JP2000012452A - Exposure equipment - Google Patents

Abstract

(57) [Summary] (with correction) [PROBLEMS] To provide an exposure apparatus provided with a reference mark excellent in stationary stability. SOLUTION: A projection optical system PL for projecting a predetermined pattern on a photosensitive substrate 202, and an X-axis orthogonal to the optical axis AX (Z) direction of the projection optical system with the substrate mounted on the upper surface and orthogonal to the optical axis.
A substrate stage 201 movable in the Y two-dimensional direction, alignment optical systems 131 to 134 for alignment of the photosensitive substrate in the XY directions, and reference marks 141 and 142 for calibration of the optical systems in the XY directions; the reference mark is fixed at a predetermined position in the substrate stage predetermined distance t ₂ from the substrate stage top, moving range T of the optical axis AX direction of the substrate stage, the photosensitive substrate thickness t ₁ and predetermined The exposure apparatus is configured so as to be equal to or more than the sum of the distance t ₂ . When the substrate is placed on the substrate stage, the reference mark does not contact the substrate, and the reference mark can be focused by moving the substrate stage in the optical axis AX direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus used for manufacturing a semiconductor device, a liquid crystal panel, and the like, and more particularly to an exposure apparatus suitable for handling a large substrate.

[0002]

2. Description of the Related Art In a conventional exposure apparatus used for manufacturing a semiconductor device, a liquid crystal panel, or the like, a reference mark is used to calibrate a position of an alignment system for measuring a position of a substrate and a position of an original. The reference mark is usually provided outside the substrate mounting area of the substrate stage so as not to interfere with the photosensitive substrate mounted on the substrate stage. However, particularly for a large and rectangular substrate, if the reference mark is provided outside the substrate mounting area of the substrate stage, the substrate stage becomes large and the moving range of the substrate stage becomes large. Therefore, in order to reduce the size of the stage while suppressing costs and maintaining accuracy, a reference mark that moves up and down is provided in the area where the substrate of the substrate stage is placed, and the reference mark is moved up and down as necessary. The position of the plate alignment system is detected while moving to avoid interference with the plate, and the base line of the exposure apparatus is measured, or the position of the original is measured.

[0003]

According to the above-described exposure apparatus, the mechanism for mechanically raising and lowering the reference mark is not always easy to maintain the mechanical accuracy of the driving mechanism at a high level. When it is necessary to place the stage in the limited space of the stage and move the reference mark upward to detect the position of the plate alignment system and especially the position of the reticle mark on multiple reticles (original), The time required to measure the position of each reticle and the position of the plate alignment system becomes considerably long, and because the reference mark itself moves up and down, force is applied due to movement of the substrate stage, etc. Due to the thermal factors such as, the reference mark itself drifts,
There was a problem that the measurement value changed over time.

Accordingly, an object of the present invention is to provide an exposure apparatus provided with a reference mark having excellent static stability.

[0005]

In order to achieve the above object, an exposure apparatus according to the present invention comprises a projection optical system PL for projecting a predetermined pattern onto a photosensitive substrate 202 as shown in FIG. A substrate stage 201 on which the photosensitive substrate 202 is mounted and movable in the optical axis AX direction (Z-axis direction) of the projection optical system PL and in a two-dimensional direction (XY direction) orthogonal to the optical axis AX direction. And alignment optical systems 131 to 131 used for two-dimensional alignment of the photosensitive substrate 202
Reference marks 141 and 142 for calibrating the positions of the alignment optical systems 131 to 134 in the two-dimensional directions XY.
Reference marks 141 and 142 are provided on the substrate stage 2
01 is fixed to a predetermined position inside the substrate stage 201 at a predetermined distance t ₂ from the upper surface of the substrate stage 20;
The moving range T in the direction of the optical axis AX 1 (FIG. 2A) is configured to be equal to or greater than the sum of the thickness t ₁ of the photosensitive substrate 202 and a predetermined distance t ₂ .

According to this structure, the reference mark is fixed at a predetermined position inside the substrate stage at a predetermined distance from the upper surface of the substrate stage. That is, the reference mark does not contact the substrate when the substrate is placed on the substrate stage. Therefore, the reference mark and the substrate do not damage each other. Also, typically, the reference mark is provided in a region of the substrate stage on which the photosensitive substrate is placed. In this case, the substrate stage on which a large substrate is placed can be formed relatively small.

The moving range T of the substrate stage in the direction of the optical axis is configured to be equal to or greater than the thickness t ₁ of the photosensitive substrate and a predetermined distance t _2. By moving the substrate stage in the optical axis direction when is not mounted, the reference mark can be matched to the substrate surface position when the substrate is assumed to be mounted, that is, the height of the exposure surface. . Therefore, when the position of the base line or the original plate of the plate alignment system is to be measured, the reference mark provided on the substrate stage can be kept in focus.

In the above-described exposure apparatus, the reference mark 141 may be formed in a phase pattern (FIG. 9) that can transmit at least the exposure light.

In this case, since the reference mark is formed of a phase pattern that can transmit the exposure light, the reflection light for the alignment light can be generated while the reflection light for the exposure light can be reduced.

In the above exposure apparatus, the information storage means 207 may be provided.
At this time, using the information on the sum of the thickness t ₁ of the photosensitive substrate and the predetermined distance t ₂ stored in the information storage unit 207, the substrate stage is moved in the Z direction to project the reference mark. It can be adjusted to the focus position of the optical system.

In order to achieve the above object, an exposure apparatus according to a fourth aspect of the present invention provides a projection optical system PL for projecting a predetermined pattern onto a photosensitive substrate 202 as shown in FIG.
With the photosensitive substrate 202 placed on the upper surface and the projection optical system P
Two-dimensional direction XY orthogonal to the optical axis AX direction (Z direction) of L
Stage 201 which can be moved to the photosensitive substrate 202;
Alignment optical systems 131 to 134 used for alignment in two-dimensional directions (XY directions); alignment optical system 1
Reference marks 141 and 142 for calibrating the two-dimensional positions of 31 to 134;
Are predetermined distances t ₂ and t ₃ from the upper surface of the substrate stage 201
Substrate stage 201 separated by (FIGS. 2A and 11)
Fixed at a predetermined position inside the reference mark;
2 has a surface reflectance of 20% or less with respect to exposure light.

With this configuration, since the surface reflectance of the reference mark with respect to the exposure light is 20% or less, even if the exposure light transmitted through the substrate is reflected by the reference mark, it may adversely affect the photosensitive layer of the substrate. Absent.

In order to achieve the above object, an exposure apparatus according to a fifth aspect of the present invention provides a projection optical system PL for projecting a predetermined pattern onto a photosensitive substrate 202 as shown in FIG.
With the photosensitive substrate 202 placed on the upper surface and the projection optical system P
The two-dimensional direction (X) orthogonal to the optical axis AX direction (Z direction) of L
A substrate stage 201 movable in the Y direction); alignment optical systems 131 to 134 used for two-dimensional alignment of the photosensitive substrate 202;
Mark 1 for calibrating two-dimensional positions of
Reference marks 141 and 142 are provided in the region of the substrate stage 201 where the photosensitive substrate 202 is placed and at predetermined distances t ₂ and t ₃ from the upper surface of the substrate stage 201 (FIG. 2A). 11) only substrate stage 2
01 and fixed to the substrate stage 201; the reference marks 141 and 142 are provided on a transparent reference plate 141.
a, 142a formed on the surface of the alignment system 1
The reference marks 141 and 142 have a surface reflectance of 8% or more with respect to the alignment light used for performing alignment by 31 to 134.

Since the reference mark is formed on the surface of the transparent reference plate, the alignment light transmits through the front surface of the reference plate and is reflected by the back surface and returns. However, the surface reflectance of the reference mark is 8% or more. Therefore, the reflected light of the reference mark is greater than the intensity of the combined light reflected on the front surface and the light reflected on the rear surface of the reference plate, and the reference mark can be easily identified.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or corresponding members are denoted by the same reference numerals, and redundant description will be omitted.

FIG. 1 is a perspective view showing a schematic configuration of an exposure apparatus according to an embodiment of the present invention, and FIG. 2 is a side view of the exposure apparatus shown in FIG. In FIG.
The illumination optical system 100 is arranged so as to illuminate a reticle 121, which is an original on which a pattern is formed, from vertically above. Reticle 121 is placed on reticle table 206 (FIG. 2). A projection lens system PL, which is a projection optical system, is disposed below the reticle table 206. A plate 202, which is a photosensitive substrate, is placed below the reticle table 206 at a position whose surface is conjugate with the reticle with respect to the projection lens system PL. Substrate stage 2 on which to place it
01 is arranged.

Above reticle table 206, reticle alignment system 11 for determining the position of the reticle
3 is provided fixedly with respect to the projection lens system PL or the exposure apparatus.

Here, it is assumed that the Z axis is in the direction of the optical axis AX of the projection lens system PL, and the XY rectangular coordinate system is in a plane orthogonal to the Z axis. The X-axis direction and the Y-axis direction (also referred to as the X direction and the Y direction, respectively) are the two-dimensional directions of the present invention.

In addition, one or more, for example, four substrate (plate) alignment systems 131 to 134 (in FIG. 1, reference numeral 134 denotes a shadow of the projection lens system PL) above the substrate stage 201 in the Z-axis direction (also referred to as Z direction as appropriate). (Not shown in the figure) is fixedly arranged with respect to the projection lens system PL. The four plate alignment systems are arranged so as to be located near four corners of, for example, a square plate to be exposed by this apparatus.

Further, as shown in the enlarged view of FIG. 2A, the substrate stage 20 is sunk from the upper surface of the substrate stage 201 by a predetermined distance t ₂ which is a predetermined distance in the Z direction.
In the position inside 1, one or more, for example, two reference marks 1
41 and 142 are fixedly provided. The movable range T of the substrate stage 201 in the Z-axis direction by the substrate driving device 205 shown in FIG.
_1, and is configured to be greater than or equal to the sum of the distance t ₂ which has sunk slightly from the top surface of the substrate stage 201 as described above.

The illumination optical system 100 includes an ultra-high pressure mercury lamp 101 as a light source, a reflecting mirror 102, and a collimating lens 10.
3. Optical integrator 104, half mirror 1
07, relay lens 108, reticle blind 10
9, a reticle blind imaging optical system 110, a reflecting mirror 111, and a condenser lens 112 (FIG. 2) arranged in this order. In this way, the reticle 121 placed on the reticle table 206 is uniformly illuminated by the illumination light via the condenser lens 112.

The projection lens system PL and the substrate stage 2
01, the substrate stage 201 is connected to the projection lens system P.
An oblique incidence type autofocus system 204 for adjusting the focus position to L is provided.

As shown in FIG. 2, a Z-direction driving system 205 is attached to the substrate stage 201, and an appropriate Z-direction driving system 205 is electrically connected to the Z-direction driving system 205 by a controller 208. The position is driven and set. Further, the information storage means 207 (FIG. 1) is electrically connected to the control device 208. The information storage unit 207 stores and stores the sum of the thickness t _{1 of the} plate to be exposed by the exposure apparatus and the sink distance t ₂ of the reference mark 141 from the upper surface of the substrate stage.

The control device 208 is provided with the information storage means 20 as needed.
7, information is called from the substrate stage 201 by that value.
Is driven up and down by the Z-direction drive system 205, and when the plate 202 is placed on the substrate stage 201 and exposure is to be performed, the projection lens system PL is focused on the exposure surface of the plate 202 and the plate 202 is When the reference mark 141 is not placed on the top and the reference mark 141 is used to measure the baseline of the plate alignment system or to measure the position of the reticle, the reference mark 141 is used.
Can be focused on the projection lens system PL.

Here, the information storage means 207 is the control device 2
08 may be integrally incorporated.

Further, as shown in FIG. 2, below the reference mark 141, inside the substrate stage 201, a reflecting mirror 172 is formed at an angle of approximately 45 degrees on the upper surface of the substrate stage 201, In the optical path deflected in parallel to the upper surface of 201, a relay lens 171 is provided.
However, the light guide fiber 3
03 end faces are arranged. That is, the reference mark 141
Below, alignment optical systems 131-134,
Alternatively, the light receiving optical system or a part thereof for performing at least one of the calibration of the position of the reticle 121 is provided on the substrate stage 20.
It is buried in 1.

On the other hand, the reflecting mirror 102 in the illumination optical system 100
A shutter 301 is provided between the light source 101 and the collimating lens 103 so that the light from the light source 101 can be switched to the collimating lens 103, that is, to the main illumination optical path or to the light guide fiber 303. Have been.

The end surface of the light guide fiber 303 opposite to the relay lens 171 faces the shutter 301 via the condenser lens 302.

For the reference mark 142, a similar optical system is embedded in the substrate stage 201.

An interferometer 2 for measuring the position of the substrate stage 201 in the X and Y directions is provided at the end of the substrate stage 201.
A moving mirror 203a for the camera 03 is fixed. Although FIG. 2 shows only an interferometer for position measurement in the X direction, an interferometer for the Y direction is also provided.

Further, as shown in FIG. 2, the substrate stage 201 has on its side a displacement measuring system for measuring the displacement of the plate stage 201 in the Z direction, for example, a Z-direction drive incorporating a measuring system such as an encoder or a potentiometer. System 205
Is provided. By the Z-direction drive system 205, the plate stage 201 can be moved to a position of displacement measured in the Z-axis direction in advance.

The movement of the substrate stage 201 in the Z direction is as follows.
In the example of FIG. 2, the upper half and the lower half of the substrate stage 201 are separated by a slope inclined with respect to the Z direction axis, including an axis parallel to the Y axis, and the needle bearing 201 b is provided on the separation surface. It is performed by a sandwiched structure. Instead of the needle bearing 201b, a gas bearing may be used in which pressurized air is blown into the slope and both slopes slide relatively parallel to the plane with a gap on the order of microns. Here, when the lower half of the substrate stage 201 is driven in the X direction, the upper half moves up and down.

In such a configuration, the reticle 121
When exposing the above pattern on the plate 202,
The light of a light source 101 such as an ultra-high pressure mercury lamp is selected to have a wavelength for exposure (for example, g-line, h-line, i-line) by an interference filter or the like (not shown).
21 is illuminated, and the pattern on the reticle 121 is transferred onto the plate 202 (shown by a dotted line in FIG. 1) by the projection lens system PL.

A large liquid crystal panel is formed by performing joint exposure using this exposure operation using a plurality of reticles 121 to 124, for example.

Here, the baseline will be described.
Generally, the reference position of the exposure apparatus is determined by a reference mark 141 disposed on the stage 201, and the reference mark 141 allows the reticle 1 to pass through the projection lens system PL.
The position of the reticle 121 via the projection lens system PL in the stage coordinate system is obtained by collating with the alignment mark RM11 and the like (FIG. 3). Further, the plate 202
In the second exposure, the plate alignment systems 131 to 134 are used to detect the position of the plate exposed to the first layer in the second and subsequent layers. The position of 134 is determined by a coordinate value in the stage coordinate system. The coordinate value thus obtained is a so-called baseline of the exposure apparatus. Generally, before the exposure, the above-described process is performed, and the position of the plate loaded on the stage 201 of the exposure apparatus is adjusted, the alignment is performed using the value of the baseline, and the exposure of the second and subsequent layers is started. .

An operation method for measuring the baseline of the exposure apparatus according to the embodiment of the present invention shown in FIGS. 1 and 2 will be described. First, in a state where the plate 202 is not placed on the plate stage 201, the plate stage 201 is moved to a position of displacement measured in the Z-axis direction in advance.
It is moved by the direction drive system 205.

The position of the displacement in the Z-axis direction is treated as a constant at the time of assembling the apparatus, and is an amount set so that the surfaces of the reference marks 141 and 142 substantially coincide with the focal plane of the projection lens system PL. Then, the plate stage 201 is driven. However, a change in the focus position due to irradiation of the projection lens system PL, a change in the focus position due to a change in atmospheric pressure, and a change in the focus position when the magnification varying mechanism in the projection lens system PL is operated are constants thereof. Has been corrected in the form added to.

Here, as shown in FIG. 1, two fiducial marks 141 and 142 are provided, and the distance between them is set to any two of the four plate alignment systems, for example, 132 and 133 as shown in FIG. By arranging them so as to be substantially the same as the interval between 131 and 134, it is possible to reduce the stroke of moving the substrate stage in the X and Y directions when measuring the baseline, and thus avoid increasing the size of the stage 201. Can be.

Next, of the reference marks 141 and 142,
For example, first, the reference mark 141 is measured by the auto-focus system 204 so that the focal point of the projection lens system PL is accurately set, and the plate stage 201 is accurately set on the focal plane of the projection lens system PL.

Here, the two displacement measurement systems, the displacement measurement system of the plate stage 201 and the autofocus system 204, are used, for example, when the normal exposure is completed and the next layer is prepared for exposure. Plate 202 that has been exposed
To set the plate stage 201 to the in-focus position of the reference mark 141 in parallel during the time required to set the reticle 122 for starting exposure next to the reticle changer. is there.

Next, the baseline measurement using the reference mark 141 will be described with reference to FIGS. 2, 3, and 4. FIG. First, the reticle 121 is placed on the reticle table 206.
Is mounted on the reticle 121, and a reticle alignment mark composed of cross slit marks RA1 and RA2 (FIG. 3) is formed at two predetermined positions on the reticle 121 by the reticle alignment system 113.
Reticle alignment marks RA11 and RA1 by moving reticle table 206 with respect to a reference slit (not shown) of reticle alignment system 113.
Fit 2

Subsequently, using the reference marks 141, the alignment marks RM11 to RM1 arranged at substantially four corners of the reticle 121 set on the reticle table 206.
4 (FIG. 3) is measured.

Next, the reference mark 142 is auto-focused by the auto-focus system 204, and the plate stage 201 is moved in the Z-axis direction so that the reference mark 142 coincides with the focal plane of the projection lens system PL. Mark RM of reticle 121 measured using 141
The positions of 11 to RM14 are measured.

In this measurement, the light reflected by the shutter 301 arranged in the optical path of the main illumination system 100 is guided to the light guide fiber 303,
The reference mark 142 is illuminated via reference mark illumination systems 171 and 172 embedded inside the reference mark 142. The illumination light is selected at an exposure wavelength by an interference filter (not shown) or the like.

The illuminated image of the reference mark 142 is formed on the alignment marks RM11 to RM14 on the reticle 121 via the projection lens system PL. Further, the light transmitted through the alignment marks RM11 to RM14 of the reticle 121 is reflected by a half mirror 107 in the illumination optical system 100 through a part of the illumination optical system 100, and is reflected on a photoelectric conversion element 105 such as a photomultiplier. Received.

Here, the pattern of the reference mark 142 and the alignment marks RM11 to RM14 of the reticle 121 are set.
Is a slit mark as shown in FIGS. 4A and 4B, for example, and a signal detected by the light receiving element 105 by scanning the stage 201 has a peak as shown in FIG. By drawing a bilaterally symmetric curve having, for example, a midpoint detection based on a slice level cut in the scanning direction at a certain signal level value, the plate stage 2
The coordinates of the substrate stage 201 corresponding to the alignment marks RM11 to RM14 of the reticles 121 to 124 can be measured by the interferometer 203 of No. 01.

Thus, the relative positions of the reference mark 141 and the reference mark 142 are measured using the alignment marks RM11 to RM14 of the reticle 121 measured by the reference mark 141 and the reference mark 142.

Next, plate alignment systems 131 and 13
2 is measured using the reference mark 141, and further, using the reference mark 142, the plate alignment system 13 is measured.
The positions of 3, 134 are measured. This measurement can be performed, for example, by arranging marks similar to the marks for performing alignment of the plate 202 on the reference marks 141 and 142, for example.
By performing normal signal processing such as image processing and detection of diffracted light by laser light, the plate alignment systems 131 to 131 can be used.
The position of 134 can be measured.

At this time, in order to measure the positions of the plate alignment systems 131 to 134 using the reference mark 141,
An alignment wavelength for performing plate alignment is used. At this time, if a signal intensity difference of about twice is obtained between the pattern portion of the reference mark 141 and the portion that is not,
Since there is little influence on the measurement accuracy, about 4% of the reflected light of the portion without the pattern is measured as noise when the surface is a glass surface, whereas the reflected light of the pattern portion is more than twice that of 8% or more. It is desirable to have reflectivity.
If the reflectance is 8% or more or exceeds 8%, the measurement accuracy can be maintained even in consideration of the light transmitted through the glass surface, reflected inside the glass, and returned. More preferably, the content is 10% or more.

Alternatively, the reflectance may be twice or more the surface reflectance of the reference plate or more than twice.

From the above, the relative position between the reticle 121 and the plate alignment systems 131 to 134, that is, the so-called base line is measured. Here, reticle 121
The four alignment marks RM11 to RM14 are measured to accurately determine the relative position between the reference mark 141 and the reference mark 142 by increasing the number of measurement points. In principle, at least one point is sufficient. .

Next, the reticle 121 is
First, the reticle 122 is aligned with the reticle alignment system 113 using the reticle alignment marks RA21 and RA22 so as to be at the same position as the reticle 121 (FIG. 7).

Subsequently, the reticle alignment marks RM21 to RM24 of the reticle 122 are measured using the reference mark 141. Thus, the relative position of reticle 122 with respect to reticle 121 can be obtained.

For example, when the reticle 122 is
As a result of measurement using reticle 1, X
If the position shifted by δ in the direction is determined to be optimal,
Reticle alignment system 113 and reticle 1 listed above
22 reticle alignment marks RM21 to RM24
It can be seen that the reticle 122 should be set with a shift of δ using.

Similarly, reticle 123 and reticle 1
24, the reticle 121 of each reticle
Can be obtained. In this way, the position of each reticle that minimizes the seam with the four reticles using the reticles 121 to 124 is determined.

Next, each of the measured reticles 121 to 124
To start the exposure operation. First, complete the baseline measurement.
At the same time, the stage 20 is moved by the preset amount.
1. Plate with potentiometer to measure Z direction displacement
Lower the stage 201. At this time, the storage means 207
Stored (at this time, exposure) photosensitive
Rate thickness t₁And the sink amount t of the reference mark 141_TwoWith
The sum is called from the information storage means 207 to the control device 208.
If the substrate stage 201 is lowered in the Z direction
Good. The movable amount T of the substrate stage 201 in the Z direction is
Rate thickness t ₁And the sink amount t of the reference mark 141_TwoWith
This movement control is possible because the
Noh.

The sum data of the plate thickness t ₁ and the sinking amount t ₂ of the reference mark 141 is stored in the information storage means 207 as values corresponding to various plate thicknesses, and exposure is performed. The data corresponding to the corresponding plate may be called and used.

Further, the plate stage 201 is moved to a position where the plate 202 for performing exposure is carried onto the stage 201, and the plate 202 is placed.

With the plate 202 mounted, autofocus is performed using the autofocus system 204, and the surface of the plate 202 is set at the focal position of the projection lens system PL. Here, the stage 201 is lowered so that the plate stage 201 has a desired displacement.
If the parallel processing is performed so that the processing is completed while the stage 201 is moving to the loading position of No. 02, the plate 202 is placed on the stage 201, and furthermore, the auto focus is performed, the throughput is improved. Can be prevented from deteriorating.

Here, the first layer is exposed by moving the plate stage 201 to a desired XY coordinate position. When performing overlay exposure, first, plate 2
02, the XY coordinate position of the plate 202 is measured by detecting the alignment marks of the previous process by the plate alignment systems 131 to 134, and statistical processing is performed so as to optimize the overlay accuracy. The amount is corrected and the overlay exposure is started.

In the case of exposure, most of the substrates used for manufacturing liquid crystal display elements are glass plates, and the layers to be patterned are various metal layers, ITO, and the like.
And the like, the thickness of the film is about several tens to several hundreds of angstroms, and if this thickness is considered, there is naturally a semi-transparent film. That is, at the time of exposure, the plate 202 is placed on the reference marks 141 and 142, so that the exposure light passes through the plate 202 and reaches the surfaces of the reference marks 141 and 142.
Since the light reflected by 41 and 142 may adversely affect the photosensitive layer of the plate 202, the surface reflectance of the reference marks 141 and 142 for exposure needs to be as small as possible.

However, during the actual exposure, most of the exposure light is absorbed by the resist applied to the surface of the plate, and the reflectance of the surface of the stage 201 on which the plate 202 is mounted is about ten and several percent. In consideration of this, it is only necessary to secure a reflectance of 20% or less with respect to the exposure light at least. More preferably, the content is 10% or less.

However, depending on the conditions for performing the exposure, the amount of exposure may be considerably higher than the appropriate amount of exposure. Therefore, it is necessary to set the amount of the exposure to be equal to or less than the reflectance of the surface of the substrate stage 201 on which the plate 202 is mounted. desirable.

Also, by suppressing the reflectance of the reference marks 141 and 142, there is no need to provide a mechanical shutter between the reference marks 141 and 142 and the substrate stage 201 for shielding light during exposure. 14
Reference numerals 1 and 142 denote several tens to 200 μm from the surface (upper surface) of the plate stage 201 on which the plate 202 is mounted.
It is enough to provide a certain level of clearance.
02 is 0.7 mm, for example.
It suffices if there is a movement range of the stage 201 in the Z-axis direction of about 9 mm. That is, by suppressing the reflectance as described above, it is not necessary to provide a shutter between the upper surface of the substrate stage and the reference mark, so that a sufficiently realistic driving range can be obtained.

If the thickness of the plate 202 to be exposed is 1.2 mm, the moving range T of the substrate stage 201
May be set to 1.2 to 1.4 mm. That is, the movement range T of the substrate stage 201 may be set to a value greater than the sum of the thickness of the plate having the maximum thickness and the sinking amount of the reference mark among the plates to be exposed.

Here, an error such as a shift generated when the plate stage 201 is moved up and down is caused by the laser interferometer 203 for measuring the X and Y positions of the plate stage 201 and the movable mirror 203a. Since it moves in the optical axis direction, that is, the Z-axis direction, every 203a, the coordinates of the focal plane of the projection lens system PL are always measured, and no error occurs.

For example, even if the movable mirror 203a itself is inclined in the optical axis AX direction of the projection lens system PL, that is, in the Z-axis direction, the relative position between the reticle 121 and the plate alignment systems 131 to 134 at each displacement of the stage 201. This does not cause a problem because no change occurs.

The order of the baseline measurement operation described in the present embodiment is not specified. For example, the positions of the reticles 121 to 124 are measured before measuring the base lines of the plate alignment systems 131 to 134. Is also good.

The second embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 5, in the present embodiment, reticle marks RM11 to RM14 (FIG. 3)
It is characterized in that the illumination light of the main illumination system 100 is used as a system configuration for detecting the reference marks 141 and 142.

In FIG. 5, a reflecting mirror 172 is provided on the inside of the substrate stage 201, below the reference mark 141 fixed to the substrate stage 201 by being slightly sunk below the upper surface of the substrate stage 201. Are fixed at an angle of about 45 degrees. A relay lens 171 is arranged in an optical path deflected substantially parallel to the upper surface of the substrate stage by the reflecting mirror 172, and a photoelectric conversion element 181 is fixed to the substrate stage 201 in an optical path beyond the relay lens 171.

In such a structure, the reticle alignment marks RM11 to RM14 on the reticle 121 are illuminated by the main illumination light from the light source 101, and an optical image of the reticle alignment marks RM11 to RM14 by the projection lens system PL is used as a reference. An image is formed overlapping the mark 141,
The light from the images of the reticle alignment marks RM11 to RM14 and the light passing through the reference mark 141 are converted by the photoelectric conversion element 1
It is guided to 81 by a relay lens 171.

The photoelectric conversion element 181 is connected to the substrate stage 20
However, in order to reduce thermal expansion due to heat generation of the light receiving element 181 itself, the light receiving element 181 may be guided to a place not affected by heat by an optical fiber. As the light receiving method, a so-called slit scan method using a slit opening, a knife edge method using an edge of a pattern, and the like can be considered. If the light receiving element 181 has uneven sensitivity, a diffusion plate or the like may be used.

FIG. 6 shows the substrate stage 20 in the light receiving sensor section.
In this case, there is provided an enlargement optical system that uses the image sensor embedded in the optical element 1 and enlarges the image of the reference mark 141 to guide the image to the image sensor. In the figure, up to the reflection mirror 172 and the relay lens 171,
The configuration is similar to that of FIG.
Further, a relay lens 173 is provided in the optical path ahead of this, and an image pickup device 182 such as a CCD is provided further therefrom. In this embodiment, a magnifying optical system is constituted by the relay lenses 171 and 172. In this magnifying optical system, the light receiving surface of the image sensor 182 and the reference mark 141 have a conjugate relationship.

In such a structure, the optical image of the reticle alignment mark illuminated by the main illumination light from the light source 101 by the projection lens system PL is used as the reference mark 1
An image of the reticle alignment mark and an image of the reference mark 141 are formed on the photoelectric conversion element 182 by the magnifying optical systems 171 and 173.

A reticle mark suitable for this case is, for example, as shown in FIGS. 7 and 8, a square annular mark shown in FIG. 8A is arranged as a reference mark 141, and a cross mark shown in FIG. When the marks are arranged, the composite image projected on the image sensor 182 is a cross-shaped mark in which a square annular mark and a cross mark are overlapped as shown in FIG. 8C.

The difference δ between the center position of the square annular mark of the reference mark 141 and the center position of the cross mark of the reticle mark is measured by image processing to obtain the reference mark 14.
1 and reticle marks RM21 to RM24 can be detected relative to each other.

This is shown in FIGS. 8 (d) and 8 (e). That is, a position deviating from the center of the cross in FIG. 8C is scanned in parallel with the vertical and horizontal lines of the cross, and when the obtained signal level is detected, an output having three peaks is obtained. If it is determined how much the center peak is shifted from the center of the left and right peaks, the difference is the difference δ.

When the main illumination light is used, the reticle blind 109 is used to prevent thermal expansion due to irradiation.
, The area of each measurement point, that is, the reticle mark R
When measuring M21, reticle mark RM21
In addition to narrowing the irradiation area to the peripheral area of the light source and optimizing the illuminance of the exposure light, a dimming means (not shown) is provided in the illumination optical system 100, and the dimming means is used at the time of exposure and at the time of measurement. A movable mechanism that can be inserted into and removed from the optical path may be provided in the illumination optical system 100 in particular. The light-reducing means may be provided at any position in the illumination optical path. However, in order to form the reticle blind 109, the light source 101 and the fly-eye (optical integrator) 104 which are less affected by illumination unevenness, illumination telecentricity, etc. It is desirable to put in between.

Referring to FIG. 9, a case where a phase pattern is used as a reference mark in the second embodiment will be described. FIG. 9A is a plan view of the reference mark, and FIG. 9B is a cross-sectional view taken along line AA of FIG. Also,
(C) (d) (e) is sectional drawing which shows the mode of reflection or transmission of light in the step of a phase pattern.

In the second embodiment, the alignment marks RM 21 to RM 2 of the reticle 121
When measuring the reference mark 141 and the reference mark 141, for example, as shown in FIGS.
By forming a phase pattern having a step with an almost transparent member such as O _2, it is possible to suppress the reflectance due to exposure light having a wavelength of λ, and in particular, the step of the pattern of the reference mark 141 to mλ / If 2 (m is an integer), the image information of the pattern cancels out due to interference.
It is valid.

This phenomenon will be described in more detail with reference to FIG. In the figure, when the phase difference between two reflected lights at the adjacent high and low stages of the phase pattern is shifted by mλ, no difference occurs between the two lights. That is, when the step is d, if 2 × d = mλ, it becomes impossible to distinguish between a portion having a step and a surface having no step pattern, and information of an image disappears. This is similar to the case where only uniform reflected light exists on the entire transparent member. Therefore, it is possible to prevent the photosensitive layer on the plate surface from being adversely affected by the reflected light from the reference mark.

Further, since the reference mark 141 is positioned by transmitted light, if the transparent member on which the reference mark 141 is formed is, for example, SiO ₂ having a refractive index of 1.5, the step is (2L + 1) λ. Can be set, the transmitted light is strengthened and the image signal becomes a peak (L is an integer).

This phenomenon will be described in more detail with reference to FIG. In the figure, when the phase difference between two lights passing through the adjacent high and low steps of the phase pattern is (L + 1/2) λ, the information of the two transmitted lights becomes maximum. Assuming that the step is d and the refractive index is p, the phase difference is (p-1) d, so that the information becomes maximum when (p-1) d = (L + 1/2) λ. Here, if the refractive index p = 1.5 is substituted, the information becomes maximum when d = (2L + 1) λ.

In the alignment system, the reference mark 14
Calibration can be performed using the reflected light of the alignment light from No. 1 in consideration of the intensity of the reflected diffraction light with respect to the alignment light in this case.
If _2, resulting in constructive when satisfying the step of _{(2n + 1) · λ 2} /4.

This phenomenon will be described in more detail with reference to FIG. In the figure, the phase difference between two reflected lights at the adjacent high and low stages of the phase pattern is (n +＋ １) λ ₂
When they are shifted by only one, the information by the two lights becomes maximum (n is an integer). That is, when the step is d, 2 × d =
If (n + 1/2) λ 2, information is maximized by the interference of the reflected light of the high stage and a low stage. That is, d = (2n + 1)
Information at the time of the · λ _2/4 so that is maximized.

If an optimum solution is obtained under the above three conditions, the conditions under which alignment and exposure can be performed most effectively can be set.

FIG. 10 is a schematic diagram showing a case where the plate 202 is actually exposed. In the figure, plate 202
Resist 2 on the surface of the glass plate 202a constituting
02b is applied. The plate 202 is placed on the upper surface of a substrate stage (substrate holder) 201 with the resist 202b facing upward. When the plate 202 is placed on the inside of the substrate stage 201 separated by a predetermined distance from the upper surface of the substrate stage 201, that is, when the plate 202 is placed on the upper surface of the substrate stage 201, the plate 202 is slightly separated from the upper surface of the substrate stage 201 only so as not to contact the plate 202. A reference mark 141 is provided at the sunk position.

FIG. 10 shows that the exposure light L1
A state where the light is reflected from the surface of the member on which the reference mark 141 and the reference mark 141 are formed and a state where the alignment light L2 is reflected from the lattice pattern portion are shown.

Further, in order to prevent the pattern of the reference mark from being transferred to the plate, the pattern of the reference mark is formed at a small interval, so that the diffracted light by the pattern is spread and the pattern image is substantially formed on the plate. It is also possible to prevent formation.

In the above embodiment, when the substrate stage 201 is moved up and down between the baseline measurement and the reticle position measurement operation and the exposure operation, the thickness of the photosensitive plate can be reduced without using the autofocus system 204. The throughput can be increased by raising and lowering the sum of the height t ₁ and the sinking amount t ₂ of the reference mark at once. Further, for example, in order focuses on the reference mark when measuring the position of the reticle, when raising the substrate stage 201, a stretch is increased by t ₁ + t _2, the projection lens system P
When the focal length is within the focal depth of L, the reticle position measurement does not need to be focused as accurately as at the time of exposure, so that the baseline measurement can be started as it is. Similarly, in some cases, it is not necessary to perform autofocus for the purpose of alignment.

Even when autofocus is performed by the autofocus system 204, the thickness t _{1 of the} photosensitive plate
The time required for autofocusing can be significantly reduced by raising and lowering the sum of the reference mark and the sinking amount t ₂ of the reference mark at once.

As described above, when at least one of the alignment optical system and the position of the reticle is calibrated with the reference mark, the displacement of the projection lens system PL of the plate 202 in the optical axis direction when the plate 202 is exposed. Is measured by a displacement measuring means for measuring the distance, and is performed by moving the substrate stage 201 by a Z moving means for moving the substrate stage 201 in the optical axis direction of the projection lens system PL.

In the exposure apparatus of the above embodiment, when at least one of the positions of the alignment optical systems 131 to 134 or the reticle 121 is calibrated with the reference mark, the exposure of the plate 202 is performed. Plate 2
02, the displacement of the projection lens system PL of the substrate stage 201 in the optical axis direction is measured independently of the displacement measuring means for measuring the displacement of the projection lens system PL in the optical axis direction (Z-direction drive system 2).
Z moving means for moving the substrate stage 201 in the optical axis direction of the projection lens system PL by a driving amount measured in advance by the second displacement measuring means, for example, the sum of the thickness of the plate and the amount of sinking of the reference mark. It can be said that it is configured to move by 205.

When at least one of the calibration of the position of the alignment optical system or the reticle is performed by the reference mark, the second displacement measuring means and the plate 2
02 when the projection lens system PL of the plate 202 is exposed.
The substrate stage 201 may be moved to a position measured in cooperation with the displacement measuring means for measuring the displacement in the optical axis direction by the Z moving means for moving the substrate stage 201 in the optical axis direction of the projection lens system PL. .

When at least one of the positions of the alignment optical systems 131 to 134 and the reticle 121 is to be calibrated using the reference mark, the substrate stage 201 is used.
And the position measuring means 203 for measuring the position of the substrate stage 201 may be performed in cooperation with the means for moving the substrate stage 201 two-dimensionally in the XY plane.

Referring to FIG. 11, a third embodiment of the present invention will be described. In the figure, the substrate stage is provided with a cylindrical hole 151 in the Z direction, and is separated from the upper surface of the substrate stage 201 by a predetermined distance t _{3 in} the hole 151.
A reference mark 141 is fixed inside the substrate stage 201. The reference mark 141 is a transparent reference plate 141a.
Is formed on the surface.

Also, a first relay lens 152 is disposed at a position between the upper surface of the substrate stage 201 and the reference mark 141 at a position sunk from the upper surface of the substrate stage 201, and the relay lens 152 and the reference mark 141 A second relay lens 153 is disposed between the two, and the relay lens systems 152 and 153 form a spatial image of the reference mark 141 at a position 154 above the upper surface of the substrate stage 201. ing. Here position 1
The reference numeral 54 is configured so that when the plate 202 is placed on the upper surface of the substrate stage 201, the height coincides with the height in the Z direction at which the exposure surface of the plate 202 is located.

Here, if the surface reflectance of the reference mark 141 with respect to the exposure light is set to 20% or less, preferably 10% or less, as described in the above embodiment,
It is possible to suppress the reflected light from the reference mark from affecting the resist on the substrate. Alternatively, it may be set to be equal to or less than the reflectance of the surface of the substrate stage 201.

The surface reflectance of the reference mark 141 formed on the surface of the transparent reference plate 141a with respect to the alignment light is set to 8% or more. Alternatively, a signal intensity difference of about twice is obtained between the pattern part of the reference mark 141 and the part that is not. By doing so, it is possible to maintain the accuracy of measurement using the fiducial marks, as in the above-described embodiment. This is because if the value is 8% or more, the reference mark can be detected even in consideration of the light transmitted through the glass surface, reflected inside the glass, and returned. More preferably, the content is 10% or more.

As described above, in the exposure apparatus according to the embodiment of the present invention, the reference mark which does not interfere with the plate is not required in the plate mounting area of the substrate stage without the need for a vertical drive mechanism for the reference mark alone. The reference mark itself is composed of a material that is low-reflective to the exposure light or a film that is anti-reflective, so that even if it is a transparent plate, the reflection light of the reference mark is applied to the pattern at the time of exposure. Has no effect. In this way, the so-called baseline measurement accuracy is improved, the screen joining accuracy for forming one panel using a plurality of reticles, and the overlay accuracy when performing overlay exposure on each layer are improved. The device can be provided at low cost.

[0101]

As described above, according to the present invention, since the reference mark is fixed at a predetermined position inside the substrate stage at a predetermined distance from the upper surface of the substrate stage, the reference mark contacts the substrate. Without this, the reference mark and the substrate do not damage each other. In addition, the moving range of the substrate stage in the optical axis direction is configured to be equal to or more than the sum of the thickness of the photosensitive substrate and the distance of the reference mark from the upper surface of the stage. By doing so, the reference mark can be made to coincide with the height of the exposure surface. Therefore, when trying to measure the position of the base line or the original plate of the plate alignment system, the reference mark can be kept in focus. in this way,
According to the present invention, it is possible to provide an exposure apparatus including a reference mark having excellent static stability.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a schematic configuration of an exposure apparatus according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional side view of a part of the exposure apparatus of FIG.

FIG. 3 is a plan view of a reticle used in the first embodiment.

FIG. 4 is a plan view showing an example of slits of a reference mark and a reticle mark.

FIG. 5 is a partially sectional side view showing a schematic configuration of an exposure apparatus according to a second embodiment of the present invention.

FIG. 6 is a partially sectional side view showing a modification of the exposure apparatus according to the embodiment of FIG. 5;

FIG. 7 is a plan view of a reticle used in the second embodiment.

8 is a plan view showing an example of a reticle mark formed on the reticle of FIG. 7 and an example of a reference mark used in combination with the reticle mark.

FIG. 9 is a plan view and a side sectional view showing an example of a phase type pattern used as a reference mark.

FIG. 10 is a side view showing a state in which exposure light and alignment light are reflected by a reference mark.

FIG. 11 is a side sectional view of a reference mark portion used in an exposure apparatus according to a third embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 100 illumination optical system 121 to 124 reticle 131 to 134 plate alignment system 141, 142 fiducial mark 201 substrate stage 202 substrate 207 information storage means 208 control device PL projection lens system

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H01L 21/30 525D

Claims (5)

[Claims] A projection optical system for projecting a predetermined pattern onto a photosensitive substrate; and a two-dimensional optical system in which the photosensitive substrate is mounted on an upper surface and which is orthogonal to the optical axis direction of the projection optical system and the optical axis direction. A substrate stage movable in the direction; an alignment optical system used for positioning the photosensitive substrate in the two-dimensional direction; and a reference mark for calibrating the position of the alignment optical system in the two-dimensional direction; The fiducial mark is fixed at a predetermined position inside the substrate stage separated by a predetermined distance from the upper surface of the substrate stage; the moving range of the substrate stage in the optical axis direction is determined by the thickness of the photosensitive substrate and the thickness of the photosensitive substrate. An exposure apparatus configured to be equal to or greater than a sum of a predetermined distance; 2. The exposure apparatus according to claim 1, wherein the reference mark is formed in a phase pattern that can transmit at least exposure light. 3. An information storage unit for storing information on a sum of a thickness of the photosensitive substrate and the predetermined distance.
The exposure apparatus according to claim 1. 4. A projection optical system for projecting a predetermined pattern onto a photosensitive substrate; and a photosensitive substrate mounted on an upper surface and movable in a two-dimensional direction orthogonal to an optical axis direction of the projection optical system. A substrate stage; an alignment optical system used for positioning the photosensitive substrate in the two-dimensional direction; and a reference mark for calibrating the position of the alignment optical system in the two-dimensional direction; An exposure apparatus fixed to a predetermined position inside the substrate stage at a predetermined distance from an upper surface of the stage; and a surface reflectance of the reference mark to exposure light of 20% or less; an exposure apparatus. 5. A projection optical system for projecting a predetermined pattern onto a photosensitive substrate; said photosensitive substrate being mounted on an upper surface and being movable in a two-dimensional direction orthogonal to an optical axis direction of said projection optical system. A substrate stage; an alignment optical system used for positioning the photosensitive substrate in the two-dimensional direction; and a reference mark for calibrating the position of the alignment optical system in the two-dimensional direction; The reference mark is made of a transparent material that is fixed to the substrate stage by sinking a predetermined distance from an upper surface of the substrate stage into the substrate stage in an area where the photosensitive substrate is mounted on the stage. The reference mark is formed on the surface of a reference plate, and has a surface reflectance of 8% with respect to alignment light used for performing alignment by the alignment system.
An exposure apparatus characterized by the above.