JPS6326653A - Photoresist material - Google Patents

Abstract

PURPOSE:To enhance sensitivity to near and far ultraviolet rays and resolution as well as dry etching resistance by using a polymer having specified sulfonate esters for a photoresist. CONSTITUTION:The photoresist material is made of the polymer having 0-nitrated benzyl sulfonate groups represented by the formula shown on the right in which each of R1 and R2 is H or lower alkyl, and it has a molecular weight of, preferably, several thousands - several millions, if lower than this range, it deteriorates in mechanical strength of the formed film and if higher than it, t he solution of the photoresist material becomes too high in viscosity, resulting in becoming hard to control the film thickness and difficult to handle, thus permitting the sulfonic acid formed by exposure to near or far ultraviolet rays to be made quite different in solubility from the nonexposed parts and to be developed by an aqueous solvents, and consequently, the obtained pattern to be enhanced in resolution.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a photoresist material, and more specifically, to a photoresist material that has high sensitivity, high resolution, and excellent dry etching resistance for near-ultraviolet and far-field radiation. Regarding resist materials.

[Background of the invention]

In recent years, semiconductor integrated circuits have become denser and more highly integrated, and we are now in an era where the degree of integration is 1 Mbit or more, and it has become necessary to form patterns of the 1 μm rule or even smaller. Along with this, along with lithography using electron beams and X-rays,
Multilayer resist, 0EL (Contrast Enhan
Attempts have been made to utilize near-ultraviolet and far-ultraviolet photolithography techniques using high-resolution resists, etc.

The performance of the resist material used in this case is that it is highly sensitive to the light source used, that the resolution of the formed pattern is excellent, and that a dry process is required for microfabrication. To be advantageous, it is necessary to have dry etching resistance. In order to satisfy high resolution, a positive type is more advantageous than a negative type, and it is particularly preferable that it can be developed in an aqueous system. A typical positive photoresist material is a resist made of a novolac resin and a naphthoquinone diazide photosensitizer. This resist material has a thickness of 1μ
The resolution is sufficient when forming a pattern of m or more, but when it comes to fine patterns, the resolution is not sufficient due to film thinning.

Further, the polymer disclosed in JP-A No. 48-47320, in which polyacrylic acid is esterified with 0-nitrobenzyl alcohol, becomes alkali-soluble when irradiated with light, but has high resolution but low sensitivity.

[Purpose of the invention]

The present invention has been made from the above viewpoint, and its purpose is to provide a material that has high sensitivity and resolution to near ultraviolet and far ultraviolet light, and has dry etching resistance, as a practical resist material for use in microfabrication. There it is.

[Structure of the invention]

The inventors of the present invention conducted extensive research in search of a resist material that has high sensitivity, high resolution, and excellent dry etching resistance. As a result, they discovered that a polymer containing a benzyl-type sulfonic acid ester in which the ester moiety is substituted with a nitro group at the 0-position has excellent performance, leading to the present invention.

That is, the present invention relates to a photoresist material characterized by comprising a polymer containing a structural unit represented by the general formula (1) % formula % (RIs R,; hydrogen or a lower alkyl group. The lower alkyl group is carbon Number 1~
5 is preferably an alkyl group, such as a methyl group or an ethyl group.

The polymer containing the structural unit represented by the above general formula (1), which is the resist material of the present invention, can be produced, for example, by the following method.

An example of a polymer reaction is a method in which a polymer consisting of a repeating unit represented by general formula (2) (RI; hydrogen or a lower alkyl group) is esterified with an alcohol in the presence of an alkali such as potassium hydroxide. .

Further, α- represented by the general formula (3) (R,,R,; hydrogen or lower alkyl group)
By monopolymerizing or copolymerizing substituted styrene sulfonic acid esters, a polymer containing a structural unit represented by the above general formula +1) can be obtained.

The polymer is obtained by ordinary radical polymerization, which can be carried out by bulk polymerization, solution polymerization, or emulsion polymerization.

α-substituted styrene sulfonic acid ester can be synthesized by the following method. For example, in the case of styrene sulfonate ester (7I), styrene sulfonate chloride is synthesized by reacting sodium styrene sulfonate with a chlorinating agent such as thionyl chloride or phosphorus pentachloride, and then the compound is
-It can be synthesized from K by reacting it with a nitrobenzyl type alcohol in the presence of a base.

α-substituted styrene sulfonic acid ester and tjm&'! contained in the resist material of the present invention. ,, Styrene sulfonic acid 2-nitrobenzyl ester, Styrene sulfonic acid 2-
Nitro 3-methylbenzyl ester.

Examples include styrenesulfonic acid 2-nitro-5-methylbenzyl ester, α-methylstyrenesulfonic acid 2-nitrobenzyl ester, and the like.

The resist material according to the present invention preferably has a molecular weight in the range of several thousand to several million. If the molecular weight is less than several thousand, the mechanical strength of the formed film may be poor. Furthermore, if the number exceeds several million, the viscosity of the resist material solution becomes too high, making it difficult to control the film thickness and making it difficult to handle.

The coating solvent for the resist material according to the present invention is not particularly limited as long as it can dissolve the polymer and form a uniform film, but xylene is an example.

Can you name toluene, benzene, tetrahydrofuran, dimethylformamide, etc.?

As the developer, an alkaline developer can be used and gives a positive pattern. Further, when development is performed using an organic solvent system such as the above-mentioned coating solvent, a negative pattern can be obtained. However, if emphasis is placed on resolution, a positive pattern using alkaline development is preferable. Coating.

Other methods such as prebaking, exposure, and development may be performed according to conventional methods.

〔Effect of the invention〕

In the resist material of the present invention, the sulfonic acid ester becomes sulfonic acid when irradiated with near ultraviolet light or far ultraviolet light, and the irradiated area has completely different solubility in a solvent compared to the unirradiated area. or,
Since it can be developed in an aqueous system with extremely little swelling, it is considered to be a trap for high resolution.

It is presumed that the high sensitivity of the resist material of the present invention is due to the fact that it contains sulfur and nitrogen atoms in its molecules.

Furthermore, since the resist material of the present invention is a polystyrene derivative, it has excellent dry etching resistance.

From the above, the resist material of the present invention is effective as a resist material for forming fine patterns in semiconductor manufacturing and the like.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Synthesis Examples and Examples, but the present invention is not limited thereto.

Synthesis example Synthesis of styrene sulfone 20-nitrobenzyl ester Styrene sulfonylflora ()''2 [10 g, o
- nitrobenzyl alcohol 15.12 and benzene 1
809 was placed in a 500-Eggplant flask, and while stirring under water cooling, 30% of triethylamine ICLOiJ was added.
Drip in minutes. After the dropwise addition, the mixture was stirred for 20 hours, and then the precipitate was removed by filtration.

Benzene was removed from the liquid by evaporation using an evaporator. The remaining residue is purified by silica gel force 2 using benzene as a developing solvent.
Styrene sulfonic acid 0-nitropendyl ester 1a09 was obtained as yellowish-brown crystals. The compound is
It is clear from the spectrum data shown below that this is the desired styrene sulfonic acid 0-nitrobenzyl ester.

1) Infrared absorption spectrum (Nujol method) 1520c1
n″″’ (c-Not extension! Stretching vibration 360α-”(s
-o stretching vibration) 1340 cm-' (C-No, stretching vibration) 1170
The crR-' (S-0 stretching vibration) infrared absorption spectrum is shown in FIG.

2)'H-NMR (solvent CDC4) ■ 5.48 ppm @7.76 ppm The 'H-NMR spectrum is shown in FIG.

Synthesis of polystyrene sulfonic acid 0-nitrobenzyl ester Styrene sulfone 0-nitrobenzyl ester 2.0
9. Benzene solution of azobisisobutyronitrile 2.9
m (containing 2 Owt% azobisisobutyronitrile) and benzene α2- in a flask, and according to the usual method,
Vacuum degassed. The flask was stirred at 70°C for 8 hours. The reaction product was purified in ethyl ether, filtered and dried to obtain α4g of folystyrenesulfonic acid O-nitrobenzyl ester as a brown precipitate. As a result of GPC measurement, the weight average molecular weight of the polymer was tOXl in terms of polystyrene.

Example 3 g of polystyrene sulfonic acid 〇-nitrobenzyl ester cL obtained in the synthesis example was mixed with 1.5 g of dimethylformamide.
The solution was applied onto a silicon wafer using a spin code method, and the wafer was further dried in a drying oven at 120°C for 3 minutes.
It was processed (prebaked) for 0 minutes. In this way, a 1.0 μm polystyrene sulfonic acid 0-nitrobenzyl ester thin film was formed on the silicon wafer.

Then, the desired area was exposed to KDeep UV light using PLA-501F (Canon). Then 10w
The exposed portion was dissolved in a t% sodium metasilicate aqueous solution to form a resist pattern on the wafer. The sensitivity was 50 rnJ/aA, and a positive pattern of 1 μmL L&S could be formed.

Dry etching resistance is determined by dry etching equipment I)K.
Resistance to reactive sputtering by CIF and gas was observed using M-451 model (manufactured by Nichiden Anelva). Etching speed of polysilicon substrate is 1400 A/
Compared to the win, in the case of the polymer of the present invention, it is 400 A
/ m1nK has become. From this, it is clear that the dry etching resistance is excellent.

[Brief explanation of drawings]

Figures 1 and 2 show the infrared absorption spectrum and 'FI-NMR of styrene sulfonic acid 〇-nitropendyl ester.
The spectrum is shown. Patent applicant: Toyo Soda Kogyo Co., Ltd. Transmission C9

Claims (1)

[Claims] (1) A photoresist material comprising a polymer containing a structural unit represented by the following general formula (1). ▲There are mathematical formulas, chemical formulas, tables, etc.▼(1) {R_1, R_2; Hydrogen or lower alkyl group