JPH021860A - Radiation sensitive positive type resist high in resolution - Google Patents

Abstract

PURPOSE:To enhance sensitivity and resolution of a resist by using a monodispersed homopolymer or copolymer of a specified monomer. CONSTITUTION:The positive type resist is formed by using the monodispersed homopolymer of the monomer or the monodispersed copolymer of said monomer represented by the formula on the right in which X is alkyl or halogen and Y is alkyl or haloalkyl. As the monomer, trifluoroethyl methacrylate and the like can be used, and the monomer can be polymerized by the low temperature anion polymerization method using an anion polymerization initiator, and the obtained polymer or copolymer is dissolved in methylcellosolve acetate or the like and applied to the surface of a desired layer.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention provides a high-resolution radiation-sensitive resist based on a monodisperse homopolymer of monomers or a monodisperse copolymer composed of two or more different monomer groups. It is related to.

<Technical Background of the Invention> As lithography techniques at the level of 0.5 μm or less, which is the limit of optical exposure for semiconductor integrated circuits, electron beam direct writing, X-ray lithography, and exposure techniques using focused ion beams have been proposed. Although this technology is already reaching the stage of realization, the development of resists that can handle this has been slow. When these resist materials are irradiated with radiation, a cross-linking reaction occurs, making them insoluble in the developing solution.When irradiated with radiation, the main polymer of the resist causes a chain splitting reaction, resulting in a lower molecular weight. There is a positive type in which the resist is easily dissolved in the developer and the resist in the irradiated area is removed.

Negative resists are characterized by high sensitivity but low resolution.

In contrast, positive resists have high resolution, but
The sensitivity is poor.

Recently, the industrial world's demand for higher integration of semiconductor integrated circuits has become more and more demanding, and negative resists, which have high sensitivity and excellent productivity, have been forced into decline due to their low resolution. As a result, positive resists have become mainstream.

<Problems with the prior art> Polymethyl methacrylate (P-MMA) is a typical main polymer for positive resists, and its resolution is 0.
．． Although it is said to have a diameter of 3 to 0.5 μm, its sensitivity to electron beams is extremely low at 5 Xl0-'C/cJ, which is inferior to negative type resists and far from being a practical resist.

Positive resists are being intensively studied because most of the resists that have been developed so far have inferior sensitivity and lack of balance in terms of performance compared to their resolution.

Many of the proposals for improving these sensitivities are based on C
1, Br, F, I, S, O, N, etc. - Examples include polyhexafluorobutyl methacrylate, polytrichloroethyl methacrylate, polybutene-■ sulfone, and polysulfone. Examples include trifluoroethyl α-chloroacrylate, novolac-poly2-methyl l-pentenesulfone mixture, and the like.

Styrene, P-
It has been reported that monodisperse polymers are synthesized from dimethylaminomethylstyrene, isoprene, etc. using anionic polymerization initiators such as butyllithium, and the resolution is significantly improved.

<Purpose of the Invention> The present invention employs the monodispersed homopolymer or copolymer of the general formula (1) as the main resist polymer, thereby achieving a D-RAM of 16 megabits or more. The purpose is to provide resist materials for large-scale integrated circuits.

It goes without saying that the essential conditions for a resist material for such a large-scale integrated circuit are a material having high resolution and high sensitivity.

<Structure of the invention> The present invention has electron-withdrawing groups 0, C1, FBr,
It possesses extremely high sensitivity characteristics to radiation,
This is a radiation-sensitive resist incorporating a monodisperse polymer that is expected to significantly improve resolution.

The present invention is comprised of the homopolymer or copolymer of the above general formula (1). Positive resists based on these polymers have a practical sensitivity of 2 to 5 μC/ci, and P-H
Productivity is 10 to 25 times better than MA and line width is 0.3
Practical resolution below μm, i.e. 16 megabit D-RA
The present invention was completed based on the prospect of a significant improvement in processing accuracy that would be fully applicable to large-scale integrated circuits after M.

The monomer used in the present invention is represented by the following formula.

/X // CH, =C \7 However, in the formula, X is an argyl group or a halogen, and Y is an alkyl group or a halogenated alkyl group, specifically trifluoroethyl methacrylate, hexafluoropropyl methacrylate, hexafluoro These include butyl methacrylate, trifluoroethyl α-chloroacrylate, tetrafluoropropyl methacrylate, perfluorooctylethyl methacrylate, and tetrafluoropropyl α-chloroacrylate.

These monomers may be obtained by conventional synthesis methods and purified by dehydration using calcium hydride or the like. Further, as a method for obtaining a monodisperse polymer by polymerizing these monomers, a low-temperature anionic polymerization method using an anionic polymerization initiator can be mentioned. That is, by controlling the reaction at low temperatures (for example, -20°C to 100'c), polymerization proceeds slowly and a polymer with uniform molecular weight (dispersity i:i1) can be obtained.

Both the above monodisperse homopolymer and monodisperse copolymer usually have a molecular weight of 20,000 to 2,000,000, but preferably 200,000 to 10,000.
00,000 are used.

<Effects of the Invention> The high-resolution radiation-sensitive resist according to the present invention is superior to the conventional P-
Compared to MMA resist, it has extremely high sensitivity characteristics, requiring only about 1/10 to 1/25 of the radiation dose, and by using a monodisperse polymer, the line width is 0.3 μm.
It is an excellent resist that exhibits the following extremely high resolutions, and is suitable for ultra-high-density engraving, such as in the electron beam and j! It guarantees a significant improvement in processing accuracy and wide latitude circuit design, and its excellent sensitivity to radiation has a significant effect on improving throughput and reducing costs in X-ray lithography.

Although examples of the present invention are shown above, it goes without saying that the present invention is not limited to these examples.

Example 1 50 ml of a solution of TIIF' (9) completely dehydrated by a conventional method containing anionic polymerization initiator 1 and l-diphenyl3-methylpentyllithium was introduced into a flask, and the inside of the flask was evaporated in a dry N2 stream. The system was cooled to 75°C. While thoroughly stirring the system, trifluoroethyl methacrylate (TFEM), which had been thoroughly dehydrated by a conventional method, was
A) 50.4 g (0.3 mol) / 100
ml of completely dehydrated Tl1F solution was quickly added under a dry N2 stream while maintaining the system internal temperature at -75°C, and reacted with stirring for about 5 hours. Methanol was added to deactivate the active sites of the polymer, and this was added to the system. After taking it out and purifying it by reprecipitation method, its molecular weight was determined by gel permeation chromatography (GPC), light tlJi, and randomization method, and the molecular weight was 385,000, and the degree of dispersion was It was 1.09.

A 6.5% by weight solution of this polymer in methyl cellosolve acetate (MCA) was prepared and coated onto a thermally oxidized silicon layer with a thickness of 0.5 μm using a spin coating method to form a 0.51 μm film I.
A polymer film of I was obtained.

After heating this at 200°C for 115 minutes, the acceleration voltage was set to 10, ν, 2.5 x 10-hC/
crA (7) Apply the electron beam to the resist film surface according to a predetermined pattern! It was 1.l.

Next, this was taken out into the atmosphere and mixed with 25 °C of ethyl cellosolve and isopropyl alcohol (IPA).
The film was developed by immersing it in a 7:3 developer solution for 5 minutes, and was rinsed and dried in a vacuum. Next, the resist film was subjected to a 115-minute boil-hake at 80°C, and when the resist film was observed with a scanning electron microscope (SEM), the resist in the electron beam irradiated area was completely removed, and the adhesion between the thermally oxidized silicon layer and the resist film was also good. It was confirmed that

When this was etched for 7 nights (cerium ammonium nitrate/perchloric acid), a sharp linear pattern of 0.3 μm was observed by SEM.

Comparative Example 1 When a TFHMA homopolymer having a dispersity of 3.8 and a molecular weight of 355,000 was used as a resist main ingredient, the resolution under the same conditions as in Example 1 was 0.8 μm.

Example 2 Trifluoroethyl α- obtained in the same manner as Example 1
The degree of dispersion of the anionically polymerized homopolymer of chloracrylate (TFECA) was 1.12, and the molecular weight was 348,000.

6.1 heavy oil% of this polymer? An ICA solution was prepared and applied onto a 0.5 μm thick thermally oxidized silicon layer by a spin coating method to obtain a 0.53 μm thick polymer film. This 2
After heat treatment (brihake) at 00° C. for 130 minutes, the resist surface was irradiated with an electron beam of 2 Xl0-'C/cffl at an acceleration voltage of 10 KV according to a predetermined pattern. Next, this was taken out into the atmosphere and methyl isobutyl keto 7
(MIBK) and IPA in an 8:2 developer solution at 25°C.
After dipping for 15 minutes and developing, rinsing with IPA and drying, post-baking at 110°C for 130 minutes, and observing this resist +19 with SEi, it was found that the resist in the electron beam irradiation H region was completely removed. It was confirmed that there is.

When this was etched according to Example 1, 0.3
A sharp pattern of μm was obtained.

Comparative Example 2 When a TFECA homopolymer having a dispersity of 3.3 and a molecular weight of 375,000 was used as a resist main ingredient, the resolution under the same conditions as in Example 2 was 0.5 μm.

Example 3 A monodisperse anionic polymer of trifluoroethyl methacrylate was obtained in the same manner as in Example 1, and 1/2 (molar ratio) of 2.2.33-fluoropropyl methacrylate (TP P A copolymer obtained by adding M A ) (TFEM^/TFP?IA・2/
The dispersity of l (molar ratio) is 1.14, the molecular weight is 42.5
It was 10,000.

6゜3% by weight MCA of this copolymer? 8 liquids were prepared and applied by spin coating onto a thermally oxidized silicon layer with a thickness of 0.5 μm to form a copolymer film with a thickness of 0.52 μm:
)is. After pre-baking this at 180'C for 115 minutes, the acceleration torque IQKV, 3. OX 10-'C/cffl
(7) Apply the electron beam to the resist film surface according to a predetermined pattern! I, 1 irradiation, development, rinsing, and post-hake under the same conditions as in Example 1. The results of SEH observation of this resist film were almost the same as in Example 1, and the resist film was carried out in accordance with Example 1. As a result of etching, a sharp linear pattern of 0.3 μm was observed in 5Etl.

Comparative Example 3 Molecular iJi degree 4. l, molecule! When a 1t454,000 copolymer (TFE/TFPMA=2/1 (molar ratio)) was used as the resist main ingredient, the resolution under the same conditions as in Example 3 was 0.8 μm.

This result shows that Examples 1 to 3 have an effect of improving resolution by employing monodispersed polymers.

Procedural author's letter (spontaneous) December 2, 1988 1, Indication of the case Patent application No. 145207/1983 2, Name of the invention Person who corrects high-resolution radiation-sensitive positive resist 36 Relationship to the case Patent Applicant address: 1-5-1-4 Taito, Taito-ku, Tokyo, amended "r50m" on page 7, line 14 of the amended specification in the detailed description of the invention of the specification to be amended to '500mJ.

Claims (1)

[Claims] (1) General formula▲There are mathematical formulas, chemical formulas, tables, etc.▼……(I) (However, in the formula, X is an alkyl group or halogen, Y is an alkyl group or a halogenated alkyl group) A high-resolution radiation-sensitive positive resist characterized by using a dispersed homopolymer or a monodispersed copolymer obtained by polymerizing two or more monomers selected from this group.