JPS61181130A - Formation of pattern - Google Patents

Abstract

PURPOSE:To enable the preparation of a minute pattern of high precision without repeating the conditions of lateration of dimensions when a reticle is designed, by a method wherein a half-transmitting portion pattern provided in a reticle is matched in position with a protuberant portion staged higher. CONSTITUTION:A reticle 6 is formed of a shielding portion (c) with a thick chrome film provided on a glass substrate 61, a half-transmitting portion (a) with a thin chrome film provided on the substrate, and a transparent transmitting portion (b). When exposure is conducted by means of this reticle 6 and with the same exposure amount, an exposure amount according with the thickness of a resist film 4 in the half-transmitting portion (a) and the transmitting portion (b) respectively cna be given, and consequently a resist film pattern having excellent precision as desired is formed. Concretely, an exposure energy applied to the resist film 4 is controlled in accordance with the film thickness, and the film thickness of the half-transmitting portion (a) is prepared in consideration of the film thickness of the half-transmitting portion (a) and that of the resist film 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a photomask and a pattern forming method thereof for forming a resist film pattern on a semiconductor substrate (wafer) surface using a photo process.

The semiconductor integrated circuit (IC) is LS1. It has been highly integrated and miniaturized with VLSI. This is because the higher the integration and density, the higher the performance.

Therefore, in the photo process, submicron fine patterns of about 1 μm or less are created.
Pattern) has come to be formed.

On the other hand, with the increase in integration and density, the surface of a semiconductor substrate becomes more uneven, and especially when wiring between elements is stacked in multiple layers, pattern accuracy tends to decrease and there is a fear of wire breakage.

Therefore, when forming a resist film pattern by photoprocessing, sufficient consideration must be given so that a highly accurate fine pattern is formed even in portions with steps.

[Prior Art] By the way, there are two types of photomasks for transfer: a contact exposure mask that exposes the semiconductor substrate in close contact with the semiconductor substrate, and a reticle that performs reduced exposure while maintaining a distance from the semiconductor substrate. Conventionally, in the photo process, Masks for close-contact exposure were mainly used, but with improvements in precision due to advances in optical machinery, reticles for reduction exposure have come into widespread use. The fact that the reticle is scratch resistant and has a long lifespan is another reason for its widespread use. The present invention will be explained below using a reticle as an example.

FIG. 4 shows a cross-sectional view of an exposure process in which a semiconductor surface with a step difference is exposed in a conventional photo process. In this example, a first layer of wiring 2 made of a polycrystalline silicon film with a film thickness of about 1 μm is provided on one surface of a semiconductor substrate (substrate to be processed).
On top of that is an insulating film 3 made of a phosphosilicate glass film with a film thickness of 1 μm.
and then coat the absolute ff1111i3 with a diameter of 1.8μ
This is a state diagram in which a resist film 4 is applied and this resist film is exposed with a reticle 5 for the purpose of opening a through hole of mφ. Note that the reticle actually has a pattern size enlarged 5 to 10 times, but in order to make it easier to understand, the reticle is shown reduced in size to have the same size as the formed pattern.

In the figure, 51 is a glass substrate of the reticle 5, and 52 is a chrome film pattern. Therefore, the resist film 4 uses a positive resist, and after the exposure process, the exposed portion of the resist film is dissolved and removed by development to form a resist film pattern with windows A and B. Using this as a protective film, the insulating film 3 is etched to form a window.

[Problems to be Solved by the Invention] By the way, when a resist is applied, since the resist is a fluid liquid, as shown in the figure, the resist I! it
A thin resist film (for example, 0.8 μm thick) is formed on the insulating film 3 on which the first layer wiring 2 is provided, and the surface of the other insulating film 11*3 is flat. A thick resist film (eg, 1.8 μm thick) is formed thereon.

Therefore, if the entire surface is irradiated with the same amount of exposure, if window A has the optimal exposure, window B will be underexposed, and window B will be underexposed.
If is the optimum exposure amount, window A will have too much path light,
There is a problem that a desired window pattern cannot be formed on both sides.

This problem has become more difficult as semiconductor devices become more highly integrated and miniaturized.
It is gradually getting a bigger close-up, and this is an IC.
This has a major impact on the quality and reliability of the product.

Therefore, at present, the dimensions of the window are changed by manipulating the reticle design. That is, the window A is made smaller than the desired size, and the window B is given the optimum exposure amount. Then, the window area A is irradiated with an excessive amount of exposure light, and due to the excessive exposure energy, the exposure energy sneaks into the surrounding area of the window area A and is exposed, and when it is developed, the window area A is exposed. After enlarging, a resist film pattern having exactly the optimum dimensions of the window portion A is formed.

This involves adjusting the dimensions of the window A when creating the reticle, but manipulating the dimensions when creating the reticle complicates the design of the reticle. The reticle is designed to have a large pattern in consideration of the amount of reduction of the pattern to be drawn on the IC, and further, dimensional operations are performed to adjust the exposure amount depending on the size of the pattern. All of these processes are controlled by computer calculations, as fixed rules apply. However, additional dimensional manipulation due to the above-mentioned steps complicates computer calculation control, and errors are likely to occur unless manual checks are added to all steps of the wafer process. This paper proposes a photomask that solves these problems and a pattern forming method using the photomask.

[Means for solving the problem] The problem was solved by using a photomask provided with a pattern consisting of a shielding part, a transparent part, and a semi-transparent part, and applying a resist solution onto a substrate to be processed with steps. A resist film is formed by coating, and then exposed using a photomask in which a semi-transparent pattern is aligned in the curved portion and a transparent pattern or a shielding pattern is aligned in the concave portion. This problem is solved by a pattern forming method that includes a step of forming a resist film pattern.

[Function] That is, the present invention provides a reticle with a semi-transparent part (also called a semi-shielding part) that reduces the amount of exposure to exposure light or electron beam, and positions the pattern of the semi-transmissive part on a convex part with a high step. Together, they are exposed and developed to form a resist film pattern.

In this way, when designing the reticle, the reticle can be created with a uniform and regular design, and a highly accurate fine pattern can be created without having to repeat the dimensional change conditions.

[Example] Hereinafter, embodiments will be described in detail with reference to the drawings.

FIG. 1 shows a cross-sectional view of a reticle 6 according to an embodiment of the present invention, and a putter 73 portion that is convex and exposes a window A that is thinly coated with a resist film has a thin chrome film. It has a pattern that covers it. Assuming that the thickness of the chromium film of the shielding part C is 1000 people, this part will cover about 100 people (several tens to hundreds of people).

Therefore, in this example, a reticle is formed from a shielding part C in which a thick chromium film is provided on the glass substrate 61, a semi-transmissive part a in which a thin chromium film is provided, and a transparent transmitting part A. .

Figure 2 shows a cross-sectional view of the exposure process in which a semiconductor surface with steps is exposed using such a reticle.This figure corresponds to Figure 4, and the same parts are given the same symbols. . When the resist film 4 is exposed with the same amount of light using this reticle 6, it is possible to give an exposure amount that matches the thickness of the resist film in the semi-transmissive part a and the transmissive part, thereby achieving the desired accuracy. A good resist film pattern is formed. That is, the present invention is a method of controlling the exposure energy applied to the resist film 4 according to the thickness of the resist film, and takes into account the film thickness of the semi-transparent part and the film thickness of the resist film. Create thickness.

Then, by using the resist film pattern thus formed as a protective film and etching the insulating film 3 to form through holes, highly accurate fine through holes are formed.

Moreover, such a reticle can be easily produced. Figures 3+8) to 3(C) show cross-sectional views in the order of the formation process. First, as shown in Figure 3(a), a thick chromium film 62 of about 1000 layers is sputtered on a glass substrate 61. A resist film pattern 65 is formed thereon, and the exposed chromium film is etched using this resist film pattern 65 as a protective film.

Etching is a dry process using, for example, carbon tetrachloride gas as a reaction gas.

Next, after removing the resist film pattern 65, a thin chromium film 62 with a thickness of about 100 mm is deposited again by sputtering, and a second resist film pattern 66 is applied thereon. Form. Using this resist film pattern 66 as a protective film, the film thickness of the chromium film 62 deposited again is 100.
Control sex to exclude only people. After that,
The resist film pattern 66 is removed, and the process is completed as shown in FIG. At this time, there is no need to create a new mask for forming the second resist film pattern 66, and it is sufficient to simply use the mask with steps from the previous process (the mask for patterning the first wiring). .

In this way, fine patterns can be formed with high precision,
It also becomes easier to create a reticle for use.

The above example is explained using a positive resist film, but
In the case of a negative resist film, a highly accurate fine pattern can be formed in the same way by simply reversing the shielding part and the transmitting part. Furthermore, it is easy to create a reticle.

It goes without saying that the present invention can be applied to a mask for contact exposure instead of a reticle.

[Effects of the Invention] As is clear from the above description, according to the present invention, patterning can be performed with high accuracy on an IC surface having a step, which is useful for improving the reliability and quality of an IC.

Furthermore, it is not difficult to create such a transfer mask.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a photomask according to an embodiment of the present invention, FIG. 2 is a cross-sectional view showing an exposure process using the photomask, and FIG.
A) to (C) are cross-sectional views in the order of steps for producing the photomask, and FIG. 4 is a cross-sectional view showing a conventional exposure process. In the figure, ■ is a semiconductor substrate, 2 is a first wiring, 3 is an insulating film,
4 is a resist film, 5.6 is a reticle,
51 and 61 are glass substrates, 52 and 62 are thick chromium films,
63 is a thin chrome film, 65 and 66 are resist film patterns for forming a reticle, a is a semi-transparent part of the reticle, b is a transparent part, C is a shielding part, and A and B are window parts of the resist film 4. Agent Patent Attorney Hiroshi Matsuoka Part 4 Figure 2 Figure 3

Claims (1)

[Claims] A resist solution is applied to a substrate to be processed with steps to form a resist film, and then a semi-transparent pattern or a shielding pattern is aligned in the convex portion, and a transparent pattern or a shielding pattern is aligned in the concave portion. 1. A pattern forming method comprising the steps of: forming a resist film pattern by exposing the shielding portion pattern to light using a photomask aligned with each other.