JP3490068B2 - Photomask storage device, projection exposure apparatus and projection exposure method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved photomask structure, a projection exposure apparatus and a projection exposure method using the same, and a semiconductor device. Further, as a specific application, in a semiconductor integrated circuit manufacturing or the like, a scanning projection exposure apparatus capable of suppressing deformation of a pattern shape when transferring a circuit pattern and a photomask used in the apparatus are provided. Concerning structure and use.

[0002]

2. Description of the Related Art FIG. 4 is a sectional view showing the structure of a photomask unit used as a photomask in this projection exposure apparatus. As shown in FIG. 4, the photomask substrate 1 includes a pellicle film 2, and a photomask pattern 3 is formed on the side covered with the pellicle film 2. The pellicle film 2 is stretched over the frame 4 substantially parallel to the photomask pattern 3 in order to prevent foreign matter such as fine particles in the atmosphere from adhering to the photomask pattern 3. Reference numeral 8 denotes a space surrounded by the photomask substrate 1, the pellicle film 2 and the frame 4. The photomask unit 100 is configured to include the photomask substrate 1, the pellicle film 2, the photomask pattern 3, the frame 4, and the space 8.

FIG. 5 is a perspective view showing the structure of a conventional scanning projection exposure apparatus. As shown in FIG. 5, the exposure light source 18
Light from (specifically, oscillated F2 laser) transmits through the photomask unit 100 and the projection optical system 15, and forms an image of the photomask on the substrate 17 to be processed (specifically, semiconductor wafer). Image.

At this time, the exposure light source 18 irradiates the illumination area 14 of the photomask unit 100 through the strip-shaped opening 11A of the masking blade 11. On the other hand, as shown by the arrow in FIG. 5, the photomask unit 100 moves in the direction perpendicular to the illumination area 14 with the scanning of the support table (scan stage) 12. As a result, the entire photomask pattern 3 in the photomask unit 100 is irradiated, and the transfer of the photomask pattern is completed.

This scanning type projection exposure is more than the case of the batch type projection exposure in which the entire one chip is exposed in one shot.
It is possible to expand the exposure field, and at the same time, it is possible to effectively use the portion of the lens with less aberration. Therefore,
This is an important method for forming a finer resist pattern.

However, in this scanning type projection exposure, the photomask unit 100 is directly scanned in the exposure apparatus. This scanning speed is usually about 1 to 2 m / sec. Therefore, as shown in FIG. 6, when the photomask unit 100 is not perfectly horizontal to the scanning direction during scanning, wind pressure is applied to the pellicle film 2 and the pellicle film 2 is distorted by this. Become. Further, due to the distortion of the pellicle film 2, the pressure of the internal gas in the space 8 changes, and this change in pressure causes non-uniformity of the refractive index of the exposure light. The distortion of the pellicle film 2 and the non-uniformity of the refractive index of the exposure light in the space 8 cause a problem because the shape of the resist pattern formed by projection exposure varies.

On the other hand, as the design rules of semiconductor integrated circuit patterns have become finer in recent years, the exposure wavelength has become shorter. The light source of the exposure apparatus for circuit pattern transfer, which is currently the mainstream, is a KrF excimer laser with a wavelength of 248 nm, followed by an ArF excimer laser with a wavelength of 193 nm. Next to the excimer laser is a vacuum ultraviolet F2 laser (wavelength 157 nm).

By the way, a laser having a short wavelength of 193 nm or later is absorbed by oxygen and moisture in the atmosphere. Therefore, it is necessary to purge with an inert gas such as nitrogen during projection exposure. Further, since it is necessary to avoid the adhesion of foreign matter on the photomask substrate, the pellicle is indispensable. However, the pellicle film, especially the pellicle film made of an organic polymer, has a thin film thickness of 600 to 1000 nm, and has very low light resistance to irradiation with a high-energy laser such as a laser beam having a short wavelength, and thus has a short life.

In order to solve such a problem that the pellicle film has a short life, in the invention of the prior application of the present invention, the space in contact with the pellicle film is filled with an active gas, usually a gas containing only an inert gas such as nitrogen. A method of mixing and purging was proposed.

Specifically, as shown in FIG. 7, at the time of exposure using a photomask having a pellicle film 2, the photomask is surrounded by a housing 5 and a predetermined amount of active gas is added to the inert gas. A method has been proposed in which a photomask housing device in which the inside 5C of the housing is purged by using a mixed purge gas is loaded into a projection exposure device to perform projection exposure.

However, this method is mainly intended for collective projection exposure with the housing 5 fixed, and does not necessarily take advantage of the above-mentioned scanning projection exposure.

Further, in the invention of the prior application, there has been proposed a method in which the space 8 of the photomask unit 100 is purged by using the above-mentioned purge gas and is mounted in the projection exposure apparatus to perform the projection exposure.

However, this method cannot suppress the variation in the shape of the resist pattern due to the above-described distortion of the pellicle film 2 and the accompanying pressure change in the space 8.

Further, in the case of this method using an inert gas in which a predetermined amount of active gas is mixed as the purge gas,
In order to suppress a change in illuminance due to absorption of exposure light of the active gas, it is necessary to keep the concentration of the active gas constant. But,
It is difficult to perform scanning while keeping the concentration of the active gas constant due to the generation of outgas from the components of the driving means when scanning the support base (scan stage) 12.

[0015]

The present invention solves the problem of short life of the pellicle film described above, and at the same time, changes in the refractive index due to deformation of the pellicle film and accompanying changes in pressure during scanning projection exposure. To suppress variations in the shape of the resist pattern.

Furthermore, the present invention is intended to suppress the change in the concentration of the active gas due to the outgas generated from the driving parts for scanning and the like, thereby suppressing the change in the illuminance at the time of projection exposure. .

[0017]

A photomask storage device according to the present invention comprises a housing whose opposing two plates are made of a light-transmissive material, and a photomask inside the housing. of the retainer to accommodate so as to face the plate, and a driving means for scanning said housing, said driving means
Is an engaging piece fixed to the outside of the housing, and the engaging piece
And an engaging portion that engages with and causes the engaging piece to scan .

Further, in the photomask storage device of the present invention, the opposing two-sided plate is made of a light-transmissive material, and the photomask is opposed to the two-sided plate in the casing. a housing for fixing tool for to, in the flood shadow exposure apparatus, and has a engaging piece that engages a drive means for scanning said housing.

Further, the photomask storage device of the present invention has an adjusting means for adjusting the position and the inclination of the photomask in the housing.

Further, in the photomask storage device of the present invention, the housing has an opening / closing mechanism for replacing the photomask.

Further, in the photomask accommodating device of the present invention, the two opposing plates are arranged at an interval of 3 cm or less.

Further, in the photomask storage device of the present invention, the two opposing plates are made of calcium fluoride, barium fluoride, or fluorine-containing synthetic quartz, and are coated to suppress reflection. There is something.

Next, the projection exposure apparatus of the present invention includes an exposure light source, an optical system for irradiating the exposed surface of the substrate to be exposed with light emitted from the exposure light source and transmitted through the photomask, and a photomask in the housing. It has a drive means for mounting and scanning the photomask housing device housing therein.

Further, the projection exposure apparatus of the present invention has an engagement portion for engaging with the photomask storage device, and at this engagement portion, the photomask storage device is engaged with the photomask storage device. The storage device is scanned.

A projection exposure apparatus according to the present invention is the projection exposure apparatus according to claim 12, wherein the photomask storage device according to any one of claims 6 to 10 is mounted as the photomask storage device. Is.

A projection exposure apparatus having an exposure light source and an optical system for irradiating the exposed surface of a substrate to be exposed with light emitted from the exposure light source and transmitted through a photomask, wherein the projection exposure apparatus comprises: The photomask storage device described in 1. is attached.

Further, the projection exposure apparatus of the present invention is provided with an interferometer for detecting the position of the casing in the projection exposure apparatus.

Next, the projection exposure method of the present invention comprises an exposure light source, a housing containing a photomask therein, and a projection optical system, and a mask pattern of the photomask is formed by light from the exposure light source. In the method of irradiating and projecting the image of the mask pattern on the exposed surface of the substrate to be processed by the projection optical system, the photomask is scanned together with the housing to perform projection exposure.

In the projection exposure method of the present invention, projection exposure is performed while filling the inside of the casing with an inert gas containing an active gas.

Further, in the projection exposure method of the present invention, the active gas is any one of oxygen, ozone, carbon dioxide, carbon monoxide, nitric oxides or oxygen sulfurs, or an organic gas containing oxygen. is there.

In the projection exposure method of the present invention, the inert gas is nitrogen, helium or argon.

Further, the projection exposure method of the present invention is performed while scanning the casing while detecting the position of the casing that has been scanned.

Furthermore, the semiconductor device of the present invention is manufactured by using the projection exposure method according to any one of claims 16 to 20.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and the description thereof will be simplified or omitted.

FIG. 1 is a sectional view showing the structure of a photomask housing device which houses the photomask unit used in the embodiment of the present invention, and FIG. 2 shows the structure of a projection exposure system according to this embodiment. A sectional view and FIG. 3 are perspective views showing the concept of the driving means 9 for scanning the photomask housing device according to this embodiment. In FIG. 1, 1 is a photomask substrate, 2 is a pellicle film, 3 is a photomask pattern, 4 is a frame (or a beam), 8 is a space and a gas filled in this space. A mask pattern 3 is formed on one surface of the photomask substrate 1, and the mask pattern 3 and the mask pattern 3 have a predetermined distance (generally, about 6 m).
m), the pellicle membrane 2 is placed in parallel with the frame 4 almost in parallel.
And protects the photomask pattern 3. A closed space 8 is formed by the photomask substrate 1, the pellicle film 2 and the frame 4, and the space 8 is filled with a purge gas made of an inert gas mixed with a predetermined amount of the active gas. The photomask unit 100 is configured to include the photomask substrate 1, the pellicle film 2, the photomask pattern 3, the frame 4, and the space 8.

Generally, a fluorine-based polymer or the like is used as the material of the pellicle film 2, and aluminum or the like is used as the material of the frame 4. However, it is not limited to this within the scope of the present invention.

Reference numeral 5 is a housing for accommodating the photomask, and 5A and 5B are two opposing plates of the housing 5, which are an upper surface plate and a lower surface plate, respectively. The upper plate 5A and the lower plate 5B are made of a light transmissive material, and the distance between the two surfaces is preferably 3 cm. The distance between the upper surface plate 5A and the lower surface plate 5B is preferably 3 cm or less in order to avoid a decrease in exposure rate due to absorption of exposure light by the active gas. However, it is not limited to this within the scope of the present invention. Further, as the light-transmitting material used for the two-sided plate, calcium fluoride, barium fluoride, or fluorine-added synthetic quartz is suitable, and a coating for suppressing reflection may be applied. It is not limited to this.

Reference numeral 6 is a fixing tool for fixing the photomask housed in the inside 5C, and in this embodiment also has a function as an adjusting means. The photomask is adjusted and fixed by a fixing tool (adjusting means) 6 inside the housing 5C so as to be substantially parallel to the upper plate 5A and the lower plate 5B. As the adjusting means 6, for example, a piezo element or the like may be used. Also, this housing 5
Has, for example, an opening / closing mechanism (not shown) such as a window that can be opened and closed on the side surface, whereby the photomask can be freely attached to and detached from the fixing tool (adjusting means) 6. .

Reference numeral 9A indicates an engaging piece of the driving means 9 for scanning the housing 5. The engagement piece 9A has a concave shape, and the housing 5
Is fixed to the outside of. Further, 9B is an engaging portion for engaging the engaging piece 9A and scanning the engaging piece 9A. The engaging portion 9B has a plate shape with a convex cross section. The driving means 9 is configured by including the engaging piece 9A and the engaging portion 9B which are engaged with each other. Further, in FIG. 3, 10A indicates a reflector (mirror) provided on two side surfaces of the housing, and 10B indicates a light emitting source 1.
0C indicates a light receiver. The light emitted from 10B is configured to be reflected by the reflection plate 10A and enter the light receiver. Reflector 10A, light emitting source 10B, and light receiver 10C
The interferometer 10 is configured to include.

Further, 7A is a gas supply port, and 7B is a gas recovery port. The inside 5C of the housing is filled with a purge gas consisting of an inert gas mixed with a predetermined amount of active gas through the gas supply port 7A, and this purge gas is recovered through the gas recovery port 7B.

The photomask accommodating apparatus 200 is constituted by including the housing 5, the fixing tool (adjusting means) 6, the driving means 9, the gas supply port 7A and the gas recovery port 7B.

In this embodiment, a photomask having a pellicle film is provided with a photomask unit, a fixing tool (adjusting means), a driving means, and the like, and a housing capable of accommodating the photomask unit is provided inside. It will be referred to as a photomask storage device.

In FIG. 2, 10 is an exposure light source, 11 is a masking blade, 15 is a projection optical system, and 16 is a table (wafer scan stage) on which a substrate 17 to be processed is placed. The projection exposure apparatus is also equipped with a photomask housing device 200 housing a photomass unit 100 as a photomask. The substrate 17 to be processed is
For example, it is a semiconductor wafer, and the exposure light source 18 is, for example, F2.
It is a laser.

Next, the operations of the projection exposure apparatus and the photomask housing apparatus when performing projection exposure using this projection exposure apparatus will be described.

As shown in FIG. 2, the photomask storage device 200 is mounted in the exposure device. In addition, as shown in FIG. 1, the photomask unit 100 confirms that there is no large foreign matter transferred to the substrate 17 to be processed on the glass surface of the photomask substrate 1 and the pellicle film 2, and then the housing 5
From the opening / closing mechanism (not shown) of the photo mask storage device 2
It is accommodated in 00. The photomask unit 100 is
The top plate 5A of the housing 5 is adjusted by the adjusting means (fixing tool) 6.
The position and inclination in the inside 5C are adjusted so as to be substantially parallel to the bottom plate 5B, and then fixed to the fixing tool (adjusting means) 6.

As shown by the arrow in FIG. 2, the exposure light (specifically, the F2 laser light) emitted from the exposure light source 18 enters the projection optical system 15 through the photomask housing device 200, and this projection optical system. The light is converged at 15, and the exposed surface of the surface of the substrate 17 to be processed is exposed.

In FIG. 3, 11A indicates an opening of the masking blade, and 14 indicates an irradiation region for the photomask housing device. Further, the arrow indicates the scanning direction of the photomask storage device, and this direction is a direction perpendicular to the irradiation region 14.

During the exposure, the exposure light from the exposure light source 18
Irradiation of the photomask storage device 200 is limited to the strip-shaped irradiation region 14 narrowed through the opening 11A of the masking blade 11. The concave engagement piece 9A meshes with the convex engagement portion 9B and scans over the convex engagement portion 9B in the direction of the arrow. Along with this, the photomask storage device 200 scans in the direction (arrow direction) perpendicular to the irradiation region 14. As a result, the entire mask pattern 3 of the photomask unit 100 fixed inside the housing 5C is irradiated, and the mask pattern is transferred to the substrate 17 to be processed. Further, during scanning, the light emitted from the light emitting source 10B is
The light is reflected by the reflection plate (mirror 10A) provided in the housing 9, and the reflected light is incident on the receiver 10C. By measuring this incident light, the photomask storage device 20
The position of 0 can be detected.

In this embodiment, the driving means 9 is
The photomask storage device 200 is provided with the photomask storage device 200. However, the exposure device is not limited to this. It may be one. Further, as the means for driving the engagement piece 9A by the driving means 9, for example, the force of the linear motor may be used, but the driving means 9 is not limited to this, and may be driven by other means.

In this embodiment, the interferometer 10 scans while detecting the position of the photomask storage device 200, but it does not have to have such means. In addition, in this embodiment, the inside of the housing 5
To C, through the gas supply port 7A and the gas recovery port 7B,
The purge gas described above is circulated. This is to exhaust the outgas generated from the pellicle or the like. However, the photomask housing device 200 does not have the gas supply port 7A and the gas recovery port 7B, and after the interior 5C of the housing is filled with the above-mentioned purge gas, projection exposure is performed with the housing 5 sealed. Good.

The space 8 of the photomask unit 100
The reason why the inside of the housing 5C is purged with a purge gas composed of an inert gas mixed with an active gas is to extend the life of the pellicle film 2, particularly the pellicle film of an organic material.

The concentration of the active gas to be mixed is 5
A range of 0 ppm to 10000 ppm is suitable. The higher the concentration of the active gas, the longer the life of the pellicle film, but the higher the concentration, the more the light transmission amount tends to decrease. Therefore, an appropriate concentration can be selected as needed. The range in which the life of the pellicle film is compatible with the light transmittance is the above range.

As the inert gas described above, any of nitrogen, argon and helium is suitable, but the inert gas is not necessarily limited to these. Also,
The active gas to be mixed with this inert gas is preferably selected from oxygen, ozone, carbon dioxide, carbon monoxide, nitrogen oxides, sulfur oxides, or an organic gas containing oxygen. However, it is not necessarily limited to these.

[0054]

As described above, in the present invention, the photomask is fixed inside the housing, and the entire housing is scanned during projection exposure. Therefore, it is possible to suppress the outgas generated from the drive component for scanning the photomask, and thereby suppress the change in illuminance during the exposure of the substrate to be processed.

Further, the pellicle film is not directly subjected to wind pressure due to the scanning of the photomask. Therefore, the deformation of the pellicle film can be prevented. At the same time, it is possible to prevent the pressure change in the space between the photomask substrate, the pellicle film, and the frame caused by the deformation of the pellicle film, and to prevent the uneven refractive index of the exposure light due to the pressure change. . By preventing the deformation of the pellicle film and the non-uniformity of the refractive index of the exposure light, it is possible to suppress the variation in the shape of the resist pattern formed on the substrate to be processed by projection exposure.

Further, since the inside of this casing is purged with an inert gas containing a predetermined amount of active gas, the pellicle film can be made longer-lived.

As described above, the present invention solves the problem that the pellicle film has a short life, and at the same time, makes use of the advantages of the scanning type exposure apparatus and solves the problem of variation in the shape of the resist pattern caused by deformation of the pellicle film. Therefore, the projection exposure of a fine pattern can be realized more reliably and faithfully.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the structure of a photomask housing device housing a photomask unit used in an embodiment of the present invention.

FIG. 2 is a sectional view showing a structure of a projection exposure apparatus used in the embodiment of the present invention.

FIG. 3 is a perspective view showing the concept of driving means of the projection exposure apparatus in the embodiment of the present invention.

FIG. 4 is a perspective view showing a structure of a conventional scanning exposure apparatus.

FIG. 5 is a sectional view showing a structure of a conventional photomask unit.

FIG. 6 is a cross-sectional view showing the concept of a state of a conventional photomask unit during scanning.

FIG. 7 is a diagram showing a structure of a projection exposure apparatus according to the invention of the prior application.

[Explanation of symbols]

100 photomask unit, 200 photomask storage device, 1 photomask substrate, 2 pellicle film, 3 mask pattern, 4 frame, 5 housing, 5A top plate, 5B bottom plate, 5C interior, 6 fixing tool (adjusting means), 7A gas supply port, 7B gas recovery port, 8 space, 9 driving means, 9A engaging piece, 9B engaging part, 10 interferometer, 10A reflecting plate (mirror), 10B light emitting source, 10
C light receiver, 11 masking blade, 12 scan stage, 14 illumination region, 15 projection optical system, 16 table for placing substrate to be processed (wafer scan stage), 17 substrate to be processed (wafer), 18 exposure light source (F2 laser).

Front page continued (58) Fields surveyed (Int.Cl. ⁷ , DB name) G03F 1/00-1/16 G03F ⁷ /20-7/24 G03F 9/00-9/02 H01L 21/027

Claims (20)

(57) [Claims] 1. A housing whose opposing two-sided plates are made of a light-transmissive material, and a fixing tool for accommodating a photomask inside the housing so as to face the two-sided plates. When the driving means for scanning the housing, wherein the drive means, said housing externally secured the engagement piece of the
And an engagement portion that engages with the engagement piece to scan the engagement piece
Photo mask storage device characterized by including, when. 2. The photomask storage device according to claim 1, further comprising adjusting means for adjusting a position and an inclination in which the photomask is stored in the housing. 3. The housing has an opening / closing mechanism for replacing the photomask.
Alternatively, the photomask storage device according to item 2. 4. The photomask storage device according to claim 1, wherein the two opposing plates are arranged at an interval of 3 cm or less. 5. The two opposing plates are made of calcium fluoride, barium fluoride, or fluorine-doped synthetic quartz, and are coated to suppress reflection. 5. The photomask storage device according to any one of 4 to 4. 6. A housing, the two facing plates of which are made of a light-transmissive material, and a fixing tool for housing a photomask in the housing so as to face the two facing plates. And a photomask accommodating apparatus having an engagement piece that engages with a drive unit that scans the housing in the projection exposure apparatus. 7. The photomask storage device according to claim 6, further comprising adjustment means for adjusting a position and an inclination in which the photomask is stored in the housing. 8. The housing has an opening / closing mechanism for replacing the photomask.
Alternatively, the photomask storage device according to item 7. 9. The photomask storage device according to claim 6, wherein the two opposing plates are arranged at an interval of 3 cm or less. 10. The two opposing plates are made of calcium fluoride, barium fluoride, or fluorine-doped synthetic quartz, and are coated to suppress reflection. 10. The photomask storage device according to any one of 9 to 9. 11. An exposure light source, an optical system for irradiating the exposed surface of a substrate to be processed with light emitted from the exposure light source and transmitted through a photomask, and a photomask housing device housing a photomask in a housing. A projection exposure apparatus having a driving means for scanning. 12. The drive means has an engagement portion for engaging with the photomask storage device, wherein the photomask storage device is engaged with the engagement portion. The projection exposure apparatus according to claim 11 , which scans. 13. The projection exposure apparatus according to claim 12, wherein the photomask storage device according to claim 6 is mounted as the photomask storage device. 14. A projection exposure apparatus, comprising: an exposure light source; and an optical system that irradiates the exposed surface of a substrate to be processed with light emitted from the exposure light source and transmitted through a photomask. A projection exposure apparatus comprising the photomask storage device according to any one of the claims. 15. The projection exposure apparatus according to claim 11, further comprising an interferometer for detecting the position of the housing in the projection exposure apparatus. 16. An image of the mask pattern, comprising: an exposure light source; a housing containing a photomask therein; and a projection optical system, wherein light from the exposure light source illuminates the mask pattern of the photomask. In the method of performing projection exposure on the surface to be exposed of a substrate to be processed by the projection optical system, wherein the photomask is scanned together with the housing to perform projection exposure. 17. The projection exposure method according to claim 16, wherein projection exposure is performed while filling the inside of the housing with an inert gas containing an active gas. 18. The active gas is any one of oxygen, ozone, carbon dioxide, carbon monoxide, nitric oxides, oxygen sulfurs, or an organic gas containing oxygen. Projection exposure method. 19. The inert gas is nitrogen, helium,
19. The projection exposure method according to claim 17, wherein the projection exposure method is argon. 20. The projection exposure method according to claim 16, wherein the scanning is performed while detecting the position of the scanned housing.