JPS61289628A - Photoelectron image transfer - Google Patents

Abstract

PURPOSE:To contrive to improve the resolution of a transferred image by a method wherein light is projected from the front part of the mask on the substrate side using the mask in a constitution, wherein parts of the thin film surface are formed as the photoelectron emission surfaces, and photoelectrons to be emitted from the photoelectron emission surfaces are projected. CONSTITUTION:A wafer 1 on a stage 3 is ready-arranged in opposition to a mask 2a in a vacuum and irradiation light 4 is irradiated on the mask 2a from the back surface of the mask 2a. Photoelectrons 6 to be emitted from the photoelectron emission surfaces, which are parts of the front of the mask, due to the action of the irradiation light 4 to reach the front part of the mask 2a are converged on the surface of the wafer 1 due to the action of the electric field between the mask 2a and the wafer 1 and the action of the uniform magnetic field, which is formed by Helmholtz coils 9, and the surface is exposed. The mask 2a is made in a constitution, wherein a semiconductor layer having an photoelectron effect, such as a GaAs semiconductor layer 11b, is formed on a material, which allows the irradiation light 4 to transmit, such as a gallium-phosphorus light-transmitting substrate 11a, the semiconductor layer 11b is made to correspond to the semiconductor substrate 11a, and a metal layer 12, which is patterned and has windows 12a, and alkali metal thin films 13 or the thin films 13 of a compound of the alkali metal are laminated on the semiconductor layer 11b.

Description

[Detailed Description of the Invention] [Summary] In a photoelectronic image transfer method in which photoelectrons emitted from a mask irradiated with light are projected, a semiconductor layer having a photoelectric effect and a patterned metal are placed on a transparent substrate. By using a mask in which a layer and a thin film of an alkali metal or its compound form a sequential layer structure and irradiating light from the substrate side of the mask, the projection distance of photoelectrons can be shortened and the resolution of the transferred image can be improved. It is something that

[Industrial application field]

The present invention relates to an improvement in a photoelectronic image transfer method for exposing a fine pattern to a wafer used in a VLSI.

Microfabrication processes are important in the manufacturing of VLSIs,
One of the microfabrication technologies (lithography technologies) is a technology that exposes micropatterns onto wafers and the like.

Conventionally, known exposure techniques of this type include ultraviolet exposure, electron beam exposure, X-ray exposure, and ion beam exposure, but each of them has the following problems.

That is, the ultraviolet exposure method is a method of transferring a mask pattern and has a high throughput and is suitable for mass production, but the resolution is insufficient due to the wavelength used.

The electron beam exposure method uses a beam spot to draw images and has low throughput.

Although the X-ray exposure method is a transfer method, various problems must be solved for mass production use. In particular, if SOR (synchrotron radiation) is used as a light source, there is a concern that the equipment will be severely damaged.

The ion beam exposure method uses a beam spot drawing transfer method, and is expected to have processing capacity that can meet mass production, excellent resolution, and equipment that does not become too large, and further improvements in transfer performance are desired. There is.

[Conventional technology]

FIG. 3 is an explanatory diagram of a conventional photoelectronic image transfer method.

The method shown in the figure is a photoelectronic image transfer method disclosed by the inventor of the present invention in Japanese Patent Application No. 59-243343 and Japanese Patent Application No. 59-252151 as a method for improving processing performance.

That is, in a vacuum, the wafer l on the stage 3 is placed facing the mask 2, and the irradiation light 4 is reflected by the reflection plate 5 placed between the wafer 1 and the mask 2, and the wafer 1 is reflected from the front surface of the mask 2. The photoelectrons 6 emitted from the photoelectron emitting surface illuminate the electric field between the mask 2 and the wafer 1, and
This is a method in which the surface of the wafer 1 is focused and exposed by the action of a uniform magnetic field formed by the north pole 7 and the south pole 8 of the magnet.

As shown in the side sectional view of FIG. 4, the mask 2 is patterned on a semiconductor substrate 11 having a photoelectric effect and has windows 12a.
A thin film of an alkali metal or its compound forming a photoelectron emitting surface and a metal layer 12 having a thickness II! 13 are laminated.

The semiconductor of the substrate 11 is gallium arsenide (GaAs).
* As the metal of the metal layer 12, platinum (
Pt), gold (Au), silver (Ag), etc.
! Cesium (Cs) is used as the alkali metal of No. 13, and cesium tellurium (Csz Te), cesium antimony (C33Sbz), etc. are used as compounds thereof.

And Thin II! The deposition of No. 13 is carried out in a vacuum and used for exposure without being taken out into the atmosphere.

During exposure, when the irradiation light 4 is irradiated as described above, photoelectrons 6 are emitted forward from the surface of the thin film 11113 serving as the photoelectron emitting surface, but the combination of the surface layer of the substrate 11, the metal layer 12, and the thin film 13 Accordingly, window 1 of metal layer 12
The emission intensity from the region 2a is extremely strong compared to the regions other than the window 12a, and the pattern of the metal layer 12 is transferred onto the wafer l.

The resolution of the transferred image transferred onto the wafer 1 is
It is inversely proportional to the projection distance of the photoelectrons 6, that is, the distance dimension a between the mask 2 and the wafer 1, and is proportional to the electric field strength between the mask 2 and the wafer 1.

[Problem that the invention seeks to solve]

Therefore, in order to improve the above-mentioned resolution, it is desirable to reduce the interval dimension a.

However, the above-mentioned transfer method has the problem that since the mask 2 is irradiated with the irradiation light 4 from the thin film 13 side, the interval dimension a has to be increased, resulting in a decrease in resolution.

[Means for solving problems]

FIG. 1 is an explanatory diagram of an embodiment of the photoelectronic image transfer method according to the present invention.

The above problem is solved by forming a layer structure in which a semiconductor layer having a photoelectric effect, a patterned metal layer, and a thin film of an alkali metal or its compound are sequentially formed on a transparent substrate, as shown in FIG. By the photoelectron image transfer method of the present invention, using a mask 2a having a photoelectron emitting surface on the surface of the cough membrane, irradiating light 4 from the substrate side of the mask 2a and projecting photoelectrons 6 emitted from the photoelectron emitting surface. resolved.

[Effect]

In this method, since the irradiation light 4 is irradiated from the substrate side of the mask 2a, it is possible to significantly shorten the interval dimension a described above compared to the conventional example, and this shortening greatly improves the resolution of the transferred image. I can do it.

However, the semiconductor layer, the metal layer, and the thin film of the mask 2a function in the same manner as the conventional mask 2, and the throughput of the conventional mask is not lost.

〔Example〕

Hereinafter, an example will be described using FIG. 1 and a side sectional view of FIG. 2 showing an example of a mask used in the example.

In the method shown in FIG. 1, a wafer 1 on a stage 3 is placed facing a mask 2a in a vacuum, and irradiation light 4 irradiates the mask 2a from the back side and reaches the front side of the mask 2a. Photoelectrons 6 emitted from the front photoelectron emission surface by the action of the irradiation light 4 are caused by the action of the electric field between the mask 2 and the wafer 1 and the uniform magnetic field similar to the conventional example formed by the Helmholtz coil 9. This is a method in which the surface of the wafer 1 is focused and exposed.

As shown in FIG. 2, the mask 2a consists of a semiconductor layer 1 made of a semiconductor having a photoelectric effect, such as GaAs, on a transparent substrate 11a made of a material such as gallium phosphide (GaP) that transmits the irradiation light 4.
1b (thickness approximation) is made to correspond to the semiconductor substrate 11 of the conventional example shown in FIG. A thin layer of alkali metal or its compound forming 1
1113 are laminated.

During exposure, the irradiation light 4 is applied to the mask 2a on the transparent substrate 11a.
When irradiated from the side, the irradiated light 4 reaches the semiconductor layer 11b and emits photoelectrons 6 forward from the surface of the thin film 13 which becomes the photoelectron emitting surface as described above.
Metal layer 121. Thin IIl! 13 is equivalent to the combination of the surface layer of the substrate 11, the metal layer 12, and the thin film 13 of the conventional mask 2, and the emission intensity from the window 12a region of the metal layer 12 is extremely strong compared to the region other than the window 12a. , the pattern of the metal layer 12 is transferred onto the wafer 1 as in the conventional example.

As mentioned above, the resolution of the transferred image is inversely proportional to the distance a between the mask 2a and the wafer 1, but in the case of the conventional example shown in FIG. Since the space that was required to be provided between the wafer 1 and the wafer 1 is no longer required, for example, in the conventional example, the size of the mask 2 is approximately 5.
Whereas in the case of a triangular mask, a spacing dimension a of about 5 is required, in this method, for masks 2a of the same size, a spacing dimension a of about 5 mm is required.
can be reduced to approximately 1 (2), and the resolution has actually been improved to approximately 5 times that of the conventional example.

In the above embodiment, GaP and GaAs were used for the transparent substrate 11a and the semiconductor layer 11b of the mask 2a, but other materials may be used, such as sapphire (A1203) and St.

〔Effect of the invention〕

As explained above, according to the configuration of the present invention, in a photoelectronic image transfer method in which photoelectrons emitted from a mask irradiated with light are projected, transfer is achieved by reducing the distance between the mask and the wafer while maintaining processing capacity. This has the effect of improving image resolution and further improving transfer performance.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of an embodiment of the photoelectronic image transfer method according to the present invention, FIG. 2 is a side sectional view of an example of a mask used in the embodiment, FIG. 3 is an explanatory diagram of a conventional photoelectronic image transfer method, and FIG. The figure is a side sectional view of an example of a mask used in the conventional method. In the figure, 1 is a wafer, 2.2a is a mask, 3 is a stage, 4 is an irradiation light, 5 is a reflector,
6 is the photoelectron, 7 is the N pole of the magnet,
8 is the S pole of the magnet, 9 is the Helmholtz coil, 11 is the semiconductor substrate, 11a is the transparent substrate, llb is the semiconductor layer, 12 is the metal layer, 12a is the ion, 1
3 is a thin film, and a is an interval dimension. Hon NEI Kafusashisha Itari Q fragile Ql Tea 1 Diagram 2 Pavilion

Claims (1)

[Claims] A mask (2a) in which a semiconductor layer having a photoelectric effect, a patterned metal layer, and a thin film of an alkali metal or its compound are sequentially layered on a transparent substrate, and the surface of the thin film is a photoelectron emitting surface. A photoelectron image transfer method characterized in that light (4) is irradiated from the substrate side of the mask and photoelectrons (6) emitted from the photoelectron emitting surface are projected using the photoelectron image transfer method.