JPS61289627A - Photoelectron image transfer - Google Patents

Abstract

PURPOSE:To correct the effect of the proximity effect and to enable to execute a faithful transfer even though the larger and smaller windows are included by a method wherein the photoelectron emission intensities are made to differ from one another by making the hole concentrations of the smaller window regions differ from those of the larger window regions. CONSTITUTION:In the formation of a mask 2a, before masking thin films 13; each consisting of part of a GaAs substrate 11, a Pt metal layer 12 and a Cs thin film 13; are coated, P type impurity ions, such as zinc Zn ions, are introduced in the windows 12a-12c of the substrate 11 by an ion beam-implantation or so forth and P-type regions 11a-11c to correspond to the windows 12a-12c are formed. The impurity concentrations of the P-type regions 11a-11c are respectively 3X10<19>/cm<3>, 8X10<18>/cm<3> and 5X10<18>/cm<3> and are set according to the order of the sizes of the windows 12a-12c. Moreover, the sizes of patterns 14a-14c to be formed on a wafer 1, which is transfer-exposed using the mask 2a, are made to nearly coincide with the sizes of the windows 12a-12c.

Description

[Detailed Description of the Invention] [Summary] In a photoelectron image transfer method in which a photoelectron emitting surface of a mask is irradiated with light, a patterned metal layer and an alkali metal are formed on a semiconductor substrate having a region of high carrier concentration in the surface layer. By using a mask that has a sequential layer structure with a thin film of the metal layer or a thin film of the compound, the intensity of the emitted photoelectrons can be varied depending on the size of the window in the metal layer, making it possible to correct the proximity effect.

[Industrial application field]

The present invention relates to a photoelectron image transfer method for exposing a fine pattern to a wafer used in a VLSI, and more particularly to an improvement in a photoelectron image transfer method for irradiating light onto a photoelectron emission surface of a mask.

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, such exposure techniques 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 large processing capacity (throughput) and is suitable for mass production, but the resolution is insufficient due to the wavelength used.

The electron beam exposure method is a method of writing using a beam dart and has a low throughput.

Although the X1ll exposure method is a transfer method, various problems must be solved for use in mass production. In particular, if SOR (synchrotron radiation) is used as a light source, there is a concern that it will cause too much damage.

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

In contrast, the photoelectronic image transfer method according to the present invention is based on a 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 is expected to have further improvement in transfer performance. desired.

[Conventional technology]

FIG. 5 is an explanatory diagram showing a conventional photoelectron image transfer method in which the photoelectron emission surface of a mask is irradiated with light.

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 ultraviolet irradiation light 4 is reflected by the reflection plate 5 placed between the wafer l and the mask 2, and the wafer l is placed opposite the mask 2. The photoelectrons 6 emitted from the front photoelectron emitting surface are irradiated by the action of the electric field between the mask 2 and the stage 3 and the uniform magnetic field formed by the N pole 7 and S pole 8 of the magnet. In this method, the surface of the wafer 1 is focused and exposed.

As shown in the side cross-sectional view of FIG.
A metal layer 12 with windows indicated by 2a to 12c and a thin film 13 of an alkali metal or its compound forming a photoelectron emission surface are laminated.

The semiconductor of the substrate 11 is gallium arsenide (GaAs).
+Gallium phosphide (GaP), indium arsenide (InA
Examples of metals for the metal layer 12 include ■-■ group such as S), IF-Vl group such as cadmium sulfide (CdS), and silicon (St). The alkali metal of the thin film 13 is cesium (Cs), and its compound is cesium tellurium (C32T13) + (!
35b2) etc. are used.

The thin film 13 is then deposited 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 metal layer 12, but the emission intensity from the window area of the metal layer 12 is extremely extreme compared to the area outside the window. The pattern of the metal layer 12 is strongly transferred to the wafer l.

[Problem that the invention seeks to solve]

In this case, the window area, for example, the windows 12a to 1 shown in FIG.
The intensities of the photoelectrons 6 emitted from the 2c region are approximately the same.

On the other hand, the object to be exposed is generally a resist layer 14 on the upper surface of the wafer 1, as shown in the side sectional view of FIG. 7, and after exposure, the resist layer 14 is patterned by development.

Then, using the above mask 2, the size is a”
When the windows 12a x 12c -c are transferred and exposed, the intensity of the projected photoelectrons 6 is uniform, so the pattern 14a = 14c (the figure is (showing the case of a negative resist) is determined by the so-called proximity effect.
Relatively, the small window 12a tends to shrink, and the large window 12c tends to enlarge, and if large and small windows coexist, such as the windows 12a to 12c, there is a problem that faithful transfer becomes difficult.

Means for Solving Problem C] FIG. 1 is an explanatory diagram showing an embodiment of the photoelectronic image transfer method according to the present invention.

As shown in FIG. 1, the problem is that a patterned metal layer and a thin film of an alkali metal or its compound form a sequential layer structure on a semiconductor substrate having regions with different carrier concentrations in the surface layer. This problem is solved by the photoelectron image transfer method of the present invention, which uses a mask 2a whose thin film surface is a photoelectron emitting surface, irradiates the photoelectron emitting surface with light 4, and projects photoelectrons 6 emitted from the cough surface.

According to the present invention, the carriers are holes, and the carrier concentration is preferably higher in the small window region of the metal layer than in the large window region.

[Effect]

It is generally known that the intensity of photoelectron generation in a specific semiconductor with a photoelectric effect becomes stronger when the semiconductor is made p-type (carriers are holes), and that it changes depending on the carrier concentration, and the higher the concentration, the stronger it becomes. It is being

The present invention takes advantage of this property and makes the photoelectron emission intensity different by making the hole concentration different between the small window region and the large window region.

This makes it possible to correct the influence of the proximity effect described above and to perform faithful transfer even when large and small windows coexist.

〔Example〕

The following are FIG. 1, a side sectional view of FIG. 2 showing an example of a mask used in the example, a characteristic diagram of FIG. Examples will be described using the side cross-sectional view of FIG.

Figure 1 is a diagram corresponding to Figure 5, and the method shown in Figure 1 is
The mask 2 in the conventional method shown in FIG. 5 is replaced with a mask 2a.1. The rest is the same as the conventional example.

The mask 2a shown in FIG. 2 includes a substrate 11 of GaAs, for example.
゜Thin III! of the conventional mask shown in FIG. 6, consisting of a Pt metal layer 12 and a Cs thin layer 111!13! 13 Prior to deposition,
A p-type impurity such as zinc (Zn) is added to the window 12a = 12c region of the substrate 11 by, for example, ion beam implantation.
p-type region 11a~ corresponding to window 12a=12c
llc was formed.

The impurity concentration of p-type regions 11a to llc is 3X, respectively.
10 self! /-18X10"/cffl, 5X101"/
-, and follow the order of the sizes of the windows 12a to 12c.

The quantum efficiency-irradiation light energy characteristics of this mask 2a are as follows:
As shown in FIG. 3, it can be seen that the intensity of photoelectrons 6 emitted from the small window 12a region is greater than that from the large window 12c region.

The pattern formed on the wafer l that has been transferred and exposed using the mask 2a is shown in FIG. 4, which corresponds to FIG. 7, and the sizes of the patterns 14a to 14C in FIG. 4 are as follows.
Unlike the case shown in FIG. 7, the size of the windows 12a to 12c is a
”-c.

In the above-described embodiment, the impurity concentration is set to three levels, but the impurity concentration does not need to be limited to three levels (it may be set as appropriate depending on the size of the window formed in the metal layer 12). good.

〔Effect of the invention〕

As explained above, according to the configuration of the present invention, it is possible to correct the proximity effect in a photoelectron image transfer method of irradiating light onto the photoelectron emission surface of a mask, which has the effect of making it possible to further improve transfer performance. There is.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing 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, and Fig. 3 is a quantum efficiency-irradiation light energy characteristic of the mask. Figure 4 is a side sectional view of an example of a wafer processed by the method of the present invention, Figure 5 is an explanatory diagram showing a conventional photoelectronic image transfer method, and Figure 6 is a side view of an example of a mask used in the conventional method. FIG. 7 is a side sectional view of an example of a wafer processed by the conventional method. In the figure, l is the wafer, 2.2a is the mask, 3 is the stage, 4 is the irradiation light, 5 is the reflector, 6 is the photoelectron, 7 is the north pole of the magnet, 8 is the south pole of the magnet, 11 is the semiconductor substrate, 11a = 11c is a p-type head area, 12 is a metal layer, 12a = 12c is a window, 13 is a thin film, 14 is a resist layer, 14a = 14c is a resist pattern, a''-c is 1
The size is 2a to 12c. Agent Patent Attorney Hiroshi Matsuoka Shibu 2 Illustrated Mask #4g Leather 3g

Claims (1)

[Claims] 1) A patterned metal layer and a thin film of an alkali metal or its compound formed on a semiconductor substrate having regions with different carrier concentrations in the surface layer form a layered structure in sequence, and the surface of the thin film is used to emit photoelectrons. A photoelectron image transfer method characterized in that using a mask (2a) having a surface, the photoelectron emitting surface is irradiated with light (4) and photoelectrons (6) emitted from the surface are projected. 2) The photoelectronic image transfer method according to claim 1, wherein the carrier is a hole, and the carrier concentration is higher in a small window region of the metal layer than in a large window region.