JP2000223388A - Stage and aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To drastically suppress positional accuracy variation due to substrate deformation by providing correcting means for loading one surface of the substrate and correcting the surface shape of the substrate. SOLUTION: Suction holes 21 of a support 2 are set to a negative pressure for sucking a substrate 50 at the top end of the support 2, a vacuum seal 22 is set to a negative pressure to suck and support the back surface of the substrate 50, a controller 9 closes a valve 7 and opens a valve 8, to make the support point surface flush with a reference with a pressure adjusting hollow 3 held open, a height-measuring unit 10 measures the surface height of the substrate 50, the valve 8 is closed, the valve 7 is opened gradually to apply a pressure to the pressure adjusting hollow 3, the height-measuring unit 10 measures the height variation of the substrate 50, the controller 9 makes fine adjustment of the valves 7, 8 to fix the pressure in the hollow 3. Then the substrate 50 surface is corrected. As a result, the positional accuracy variation due to the substrate deformation is suppressed drastically.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithography technique, and more particularly, to a stage on which a substrate to be exposed provided with a coating film of a photosensitive material is mounted and an exposure apparatus using the stage.

[0002]

2. Description of the Related Art In a conventional lithography technique in which a resist pattern is formed on a substrate using an exposure apparatus, the shape of the surface of a substrate to be exposed provided with a coating film of a photosensitive material is deformed in each exposure process. However, there is a problem that the positional accuracy is deteriorated.

For example, when a silicon wafer is chucked on a wafer stage of an exposure apparatus, the back surface of the substrate comes into contact with the shape of the chuck surface when the silicon wafer is chucked on a wafer stage of the exposure apparatus. This is caused by deformation to imitate.

[0004] A chuck for a silicon wafer is composed of a convex portion that forms a contact surface at the top and a groove portion that performs vacuum suction, and the convex portion has a ring arranged concentrically.

In the case of a thick substrate such as a photomask substrate,
It is known that the shift amount of the pattern position on the front surface due to the deformation at the time of back surface chucking is further increased as compared with a relatively thin substrate such as a silicon substrate.

Therefore, in a photomask exposure apparatus and a pattern position measuring apparatus, the substrate is supported at three points and deformed only by its own weight deflection.
There is known a method for improving the reproducibility of the deformation of the shape of the substrate surface in each exposure step. When possible, exposure is performed by correcting the position coordinates based on the deformation amount.

However, in order to fix and support the substrate and to move the stage at high speed, it is necessary to secure sufficient friction. For this reason, techniques for performing point support using a very hard material and preparing a flexible vacuum chuck surface around the point support portion have been developed. JP-A-5-28
No. 3511 proposes a technique for adsorbing at three points of a minute tip to secure a sufficient frictional force. As a result, it is possible to hold the substrate in a deformation caused only by its own weight.

[0008]

By the way, in the case of a photomask, it has been pointed out that a difference in attitude occurs between when the mask is manufactured and when it is used as an original in an exposure apparatus. Normally, when making the mask, hold the light-shielding film surface up,
When used as an original for an exposure apparatus, the light-shielding film is held face down. In addition, when used as an original for an exposure apparatus, the light-shielding film pattern surface is held by a vacuum chuck.

As a result, the substrate is deformed differently between when the mask is manufactured and when it is used as an original for an exposure apparatus,
There is a problem that the pattern position moves. These problems of positional accuracy tend to be significant when a large-diameter, heavy-weight and thick substrate, such as a photomask, is difficult to secure the planar accuracy of the front and back surfaces.

[0010] Here, the substrate has warpage, bending, and uneven thickness, and the parallelism and flatness are different for each substrate. Therefore, even if the above-described three-point support is performed, exposure or measurement of the pattern position is performed in a different deformed state of the substrate, that is, in a distorted state. There is a problem that the value can not be obtained, as a result,
There has been a problem that sufficient positional accuracy cannot be obtained in element manufacturing or the like.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and has as its object to uniquely determine the attitude of a substrate without being restricted by the surface accuracy of the contact surface of the substrate. It is an object of the present invention to provide a stage which can be supported and supported, and which can significantly suppress the variation in the positional accuracy due to the deformation of the substrate, and an exposure apparatus using this stage.

[0012]

According to a first aspect of the present invention, there is provided a stage for supporting a substrate by a supporting portion to uniquely determine and hold the posture of the substrate. A correcting means for applying a load to one surface of the substrate, and correcting the surface shape of the substrate.

According to the first aspect of the present invention, by applying a load to the support surface of the substrate via a gas, a liquid, or a soft material, the substrate is deformed due to unevenness in flatness or deflection due to its own weight. Can be corrected. Thus, when the substrate is a photomask blank or the like, exposure or measurement of the pattern position can be performed in a state where the deformation of the photomask blank has been corrected, and the positional accuracy variation due to the substrate deformation can be achieved. Can be significantly suppressed.

A feature of the invention according to claim 2 is that the surface shape of the substrate is corrected by applying a load to the support-side surface of the substrate by the correcting means to correct the self-weight deflection of the substrate.

According to a third aspect of the present invention, the correcting means includes a mechanism for generating a pressure difference between one surface of the substrate and an opposing surface.

According to a fourth aspect of the present invention, the supporting portion includes an adsorbing means for adsorbing the supporting surface of the substrate.

According to a fifth aspect of the present invention, the correcting means is formed of a film of a soft material which hermetically covers the cavity. By adjusting the pressure, the surface shape of the substrate is corrected.

According to a sixth aspect of the present invention, the correcting means is an airtight space formed on the support surface side of the substrate, and corrects the surface shape of the substrate by adjusting the pressure in this space.

A feature of the invention according to claim 7 is that a measuring means for measuring the flatness of the substrate, a gas supply / exhaust means for adjusting a pressure in the cavity or the space, and the gas supply means based on a measurement result of the measuring means. A control means for controlling the air supply / exhaust means to adjust the pressure in the cavity or the space is provided.

According to an eighth aspect of the present invention, there is provided an exposure apparatus for holding a substrate to be exposed having a photosensitive material film on a stage and performing pattern exposure on the photosensitive material film on the substrate. The stage according to any one of 1 to 7 is mounted, and a load is applied to the back surface of the substrate to be exposed by the stage to correct the shape of the substrate surface, and then the photosensitive material film on the substrate is subjected to pattern exposure. To do.

According to a ninth aspect of the present invention, the correction means provided on the stage has a means for preventing reflection of light transmitted through the substrate to be exposed.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing a first embodiment of the stage of the present invention. The stage 1 has a quadrangular shape, an upper surface of the stage 1 is flat, and a surrounding portion forming a side surface is provided around the upper surface of the stage 1, and the upper part of the surrounding is open. A pressure adjusting cavity 3 formed of a film of a soft material such as rubber is accommodated on the upper surface of the stage 1 and inside the enclosure. The film of a soft material such as rubber on the upper part of the pressure adjusting cavity 3 is in close contact with the back surface of the substrate 50, as described later.

The stage 1 is penetrated by three support portions 2 having a suction hole 21 at the center.
, And its tip penetrates the upper surface of the pressure adjusting cavity 3 and contacts the back surface of the substrate 50.

The pressure adjusting cavity 3 communicates with a gas flow path 5, which passes through the stage 1 and is connected to a pipe 6 outside the stage 1. The pipe 6 is connected to a gas pressure source 11 for supplying nitrogen gas, and a gas injection valve 7 and a gas exhaust valve 8 are provided on the way.

The opening and closing of the valve 7 and the gas exhaust valve 8 are controlled by a control unit 9. This control unit 9
Controls the opening and closing of the valves 7 and 8 based on the measurement result of the height measuring device 10 for detecting the flatness of the substrate 50 such as a photomask blank placed on the pressure adjusting cavity 3.

FIG. 3 is an enlarged sectional view of a portion shown by a circle in FIG. FIG. 4 is a plan view showing details of the surface of the soft material that is in close contact with the substrate 50.

Next, the operation of this embodiment will be described. The exposure apparatus is one in which the stage 1 of the present embodiment is mounted on an i-line reduction exposure type sequential exposure apparatus, and performs a sequential exposure process called step-and-repeat. Exposed substrate 50
Is a photomask blank called No. 6025 manufactured by HOYA Co., Ltd., which is obtained by applying a photoresist to a chromium surface to a thickness of 0.5 μm and performing a soft baking process.
First, it is mounted on a stage of an exposure apparatus.

The substrate 50 is supported at the support point 20 at the tip of the support section 2 of the stage as shown in FIG.

FIG. 5A is a cross-sectional view of a suction portion of the stage 1, and FIG. 5B is an enlarged cross-sectional view of a tip of a support portion 2 which is a suction portion. A vacuum sealing portion 22 made of a soft rubber film is provided around the tip of the support portion 2, and the suction hole 21 of the support portion 2 is set to a negative pressure.
Is sucked (first suction), and the suction hole 21 is set to a negative pressure, so that the inside of the soft rubber film, that is, the vacuum sealing portion 22 is also set to a negative pressure. Is adsorbed (second adsorption) and supported. Thus,
The height and position of the back surface of the substrate 50 are uniquely determined by the three support portions 2.

The support 2 at the above three points is, for example, 1 m
m and an outer diameter of 2 mm.
Are formed. The vacuum sealing portion 22 is formed of a soft rubber film in contact with an outer diameter of 2 mm. The soft rubber film has a thickness of 3 mm, and there is no soft rubber on the top of the convex portion of the support 2.

At three points, the contact portion to the substrate 50 is cylindrical, the end is rounded to reduce the contact area, and the above-mentioned vacuum sealing portion 22 is disposed around the periphery thereof, Adsorption is being performed.

In the second suction, the suction force is reduced by half with respect to the vacuum suction at the three points, and the suction is performed at almost the middle of the atmospheric pressure. As shown in FIG. 6 (B), a 1 mm thick soft rubber film forming the upper part of the pressure adjusting cavity 3 is in close contact with a portion except for a periphery of 5 mm and four corners of 10 mm on the back surface of the substrate 50. I have.

The soft rubber film is provided with irregularities on the substrate 50 side. The end of the soft rubber film is
It has a shape as shown in FIG. 6A in mm and is fixed to a thicker soft rubber frame to form the pressure adjusting cavity 3.

Next, the operation of adjusting the flatness of the substrate 50 will be described. The control unit 9 first closes the valve 7 and opens the valve 8 to directly connect the pressure adjusting cavity 3 to the atmosphere, and sets the surface of the support point 20 to the same height as the reference in the open state. Next, the height of the surface of the substrate 50 is measured at 3 mm intervals by the height measuring device 10 using the autofocus system of the exposure device.

Next, the control unit 9 closes the valve 8, gradually opens the valve 7 to apply an extra pressure to the pressure adjusting cavity 3 with respect to the atmospheric pressure, and uses the height measuring device 10 to change the height of the substrate 50. Is measured. Since the measured value of this height is input to the control unit 9, the height of the central surface of the substrate 50 is about 0.6 μm.
When it rises, the control unit 9 finely adjusts the valves 7 and 8 to fix the pressure in the pressure adjustment cavity 3.

Thereafter, the height of the entire surface of the substrate is measured again by the height measuring device 10, and it is confirmed that the difference in height is within 0.55 μm in a region excluding 10 mm around the substrate 50. . As a result, in the height distribution, no concave portion considered to be associated with its own weight was found particularly in the central portion.

Next, a 20 mm square exposure was repeated 36 times in a region excluding 15 mm around the substrate 50, that is, in a 120 mm square region.

The stage 1 was set so as to move at an acceleration of 0.12 G or less in order to prevent the displacement of the substrate 50. After performing post-baking at 100 ° C. for 10 minutes, it was confirmed that the substrate 50 had returned to room temperature. The substrate 50 was set in a spray developing device, and a developer (AD) controlled at 23 ° C. from a full cone nozzle was used. -10 Tama Chemical)
Was sprayed, rotated at 100 rpm, and developed for 75 seconds, and immediately rinsed with ultrapure water.

Next, after performing baking treatment at 10 ° C. for 20 minutes, plasma descum treatment using wet air was performed by parallel plate type dry etching. Etching is performed at 75 W for 3 minutes.
The resist film thickness decreased by about 0.03 μm. Then, using a mixed gas of chlorine and oxygen, the light-shielding film containing chromium as a main component and having a thickness of about 0.1 μm was etched for 20 minutes. From the monitor of the RF reflected wave intensity, the etching was Just + 35%.

After the resist was removed, the dimension of a space pattern whose design data was 0.8 μm was measured with a confocal microscope. In the dimension measurement, the same point was measured eight times, and the reliability of the data was confirmed. The size of each of the nine locations in the 36 shots is 0.832 μm on average, the variation is 16 nm (3σ), and the difference between the maximum value and the minimum value is 23 nm.
Met.

Next, the positional accuracy of the pattern was measured.
The measurement was performed using a Leica LMS-iPRO measuring device. The measurement was performed at 5 mm intervals in a 120 mm square area. At the pattern position, the magnification error in the x direction and the y direction was recognized to be 0.1 ppm or less, but the distortion considered to be caused by the deformation of the substrate 50 was reduced to 1/5 or less, and 12
It was confirmed that it was ± 3 nm or less in a 0 mm square area.

According to the present embodiment, the substrate 50 is supported at three points by the three support portions 2 of the stage 1, and then a load is applied to one surface of the substrate 50 via the pressure adjusting cavity 3. Since the surface shape can be corrected, the distortion that is considered to be caused by the deformation of the substrate 50 can be reduced to 1/5 or less of the related art. This allows the substrate 5 to be
Since 0 is prevented from being deformed and the positional accuracy of the pattern can be improved, sufficient positional accuracy can be ensured at the time of element manufacture or the like.

FIG. 7 is a sectional view showing a stage according to a second embodiment of the present invention. However, the same portions as those of the first embodiment shown in FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted as appropriate. The stage 1 of the present embodiment is formed in a concave shape as shown in the figure, and an O-ring 81 of soft rubber and a side support portion 82 for supporting the O-ring 81 as shown in FIG.
Is formed.

The side supporting portion 82 has a tubular portion, and the side tubular portion 82 penetrates the concave side surface and projects to the outside. The substrate 50 has the same support portion 2 as in the first embodiment.
After being supported at three points, the side surface of the substrate 50 is brought into contact with the O-ring 81 made of soft rubber, and the tubular portion of the support portion 82 is set to a negative pressure, thereby fixing the side surface of the substrate 50.

Thus, the concave portion of the stage 1 and the substrate 5
The zero support surface forms a pressure regulating cavity 3. Also,
The back surface of the substrate 50 is directly exposed to the atmosphere of the pressure adjusting cavity 3. Further, the inside of the pressure adjusting cavity 3 is painted black in order to prevent the exposure light transmitted through the substrate 50 such as a photomask blank from being reflected.

Although not shown, a gas flow path similar to that of the first embodiment is formed in the pressure adjusting cavity 3 so that the pressure in the pressure adjusting cavity 3 can be adjusted.

Next, the operation of this embodiment will be described. The substrate 50 is mounted on the concave portion of the stage, and the vacuum suction portion 83 shown in FIG. 8 is set to a negative pressure, whereby the substrate 50 is sealed by the soft rubber O-ring 81, and the substrate 50 is suctioned by the side support portion 82. .

As described above, the substrate 50 was held on the stage 1, and the exposure was performed while correcting the surface shape of the substrate. In holding the substrate 50, the vacuum suction unit 83 in FIG. 8 was once reduced to 50% or less of the atmospheric pressure, and after confirming that the vacuum was held, returned to 5% and held. Thereby, the pressure adjusting cavity 3 formed by the concave portion of the stage 1 and the substrate 50
Is sealed.

Next, at the time of exposure, the pressure adjusting cavity 3 is set to have a slight excess pressure, and it is determined that the surface height is within 0.6 μm in the region excluding the periphery of the substrate 10 mm.
Was confirmed from the surface height measurement.

The pattern after exposure was developed and etched to measure the pattern position accuracy. The positional accuracy of the pattern was measured using an LMS-iPRO measuring device manufactured by Leica. Distortion inherent in three-point support is reduced in the pattern position, and in a region of 120 mm square as in the above-described embodiment, the variation in positional accuracy considered to accompany the deformation of the substrate is as follows:
It was less than ± 3 nm.

This embodiment is similar to the first embodiment shown in FIG. 1 and can obtain the same effects.

[0052]

As described in detail above, according to the present invention, the flatness of the contact surface of the substrate is not restricted.
The orientation of the substrate can be uniquely determined and supported, and the variation in positional accuracy accompanying the deformation of the substrate can be significantly suppressed.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a stage according to a first embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a portion shown by a circle in FIG.

FIG. 3 is a plan view of the soft rubber film shown in FIG.

FIG. 4 is a plan view showing support points of the substrate shown in FIG. 1;

FIG. 5 is an enlarged cross-sectional view of a support point of the substrate shown in FIG. 1 and a front end of a support portion that adsorbs the support point.

FIGS. 6A and 6B are a cross-sectional view and a plan view illustrating an operation of adjusting flatness of a substrate by applying extra pressure to a pressure adjusting cavity of the stage shown in FIG. 1;

FIG. 7 is a sectional view illustrating a stage according to a second embodiment of the present invention.

8 is an enlarged cross-sectional view of the vacuum suction unit shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Stage 2 Support part 3 Pressure adjustment cavity 4 Soft rubber film 5 Gas flow path 6 Piping 7, 8 Valve 9 Control part 10 Height measuring device 11 Gas pressure source 20 Support point 21 Suction hole 22 Vacuum sealing part 50 Substrate 81 O Ring 82 Side support part 83 Vacuum suction part

Claims (9)

[Claims] 1. A stage for supporting a substrate by a supporting portion to uniquely determine and hold the posture of the substrate, comprising: a correction unit configured to apply a load to one surface of the substrate, and correcting a surface shape of the substrate. A stage characterized by that. 2. The stage according to claim 1, wherein a surface shape of the substrate is corrected by applying a load to the support-side surface of the substrate by the correction means to correct the deflection of the substrate by its own weight. 3. The stage according to claim 1, wherein the correction means includes a mechanism for generating a pressure difference between one surface of the substrate and an opposing surface. 4. The apparatus according to claim 1, wherein said support section includes a suction means for suctioning a support surface of said substrate.
Stage described in either. 5. The correction means is formed of a film of a soft material which hermetically covers the cavity, and after arranging one surface of the correction means so as to be in close contact with the support surface of the substrate, adjusts the pressure in the cavity. 3. The stage according to claim 1, wherein the surface shape of the substrate is corrected. 6. The correction means is an airtight space formed on the support surface side of the substrate, and corrects a surface shape of the substrate by adjusting a pressure in this space. Stage according to 1 or 2. 7. A measuring means for measuring the flatness of the substrate; a gas supply / exhaust means for adjusting the pressure in the cavity or the space; and controlling the gas supply / exhaust means based on a measurement result of the measurement means. 7. The stage according to claim 5, further comprising control means for adjusting a pressure in the cavity or the space. 8. An exposure apparatus for holding a substrate to be exposed having a photosensitive material film on a stage and performing pattern exposure on the photosensitive material film on the substrate, wherein the stage is used as the stage. Mounting a stage on the substrate, applying a load to the back surface of the substrate to be exposed by the stage, correcting the shape of the substrate surface, and then performing pattern exposure on a photosensitive material film on the substrate. apparatus. 9. An exposure apparatus according to claim 8, wherein said correction means provided on said stage includes means for preventing reflection of light transmitted through said substrate to be exposed.