JPS62215945A - Pattern forming method - Google Patents

Abstract

PURPOSE:To form a fine pattern in a few stages by forming a prescribed photosensitive resin layer on a resin layer as a lower layer formed on a substrate and by carrying out exposure and development. CONSTITUTION:A resin for a lower layer is applied to a substrate to form a lower layer. A resin for an upper layer is applied to the lower layer to form an upper layer and this upper layer is patterned by exposure and development. The lower layer is then patterned by etching with the pattern of the upper layer as a mask. A photosensitive resin made of a copolymer of a silane having naphthyl bonded to Si with a silane having alkyl bonded to Si is used a the resin for the upper layer. The copolymer has 0.2-1.0 ratio of the number of repeating units of the silane having naphthyl bonded to Si to the number of repeating units of the silane having alkyl bonded to Si. A fine pattern comparable to that obtd. by a three-layered resist system is obtd. and the number of layer forming stages can be reduced.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Field of Application) The present invention relates to a pattern forming method, and more specifically, to a method for forming a fine resist pattern in the manufacture of integrated circuits of semiconductor devices. Concerning methods.

(Prior Art) Conventionally, as a 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, as the minimum processing dimensions have been reduced year by year, various problems have been pointed out regarding this single layer resist method.

That is, since the vertical dimension of an integrated circuit is not reduced as much as the horizontal dimension of the integrated circuit, the ratio of the height to the width of the resist pattern has to be large. For this reason, it has become more difficult to change the dimensions of a resist pattern on a wafer having a complicated step structure as patterns become finer.

Furthermore, problems have arisen with the reduction of the minimum dimension in various exposure methods.For example, in light exposure, the interference effect of reflected light due to the step difference in the substrate has a large impact on dimensional accuracy. On the other hand, in electron beam exposure, due to the proximity effect caused by back scattering of electrons,
It is no longer possible to increase the height-to-width ratio of a fine resist pattern.

It has been found that many of these problems can be solved by using a multilayer resist system (Solid State Technology, 74 (1981);
5tate Technology 7.74 (1981
)), and many other studies regarding this system have been published. Currently, the most commonly attempted method is a resist system with a three-layer structure, in which a mask is used to etch the bottom layer, which has the role of flattening the steps on the substrate and preventing reflections from the substrate. It consists of an intermediate layer which functions as a photosensitive layer and a top layer which acts as 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 problem of increasing the number of steps required to form a pattern.

(Problems to be Solved by the Invention) An object of the present invention is to provide a method of forming a pattern using a two-layer resist system, which can perform fine patterning equivalent to that of a three-layer resist system, and with a reduced number of steps.

[Structure of the Invention] (Means and Effects for Solving Problems) The pattern forming method of the present invention includes coating a lower layer resin on a substrate to form a lower layer, and then applying an upper layer resin on the lower layer. In this method, the resin for the upper layer is coated to form an upper layer, then exposed and developed to form a pattern on the upper layer, and then the upper layer pattern is used as a mask to etch the lower layer resin to form a pattern. is a photosensitive resin consisting of a copolymer of silane in which a naphthyl group is bonded to a silicon atom and silane in which an alkyl group is bonded to a silicon atom, and the naphthyl group is based on the number of repeating units of the silane in which an alkyl group is bonded to a silicon atom. is characterized in that the ratio of the number of repeating units of silane bonded to silicon atoms is from 0.2 to 10.

Although the substrate used in the present invention is not particularly limited, a silicon wafer is usually used.

The resin for the lower layer of the present invention may be any resin as long as it has a purity that does not cause problems in the production of semiconductor devices.For example, a positive resist consisting of substituted @-quinonediazide and a novolac resin, polystyrene, Mention may be made of polymethyl methacrylate, polyvinylphenol, novolak resin, polyester, polyvinyl alcohol, polyethylene, polypropylene, polybutadiene, polyvinyl acetate, polyvinyl butyral, polyimide resin, and polyamide resin.

Each of these can be used alone or in a mixed system of at least two or more types, and has the function of flattening steps on the substrate and preventing reflection from the substrate.

The upper layer resin of the present invention is a photosensitive resin made of a copolymer of a silane in which a naphthyl group is bonded to silicon and a silane in which an alkyl group is bonded to a silicon atom.

In this copolymer, the silane in which a naphthyl group is bonded to a silicon atom is a repeating unit represented by , other substituents have 1 to 13 carbon atoms
is an alkyl group or an aromatic group).

Examples of the derivatives of 1-naphthyl group and 2-naphthyl group in formula (I) include 6-medoxy-1-naphthyl group and 6-methyl-2-naphthyl group. Further, examples of the aromatic group include phenyl group, methylphenyl group, methoxyphenyl group, ethylphenyl group, dimethylphenyl group, and benzyl group.

On the other hand, silane in which an alkyl group is bonded to a silicon atom is a repeating unit represented by is a derivative).

Examples of the phenyl group derivative in formula (II) include methylphenyl group, methoxyphenyl group, ethylphenyl group, dimethylphenyl group, and benzyl group.

The quantitative relationship between repeating unit (1) and repeating unit (II) in this copolymer is 0.2≦A/B≦10, where A is the number of the former and B is the number of the latter. is necessary. By limiting the wavelength to this range, ultraviolet absorption is extended toward longer wavelengths, and the absorbance is increased.

A copolymer composed of the above-mentioned repeating units is produced by, for example, a Wurtz reaction.
-1000 parts by weight, 4 to 1 based on the number of moles of monomer
Mix 2 moles of dispersed sodium and add 100% by standard method.
Polymerize at 130°C. The solvent used at this time is preferably toluene or xylene.

The number average molecular weight of these polymers is usually 500 to i,oo
This average molecular weight, which is preferably o, ooo, is
If it is less than 500, a coating film cannot be formed, and 1.000.000
This is because if it exceeds this amount, it becomes difficult to dissolve in the solvent. From the point of view of solubility and sensitivity, preferably 1,000 to 30
,000.

Further, these copolymers may be either random copolymers or block copolymers.

The resin for the upper layer thus obtained functions as both the intermediate layer and the uppermost layer in a conventional three-layer resist system, acts as a mask for etching the lowermost layer, and is photosensitive.

Pattern formation according to the present invention is performed, for example, as follows.

That is, first, the resin for the lower layer is dissolved in a solvent such as toluene, xylene, 0-dichlorobenzene, chloroform, ethanol, isopropyl alcohol, cyclopentanone, cyclohexanone, cellosolve acetate, butyl acetate, methyl ethyl ketone, or the like.

The obtained solution is applied onto a substrate by a spin drying method. The thickness of the resin for the lower layer is 0.5 to 3, preferably 1 to 2. Dry for 1 to 90 minutes.

Furthermore, the resin for the upper layer is dissolved in the solvent.

The obtained solution is coated on the lower layer resin by the coating method described above. Its thickness is 0.2-1H1 preferably 0.5
~0.6μ. Then, 50-200°C, preferably 80-120°C; 0.5-120 minutes, preferably 1
Dry for ~60 minutes. Furthermore, the upper resin layer is exposed to light through a mask having a predetermined pattern. Exposure is carried out by irradiating energy rays such as visible, infrared, and ultraviolet rays or electron beams according to a conventional method.

After that, develop it. As a developer, acetone, dichloromethane, chloroform, ethanol, hexane,
Cyclohexane, toluene, xylene, petroleum benzene,
An organic solvent such as petroleum ether is used as appropriate. The development time is 0.1 to 110 minutes, preferably 0.2 to 2 minutes.

After development, it is dried by a spin drying method at 50 to 120°C for 0.5 to 120 minutes.

Finally, the lower layer is etched using oxygen gas plasma or a suitable solvent, preferably oxygen gas plasma.

In this case, usually lX104 to lXl0″' Torr
, 0.01 to IOW/cm for 1 to 120 minutes.

(Example) Example 1 A solution of novolac resin dissolved in cellosolve acetate was applied onto a silicon wafer using a spinner, and heated at 220°C.
was dried for 1 hour to form a lower layer. Its thickness is 2.0
Polymer 20i having the structure shown in formula 0 which was JJJl
A photoresist was prepared by dissolving 450 parts of cyclohexanone in 450 parts of cyclohexanone.

(n:m=+2:1) This was applied onto the lower layer using a spinner and dried on a hot plate at 90° C. for 2 minutes to form a 0.4 μm photosensitive coating film. After that, it was exposed to monochromatic light of 313 nm and developed for 45 seconds using 1 petroleum benzene as a solvent.
A resist pattern was formed on the upper layer by drying at ℃ for 30 minutes.Then, using the pattern formed on this upper layer,
2X IO' Torr, 0, 06 W/crd
(1) As a result of etching the lower layer for 30 minutes using -cm elementary plasma, a pattern of lines 1tJ0.6u was formed.

Example 2 A pattern was formed in the same manner as in Example 1, except that a polymer having the structure shown in Formula 2 was used as the photosensitive resin and the thickness of the photosensitive coating was 9.3IJJ+. ,
A pattern with a line width of 0.6 μm was formed.

(n: m 1: l) Example 3 A pattern was formed in the same manner as in Example 1 except that a polymer having the structure shown in formula 3 was used as the photosensitive resin. A pattern was formed.

(n:m=1:1) Example 4 A pattern was formed in the same manner as in Example 1 except that a polymer having the structure shown in Formula 4 was used as the photosensitive resin. As a result, the line width was 0, lBa pattern was formed.

(n:m-2:1) [Effects of the Invention] As is clear from the above description, according to the present invention, even if the number of steps required to form a predetermined resist pattern is small, it can be compared with the conventional three-layer resist system. Fine patterning equivalent to that can be performed. Therefore, the number of resist layers required is one less than that of the conventional method, and the process required for forming the resist layer can be omitted, and the incidence of defective products is also reduced. Furthermore, since there is no need to form an intermediate layer, the labor of transferring the pattern of the photosensitive layer to the intermediate layer using, for example, CFa plasma can be omitted, which is of great industrial value.

Claims (1)

[Claims] A lower layer resin is applied on the substrate to form a lower layer, then an upper layer resin is applied on the lower layer to form an upper layer, and a pattern is formed on the upper layer by exposure and development, and further, In the method of forming a pattern by etching the lower layer resin using this upper layer pattern as a mask, the upper layer resin is composed of a silane in which a naphthyl group is bonded to a silicon atom and a silane in which an alkyl group is bonded to a silicon atom. It is a photosensitive resin made of a polymer, and the ratio of the number of repeating units of the silane having a naphthyl group bonded to the silicon atom to the number of repeating units of the silane having an alkyl group bonded to the silicon atom is 0.2 to 10. A pattern forming method characterized by: