JP2000098112A - Production of multiple light source forming reflection mirror and optical device using this reflection mirror - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily form a basic reflection surface having a surface shape of high accuracy by pressing a surface to be worked of a workpiece by a pressing means having the compressive strength higher than the compressive strength of the surface to be worked and having a prescribed shape at its front end to plastically deform this surface in such a manner that the basic reflection surface has a prescribed curvilinear surface shape. SOLUTION: The workpiece 310 is installed on a work table 325 and the pressing means 326 is arranged in the upper part of the workpiece 310. Brass is used for the workpiece 310. The pressing means 326 is connected to a drive assembly 327. The pressing means 326 worked at its front end to the prescribed reversal shape is controlled in its position with respect to the workpiece 310 on the work table 325 by a control means 328. After the pressing means 326 is positioned to the prescribed position, the pressing means presses the workpiece while a descending quantity is controlled, by which the prescribed surface shape is formed on the surface. Namely, the prescribed optical surface shape is formed in the arbitrary position on the workpiece 310 by the control of the position of the pressing means 326 and the control of the pressing quantity of the pressing means 326.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a reflecting mirror and a semiconductor manufacturing apparatus, and more particularly to a method for manufacturing a reflecting mirror having a reflecting surface constituted by a repetitive arrangement of minute basic reflecting surfaces. The present invention relates to a reflective illumination device, and further relates to a semiconductor exposure apparatus using the illumination device.

[0002]

2. Description of the Related Art At present, in the manufacture of semiconductor devices such as DRAMs and MCPs, development research for narrowing the minimum line width is actively conducted, and the design rule is 0.13 μm.
(4G DRAM equivalent), 0.1μm (16G DRA
M), and various technologies have been developed for realizing 0.07 μm (corresponding to 32G DRAM). Having an inseparable relationship with this problem of minimum line width,
It is a light diffraction phenomenon that occurs at the time of exposure, and due to this,
This is the biggest problem when realizing the minimum line width that requires blurring of the image and the focal point. In order to suppress the influence of this diffraction phenomenon, it is necessary to increase the numerical aperture (NA) of the exposure optical system, and the point of development is to increase the diameter of the optical system and shorten the wavelength. However, when the wavelength of light is shortened, particularly when the wavelength is 200 nm or less, optical materials that are easy to process and have low light absorption are not found. Therefore, a projection optical system using a reflection optical system has been developed by abandoning the transmission optical system, and has achieved considerable results. Among them, a combination of a plurality of reflecting mirrors realizes an arc-shaped optical field of view (area that can be used as an exposure area) for soft X-rays, and synchronizes the mask and wafer with each other at the relative speed of the projection reduction ratio. There is a method in which the entire chip is exposed by moving the chip. (For example, Koi
chiro Hoh and Hiroshi Tanino; “Feasibility Study
on the Extreme UV / Soft X-ray Projection-type Lith
ography ”, Bulletin of the Electrontechnical Labor
atory Vol. 49, No. 12, p. 983-990, 1985: hereinafter referred to as reference document 1). Incidentally, along with the minimum line width, a so-called throughput is an important factor for the semiconductor device manufacturing as described above. Factors involved in this throughput include the light emission intensity of the light source, the efficiency of the illumination system, the reflectance of the reflector used in the reflection system, and the sensitivity of the photosensitive material / resist on the wafer. At present, as a light source, an ArF laser, an F2 laser, and synchrotron radiation light and laser plasma light have been developed as short-wavelength light sources. Is also carried out at a rapid pace, close to the level of practical use (for details, refer to the above-mentioned reference 1, and Andr
ew M. Hawryluk et al; “Soft x-ray beamsplittersan
d highly dispersive multilayer mirrors for use as
soft x-ray laser cavity component ”, SPIE Vol. 688
Multilayer Structure and Laboratory X-ray Laser
Research (1986) P.81-90 and JP-A-63-312
640: hereinafter referred to as reference document 2). Now, regarding the technical development of the illumination system, the required technology for realizing uniform illumination and numerical aperture is disclosed in, for example, Japanese Patent Application Laid-Open No. Sho 60-2.
Japanese Patent Publication No. 32552 proposes a technique for a rectangular illumination area. However, when the field of view of the projection optical system is on a circular arc as in the above-described projection system, if the illumination field of view has a rectangular shape, the light use efficiency is poor, and the exposure time cannot be reduced inevitably, so that the throughput has not increased. Recently, as a method of solving this problem, a method of setting an illumination field in accordance with the optical field of the projection optical system, thereby increasing illumination efficiency and solving the problem of throughput has been proposed in Japanese Patent Application No. 10-047400. ing. Fig. 4
This will be briefly described based on the above. FIG. 4 is a schematic view of a projection exposure apparatus. Light emitted from a light source 1 passes through a proposed multi-source forming reflecting mirror 2, a condenser optical element 3, and a reflecting mirror 4, and a mask 5 held on a mask stage 5s. To illuminate.
On the mask 5, a pattern to be drawn on the wafer held on the wafer stage 7s is formed as a reflector figure. The pattern on the mask is illuminated by reflective illumination optics consisting of 2, 3 and 4, 6a, 6b, 6c, 6
The light is projected onto the wafer 7 through the projection optical device 6 made of d. At this time, the optical field of view of the projection optical device is not wide enough to cover the entire device chip to be manufactured, and the exposure is performed while the mask 5 and the wafer 7 are relatively moved (scanned) in synchronization with each other to perform patterning on the entire chip. Is formed on a wafer. For this purpose, a mask stage controller 8 including a laser interferometer and a wafer stage controller 9 for controlling the amount of movement of the stage are provided. (Refer to the above-mentioned reference 1 for the exposure method involving this scan.) The point in this case is that the multiple light source forming reflecting mirror 2 constitutes a reflecting mirror by repeating arrangement of one or a plurality of minute basic reflecting surfaces, and the outer shape of the basic reflecting surface is defined by the optical field shape of the projection optical device. It is to make it similar. As a result, a large number of point light source images I are formed at the position P2 in a substantially circular shape, which forms the required illumination field by the condenser optical element. By using the above-described technique, a region to be illuminated on a mask can be uniformly illuminated without waste, the exposure time can be reduced, and a semiconductor exposure apparatus having high throughput can be realized.

[0003]

FIGS. 5 and 6 show the results of actually designing a multiple light source forming reflector for a reflection type illumination optical device having an arc-shaped illumination field as described above and its basic reflecting surface. This will be described with reference to FIG. As shown in FIG. 5A, this multi-light source forming mirror has three types of basic reflecting surfaces (A1, B1, and B1).
C1). That is, in each row of the multiple light source forming reflecting mirror of FIG. 5A, each basic reflecting surface has A1, B1,.
Are arranged in the order of C1,. 6 (a), (b),
(C) shows the shape of each basic reflection surface. As shown in these figures, each basic reflecting surface has a concave spherical surface 41 having a radius of curvature R.
5 (b), an arc-shaped band parallel to the YZ plane (an arc-shaped band of a circle having an average radius of Zh) is projected. At this time, the projected image when the center of the projected arc is aligned with the center axis of the spherical surface is A1, and the projected image when the center of the circular arc is shifted by Yh perpendicular to the axis of the spherical surface is B.
1, C1. This projected image shape is cut out and used as a basic reflecting surface. Each of them has a substantially arc shape. At least X
When viewed from the direction, the shape is a perfect arc. And B1, C1
Are respectively translated in the Y-axis direction and combined with A1. For example, when a parallel ray is incident on the reflecting mirror formed in this way from the X direction, the point image by A1 is shifted to the focal point of the spherical surface 41, and the point image by B1 is shifted by Yh from the focal point.
A point image by C1 is formed so as to be laterally shifted by −Yh from the focal point. Here, for example, as a suitable practical design solution of the basic reflecting surface, the radius of curvature R of the concave spherical surface is 160 to 200.
mm and Zh are 4.5 to 5.5 mm, the width of the arc (the width of the arc-shaped band) is 0.3 to 2 mm, and the length of the arc is 4.5 to 5.5.
mm and Yh are about 2.3 to 2.7 mm, and the surface roughness is Rrms <0.3 nm.

Incidentally, the above-mentioned reflecting mirror is usually manufactured by cutting using a cutting machine equipped with a ball end mill. The ball end mill has a shape as shown in FIG. 7 (a). By controlling the position of the ball end mill three-dimensionally with respect to the workpiece, it is possible to process various surfaces as shown in FIG. 7 (b). is there. But in fact, as a metal material,
Using aluminum to process the basic reflective surfaces one by one,
When actually illuminating using the completed multi-light source forming reflector, a multi-light source forming reflector having the expected good efficiency was not obtained, and therefore a semiconductor exposure apparatus with high throughput was not obtained. Therefore, when the cause was investigated, as shown in FIG. 13, the respective basic reflection surfaces 51 were adjacent to each other, and there was an unprocessed portion in a valley portion.
The effect of this part was found to be major. This processing residue is caused by the shaft radius of the ball end mill,
This is the CR section in the figure. Considering that the minimum value of the shaft radius of the ball end mill is about 0.5 mm, it has been found that the problem is unavoidable if such cutting is performed. Further, in the processing method, even if the processing of one basic reflection surface fails during the processing process, a new workpiece has to be prepared and then processed again from the beginning. As a result, high processing efficiency could not be obtained.

[0005] Also, as a material such as aluminum,
A method of processing a metal material that is easy to cut into a predetermined concave spherical surface using an NC cutting machine and cutting out a predetermined arc-shaped reflective element element from the spherical surface using a wire electric discharge machine is also conceivable. It takes time and the processing cost becomes enormous. Therefore, the present invention has been devised to solve such a problem, and a first object of the present invention is to provide a manufacturing method capable of manufacturing a multi-light source forming reflecting mirror having a reflecting surface shape as designed at a high yield. Furthermore, the second is to obtain a semiconductor exposure apparatus with higher throughput.
For the purpose.

[0006]

In order to achieve the above object, according to the present invention, as a first means, a multi-source light source is provided in which a basic reflecting surface having a part of a predetermined curved surface is repeatedly arranged. When manufacturing a formed reflector, a metal serving as a base material of the multi-source formed reflector is prepared as a workpiece, the compressive strength is higher than the processed surface of the workpiece, and the tip has a predetermined shape. The surface to be processed is pressed and plastically deformed by the pressing means, so that the basic reflecting surface has a predetermined curved shape. Thereby, a basic reflecting surface having a highly accurate surface shape can be easily formed. In the first aspect, the fact that the tip has a predetermined shape means that the tip has a shape inverted from the curved shape of the basic reflection surface, that is, a male shape.

As a second means, when the first means is carried out, at least one of the work surface or the pressing means is moved, the pressing by the pressing means and the plastic deformation are performed at the moving position, and further, By repeating the movement, the pressing and the plastic deformation, a large number of basic reflection surfaces are formed on the surface to be processed. This makes it possible to easily form a basic reflecting surface having a highly accurate surface shape at a predetermined position.

As a third means, a reflection type illumination device comprising a plurality of reflecting mirrors is provided with a multiple light source forming reflecting mirror manufactured by the above first or second means. As a result, the light use efficiency of the reflective illumination device is improved, and the cost is reduced. As a fourth means, a light source, a mask stage that holds and moves a mask, an illumination device that illuminates the mask, a projection optical device that projects a pattern on the mask onto a wafer, and a wafer that holds and moves the wafer The reflection type illumination device obtained by the third means is used in a semiconductor exposure apparatus having a stage, and the basic reflection surface of the multiple light source forming reflector of the reflection type illumination device is similar to the optical field of the projection optical device. Shape. As a result, the optical field of the illumination system and that of the projection system can be matched as an exposure apparatus. Therefore, a semiconductor exposure apparatus having high light use efficiency and high throughput can be obtained.

As a fifth means, as the semiconductor exposure apparatus obtained by the fourth means, a projection optical apparatus uses a reflection type projection optical apparatus comprising a plurality of reflecting mirrors, and the optical field of view of the projection optical apparatus is an arc. I did it. This gives 157
A semiconductor exposure apparatus using an F2 laser or a soft X-ray having a wavelength of nm can be obtained. The use of the arc-shaped projection system visual field is based on the fact that a wide visual field can be obtained with a small number of reflecting mirrors.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The basic idea of the present invention is that, in a processing method in which each basic reflecting surface is in point contact with a workpiece or mechanical contact in a minute area, an unprocessable area is formed. It is based on the recognition that it takes a huge amount of time even if the entire surface can be processed, and that there is a large variation in the processing.One mold is pressed against the base, and the base is plastically deformed. A method is used in which a reflective surface is formed and precise surface accuracy can be manufactured with good reproducibility.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view of the present invention, in which a workpiece 310 is set on a work table (working table) 325, and a pressing means 326 is arranged above the workpiece. The pressing means 326 is connected to the driving device 327. The control device 328 is connected to the work table 325 and the pressing means 326. The tip 329 of the pressing means 326 is made of tool steel or super steel (W
C). Further, the tip 329 of the pressing means
Is the inverted shape of the basic reflection surface of the multiple light source forming reflector (here, when pressed against a plastically deformable material, the shape of the pressing member side is changed so that the surface shape of the plastically deformable material becomes a desired shape. (Referred to as inverted shape or male shape). In the case of tool steel, in the case of tool steel, after shaping the approximate shape with a milling cutter or the like, quenching is performed, and a predetermined surface shape is created by electric discharge machining or grinding. Subsequently, the shape is refined and mirror-finished by polishing. In the case of super steel, a shape is created by grinding and electric discharge machining, and further polishing is performed to achieve high precision and a mirror surface. In this way, the control device 328 controls the position of the pressing means 326 whose tip is formed into a predetermined inverted shape with respect to the workpiece on the work table. After the pressing means 326 is positioned at a predetermined position, it is pressed while controlling the amount of descent to form a predetermined surface shape on the surface. That is, by controlling the position of the pressing means and the control of the pressing amount of the pressing means, a predetermined optical surface shape can be formed at an arbitrary position on the workpiece. Further, as shown in FIG. 1, the control device repeatedly moves the work table in the Z or Y direction at a predetermined interval and lowers the pressing means by a predetermined amount, whereby the basic reflecting surface is reduced. The array can be processed.

In addition, the base material that has been plastically deformed when pressed may bulge on the surface and degrade the characteristics as a reflector. At this time, after the processing is completed, the surface is polished to remove unnecessary substances generated during the processing, or at least every other basic reflection surface is formed. Then, the same basic reflecting surface shape or a different basic reflecting surface shape is formed between the already formed basic reflecting surfaces in the same manner. When a more accurate basic reflection surface is required, as shown in FIG. 3, a resin having low adhesive strength is poured into the formed basic reflection surface and fixed thereto. It is effective to form a surface. As this resin, an ultraviolet-curing resin is used, and only a basic reflection surface already formed by selectively exposing a portion where a reflection surface has been formed and a portion not having the reflection surface (for example, 31 in FIG. 3).
5) The resin can be filled. Next, a method of actually processing is described below. The shape of the basic reflecting surface here is, for example, the radius of curvature R of the concave spherical surface to be cut out is 180 mm,
Zh is 5.0 mm, and the width of the arc (the width of the arc-shaped band) is 0.3.
mm, the length of the arc is 5.0 mm, and Yh is about 2.5 mm.

The processing procedure will be described with reference to FIG. 1 again. In the figure, brass is used for the workpiece. Tool steel is used at the tip of the pressing means. FIGS. 2 (a), 2 (b) and 2 (c) show the tip shapes of the pressing means prepared to press and plastically deform the shape of FIG. 1 to create a basic reflecting surface. Each tip shape corresponds to the basic reflecting facets A1, B1, and C1, and is a shape on the male side with respect to A1, B1, and C1. Since the tip material was tool steel, the above-mentioned surface processing was performed by milling using a ball end mill, or by grinding and polishing. In processing the basic surface, first, the pressing means shown in FIG. 2A is attached to the driving device. Next, the workpiece is moved to a predetermined position (11 in FIG. 1) 11 by moving the work table.
The pressing means is lowered to transfer the tip shape of the pressing means to the workpiece. Next, the workpiece is moved 0.9 mm in the Z direction.
Move. The pressing means is lowered to transfer the tip shape of the pressing means to the workpiece. In such a case, the.
The movement of 9 mm and the lowering of the pressing means are repeated. When the processing of the basic reflection surfaces arranged in one line in the Z direction is completed, the workpiece is moved by 5 mm in the Y direction, and thereafter, the movement by 0.9 mm in the Z direction and the lowering of the pressing means are repeated. When the processing in one row is completed, the workpiece is again moved 5 m in the Y direction.
After moving by m, the movement of 0.9 mm in the Z direction and the lowering of the pressing means are repeated. Thus, the shape of FIG. 2A is transferred to the workpiece. Next, the pressing means will be described with reference to FIG.
2 and the position (12 in FIG. 1) adjacent to the shape transferred by the work table in FIG.
The workpiece is moved so that (b) can be transferred. Next, the pressing means is lowered to transfer the tip shape of the pressing means to the workpiece. Next, the workpiece is moved in the Z direction by 0.
Move 9 mm. The pressing means is lowered to transfer the tip shape of the pressing means to the workpiece. Such a movement of 0.9 mm in the Z direction and the lowering of the pressing means are repeated.
Next, after moving the workpiece 5 mm in the Y direction,
The movement of 0.9 mm in the direction and the lowering of the pressing means are repeated. After moving the workpiece 5 mm in the Y direction again,
The movement of 0.9 mm in the Z direction and the lowering of the pressing means are repeated. Thus, the shape of FIG. 2B is transferred to the workpiece. Next, the pressing means is exchanged for FIG. 2 (c), and FIG. 2 (c) can be transferred to a position (13 in FIG. 1) adjacent to the shape transferred on the work table according to FIG. 2 (b). Next, the workpiece is moved. Next, the pressing means is lowered to transfer the tip shape of the pressing means to the workpiece. Next, the workpiece is moved by 0.9 mm in the Z direction. The pressing means is lowered to transfer the tip shape of the pressing means to the workpiece. 0.9mm in the Z direction
And the lowering of the pressing means are repeated. Next, after moving the workpiece 5 mm in the Y direction, the workpiece is moved 0.9 mm in the Z direction.
The movement of mm and the lowering of the pressing means are repeated. After moving the workpiece again by 5 mm in the Y direction, the workpiece is moved in the Z direction by 0.1 mm.
The movement of 9 mm and the lowering of the pressing means are repeated. Thus, the shape of FIG. 2C is transferred to the workpiece. or,
As described above, if necessary, after completion of the transfer of the shape 2 (a), polishing is performed to remove a bulge around the transfer surface caused by plastic deformation, or after completion of the transfer of the entire surface, Perform polishing. As described above, it is possible to process the complicated light source forming reflector shown in FIG.

In order to use the F2 laser as a light source to increase the reflectance of the surface thus processed, an aluminum thin film having a thickness of about 100 nm is formed by vapor deposition. In the same vacuum layer, MgF2 is tens of nm from the viewpoint of preventing oxidation and maintaining the reflectance.
Was formed by vapor deposition. In addition, in order to use light (electromagnetic waves) in the soft X-ray region, a reflecting mirror made of a multilayer film of Si and Mo (see the above-mentioned references 1, 2) was formed.

As described above, in the present embodiment, an example of a method of processing a multi-source light reflecting mirror constituted by element optical elements A1, B1, and C1, which are a part of a spherical surface, has been described. However, the multiple light source forming reflecting mirror that can be processed in the present invention is not limited to this. For example, the number of basic reflection surfaces may be more or less than three. The element optical element may be a part of an aspheric surface.

In order to incorporate the above-mentioned multiple light source forming reflecting mirror into a semiconductor exposure apparatus, it is sufficient to configure it as shown in FIG.

[0017]

As described above, according to the processing method provided by the present invention, an optical element having a complicated shape composed of a large number of basic reflecting surfaces can be manufactured with high precision and high processing efficiency. The optical element obtained by this manufacturing method is suitable for a lighting device for a semiconductor device manufacturing apparatus.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an embodiment of the present invention.

FIG. 2 is a diagram illustrating a pressed shape forming unit according to an embodiment of the present invention.

FIG. 3 is a schematic view of a resin filling method according to an embodiment of the present invention.

FIG. 4 is a projection optical system according to the present invention.

FIG. 5 is a multi-light source forming reflector according to the present invention.

FIG. 6 shows the shape of a basic reflecting surface according to the present invention.

FIG. 7: External shape and processing curved surface of a ball end mill

FIG. 8 is a diagram showing a problem of the conventional method.

[Explanation of symbols]

1 ····· Light source 2 ···· Multiple light source forming reflector 3 ···· Condenser optical system 4 ···· Reflector 5 ···· Mask, 5s ···· Mask Stage 6 Projection optical device 7 Wafer 7 s
Wafer stage 8 Mask stage controller 9 Wafer stage controller 41 Concave spherical surface 51 that cuts out the basic reflection surface 51 Basic reflection surface 310 Workpiece 315 Filling resin 325 Work table 326 Pressing means 327 Driving means 328 Control means 329 Surface shape forming part A1, B1, C1, basic reflection surface

Claims (5)

[Claims] 1. A method of manufacturing a multi-light source forming reflector, comprising: repeatedly arranging a basic reflecting surface having a part of a predetermined curved surface as a surface shape, wherein a metal as a base material of the multi-light source forming mirror is provided. Prepared as a workpiece, the compression strength is higher than the workpiece surface of the workpiece, and the tip portion is pressed by a pressing means having a predetermined shape to plastically deform the workpiece surface, whereby the basic reflection surface Has a predetermined curved surface shape. 2. The method of manufacturing a multi-light source forming reflecting mirror according to claim 1, wherein at least one of the processing surface and the pressing means is provided.
Moving one, performing the pressing and plastic deformation by the pressing means at the moving position, and further sequentially, by repeating the movement, pressing and plastic deformation, forming a number of basic reflection surfaces on the surface to be processed. Processing method of the optical element. 3. A reflection type illumination device comprising a plurality of reflection mirrors, wherein the reflection type illumination device has a multi-light source forming reflection mirror manufactured by the manufacturing method according to claim 1. 4. A light source, a mask stage that holds and moves a mask, an illumination device that illuminates the mask, a projection optical device that projects a pattern on the mask onto a wafer, and a wafer stage that holds and moves the wafer A semiconductor exposure apparatus having the reflective illumination device according to claim 3,
A semiconductor exposure apparatus, wherein a basic reflecting surface of a multiple light source forming reflector of the reflection type illumination device has a shape similar to an optical field of view of the projection optical device. 5. The semiconductor exposure apparatus according to claim 4, wherein
A semiconductor exposure apparatus, wherein the projection optical device is a reflection type projection optical device including a plurality of reflecting mirrors, and an optical field of view of the projection optical device is arc-shaped.