JPS62198855A - Formation of pattern - Google Patents

Abstract

PURPOSE:To prevent the formation of a reformed layer by mixing of an upper positive type UV resist and lower positive type far UV resist and to improve the accuracy of a pattern size by forming a PVA film between the lower positive type far UV resist film and the upper positive type UV resist film. CONSTITUTION:A polycrystalline silicone layer 2 is formed on a silicon substrate having steps and a positive type far UV resist material, for example, PMMA (polymethyl methacrylate) is coated thereon to form the positive type far UV resist film 3 which is the 1st film. After a heating treatment is executed, the PVA is coated on the film to form the PVA film 4 which is the 2nd film. A positive type photoresist material consisting of an ordinary novolak resin is then coated thereon to form the positive type UV resist film 5 which is the 3rd film. The film is then subjected to a heating treatment. The film is exposed with UV rays and is developed, by which the resist material in the exposed parts and the PVA film right thereunder are removed. The far UV rays are irradiated over the entire substrate surface and the film is developed with a toluene, by which the pattern consisting of the three layers is obtd. with the good dimensional retentivity in the step part.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for forming patterns on various semiconductor substrates in the production of semiconductor integrated circuits, and more particularly to a method for forming fine patterns on various semiconductor substrates having steps.

[Conventional technology]

Conventionally, P is a method for forming fine patterns on a semiconductor substrate having steps using a coating agent such as a resist.
CM (Portable Comformable
A method called "Mask" was proposed. This method is comprised of the steps shown in FIGS. 2(a) to 2(c). First, as shown in FIG.
A positive far-UV resist material such as PMMA (polymethyl methacrylate-1.
A UV resist material such as a normal novolac resin having a photosensitive range of 0 to 450 nm is applied to form a positive UV resist coating 5. Then 300-450n
A positive ultraviolet resist pattern 5a is formed only on the upper ultraviolet resist film using an exposure device that uses ultraviolet rays as a light source.
However, at this time, the lower deep ultraviolet resist film is not exposed to light because its sensitivity range is different. Thereafter, the entire surface of the semiconductor substrate is irradiated with sufficiently parallel deep ultraviolet rays having a wavelength of about 200 to 250 nm.

At this time, in the remaining portion of the upper ultraviolet resist I/coating, this portion absorbs the far ultraviolet rays and serves as a mask for the lower resist coating immediately below, so that the lower far ultraviolet resist coating is not exposed. On the other hand, in areas where the upper ultraviolet resist film does not remain, the lower resist film, which has been irradiated with deep ultraviolet rays and has a low molecular weight, is developed and removed using an appropriate solvent, resulting in a fine positive deep ultraviolet resist pattern 30. is obtained. The upper resist film may or may not be dissolved during development of the lower resist film.

[Problems to be Solved by the Invention] In the conventional PCM method described above, since the lower deep-UV resist film is not completely insoluble in the upper-layer UV resist material, a metamorphic layer is formed between the deep-UV resist films. is formed. This metamorphic layer has the disadvantage that the development speed is extremely slow for both UV resist and deep UV resist developers, and it is difficult to develop the lower deep UV resist film unless the metamorphic layer is removed by 02 plasma treatment. .

0□ Removal of the metamorphic layer by plasma treatment has the drawbacks of adding additional steps and reducing precision of fine patterns.

An object of the present invention is to provide a pattern forming method that can improve the accuracy of pattern dimensions without adding complicated steps.

[Means for solving problems]

The pattern forming method of the present invention includes the steps of forming a first coating made of positive deep ultraviolet rays on a semiconductor substrate having steps, either directly or through a film of a material different from the substrate, and applying PVA (PVA) on the coating. a step of forming a second film made of polyvinyl alcohol), a step of forming a third film made of an ultraviolet resist material on the second film, and a step of exposing and developing the third film. A step of forming a pattern by removing the exposed portion or unexposed portion of the third coating and the coating immediately below it, and irradiating the first coating with deep ultraviolet rays using the third coating pattern as a mask; and developing and removing the exposed portion of one coating to obtain a pattern consisting of the first, second, and third coatings.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings. FIGS. 1(a>-(c)) are sectional views shown in the order of steps for explaining an embodiment of the present invention.

First, as shown in FIG. 1 (a), a polycrystalline silicon layer 2 with a thickness of about 0.5 μm is formed on a silicon substrate with a step of about 0.5 μm, and a positive type silicon layer 2 is formed on the polycrystalline silicon layer 2. A far-UV resist material, such as PMMA (polymethyl methacrylate), is applied to a thickness of 1.5 μm to form a positive-type deep-UV resist film 3, which is the first film.Then, it is heated in a convection oven at 100° C. for 25 minutes. After heat treatment, PVA (polyvinyl alcohol)
was applied to a thickness of approximately 500 mm to form a polyvinyl alcohol coating 4, which is the second coating. Next, a positive photoresist material made of a normal novolac resin, such as 0FPR800C-35CP manufactured by Tokyo Ohka Co., Ltd., is applied to a thickness of 1.0 μm.
A third coating, positive type ultraviolet resist coating 5, was formed and heated at 100°C on a hot plate 1 at 60°C.
Heat treatment is performed for 0 seconds.

Next, as shown in FIG. 1(b), exposure is performed using an exposure device using ultraviolet light as a light source. Then, the resist material was developed for 50 seconds using a positive photoresist developer NMD-3 manufactured by Tokyo Ohka Co., Ltd., and the exposed portion of the resist material and the PVA coating immediately below it were removed. Incidentally, since the polyvinyl alcohol film is easily removed by the above-mentioned developer, it is desirable to form it as thin as possible as described above in order to prevent excessive dissolution.

Next, as shown in FIG. 1(c), the entire surface of the substrate is irradiated with parallel far ultraviolet rays, but the PMMA directly under the pattern 4a of the photoresist material is not exposed to the light because the pattern 4a absorbs the far ultraviolet rays. .

Then, by developing with toluene for 3 minutes, the low-molecular PMMA is removed by irradiation with deep ultraviolet rays, and the pattern consisting of the positive deep ultraviolet resist pattern 3a, the PVA pattern 4a, and the positive ultraviolet resist pattern 5a maintains its dimensions at the stepped portion. It can be obtained easily.

〔Effect of the invention〕

As explained above, in the present invention, by forming a PVA film between the lower positive deep ultraviolet resist film and the upper positive deep ultraviolet resist film in the PCM method, the upper positive UV resist and the lower positive deep ultraviolet Formation of metamorphic layer due to mixing with resist can be prevented, and 02
Since the step of removing the metamorphic layer by plasma treatment can be omitted, there is an effect that the precision of pattern dimensions can be improved.

[Brief explanation of drawings]

FIGS. 1(a) to (c) are cross-sectional views shown in order of steps to explain an embodiment of the present invention, and FIGS. 2(a) to (c) are cross-sectional views showing a pattern forming method using the conventional PCM method. FIG. 4 is a cross-sectional view shown in order of steps for explanation. DESCRIPTION OF SYMBOLS 1... Semiconductor base, 2... Polycrystalline silicon coating, 3
...Positive deep ultraviolet resist coating (first coating), 3
a...Positive deep ultraviolet resist pattern, 4...Polyvinyl alcohol film (second coating), 4a...Polyvinyl alcohol pattern, 5...Positive ultraviolet resist coating (third coating), 5a ...Positive UV resist pattern. Kaya ly! J'iFZ bacteria

Claims (1)

[Claims] A step of forming a first film made of a positive deep ultraviolet resist material on a semiconductor substrate having steps, either directly or through a film of a material different from the substrate; a step of forming a third film made of an ultraviolet resist material on the second film; a step of selectively exposing the third film; and a step of predetermined development. selectively removing exposed portions or unexposed portions of the third and second coating portions with a liquid to form a pattern of the third and second coatings; A pattern comprising the step of irradiating far ultraviolet rays using a mask, and then developing and removing the exposed portion of the first coating to obtain a pattern consisting of the first, second, and third coatings. How to form.