JP2516968B2 - Flattening material for two-layer electron beam resist - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] In an electron beam resist having a two-layer structure, in order to eliminate charge accumulation that occurs during exposure, the lower layer resist is a high molecular weight polycation or low molecular weight cation tetracyanoquinodimethane. A resist material comprising a mixture of a salt-type complex and a photocurable resin composition, which retains conductivity.

[Industrial applications]

The present invention relates to a two-layer structure electron beam resist, and more particularly to improvement of workability and improvement of a lower layer resist which eliminates electron accumulation.

With the progress of information processing technology for processing a large amount of information at high speed, semiconductor devices have been increased in capacity and LSIs and VLSIs have been put into practical use, but these are all realized by miniaturization of unit elements. .

That is, the electrode area forming each unit element and the wiring pattern width for interconnecting the elements are extremely miniaturized, and the minimum pattern width is about 1 μm.

Now, fine electronic circuits such as surface integrated filters such as semiconductor integrated circuits such as ICs and LSIs are almost always formed by using thin film forming technology and photolithography technology (photolithography).

The semiconductor integrated circuit, which has been miniaturized most, is described below. A photosensitive resist (photoresist) is spin-coated on a semiconductor substrate (wafer) to form a thin film, and a required position is opened by selective exposure. Then, a semiconductor region is formed by an ion implantation method or the like, the photoresist is removed, and then an insulating layer is formed over the entire surface of the wafer by a chemical vapor deposition method or the like.

Next, a photo-resisting technique consisting of photoresist coating, selective exposure and dry etching is applied to this insulating layer to open a window for an electrode position, and a thin film forming technique such as a vacuum deposition method or a sputtering method is used on this wafer. A thin film of conductive metal is formed by using the photolithography technique as described above, and a fine wiring pattern in the X direction, for example, is formed for each unit element.

Next, after forming an insulating layer on this using the thin film forming technique as before, a contact hole is opened, a conductive metal is vapor-deposited on this to form a thin film, and then a photo-etching technique is used. A fine wiring pattern in the Y direction, for example, is formed for each unit element.

As described above, a fine pattern is formed by the thin film forming technique and the photo-etching technique, but the minimum pattern width is 1 μm.
Since miniaturization has progressed to less than this, electron beams have come to be used as an exposure light source instead of ultraviolet rays.

That is, the formation of a fine pattern by UV exposure is limited to 1 μm or more due to the wavelength limitation, whereas the wavelength of the electron beam varies depending on the accelerating voltage. Can be formed.

Next, in order to form the wiring pattern of the integrated circuit, for example, a three-dimensional intersection of the X-direction wiring pattern and the Y-direction wiring pattern is required, but a significant step is generated at the intersection portion, and therefore, similar to a flat surface. When the photo-etching technique is applied by the method, there is a problem that the wiring pattern width is narrow and thus the disconnection is likely to occur.

Therefore, as a solution to this problem, a photolithography technique of using a two-layer structure resist, flattening the wafer surface with a lower layer resist, coating an electron beam resist on this, irradiating an electron beam, and selectively exposing Being developed.

The present invention relates to an improvement in this lower layer resist for planarization.

[Conventional technology]

The requirement for the lower layer resist for a two-layer electron beam resist is that there is no charge accumulation.

It can be formed by a short-time treatment.

Excellent dry etching resistance against fluorine gas plasma and chlorine gas plasma.

And the like.

That is, as a problem related to the above, in the electron beam exposure, the upper layer resist is exposed by the electron beam irradiated, and a considerable amount of the electron beam penetrates the upper layer resist and reaches the lower layer resist.

Here, since the electrons are negatively charged, the accumulation of charges in the lower layer resist (charge-up) hinders the projection of the electron beam, resulting in the displacement of the exposed pattern. There is.

As a solution to this, a method of making the lower layer resist conductive so as to prevent the accumulation of electric charge is good, and the inventors previously added polyvinylbenzyltrimethylammonium / TCNQ salt type complex to the cresol novolac resin to improve the conductivity of the resist. It is proposed to set 10 ^-15 to 10 ^-12 Scm ^-1 . (Japanese Patent Application No. 60-254003) However, this salt type complex is difficult to synthesize,
There is also a problem that the compatibility with the resin is not good.

In addition, as for the conventional, a positive resist composed of a cresol novolac resin and a naphthoquinone azide compound has been used, but it is necessary to use a positive resist for use as a planarizing layer.
The baking process is required at 0 ° C. for about 1 hour, which is a problem.

[Problems to be solved by the invention]

As described above, it is necessary to use an electron beam resist having a two-layer structure in order to form a conductor pattern having a minute line width on a substrate having a step.

However, when using the electron beam resist, there is a phenomenon of accumulation (charge-up) of irradiation electrons, and it is necessary to eliminate the positional deviation of the pattern due to this phenomenon.

On the other hand, the inventors have proposed a method of making the lower layer resist conductive, but it is not sufficient in terms of workability and characteristics.

 Therefore, the problem is to solve this.

[Means for solving problems]

The above problem is that after applying a lower layer resist on the substrate to be processed including a high step and flattening it, an upper layer is coated with an electron beam resist and exposed, and a resist pattern is formed using a photo-etching technique. The lower layer resist used for the solution is solved by using a planarizing material for a two-layer structure electron beam resist, which is composed of a mixture of a tetracyanoquinodimethane salt type complex of a high molecular weight polycation or a low molecular weight cation and a photocurable resin composition. can do.

[Action]

The present invention has been made as a product on the conventional research line, and is a salt-type complex of tetracyanoquinodimethane (abbreviated as TCNQ) of a high molecular weight polycation which is commercially available or easy to synthesize or a salt-type of a low molecular weight cation. The use of a complex provides conductivity, and the use of an ultraviolet curable resin as the resin shortens the curing time.

The lower-layer resist formed in this manner has a conventional lower-layer resist conductivity of 10 ⁻¹⁷ to 10 ⁻¹⁶ Scm ^−1.
It can be increased to ^-15 to 10 ^-12 Scm ^-1 , which can solve the problem that a pattern shift occurs due to charge accumulation in electron beam exposure.

〔Example〕

Example 1: [Polymer polycation TCNQ salt type complex (Simple-s
Example of use of alt)] A polymer PiX-TCNQ salt-type complex having a structural formula shown in Fig. 1 was dissolved in dimethylformamide (abbreviation: DMF) to prepare a 0.4 wt% solution.

A lower layer resist solution was prepared by adding benzophenone (Wako Pure Chemical Industries, Ltd.) as a photopolymerization initiator to an ultraviolet curable epoxy acrylate resin (Product name: Lipoxy SP-4010 Showa Highpolymer Co., Ltd.).

This was applied onto a silicon (Si) wafer by spin coating to form a flattening layer having a thickness of 2 μm.

After being cured by being irradiated with ultraviolet rays, a silicone resist was applied to the upper layer to a thickness of 0.2 μm and prebaked at 80 ° C. for 20 minutes to cure.

Next, electron beam exposure is performed under the conditions of an accelerating voltage of 20 KV and an exposure amount of 16 μC / cm ² , and after developing for 30 seconds using methyl isobutyl ketone (abbreviation MIBK), isopropyl alcohol (abbreviation IP
Rinse with A) for 10 seconds.

Using the pattern thus formed as a mask, oxygen (O ₂ ) plasma etching is performed to transfer the pattern,
A line and space of 0.5 μm was resolved.

Next, when the amount of positional deviation of this pattern was examined, no positional deviation due to charge accumulation was observed.

Example 2: [TNCQ salt-type complex of low molecular weight cation (Simple-s
alt)] 1,4-dimethylpiperazine and dichloromethane were reacted to obtain a low molecular weight cation-TCNQ whose structural formula is shown in Fig. 2.
The salt complex was dissolved in DMF to give a 1% by weight solution.

The ene / thiol photocurable resin composition [Adekaoptomer BY-300 (Asahi Denka Kogyo Co., Ltd.)] was added to the epichlorohydrin (3: 1) solution, and this was spin-coated on a Si wafer to 2 μm. A thick flattening layer was formed and was irradiated with ultraviolet rays to be cured.

Thereafter, an upper layer resist is formed in the same manner as in Example 1,
When a pattern is formed, 0.5 μm line and
The space was resolved, and when the amount of pattern displacement was examined, no displacement due to charge accumulation was observed.

Example 3: [TCNQ salt-type complex of low molecular weight cation (Complex-
salt)] The TCNQ of n-butyl acridium whose structural formula is shown in Fig. 3
The salt complex was dissolved in DMF to give a 0.5 wt% solution.

This is added to a solution obtained by adding benzophenone to Lipoxy SP-4010 and diluting it in the same manner as in Example 1 to form a lower layer resist solution, and after forming a planarizing layer having a thickness of 2 μm, it is irradiated with ultraviolet rays and cured. It was

Thereafter, an upper layer resist is formed in the same manner as in Example 1,
When a pattern is formed, 0.5 μm line and
The space was resolved, and when the amount of pattern displacement was examined, no displacement due to charge accumulation was observed.

〔The invention's effect〕

As described above, when a mixture of a TCNQ salt type complex of a high molecular weight polycation or a low molecular weight cation and a photocurable resin composition is used as a lower layer resist, workability is good and there is no charge accumulation during electron beam irradiation. Therefore, it is possible to form a highly precise fine pattern.

[Brief description of drawings]

FIG. 1 is a structural formula of a high molecular weight polycation Pix-TCNQ salt type complex, FIG. 2 is a structural formula of a low molecular weight cation-TCNQ salt type complex, and FIG. 3 is a structure of an n-butyl acridium-TCNQ salt type complex. The formula is.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shoji Shiba, 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Fujitsu Limited (72) Inventor Keiji Watanabe, 1015, Kamedotachu, Nakahara-ku, Kawasaki, Fujitsu Ltd. (56) References JP-A-59-107347 (JP, A) JP-A-59-93441 (JP, A) JP-A-61-144639 (JP, A) JP-A-60-8839 (JP, A) Special table Sho-58-502169 (JP, A)

Claims (1)

(57) [Claims] 1. A lower layer resist is coated on a substrate to be processed having a high step to be planarized, and then an electron beam resist is coated on the upper layer for exposure, and a resist pattern is formed by using a photo-etching technique. The lower layer resist used for the above is composed of a mixture of a tetracyanoquinodimethane salt type complex of a high molecular weight polycation or a low molecular weight cation having a cation portion in the main chain and a photocurable resin composition. Planarization material for layered electron beam resist.