JPS6058463B2 - Pattern formation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pattern forming method using a resist exhibiting good sensitivity to electron beams and X-rays.

Conventionally, photolithography using ultraviolet light having a wavelength of 350 to 450 nTrl has been used as a method for forming circuit patterns for semiconductor integrated circuits and the like.

In addition, as the density of these device patterns increases, fine patterns with a photolithography limit pattern width of 2 μm to 30 μm or less are required, and for this purpose, lithography using electron beams or X-rays has been studied and proposed. . Polyglycidyl methacrylate (PGMA), glycidyl methane acrylate ethyl acrylate copolymer [P(GMA-EA)],
Glycidyl methacrylate styrene copolymer [p(GM
A-St)] and the like are well known.

Although these resists are satisfactory in sensitivity, they have drawbacks such as poor resolution and dry etching resistance. SUMMARY OF THE INVENTION An object of the present invention is to provide a pattern forming method capable of forming a pattern using a pattern forming material that does not have the above-mentioned drawbacks.

In order to achieve the above object, the present invention uses a chemically stable dicarboxylic acid diallyl ester polymer as a pattern forming material for electron beams and X-rays.

That is, the dicarboxylic acid diallyl polymer is an aliphatic dicarboxylic acid diallyl represented by the general formula...CH2=C
H-CH2-0C0(CH2)nC00-CH2-CH
■CH2... (where n = integer from 0 to 8) For example, diallyl oxalate, diallyl malonate, diallyl succinate, diallyl glutarate, diallyl adipate,
Diallyl sebacate or diallyl aromatic dicarboxylate represented by general formula (2) (where A is phenylene or naphthylene), such as diallyl phthalate, diallyl isophthalate, diallyl terephthalate, and others. Examples include diallyl carbonate and diallyl maleate.

Among these, a particularly practical material is an aromatic dicarboxylic acid diallyl polymer from the viewpoint of heat resistance, since resins having phenyl groups generally have high heat resistance.

In addition, the molecular weight (M2) of the polymer ranges from 5000 to 500.
00, the range of dispersity (Mw/Mn), which is the ratio of number average molecular weight (flat) to weight average molecular weight (Mw), is 1.0 to 2.5.
was found to be preferable in terms of resolution.

That is, according to photographic judgment, the weight average molecular weight Mw is 5.
When the resolution was evaluated using a sample of 0.000 or less, it was found that practical sensitivity could not be obtained and the ability to form a resist film was also low.

On the other hand, it has been found that when a material having a weight average molecular weight Mw of 50,000 or more is used, whiskers occur, the pattern becomes meandering, and the resolution of 1 μm is lost.

Furthermore, it was found that when a polymer containing a polymer having a molecular weight Mw of 300,000 or more was included, the pattern meandered significantly and whiskers were generated. Therefore, when using diallyl phthalate polymer as an electron beam or X-ray negative resist, the weight average molecular weight should be 50.
It was found that it was necessary to adjust it to a range of 00 to 50,000.

Furthermore, it has been found that high resolution can be obtained by adjusting the dispersity Mw/Mn to a range of 1 to 2.5. A general fractional precipitation method was used to adjust the molecular weight and dispersion of the diallyl phthalate polymer.

Diallyl phthalate polymer was converted into methyl ethyl ketone (MEK).
) at a concentration of 5%, add a predetermined amount of isopropyl alcohol (IPA), which is a non-solvent for the above polymer, to precipitate and remove the high molecular weight polymer, and then add a predetermined amount of isopropyl alcohol to the solution. The desired polymer was obtained by precipitation. The polymer used in the present invention is particularly Mw
Since it is necessary to remove molecules having a value of 300,000 or more, a polymer obtained as a precipitate by adding isopropyl alcohol in the first step cannot be used.

The molecular weight and degree of dispersion were controlled by the amount of isopropyl alcohol, which is a non-solvent. The molecular weight of the resist was determined by molecular weight distribution using high performance liquid chromatography, and calculated using the line segment method from a standard polystyrene calibration curve.

The drawing shows an example of a molecular weight distribution curve of a resist.

In the figure, A indicates a weight average molecular weight Mw = 2.67 x 10' and a number average molecular weight M which is similar in molecular weight and dispersity to the sample used in the example.
n=1.55×1011 dispersion KAw/Vn=1.72
The molecular weight distribution curve of a resist material obtained by dissolving diallyl phthalate polymer in 2-ethoxyethyl acetate to a concentration of 2% by weight and using it as a resist solution, and B is the average molecular weight Mw=
The molecular weight distribution curve of a resist of diallyl phthalate polymer having 4.23×101, Mn=6.67×1Cf3, and dispersity Mw/Mn=6.34 is shown.

Example 1 Diallyl phthalate having a weight average molecular weight (Mw) of 000 and a dispersity Vw/Mn of 1.6, which was subjected to molecular weight fractionation by the method described above, was converted into 2-ethoxyethyl acetate by 25%.
The resist solution was dissolved at a concentration of Wf%.

The allyl group content of the polymer was 60 mol%. This was applied by spin coating onto a Si wafer coated with thermally oxidized SiO2 (0.5 μM) to a dry film thickness of 1 μml.

In addition, 2-methoxyethyl acetate, cyclohexane, etc. can be used as the resist coating solvent.

This was prebaked at 80°C for 3 minutes in a nitrogen stream.
It was used as a sample. Prebaking temperature is preferably 60 to 80°C. This sample was accelerated at a voltage of 15K and a current of 10-7.
Exposure was performed with an electron beam of ~10-10A. After exposure, a mixed solvent of monochlorobenzene and isoamyl acetate (volume ratio monochlorobenzene/isoamyl acetate 2/3) was used as a developer, and the film was immersed for about a second at a solution temperature of 20° C. for development. As the rinsing liquid, acetic acid isoamyl alcohol, isopropyl alcohol, etc. can be used. The sensitivity of the resist material was 4.times.10@-6 CIcI at an exposure dose with a residual film rate of 50%.

Furthermore, when a grating pattern was drawn using an electron beam with a beam diameter of 0.4 μmφ, a rectangular grating pattern of 1 μm line/1 μm space or less could be obtained.

In addition, the sample coated with the above resist was electrochemically etched to a thickness of 4 μml using AlKd(7) X-rays (8.34A) as a master mask. Au/S with 0.9μm evaporated
] When a transfer pattern was created using a mask, the result was 200
A grating pattern having a rectangular shape of 1 μm line/1 μm space was obtained with the sensitivity of the 111j IC.

Example 2 The weight average molecular weight Mw of diallyl isophthalate was adjusted to 110001 and the dispersity Mw/Mn was adjusted to 1.6 in the same manner as in Example 1, and the resolution was evaluated in the same manner. A grating pattern with a line spacing of 1 μm or less was obtained.

Example 3 Diallyl terephthalate was adjusted to the same molecular weight and dispersion as in Example 1, and the resolution was evaluated in the same manner.
It was confirmed that a grating pattern of 1 μm line/1 μm space or less could be created using both electron beams and X-rays.

The diallyl phthalate polymer has dry etching resistance equivalent to that of AZ-1350J against plasma etching using CF4 gas.

As explained above, according to the present invention, a dicarboxylic acid diallyl ester polymer is subjected to molecular weight fractionation using a fractional precipitation method, and the weight average molecular weight (Mw) is 5000 to 50.
By using the fractionated polymer as a resist material for electron beam and It is possible to resolve grating patterns with end faces and create fine patterns.

[Brief explanation of the drawing]

The drawing is a molecular weight distribution map.

Claims (1)

[Claims] 1 The dicarboxylic acid diallyl ester polymer has a weight average molecular weight @Mw@ in the range of 5,000 to 50,000, and a dispersity, which is the ratio of the number average molecular weight @Mn@ and the weight average molecular weight @Mw@, of 1 to 2.5. A step of separating the dicarboxylic acid diallyl ester polymer and forming a resist film on a substrate;
A pattern forming method comprising the steps of: irradiating and exposing lines according to a pattern to be formed; and developing the exposed resist film.