JPS649614B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a highly sensitive radiation-sensitive positive resist composition with improved performance and a solution thereof. Conventionally, when a coating film coated on a suitable substrate is irradiated with a predetermined amount of radiation, the main chain of the polymer bond in the irradiated part is cut, its molecular weight becomes smaller, and it becomes soluble, creating a so-called radiation-sensitive positive film. Polymeric materials for mold resists are known. For example, polymethyl methacrylate, which is known for its high resolution, can be irradiated with an electron beam with an irradiation dose of about 5 × 10 ^-5 coulombs/cm ² or more.
Only the irradiated portion becomes significantly soluble in solvents such as methyl isobutyl ketone and isoamyl acetate. This type of material can be used, for example, as a resist material for forming a mask for etching only very fine parts in the manufacturing process of semiconductor devices, or as a material for recording information using other radiation. However, most of the conventionally known radiation-sensitive positive resist materials, such as the above-mentioned polymethyl methacrylate, require a relatively large radiation dose to become soluble, that is, their sensitivity is low. Another drawback is that radiation irradiation must be carried out for a relatively long time in order to obtain a desired positive irradiation image. On the other hand, a few high-sensitivity positive electron beam resist materials that require relatively short irradiation times have problems such as low properties such as etching resistance, solvent resistance, and resolution, making them practical for semiconductor manufacturing processes. As a possible resist, there was no one that fully satisfied both parties. The present invention utilizes the above-mentioned conventional polymeric materials for radiation-sensitive positive resists to achieve significantly higher sensitivity, contrast, heat resistance, etc. by combining specific raw materials (monomers) and copolymerizing them. The purpose of this research was to obtain a highly sensitive radiation-sensitive positive resist composition and its solution with improved properties. The highly sensitive radiation-sensitive positive resist composition of the present invention contains i-propyl methacrylate monomer as a main component, and α
It is characterized by being copolymerized by adding one type of -position-substituted branched butyl acrylate monomer and a methyl methacrylate monomer in a fixed composition ratio. (In the formula, R ₁ is -CH ₃ , -C ₂ H ₅ , -C ₃ H ₇ , -CH ₂ CN,
_-CH2F , _-H2Cl , -CN, -F, -Cl group, _R2
represents s-butyl, i-butyl and t-butyl groups. ) According to the radiation-sensitive positive resist composition of the present invention comprising the above-mentioned copolymer, the radiation-sensitive resist composition is about 1/10 to 1/100 of that of conventional radiation-sensitive positive resist polymer materials. A sufficiently clear positive image can be obtained with a certain amount of radiation exposure, and its resolution, heat resistance, and etching resistance are almost comparable to those of PMMA/resist materials. The highly sensitive radiation-sensitive positive resist composition of the present invention has i-propyl methacrylate (hereinafter referred to as "A") monomer as a main component, and α-substituted branched butyl expressed by the general formula []. It is necessary to copolymerize acrylate (hereinafter referred to as "B") monomer and methyl methacrylate (hereinafter referred to as "C") monomer in a specific ratio, and B
The composition amount of the monomer contained in the copolymer is 10 to 40 mol%, and the composition amount of the C monomer is 5 to 20 mol%. If the amount of B is below this range, the solubility of this copolymer in a solvent will be too high, making it difficult to obtain appropriate development conditions and making it difficult to use with high sensitivity. Further, above this range, significant improvement in sensitivity is hindered. On the other hand, if the composition amount of C is below this range, the portions that have not been irradiated with radiation will swell significantly due to high-sensitivity development, and the glass transition point will drop significantly. Further, above this range, the sensitivity becomes extremely low. The copolymerization method is not particularly limited, and common polymerization methods such as emulsion polymerization, suspension polymerization, bulk polymerization, radical or anionic polymerization in a solution, and methods such as graft polymerization and living polymerization can be used. It is appropriately selected depending on the physical properties of the polymer, the desired molecular weight, degree of dispersion, etc. The copolymer polymer material for positive resists according to the present invention can be used in a molecular weight range comparable to that of other currently commonly used positive resist materials. That is, it has a form having a wide range of molecular weights ranging from 100,000 to several million millions, and in practice, a range of 300,000 to 3,000,000 is used, and is selected depending on various purposes. The upper limit of the molecular weight is determined by the fact that the solution viscosity of the resist material becomes too high and the working margin is significantly reduced, and the lower limit is determined by the fact that it becomes difficult to develop a good image and the etching resistance etc. decrease. The developing solvent for using the copolymer polymer material according to the present invention as a resist is a solvent that can dissolve the copolymer material uniformly and well, has an appropriate boiling point, and is a low-polymer solvent that has excellent spreadability for the polymer material. It is necessary that the viscosity is a volatile organic solvent. There are many suitable solvents, to name a few: toluene,
Aromatic solvents such as xylene and benzene, chlorinated solvents such as trichloroethylene and chlorobenzene, n
-propyl acetate, isoamyl acetate,
There are ester solvents such as ethyl cellosolve acetate, methyl cellosolve acetate, and t-butyl propionate, and ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, 4-methoxy-4-methylpentanone-2, and dipropyl ketone. However, the solvent is not limited to the above examples, and it is also possible to use a mixture of two or more solvents. A detailed explanation will be given below with reference to examples. Example 1 Ion-exchanged water was placed in a suitable reaction vessel, dissolved oxygen was expelled through nitrogen gas, and an emulsifier such as sodium alkylbenzene sulfonate was added thereto and mixed at a desired blending ratio. -Propyl methacrylate (A), t-butyl methacrylate (B) and methyl methacrylate (C)
Then add a small amount of an aqueous solution containing a redox polymerization initiator such as sodium persulfate and sodium bisulfite, and raise the reaction temperature.
After reacting for about 6 hours while maintaining the temperature at 60 to 80°C and stirring vigorously, the polymerized product is separated, further dissolved, and reprecipitated for purification. In this way, when the glass transition temperature is 80℃ or higher,
Copolymer compositions were obtained in which the proportions of B were 5, 15, 20, 30, 40, and 60 mol %, respectively. Next, each of the above copolymer compositions was dissolved in xylene, and this was applied onto a 3-inch silicon wafer using a spinner, and dried under predetermined conditions to form a coating film of the above copolymer with a thickness of about 0.5 μm. A surface was formed. Table 1 shows the electron beam irradiation dose (hereinafter referred to as "dose") required to obtain a clear positive image when the copolymer coating surface of each example of the present invention was irradiated with an electron beam at an acceleration voltage of 20 KV. Examples of developer solutions are shown.

[Table] As shown in Table 1, the copolymer composition according to the present invention has a copolymerization ratio of B of 45 mol% or less and a copolymerization ratio of C of 20 mol%. % or less, a clear positive image could be obtained at a dose of about 1/10 to 1/50 of that of conventional PMMA resists, and the resolution of fine patterns was also excellent. On the other hand, if the composition amount of B is 10 mol% or less and
When the composition amount is 5% or less (Reference Example 1), the sensitivity is very good, but swelling occurs, making it very difficult to perform proper development, and furthermore, pattern formability deteriorates, making it difficult to perform microfabrication. It is unsuitable as a resist material for Example 2 Dry nitrogen gas was introduced into a sufficiently dried appropriate reaction vessel, and after the atmosphere inside the vessel was sufficiently replaced with nitrogen, dehydrated and purified toluene was added, and the purified monomers were added in the blending ratio shown in Table 2. Add a small amount of a radical polymerization initiator, such as a peroxide such as benzoyl peroxide, or a radical generator such as azobisisobutyronitrile, and maintain the reaction temperature at 60 to 70°C for 48 hours. . After the polymerization was completed, purification was carried out in the same manner as in Example 1 to obtain a copolymer having a copolymer composition as shown in Table 2 and a glass transition point of 70° C. or higher.

[Table] These copolymer compositions were dissolved in respective developing solvents such as methyl cellosolve acetate, and Example 1
Electron beam irradiation was performed in the same manner as above. Table 2 summarizes the doses and developing solutions required to obtain clear positive images for each copolymer composition. The figure also shows electrosensitive characteristic curves obtained for Reference Example 3 and Example 2-2. In the figure, the vertical axis is the normalized film thickness of the resist after development, and the horizontal axis is the electron beam irradiation dose (dose). The blot on the vertical axis indicates the film thickness of the unirradiated area after development. Curve A shows the characteristics of Reference Example 3, and curve B shows the characteristics of Example 2-2. As is clear from the above results, the i-propyl methacrylate-i-butyl methacrylate copolymer (Reference Example 3) has a significantly high sensitivity of 0.07 μC/ ^cm2 , but as shown in the figure, it swells considerably during development. appear. On the other hand, an appropriate amount of methyl methacrylate (C)
(Example 2-
2) The glass transition point: Tg has increased from 90°C to 98°C, improving heat resistance, and as is clear from the figure, no swelling was observed during development, and the sensitivity was also low.
It was approximately the same level at 0.08 μC/cm ² . Example 2-4
Although the sensitivity was slightly lower in Sample No. 2-6, similar trends were observed, and the development characteristics were good and the ability to form fine patterns was excellent. Example 3 Dry nitrogen gas was introduced into a sufficiently dried appropriate reaction vessel, and after the atmosphere inside the vessel was sufficiently replaced with nitrogen, dehydrated and purified toluene was added, and the purified monomers were added in the blending ratio shown in Table 3. A small amount of an anionic polymerization initiator solution such as n-butyllithium was added, and the reaction temperature was maintained at around -70°C.
Incubate for 48 hours. After the polymerization was completed, purification was carried out in the same manner as in Example 1, and the results were as shown in Table 3.

[Table] A copolymer having a copolymer composition, a molecular weight of several hundred thousand to 1.5 million, a dispersity of 1.6 to 2.5, and a glass transition temperature of 70°C or higher was obtained. These copolymer compositions were dissolved in the respective developing solvents and applied on a 75 mm square chrome blank substrate in the same manner as in Example 1, dried, and then irradiated with an electron beam. Table 4 shows the dose, developer, and slope of the electron sensitivity curve required to obtain a clear positive image when the copolymer coating surface of each example of the present invention was irradiated with an electron beam at an accelerating voltage of 20 KV. This figure shows the γ value obtained from the above.

[Table] As is clear from the above results, although the radiation-sensitive positive resist material obtained by the present invention has high sensitivity, almost no swelling is observed during development, and the pattern formation property is also low. It was good and warm. Furthermore, when etching a chrome mask was attempted, it was confirmed that the mask had adhesion that could withstand wet etching of chromium and heat resistance that could withstand dry etching of chromium. By carrying out the present invention as described above, a polymeric material for radiation-sensitive positive electron beam resist that has much higher sensitivity and contrast than conventionally known PMMA resists and has less swelling during development. can be obtained. Generally, negative resists have problems in terms of post-polymerization effects and resolution when drawing, transferring, or recording patterns that have fine patterns of 1 μm or less using radiation and require precision of submicron or less. It is said that it is desirable to use a positive resist which has better resolution than using a resist, and the present invention is extremely effective when used for precise and minute processing or recording of patterns as described above. .

[Brief explanation of drawings]

The figure shows the electrosensitive characteristics of Reference Example 3 and Example 2-2 of the present invention.

Claims (1)

[Claims] 1 The main component is i-propyl methacrylate monomer (A), and has the general formula (In the formula, R ₁ is -CH ₃ , -C ₂ H ₅ , -C ₃ H ₇ , -CH ₂ CN,
_-CH2F , _-H2Cl , -CN, -F, -Cl group, _R2
represents s-butyl, i-butyl and t-butyl groups. ) and a methyl methacrylate monomer (C), and in the above copolymer, 10 to 40 of the above monomers (B) are Including mole%,
A radiation-sensitive positive resist composition containing 5 to 20 mol% of the above methyl methacrylate monomer (C).