JPS6271945A - Formation of pattern - Google Patents

Abstract

PURPOSE:To execute fine patterning equal to patterning of a 3-layer resist system by forming a resin for an upper layer of a photosensitive resin consisting of a polysilane in which an arom. ring having a hydroxyl group is bound with silicon atoms or photosensitive resin having -Si-O-O- bond. CONSTITUTION:A resin for a lower layer is coated on a substrate to form the lower layer, then the photosensitive resin consisting of the polysilane in which the arom. ring having the hydroxyl group is bound with the silicon atoms or the photosensitive resin consisting of a polymer having the -Si-O-O- bond is coated thereon to form the upper layer. The resin layers are thereafter exposed and developed to form the pattern on the upper layer. The resin of the lower layer is then etched with the pattern as a mask to form the pattern. The polysilane is exemplified by the homopolymer or copolymer having the repeating unit I or II expressed by formula I or II. On the other hand, the resin expressed by, for example, formula II is used as the photosensitive resin consisting of the photosensitive material and the polymer having the -Si-O-O- bond.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a pattern forming method, and more particularly to a method capable of forming fine resist patterns in the manufacture of integrated circuits of semiconductor devices.

[Technical background of the invention and its problems]

As a conventional pattern forming method, there has been a so-called single-layer resist method in which only one resist layer is formed on a wafer. However, in the manufacture of integrated circuits, the minimum processing dimensions have been reduced year by year, and various problems have been pointed out regarding this single-layer resist method.

That is, since the vertical dimension of an integrated circuit has not been reduced as much as the horizontal dimension of the integrated circuit, the ratio of the height to the width of the resist pattern has been forced to increase. For this reason, suppressing dimensional changes in resist patterns on wafers with complex step structures is difficult.
As the pattern becomes finer, it becomes more difficult. Furthermore, problems have also arisen in various exposure methods as the minimum dimension is reduced. For example, in light exposure, the interference effect of reflected light due to the step difference in the substrate has a large effect on dimensional accuracy, while in electron beam exposure, the proximity effect caused by back scattering of electrons causes fine It is no longer possible to increase the height-to-width ratio of resist patterns.

It has been found that many of these problems are overcome by using a multilayer resist system.

For multilayer resist systems, solid state
Technology, 74 (1981) (5olid
5tateTechr+oLogy, 74 (19
81)), but many other studies regarding this system have also been published. the current,
The most commonly attempted method is a three-layer resist system.

It consists of a bottom layer which has the role of flattening the steps of the substrate and preventing reflection from the substrate, an intermediate layer which functions as a mask for etching the bottom layer, and a top layer which is a photosensitive layer. However, while this three-layer resist system has the advantage of being able to perform fine patterning compared to the single-layer resist method, it has the disadvantage of increasing the number of steps required to form a pattern.

[Purpose of the invention]

An object of the present invention is to provide a pattern forming method that can perform fine patterning equivalent to that of a three-layer resist system and that requires fewer steps.

[Summary of the invention]

As a result of intensive studies aimed at solving the above-mentioned drawbacks, the present inventors have made it possible to form a resin layer that has both the functions of the intermediate layer and the upper layer in the three-layer resist system, and from this, the two-layer resist system of the present invention has been made possible. We have developed a method for forming patterns using resist.

That is, in the pattern forming method of the present invention, a lower layer resin is coated on a substrate to form a lower layer, and then a photosensitive resin made of polysilane in which an aromatic ring having a hydroxyl group is bonded to a silicon atom, or A photosensitive resin made of a polymer having a -5i-0-0- bond is applied to form an upper layer, and then exposed and developed to form a pattern on the upper layer, and then the pattern is used as a mask to form a lower layer. It is characterized by forming a pattern by etching the resin.

The present invention will be explained in more detail below.

In the present invention, a pattern can be formed, for example, by the following method. That is, first, the lower layer resin is dissolved in a solvent, and the resulting solution is applied onto the substrate. Next, the resin layer is dried, and a solution prepared by dissolving the resin for the upper layer in a solvent is applied thereon, and then the layer is dried. Next, a predetermined pattern is formed by exposing and developing, drying, and etching the lower layer resin according to a conventional method.

As this substrate, a silicon wafer is usually used, but there is no particular limitation.

Further, the resin for the lower layer may be any resin as long as it has a purity that does not cause any trouble in the manufacture of semiconductor elements. Examples of the resin include positive resists made of substituted 0-quinone diazide and novolak resin, polystyrene, polymethyl methacrylate, polyvinylphenol, novolak resin, polyester, polyvinyl alcohol, polyethylene, polypropylene, polybutadiene, polyvinyl acetate, and polyvinyl butyral. can be mentioned. These resins may be used alone or in a mixed system.

On the other hand, the top layer resin functions as a mask for etching the bottom layer to serve as both the middle layer and the top layer in a conventional three-layer resist system, and must also be photosensitive.

For this purpose, in the present invention, as the resin for the upper layer, a photosensitive resin made of polysilane in which an aromatic ring having a hydroxyl group is bonded to a silicon atom, or a photosensitive resin made of a polymer having a -Si-0-0- bond is used. use

This polysilane has the following formula: R engineering to R engineering are a hydroxyl group, a hydrogen alkyl group, or a vinyl group.

selected from an alkyl group, an alkoxy group, or an aromatic group, and at least one of R0 to R6, and R, to R1
At least one of 3 is a hydroxyl group.

Homopolymers or copolymers of the repeating unit (I) or (II) shown in the formula are exemplified. Examples of the copolymerized unit include the following. In addition to an organic solvent, an aqueous alkaline solution of tetramethylammonium hydroxide, choline, etc., is used as a developing solvent for the resin thus obtained. In addition, the molecular weight of these is 500 to 5oooooo, especially 1
A range of 000 to 30,000 is preferable from the viewpoint of solubility and sensitivity. These resins may be used alone or in a mixed system.

On the other hand, as a photosensitive resin made of a photosensitive substance and a polymer having -Si-0-0- bonds, for example, a resin represented by the following formula is used. As a solvent for the resin thus obtained, an organic solvent such as acetone is used. Further, the molecular weight of these resins is preferably in the range of approximately 1,000 to 30,000 from the viewpoint of solubility and sensitivity. These resins may be used alone or in a mixed system.

The resin for the lower layer and the resin for the upper layer described above are applied after being dissolved in a solvent, but the solvent is not particularly limited, and examples thereof include toluene and xylene.

0-dichlorobenzene, chloroform, ethanol, isopropyl alcohol, cyclopentanone.

Examples include cyclohexanone, cellosolve acetate, and methyl ethyl ketone. Further, although the coating method is carried out in accordance with the procedure described above, a spin code method is preferably adopted.

In addition, after coating the above resin, it is dried, and the drying conditions are usually 50 to 250 degrees Celsius, preferably 80 to 220 degrees Celsius, usually 0.5 to 120 minutes, preferably 1 to 90 minutes in the case of the lower layer resin. In the case of upper layer resin, it is usually 50
~200℃, preferably 80~120℃, usually 0.5~
The duration is 120 minutes, preferably 1 to 60 minutes.

Next, the upper resin layer is exposed to light through a mask having a predetermined pattern, and the exposure is carried out by irradiating visible, infrared, ultraviolet light, or electron beams in accordance with a conventional method.

After that, it is developed with a solvent. Development time is usually 0.5-1
0 minutes, and the solvent is tetramethylammonium hydroxide when the upper layer resin is made of the above-mentioned photosensitive resin made of polysilane.

Drying is usually carried out at 50 to 200° C. for 0.5 to 120 minutes using an aqueous alkaline solution such as choline or an organic solvent such as acetone. When the upper layer resin is a photosensitive resin made of a polymer having 15L-0-0- bonds, an organic solvent such as acetone is used as the solvent and the temperature is usually 50°C to 150°C. Dry for ~120 minutes.

Finally, a predetermined resist pattern is obtained by etching the lower layer using oxygen gas plasma or a suitable solvent. Note that etching is preferably performed using oxygen gas plasma. In this case, usually IX 10'-' ~ IX
1-12 at 10-”Torr, 0.01-IOW/cd
Process for 0 minutes.

By the above method, an integrated circuit of semiconductor elements is formed.

〔Effect of the invention〕

According to the present invention, although the number of steps required to form a predetermined resist pattern is small, it is possible to perform fine patterning equivalent to that of a conventional three-layer resist system. Therefore, the labor required for layer formation can be reduced by one less resist layer than in the past, and the rate of defective products is also reduced. In addition, since there is no need to form an intermediate layer, it is possible to eliminate the trouble of transferring the pattern of the photosensitive layer to the intermediate layer using, for example, CF4 plasma. Apply the solution dissolved in Cellsolve with a spinner.

It was dried at 220° C. for 1 hour to form a lower layer. Its thickness was 2.0 μm. A photoresist was prepared by dissolving 20 parts by weight of a polymer having a structure represented by formula [I[1] in 450 parts by weight of cyclohexanone.

H It was applied onto a silicon wafer using a spinner and dried on a hot plate at 90° C. for 2 minutes to form a photosensitive coating film with a thickness of 0.4 μm. After that, it was exposed to monochromatic light of 313 nm, and a tetramethylammonium hydroxide aqueous solution (
0.5%) as a solvent for 45 seconds and 200
A resist pattern was formed on the upper layer by drying at ℃ for 30 minutes. Next, using the pattern formed on this upper layer, oxygen gas plasma (2, OX 10-” To
As a result of etching the lower layer for 30 minutes at rr 0.06 W/ci), turns with a line width of 0.6 μm were formed.

Example 2 A solution of novolak resin dissolved in acetic acid Celsolve was applied onto a silicone wafer using a spinner, and the solution was heated at 220°C for 1 hour.
It was dried for a while to form a lower layer. Its thickness was 2.0 μm. A photoresist was prepared by dissolving 20 parts by weight of a polymer having the structure shown by formula [IV] in 450 parts by weight of cyclohexanone.

This was applied onto a silicon wafer using a spinner and dried on a hot plate at 90°C for 2 minutes to form a 0.3 μm photosensitive coating film. After that, it was exposed to monochromatic light of 365 nm, and a tetramethylammonium hydroxide solution (0
, 5%) as a solvent and developed for 45 seconds at 200°C.
A resist pattern was formed on the upper layer by drying for 30 minutes. Next, using the pattern formed on this upper layer, oxygen gas plasma (2,0×10-” Torr
As a result of etching for 30 minutes at 0.06 W/+ff1), a pattern with a line width of 0.6 μm was formed.

Example 3 A solution of novolac resin dissolved in acetic acid cellosolve was applied onto a silicone wafer using a spinner.

It was dried at 220° C. for 1 hour to form a lower layer. A photoresist was prepared by dissolving 20 parts by weight of a polymer having a structure shown in formula 6 [V] whose thickness was 2.0 μm in 450 parts by weight of cyclohexanone.

This was applied onto a silicon wafer using a spinner and dried on a hot plate at 90°C for 2 minutes to form a 0.3 μm photosensitive coating film. Thereafter, it was exposed to monochromatic light of 254 nm, developed for 45 seconds using petroleum benzine as a solvent, and dried at 200° C. for 30 minutes to form a resist pattern on the upper layer.

Next, using the pattern formed on this upper layer, oxygen gas plasma (2,0X10-2Torr O,06W/
cJ) for 30 minutes, the result was 0.6μ
A pattern with a line width of m was formed.

Example 4 A solution of novolak resin dissolved in acetic acid Celsolve was applied onto a silicone wafer using a spinner, and the solution was heated at 220°C for 1 hour.
It was dried for a while to form a lower layer. Its thickness was 2.0 μm. A photoresist was prepared by dissolving 20 parts by weight of a polymer having the structure shown by formula [VI] in 450 parts by weight of cyclohexanone.

This was applied onto a silicon wafer using a spinner and dried on a hot plate at 90°C for 2 minutes to form a 0.3 μm photosensitive coating film. Thereafter, it was exposed to monochromatic light of 254 nm, developed for 45 seconds using petroleum benzene as a solvent, and dried at 200° C. for 30 minutes to form a resist pattern on the upper layer. Next, using the pattern formed on this upper layer, oxygen gas plasma (2,0×10−
As a result of etching for 30 minutes at "Torr O, 06W/co?", a pattern with a line width of 0.6 μm was formed.

Example 5 A solution of novolak resin dissolved in acetic acid cellosolve was applied onto a silicone wafer using a spinner and dried at 220° C. for 1 hour to form a lower layer. Its thickness was 2.0 μm. A photoresist was prepared by dissolving 10 parts by weight of a polymer having the structure shown by the formula [V] and 10 parts by weight of the polymer having the structure shown by the formula [■] in 450 parts by weight of cyclohexanone.

This was applied onto a silicon wafer using a spinner and dried on a hot plate at 90°C for 2 minutes to form a 0.3 μm photosensitive coating film. After that, it was exposed to monochromatic light at 254 stops, developed for 45 seconds using petroleum benzine as a solvent,
A resist pattern was formed on the upper layer by drying at 200° C. for 30 minutes. Next, using the pattern formed on this upper layer, oxygen gas plasma (2.0X10-2
As a result of etching for 30 minutes at a Torr of 0.06 W/a7), a pattern with a line width of 0.6 μm was formed.

Agent Patent Attorney Norihiro Kenji Quantity Bamboo Flower Kikuo Handbook supplementary text (spontaneous) 116 staves 1 Otsu P28

Claims (1)

[Claims] (1) Applying a lower layer resin onto a substrate to form a lower layer, then applying an upper layer resin onto the lower layer to form an upper layer,
A method is provided in which a pattern is formed on the upper layer by subsequent exposure and development, and then the lower layer resin is etched using the pattern as a mask to form a pattern, wherein the upper layer resin is an aromatic ring having a hydroxyl group. A pattern forming method characterized in that the photosensitive resin is made of a polysilane in which is bonded to a silicon atom, or the resin for the upper layer is a photosensitive resin made of a polymer having a -Si-O-O- bond.