JPS60254035A - Formation of pattern - Google Patents

Abstract

PURPOSE:To enhance dry etching resistance without impairing sensitivity and resolution property by using 2-layer resist films composed of upper and lower layers each made of a specified substance in forming a negative type resist pattern by using ionizing radiation rays. CONSTITUTION:The lower resist layer made of a material etchable with oxygen plasma and high in dry etching resistance is formed on the layer to be worked, such as a silicon wafer, and then on this layer, the upper layer made of polysilsesquioxane represented by formula (I), R1-R4 are independent of each other, each of them is phenyl, halophenyl, or halomethylphenyl, and at least one of them is halophenyl or halomethylphenyl, and n is a polymn. degree. A resist pattern is formed in the upper layer by patternwise exposing the upper layer to ionizing radiation, such as electron beams, X-rays, or ion beams, and developing it. The pattern is transferred to the lower layer by etching the lower layer by using this pattern of the upper layer as a mask. The lower layer is made of a phenol, polyimide, or polystyrene resin, or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to lithography technology using ionizing radiation such as electron beams, X-rays, and ion beams.

More specifically, the present invention relates to a method of irradiating a two-layer resist material with ionizing radiation as described above to form a negative resist pattern as a result of exposure and development.

BACKGROUND TECHNOLOGY In the manufacturing of semiconductor devices, especially large-scale integrated circuits (LS
It is well known that high dimensional accuracy is required when manufacturing items such as I). However, when pattern formation is performed using a normal single-layer resist film, if there are unevenness or other steps on the base of the resist film, the ionizing radiation for turning will be reflected from the adjacent pattern on the base. Inconveniences occur, such as radiation scattering within the cyst film and the thickness of the resist film becoming inconsistent, resulting in a wavy surface, resulting in a significant drop in pattern accuracy.

Furthermore, polyglycidyl methacrylate, poly(glycidyl methacrylate-coethyl acrylate), halogenated acrylate, epoxidized polybutadiene, etc., which are widely known as negative resists for electron beams and ), generally have poor dry etching resistance. Therefore, for example, aluminum, aluminum alloy, silicon dioxide (
When semiconductor wiring materials such as 51o2) are microfabricated by dry etching or etching, problems occur such that the resist disappears before the etching is completed or the edges of the resulting wiring pattern become moth-eaten.

In order to improve the dry etching resistance of the resist, attempts have also been made to introduce a large amount of aromatic rings into its molecular structure. However, in the case of this type of resist, a new problem has arisen in that the sensitivity is significantly lower than in other cases. Although attempts have been made to increase the thickness of the resist, it has not been possible to overcome the decrease in resolution.

Problems to be Solved by the Invention As is clear from the above, it is desirable to improve dry etching resistance without impairing sensitivity and resolution when forming a negative pattern by irradiating a resist material with ionizing radiation. Further, even if there is a level difference such as unevenness on the base of the resist film, it is desirable that the presence of such a level difference does not cause a significant decrease in pattern accuracy. The present invention seeks to solve these problems.

The present inventors have recently discovered, as a means to solve the above-mentioned problems, a polysilsesquioxane represented by the following formula: phenyl group, )\tetragenated phenyl group or halomethylated phenyl group, respectively, provided that at least one of these groups is a saponified phenyl group or a halomethylated phenyl group, and n is A negative resist pattern is formed by irradiation with ionizing radiation using a two-layer resist film consisting of an upper layer consisting of a material (indicating the degree of polymerization) and a lower layer consisting of a material that can be etched by oxygen plasma and has high dry etching resistance. We have discovered a pattern forming method that is characterized by the following.

The method discovered by the present inventors consists in forming a first resist layer (
This lower layer is made of a material that can be etched and etched with oxygen plasma and has high dryer and etching resistance.)
is formed, and the formula (I) is further formed on this lower resist layer.
) A second resist layer made of polysilsesquioxane (this upper resist layer acts as a negative resist) is formed, and the resulting two-layer resist layer is exposed to electron beams, X-rays, Ionizing radiation such as an ion beam is irradiated in a desired image pattern, the unexposed portion of the upper layer is dissolved and removed by development to obtain a resist pattern, and the lower resist layer below is etched using oxygen plasma using this resist pattern as a mask. Therefore, the pattern forming method includes a step of transferring the same pattern as the upper resist layer to the lower resist layer.

In the practice of the present invention, any of the polysilsesquioxanes represented by formula (I) above can be advantageously used as the top-layer resist. These polysilsesquioxanes have a halogenated or halomethylated phenyl group such as a chlorophenyl group or a chloromethylphenyl group in each repeating unit, resulting in polysilsesquioxanes containing only unsubstituted phenyl groups. It has a significantly higher sensitivity to flashes of ionizing radiation than the These polymers also have a higher softening temperature than conventional linear silicone resins, and therefore do not suffer from deformation or flow of patterns due to heat generated by irradiation with ionizing radiation.

The polysilsesquioxane used in the present invention typically has a molecular weight (MW) of about 5. ODD~100, D,
00, and the degree of dispersion (My/Mn) is approximately 1.0 to 4.
Advantageously, it is 0. Outside the above range, the resolution of resist patterns formed from these polymers will be reduced. Furthermore, the total halogenation rate or halomethylation rate of the phenyl groups contained in the repeating units is advantageously from 5 to 100% of the total phenyl groups.

If this ratio goes around 5%, it will not be possible to obtain satisfactory sensitivity.

The described polysilsesquioxane can be prepared according to conventional methods, for example, in JP-A-55-50645 and JP-A-53-880.
R can be manufactured by modifying the methods described in Japanese Patent Application Laid-open No. 99, Japanese Patent Application Laid-open No. 50-139900, Japanese Patent Application Laid-open No. 111197-1980, and the like.

These polymers can be further processed by subjecting polyphenylsilhepta-squioxane to halogenation using N-bromosuccinimide or N-chlorotetrasuccinimide, or chloromethylation using Friedel-Crafts reaction using chloromethyl ether. It can also be prepared.

There are various materials for forming the lower layer that can be etched by oxygen plasma and have high dry etching resistance.

Commonly useful materials include positive photoresists, phenol resins, polyimide resins, and polystyrene resins commercially available from Silaplay Corporation in the United States under the AZ series. Among these numerous sublayer-forming substances,
You can arbitrarily select one that suits your desired results.

In the practice of the invention, it is advantageous to construct the top layer of the two-layer resist film to be thinner and the bottom layer to be thicker. As a result of thinning the upper layer, combined with the full use of polysilsesquioxane as the upper layer resist, excellent sensitivity and resolution can be achieved, and this excellent upper layer resist pattern? As a result of transferring to a thick lower layer with excellent dry etching resistance, good dry etching resistance can also be achieved.

Furthermore, since the lower layer is a thick film, it is also possible to flatten steps such as unevenness in the layer to be processed. Preferably, the upper layer
The thickness of the upper layer is #JO, 1 to 0.5 μm, and that of the lower layer is about 1.5 to 6.0 μm.

EXAMPLES The following examples further illustrate the patterning method according to the invention.

In this example, a resist film having a two-layer structure shown by the l17r plane in FIG. 1 was prepared.

A positive type photoresist AZ-135DJ manufactured by Sheapley, Inc., USA was applied to a silicon wafer with a film thickness of 2.5 μm, and this was cured by heating at 2000 °C for 1 hour. Polysilsesquioxane (
MW=3.5X10.

MW/M111=2. s, chlorophenylation rate = 5
The upper layer 6 (film thickness: 05 μm) was formed by applying a toluene solution of 0%) and heating at 80 C for 20 minutes.

The silicon wafer with the two-layer resist film prepared as described above (see Figure 1) was filled into an electron beam exposure device,
A line space pattern of 1 μm was drawn under conditions of an accelerating voltage of 20 V and an electron beam exposure dose of 10 μa. In FIG. 2, the exposed area of the upper layer is indicated by 3'. After exposure to an electron beam, development was performed for 60 seconds with an isostatic mixture of methyl ethyl ketone and isopropyl alcohol to dissolve and remove the unexposed area of the upper layer, and a pattern as shown in FIG. 3 was obtained. Next, this wafer was placed in a parallel plate dryer.
filling the inside of the cutting device, and using the remaining upper layer 6' as a mask, the lower layer 2'? I dry etched it. For this etching, oxygen as a reactive gas was heated at a pressure of 15 m'L'o.
rrS power 0.25 W/crI and applied frequency 13-
It was applied for 20 minutes at 56 MHz.

After etching, a cross-sectional shape as shown in FIG. 4 was obtained. That is, the resist pattern 3' on the upper layer was hardly etched, and the pattern was transferred to the lower layer 2 as it was.

Effects of the Invention According to the present invention, the resist film has a two-layer structure and optimal resists are used for the upper and lower layers, thereby providing a pattern forming method that satisfies sensitivity, dry etching resistance, and resolution at the same time. According to the present invention, the lower layer of the resist film is made relatively thick, so that if the surface to be processed is not flat, it can be made flat.

[Brief explanation of drawings]

FIG. 1, FIG. 2, FIG. 3, and FIG. 4 are cross-sectional views sequentially showing the pattern forming method according to the present invention. In the figure, 1 is a silicon wafer, 2 is a lower layer, and 3 is an upper layer. i+++i Hi+

Claims (1)

[Claims] 1. Polysilsesquioxane represented by the following formula: (In the above formula, - R1, R2, R3 and R4 may be the same or different from each other, and each represents a phenyl group or a halogenated phenyl group. or a halo-methylated phenyl group, provided that at least one of these groups is a halo-methylated phenyl group or a ha-tetramethylated phenyl group, and n represents the degree of polymerization) and an upper layer formed by oxygen plasma, A pattern forming method comprising forming a negative resist pattern by irradiation with ionizing radiation using a two-layer resist film consisting of a lower layer made of a material that can be etched and has high dry etching resistance.