JPS61260242A - Formation of resist pattern - Google Patents

Abstract

PURPOSE:To eliminate swelling and to execute a developing process without the generation of scum by adding a poor solvent to a good solvent of polymethylsilsesquioxane (PMSS) at the highest possible ratio within a range where the development residues are not formed. CONSTITUTION:After a lower layer resist is provided on an Si substrate, a 4-methyl-2-pentanone soln. of PMSS is coated thereon and is prebaked to form an upper layer resist. A pattern is drawn thereon and thereafter the substrate is immersed in a soln. mixture composed of 4-methyl-2-pentanone and ethanol and is developed, then the substrate is immersed in isopropanol and is subjected to a rinse treatment. The upper layer resist is thereby developed and the PMSS pattern having no scum is formed on the lower layer resist at 0.3mum line and space.

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] Polymethylsilsesquioxane used as an upper layer resist in a two-layer resist for electron beam lithography swells during development and tends to generate scum.

The present invention eliminates the generation of scum and obtains a highly accurate resist pattern by performing development using a mixed solution of a good solvent and a poor solvent.

[Industrial application field]

The present invention relates to a developer composition for an upper layer resist for a two-layer structure.

Semiconductor devices are becoming more highly integrated, from ICs to LSIs.
Also, although the capacity has increased from LSI to VLSI,
This has been realized through advances in thin film formation technology and photolithography (IJ lithography).

Photo etching technology involves coating a resist on the substrate to be processed using a method such as a spin code method, and exposing it to ultraviolet rays through a mask, so that the exposed area is exposed to the developer. A resist pattern is formed by taking advantage of the difference in solubility.

Here, there are two types of pattern forming molds: a negative type in which the light part is insoluble in the developer, and a positive type in which the light part is soluble.

Now, in the conventional pattern formation method using ultraviolet light exposure, the minimum pattern formation is 0.7μ due to wavelength limitations.
It is limited to m lines and spaces, and it is difficult to form a pattern with a line width of substantially 1 μm or less.

However, pattern formation of LSI-PVLSI requires pattern formation of submicron width, and there is a demand for practical application of this formation technology.

On the other hand, the wavelength of an electron beam varies depending on the accelerating voltage, but is about 0.1 nm, which is more than 4 orders of magnitude smaller than the wavelength of light, so it can be expected to have great resolution, and it is also possible to form patterns with a width of 0.1 μm. Become.

Therefore, electron beam lithography is used instead of conventional ultraviolet lithography to form submicron patterns.

[Conventional technology]

Negative resists used in electron beam lithography include chloromethylated polystyrene and cyclized polyisoprene.
A resist pattern is formed by coating the film with a thickness of μm, scanning it with an electron beam to draw a fine pattern, and developing it.

However, with such a single-layer resist, when a pattern is drawn, electrons are reflected and scattered by a substrate to be processed (hereinafter referred to as a Si substrate) made of silicon (Si), so that fine patterns cannot be drawn.

Therefore, a resist with a two-layer structure that is less susceptible to electron scattering was developed.

The lower resist forming the two-layer structure must have excellent solvent resistance after the heat curing process and dry etching resistance against halogen plasma, such as novolak resin. and epoxy resin copolymers.

On the other hand, the upper cyst layer must have good sensitivity to electron beams, excellent resolution, and excellent dry etching resistance to oxygen (02) plasma.

In other words, in electron beam lithography using a two-layer resist, the upper resist is removed by chemical etching except for the portions exposed and polymerized by electron beam scanning, and then the lower resist is opened using oxygen plasma using the upper resist pattern as a mask. Next, a two-layer resist pattern consisting of an upper layer resist and a lower layer resist is used as a mask.
, which performs dry etching of a Si substrate using logen plasma.

From this point of view, it is inappropriate to use the above-mentioned chloromethylated polystyrene, cyclized polyisoprene, etc., which are used as a layer resist, as an upper layer resist because of poor dry etching resistance. The authors propose the use of polymethylsilsesquioxane (hereinafter abbreviated as PMSS).

However, silicone resists such as PMSS have the problem of generating scum around the resist pattern after development, impairing resolution, and countermeasures have been required.

[Problem that the invention seeks to solve]

As explained above, when PMSS is used as the upper layer resist of a two-layer resist used in electron beam lithography, scum tends to form on the resist pattern after the development process is completed, which causes a problem in resolution. .

[Means for solving problems]

The above problem can be solved by adopting a resist pattern forming method characterized in that the PMSS developer used for the two-layer structure resist of electron beam lithography consists of a combination of a good solvent and a poor solvent for the PMSS. can.

[Effect]

The reason why scum is likely to occur after development when PMSS is used as the upper layer resist of a two-layer resist is that swelling occurs during the development process.

Therefore, the present invention aims to eliminate swelling and perform a development process without generating scum by adding a poor solvent to the good solvent of PMSS in an amount as large as possible without producing development residue.

Here, good solvents for PMSS include 4-methyl-2-pentanone, 2-butanone, isoamyl acetate, ethyl acetate, 1,4-dioxane, etc., and poor solvents include cyclohexanone, acetone, Examples include isopropanol, ethanol, methanol, acetonitrile, benzyl alcohol, etc.

The figure shows the optimal mixing range with a poor solvent when 4-methyl-2-pentanone is used as a good solvent. Taking isopropanol as an example, the mixing ratio of 4-methyl-2-pentanone is 20 If the amount is 100% by volume or less, development of PMSS is possible, but as the mixing ratio of 4-methyl-2-pentanone increases, swelling will occur, while if it is less than 20% by volume, development cannot be performed.

Therefore, the optimal developer that does not produce scum is 4-methyl-2
-Mixing specific strength of pentanone and isopropanol: 20:
The optimum case is 80% by volume.

〔Example〕

Positive photoresist on Si substrate) 0FPR-800 (
(manufactured by Tokyo Ohka Co., Ltd.) was coated to a thickness of about 2 μm by a spin code method, and heated and cured at 200° C. for 1 hour to form a lower resist.

Next, add PMSS (weight average molecular weight is 3300
A 4-methyl-2-pentanone solution with a 0° dispersion degree of 1.36) was applied to a thickness of 0.2 μm using a spin code method, and prebaked at 80°C for 20 minutes in a N2 stream to form an upper resist layer. did.

After drawing a pattern on the sample using an electron beam with an accelerating voltage of 20 KV, it was developed by immersing it in a mixture of 4-methyl-2-pentanone and ethanol (volume ratio 1:1) for 30 seconds, and then isopropyl A rinsing treatment was performed by immersing the tool in the tool for 30 seconds.

Through the above process, the upper resist layer was developed, and a scum-free PMSS pattern with 0.3 μm line and space could be formed on the lower resist layer.

〔Effect of the invention〕

As explained above, by carrying out the present invention, there is no swelling,
Therefore, it is possible to perform PMSS development without generating scum.

[Brief explanation of the drawing]

The figure is an explanatory diagram showing the developable range when 4-methyl-2-pentanone is used as a good solvent. Yu

Claims (1)

[Claims] Formation of a resist pattern characterized in that a polymethylsilsesquioxane developer used for a two-layer structure upper layer resist in electron beam lithography is a mixture of a good solvent and a poor solvent for the polymethylsilsesquioxane. Method.