JPS6153646A - Projection optical device - Google Patents

Abstract

PURPOSE:To project only a pattern of an original picture pattern formed body without projecting a pattern of a foreign matter, a flaw of a mask substrate, etc., by executing a projection of an original picture pattern by utilizing a reflected light by a mask. CONSTITUTION:A light from an exposure light source 100 is converted to parallel rays having a uniform illuminance distribution of a monochrome by an illuminating optical system 110, and made incident on a half prism 10 from the right. As for this illuminating light, its optical path is changed in the upper direction by the half prism 10, and it is made incident on a mask 12 from a glass surface side. A part of the incident illuminating light is reflected by a pattern formed body 16, and this reflected light is made incident on a projection optical system 116 through the half prism 10. Subsequently, a pattern 120 of the pattern formed body 16 on the surface to be transferred of a wafer 118 is brought to image formation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a projection optical device for projecting a predetermined pattern, which is used, for example, in semiconductor wafer printing equipment in semiconductor manufacturing.

[Background of the invention]

A conventional projection optical device uses a mask or reticle (hereinafter simply referred to as a "mask") on which a predetermined pattern is formed.
Utilizing the light that passes through the water (7 items appear).

As a mask, use a light-transmitting substrate such as glass.
A material with the necessary pattern formed using a shiny material such as chromium is used. When light is irradiated from one side of this mask from an appropriate light source, the light is transmitted to the other side except for the patterned portion. This transmitted light enters a predetermined projection optical system, and further a pattern is projected onto a predetermined wafer.

By the way, in the projection optical device as described above, if there is dust, fingerprints, scratches, etc. that block the light on the portion of the mask substrate where the light should be transmitted, these will block the light that should be transmitted. Therefore, the dust and the like are also projected.

This will adversely affect the original pattern that should be projected. Therefore, defects in elements or circuits formed on the semiconductor wafer are caused, and production efficiency is reduced.

[Purpose of the invention]

The present invention has been made in view of the above points, and an object thereof is to provide a projection optical device that can improve the drawbacks of the above-mentioned background art and reduce the occurrence of defects in projection patterns due to dust, etc. It is something.

[Summary of the Invention] According to the present invention, reflected light rather than transmitted light from a mask substrate is used to project a pattern. Sunlight light source (100
), an illumination optical system (110), a half prism αQ), and a light guide means (half prism Qd) for introducing the illumination light reflected by the mask substrate into the projection optical system (11,'l). There is.

〔Example〕

Hereinafter, a projection optical device according to the present invention will be described in detail based on embodiments shown in the accompanying drawings.

FIG. 1 is an explanatory diagram showing the basic principle of the present invention.
First, the basic principle will be explained based on this diagram. In Figure 1, a mirror prism (hereinafter simply "
)--7 prism-1)10KI-m, illumination light enters from the right side of the figure as indicated by the arrow FA. A mask 12 is arranged above the half prism 10, and an arrow F
Illumination light emitted from a person as shown in A is bent toward the mask 12 by the action of the half prism 100, and enters the mask 12.

The mask 12 is configured to form a predetermined pattern on, for example, a glass substrate 14 having a flat surface. □1' A photosensitive material (hereinafter simply referred to as "pattern forming body") 16 such as ROM is deposited by vacuum evaporation or the like. It is provided by the following method. It is assumed that foreign matter 18 is attached to a portion of the glass substrate 14 through which light passes. The illumination light is the mask 12
The light enters from the opposite side of the glass substrate 14, that is, the glass surface where the pattern forming body 16 is not provided.

Of the illumination light that is incident on the glass substrate 14, the light that is incident on portions other than the pattern forming body 16 or the foreign matter 18 is almost transmitted as shown by the arrow FB. Next, the light incident on the pattern forming body 16 is specularly reflected because the incident surface is flat and a metal such as chromium is provided on the flat surface by vacuum evaporation, etc. It follows the optical path opposite to the incident light. This reflected light passes through the S-7 prism 10.

On the other hand, most of the illumination light incident on the foreign object 18 is scattered as shown by the arrow FD.

Therefore, reflected light corresponding to the pattern shape of the pattern forming body 16 mainly enters the projection optical system (not shown). That is, the pattern of light incident on the projection optical system includes a region 20 corresponding to transmitted light indicated by arrow F13, a region 22 corresponding to reflected light indicated by arrow FC,
It consists of a region 24 corresponding to the scattered light indicated by arrow FD,
The area except the area 22 becomes a dark area. Note that when the β-contaminant 18 enters the region 24 on the same plane side as the pattern forming body 16 with a light intensity equal to or lower than that of the region 20, the foreign material 18 is removed as described above. When the illumination light is on the glass surface side of the glass substrate 14, the illumination light is scattered and the specular reflection component is small, and the focal position shift due to the thickness of the glass substrate 14 also comes into play. For this reason,
The image of the foreign object 18 is defocused and there is no possibility that it will be projected as a pattern area.

Moreover, contrary to the above-mentioned case, if the mask 12 is turned upside down and the illumination light is made to enter from the mask surface side of the mask 12, even if the pattern formation body
By making the surface of 6 a mirror surface to increase the reflectance, the illumination light shining on the part of the foreign object 18 will be scattered.
, you can get a similar effect. However, in this method, if a foreign substance adheres to the narrow surface of the pattern forming body 16 (1), the illumination light from the part of the foreign substance will be scattered, which is undesirable because it will affect the pattern.

From this point of view, it is preferable that the illumination light be emitted from the glass surface side of the mask 12, as shown in FIG. Further, in this case, the light scattered by the foreign object 18 is attenuated and scattered by internal reflection within the glass substrate 14, and the effect that the light reaching the projection optical system becomes even weaker can be obtained.

As described above, in the present invention, since the reflected light from the mask 12 is utilized, it is preferable to increase the reflectance of light by the pattern forming body 16. Further, it is preferable that the light source for illumination has a large amount of light. As this light source, for example, an ultra-high pressure mercury discharge lamp, a light emitting type excimer laser, or a pulse emission type excimer laser is suitable.

Next, a first embodiment of the present invention will be described with reference to FIG. In this embodiment, the present invention is applied to a reduction projection type exposure apparatus which is one type of central body wafer printing apparatus.

In FIG. 2, an elliptical mirror 10 is located behind the exposure light source 100.
2 is provided so that the light from the exposure light source 1DO is focused. The focused light is made monochromatic by an interference filter 104, and is further converted into a fly's eye inch η
The illuminance is illuminated by a person and converted into a uniform illuminance distribution.

A condenser lens 108 is placed next to the fly's eye integrator 106, so that the light converted into a uniform illuminance distribution is converted into substantially parallel light beams. This collimated light is purchased so as to be incident on the FUGRISM 10 as illumination light. In addition, in the following explanation, ellipse &102. Interference filter 104. Fly eye integrator 106 and condenser lens 10
8 will be collectively referred to as an illumination optical system 110.

Above the half prism 10, a mask 12 is placed.
It has been placed. The end of the mask 12 on the pattern surface side of the glass substrate 14 is fixedly supported by a vacuum chuck 112 . That is, the mask 12 is held by suction on the vacuum chuck 112 by supplying air to the vacuum piping 114 provided in the vacuum chuck 112 by an air distribution system (not shown). Note that in this embodiment, the mask 12
The illumination light enters from below, that is, from the glass surface side of the glass substrate 14, and the reflected light is used. Support is being provided.

On the other hand, below the half prism 10, that is, the mask 12
A projection optical system (reducing projection lens) 116 is placed on the opposite side of the VC, and a wafer 118, which is an object to be transferred, is placed below the VC. In addition to the reduction projection lens, an equal-magnification projection hing, 1-equal-magnification mirror projection, etc. are used.

Next, the overall operation of the above embodiment will be explained. First, the light emitted from the exposure light source 100 is transmitted to the illumination optical system 11.
The rays are converted into parallel rays with a monochromatic and uniform illuminance distribution, and enter the barf grism 10 from the right. The optical path of this illumination light is changed upward by the half prism 10 and enters the mask 12 from the glass surface side.

A part of the incident illumination light is reflected by the pattern forming body 16, and this reflected light passes through the half prism 10 and is emitted onto the projection optical system 116IC. A pattern 120 of the pattern forming body 16 is imaged onto the transfer surface.

Incidentally, although the illuminated light is also reflected on the glass surface side of the glass substrate 14 of the mask 12 (on the contrary, it is small).

Moreover, most of the illumination light that is incident on the foreign object 18 is scattered as explained in FIG. 1. Therefore, the pattern of foreign matter 18 is not imaged onto wafer 118.

Next, a second embodiment of the present invention will be described with reference to FIG. Note that the same code sounds are used for groove components similar to those in the above-described embodiment.

In this embodiment, compared to the 11 examples shown in FIG. 2 described above, the half prism 10 uses a polarizing beam splinter 204 whose optical path is changed depending on the M direction of the light. It's becoming l.

Specifically, a polarizing plate 202 is arranged between the polarizing beam splitter 200 and the condenser lens 108, and a λ4 wavelength plate is arranged between the polarizing beam splitter 200 and the glass substrate 14 of the mask 12. 204 are arranged.

To explain the operation of this embodiment, light that has been made monochromatic by the interference filter 104 is output from the condenser lens 108, and after being polarized to a certain degree by the polarizing plate 202, it enters the polarizing beam splitter 200. Therefore, the polarizing beam splitter 200 reflects almost 100% of the human light upwardly, that is, in the direction of the mask 12.

For the IC, the illumination light with anti-Sa dimensions is transmitted through the λ/4 wavelength plate 204.
As a result, the light becomes a predetermined circularly polarized light and enters the mask 12. Further, when the illumination light is reflected by the pattern forming body 16, it becomes light of reverse rotation. When this light passes through the λ/4 wavelength plate 204 again, it becomes linearly polarized light whose plane of polarization has been rotated by 90 degrees. That is, the polarizing beam splitter 200
The light incident on the V4 wavelength plate 204 from the λ/4 wavelength plate 2
The light incident on the polarizing beam splitter 200 from 04 differs by 90 in terms of E1 light. Therefore, the illumination light reflected by the pattern forming body 16VC passes straight through the polarizing beam splitter 200 and enters the projection optical system 116.

As described above, in this embodiment, the illumination light is polarized to separate the incident light and the reflected light. This will prevent a decrease in the original light incident on the meter.

Next, the sixth embodiment of the present invention will be explained with reference to FIG.
The same reference numerals will be used for the same components as in the embodiment described above.

This embodiment is different from the eleventh embodiment shown in FIG. 2 described above in that a liquid tank 300 filled with a predetermined liquid is used.

Specifically, the liquid tank 300 is provided below the mask 12 and is filled with a liquid 302.

This liquid 302 corrodes the glass surface (+111) of the glass substrate 14 of the mask 12.
The liquid 302 is selected so that the refractive index of the liquid 302 and the refractive index of the liquid 302 are approximately equal to -1. -! , /C% liquid accommodation 3
The lower part 1411 of 00, that is, the glass surface groove ( ) 4 on the half prism side has improved flatness accuracy.

To explain the operation of this 61 example, the illumination optical system 11
The illumination light that enters the half prism 10 from 0 is reflected by the half prism 10 and enters the liquid 10300 VC, and further enters the mask 12 and is reflected by the pattern forming body 16 of the mask 12. The light with f' is
The liquid passes through the liquid tank 300 again and enters the half prism 10. In the above incident and reflection process of illumination light, ?
7i, since the glass IIIT 304 of the tank 300 has a high flatness, scattering of light is prevented. Further, the glass substrate 14 of the mask 12 may not always have a flatness, especially the flatness of the glass surface side, due to mask formation, and its thickness may not be sufficiently controlled. This unevenness in flatness and thickness of the glass substrate 14 is corrected by the liquid 602 in the liquid tank 300. This fC&), glass group &1
The optical path length on the glass surface side of the glass substrate 14 is
The aberrations of the optical system using the projection optical system 116 are uniform over the entire surface and are constant regardless of variations in the surface degree f'':fL of the glass substrate 14, making it possible to form a precise projection optical system. , reflection on the glass surface side of the glass substrate 14 can be suppressed.

As described above, this embodiment is effective when the flatness of the glass surface, that is, the lower surface side of the glass substrate 14 of the mask 12 is poor, or when the thickness of the mask 12 cannot be sufficiently controlled [F ] Ru.

It should be noted that the present invention is not limited to the above-mentioned implementation, but for example, by applying an anti-reflection coating to the patterned surface of the glass plug 1 or 14 of the mask 12. Illumination incident on the projection source system 116)C
Among them, the light of the i1'7 part (i3 separator of the mask 12) that is not 6 is further 1 (((reduction is 15
It's going to be a problem. However, none of the above cases of pharyngitis have adhered to the mask.
Although I have only explained about the difference in temperature, heat and resistance, the resistance on the substrate of the mask (such as J5) is also a colleague.

〔Effect of the invention〕

As described above, according to the projection optical device according to the present invention, since the original pattern is projected using the light reflected by the mask, only the pattern on the pattern forming body is projected well, and foreign particles are , Isthmus; 1) Ruini-length mask! Patterns such as those on 5 plates of tin cannot be projected. The effect is that it can be achieved.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the basic principle of the projection optical device according to the present invention, FIG. 2 is a diagram showing the first embodiment of the present invention, and FIG. 411(
Figure εa4 shows the third embodiment of the present invention. mask, 14
...Glass substrate, 16... Pattern-formed body, 18.
...Ingredients, 1'00...k'J Hikarubuhihara, 110.
...Illumination source system, 116...Projection optical system, 11B...
・Waehha, 200... (114 beam splitter,
202...11.6 light plate, 204...λ/4 wavelength plate. Shima Agent Patent Attorney Sanfeng Kimura Figure 2 μ II Figure 3 Interchange υ 14 Figure 1 Iσ

Claims (4)

[Claims] (1) A projection optical device that forms a predetermined original pattern on a light-transmissive mask substrate using a light-reflective pattern forming body, and projects a light image of the original pattern onto an object to be projected via a projection optical system. The method further comprises: an illumination optical means for irradiating the mask substrate with illumination light; and a light guide means for introducing the illumination light reflected by the mask substrate into the projection optical system. Projection optical device. (2) The projection optical device according to claim 1, wherein the illumination means irradiates illumination light from a surface of the mask substrate opposite to the pattern formation surface. (3) The projection optical device according to claim 1 or 2, wherein the light guide means includes an optical path splitter that is a part of the illumination optical means. (4) The projection optical apparatus according to claim 2, wherein the illumination optical means includes illumination light polarization means, and the optical path splitter is a polarization beam splitter.