JPH0652704B2 - Projection exposure method and apparatus - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure method and apparatus used for, for example, a semiconductor wafer printing apparatus in the manufacture of semiconductor devices, which projects a predetermined pattern.

[Prior Art] A conventional projection exposure apparatus uses light transmitted through a mask or reticle (hereinafter simply referred to as a "mask") having a predetermined pattern for exposure. As the mask, a mask having a necessary pattern formed on a light-transmitting substrate such as glass by a light-shielding substance such as chromium is used. When light is emitted from one surface side of the mask by an appropriate light source, the light is transmitted to the other surface side except the pattern portion. This transmitted light enters a predetermined projection optical system,
As a result, the image of the pattern is projected onto the wafer coated with a predetermined photosensitive resist.

[Problems to be Solved by the Invention] In the projection exposure apparatus as described above, if there is dust, fingerprints, scratches, or the like that block light at a portion on the mask substrate where light should pass, it should be transmitted by these. The light will be blocked locally. Therefore, the image of these dusts and the like is also projected, which adversely affects the originally projected pattern. Therefore, the element or the circuit formed on the semiconductor wafer may be defective and the production efficiency may be reduced.

The present invention has been made in view of the above points, and an object thereof is to provide a projection exposure method and apparatus capable of improving the above-mentioned drawbacks of the conventional technology and reducing the occurrence of defects in a projection pattern due to dust or the like. To do.

[Means for Solving the Problems] In order to achieve the above object, in the projection exposure method according to the present invention, a mask substrate formed by forming an original pattern on one surface of a substrate having a predetermined thickness is used for exposure. When irradiating an energy ray and projecting and exposing an energy distribution corresponding to the original image pattern on a sensitive substrate, the original image pattern of the mask substrate is formed of a material having reflectivity with respect to the energy ray. A reflected energy ray is generated from the substance forming the original image pattern by irradiating the energy ray on the substrate, and the reflected energy ray has a predetermined magnification so as to have an energy distribution similar to the original image pattern on the sensitive substrate. It is guided to the sensitive substrate via a projection system.

In this case, preferably, the mask substrate is formed in a state where the substance is brought into close contact with one surface of the substrate that is transparent to the energy rays, and the energy beam for exposure is formed on the other surface of the transparent substrate. The surface side is irradiated so that the reflected energy rays are generated from the other surface side of the transparent substrate.

Further, in the projection exposure apparatus according to the present invention, an illumination system for irradiating exposure light to a mask substrate formed by forming an original image pattern on one surface of a transparent substrate having a parallel surface with a predetermined thickness, and the original image. A projection system for image-projecting a light distribution corresponding to the pattern onto the photosensitive substrate is provided, and in order to achieve the above-mentioned problems, the original pattern of the mask substrate is provided with reflectivity for the illumination light. Formed of a substance having the above structure, and guides the illumination light from the illumination system to the mask substrate in the projection optical path between the mask substrate and the photosensitive substrate and projects the reflected light from the substance forming the original image pattern. A light guide means for guiding the photosensitive substrate through the system is arranged.

In this case, in a preferred aspect, the light guide means includes an optical path splitter arranged in a common optical path of the illumination light path of the illumination light from the illumination system to the mask substrate and the projection light path.

In yet another preferred aspect, the illumination system is arranged so as to irradiate the illumination light from a surface opposite to one surface of the mask substrate on which the original image pattern is formed, and the light guide unit directs the original image pattern. It is arranged so as to guide the reflected light, which is reflected by the constituent material and has passed through the transparent substrate, to the projection system.

When the light guide means includes the optical path splitter, according to a preferred aspect, the illumination system is configured to give the illumination light a specific polarization characteristic, and the optical path splitter is configured by a polarization beam splitter. It

According to still another preferred aspect, the projection system is configured by either a projection lens system or a mirror projection system, and the illumination system includes either a discharge lamp or a laser as a light source that emits the illumination light. I'm out.

According to still another preferred embodiment, the mask substrate has an antireflection coating on the surface of the transparent substrate on which the original image pattern is formed, so that there is no substance forming the original image pattern on the transparent substrate. Measures are taken to reduce the reflected light from the part.

[Operation] In the projection exposure method and apparatus according to the present invention, reflected light, not transmitted light from the mask substrate, is used for projection exposure of the mask pattern onto the photosensitive substrate.

That is, the operation of the present invention will be described with reference to FIG. 1 showing the basic principle of the present invention. In FIG.
The light enters the mirror prism (hereinafter, simply referred to as “half prism”) 10 that splits the optical path from the right side of the drawing as indicated by arrow FA. The mask 12 is arranged above the half prism 10, and the illumination light incident as shown by the arrow FA illuminates the mask 12 from its lower surface by the action of the half prism 10.

The mask 12 is formed by forming a predetermined pattern of a light shielding material (hereinafter simply referred to as a pattern forming body) 16 such as chromium on the upper surface of a glass substrate 14 having a parallel flat surface by a method such as vacuum deposition. Here, it is assumed that the foreign matter 18 is attached to the portion of the pattern on the glass substrate 14 through which light is transmitted. Further, the illumination light is adapted to enter from the lower surface side of the glass substrate 14 of the mask 12, that is, the glass surface on the side where the pattern forming body 16 is not provided.

Of the illumination light incident on the glass substrate 14, the light incident on a portion other than the pattern forming body 16 or the foreign matter 18 is indicated by an arrow F.
As shown in B, it is almost transmitted through the glass substrate 14.

On the other hand, the light incident on the pattern forming body 16 has a flat incident surface, and since the pattern forming body 16 is provided with a metal light-shielding film such as chromium by vacuum deposition on the flat surface, the light is reflected by specular reflection. As shown by the arrow FC, the optical path is the reverse of the incident light. This reflected light is a half prism 1
Pass 0 straight down.

On the other hand, most of the illumination light that has entered the foreign matter 18 is scattered because the foreign matter is indefinite, and the reflected light from the foreign matter 18 is extremely unlikely to enter the half prism 10.

Therefore, the reflected light FC corresponding to the pattern shape of the pattern forming body 16 mainly enters the projection optical system (not shown) arranged below the mask 12. That is, the pattern of the incident light with respect to the projection optical system includes a region 20 corresponding to the transmitted light indicated by the arrow FB, a region 22 corresponding to the reflected light indicated by the arrow FC, and a region 24 corresponding to the scattered light indicated by the arrow FD. Area 2
Except for 2, the area is substantially dark. The area 24 is the area 2
The amount of light is equal to or less than 0.

The above is the case where the foreign material 18 is on the same surface side as the pattern forming body 16. However, when the foreign material 18 is attached to the lower surface side of the glass substrate 14, the illumination light is scattered by the foreign material, so the projection optical system. In addition to having a small amount of reflection component going to
Depending on the thickness of the glass substrate 14, the shift of the focal position with respect to the pattern forming body 16 also acts. Therefore, the foreign matter 1
The image 8 is defocused on the image plane side of the projection optical system, and the image of the foreign matter 18 is less likely to be projected as a defect image on the photosensitive substrate.

Contrary to the case of FIG. 1 described above, even if the upper and lower surfaces of the mask 12 are turned upside down so that the illumination light is made incident on the pattern surface side of the mask 12 from below, If the surface of 16 is used as a mirror surface to increase the reflectance, the same effect can be obtained by scattering of the illumination light incident on the foreign matter 18 attached to the portion other than the pattern forming body 16. Body 16
When the foreign matter 18 adheres to the surface of the foreign substance, the illumination light of the foreign matter portion is scattered and the incident light to the projection optical system is locally dimmed, and the pattern image projected on the photosensitive substrate is locally illuminated. It is not preferable because it has a negative influence. From this point of view, it is preferable that the illumination light is made incident on the glass surface side of the mask 12 where the pattern forming body 16 is not formed, as shown in FIG. Further, by doing so, most of the scattered light by the foreign material 18 is attenuated and scattered by the internal reflection in the glass substrate 14, and the unnecessary light reaching the projection optical system is further weakened.

As described above, in the present invention, since the reflected light from the mask 12 is used for projection exposure, the higher the reflectance of light by the pattern forming body 16 is, the more preferable result is obtained. Further, it is preferable that the light source for illumination also has a large amount of light, and as such a light source, for example, an ultra-high pressure mercury discharge lamp or a pulse emission type excimer laser is suitable.

[Examples] Hereinafter, a projection optical apparatus according to the present invention will be described in detail based on Examples shown in the accompanying drawings.

FIG. 2 shows a first embodiment of the present invention, which is an example in which the present invention is applied to a reduction projection type exposure apparatus which is one of semiconductor wafer printing apparatuses.

In FIG. 2, an elliptical mirror 10 is provided behind the exposure light source 100.
2 is provided so that the light from the exposure light source 100 is condensed. The condensed light is the interference filter 104.
Is made into a single color by the fly eye integrator 1
The light is incident on 06 and is converted into light having a uniform illuminance distribution.

A condenser lens 108 is arranged next to the fly-eye integrator 106 so that the light converted into a uniform illuminance distribution is converted into substantially parallel rays. The light converted into parallel rays enters the half prism 10 as illumination light. In the following description, the elliptical mirror 102,
Interference filter 104, fly-eye integrator 106
The condenser lens 108 and the condenser lens 108 are collectively referred to as an illumination optical system 110.

The half prism 10 is the same as that described above with reference to FIG. 1, and the mask 12 is arranged above it. The edge of the mask 12 on the pattern surface side of the glass substrate 14 is fixed and supported by the vacuum chuck 112. That is, the mask 12 is suction-held on the vacuum chuck 112 by evacuation from the vacuum pipe 114 provided on the vacuum chuck 112 by an exhaust system (not shown). In this embodiment, the illumination light enters from below the mask 12, that is, from the glass surface side of the glass substrate 14, and is used for projection exposure of reflected light by the pattern forming body 16 that is closely formed on the pattern surface of the glass substrate 14. Therefore, support is provided on the upper surface side of the mask 12 so as not to interfere with the incidence or reflection of these illumination lights.

On the other hand, below the half prism 10, that is, the mask 12
The projection optical system (reduction projection lens) 11 is provided at the position opposite to
6 is arranged, and further below that, a wafer 118, which is a transferred body, is arranged. The projection optical system 11
6 includes an equal-magnification projection lens in addition to the reduction projection lens,
The same-magnification mirror projection may be used.

Next, the overall operation of the first embodiment will be described.
First, the light emitted from the exposure light source 100 is converted into parallel rays having a uniform illuminance distribution of a single color by the illumination optical system 110, and enters the half prism 10 from the right side of the drawing. The optical path of the illumination light is changed upward by the half prism 10, and enters the mask 12 from the lower surface of the glass substrate 14, that is, the glass surface side.

Part of the incident illumination light is reflected by the pattern forming body 16, and the reflected light travels backward and passes through the half prism 10 to enter the projection optical system 116. Then, the pattern 120 of the pattern forming body 16 is imaged on the transfer surface of the wafer 118 by the projection optical system 116.

The glass substrate 14 of the mask 12 also reflects the illumination light on the glass surface thereof, but this is extremely smaller than the light reflected by the pattern forming body 16. In addition, most of the illumination light that is incident on the foreign matter 18 will be scattered as described in FIG. Therefore, an image of the foreign material 18 that causes a defect is not formed on the wafer 118.

Next, FIG. 3 shows a second embodiment of the present invention.
The same reference numerals are used for the same components as those in the figure or FIG.

In the second embodiment, as compared with the first embodiment shown in FIG. 2 described above, a polarization beam splitter 200 that changes the optical path according to the polarization direction of light is used as the optical path splitting means instead of the half prism 10. , A polarizing plate 202 and a quarter-wave plate (hereinafter referred to as a λ / 4 wave plate) 204 are combined.

More specifically, a polarizing plate 202 is arranged between the polarizing beam splitter 200 and the condenser lens 108, and a λ / 4 wavelength plate 204 is arranged between the polarizing beam splitter 200 and the glass substrate 14 of the mask 12. It is arranged.

Explaining the operation of the present embodiment, the condenser lens 108 outputs the light monochromaticized by the interference filter 104, and the light is incident on the polarization beam splitter 200 after being subjected to a certain polarization by the polarizing plate 202. The polarization beam splitter 200 directs this polarized incident light upwards or mask 12 with a reflectance of approximately 100%.
In the direction of.

The illumination light directed upward is turned into circularly polarized light in a predetermined direction by the λ / 4 wavelength plate 204 and enters the mask 12. When the incident circularly polarized light is reflected by the pattern forming body 16, the reflected light becomes circularly polarized light having a reverse rotation with respect to the incident circularly polarized light. When this light passes through the λ / 4 wave plate 204 again, it becomes a linearly polarized light whose polarization plane is inclined opposite to the incident light. That is, the polarization planes of the light entering the λ / 4 wavelength plate 204 from the polarization beam splitter 200 and the light entering the polarization beam splitter 200 from the λ / 4 wavelength plate 204 are different by 90 °. Therefore, the light reflected by the pattern forming body 16 is not reflected by the polarization beam splitter 2
It goes straight down in 00 and enters the projection optical system 116.

As described above, in the second embodiment, since the incident light and the reflected light are separated by giving appropriate polarization to the illumination light, the illumination light incident on the photomask 12 and the wafer 1 are separated.
A decrease in the amount of light incident on 18 is prevented.

FIG. 4 shows a third embodiment of the present invention. In this case as well, the same reference numerals are used for the same reference numerals as those in FIGS. 1 to 3 described above. .

The third embodiment is different from the first embodiment shown in FIG. 2 described above in that a liquid tank 300 filled with a specific liquid is used.

More specifically, the liquid tank 300 is provided below the mask 12, and the inside thereof is filled with the liquid 302. The glass surface side of the glass substrate 14 of the mask 12 is dipped in the liquid 302, and the refractive index of the glass substrate 14 and the liquid 3
The composition of the liquid 302 is selected so that the refractive index of 02 is almost the same. Further, the lower side of the liquid tank 300, that is, the half prism 10 side is constituted by a transparent glass surface 304, and this glass surface 304 has a highly accurate flatness.

The operation of this embodiment will be described. Illumination optical system 110
The illumination light that has entered the half prism 10 from above is reflected upward by the half prism 10 and enters the liquid tank 300, and further enters the mask 12. Further, the light reflected by the pattern forming body 16 of the mask 12 travels backward, passes through the liquid tank 300 again, passes through the half prism 10, and enters the projection optical system 116. In the above-described illumination light incidence / reflection process, first, the glass surface 304 of the liquid tank 300 has a high degree of flatness, so that the occurrence of aberration of the optical system is prevented. Further, the glass substrate 14 of the mask 12 is
Due to the mask forming process, the flatness, especially the flatness on the glass surface side, may not always be increased, and the thickness may not be sufficiently controlled so that the individual masks have the same thickness. The unevenness of the flatness of the glass substrate 14 and the thickness of the glass substrate for each mask is caused by the liquid tank 30.
It will be corrected by the liquid 302 in 0. In this way, the optical optical path length on the glass surface side of the glass substrate 14 is made uniform over the entire surface of the glass substrate 14, and the aberration of the optical system using the projection optical system 116 is reduced.
It is possible to configure a precise projection optical system by keeping the value constant regardless of the variation in thickness and flatness. Further, reflection on the glass surface side of the glass substrate 14 can also be suppressed.

As described above, in the third embodiment, when the flatness of the glass surface of the glass substrate 14 of the mask 12, that is, the lower surface side is poor, or the thickness of each mask 12 cannot be controlled sufficiently uniformly. Especially effective.

The present invention is not limited to the above-mentioned embodiments, and for example, by applying an antireflection coating to the pattern surface of the glass substrate 14 of the mask 12,
Of the illumination light incident on the projection optical system 116, the case where the light of the dark portion (the transparent portion of the mask 12) not corresponding to the pattern is further reduced is also included in the scope of the present invention.

Further, although any of the above-described embodiments has been mainly described as a countermeasure against foreign matter attached on the mask, the present invention also has the same effect on scratches on the substrate of the mask.

[Effects of the Invention] As described above, according to the present invention, the projection exposure of the original image pattern is performed using the reflected light from the mask.
Only the pattern of the pattern forming body is projected well, and unnecessary patterns such as foreign matter, dust or scratches on the mask substrate are not substantially projected, and therefore, the labor of cleaning and inspecting the mask is simplified. There is an effect that it is possible to save labor and improve productivity in manufacturing a semiconductor device.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing the basic principle of the present invention, FIG. 2 is a configuration diagram showing a first embodiment of the present invention, and FIG. 3 is a configuration diagram showing a second embodiment of the present invention. The drawing is a block diagram showing a third embodiment of the present invention. (Explanation of symbols of main parts) 10 ... Half prism, 12 ... Mask, 14 ... Glass substrate, 16 ... Pattern forming body, 18 ... Foreign matter, 1
00 ... exposure light source, 110 ... illumination optical system, 116 ...
Projection optical system, 118 ... Wafer, 200 ... Polarizing beam splitter, 202 ... Polarizing plate, 204 ... λ / 4 wavelength plate.

Claims (6)

[Claims] 1. A mask substrate comprising a transparent substrate having a predetermined thickness on one surface of which a substance to be an original image pattern is formed is irradiated with an energy ray for exposure to obtain an energy distribution corresponding to the original image pattern. In the method of performing projection exposure on a sensitive substrate, a substance having a reflectivity for the energy rays is formed in close contact with one surface of the mask substrate, and the other surface side of the mask substrate is used for the exposure. Irradiation with energy rays causes the reflected energy rays to be reflected by the material forming the original pattern and emitted from the other surface of the mask substrate, and the reflected energy rays form the original pattern on the sensitive substrate. Projection characterized in that the reflected energy rays are guided to the sensitive substrate through a projection system of a predetermined magnification so as to have a similar energy distribution. Exposure method. 2. An illumination system for irradiating an illumination light for exposure to a mask substrate formed by forming an original image pattern on one surface of a transparent substrate having a parallel surface having a predetermined thickness, and a light corresponding to the original image pattern. In a projection exposure apparatus comprising a projection system for image-forming and projecting a distribution on a sensitive substrate, the original image pattern of the mask substrate is formed of a material having a reflectivity for the illumination light, and the mask substrate and the sensitive substrate. Is disposed in the projection optical path between the substrate and the illumination system, and guides the illumination light from the illumination system to the mask substrate, and guides the reflected light from the substance forming the original image pattern to the sensitive substrate via the projection system. A projection comprising: a light splitter; and a holding member for holding the mask substrate so that one surface side of the mask substrate on which the original image pattern is formed faces the opposite side of the light splitter. Light equipment. 3. The illumination system is arranged so as to irradiate the illumination light from a surface opposite to one surface of the mask substrate on which an original image pattern is formed, and the light splitter divides the original image pattern. The projection exposure apparatus according to claim 2, wherein the projection exposure apparatus is arranged so as to guide the reflected light that has been reflected by the constituent substances and passed through the transparent substrate to the projection system. 4. The illumination system according to claim 2, wherein the illumination system is configured to give a specific polarization characteristic to the illumination light, and the light splitter is configured by a polarization beam splitter. The projection exposure apparatus described. 5. The projection system is configured by either a projection lens system or a mirror projection system, and the illumination system includes either a discharge lamp or a laser as a light source for emitting the illumination light. Claim 2 to
The projection exposure apparatus according to item. 6. The mask substrate has an antireflection coating on a surface of a transparent substrate on which the original image pattern is formed, and reduces reflected light from a portion on the transparent substrate where a substance forming the original image pattern does not exist. The projection exposure apparatus according to claim 3, characterized in that