JPH04294355A - Resin composition and method for formation of resist pattern - Google Patents

Abstract

PURPOSE:To improve resolution by applying a polymer resist containing a specified polyacrylate org. compd. as the basic skeleton on a lower resist layer, and then exposing and developing. CONSTITUTION:The resist compsn. consists of a polymer having a polyacrylate org. compd. expressed by formula I as the basic skeleton. In formula I, R is alkyl group or hydrogen, R1-R5 are alkyl groups and may be same or different, (l) and (m) are positive integers from 1 to 4, (n) is positive number. Then the resist of this resist compsn. is applied on the lower resist layer, then exposed to light and developed. By using the resist comprising the polymer having polyacrylate as the basic skeleton and Si introduced to the polymer ester, a negative-type submicron pattern excellent in O2 plasma durability, sensitivity and resolution can be formed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-layer negative resist and a pattern forming method thereof. Due to the need to process large amounts of information at high speed, the integration of semiconductor devices that form the main body of information processing equipment has progressed, and LSI and VLSI have been put into practical use.

[0002] Integration has been achieved by miniaturizing unit elements, and the minimum line width of wiring patterns has reached submicron. On the other hand, since multilayer wiring is used, there are many fine steps on semiconductor wafers forming integrated circuits.

Now, in the production of semiconductor integrated circuits, a resist is coated on a semiconductor substrate, selective exposure is performed, the exposed or non-exposed areas are dissolved by development processing to open a window in the resist, and then dry etching is performed. Photolithography (photolithography or electron beam lithography) is essential for patterning conductive and insulating films.

[0004] Therefore, a multilayer resist method having a two-layer or three-layer structure is used as a method to eliminate the influence of steps and form fine patterns with high precision.Among these, the two-layer resist method, which requires fewer steps, is the most common. It is used in

[0005]

[Prior art] The two-layer resist method involves coating a substrate with steps with a novolac resin as a lower resist layer and flattening the layer. This is a method of forming a thin upper layer resist with excellent properties.

Although various resists have been proposed as such upper layer resists, an electron beam resist that fully satisfies sensitivity and resolution has not yet been put into practical use. That is, a polymer with a siloxane skeleton is used as a negative resist characterized by excellent O2 plasma resistance,
A ladder type or three-dimensional crosslinked type has been proposed.

SNR-EX (manufactured by Tosoh), whose structural formula is shown in formula (2), is a typical resist.

[0008]

[Case 2]

However, although this resist has excellent O2 plasma resistance, when it is developed using an organic solvent, the solvent is incorporated into the resist, causing swelling, making stable pattern formation impossible, and insufficient There is a problem that it does not have a high resolution.

0010

Problems to be Solved by the Invention It is necessary for the upper layer resist used in the two-layer resist method to have excellent O2 plasma resistance, as well as excellent sensitivity and resolution.

However, conventionally proposed polymers with a siloxane skeleton made into a ladder type or a three-dimensionally crosslinked type have excellent O2 plasma resistance, but do not have sufficient resolution because they swell during development processing. The problem is that it does not show.

0012

[Means for solving the problem] The above problem is solved by the structural formula (1
) using a polymer resist whose basic skeleton is a polyacrylate organic compound with excellent resolution.
This problem can be solved by configuring a resist pattern forming method characterized by coating this resist on a lower layer resist, performing exposure and development.

[0013]

[Function] Conventionally, the upper layer resist used in the two-layer resist method was based on a polymer with a siloxane skeleton, making it impossible to create an electron beam resist with excellent resolution. An attempt was made to form a negative resist by introducing Si into a polymer ester having an excellent acrylate skeleton.

However, the polymethacrylate whose structural formula is shown in FIG. 3, in which the ester is a trimethylsilylmethyl group, exhibited positive type behavior when irradiated with an electron beam and did not become negative type.

[0015]

[Chemical formula 3]

[0016] Therefore, as a result of synthesizing and investigating a polymer whose basic skeleton is a polyacrylate organic compound whose structural formula is shown in Figure 1, it was possible to obtain a resist that exhibited negative type behavior and had good resolution. Ta.

Although this resist has a slightly lower Si content than the conventional resist whose structural formula is shown in FIG. 2, it has been found through experiments that it has practically sufficient O2 plasma resistance.

[0018]

[Example] Synthesis Example 1: (Synthesis example of homopolymer) α,α'-Azobisisobutyronitrile (abbreviation: AIBN) was added thereto, and the reaction was maintained at 80°C for 11.5 hours.

[0019]

[C4]

Thereafter, this reaction product was dropped into a large amount of methanol solution, and the precipitated polymer was filtered and recovered to obtain a homopolymer having the structural formula shown in FIG. 5 in a yield of 78.
Obtained in %.

[0021] The average molecular weight of this polymer was 7.7 x 104 in terms of weight average molecular weight, and the degree of dispersion was 2.28.

[0022]

[C5]

Example 1: (Homopolymer) A phenol novolak resin was applied to a thickness of 2 μm on a Si wafer using a spin coating method to form a lower resist layer, and on top of this, toluene of the homopolymer obtained in Synthesis Example 1 was applied. The solution was applied to a thickness of 3000 Å by spin coating and heated at 150°C.
It was heated and dried for 30 minutes.

Next, this wafer was exposed to an electron beam with an accelerating voltage of 20 KeV and developed using ethylbenzene, resulting in a well-shaped negative pattern with a width of 0.6 μm at an exposure dose of 8.0 μC/cm2. was able to form.

Next, dry etching was performed by reactive ion etching (abbreviated as RIE) using O2 gas, but the etching rate was about 1/50 of that of phenol novolak resin, and a 0.6 μm wide pattern was formed on the lower resist. was able to transcribe it. Example 2: (Alkali-developable copolymer) The following copolymer was synthesized and used as a resist.

These copolymers can be used with TMA as a developer.
Since H can be used, swelling can be prevented.

[0027]

[C6]

Here, R6 is a C00H group or C6H4
OH group Then, as in Example 1, a phenol novolac resin was applied to a thickness of 2 μm on the Si wafer to form a lower resist layer, and a toluene solution of the above copolymer was applied onto this to a thickness of 3000 Å by spin coating. Apply,
It was dried by heating at 150° C. for 30 minutes.

Next, this wafer was exposed to an electron beam at an accelerating voltage of 20 KeV and developed using TMAH. As in Example 1, the wafer was exposed to an exposure dose of 8.0 μC/cm2 and had a good shape of 0.6 μm. It was possible to form a wide negative pattern.

In particular, since the copolymer represented by formula (6) can be developed with an alkaline aqueous solution, no swelling is observed. Example 3: (Copolymer developed with other than alkaline aqueous solution)

[0031]

[C7]

Here, the combination of R and R7 is as follows. ■ H and H ■ CH3 and H ■ H and CH2Cl■
CH3 and CH2Cl■ H and
Cl ■ CH3 and Cl Next, using the copolymers shown by formulas (6) and (7), dry etching was performed by RIE using O2 gas, but in both cases, the etching rate was about the same as that of the phenol novolak resin. It was 1/30, and a pattern with a width of 0.6 μm could be transferred to the lower resist layer. Example 4: (Homopolymer) The homopolymer obtained in Synthesis Example 1 was added with 4,4′, which is a photosensitizer.
- 10% diadochalcone was mixed to make it photosensitive to wavelengths in the ultraviolet region.

[0033] As a light source, xenon/mercury (Xe
-Hg) A pattern was formed in the same manner as in Example 1 except that exposure was performed for 30 seconds using a lamp.
．． It was possible to resolve 8 μm.

[0034]

[Effect of the invention] By using this resist in which Si is introduced into a polymer ester with a basic skeleton of polyacrylate, a negative submicron pattern with excellent O2 plasma resistance and excellent sensitivity and resolution can be formed. be able to.

Claims (2)

[Claims] 1. A resist composition comprising a polymer having a basic skeleton of a polyacrylate organic compound represented by the following structural formula. [Formula 1] However, R is an alkyl group or hydrogen R1 to R5 are alkyl groups, and l and m, which may be the same or different, are positive numbers from 1 to 4. n is a positive number. 2. A method for forming a resist pattern, which comprises applying a resist made of the above-mentioned resist composition onto a lower resist layer, and performing exposure and development.