JPS60206135A - Pattern forming process - Google Patents

Abstract

PURPOSE:To reduce the process number while performing minute patterning process similar to that of three layer resist system by a method wherein a sensitive silicon resin layer is provided with the functions of an interlayer and the topmost layer. CONSTITUTION:A substrate is coated with a resin for lower layer to form a lower layer. Firstly the lower layer is coated with a sensitive silicon resin to form an upper layer and then a pattern is formed into the upper layer by exposure and development processes. Secondly another pattern is formed by etching the resin of lower layer utilizing the first pattern as a mask. Normally silicon wafer is utilized as a substrate but not always limited to the same. Besides, any resin may be utilized for the lower layer as far as it is provided with the purity sufficient to manufacture seimconductor element. The sensitive silicon resin shall be provided with the functions of an intermediate layer and the topmost layer in the conventional three layer resist system as well as a mask for etching the lowermost layer in addition to the sensitivity. In order to meet such requirements, mixed resin of polyorganosiloxane and aromatic bisazide compound etc. may be utilized.

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 method for forming the butter 7, 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, it is difficult to suppress dimensional changes in resist patterns on wafers with rough step structures.
This has become more difficult as patterns become finer. Furthermore, problems have arisen in various exposure methods as the minimum dimensions are 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 resist It is no longer possible to increase the height to width ratio of the system.

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

For multilayer resist systems, see Solid State Technology, 74 ('1981) (SolidStat
e Technology 74 (1981))
An overview has been published in , but many other studies on this system have also been published. Currently, the most commonly attempted method is to use a three-layer resist system, with the bottom layer having the role of flattening the steps on the substrate and preventing reflections from the substrate, and a mask for etching the bottom layer. It consists of an intermediate layer which functions as a photosensitive layer and a top layer which acts as a photosensitive layer. However, compared to the single Jn resist method, this three-layer resist system has the advantage of being able to perform fine flapping, but has the disadvantage of increasing the number of steps required for pattern formation. .

[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]

In order to eliminate the above-mentioned drawbacks, the present inventors have made extensive studies and found that the photosensitive silicone resin layer has both the functions of the intermediate layer and the top layer in the three-layer resist system. This led to the development of a layered resist system.

Namely, in the pattern forming method of the present invention, a lower layer resin is applied onto a substrate to form a lower layer, a photosensitive silicone resin is then applied onto the substrate to form an upper layer, and then exposure is performed.
The method is characterized in that a pattern is formed in the upper layer by development, and then the pattern is formed by etching the resin in the lower layer using the pattern as a mask.

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, a solution of a photosensitive silicone resin dissolved in a solvent is applied thereon, and then the layer is dried.

Next, a predetermined pattern is formed by exposing, developing and drying the lower layer resin according to a conventional method.

As the substrate, silicone urethane 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 photosensitive silicone resin serves as both the middle layer and the top layer in a conventional three-layer resist system, functions as a mask for etching the bottom layer, and must also be photosensitive. Therefore, in the present invention, the photosensitive silicone resin is a mixed resin of a polyorganosiloxane and an aromatic bisazide compound, a polyorganosiloxane containing an acryloyl group into which a photosensitive group has been introduced, a polyorganosiloxane containing an azide group, or a polyorganosiloxane containing an acryloyl group and an azide group. A polyorganosiloxane containing is used.

(1) (II) (river) (In the formula, R+ may be the same or different,
Examples include those having repeating units (1), (It) and/or (III) represented by (representing an organic group) and whose terminal end is terminated with a triorganosiloxy group. This (1), (I
The proportions of f) and (III) in the polymer are not particularly limited, but those having a degree of polymerization of 900 to 12,000 are usually used. Examples of the organic group R include aliphatic or aromatic hydrocarbon groups such as methyl, vinyl, and phenyl.

The aromatic bisazide compound is not particularly limited, but examples include 7Ii'4, 4'-diazide chalcone, 2.
6-bis(4'-azidobenzal)cyclohexa/7,
2.6-bis(4'-azidobenzal-4-methylenecyclohexanone, 1,3-bis(4'-azidobenzal)-2-flovanone, 1,3-bis(4'-azidocinnamylidene)-2- Propanone, 4,4'-diazidostilbene, 4,4'-diazidobiphenyl, 4,
Examples include 4'-diazido diphenyl sulfide, 3,3'-diazido diphenyl sulfite, 4,4'-diazido diphenyl sulfone, 3゜3'-diazido diphenyl sulfone, 4,4'-diazido stilbene, etc. It will be done. These are used alone or in a mixed system, and are usually 1 to 50% by weight, preferably 1% by weight, based on the polyorganosiloxane.
d3 to 30% by weight is blended.

When a mixture of polyorganosiloxane and aromatic bisazide compound is used, additives such as a sensitizer may be added. Sensitizers include, but are not limited to, benzophenone, 1-nitrobeylene, i,s-dinitropyrene, 5-nitroacenaphthene, and trinitrofluorenone. These sensitizers are used alone or in a mixed system, and the amount of sensitizers is usually 0 to 1 with respect to the aromatic bisazide compound.
It is blended in an amount of 50% by weight, preferably 0 to 20% by weight.

As acryloyl group-containing polyorganosiloxane,
For example, the following formula: %Formula% (In the formula, each R may be the same or different and represents an aliphatic or aromatic hydrocarbon group such as methyl or phenyl; l is an integer from O to 50; 1m is from 1 to An integer of 50, n is 1~
Examples of the compounds shown in Table 1: j) are shown in Table 1.
Volume 16, No. 3, pp. 131-136.

1976, etc.]. Note that the above polymer may be a compound in which an organosilyl group and an acryloyl group-containing silyl group are randomly copolymerized. A specific example of the compound is a compound represented by the following formula 2.

On the other hand, as azide group-containing polyorganosiloxane,
For example, the following formula: (wherein BS may be the same or different,
Represents an aliphatic or aromatic hydrocarbon group such as methyl or phenyl; O is an integer of 0 to 50, p is an integer of 1 to 50, and q is an integer of 1 to 12). [See the above-mentioned literature, etc.].

The above polymer may also be a compound in which an organosyl group and an azide group-containing silyl group are randomly copolymerized. A specific example of the compound is a compound represented by linear formula 20.

As the above-mentioned acryloyl group- or azide group-containing polyorganosiloxane, any photosensitive polyorganosiloxane containing the above functional group can be used. Furthermore, a photosensitive polyorganosiloxane containing both of the functional groups described above may be used. These acryloyl group- and/or azide group-containing polyorganosiloxanes can be used in combination with the aromatic bisazide compound, and may also be blended with additives such as polymerization initiators and sensitizers. Examples of the polymerization initiator include compounds such as benzophenone, benzoin isopropyl ether, and xanthone.
% by weight is added. As the sensitizer, for example, the above-mentioned sensitizers are used, and the photosensitive silicone resin is usually exposed to O.
~30% by weight is added.

The lower layer resin and photosensitive silicone resin described above are applied after being dissolved in a solvent, but such solvents are not particularly limited, and examples include toluene, xylene,
-') Chlorobenzene, chloroform, ethanol, isopropyl alcohol, cyclopentanone, cyclohexanone, cellosolve acetate, and methyl ethyl ketone. Further, the coating method is performed according to a conventional method, but preferably a spin code method is adopted.

After applying the above resin, it is dried, but the drying conditions are as follows.
In the case of lower layer resin 1 Usually 50 to 250°C, preferably 80°C
~220°C for 1 usually 0.5 to 120 minutes, preferably 1
~90 minutes, and in the case of photosensitive silicone resins, the temperature is usually 50 to 200°C, preferably 80 to 120°C.
-120 minutes, preferably 1-60 minutes.

Next, the photosensitive silicone resin layer is exposed to light through a mask with a predetermined pattern, and the N light is irradiated with visible, infrared, ultraviolet light, or energy rays such as electron beams according to a conventional method.

After that, it is developed with a solvent. Development time is usually 0.5-1
The duration is 0 minutes, and an appropriate solvent such as acetone is used as the solvent. Next, it is usually 50 to 200℃ and 05 to 120℃.
Let dry for a minute. Finally, the lower layer is etched using oxygen gas plasma or a suitable solvent to obtain a J:υ predetermined resist pattern. Note that etching is preferably performed using oxygen gas plasma. In this case 1 usually 1×10
-4~l X 10-'Torr10.01~l OW
/(yl) for 1 to 120 minutes.

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

〔Effect of the invention〕

According to the present invention, forming a predetermined resist pattern 1
Although the number of steps required is small, it is possible to achieve the same fine patterning as the 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.

Furthermore, since there is no need to form an intermediate layer, the effort of transferring the pattern of the photosensitive layer to the intermediate layer using, for example, CF4 plasma can be omitted.

[Embodiments of the invention]

Example 1 A solution of novolak resin dissolved in cellosolve acetate was applied onto a bricone wafer using a spinner, and dried at 220° C. for 1 hour to form a lower IA.

Its thickness was 18 μm. The polysiloxane has a polymerization degree of 4500. The ratio of the repeating units of (1), (■) and (1) is %80:15:5%, the organic groups are 99% methyl groups and 1% vinyl groups, and the aromatic bisazide compound is 2%. , 6-bis(4'-azidobenzal)-4-methylcyclohexanone was added in an amount of 5 parts by weight based on the polysiloxane, and 1-nitropyrene was added as a sensitizer in an amount of 10 parts by weight based on the bisazide compound. - Cellosolve acetate was dissolved in a mixed solvent, and the resulting solution was applied using a spinner, and then dried to form an upper layer of 0.3 μm thick. This material was exposed for 1 second through a 1 μm line IN mask using an exposure machine using a 300 W ultra-high pressure mercury lamp. While bathing this in acetone,
The film was developed for 1 minute and dried at 100°C for 30 minutes. Next, oxygen gas plasma? (2, Ox 10-2 Tor
As a result of etching for 30 minutes at r + , 0.06 W/cffl), a pattern with a line width of 1 μm was formed.

Examples 2 to 7 The same operations as above were carried out, except that the aromatic bisazide compound and the compound shown in the following table were used as the sensitizer in the same amounts as in Example 1.

Even using the above, a pattern with a line width of 1 μm was formed as in Example 1.

Example 8 In Example 1, instead of the polysiloxane and bisazide compound used in the upper layer, acryloyl-based photosensitive silicone of the formula (1) was used, and 1% by weight of penzoin isoglobyl ether was added as an initiator. was used to form a pattern.

As in Example 1, three patterns with a line width of 1 μm were formed.

Example 9 In Example 8, a pattern was formed using the azide photosensitive silicone of the formula V instead of the acryloyl photosensitive silicone and adding 5% by weight of 5-nitroacenaphthene as a sensitizer. .

As in Example 1, a pattern with a line width of 1 μm was formed.

Claims (3)

[Claims] (1) A lower layer resin is applied on the substrate to form a lower layer, 1. A photosensitive silicone resin is then applied on the lower layer to form an upper layer, and then a pattern is formed on the upper layer by exposure and development. . Next, using the pattern as a mask, the underlying resin is etched to form the entire pattern. (2) The pattern forming method according to claim 1, wherein the photosensitive silicone resin is a mixed resin of polyorganosiloxane and an aromatic bisazide compound. (3) The pattern forming method according to claim 1, wherein the photosensitive silicone resin is an acryloyl group-containing and/or azide group-containing polyorganosiloxane.