JPH0354336B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a positive electron beam resist material that is highly sensitive to radiation such as electron beams and X-rays, has high resolution, and has excellent dry etching resistance. In order to use electron beam resists for manufacturing semiconductor devices such as ICs and LSIs in actual microfabrication, they are required to satisfy the following properties. : Must be highly sensitive to electron beams. : Must be high resolution. : Excellent dry etching resistance. Many materials for electron beam resists have been announced so far, but one that satisfies all of the above requirements has not yet been developed. Therefore, there are strong expectations in the electronics industry for the emergence of high-performance electron beam resist materials that can be used in actual processes. In addition, in terms of whether to use a negative resist or a positive resist, the trend towards finer images has been increasing in recent years, so there are particularly strong expectations for positive resists, which are easier to obtain high resolution. Typical positive electron beam resists developed so far include polybutene-1-sulfone (PBS) and polymethyl methacrylate (PMMA). Although PBS has very high sensitivity, it has poor dry etching resistance and does not have very high resolution. In other words, the required properties are not satisfied. PMMA has high resolution, but low sensitivity and poor dry etching resistance. In other words, the required properties are not satisfied. Polynorbornenesulfone (PNS) has also been developed as a positive resist material that overcomes the weak dry etching resistance, which is a common drawback of PBS and PMMA. However, PNS has low sensitivity and resolution. In other words, the required properties are not satisfied. PNS cannot be said to be a satisfactory resist material for use in actual processes. An object of the present invention is to provide a material for a positive electron beam resist that has excellent dry etching resistance, high sensitivity, and high resolution, that is, a material for a positive electron beam resist that satisfies all of the above-mentioned required properties. The above object of the present invention is achieved by a positive electron beam resist material characterized by having as an essential component a polymer having a basic unit represented by the following general formula in its molecular skeleton. (In the formula, R ₁ , R ₂ , R ₃ each represent hydrogen or a hydrocarbon residue having 1 to 6 carbon atoms, and R ₄ is (a) a hydrocarbon residue having 1 to 20 carbon atoms or (b) a carbon Represents one or more hydrogen atoms contained in a number of 1 to 20 hydrocarbon residues substituted with a fluorine atom. The polymer of the present invention usually consists of a compound represented by the general formula (A) and SO ₂ . It is obtained by copolymerizing. (In the formula, R ₁ to R ₄ are the same as above.) The compound represented by formula (A) is typically produced by the Diels-Alder reaction between cyclopentadiene and acrylic esters. (formula (A ₁ ) below). Additionally, compounds obtained by Diels-Alder reaction using methylcyclopentadiene instead of cyclopentadiene and methacrylic ester instead of acrylic ester, such as the following formula (A ₂ )～( _A4 )
Compounds shown in can also be preferably used.

【formula】

【formula】

【formula】

[Formula] (In the formula, R ₄ is the same as above) A radical catalyst is usually used as a catalyst for the copolymerization of the compound represented by formula (A) and SO ₂ at a temperature of -100°C to 100°C.
The reaction is carried out at a temperature of preferably -50°C to 0°C. In this case, a compound having an olefinic carbon=carbon double bond having 2 to 20 carbon atoms may be coexisting as a monomer. These olefins include, for example, ethylene, propylene, butene, pentene,
One or more types of hexene, cyclopentene, cyclohexene, styrene, etc. These olefins are preferably used in an amount of 50% by weight or less of the compound represented by formula (A). When these olefins are used, a copolymer in which olefin-SO ₂ - units are partially inserted into the molecular skeleton is obtained. These copolymers belong to so-called polysulfones. The above-mentioned copolymers can also be synthesized and used by other methods known for synthesizing polysulfones, such as oxidation of polysulfides. The molecular weight of these copolymers is usually a number average molecular weight of 10,000 to 1 million, preferably 30,000 to 1,000,000.
500,000 can be used in the present invention. Other organic materials can also be mixed with the polymers used in the invention. Examples of this organic material include novolak type phenolic resin, resol type phenolic resin, epoxy resin, petroleum resin, and the like. These organic materials are preferably used in an amount of 50% by weight or less of the polymer used in the present invention. The polymers used in the present invention are soluble in solvents such as chloroform, cyclohexanone, tetrahydrofuran, and dioxane. When the polymer of the present invention is used as a resist material, it can be dissolved in the above-mentioned solvent in an amount of 3 to 40% by weight, preferably 5% by weight.
Prepare a solution with a concentration of ~20% by weight. In the present invention, the resist material-containing solution is usually applied to the substrate using a rotary coating machine. Preheating can be performed as necessary after coating. The heating temperature is 100-200°C, preferably 140-160°C. A substrate coated with a positive resist is exposed to light using an electron beam or the like in a conventional manner, and only the exposed portions of the resist are decomposed to achieve the purpose. As the phenomenon liquid after electron beam exposure, a mixture of a good solvent such as chloroform, cyclohexanone, tetrahydrofura, dioxane, etc. and a poor solvent such as ethanol, osopropanol, toluene, etc. in an appropriate ratio can be used. The resist material of the present invention is characterized in that it has dry etching resistance equivalent to that of PNS, and has higher sensitivity and resolution than PNS.
This is a substituent

[Formula] (R is (a) a hydrocarbon residue having 1 to 20 carbon atoms or (b) one or more hydrogen atoms contained in a hydrocarbon residue having 1 to 20 carbon atoms substituted with a fluorine atom) This effect can only be achieved by introducing a (representing something) into the side chain of the skeleton. The reason for this effect is not clear, but the substituent

It is presumed that this is because the introduction of the formula increases the difference in dissolution rate in the developer between the electron beam exposed area and the unexposed area. Hereinafter, the present invention will be explained in detail based on Synthesis Examples, Examples, and Comparative Examples, but the present invention is not limited thereto. Synthesis example 1

Synthesis of [formula] (polymer) By carrying out the Diels-Alder reaction between cyclopentadiene and methyl acrylate at 30°C. was obtained with a yield of 90%. 76 g (0.5 mol) of the compound and 0.45 g (0.005 mol) of t-butyl hydroperoxide were dissolved in 1000 ml of cyclohexanone, and the solution was poured into a No. 2 flask equipped with a stirrer.
The internal temperature was maintained at -20° C. by stirring the contents while cooling the flask in a low-temperature bath, and 32 g (0.50 mol) of sulfur dioxide was blown into the flask little by little to carry out polymerization. After polymerization at −20° C. for 1 hour, the polymerized oil was added dropwise into 10 methanol to form a white precipitate. This precipitate was purified by dissolving it in chloroform and reprecipitating it into methanol. When dried under reduced pressure at 50℃ for 24 hours, the weight of the precipitate is 80
g (yield 74%). Elemental analysis, NMR analysis, and IR analysis confirmed that this precipitate was a 1/1 alternating copolymer of the compound and sulfur dioxide. When determining the molecular weight by GPC analysis using polystyrene as a standard, Mn: 4.6×
10 ⁴ , Mw: 14.0×10 ⁴ . Synthesis example 2

Synthesis of [Formula] (polymer) By Diels-Alder reaction between 2,2,2-trifluoroethyl acrylate and cyclopentadiene was synthesized, and then, in the same manner as in Synthesis Example 1, a 1/1 alternating copolymer of the compound and sulfur dioxide was synthesized. Mn: 8.2×10 ⁴ , Mw: 12.6×10 ⁴ . Polymerization example 3 Synthesis (polymer) By Diels-Alder reaction between a compound obtained by esterifying 2,2,3,3,4,4,5,5-octafluoropentanol with acrylic acid and cyclopentadiene. was synthesized, and then, in the same manner as in Synthesis Example 1, a 1/1 alternating copolymer of the compound and sulfur dioxide was synthesized. Mn: 3.5×10 ⁴ , Mw: 8.0×10 ⁴ . Comparative synthesis example 1 Synthesis of [Polynorbornenesulfone (PNS)] PNS was synthesized from norbornene and sulfur dioxide in the same manner as in Synthesis Example 1. Mn: 16.9× ¹⁰⁴ ,
Mw: 147× ¹⁰⁴ . Comparative Synthesis Example 2 Resist solution OEBR-1000 (manufactured by Tokyo Ohka Co., Ltd.), which is commercially available as polymethyl methacrylate (PMMA), was used. Examples 1 to 3 and Comparative Examples 1 to 2 The polymers obtained in Polymerization Examples 1 to 3 and the PNS obtained in Comparative Polymerization Example 1 were dissolved in cyclohexanone to prepare a 10% by weight solution. These solutions and PMMA commercially available resist solutions are
OEBR-1000 was coated on a silicon wafer to a thickness of about 0.5 μm using a spin coater. Next, this wafer was placed in a constant temperature bath that was purged with nitrogen.
Preheating was carried out for 1 hour at a temperature of 160°C. Electron beam resist evaluation equipment ERE- for electron beam exposure
301 (manufactured by Elionix Co., Ltd.) to
It was conducted under the condition of 20KV. After exposure, the film was developed using a developer appropriate for the material, and changes in film thickness were measured. A characteristic curve was created from the relationship between the exposure amount and the change in film thickness, and the sensitivity and contrast (an index of resolution; the higher the better) of the resist were determined. The plasma etching resistance of the coating film was evaluated using a plasma reactor PR-501 (manufactured by Yamato Scientific Co., Ltd.), and the resistance to CF ₄ plasma was evaluated based on the rate at which the film thickness decreased per unit time. The performance evaluation results are shown in Table 1, Figures 1 and 2.
Shown in the figure. As a result, Examples 1 to 3 using polymers
It can be seen that the sample has almost the same dry etching resistance as Comparative Example 1 using PNS, and has higher sensitivity than Comparative Example 1. Furthermore, the contrast values of Examples 1 to 3 are higher than those of Comparative Example 1, indicating that the resolution is higher. Also, PMMA
Comparative Example 2, which uses the same method, has high resolution but low sensitivity and poor etching resistance.

【table】 [Brief explanation of drawings]

The accompanying drawings are curves showing the performance of the resist material of the present invention in comparison with other resist materials.
The figure is a graph showing the sensitivity characteristics of the resist material in terms of the relationship between the normalized film thickness and the electron beam exposure amount, and FIG. 2 is the graph showing the dry etching resistance in terms of the relationship between plasma etching time and etching thickness.

Claims (1)

[Claims] 1 (In the formula, R ₁ , R ₂ , R ₃ each represent hydrogen or a hydrocarbon residue having 1 to 6 carbon atoms, and R ₄ is (a) a hydrocarbon residue having 1 to 20 carbon atoms or (b) a carbon 1 to 20 hydrocarbon residues in which one or more hydrogen atoms are substituted with fluorine atoms) A polymer having the basic unit represented by the above general formula in its molecular skeleton is an essential component. 1. A positive electron beam resist material comprising: