JPH0855793A - Scanning exposure method and scanning aligner - Google Patents

Abstract

PURPOSE:To improve the throughput by shifting a photosensitive substrate in the direction of primary scanning at a speed rate geared to the magnification of a projective optical system, at the same time with shifting a mask at a specified speed in the direction of primary scanning so that it may relatively scan the rectangular region on a mask with illumination light. CONSTITUTION:The image of the pattern on a reticle R arranged on the side of the object face of a projection lens PL is scaled down to 1/5 by a protective lens PL, and an image is formed on a wafter W arranged on the side of an image face. Since the magnification of projection is made 1/5, the shifting speed in X direction of an X-Y stage 48 is 1/5 of the speed of a reticle stage 30. And, relative alignment between the reticle R and the wafer W is made by providing a TTR method of alignment system 60, which detects the alignment mark on the wafer W through the reticle R and the projection lens PL, and a system 62, which detects the alignment mark on the wafer W through the projection lens PL from the space under the reticle R.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a method of scanning and exposing a mask pattern on a photosensitive substrate in a lithography process during the manufacturing process of semiconductor devices, liquid crystal display devices and the like, and to be used for implementing the method. The present invention relates to a scanning exposure device.

[0002]

2. Description of the Related Art Conventionally, projection exposure apparatuses used in this type of lithography process are roughly classified into two types, one having an exposure field capable of including the entire pattern of a mask (reticle). A method of exposing a photosensitive substrate such as a wafer or a plate through a projection optical system by a step-and-repeat method is another method, in which the mask and the photosensitive substrate are opposed to each other with the projection optical system sandwiched therebetween, and arc-shaped slit illumination light This is a scanning method of performing relative scanning and exposure under mask illumination.

The 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 the latter aligner adopting the scan exposure method. Both are becoming more expensive, and steppers are expected to remain the mainstream for some time to come.

By the way, recently, a new method for achieving high resolution even in the scan exposure method is 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 is one-dimensional scanning of a mask (reticle),
This is a mixture of a scanning method in which the wafer is one-dimensionally scanned at a speed synchronized with it and a method in which the wafer is stepwise 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. Here, the array of shot areas (one chip or multi-chip) in the X direction on the wafer W is arranged by the arc-shaped slit illumination light RIL. Scanning exposure is performed and the wafer W is stepped in the Y direction. In the figure, arrows indicated by broken lines represent 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 shot areas SA7, SA8, ... S arranged in the center of the wafer W in the Y direction.
The same S & S exposure is performed in the order of A12.

In the S & S type aligner disclosed in the above-mentioned document, the image of the reticle pattern illuminated by the arc-shaped slit illumination light RIL is imaged on the wafer W via the 1 / 4-fold 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 as a projection optical system that uses a reduction system that is a combination of a refraction element and a reflection element. This is to obtain the advantage that various aberrations become almost zero. An example of such a catoptric reduction projection system is described, for example, in USP. 4,747,678
Is disclosed in.

S using such an arc-shaped slit illumination light
In addition to the & S exposure method, a normal projection optical system with a circular image field (full field type)
An attempt to apply it to the S exposure method is disclosed in, for example, Japanese Patent Laid-Open No. 2-229.
No. 423 was proposed. In this publication, the shape of exposure light for illuminating a reticle (mask) is a regular hexagon inscribed in a circular field of a projection lens system, and the edges of two sides of the regular hexagon facing each other are perpendicular to the scanning exposure direction. It is disclosed that S & S exposure with further improved throughput is realized by increasing the length.

That is, in this publication, the scanning speed of the reticle stage and wafer stage is set to be as large as possible in the reticle (mask) illumination area in the scan exposure direction, as compared with the S & S exposure method using arc-shaped slit illumination light. It is shown that it can be made extremely high.

[0009]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
According to the conventional technique disclosed in Japanese Patent No. 9423, the mask illumination area in the scanning exposure direction is made as wide as possible, which is advantageous in throughput. However, considering the actual scanning sequence of the mask stage and the wafer stage, even in the apparatus disclosed in the above publication,
There is no choice but to use the zigzag S & S system as shown in FIG.

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

Even if such a reticle can be manufactured, since the stroke of the reticle stage for scanning the reticle in the X direction requires 750 mm or more,
It is essential that the device be extremely large. For this reason,
Even with the device disclosed in the above-mentioned publication, there is 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 SA12 in FIG.
Then, 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 the projection lens system, and a reticle R.
10A shows the arrangement at the time of scanning exposure, and FIG. 10A shows a state in which the hexagonal illumination area HIL is set at the scan start position on the reticle R. From this state, only the reticle R moves to the right in the figure. Move one dimension. Then, 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, outside the pattern area, at least the width dimension of the hexagonal illumination area HIL in the scanning direction (X direction) is larger than the width dimension. Requires a light shield. 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.

There is also a problem in the shape of the illumination area in the Y direction orthogonal to the scanning direction, and in the case of the hexagonal illumination area HIL as shown in FIG. 10, the Y direction of the chip pattern on the reticle R (non-scanning direction). Although the dimension of is constant, the dimension of the illumination area HIL in the Y direction changes into a mountain shape according to the position in the X direction. Therefore, in the case of the chip pattern as shown in FIG. 10, the dimension Y in the Y direction in which the width in the X direction is constant in the hexagonal illumination area HIL.
D becomes smaller than the size of the chip pattern in the Y direction, and the reticle R (wafer W) is scanned only once in FIG.
Even when the chip pattern group is exposed, a remarkable unevenness of the exposure amount occurs due to the mountain-shaped portion of the illumination area HIL.

In view of this, Japanese Patent Laying-Open No. 2-229423 discloses that when the dimension of the chip pattern in the Y direction is YD or more,
It has been shown that the chip pattern group of the reticle R is transferred onto the wafer by scanning exposure (overlapping) twice or more, but this is not necessarily advantageous in terms of throughput. The present invention, in view of the above problems,
A scanning method (or S & S) that improves throughput without providing a particularly wide light shield around the pattern exposure area on the reticle (mask) and minimizing the movement stroke of the reticle (mask) stage during scanning exposure.
An object of the present invention is to provide a scanning exposure method of S method) and an exposure apparatus therefor.

[0017]

According to the present invention, a mask (R) arranged on the object plane side of a projection optical system (PL) having a circular image field (IF) and an image plane side of the projection optical system are arranged. The photosensitive substrate (W) to be formed is one-dimensionally scanned relative to a circular image field, so that the entire circuit pattern formed in the rectangular area on the mask is scanned and exposed on the photosensitive substrate. To be done.

The characteristic construction of the method is that the non-scanning direction (Y direction) intersects the one-dimensional scanning direction (X direction).
Illumination light having an intensity distribution that is limited to a substantially rectangular shape or a slit shape that linearly extends in the direction of the axis and that includes the center (point through which the optical axis AX passes) of the circular image field on the object plane side of the projection optical system. The step of irradiating (the transmitted light of the opening AP of the blind mechanism 20 of the illumination system) toward the mask, and the illumination light having a rectangular or slit-shaped intensity distribution crosses the rectangular area on the mask from one end side to the other end side. The mask is moved in the one-dimensional scanning direction at a predetermined speed (Vrs) so that relative scanning is performed, and at the same time, the photosensitive substrate is moved at a speed ratio (Vrs / 5) corresponding to the magnification (eg, 1/5) of the projection optical system. And a step of moving in the one-dimensional scanning direction.

Further, according to the present invention, the mask (R) held on the object plane side of the projection optical system (PL) having the circular image field (IF) is at least in the first direction (X direction) with respect to the circular image field. A mask stage (30) for moving and a substrate stage (44, 46, 48) for moving the photosensitive substrate (W) exposed with the image of the circuit pattern (Cpn) of the mask projected by the projection optical system in at least the first direction. ) And the mask stage and the substrate stage are synchronously moved in the first direction to scan and expose the entire image of the circuit pattern of the mask on the photosensitive substrate.

The characteristic configuration of the apparatus according to the present invention is limited to a substantially rectangular shape or a slit shape linearly extending in the second direction (Y direction) intersecting the first direction during scanning exposure, and Irradiating the mask with illumination light (transmission light of the aperture AP of the blind mechanism 20) having an intensity distribution set so as to include the center (point through which the optical axis AX passes) of the circular image field on the object plane side of the projection optical system. The illuminating means (lamp 2 to condenser lens 28) is provided.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the conventional scanning exposure method, the mask was irradiated with illumination light limited to a hexagonal shape or an arc shape, but in the present invention, the width in the scanning direction is almost constant and the projection optical system is used. Scanning exposure was performed while irradiating the mask with illumination light limited to a slit shape (rectangular shape) extending in the diameter direction of the circular image field of the system. Therefore, the same S & S exposure method can be realized without overrunning the mask at the scanning start portion and the scanning end portion on the mask.

Since the illumination light distribution defined by the present invention has a linear slit shape (rectangular shape), its width in the scanning direction can be changed very easily and accurately.
Therefore, if the width of the illumination light is changed in conjunction with the start portion and the end portion of the scanning exposure, overrun of the mask stage is unnecessary or can be made extremely small, and the moving stroke of the mask stage can be minimized.

Further, the width of the light shield formed around the pattern formation area on the mask may be as small as that of the conventional mask, and pinhole defects in the light shield (usually a chrome layer) are inspected during mask manufacture. There is also an advantage that the labor to do is reduced. Particularly, in the present invention, the projection optical system having the circular image field is used, and the rectangular or slit-shaped region extending along the diameter in the circular image field is used. The size in the direction is allowed up to a value close to the diameter of the circular image field, and the size of the exposure field that can be transferred in one scan without overlapping exposure is also disclosed in Japanese Patent Laid-Open No. 2-224923. It can be large compared to the disclosed scheme.

Further, since only the elongated rectangular or slit-shaped area including the diameter within the circular image field is used, the image distortion characteristic which is one of the image forming performance of the projection optical system,
Only the rectangular or slit-shaped region needs to be considered, and there are advantages that the high resolution (high NA) and the large-field projection optical system are relatively easy to manufacture. Therefore, the configuration of the scanning exposure apparatus according to the embodiment of the present invention having the above advantages will be described with reference to the drawings.

FIG. 1 shows the arrangement of a projection exposure apparatus according to the first embodiment of the present invention. In this embodiment, both sides are telecentric and a reduction element of ⅕ is used alone, or a combination of a refraction element and a reflection element is used. A configured projection optical system (hereinafter, simply referred to as a projection lens) PL is used. The exposure illumination light from the mercury lamp 2 is focused on the second focus by the elliptical mirror 4. At the second focus, a rotary shutter 6 that switches between blocking and transmitting illumination light by a motor 8 is arranged. The illumination light flux passing through the shutter 6 is reflected by the mirror 10 and enters the fly-eye lens system 14 via the input lens 12. A large number of secondary light source images are formed on the exit side of the fly-eye lens system 14, and the illumination light from each secondary light source image is reflected by the beam splitter 16
The light enters the lens system (condenser lens) 18 via the.

On the rear focal plane of the lens system 18, the movable blades BL1, BL2, B of the reticle blind mechanism 20 are arranged.
L3 and BL4 are arranged as shown in FIG. The four blades BL1, BL2, BL3, BL4 are drive system 2 respectively.
Moved independently by 2. In this embodiment, as shown in FIG. 2, the width of the opening AP in the X direction (scanning exposure direction) is determined by the edges of the blades BL1 and BL2 extending parallel to the Y axis (diameter) passing through the optical axis AX of the projection lens PL. , The length of the opening AP in the Y direction (stepping direction) is determined by the edges of the blades BL3 and BL4.

The shape of the aperture AP defined by the edges of the four blades BL1 to BL4 is the projection lens PL.
Is defined as a rectangular shape (or slit shape) extending along the diameter in the circular image field IF of. Now, at the position of the blind mechanism 20, the illumination light has a uniform illuminance distribution, and the illumination light that has passed through the aperture AP of the blind mechanism 20 irradiates the reticle R via the lens system 24, the mirror 26, and the main condenser lens 28. To do. At this time, the four blades BL1 to BL of the blind mechanism 20
4 The image of the defined aperture AP is formed on the pattern surface of the lower surface of the reticle R.

The lens system 24 and the condenser lens 2
8 and can give any imaging magnification,
Here, it is assumed that the opening AP of the blind mechanism 20 is enlarged to approximately twice and projected onto the reticle R. Therefore, the scanning speed Vrs of the reticle R during scanning exposure and the blades BL1 and B of the blind mechanism 20 projected on the reticle R
In order to match the moving speed of the edge image of L2, the moving speed Vbl of the blades BL1 and BL2 in the X direction is set to Vrs /
You can set it to 2.

The reticle R that has received the illumination light defined by the opening AP is held by the reticle stage 30 that can move at least uniformly in the X direction on the column 32. Although not shown, the column 32 is integrated with a column for fixing the lens barrel of the projection lens PL. Reticle stage 3
0 performs one-dimensional scanning movement in the X direction by the drive system 34, minute rotational movement for yawing correction, and the like. A movable mirror 36 that reflects the length measurement beam from the laser interferometer 38 is fixed to one end of the reticle stage 30.
The position in the X direction and the yawing amount are measured by the laser interferometer 38 in real time. The laser interferometer 38
A fixed mirror (reference mirror) 40 for is fixed to the upper end of the lens barrel of the projection lens PL.

The image of the pattern on the reticle R arranged on the object plane side of the projection lens PL is projected by the projection lens PL.
It is reduced to / 5 and an image is formed on the wafer W arranged on the image plane side. The wafer W is held together with the fiducial mark plate FM on the wafer holder 44 which can be rotated minutely. The holder 44 is provided on a Z stage 46 that can be finely moved in the optical axis AX (Z) direction of the projection lens PL. And the Z stage 46 is X,
It is provided on an XY stage 48 that moves two-dimensionally in the Y direction, and this XY stage 48 is driven by a drive system 54.
The coordinate position of the XY stage 48 and the yawing amount are measured by the laser interferometer 50, and the laser interferometer 5
The fixed mirror 42 for 0 is fixed to the lower end of the lens barrel of the projection lens PL, and the movable mirror 52 is fixed to one end of the Z stage 46.

Since the projection magnification is set to 1/5 in this embodiment, the moving speed Vws of the XY stage 48 in the X direction during scan exposure is 1/5 of the speed Vrs of the reticle stage 30.
Is. Further, in this embodiment, from a space below the reticle R, an alignment system 60 of a TTR (through the reticle) system that detects an alignment mark (or a reference mark FM) on the wafer W via the reticle R and the projection lens PL. TT for detecting the alignment mark (or the reference mark FM) on the wafer W via the projection lens PL
L (through the lens) type alignment system 62
Is provided, and the relative alignment between the reticle R and the wafer W is performed before the start of the S & S exposure or during the scan exposure.

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

By the way, the rectangular opening A of the blind mechanism 20
By making P as long as possible in the Y direction orthogonal to the scanning direction (X direction), the number of times of scanning in the X direction, that is, the number of times of stepping of 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, it may be better to change the length of the opening AP in the Y direction at each edge of the blades BL3 and BL4. 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.

If 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 Japanese Patent Laid-Open No. 2-229423, the overlap in the shot area is performed. It is necessary to perform exposure to make the exposure amount seamless. The method in this case will be described in detail later. Next, the operation of the apparatus of this embodiment will be described.
Totally managed by 0. The basic operation of the main control unit 100 is the position information from the laser interferometers 38 and 50,
Based on the input of yawing information, the input of speed information from the tacho-generators in the drive systems 34 and 54, and the like, the reticle pattern 30 and the XY stage 48 are kept at a predetermined speed ratio during scan exposure, and the reticle pattern and the wafer are maintained. The purpose is to move the pattern relative to the pattern while keeping it 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 major feature is the interlocking control. When the amount of illumination light during scanning exposure is constant, the reticle stage 3 increases 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, assuming that 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 doubled in speed.

FIG. 3 shows the positional relationship between the reticle R which 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 divided by a light-shielding band corresponding to a street line, and four chips are surrounded by a light-shielding band having a width Dsb wider than the street line at the periphery of a pattern gathering region (shot region).

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. In addition, 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, as a premise, the reticle R and the wafer W shown in FIG.
0, 62, photoelectric sensor 64, etc. are used for relative alignment. 4 is a side view of the reticle R of FIG. 3, and here, the blade BL of the blind mechanism 20 is used.
In order to make the operation of 1 and BL2 easy to understand, the reticle R
Blades BL1 and BL2 are shown immediately above.

First, as shown in FIG. 4A, the reticle R
Is set to 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 that illuminates the reticle R is ideally desired to have a width Dap of zero, but it is difficult to make it completely zero depending on the quality 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, the 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 traveling direction of the reticle R (left side in the drawing). This distance ΔX
s is the maximum opening width D of the opening AP with respect to this reticle R
Set to about half of ap. More specifically, the aperture AP
Since the dimension in the longitudinal direction of the reticle R is naturally determined by the width in the Y direction of the shot area of the reticle R, the maximum value DAmax of the width Dap in the X direction of the opening AP is also determined by the diameter of the image field IF. The maximum value DAmax is calculated in advance by the main control unit 100. Further, assuming that the width (minimum) of the opening AP at the scanning start point in FIG. 4A is DAmin, strictly speaking, the distance ΔXs is determined so as to satisfy the relationship of DAmin + 2 · 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, in the blind mechanism 20, the blade B in the traveling direction of the reticle R is moved.
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 irradiated with the illumination light that has passed through, it is sent in the X direction at a constant speed and reaches the position of FIG. That is, 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. 4E, the image of the edge E1 of the blade BL1 is made to run in the same direction in synchronism with the moving speed of the reticle R from the time of hitting Bl.

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. By the above operation, the exposure of 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 leaked to the wafer W can be made zero, the shutter 6 is left open. You may

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. As described above, according to this embodiment, 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, it is also necessary to determine the prescan (running) range until the state of FIG. In that case, the width Dsb of the light-shielding bands SBr and SBl is increased according to the length of the prescan. 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 calculates the difference in yawing amount,
The reticle stage 30 or the wafer holder 44 may be finely rotated during scan exposure so that the difference becomes zero. However, in that case, the rotation center of the minute rotation must always be the center of the opening AP, and in consideration of the structure of the apparatus, the X-direction guide portion of the reticle stage 30 is slightly rotated around the optical axis AX. The method can be easily realized.

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.
Similarly to, the step-and-scan method using the illumination light from the slit-shaped opening AP is used to expose the wafer. Further, the other chip patterns CP4 and CP5 formed on the same reticle R are used to expose the wafer by the step-and-repeat (S & R) method.

The blind mechanism 2 is used properly in this way.
This can be easily realized by setting the aperture AP by the blades BL1 to BL4 of 0. 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. At the same time, the shape of the opening AP need only be matched with the outer shape of the chip pattern CP4. Then, only the XY stage 48 may be moved in the stepping mode. With the reticle pattern shown in FIG. 5 as described above, S & S exposure and S & R exposure can be selectively performed by the same device and without reticle exchange.

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) are parallel to the Y axis that passes through the center of the circular image field IF as in FIG. Is growing. The edges E3 and E4 defining the longitudinal direction of the opening AP are parallel to each other but are inclined with respect to the X axis, and the opening AP is 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.
6 schematically shows a scanning sequence during 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 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 is present, for the area Ad set in the pattern area CP, the triangular portion formed by the edges E3 and E4 of the opening AP is Y.
The exposure was made uniform by performing scanning exposure while overlapping in the direction. Further, the other area As is exactly aligned with the light-shielding band on the reticle R.

Now, from the state of FIG. 7A, the reticle R and the edge E2 (blade BL2) are made to run in the + X direction (right side in the figure) at substantially the same speed. Eventually, the width of the opening AP in the X direction becomes maximum as shown in FIG.
Stop moving 2 as well. In the state of FIG. 7B, the center of the opening AP and the optical axis AX substantially coincide with each other. 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. In this way, the lower half of the chip pattern area CP is exposed, and the reticle R and the opening AP are stopped in the state as shown in FIG. 7D.

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, the state becomes 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 of directions 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 due to 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. Also in the case of such a chevron type, if the overlapping exposure is performed in the triangular portions at both ends, the homogenization can be similarly performed.

As described above, in each of the embodiments of the present invention, the projection exposure apparatus is premised. However, the mask and the wafer are brought close to each other, and the proxy integrally scans the mask and the wafer with respect to the irradiation energy (X-ray, etc.). The same method can be used for the Mighty Aligner.

[0062]

As described above, according to the present invention, it is possible to reduce the movement stroke of the mask (reticle) in the scanning exposure method and also reduce the size of the light-shielding band on the mask. At the same time, the size of the illumination area in the scanning direction on the mask can be made smaller than that of the conventional hexagon but larger than that of the conventional arc, so that the processing throughput can be increased in combination with the reduction of the moving stroke.

Since the distribution of the illumination light defined by the present invention is a linear slit shape (rectangular shape), the width in the scanning direction can be changed very easily and accurately, so that the width of the illumination light is scanned and exposed. If it is changed in conjunction with the above, overrun of the mask stage is unnecessary or can be made extremely small, and the movement stroke of the mask stage can be minimized.

Particularly, in the present invention, since the projection optical system having the circular image field is used and the rectangular or slit area extending along the diameter in the circular image field is used, the chip pattern area is used. The size in the non-scanning direction is allowed up to a value close to the diameter of the circular image field, and the size of the exposure field that can be transferred by one scan without overlapping exposure is also the same as that of the conventional JP-A-2-224923. It can be made larger than the method disclosed in the publication.

Further, since only the elongated rectangular or slit-shaped region including the diameter within the circular image field is used, the image distortion characteristic which is one of the image forming performances of the projection optical system,
Only the rectangular or slit-shaped region needs to be considered, and there are advantages that the high resolution (high NA) and the large-field projection optical system are relatively easy to manufacture.

[Brief description of 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 a blind mechanism.

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

FIG. 4 is a diagram illustrating a scanning exposure operation according to the embodiment of the present invention.

5 is a plan view showing another pattern arrangement of the reticle mountable on the apparatus of FIG.

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

FIG. 7 is a diagram illustrating 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 diagram illustrating a concept of a conventional step & scan exposure method using arcuate slit illumination light.

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

[Explanation of symbols for main parts]

 R Reticle PL Projection optical system IF Circular image field W Wafer BL1, BL2, BL3, BL4 Blade AP Aperture 20 Blind mechanism 30 Reticle stage 48 XY stage 100 Main control system.

Claims (10)

[Claims] 1. A mask arranged on the object plane side of a projection optical system having a circular visual field and a photosensitive substrate arranged on the image plane side of the projection optical system are one-dimensional relative to the circular visual field. In the method of scanning and exposing the entire circuit pattern formed in a rectangular area on the mask by scanning, the linearly extending in a non-scanning direction intersecting the one-dimensional scanning direction. Irradiating the mask with illumination light having an intensity distribution that is limited to a substantially rectangular shape or a slit shape and is set so as to include the center of a circular visual field on the object plane side of the projection optical system; Alternatively, the mask is moved at a predetermined speed in the one-dimensional scanning direction so that the illumination light having the slit-like intensity distribution relatively scans the rectangular area on the mask from one end side to the other end side, and at the same time, the photosensitive material is exposed. Basis Scanning exposure method which comprises the step of moving said one-dimensional scanning direction at a speed ratio corresponding to the magnification of the projection optical system. 2. The reduction projection optical system which is telecentric on both sides by using only a refractive optical element or a combination of a refractive optical element and a reflective optical element is used as the projection optical system. The method described. 3. Prior to the start of the scanning exposure, the length of the rectangular or slit-shaped intensity distribution of the illumination light in the non-scanning direction is defined as a dimension of the rectangular area on the mask in the non-scanning direction. 3. The method of claim 2 including the step of adjusting according to. 4. The width in the one-dimensional scanning direction of the rectangular or slit-shaped intensity distribution of the illumination light with which the mask is irradiated at each of a start period and an end period of scanning exposure with respect to a rectangular area on the mask. 4. The method according to claim 3, including the step of changing the value in accordance with the movement of the mask. 5. A mask stage for moving a mask held on the object plane side of a projection optical system having a circular visual field in at least a first direction with respect to the circular visual field, and a mask stage projected by the projection optical system. A substrate stage for moving at least a photosensitive substrate exposed with a circuit pattern image in the first direction, and the mask on the photosensitive substrate by synchronously moving the mask stage and the substrate stage in the first direction. Is a device for scanning and exposing the entire image of the circuit pattern, wherein the scanning exposure is limited to a substantially rectangular shape or a slit shape linearly extending in a second direction intersecting the first direction, and the projection is performed. Scanning exposure characterized in that an illumination means is provided for irradiating the mask with illumination light having an intensity distribution set so as to include the center of a circular visual field on the object plane side of the optical system. Location. 6. The projection optical system is a reduction projection optical system configured as a both-side telecentric system by only a refractive optical element or a combination of a refractive optical element and a reflective optical element, and the first stage of the mask stage and the substrate stage. 6. The apparatus according to claim 5, further comprising stage control means for adjusting a speed ratio during synchronous movement in the directions to a reduction magnification of the reduction projection optical system. 7. The light illuminating means includes a light shielding mechanism having a rectangular opening arranged at a position substantially conjugate with the mask for irradiating the illumination light having the rectangular or slit-shaped intensity distribution, and a rectangle of the light shielding mechanism. 7. An apparatus according to claim 6, further comprising a magnifying optical system for magnifying and projecting illumination light passing through the opening onto the mask. 8. The light-shielding mechanism is such that the length of the intensity distribution of the illumination light with which the mask is irradiated in the non-scanning direction is adjusted according to the dimension of the rectangular region on the mask in the non-scanning direction. 8. The apparatus of claim 7, including a movable blade that modifies the size of the rectangular opening. 9. The light-shielding mechanism has a width in the one-dimensional scanning direction of an intensity distribution of illumination light irradiated on the mask at each of a start period and an end period of scanning exposure with respect to a rectangular area on the mask. The apparatus according to claim 7, further comprising a movable blade that changes the shape of the rectangular opening so as to change in association with the movement of the mask. 10. The light-shielding mechanism includes a drive member that drives a movable blade that changes the shape of the rectangular opening in the one-dimensional scanning direction, and the moving speed of the movable blade by the drive member and the stage control means. 10. The apparatus according to claim 9, wherein the ratio of the moving speed of the mask stage to the magnifying power of the magnifying optical system of the proving means is made to correspond.