JPS604943A - Photomask - Google Patents

Abstract

PURPOSE:To mitigate a steep level difference without changing the manufacturing process of a semiconductor integrated circuit device by forming patterns changed in light transmittance partially in a light intercepting pattern formed on the surface of a glass plate. CONSTITUTION:A metallic film 7 is uniformly formed on a glass plate 1. A pattern 2 is formed on the film 7 by the lithographic process. The pattern 2 is coated with a photosensitive resin and exposed and developed. The resin 8 is masked, the pattern 2 is etched down to the half way to form a pattern 6 for changing light transmittance. The photomask thus formed does not transmit light through a pattern thick in pattern film thickness but it transmits light through a thin pattern to a certain extent. As a result, the sectional form of the photosensitive resin is made gentle in slope on the place different in level.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a photomask used in a photolithography process for manufacturing semiconductor integrated circuit devices and the like.

Generally, semiconductor integrated circuit devices consist of a diffusion process and an assembly/finishing process. The diffusion process is a round trip between each process such as impurity introduction and film formation and a photoringraph, and circuit elements such as X, retransistor, diode, etc. and wiring are formed in this round trip. Photolithography includes steps such as coating a photosensitive resin on an oxide film or metal film, overlapping a wafer and a photomask, exposing and developing, etching, and etching.

Conventionally, a photomask used in the photolithography process is as shown in FIG. 1, in which a metal film is formed on a glass plate 1 by thin film or L vapor deposition, and a pattern 2 of a semiconductor integrated circuit device is formed regularly on the glass plate 1. It was formed by arranging them.

The shape of this box is shown in FIG. This pattern 2 is made of a uniform layer of metal, and within the same pattern, light is uniformly blocked and no light is transmitted.

In recent years, as semiconductor integrated circuit devices have become more dense and highly integrated, it has become essential to adopt a multilayer wiring structure, and the need to alleviate steep step structures has rapidly increased. FIG. 3 shows an example of two-layer metal wiring using a conventional photomask. A photosensitive resin is applied onto the first layer metal film 3 on the semiconductor foil 9, and exposed, developed, etched, and etched. Then, an interlayer insulating film 4 is deposited, and a second metal film is formed thereon.
Similar photolithography is performed to form second layer metal wiring 5. In this case, since the conventional photomask uniformly blocks light, the photosensitive resin has a steep rectangular shape. For this reason, the coverage of the insulating film between the metal wiring is poor, resulting in a short circuit between 1.2 layers (
4) or the second layer metal wiring is easily broken due to the steep step portion (FIG. 5). The same thing applies to the level difference in the contact pole portion.

SUMMARY OF THE INVENTION An object of the present invention is to provide a photomask that allows steep steps to be reduced without changing the manufacturing process of a semiconductor integrated circuit device.

The 7 otomask of the present invention is characterized in that it has a pattern in which the amount of light transmitted is partially changed within the same light-shielding pattern formed on the surface of a glass plate.

6 and 7 each show an embodiment of the present invention.

Figure 6 is a row using a metal pattern in which the amount of light transmitted is changed continuously within the same pattern, and Figure 7 is an example in which the amount of light transmitted is changed stepwise by changing the thickness of the pattern. be. When a photomask embodying the present invention is used, the exposure lid changes, and the remaining film of the photosensitive resin changes in accordance with the amount of change. By performing drying and etching from above, it becomes possible to form a gentle step. Figure 8 shows the cross-sectional shape of the gentle step. The gentle step eliminates short circuits between the p-layers and disconnections at the two-step difference.

The present invention will be explained below using an example in which the pattern thickness is changed. A conventional photomask consists of a uniform metal film 7 on a glass plate.
A pattern 2 is formed through a photolithography process. This manufacturing process is shown in FIG. That is, a metal film 7 is deposited on a glass plate 1 and selectively removed using a photosensitive resin 8 to form a pattern 2 having a uniform thickness.

On the other hand, examples in which the present invention is implemented using a positive type photomask are shown in FIGS. 10 to 13. A metal film 7 is uniformly formed on the glass plate 1 (Fig. 10). A photolithography process is applied to the metal film to form a pattern 2 (Fig. 11). A photosensitive resin is then applied onto the pattern 2 and exposed. Perform development (Figure 12).

Using the photosensitive resin 8 in FIG. 11 as a mask, pattern 2 is etched halfway to form pattern 6 that changes the amount of light transmitted (FIG. 13).

In the photomask manufactured in this manner, the thick pattern film does not transmit light, and the thin pattern film thickness allows light to pass through to some extent. This makes it possible to make the cross-sectional shape of the photosensitive resin gentle and to make the stepped portions gentle.

Oka: Although the example is a photomask using a positive type photosensitive resin, the present invention can also be used when using a negative type photosensitive resin.

Furthermore, the nature of the glass plate and the type of metal forming the pattern are not limited in any way in the practice of the present invention.

[Brief explanation of drawings]

Figure g1 and Figure 2 are a plan view and a cross-sectional view of a conventional photomask. FIG. 3 is a cross-sectional view of a two-layer wiring semicircular integrated circuit device using a conventional product. FIG. 4 and FIG. 5V are diagrams illustrating defects that occur in conventional products. FIGS. 6 and 7 show photomasks to which the present invention is applied. FIG. 8 is a sectional view of a bibrow wiring semiconductor integrated circuit device manufactured using the product of the present invention. FIG. 9 is a diagram illustrating an outline of a conventional photomask manufacturing process. Examples of negative photomasks to which the present invention is applied are shown in FIGS. 101 to 13. FIG. 10 is a diagram showing a metal film formed on a glass plate. FIG. 11 is a diagram showing the pattern formed. FIG. 12 is a diagram showing the formation of a photosensitive resin serving as a mask for a pattern that blocks light. FIG. 13 is a diagram in which a pattern for changing the amount of light transmission is formed by etching. In addition, in the figure, 1...Glass plate, 2...
...Semiconductor integrated circuit pattern, 3...First layer metal wiring, 4...Interlayer insulating film, 5...
1st layer metal wiring, 6... Pattern for changing the amount of light transmission, 7... Metal film, 8... Photosensitive resin, 9... Semiconductor 1, Ha 0 Agent Patent Attorney Uchihara 1' 1. -/' Fig. %/7 Fig. 3 Fig. 8q

Claims (1)

[Claims] A photomask comprising a light-shielding pattern formed on the surface of a glass plate, characterized in that the photomask has a pattern in which the amount of light transmitted is partially changed within the same pattern.