JPH0272361A - Electron ray resist having two-layered structure - Google Patents

Abstract

PURPOSE:To allow the exact transfer of the patterns of an upper layer resist to a lower layer by using a mixture composed of an electron ray decomposition type polymer consisting of polybutene sulfone or polyalpha-subsutd. acrylate and a phenol or cresol novolak resin introduced with a silicon-contg. substituent as the upper layer resist. CONSTITUTION:The upper layer resist of the resist having the two-layered structure is constituted of the mixture composed of the electron ray decomposition type polymer consisting of polybutene sulfone or polyalpha-substd. acrylate and the phenol novolak resin or cresol novolak resin introduced with the silicon- contg. substituent. The pattern accuracy is improved in this way and since the etching rate in RIE of O2 is low, the exact transfer of the upper layer resist pattern to the lower layer is possible and the accuracy of integrated circuits is improved.

Description

[Detailed Description of the Invention] [Summary] Regarding the upper layer resist of a two-layer structure resist, the purpose is to provide an electron beam resist that can accurately transfer the pattern of the upper layer resist to the lower layer. A mixture of an electron beam decomposable polymer consisting of an acid ester and a phenol or cresol novolank resin into which a silicon-containing substituent group has been introduced is used as the upper resist layer to form a two-layer electron beam resist.

[Industrial application field]

The present invention relates to a two-layer electron beam resist with excellent oxygen plasma etching resistance.

Thin film formation technology and photolithography (photolithography or electron beam lithography) are often used in the formation of semiconductor integrated circuits, and as these technologies advance, semiconductor unit elements are becoming increasingly finer, and semiconductor devices such as I, SI, and VLSI are becoming increasingly finer. integrated circuits have been put into practical use.

That is, regarding wiring patterns, initially a resist is coated on a thin film made of a wiring forming material formed on a substrate to be processed, and this is selectively exposed to ultraviolet light and then developed to create a resist pattern. Wiring patterns were formed by subjecting this to wet etching or dry etching.

However, as integration has progressed and miniaturization has progressed to a minimum pattern width of less than 1 μm, electron beams have come to be used as exposure light sources instead of ultraviolet rays.

In other words, the formation of fine patterns by ultraviolet light exposure is limited to about 1 μm due to wavelength restrictions, whereas the wavelength of electron beams varies depending on the accelerating voltage\and is much shorter, about 0.1 μm, so it is difficult to form fine patterns in the submicron region. This makes it possible to form fine patterns.

Next, in the manufacturing process of semiconductor devices such as LSI and VLSI, it is necessary to make circuits multilayered, and in this case, if there is a wiring pattern in the lower layer, the surface of the insulating layer formed on top of the wiring pattern is 1 to 2 μm thick. In such cases, applying the conventional single-layer resist method makes it impossible to form fine patterns with high accuracy.

Therefore, a two-layer resist is used in which a lower resist layer is first flattened, and a thin upper resist layer with excellent oxygen dry etching resistance is formed on top of the lower resist layer and then dry etched to form a fine pattern.

[Conventional technology]

The two-layer resist is made by spin-coating a material that can be easily dry-etched by oxygen (0□) plasma, such as phenol novolac resin or cresol novolac resin, to a thickness of about 2 μm and flattening it as the lower layer resist, and then forming the upper layer resist on top of this. As a result, it is easily decomposed by electron beam irradiation and becomes soluble by developer, but the non-irradiated area is 0□ Depending on the plasma, the resistant polymer material (polymer) is reduced to about 0.2 to 0.3 μm. l'! '7 <It is formed by coating.

Here, as the upper layer resist, ■ polymethacrylic acid ester having silicon (Si) as a +1N element, ■ polymer made by copolymerizing olefin and sulfur dioxide (SO, ) having Si as a constituent element, etc. Proposed.

However, the oxygen plasma etching resistance of these upper layer resists is only about 10 times that of the lower layer resist, and in the process of performing oxygen plasma etching to transfer the upper layer resist pattern to the lower layer resist, the upper layer resist is also etched to a considerable extent and the pattern is The problem is that the accuracy decreases.

[Problem to be solved by the invention]

As mentioned above, conventional two-layer structure resists cannot be said to have sufficient oxygen plasma etching resistance, and in the process of performing oxygen plasma etching to transfer the upper layer resist pattern to the lower layer resist, the upper layer resist is also etched considerably.
The problem is that pattern accuracy is thereby reduced.

[Means to solve the problem]

The above problem is solved when the upper layer of the two-layer resist is made of a mixture of an electron beam decomposable polymer such as polybutene sulfone or poly-α-substituted acrylic ester, and a phenol novolac resin or cresol novolac resin into which a silicon-containing substituent has been introduced. This problem can be solved by using a two-layer electron beam resist.

[Effect]

As already mentioned, the necessary conditions for the upper layer resist of the two-layer structure are: ■ Easily decomposed by electron beam irradiation; ■ Durability 02
It has excellent dry etching properties.

The present invention uses an electron beam decomposable polymer such as polybutene sulfone whose structural formula is shown in FIG. 1 or polyα-substituted acrylic ester whose structural formula is shown in FIG. A mixture of Talesol novolank resin or phenol novolak resin into which a Si-containing substituent shown by the formula is introduced is used.

The inventors discovered that polybutensulfone (Polybutensulfone), which has a sulfonyl group (-Sow) in its main chain, is a polymer that is known to be easily decomposed by electron beam irradiation.
On abbreviation r' [ls) and polyα-substituted acrylic ester were selected.

When such polymers are used as photosensitizers, C-8 bonds in polybutene sulfone decompose due to electron beam irradiation, and C-C bonds in the main chain of poly-α-substituted acrylic esters are decomposed by electron beam irradiation. decomposes, the polymer has a lower molecular weight and becomes easier to dissolve in a developer.

On the other hand, the non-exposed area needs to have excellent dry etching resistance, and until now, applications that require oxygen (0□) plasma etching resistance have been made using silicon dioxide (SiO□) films and spin-on glass (abbreviated as 5OG). is used.

Therefore, the present invention uses a cresol novolak resin or phenol novolac resin into which a Si-containing substituent has been introduced as a binder resin.

In this case, when the photosensitive agent and binder resin are decomposed by oxygen plasma, Si atoms combine with oxygen (0) atoms to form Sings and cover the surface, thereby improving dry etching resistance.

〔Example〕

Example 1-1: m (meta) and p (para) cresol and formaldehyde were modified into silicone to obtain a cresol novolak resin having a structural formula as shown in FIG. 4 and having a Si content of 14% by weight.

0.2 g of this resin and 0.8 g of polybutene sulfone obtained by radical polymerization and having a molecular weight of about 200,000 were mixed to prepare a 5% by weight electron beam resist solution using methylcellosolve acetate as a solvent.

First, we applied 0FP, a commercially available positive resist, on a Si substrate.
I? -80 (similar to Tokyo Ohka) was spin-coded and 200°
C for 1 hour to form a lower resist layer with a thickness of 2 μl.

Next, the above electron beam resist solution was spin-coded on top of this and dried at 80° C. to form an upper resist layer having a thickness of about 2,000.

Next, after exposure to an electron beam with an accelerating voltage of 20 kV, development was performed for 25 seconds with methyl isobutyl ketone (abbreviated as BK), resulting in a sensitivity curve as shown for third-country people, at which time 0.8
I resolved the lines and spaces of μ-gu.

Next, 0□ reactive ion etching (abbreviated as R
IE) In order to investigate the
Plasma etching was performed for 0 minutes, but no film loss was observed.

Example 1-2 = In the previous example, cresol and formaldehyde were modified into silicone, and the content of Si-containing substituents was 14
% by weight of cresol novolac resin and mixed it with polybutene sulfone to prepare an electron beam resist solution.This time, we used one with a Si-containing substituent content of 8% by weight, and the rest was the same as in the example. A two-layer resist was prepared in the same manner as in 1-1.

However, under the same conditions as before, O! If RIE is performed, approximately 20
Although a film reduction of 0.00 was observed, the sensitivity and resolution were the same as in Example 1-1.

Example 2-1: 0.96 g of a silicone-modified novolac resin into which a Si-containing substituent, the structural formula of which is shown in FIG.

(manufactured by Nippon Zeon) and mixed with 2.4 g to prepare a 5% by weight electron beam resist using MCA as a solvent.

Next, the leaf PR-80 was placed on the Si substrate in the same manner as in Example 1-1.
0 (manufactured by Tokyo Ohka) to form a 2 μm lower resist layer, and after spin-coding the electron beam resist solution above, drying at 80°C to a thickness of approximately 2000°C.
Formed the upper resist layer of the person.

Next, as before, it was exposed to an electron beam with an accelerating voltage of 20 kV, and then developed for 1 minute in a 1:1 solution of methyl isobutyl ketone (abbreviated as BK) and ethyl acetate. As a result, a sensitivity curve as shown in Figure 3 was obtained. can be obtained, and the sensitivity at this time is 3
0 μC/cm” and 0.8 μm line and
I was able to resolve space.

Next, in order to examine o
Plasma etching was performed for 10 minutes under 0W conditions, but no film loss was observed.

〔Effect of the invention〕

According to the present invention, since an electron beam decomposition type volima is used as a photosensitizer, pattern accuracy is good, and 0° to 1? Since the etching rate in IE is low, the upper layer resist pattern can be accurately transferred to the lower layer, thereby making it possible to improve the precision of the integrated circuit.

[Brief explanation of the drawing]

Figure 1 is the structural formula of polybutene sulfone, Figure 2 is the structural formula of poly-α-substituted acrylic ester, Figure 3 is the sensitivity curve of the electron beam decomposable polymer according to the present invention, and Figure 4 is the silicon-containing substituent. Figure 5 is the structural formula of Talesol novolak resin into which a silicon-containing substituent has been introduced. J-13 Nonu Riften Dilf Person G')
-'Kaya 2. 11 photos of the horned cow Yagamarimag 1st year of the year 3

Claims (1)

[Claims] A two-layer structure characterized in that a mixture of an electron beam decomposable polymer made of polybutene sulfone or poly-α-substituted acrylic ester and a phenol or cresol novolac resin into which a silicon-containing substituent has been introduced is used as an upper resist layer. Electron beam resist.