JP2506952B2 - Fine pattern formation method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fine pattern forming material used when a semiconductor element or an integrated circuit is formed by patterning using an electron beam, and a fine pattern using the same material. The present invention relates to a forming method.

2. Description of the Related Art Conventionally, in the manufacture of ICs and LSIs, pattern formation is performed by photolithography using ultraviolet rays. High NA of stepper lens due to element miniaturization
Although the use of a short wavelength light source has been promoted, there is a disadvantage that the depth of focus becomes shallow. Also, LS
Electron beam lithography has come to be used with the miniaturization of the pattern size of the I element and the manufacture of ASICs. In electron beam lithography, there are drawbacks such as poor dry etching resistance of electron beam resist, deterioration of pattern accuracy due to proximity effect due to forward scattering and back scattering of electrons, and charge-up due to exposure electrons. A multi-layer resist process in which the function of the resist is divided into a photosensitive layer and a planarizing layer is an effective method in order to overcome these drawbacks. FIG. 3 is a view for explaining a multilayer resist process in electron beam lithography. To suppress the proximity effect, an organic film is used as the lower layer film 2 to 3 μ.
m thickness is applied and an inorganic film such as SiO ₂ or SO is used as the intermediate layer 22.
G (spin-on-glass) is applied, an electron beam resist 23 is applied on the upper layer, and an aluminum layer 24 is vapor-deposited thereon in an amount of about 100 Å in order to prevent charge-up (FIG. 3 (a)).
After the exposure, the aluminum layer is removed with an alkaline aqueous solution, and then developed (FIG. 3 (b)). Next, the intermediate layer 22 is dry-etched using this resist pattern as a mask (FIG. 3C), and then the intermediate layer 22 is used as a mask to form a lower layer film.
21 is dry-etched (FIG. 3 (d)).

By using the multilayer resist process as described above, a fine pattern can be formed with a high aspect ratio. However, a multilayer resist for depositing an aluminum layer or a SiO ₂ layer is not practical because the process becomes more complicated and there are problems such as contamination.

Among electron beam resists, polymethylmethacrylate (PMMA) is known to have the highest resolution, but its low sensitivity is a drawback. Therefore, in recent years, many reports have been made to increase the sensitivity of positive electron beam resists, for example, polybutyl methacrylate, a copolymer of methyl methacrylate and methacrylic acid, a copolymer of methacrylic acid and acrylonitrile. Positive type electron beam resists such as a copolymer of methyl methacrylate and isobutylene, polybutene-1-sulfone, polyisopropenyl ketone, and fluorine-containing polymethacrylate have been announced. In any of these resists, the electron-withdrawing group is introduced into the side chain, or a bond that is easily decomposed into the main chain is introduced so that the main chain can be easily cleaved by the electron beam. However, due to poor dry-etch resistance and charging due to insulation,
There is a problem such as the effect of up.

Also, there are polysiloxane and polysilsesquioxane type resists as a resist for a two-layer resist having a high dry etching resistance, but the sensitivity and resolution are not sufficient, and the effect of charge-up due to the insulating property, etc. There's a problem.

Problems to be Solved by the Invention As described above, the multilayer resist process with an aluminum layer is an effective method, but has problems such as complicated steps and aluminum contamination. In addition, the multilayer resist process excluding the aluminum layer has a problem of charge-up. Charge-up is a phenomenon in which exposed electrons accumulate in a resist, an intermediate layer, or a lower layer which is an insulator. Due to this charge-up effect, in electron beam lithography, major problems such as field butting and deterioration of alignment accuracy occur. This charge-up phenomenon is also observed in the single-layer resist, and like the three-layer resist, the field batting and the alignment accuracy are deteriorated.

That is, in electron beam lithography, the exposed electrons are scattered in the resist while not receiving energy, and stop at a depth of 1 to 1.5 μm from the resist surface, and charges accumulate in that region.
This accumulated charge bends the electron beam,
We thought that it would cause field batting and deterioration of alignment accuracy.

Further, the conventional two-layer resist has a problem that the sensitivity and the resolution are not sufficient, and that it is an insulating film, which causes charge-up.

In order to solve these problems, the present inventors have used a conductive inorganic polymer as an electron beam resist, and have completed a fine pattern forming method using them.

Means for Solving the Problems That is, the present invention is (However, R ₁ and R ₂ represent the same or different fluorine-containing alkyl groups, or alkyl groups and alkoxy groups, and n
Represents a positive integer. The use of the polyphosphazene-based conductive inorganic polymer represented by the formula (4) as an electron beam resist is intended to solve the above problems. Since this polymer substance has a conjugated double bond in its main chain, it exhibits high conductivity, so that charge-up due to electrons can be prevented. Further, by introducing fluorine into the side chain, a highly sensitive positive resist can be obtained. Further, since the main chain is composed of only P and N, it has high dry etching resistance and can be used as an upper layer resist of a two-layer resist.

Further, even if it does not act as a resist, a multilayer resist can be easily formed by using this conductive inorganic polymer as an intermediate layer of a three-layer resist, and the field batting coller due to charge-up can be formed. Therefore, it is possible to form an accurate fine resist pattern without misalignment.

Action The present invention can easily form an accurate fine pattern without charge-up by the above-mentioned conductive inorganic polymer resist and the resist process using the same. It is not necessary to deposit an aluminum layer, there is no problem of contamination, the process can be simplified, and charge-up by electrons can be prevented, and an accurate fine pattern can be formed. Therefore, by using the present invention, it works effectively for accurate and high-resolution fine pattern formation.

Example 1 After dissolving the polyphosphazene shown above in chlorobenzene, the insoluble matter was filtered off to obtain a resist solution.
This resist solution was dropped onto a semiconductor substrate, spin-coated at 2000 rpm, and baked at 200 ° C. for 30 minutes.
A resist film having a thickness of 1.2 μm was formed. This resist film was exposed to an electron beam at an acceleration voltage of 20 KV and an irradiation dose of 1 × 10 ^-5 C / cm ² , and then developed with a mixed solution of methyl isobutyl ketone (MIBK) and isopropyl alcohol (IPA).
We were able to obtain an accurate resist pattern with no field or batting error due to charge-up.

(Embodiment 2) A second embodiment of the present invention is shown in FIG. Semiconductor substrate 1
A polymer organic film 2 was applied as an underlayer film on the top and baked at 220 ° C. for 30 minutes. The polyphosphazene inorganic film 3 obtained in Example 1 was applied thereon and baked at 200 ° C. for 20 minutes to obtain an inorganic film having a thickness of 0.5 μm (FIG. 1 (a)). Next, acceleration voltage 20KV, irradiation dose 1 × 10 ^-5 C /
Electron beam exposure was performed at cm ² , and development was performed with a mixed solution of MIBK and IPA, and an accurate fine resist pattern was obtained (Fig. 1 (b)). No field batting error due to charge up was seen. By using this resist pattern as a mask, the lower polymer organic film was etched, and an accurate and vertical fine resist pattern could be formed (FIG. 1 (c)).

(Embodiment 3) A third embodiment of the present invention is shown in FIG. Semiconductor substrate 1
The polymer organic film 11 was applied as the lower layer on the top and baked at 200 ° C. for 30 minutes. A polyphosphazene inorganic film 12 shown below was applied onto this and baked at 200 ° C. for 20 minutes.

Further, PMMA was applied as an electron beam resist 13 thereon, and baked at 170 ° C. for 20 minutes (FIG. 2 (a)). This resist film has an accelerating voltage of 20 KV and a dose of 1 ×
After electron beam exposure at 10 ^-4 C / cm ² and development with a mixture of MIBK and IPA, an accurate fine resist pattern without field batting error due to charge-up could be formed. (FIG. 2 (b)). The inorganic film 12 was dry-etched by using this resist pattern as a mask (FIG. 2C), and then the polymer presence / absence film 11 was etched by using the inorganic film as a mask (FIG. 2D). In this way, an accurate and vertical fine resist pattern could be obtained.

Effects of the Invention As described above, according to the present invention, a highly sensitive and high-resolution resist pattern can be formed by using a polyphosphazene polymer, which is a conductive inorganic polymer, as an electron beam resist. . By using these resists, the influence of charge-up due to exposure electrons is eliminated, and field batting and alignment accuracy can be improved. Also. Since it has sufficiently high resistance to dry etching, it can be used as an upper layer resist of a two-layer resist.

Also, by applying as an intermediate layer of a three-layer resist, it is possible to easily prevent charge-up,
An accurate and vertical fine resist pattern can be formed, which can greatly contribute to the manufacture of ultra-high density integrated circuits.

[Brief description of drawings]

FIG. 1 is a process sectional view of an embodiment of the present invention, FIG. 2 is a process sectional view of the other embodiment, and FIG. 3 is a process sectional view of a conventional multilayer resist method. 1 ... Semiconductor substrate, 11 ... Polymer organic film, 12 ... Inorganic film, 13 ... Electron beam resist.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Noboru Nomura 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-1-44935 (JP, A) JP-A-1- 44927 (JP, A)

Claims (2)

(57) [Claims] 1. A polymer organic film is applied onto a semiconductor substrate and heat-treated, and then, the polymer organic film is applied onto the polymer organic film. (However, R ₁ and R ₂ represent the same or different fluorine-containing alkyl groups, and n represents a positive integer.) A step of applying a heat treatment after coating a polyphosphazene-based inorganic polymer film represented by A step of subjecting the semiconductor substrate having the polymer organic film and the inorganic polymer film formed thereon to electron beam exposure, and performing development to selectively expose an electron beam exposed portion of the inorganic polymer film. A fine pattern forming method comprising: a step of removing and forming a resist pattern made of the inorganic polymer film; and a step of etching the polymer organic film using the resist pattern as a mask. 2. A polymer organic film is applied onto a semiconductor substrate and heat-treated, and then the polymer organic film is applied onto the polymer organic film. (However, R ₁ and R ₂ represent the same or different alkyl groups or alkoxy groups, and n represents a positive integer. A step of applying a polyphosphazene-based inorganic polymer film represented by A step of applying a resist on the inorganic polymer film, a step of performing electron beam exposure on the semiconductor substrate on which the resist, the polymer organic film and the inorganic polymer film are formed, and development. A fine patterning process, which includes a step of selectively removing an electron beam exposed portion of the resist to form a resist pattern, and a step of etching the inorganic polymer film and the polymer organic film using the resist pattern as a mask. Pattern formation method.