, the opposing edges of the blades BL3 and BL4 may be adjusted so as to be aligned with the street line that defines the shot area on the wafer W. By doing so, it is possible to easily cope with the size change of the shot area in the Y direction.

When the size of one shot area in the Y direction is equal to or larger than the maximum size of the opening AP in the Y direction, as shown in the above-mentioned Japanese Patent Laid-Open No. 2-229423, the overlap occurs inside the shot area. It is necessary to perform exposure to make the exposure amount seamless. The method in this case will be described later in detail. Next, the operation of the apparatus according to the present embodiment will be described.
0 is managed collectively. The basic operation of the main control unit 100 includes position information from the laser interferometers 38 and 50,
Based on the input of yawing information, the input of speed information from a tachogenerator or the like in the drive systems 34 and 54, the reticle stage 30 and the XY stage 48 are maintained at a predetermined speed ratio during scan exposure, The relative movement with respect to the pattern is kept within a predetermined alignment error.

In addition to its operation, the main controller 100 of this embodiment moves the edge positions of the blades BL1 and BL2 in the scanning direction of the blind mechanism 20 in the X direction in synchronization with the scanning of the reticle stage 30. , Drive system 22
The main feature of this is that it is controlled interlockingly. When the illumination light amount at the time of scanning exposure is constant, the reticle stage 3 becomes larger as the maximum opening width of the opening AP in the scanning direction increases.
0, the absolute speed of the XY stage 48 must be increased. In principle, when the same exposure amount (dose amount) is given to the resist on the wafer W, if the width of the opening AP is doubled, the XY stage 48 and the reticle stage 3
Zero must also be twice as fast.

FIG. 3 shows the positional relationship between the reticle R that can be mounted on the apparatus shown in FIGS. 1 and 2 and the opening AP of the blind mechanism 20. Here, four chip patterns CP1, CP2, CP3 are provided on the reticle R. , CP4 are arranged in the scanning direction. Each chip pattern is defined by a light-shielding band corresponding to a street line, and the periphery of a pattern collection region (shot region) is surrounded by a light-shielding band having a width Dsb wider than the street line.

Here, it is assumed that the left and right light-shielding bands around the shot area on the reticle R are SBl and SBr, and the reticle alignment marks RM1 and RM2 are formed outside them. The opening AP of the blind mechanism 20
Has an edge E1 of the blade BL1 and an edge E2 of the blade BL2 extending parallel to the Y direction orthogonal to the scanning direction (X direction), and the width of the edges E1 and E2 in the scanning direction is Dap. Further, the length of the opening AP in the Y direction is substantially equal to the width of the shot area on the reticle R in the Y direction, and the edge defining the longitudinal direction of the opening AP is aligned with the center of the light shielding band extending in the X direction in the periphery. Blades BL3, BL
4 is set.

Next, with reference to FIG. 4, the state of S & S exposure of this embodiment will be described. Here, it is assumed that the reticle R and the wafer W shown in FIG.
It is assumed that relative alignment is performed using 0, 62, photoelectric sensor 64 and the like. FIG. 4 shows the reticle R of FIG. 3 as viewed from the side, and here, the blade BL of the blind mechanism 20 is shown.
1. To make the operation of BL2 easier to understand, reticle R
The blades BL1 and BL2 are shown just above.

First, as shown in FIG. 4A, the reticle R
Is set as the scanning start point in the X direction. Similarly, one corresponding shot area on the wafer W is set to start scanning in the X direction. At this time, the image of the aperture AP illuminating the reticle R ideally desirably has a width Dap of zero, but it is difficult to completely eliminate the width Dap due to the condition of the edges E1 and E2 of the blades BL1 and BL2. .

Therefore, in this 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, shading band S
The width Dsb of Br is about 4 to 6 mm, and the width Dap of the image of the aperture AP on the reticle is preferably about 1 mm. Then, as shown in FIG. 4A, the center of the opening AP in the X direction is shifted by ΔXs with respect to the optical axis AX in the direction opposite to the scanning direction of the reticle R (left side in the figure).

The distance ΔXs is set to about half of 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 Y direction, the maximum value DAmax of the width Dap of the opening AP in the X direction is also determined by the diameter of the image field IF. Come on. The maximum value DAmax is calculated in advance by the main control unit 100. Further, assuming that the width (minimum) of the aperture AP at the scanning start point in FIG. 4A is DAmin, strictly speaking, DAmin + 2
The distance ΔXs is determined so as to satisfy the relationship ΔXs = DAmax.

Next, the reticle stage 30 and the XY stage 48 are moved in mutually opposite directions at a speed ratio proportional to the projection magnification. At this time, as shown in FIG. 4B, of the blind mechanism 20, the blade B in the traveling direction of the reticle R
Only L2 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.

When the scanning of the reticle R progresses and the edge E2 of the blade BL2 reaches the position defining the maximum opening width of the opening AP as shown in FIG. 4C, the movement of the blade BL2 is stopped thereafter. Therefore, the drive system 22 of the blind mechanism 20 is provided with an encoder, a tacho-generator, etc. for monitoring the moving amount and moving speed of each blade, and the position information and speed information from these are provided to the main control unit 10.
0 and is used to synchronize with the scanning movement of the reticle stage 30.

In this way, the reticle R has the maximum opening AP.
While being illuminated by the illumination light passing through, the light is sent in the X direction at a constant speed and reaches the position shown in FIG. That is, the edge E of the blade BL1 in the direction opposite to the direction of travel of the reticle R
1 is a light-shielding band S on the left side of the shot area of the reticle R.
4E, the image of the edge E1 of the blade BL1 is run in the same direction in synchronization with the moving speed of the reticle R, as shown in FIG.

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 and the width Dap of the opening AP becomes the minimum value DAmin). , The movement of the reticle stage 30 and the blade BL1 is stopped. With the above operation, exposure by one scan of the reticle (exposure for one shot) is completed, and the shutter 6 is closed. However, when the width Dap of the opening AP is sufficiently narrower than the width Dsb of the light-shielding band SBl (or SBr) at that position and the illumination light leaking to the wafer W can be reduced to zero, the shutter 6 remains open. It may be.

Next, the XY stage 48 is stepped in the Y direction for one row of the shot area, and the XY stage 48 and the reticle stage 30 are scanned in the opposite direction to the same as the other shot areas on the wafer W. Perform scan exposure. According to the present embodiment described above, the stroke of the reticle stage 30 in the scanning direction can be minimized, and the widths Dsb of the light-shielding bands SBl and SBr that define both sides of the shot area in the scanning direction can be reduced. There are advantages.

It should be noted that, until the reticle stage 30 accelerates from the state of FIG. 4 (A) to uniform speed scanning, uneven exposure amount in the scanning direction occurs on the wafer W. Therefore, at the start of scanning, it is necessary to determine a prescan (running) range until the state shown in FIG. In that case, the width Dsb of the light-shielding bands SBr and SBl is increased according to the length of the pre-scan. This also applies when overscanning is required in response to the fact that the uniform velocity motion of the reticle stage 30 (XY stage 48) cannot be stopped abruptly at the end of one scan exposure. .

However, even when performing prescanning and overscanning, when the shutter 6 is set to a high speed and the open response time (time required from the fully closed state of the shutter to the full open) and the closing response time are sufficiently short, When the reticle stage 30 completes the pre-scan (acceleration) and enters the main scan (position in FIG. 4A), or when the main scan shifts to overrun (deceleration), the shutter 6 is interlocked. Just open and close it.

For example, the uniform scanning speed of the reticle stage 30 during the main scan is Vrs (mm / sec), and the light blocking bands SBl and S.
Assuming that the width of Br is Dsb (mm) and the minimum width of the opening AP on the reticle R is DAmim (mm), the response time ts of the shutter 6 satisfies the following relationship under the condition of Dsb> DAmin. If you have. (Dsb-DAmin) / Vrs> ts In the apparatus of this embodiment, the yawing amount of the reticle stage 30 and the yawing amount of the XY stage 48 are independently measured by the laser interferometers 38 and 50, respectively. The main controller 100 finds the difference in yawing amount, and the reticle stage 30 or the wafer holder 44 is finely rotated during scan exposure so that the difference becomes zero. However, in that case, the center of rotation of the minute rotation is always the opening A.
It is necessary to set it at the center of P (that is, the optical axis AX of the projection lens PL). Considering the structure of the apparatus, there is a method of slightly rotating the guide portion of the reticle stage 30 in the X direction about the optical axis AX. Easy to implement.

FIG. 5 shows a pattern arrangement example of the reticle R which can be mounted on the apparatus shown in FIGS. 1 and 2, and the chip patterns CP1, CP2, CP3 are the reticle R shown in FIG.
In the same manner as described above, it is used to expose a wafer by a step-and-scan method using illumination light from a slit-shaped opening AP. The other chip patterns CP4 and CP5 formed on the same reticle R are used to expose a wafer by a step-and-repeat (S & R) method.

The blind mechanism 2 is used properly in this way.
For example, when exposing the chip pattern CP4, the reticle stage 30 is moved so that the pattern center of the chip pattern CP4 coincides with the optical axis AX when exposing the chip pattern CP4. At the same time, it is only necessary to match the shape of the opening AP with the outer shape of the chip pattern CP4. Then, only the XY stage 48 needs to be moved in the stepping mode. With the reticle pattern shown in FIG. 5 as described above, the S & S exposure and the S & R exposure can be selectively performed by the same apparatus without changing the reticle.

FIG. 6 shows the blind mechanism 20 corresponding to the case where the size of the chip pattern on the reticle to be exposed in the direction (Y direction) orthogonal to the scanning direction is larger than the image field IF of the projection optical system. An example of the shapes of the blades BL1 to BL4 is shown, and the edges E1 and E2 that define the width of the opening AP in the scanning direction (X direction) extend in parallel to the Y direction as in FIG. Although the edges E3 and E4 defining the longitudinal direction of are parallel to each other, they are inclined with respect to the X axis, and the opening AP becomes a parallelogram (rectangle).

In this case, the four blades BL1 to BL4
Moves in the X and Y directions in conjunction with the movement of the reticle during scan exposure. However, the blade BL in the scan exposure direction
The moving speed Vbx in the X direction of the images of the edges E1 and E2 of 1 and BL2 is almost the same as the scanning speed Vrs of the reticle,
When it is necessary to move the blades BL3 and BL4, the moving speed Vby of the edges E3 and E4 in the Y direction is Vby when the inclination angle of the edges E3 and E4 with respect to the X axis is θe.
It is necessary to synchronize with the relation of = Vbx · tan θe.

FIG. 7 shows the S & S according to the opening shape shown in FIG.
7 schematically shows a scanning sequence at the time of S exposure. In FIG. 7, the aperture AP is considered as being projected on the reticle R, and is shown by its edges E1 to E4. In the second embodiment shown in FIGS. 6 and 7, it is assumed that the chip pattern region CP on the reticle R to be projected on the wafer W has a size about twice the size of the opening AP in the longitudinal direction. Therefore, in the second embodiment, the reticle stage 30 is also structured to precisely step in the Y direction orthogonal to the scanning direction.

First, the blades BL1 and BL2 in FIG. 6 are adjusted to set the state as shown in FIG. 7A at the start of scanning. That is, the aperture AP with the narrowest width is located on the right shading band SBr of the reticle R, and the edge E1 on the left side of the aperture AP is at the position farthest from the optical axis AX (the aperture AP is Set it to the edge position when it is most widened in the X direction.

Further, in FIG. 7, regions Ad and As extending like a belt in the scanning direction (X direction) are portions where the exposure amount is insufficient in one scanning exposure. The areas Ad and As are formed by the openings AP.
This occurs because the upper and lower edges E3 and E4 of the areas Ad and As in the Y direction are the inclination angles .theta.e of the edges E3 and E4 and the edge E1.
And the maximum opening width DAmax of E2, DAmax.t
It is uniquely determined as anθe. Of the areas Ad and As where the exposure amount unevenness occurs, the area Ad set in the pattern area CP is scanned and exposed by overlapping the triangular portions formed by the edges E3 and E4 of the opening AP in the Y direction. Thus, the exposure amount is made uniform.
Further, the other area As is exactly aligned with the light-shielding band on the reticle R.

Now, from the state shown in FIG. 7A, the reticle R and the edge E2 (blade BL2) are run at approximately the same speed in the + X direction (right side in the figure). Eventually, as shown in FIG. 7B, the width of the opening AP in the X direction becomes maximum, and the edge E
Stop moving 2 as well. In the state shown in FIG. 7B, the center of the opening AP substantially coincides with the optical axis AX. After that, only the reticle R moves at a constant velocity in the + X direction, and from the time when the left edge E1 of the opening AP enters the left light-shielding band SBl as shown in FIG. 7C, the edge E1 (blade BL1) becomes the reticle R. Move to the right (+ X direction) at almost the same speed. Thus, the lower half of the chip pattern area CP is exposed, and the reticle R and the opening AP are stopped in a state as shown in FIG.

Next, the reticle R is precisely stepped in the -Y direction by a fixed amount. The wafer W is similarly stepped in the + Y direction. Then, a state as shown in FIG. At this time, the overlap area Ad is overlapped and exposed in the triangular portion defined by the edge E4.
The relative positional relationship in the direction is set. At this time, the opening A
When it is necessary to change the length of P in the Y direction, the edge E
3 (Blade BL3) or Edge E4 (Blade BL3
4) Move and adjust in the Y direction.

Next, the reticle R is scanned and moved in the -X direction, and the edge E1 (blade BL1) is moved in conjunction with the -X direction. Then, when the opening width by the edges E1 and E2 becomes maximum as shown in FIG. 7F, the movement of the edge E1 is stopped and only the reticle R is continuously moved in the −X direction at a constant velocity. By the above operation, a large chip pattern area CP having a size larger than the dimension of the image field of the projection optical system in the Y direction can be exposed on the wafer W. Moreover, the overlap area Ad is set and the opening AP
Both ends (triangle part) where the amount of exposure is insufficient due to the shape of
Is overlapped by two scanning exposures, the area Ad
The amount of exposure inside is also made uniform.

FIG. 8 shows another blade shape of the blind mechanism 20, which defines blades BL1 and BL for defining the scanning direction.
The edges E1 and E2 of 2 are straight lines parallel to each other, and the edges of the blades BL3 and BL4 in the direction orthogonal to the scanning direction are triangular shapes symmetrical with respect to the Y axis passing through the optical axis AX. Here, the edges of the blades BL3, BL4 have a complementary shape so that they can shield light almost completely as they approach each other in the Y direction. Therefore, the shape of the opening AP can be a so-called chevron shape. In the case of such a chevron shape as well, if overlap exposure is performed in the triangular portions at both ends, uniformity can be similarly achieved.

In each of the above embodiments, the projection exposure apparatus is premised. However, in the proximity aligner in which the mask and the wafer are brought close to each other and the mask and the wafer are integrally scanned with respect to irradiation energy (X-ray, etc.). The same method can also be used for. As described above, according to each embodiment of the present invention, the blind mechanism 20 does not irradiate the mask with the illumination light through the fixed opening (hexagonal shape, arcuate shape, etc.) as in the conventional scanning exposure method. Since the width of the aperture AP (variable field diaphragm) in the scanning direction is changed in conjunction with reticle scanning or wafer scanning, the reticle stage does not have to be largely overrun at the scanning start portion or the scanning end portion on the reticle. The same S & S exposure method can be realized by simply decreasing the width of the opening AP.

Therefore, since the overrun of the reticle stage is unnecessary or can be made extremely small, the moving stroke of the reticle stage can be minimized and the width of the light shield formed around the pattern forming area on the reticle can be minimized. The number is as small as that of the conventional reticle, and there is an advantage that the labor for inspecting the pinhole defect in the light shield (usually a chromium layer) at the time of manufacturing the reticle is reduced.

Further, by setting the shape of the opening AP of the blind mechanism 20 to match the pattern forming area on the reticle, it can be used as a stepper equivalent to the conventional one. Further, by configuring the blind mechanism 20 to change the aperture position and the geometrical shape of the variable field stop in one-dimensional, two-dimensional or rotational directions within the image field of the projection optical system, various chip sizes can be obtained. It is also possible to respond to the mask pattern instantly.

[0063]

As described above, according to the present invention, when the mask and the photosensitive substrate are moved relative to the image field of the projection optical system for scanning exposure, they occur during the relative movement of the mask and the photosensitive substrate. Relative rotation error (yawing) is precisely corrected,
There is an advantage that the quality of the image projected on the photosensitive substrate is improved. There is also an advantage that the overlay accuracy with the projected image of the mask pattern that is overlaid and exposed on the pattern area (shot area) already formed on the photosensitive substrate is improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a projection exposure apparatus according to an embodiment of the present invention.

FIG. 2 is a plan view showing a blade shape of the blind mechanism.

FIG. 3 is a plan view showing a pattern arrangement of a reticle suitable for the apparatus shown in FIG. 1;

FIG. 4 is a view for explaining a scanning exposure operation in the embodiment of the present invention.

FIG. 5 is a plan view showing another pattern arrangement of a reticle that can be mounted on the apparatus of FIG. 1;

FIG. 6 is a plan view showing a blade shape of a blind mechanism according to a second embodiment.

FIG. 7 is a view for explaining a sequence of step & scan exposure according to the second embodiment.

FIG. 8 is a plan view showing another blade shape.

FIG. 9 is a view for explaining the concept of a conventional step-and-scan exposure method using arc-shaped slit illumination light.

10A and 10B are views for explaining a conventional scan exposure system using regular hexagonal illumination light.

[Description of Signs of Main Parts]

 R reticle PL projection optical system IF circular image field W wafer AP aperture 20 blind mechanism 30 reticle stage 34 drive system 38 laser interferometer 48 XY stage 50 laser interferometer 54 drive system 100 main control system.

Claims (6)

(57) [Claims] 1. An illumination means for irradiating a part of a circuit pattern formed on a mask with illumination light limited to a predetermined shape,
A projection optical system for projecting an image of a part of the circuit pattern illuminated by the illumination light onto a photosensitive substrate, a mask stage for holding the mask and moving in at least a first direction, and holding the photosensitive substrate. And a substrate stage that moves in at least the first direction, and that exposes the entire image of the circuit pattern onto the photosensitive substrate by the synchronous scanning of the mask stage and the substrate stage. A first interferometer that sequentially measures the amount of yawing of the mask stage that occurs; a second interferometer that sequentially measures the amount of yawing of the substrate stage that occurs during the scanning exposure; the first interferometer and the second interferometer At least one of the mask and the photosensitive substrate so that the difference between the yawing amounts measured by And a control means for correcting minute rotation correction during the scanning exposure while centering on the projection area of the circuit pattern on the photosensitive substrate. 2. The projection optical system has a circular image field, and the control means always performs minute rotation correction of the mask or the photosensitive substrate during the scanning exposure with the optical axis position in the circular image field as the center. An apparatus according to claim 1, characterized in that 3. A rectangular or slit-shaped intensity distribution set in such a manner that the illumination means extends in a direction orthogonal to the first direction within a circular image field of the projection optical system and includes the optical axis position. 3. The apparatus according to claim 2, further comprising a shaping optical member for irradiating the mask with the illumination light. 4. The projection optical system is a double-sided telecentric reduction projection optical system configured by only a refractive optical element or a combination of a refractive optical element and a reflective optical element. The described device. 5. The control means finely corrects the mask stage during the scanning exposure so that the difference between the yawing amounts measured during the scanning exposure is constant. The apparatus according to item 4. 6. A mask stage for holding the mask while projecting an image of a part of a circuit pattern on the mask irradiated with illumination light of a predetermined shape onto a photosensitive substrate through a reduction projection optical system, and the photosensitive layer. A method of scanning and exposing the entire image of the circuit pattern onto the photosensitive substrate by relatively one-dimensionally moving a substrate stage for holding a substrate and a speed ratio corresponding to a projection magnification of the reduction projection optical system, Using an interferometer to measure a minute relative rotation error between the mask and the photosensitive substrate caused by each yawing of the mask stage and the substrate stage during scanning exposure; In order to maintain the measured relative rotation error at a predetermined constant value, a predetermined area within the projection visual field of the reduction projection optical system is always provided during scanning exposure of either the mask or the photosensitive substrate. Scanning exposure method, characterized in that the Focusing and a step of micro rotation correction.