JP2691319B2 - Projection exposure apparatus and scanning exposure method - Google Patents

Description

The present invention relates to a projection exposure apparatus used in a lithography process during the manufacturing process of semiconductor elements, liquid crystal display elements, etc., and a photoexposure using such an exposure apparatus. The present invention relates to a scanning exposure method for a substrate.

[Conventional technology]

Conventionally, there are roughly two types of projection exposure apparatuses of this type, one is a method of exposing a wafer, a plate, or the like through a projection optical system having an exposure field capable of including the entire pattern of a mask (reticle). There is a step-and-repeat method of exposing the substrate, and the other is to expose the mask and the photosensitive substrate so as to face each other with the projection optical system in between and to perform relative scanning under the mask illumination of arc-shaped slit illumination light. This is a scanning method.

The former step-and-repeat exposure method is a mainstream device in recent lithography processes, and has higher resolution, overlay accuracy, and throughput than aligner using the latter scan-exposure method. It is becoming increasingly common, and steppers are expected to remain the mainstream for some time to come.

By the way, recently, a new method that achieves high resolution even in the scan exposure method is SPIE Vo1.1088 Optical / Lase.
r Microlithography II (1989), pages 424-433, proposed as a step-and-scan method. The step-and-scan method is a method in which a mask (reticle) is one-dimensionally scanned while a wafer is one-dimensionally scanned at a speed synchronized with the mask, and a method in which the wafer is step-moved in a direction orthogonal to the scanning exposure direction. Are mixed.

FIG. 9 is a diagram for explaining the concept of the step & scan method, but here, an array of shot areas (one chip or multi-chips) in the X direction on the wafer W is scanned and exposed by the arc-shaped slit illumination light RIL. , W in the Y direction
To step. In the figure, the arrow shown by the broken line represents the exposure sequence of step & scan (hereinafter referred to as S & S), and S & S exposure is performed in the order of shot areas SA ₁ , SA ₂ , ... SA ₆ , and then the wafer W is exposed. The same S & S exposure is performed in the order of shot areas SA ₇ , SA ₈ , ... SA ₁₂ arranged in the center in the Y direction. In the S & S aligner disclosed in the above-mentioned document, the image of the reticle pattern illuminated by the arcuate slit illumination light RIL is imaged on the wafer W via the 1/4 × reduction projection optical system. 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. Also, the circular slit illumination light RIL
Uses a reduction system that combines a refraction element and a reflection element as a projection optical system, and it is said that various aberrations become almost zero in a narrow range (annular zone) of the image height point that is apart from the optical axis by a certain distance. This is to get an advantage. An example of such a catoptric reduction projection system is disclosed, for example, in USP 4,747,678.

In addition to the S & S exposure method using the arcuate slit illumination light, an attempt to apply a normal projection optical system having a circular image field (full field type) to the S & S exposure method is disclosed in, for example, Japanese Patent Laid-Open No. 2-229423. It was proposed in the publication. According to this public law, the shape of the exposure light that illuminates the reticle (mask) is a regular hexagon inscribed in the circular field of the projection lens system, and the edges of the two sides of the regular hexagon that face 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 reticle (mask) in the scan exposure direction is used.
It has been shown that the scanning speed of the reticle stage and the wafer stage can be remarkably increased as compared with the S & S exposure method using the arc-shaped slit illumination light by taking the illumination area as large as possible.

[Problems to be solved by the invention]

According to the conventional technique disclosed in Japanese Unexamined Patent Publication No. 2-229423, the mask illumination area in the scanning exposure direction is made as wide as possible, which is advantageous on the loop.

However, in consideration of the actual scanning sequence of the mask stage and the wafer stage, even the apparatus disclosed in the above publication has to use the zigzag S & S method as shown in FIG.

This is because when the diameter of the wafer W is set to 150 mm (6 inches) and it is attempted to complete the exposure of a row of shot regions corresponding to the wafer diameter by only one continuous X-direction scan,
Assuming that a projection lens system with a magnification of 1/5 is used, the length of the reticle in the scanning direction (X direction) reaches 750 mm (30 inches), which makes it extremely difficult to manufacture such a reticle. Is. Even if such a reticle can be manufactured, the reticle stage that scans the reticle in the X direction requires a stroke of 750 mm or more. Therefore, it is essential to make the apparatus extremely large. For this reason, even with the device disclosed in the above publication, there is no choice but to perform zigzag scanning.

Therefore, in the shot areas adjacent to each other in the scanning exposure direction, for example, the shot areas SA ₁ and SA _{12 in} FIG. 9, the light shield is provided around the pattern area on the reticle so that the reticle pattern is not transferred into the adjacent shot areas. I had to cover it widely.

FIG. 10 shows the arrangement of the hexagonal illumination area HIL, the circular image field IF of the projection lens system, and the reticle R during scanning exposure, and FIG. 10 (A) shows the hexagonal illumination area HIL scanning on the reticle R. Represents the state set at the start position,
From this state, only the reticle R one-dimensionally moves to the right in the figure. Then, at the end of one scan, it becomes as shown in FIG.

In FIG. 10, CP ₁ , CP ₂ , ... CP ₆ are chip patterns formed on the reticle R side by side in the X direction. The arrangement of these six chip patterns is one scan in the X direction. Corresponds to the shot area to be exposed. In the figure, the center point of the hexagonal subtotal area HIL is the center of the image field IF, that is, the optical axis AX of the projection lens system.
And almost match.

As is clear from FIG. 10, at the scanning start portion and the scanning end portion on the reticle R, a light shield at least the width dimension of the hexagonal illumination area HIL in the scanning direction is required outside the pattern area. . At the same time, the size of the reticle R itself in the scanning direction becomes large, and the movement stroke of the reticle stage in the X direction also changes from CP _{1 to} C of the chip pattern.
There may be a problem in realizing the device, such as the total size of P _{6 in} the X direction and the size of the hexagonal illumination area HIL in the scanning direction is required.

In view of the above problems, the present invention does not provide a particularly wide light shield around the pattern exposure area on the reticle (mask), and minimizes the movement stroke of the reticle (mask) stage during scanning exposure. It is also an object of the present invention to provide a scan type (or S & S type) projection exposure apparatus and a scanning exposure method with improved throughput.

[Means for solving the problem]

Therefore, the present invention provides, in a scanning exposure type projection exposure apparatus, illumination means for irradiating illumination light for exposure to a transfer area of a mask through an opening of a variable field stop disposed at a position substantially conjugate with the mask, The variable field stop aperture shape is made rectangular (having an edge orthogonal to the scanning exposure direction), and the width of the rectangular stop aperture is changed in the direction of the width dimension of the transfer area (pattern formation area) on the mask (scanning direction). Drive means is provided.

Then, the driving means is arranged to change the width of the rectangular aperture of the variable field diaphragm in conjunction with the position change of the rectangular aperture image of the variable field diaphragm on the transfer area of the mask which changes by one-dimensional scanning of the mask stage. A control means for controlling is provided.

Furthermore, the present invention irradiates a part of the circuit pattern (chip pattern CPn) formed in the rectangular area on the mask (reticle R) with illumination light limited to a two-dimensional shape, and a part of the circuit pattern of the mask. Image of the projection optical system (projection lens P
While projecting and exposing on the photosensitive substrate (wafer W) via L), the mask (R) and the photosensitive substrate (W) are projected onto the projection optical system (P).
It is applied to a scanning exposure method for forming an entire image of a circuit pattern on a photosensitive substrate (W) by performing relative scanning in a predetermined first direction (X direction) with respect to a projection visual field (image field IF) of L). It And in the exposure method,
The size in the first direction (X direction) of the two-dimensional shape of the projected image of a part of the circuit pattern exposed on the photosensitive substrate (W) (defined by the width D _ap of the illumination opening AP) is the mask (R).
And the photosensitive substrate (W) are moved relative to each other in each of the start period and the end period of the scanning exposure by the relative movement, and are substantially constant between the start period and the end period (the maximum value of the width _Dap ). Therefore, the step of adjusting the magnitude of the illumination light in the first direction according to the passage of time of scanning exposure is performed.

[Action]

In the conventional scanning exposure method, a fixed shape aperture (hexagon,
The mask was irradiated with the illumination light via an arc, etc.,
In the present invention, since the width of the aperture (variable field stop) in the scanning direction is changed in association with the mask scanning or the photosensitive substrate scanning, the mask is largely overrun at the scanning start portion and the scanning end portion on the mask. Even if it is not necessary, the same S & S exposure method can be realized by simply narrowing the opening width. Therefore, overrun of the mask stage is unnecessary or extremely small, and the movement stroke of the mask stage can be minimized.
The width of the light shield formed around the pattern formation area on the mask can be as small as that of the conventional mask, reducing the time and effort required to inspect pinhole defects in the light shield (usually a chrome layer) during mask manufacturing. There is an advantage that is done.

Furthermore, by setting the opening of the variable field stop to have a shape that matches the pattern formation region on the mask, it can be used as a stepper equivalent to the conventional one.

In addition, the aperture position and geometrical shape of the variable field stop can be changed to one-dimensional, two-dimensional, or rotational direction within the image field of the projection optical system, so that mask patterns of various chip sizes can be instantly displayed. Can correspond to.

〔Example〕

FIG. 1 shows the structure of a projection exposure apparatus according to the first embodiment of the present invention.
5 A projection optical system (hereinafter simply referred to as a projection lens for simplicity) PL configured by only a reduction refraction element or a combination of a refraction element and a reflection element is used.

The illumination light for exposure from the mercury lamp 2 is condensed at the second focal point 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 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 illumination light from each secondary light source image enters a lens system (condenser lens) 18 via a beam splitter 16. Movable blades BL ₁ , BL ₂ , BL ₃ , BL ₄ of the reticle blind mechanism 20 are arranged on the rear focal plane of the lens system 18 as shown in FIG. The four blades BL ₁ , BL ₂ , BL ₃ and BL ₄ are drive system 22 respectively.
Moved independently by. In this embodiment, blade B
The width of the opening AP in the X direction (scanning exposure direction) is determined by the edges of L ₁ and BL ₂ , and the length of the opening AP in the Y direction (stepping direction) is determined by the edges of the blades BL ₃ and BL _4. And

Further, the shape of the aperture AP defined by the edges of the _four blades BL _{1 to} BL ₄ is defined so as to be included in the circular image field IF of the projection lens PL. Now, at the position of the blind mechanism 20, the illumination light has a uniform illuminance distribution,
The illumination light that has passed through the opening AP of the blind mechanism 20 illuminates the reticle R via the lens system 24, the mirror 26, and the main condenser lens 28. At this time, the blind mechanism
An image of the aperture AP defined by the _four blades BL _{1 to} BL ₄ of 20 is formed on the pattern surface of the lower surface of the reticle R. Although an arbitrary imaging magnification can be given by the lens system 24 and the condenser lens 28, it is assumed here that the aperture AP of the blind mechanism 20 is enlarged to about 2 times and projected onto the reticle R. Therefore, in order to match the scanning speed V _rs of the reticle R during scan exposure with the moving speeds of the edge images of the blades BL ₁ , BL ₂ of the blind mechanism 20 projected on the reticle R, the blades BL ₁ , BL ₂ V speed Vbl in the X direction
Set it to _rs / 2.

Now, the reticle R that received the illumination light specified by the aperture AP
Are held by a reticle stage 30 that can move at least at a constant speed on the column 32 in the X direction. Although not shown, the column 32 is integrated with a column for fixing the lens barrel of the projection lens PL. The reticle stage 30 is driven by the drive system 34
One-dimensional scanning movement in the direction, minute rotational movement for yawing correction, etc. are performed. A movable mirror 36 that reflects the measurement beam from the laser interferometer 38 is fixed to one end of the reticle stage 30, and the position and yawing amount of the reticle R in the Y direction are measured by the laser interferometer 38 in real time.
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 the projection lens PL.
It is reduced to 1/5 and is imaged on the wafer W. The wafer W is attached to the wafer holder 44 that can be rotated minutely and has a reference mark plate.
Holds with FM. The holder 44 is the optical axis of the projection lens PL
It is provided on a Z stage 46 that can be finely moved in the AX (Z) direction. Then, the Z stage 46 moves two-dimensionally in the X and Y directions.
It is provided on the XY stage 48, and this XY stage 48 is a drive system.
Driven by 54. The coordinate position and yawing amount of the XY stage 48 are measured by the laser interferometer 50, 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 movable mirror 52 is the Z stage. It is fixed to one end of 46.

Since the projection magnification is set to 1/5 in this embodiment, the moving speed V _ws of the XY stage 48 in the X direction during scan exposure is 1/5 of the speed V _rs of the reticle stage 30. Further, in this embodiment, 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 60
And a TTL (through-the-lens) type alignment system 62 for detecting the alignment mark (or reference mark FM) on the wafer W from the space below the reticle R via the projection lens PL, before the start of S & S exposure, Alternatively, the relative alignment between the reticle R and the wafer W is performed during scan exposure.

The photoelectric sensor 64 shown in FIG. 1 is a reference mark.
When the FM type is used, the light from the emission mark is received via the projection lens PL, reticle R, condenser lens 28, lens systems 24 and 18, and beam splitter 16, and the coordinate system of the XY stage 48. When specifying the position of the reticle R in the
It is used to define the position of the detection center of.

By the way, the opening AP of the blind mechanism 20 is arranged in the scanning direction (X
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 by increasing the length in the Y direction orthogonal to the (direction). 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 BL ₃ and BL ₄ . For example, the opposing edges of the blades BL ₃ and BL ₄ may be adjusted so as to match the street lines that define 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.

Also, the size of one shot area in the Y direction is the Y of the opening AP.
If the size exceeds the maximum dimension in the direction, the above-mentioned JP-A-2-2294
As seen in Japanese Patent Publication No. 23, it is necessary to perform overlap exposure inside the shot area 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. The sequence and control of the operation are comprehensively managed by the main control unit 100. The basic operation of the main control unit 100 is the laser interferometer 38, 5
Input of position information and yawing information from 0, drive system 34, 5
Based on the input of speed information from the tachogenerator, etc. in 4, while maintaining a predetermined speed ratio between the reticle stage 30 and the XY stage 48 during scanning exposure, the relative positional relationship between the reticle pattern and the wafer pattern is predetermined. It is to make relative movement while holding it within the alignment error of.

Then, the main control unit 100 of the present embodiment, in addition to its operation, moves the edge positions of the blades BL ₁ and BL ₂ in the scanning direction of the blind mechanism 20 in the X direction in synchronization with the scanning of the reticle stage 30, A major feature is that the drive system 22 is interlocked.

When the amount of illumination light during scanning exposure is constant, the absolute speed of reticle stage 30 and XY stage 48 must be increased as the maximum opening width of aperture AP in the scanning direction increases. In principle, when the same exposure amount (dose amount) is given to the resist on the wafer W, the width of the opening AP is set to 2
If doubled, the XY stage 48 and reticle stage 30 must also be doubled in speed.

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 C are provided on the reticle R.
It is assumed that P ₁ , CP ₂ , CP ₃ and CP ₄ are lined up 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 D _sb wider than the street line around the 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 RM ₁ and RM ₂ are formed outside them.

The opening AP of the blind mechanism 20 has a scanning direction (X-direction) edges E ₁ of the blade BL ₁ extending parallel to the Y direction perpendicular to the blade BL ₂ edge E _2, the edge
The width of E ₁ and E _{2 in} the scanning direction is D _ap . Furthermore, Y of opening AP
The length in the direction substantially coincides with the width in the Y direction of the shot area on the reticle R, and the blade BL is arranged so that the edge defining the longitudinal direction of the opening AP coincides with the center of the light shielding band extending in the peripheral X direction. ₃ , BL ₄ are set.

Next, with reference to FIG. 4, the manner of S & S exposure in this embodiment will be described. Here, as a premise, it is assumed that the reticle R and the wafer W shown in FIG. 3 are relatively aligned using the alignment systems 60 and 62, the photoelectric sensor 64, and the like.
FIG. 4 is a side view of the reticle R shown in FIG.
Here, in order to make it easier to understand the operation of the blades BL ₁ and BL ₂ of the blind mechanism 20, the blade BL is placed directly above the reticle R.
₁ and BL ₂ are illustrated.

First, as shown in FIG. 4A, the reticle R is set at 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 ideally has a width D _ap of zero, but the blade B
It is difficult to completely set it to zero depending on the quality of the edges E ₁ and E ₂ of L ₁ and BL ₂ . Therefore, in this embodiment, the width D _ap of the image of the aperture AP on the reticle is set to _be smaller than the width D _sb of the light-shielding band SBr on the right side of the reticle R. Usually, light-shielding band SBr
The width D _sb is about 4 to 6 mm, and the width D _ap of the image of the aperture AP on the reticle is about 1 mm.

Then, as shown in FIG. 4 (A), the center of the aperture AP in the X direction is shifted by ΔX _{s with} respect to the optical axis AX in the direction opposite to the scanning traveling direction of the reticle R (left side in the figure). deep. The distance ΔX _s is set to about half the maximum opening width D _ap of the opening AP with respect to the reticle R. More specifically, the opening A
Since the dimension of P in the longitudinal direction is naturally determined by the width of the shot area of the reticle R in the Y direction, the width of the opening AP in the X direction.
The maximum value DA _{max of} D _ap is also determined by the diameter of the image field IF. The maximum value DA _max is calculated in advance by the main control unit 100. Moreover the Figure 4 (A) an opening AP of the width of the scanning start point of the (minimum) and DA _min, strictly speaking, D
Distance ΔX _s to satisfy the relationship of A _min + 2 · ΔX _s = DA _max
Is determined.

Next, the reticle stage 30 and the XY stage 48 are moved in opposite directions at a speed ratio proportional to the projection magnification. At this time, as shown in FIG. 4 (B), of the blind mechanism 20, only the blade BL _{2 in} the traveling direction of the reticle R moves in synchronization with the movement of the reticle R, and the image of the edge E ₂ of the blade BL ₂ appears. Is on the shading band SBr.

The progress in scanning the reticle R, When the edge E ₂ of the blade BL ₂ reaches the position that defines the maximum aperture AP opening width as FIG. 4 (C), to stop the subsequent movement of the blade BL _2. Therefore, in the drive system 22 of the blind mechanism 20, an encoder that monitors the moving amount and moving speed of each blade, a tacho-generator, etc. are provided, and position information and speed information from these are sent to the main control unit 100, Used to synchronize with the scanning movement of reticle stage 30.

Thus, the reticle R is sent in the X direction at a constant speed while being illuminated with the illumination light that has passed through the aperture AP having the maximum width, and reaches the position shown in FIG. 4 (D). That is, as shown in FIG. 4 (E), from the time when the image of the edge E ₁ of the blade BL _{1 in} the direction opposite to the traveling direction of the reticle R hits the shading band SBl on the left side of the shot area of the reticle R, The image of the edge E ₁ of the blade BL ₁ is run in the same direction in synchronization with the moving speed of the reticle R.

Then, at the time when the left shading strip SBL is shielded by the edge image of the right blade BL ₂ (at this time, the left blade BL ₁ also moves, and the width D _{ap of the} opening AP is the minimum value DA _min
Reticle stage 30 and blade BL ₁
Stop moving.

With the above operation, exposure by one scan of the reticle (exposure for one shot) is completed, and the shutter 6 is closed. However, if the width D _ap of the opening AP is sufficiently narrower than the width D _sb 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
May be left open.

Next, the XY stage 48 is stepped in the Y direction by 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 direction as before, and the same scan exposure is performed on different shot areas on the wafer W. To do.

As described above, according to this embodiment, the stroke of the reticle stage 30 in the scanning direction can be minimized, and the light-shielding band SB that defines both sides of the shot area in the scanning direction can be used.
There is an advantage that the width D _sb of l and SBr can be small.

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.

For this reason, it is also necessary to determine the prescan (running) range until the state shown in FIG. In that case, depending on the length of the prescan, the width of the light-shielding bands SBr and SBL
It will expand D _sb . This is also applicable when overscanning is required in response to the fact that the uniform velocity motion of the reticle stage 30 (XY stage 48) cannot be suddenly stopped at the end of one scan exposure. .

However, even when performing prescan and overscan, the reticle stage 30 is operated when the shutter 6 is set to a high speed and the open response time (the time required from the fully closed state of the shutter to the full open) and the closing response time are sufficiently short. At the time of completing the pre-scan (acceleration) and entering the main scan (position in FIG. 4 (A)), or when moving from the main scan to the overrun (deceleration), the shutter 6 is interlocked to open and close. Good.

For example, the uniform scan speed of the reticle stage 30 during the main scan is V _rs , (mm / sec), and the widths of the light-shielding bands SBl and SBr are D _sb (m
m) and the minimum width of the aperture AP on the reticle R is DA _min (mm), the response time t _s of the shutter 6 should satisfy the following relationship under the condition of D _sb > DA _min. Good.

(D _sb −DA _min ) / V _rs > t _{s 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. Therefore, the main controller 100 calculates the difference between the two yawing amounts, and the reticle stage 30 or the wafer holder is adjusted so that the difference becomes zero.
It suffices to slightly rotate 44 during scanning exposure. However, in that case, it is necessary to always make the center of rotation of the minute rotation the center of the opening AP. Considering the structure of the apparatus, the guide portion of the reticle stage 30 in the X direction is slightly rotated about 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 , CP ₂ and CP ₃ are used to expose a wafer by a step-and-scan method using illumination light from the slit-shaped aperture AP similarly to the reticle R shown in FIG. Another chip pattern formed on the same reticle R
CP ₄ and CP ₅ are used to expose a wafer by a step-and-repeat (S & R) method. Such proper use can easily be achieved by setting the aperture AP by the blade BL ₁ to BL ₄ of the blind mechanism 20, for example, when exposing a chip pattern CP ₄ is the chip pattern CP ₄ by moving the reticle stage 30 It suffices to set the pattern center so as to coincide with the optical axis AX and match the shape of the opening AP with the outer shape of the chip pattern CP ₄ . 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, S & S exposure and S & R exposure can be selectively performed by the same device and without reticle exchange.

FIG. 6 shows the blade BL of 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 _{1 to} BL ₄ is shown, and the edges E ₁ and E ₂ that define the width of the opening AP in the scanning direction (X direction) extend in parallel to the Y direction as in FIG. 2 above. , The edge that defines the longitudinal direction of the opening AP
Although E ₃ and E ₄ are parallel to each other, they are inclined with respect to the X axis, and the opening AP becomes a parallelogram. In this case, four blades BL ₁ to BL ₄ is moved in conjunction with the reticle movement at the time of scanning exposure in X, Y directions. However, although the moving speed V _{bx in} the X direction of the images of the edges E ₁ and E ₂ of the blades BL ₁ and BL _{2 in} the scan exposure direction is almost the same as the scanning speed V _{rs of the} reticle, the blades BL ₃ and BL ₄ when a need to move the can, the moving velocity V _By the edge E _3, E ₄ in the Y direction, the edge E _3, E ₄
Let θe be the inclination angle of X with respect to the X-axis, then V _by = V _bx · tan
It is necessary to synchronize with the relationship of θe.

FIG. 7 schematically shows a scanning sequence during S & S exposure with the aperture shape shown in FIG. Seventh
In the figure, the aperture AP is considered as being projected on the reticle R, and is displayed by each edge E _{1 to} E ₄ . In the second embodiment shown in FIGS. 6 and 7, the reticle R to be projected on the wafer W is used.
It is assumed that the upper chip pattern region CP 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 BL _{1 to} BL ₂ in FIG. 6 are adjusted to set the state as shown in FIG. 7 (A) at the start of scanning.

That is, the aperture AP with the narrowest width is located on the light-shielding band SBr on the right side of the reticle R, and
An edge E ₁ on the left side of the opening AP is set at a position farthest from the optical axis AX (an edge position when the opening AP is widest 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 generated by the upper and lower edges E ₃ and E ₄ of the opening AP being inclined with respect to the X axis, and the widths of the areas Ad and As in the Y direction are equal to the edge E ₃ ,
DA _max · tan θe is uniquely determined by the inclination angle θe of E ₄ and the maximum opening width DA _max of the edges E ₁ and E ₂ . 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 E ₃ and E ₄ of the opening AP in the Y direction. By doing so, the exposure amount was made uniform. Further, the other area As is exactly aligned with the light-shielding band on the reticle R.

Now, from the state of FIG. 7 (A), the reticle R and the edge E ₂
Run (blade BL ₂ ) in the + X direction (right side in the figure) at approximately the same speed. Eventually, the width of the opening AP in the X direction becomes the maximum as shown in FIG. 7 (B), and the movement of the edge E ₂ is also stopped. In the state of FIG. 7 (B), the center of the opening AP and the optical axis AX substantially coincide with each other.

After that, only the reticle R moves in the + X direction at a constant speed, and as shown in FIG. 7 (C), the edge E ₁ on the left side of the opening AP enters the light shielding band SBl on the left side from the edge E ₁ (blade BL ₁ ) Move to the right (+ X direction) at almost the same speed as reticle R. Thus, 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 relative positional relationship in the Y direction is set so that the overlap area Ad is exposed by weight in the triangular portion defined by the edge E ₄ . At this time, if it is necessary to change the length of the opening AP in the Y direction, the edge E ₃ (blade B
L ₃ ) or edge E ₄ (blade BL ₄ ) is moved and adjusted in the Y direction.

Next, the reticle R is scanned and moved in the -X direction, and the edge E ₁ (blade BL ₁ ) is moved in conjunction with the -X direction. Then, as shown in FIG. 7 (F), when the opening width due to the edges E ₁ and E ₂ becomes maximum, the movement of the edge E ₁ 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, since the overlapping area Ad is set and both end portions (triangular portions) where the exposure amount is insufficient due to the shape of the opening AP are superimposed and exposed by two scanning exposures, the exposure amount in the area Ad is also uniformed.

FIG. 8 shows another blade shape of the blind mechanism 20, which defines the edges E _{1 of} the blades BL ₁ and BL _{2 which} are defined in the scanning direction.
E ₂ is a straight line parallel to each other, and the edges of the blades BL ₃ and BL _{4 in} the direction orthogonal to the scanning direction are triangles symmetrical with respect to the Y axis passing through the optical axis AX. And here the blade
The edges of BL ₃ and BL ₄ 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.

As described above, the projection exposure apparatus is assumed in each of the embodiments of the present invention. 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 the irradiation energy (X-ray, etc.). The same method can also be used for.

〔The invention's effect〕

As described above, according to the present invention, the movement stroke of the mask (reticle) in the scanning exposure method can be minimized, and the size of the light-shielding band on the mask can be reduced.

At the same time, since a large illumination area in the scanning direction on the mask can be obtained, the processing throughput can be remarkably increased in combination with the reduction of the movement stroke.

Further, according to the present invention, since the movement stroke of the mask stage provided relatively above in the exposure apparatus can be minimized (at least the size of the pattern area of the mask is required), the change of the center of gravity of the entire exposure apparatus can be prevented from the conventional case. It is possible to keep it smaller than that. Therefore, it is possible to reduce the shaking of the exposure device that occurs during execution of the step-and-scan exposure operation, and it is also possible to suppress deterioration of the image quality of the circuit pattern projected and exposed on the photosensitive substrate and obtain high resolution. Become.

[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 a blind mechanism, and FIG. 3 is a reticle pattern arrangement suitable for the apparatus of FIG. 4 is a plan view showing the scanning exposure operation in the embodiment of the present invention, FIG. 5 is a plan view showing another pattern arrangement of the reticle mountable on the apparatus of FIG. 1, and FIG. FIG. 7 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, and FIG. 8 is a plan view showing another blade shape. FIG. 9 is a diagram for explaining the concept of a conventional step & scan exposure method using arcuate slit illumination light, and FIGS. 10 (A) and (B) are conventional scan exposure methods using regular hexagonal illumination light. It is a figure explaining. [Explanation of symbols of main parts] R ... Reticle, PL ... Projection optical system, W ... Wafer, BL
₁ , BL ₂ , BL ₃ , BL ₄ …… Blade, AP …… Aperture, E ₁ , E ₂ ,
E ₃ , E ₄ ...... Opening edge, 20 ...... Blind mechanism, 22 ......
Blind drive system, 30 ... reticle stage, 34 ... drive system, 48 ... XY stage, 54 ... drive system, 100 ... main control system.

Claims (16)

(57) [Claims] 1. A projection optical system for projecting a pattern formed in a transfer area on a mask onto an exposed area on a photosensitive substrate,
A mask stage that moves the mask one-dimensionally over a range equal to or larger than the width dimension in one direction of the transfer area of the mask while holding the mask substantially perpendicular to the optical axis of the projection optical system, and the photosensitive substrate. A substrate stage that moves one-dimensionally along a one-dimensional movement direction of the stage at a speed synchronized with the moving speed of the mask stage, and projection exposure for exposing the pattern of the mask onto the photosensitive substrate by scanning exposure In the apparatus, an illumination means for irradiating the transfer area of the mask with illumination light for exposure through an opening of the variable field diaphragm arranged at a position substantially conjugate with the mask; Driving means for forming a rectangle having an edge substantially orthogonal to the scanning exposure direction and varying the width of the rectangle in the scanning exposure direction; one-dimensional of the mask stage And a control means for controlling the driving means so as to change the rectangular aperture width of the variable field stop in association with a change in the relative position of the transfer area of the mask and the variable field stop that changes due to movement. And a projection exposure apparatus. 2. The width of the rectangular aperture of the variable field stop in the one-dimensional movement direction in synchronization with the peripheral portion of the transfer area of the mask facing the vicinity of the optical axis of the projection optical system. 2. The device according to claim 1, wherein the drive means is controlled so as to decrease the power consumption sequentially. 3. The shape of the opening of the variable field stop is two-dimensionally variable from a maximum open state that includes almost the entire transfer area of the mask to a fully closed state that substantially shields the illumination light to the mask. 2. The substrate is exposed statically by prohibiting relative scanning between the mask stage and the substrate stage when the aperture of the variable field stop is set to the maximum open state. The described device. 4. A mask stage capable of linearly moving in at least a first direction while holding a mask having a circuit pattern formed within a predetermined rectangular area, and a predetermined two-dimensional shape smaller than the area of the rectangular area of the mask. Illuminating means for irradiating the mask with illumination light limited to the above, a projection optical system for projecting an image of a part of the circuit pattern of the mask illuminated with the illumination light, and exposure by the projected image And a substrate stage capable of moving linearly along at least the first direction and holding the photosensitive substrate to be moved linearly along the first direction, and by synchronously moving the mask stage and the substrate stage in the first direction, the circuit pattern of the mask is A projection exposure apparatus for scanning and exposing on a photosensitive substrate, wherein during the scanning exposure, illumination light from the illumination means is on one end side in the first direction of a rectangular range of the mask. Illumination shape changing means for changing the size of the two-dimensional shape of the illumination light in the first direction in association with the movement of the mask stage during the irradiation of each of the other ends is provided. Projection exposure apparatus. 5. The illuminating means is arranged substantially coincident with an imaging optical system that forms a surface conjugate with the mask between a light source that supplies the illumination light and the mask. And an illumination field varying mechanism having an opening for defining a two-dimensional shape of illumination light on the mask, wherein the illumination field varying mechanism is also used as the illumination shape varying means. The apparatus according to item 4. 6. The illumination shape changing means includes a driving mechanism for changing the dimension of the opening of the illumination visual field changing mechanism in the first direction at a speed synchronized with the movement of the mask stage. Item 5. The device according to item 5. 7. The image forming optical system of the illuminating means has a predetermined magnifying power for magnifying and projecting an image of the opening of the illumination visual field varying mechanism onto the mask, and the illumination visual field by the driving mechanism. 7. The apparatus according to claim 6, wherein the ratio of the speed of dimensional change of the opening of the variable mechanism to the moving speed of the mask stage is set to the value of the magnification of the imaging optical system. 8. The projection optical system is a reduction projection optical system having a circular projection field that is telecentric on both sides of the mask side and the photosensitive substrate side, and the two-dimensional shape of illumination light on the mask is the above-mentioned. The shape of the opening of the illumination field changing mechanism is formed in a rectangular shape or a slit shape so as to be set in a rectangular shape or a slit shape linearly extending in the direction orthogonal to the first direction in the center of the circular projection visual field. The device according to any one of claims 5, 6, and 7, characterized in that. 9. A mask stage capable of linearly moving in at least a first direction while holding a mask having a circuit pattern formed within a predetermined rectangular range, and a predetermined two-dimensional shape smaller than the area of the rectangular range of the mask. Illuminating means for irradiating the mask with illumination light limited to the above, a projection optical system for projecting an image of a part of the circuit pattern of the mask illuminated with the illumination light, and exposure by the projected image And a substrate stage capable of moving linearly along at least the first direction and holding the photosensitive substrate to be moved linearly along the first direction, and by synchronously moving the mask stage and the substrate stage in the first direction, the circuit pattern of the mask is A projection exposure apparatus for scanning and exposing on a photosensitive substrate, wherein during the scanning exposure, illumination light from the illumination means is on one end side in the first direction of a rectangular range of the mask. Illumination shape changing means for changing the size of the two-dimensional shape of the illumination light in the first direction between the period of irradiating each of the other ends and the period of illumination of the illumination light inside the rectangular range of the mask. A projection exposure apparatus, which is provided. 10. A part of a circuit pattern formed within a rectangular area on a mask is illuminated with illumination light limited to a two-dimensional shape, and a part of the image of the circuit pattern is exposed through a projection optical system. The entire image of the circuit pattern is formed on the photosensitive substrate by relatively scanning the mask and the photosensitive substrate in a predetermined first direction with respect to the projection field of the projection optical system while projecting and exposing the substrate. A scanning exposure method, wherein the size of a projected image of a part of the circuit pattern exposed on the photosensitive substrate in the first direction is a period for starting scanning exposure by relative movement of the mask and the photosensitive substrate. The magnitude of the illumination light in the first direction is changed with the passage of time during the scanning exposure so that it changes in association with the relative movement in each of the end periods and becomes substantially constant between the start period and the end period. Adjust according to A scanning exposure method comprising the steps of: 11. A size in a first direction of a projected image of a part of a circuit pattern exposed on the photosensitive substrate in a period between a start period and an end period of the scanning exposure,
When set to a constant width DA smaller than the dimension of the image in the first direction when the entire rectangular range of the mask is projected,
The width of the illumination light in the first direction such that the size of the projected image of a part of the circuit pattern in each of the start period and the end period in the first direction is interlocked and changed within a range smaller than the constant width DA. 11. The method according to claim 10, characterized in that V is variable. 12. The method of claim 11, wherein the projection optics is a double-sided telecentric reduction projection lens having a circular projection field. 13. The projection optical system according to claim 11, wherein the projection optical system is a combination of a refractive optical element and a reflective optical element, or a double-sided telecentric reduction projection optical system composed of only the refractive optical element. The method described in. 14. The step of adjusting the magnitude of the illumination light in the first direction according to the elapsed time of the scanning exposure includes:
7. The method according to claim 1, further comprising: an adjustment for continuously increasing a width of the illumination light in the first direction and an adjustment for continuously reducing the width according to a moving position of the mask during scanning exposure. The method described in paragraph 10. 15. The intensity distribution of the illumination light on a mask is
15. The rectangular shape or the slit shape, which linearly extends in a second direction orthogonal to the first direction and whose width in the first direction is variable, is defined as in claim 12 or 14. The method according to any one of claims. 16. During the scanning exposure between the start period and the end period, the intensity distribution of the illumination light is limited to a rectangular shape or a slit shape including the center in the circular projection field of the projection optical system. 16. The method according to claim 15, characterized in that