JPS6048030B2 - How to form a photomask - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a film of metal or metal compound on the surface of a substrate.

It is well known that lithography technology is used to create fine patterns on semiconductor materials when manufacturing semiconductor devices. A pattern of a desired shape is formed.

Such masks can be broadly classified into emulsion masks, masks, and hard masks.Since hard masks can provide high-quality patterns, various coating materials have recently been developed and widely used.

By the way, coating materials include single metals, multi-component alloys, and compounds such as metal oxides and metal nitrides, and all of them must have shielding properties against light or electron beams. Similarly, when forming a pattern, it is an important condition that a fine pattern can be easily formed with high precision.

On the other hand, in the semiconductor field, LSI and VLSI are being researched and developed, and they require increasingly finer and more precise patterns.
For example, in the past, patterns were formed with a spacing of about 4 .mu.m, but in order to increase the switching speed and improve the degree of integration in the semiconductor device described above, it is now common to form patterns with a spacing of 2 .mu.m or less. As a result, roughness of about 0.5 to 0.3 .mu.m, which occurs at the peripheral edges of patterns, which was not a problem in the past, has become a fatal defect in semiconductor devices. When the photoresist film on the semiconductor substrate is exposed to light and the mask pattern is transferred, the scratches are magnified due to the reflection of the light, and sometimes remain as whiskers on the photoresist film, and the pattern on the semiconductor substrate An inconvenience occurs that causes a pause. The purpose of the present invention is to solve these problems, and when depositing a film made of a metal or a metal compound on a substrate surface, the film is deposited intermittently or the amount of film deposited per hour is reduced. The present invention proposes a method for forming a film, which is characterized in that the film is deposited by repeating the increase and decrease a plurality of times.

That is, in order to eliminate the roughness formed at the periphery of the above-mentioned film pattern, the method of forming the film is changed, and will be described in detail below using an example using a vacuum evaporation method.

5. FIG. 1 is a schematic diagram of a vacuum evaporation apparatus, in which a holder 3 that holds a substrate and rotates in a high vacuum chamber, an evaporation source 4, and a shutter 5 are provided.

When forming a film using such a vacuum evaporation apparatus, conventionally the evaporation source 4 is shielded with a shutter 5, and after a certain amount of evaporation occurs by heating the film material in the evaporation source 4, a certain amount of evaporation is performed. The shutter 5 is opened for a certain period of time to ensure that the coating material is deposited on the substrate 2, and after the required amount has been deposited, the shutter 5 is again used to shield the evaporation source 4 to complete the deposition.

The present invention is a method of repeatedly opening and closing the shutter 5 during a certain period of time when the shutter 5 is open. To explain with an example of wearing
After heating the metallic chromium evaporation source to reach a constant evaporation rate of 60 A/min, open the shutter 5 for 2 minutes and
20A is applied, and then the shutter 5 is closed for several tens of seconds. The shutter 5 is opened again to deposit the metal chromium, and when the shutter 5 is opened 5 times in this manner, a total film thickness of 600A is deposited. Next, the heating of the metal chromium evaporation source is stopped, and the chromium oxide evaporation source is heated. After the evaporation amount reaches a certain level of 30 A/min, the shutter 5 is opened and closed 5 times in the same manner as above for 2 minutes. Then, chromium oxide with a total thickness of 300A is deposited.

Then, 90 layers consisting of 10 layers as shown in Figure 2
A deposit with a film thickness of 0 A is formed. When this is etched with a wet etching solution mainly containing nitric acid complex salts to create a mask◆ pattern, the peripheral end face becomes jagged with a diameter of 0.1 μm or less, resulting in a much sharper end face than before.

3. This is thought to be due to the presence of films with slightly different stoichiometry between each layer. Instead of opening and closing such a shutter, the current value of the heating source of the evaporation source may be changed.

Figure 3 is a chart showing the situation, where the vertical axis shows the amount of evaporation deposit S.
1. Time T is plotted on the horizontal axis. After the evaporation source 4 is heated to reach a steady state, the shutter 5 is opened (indicated by 0PEN in the figure) and the current value of the heating source of the evaporation source is changed with time to increase the evaporation exposure. The coating amount S can be increased or decreased from almost O) state to the saw amount, which has the same effect as opening and closing a shutter, and a sharp peripheral edge surface can be obtained. Furthermore, similar results can be obtained not only by the vacuum evaporation method described above but also by sputtering by changing the applied electric field.

As is clear from the above explanation, the present invention forms a multilayered film by simply depositing the film intermittently or increasing or decreasing the amount of film deposited, and forms a sharp end surface by wet etching. It is highly effective in improving the quality and increasing the degree of integration of semiconductor devices.

Note that the present invention is applicable not only to semiconductor devices but also to other fields.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a vacuum evaporation apparatus, FIG. 2 is an example of a cross-sectional view of a film formed according to the present invention, and FIG. 3 is a chart showing increases and decreases in the amount of coating according to the present invention.

Claims (1)

[Claims] 1. A film made of a metal, a metal compound, or an oxide is deposited intermittently on the surface of a transparent glass substrate, and the film is deposited by repeatedly increasing and decreasing the amount of film deposited over a period of time. A method for forming a photomask, characterized by forming a mask pattern by post-photoetching.