TWI686413B - Polymer and positive photoresist composition - Google Patents

Abstract

An object of the present invention is to provide a positive-type photoresist composition that can be used as a positive-type photoresist that sufficiently suppresses tailing and has high sensitivity, and can form a high-resolution photoresist pattern efficiently. The polymer system of the present invention includes α-methylstyrene units and α-methyl chloroacrylate units, the molecular weight distribution (Mw/Mn) is less than 1.25, and the proportion of components with a molecular weight less than 6000 is more than 0.5%. The positive photoresist composition of the present invention contains the above-mentioned polymer and solvent.

Description

Polymer and positive photoresist composition

The present invention relates to a polymer and a positive resist composition, and particularly to a polymer suitable for use as a positive resist and a positive resist composition containing the polymer.

Conventionally, in the fields of semiconductor manufacturing and the like, short-wavelength light such as ionizing radiation such as electron beams and ultraviolet rays (hereinafter, the combined radiation of short-wavelength radiation and short-wavelength is referred to as "free radiation, etc.") The main chain is cut, and the polymer having increased solubility in the developing solution uses a positive-cut photoresist which is a main chain cut type.

Also, for example, Patent Document 1 discloses a positive type photoresist formed from a copolymer of α-methylstyrene and α-methyl chloroacrylate units containing α-methylstyrene units and α-methyl acrylate units , As a positive type photoresist with high sensitivity main chain cutting type.

【Prior Technical Literature】 【Patent Literature】

[Patent Document 1] Japanese Patent Publication No. 8-3636

Here, by reducing the formation of the photoresist pattern required free radiation, etc. From the viewpoint of the amount of irradiation and the efficiency of forming a photoresist pattern, positive-type photoresist seeks to improve sensitivity while suppressing the phenomenon that a part of the exposed part is not sufficiently dissolved in the developer and remains (tailing).

However, the positive photoresist formed by the α-methylstyrene‧α-methyl chloroacrylate copolymer described in Patent Document 1 is not sufficiently sensitive, and the tailing cannot be sufficiently suppressed. In addition, in recent years, although the method of eliminating trailing by adjusting the process conditions in the development process (processing time and the rotation speed of the development stage in shower development) is also studied, the development process is easily complicated . Therefore, it is desired to improve the properties of the polymer constituting the positive photoresist, thereby enabling high sensitivity of the positive photoresist and suppression of smearing.

Therefore, an object of the present invention is to provide a polymer that can be used as a positive photoresist with high sensitivity and sufficient suppression of smearing.

In addition, an object of the present invention is to provide a positive-type photoresist composition capable of efficiently forming a high-resolution photoresist pattern.

In order to achieve the above-mentioned object, the present inventors conducted earnest research. The present inventors found that an α-methylstyrene‧α-methyl chloroacrylate copolymer having a predetermined molecular weight and a proportion of components with a molecular weight of less than 6000 exceeding the predetermined value can be used well as a sufficient suppression of drag The invention is completed with a positive photoresist with a tail and high sensitivity.

That is, this invention aims to solve the above-mentioned problems beneficially, and the polymer of the present invention is characterized by including α-methylstyrene units and α-methyl chloroacrylate units, and the molecular weight distribution (Mw/ Mn) is less than 1.25, and the proportion of components with a molecular weight of less than 6000 is more than 0.5%. The molecular weight distribution (Mw/Mn) is less than 1.25, and the proportion of components with a molecular weight of less than 6000 is more than 0.5% of α-methylstyrene‧α-methyl chloroacrylate copolymer, when used as a positive photoresist The tail can be fully suppressed, and the sensitivity is high, it can be used as a positive photoresist.

Here, in the present invention, "molecular weight distribution (Mw/Mn)" refers to the ratio of weight average molecular weight (Mw) to number average molecular weight (Mn). In addition, in the present invention, "number average molecular weight (Mn)" and "weight average molecular weight (Mw)" can be measured by gel permeation chromatography. In addition, in the present invention, the "proportion of components with a molecular weight of less than 6000" can be obtained by using gel permeation chromatography, and the total area of the peaks of the components with a molecular weight of less than 6000 in the chromatogram (B ) Is calculated by calculating the ratio of the total area (A) of the peaks in the chromatogram (=(B/A)x100%).

Here, the polymer of the present invention preferably has a ratio of components with a molecular weight of less than 6000 to 3.0% or more. If the proportion of components with a molecular weight of less than 6000 is 3.0% or more, the sensitivity can be sufficiently improved when used as a positive photoresist, and tailing can be further suppressed.

In addition, the polymer of the present invention preferably has a proportion of components having a molecular weight of more than 20,000 of 70% or less. If the proportion of components having a molecular weight of more than 20,000 is 70% or less, the sensitivity can be sufficiently improved when used as a positive photoresist, and tailing can be further suppressed.

Here, in the present invention, "the ratio of components with a molecular weight of more than 20,000" can be obtained by using a gel permeation chromatography chromatogram, and the total area of the peaks of the components with a molecular weight of more than 20,000 in the chromatogram (C) The ratio of the total area (A) of the peaks in the chromatogram (=(C/A)x100%) was calculated and calculated.

Furthermore, the polymer of the present invention is based on the weight average score The sub-weight (Mw) is preferably 25,000 or less. If the weight average molecular weight (Mw) is 25,000 or less, the sensitivity can be sufficiently improved when used as a positive photoresist, and tailing can be further suppressed.

In addition, this invention is aimed at solving the above-mentioned problems favorably, and the positive-type photoresist composition of the present invention is characterized by including any of the above-mentioned polymers and solvents. If the polymer is included as a positive photoresist, a high-resolution photoresist pattern can be efficiently formed.

The polymer of the present invention can provide a positive photoresist with sufficiently suppressed tailing and high sensitivity.

In addition, according to the positive-type photoresist composition of the present invention, a high-resolution photoresist pattern can be efficiently formed.

Hereinafter, embodiments of the present invention will be described in detail.

Here, the polymer of the present invention can be irradiated with short-wavelength light such as electron beams and ultraviolet rays to cut the main chain to achieve a low molecular weight, and can be used as a positive type of main chain cutting type. Photoresist. In addition, the positive resist composition of the present invention contains the polymer of the present invention as a positive resist.

(polymer)

The polymer of the present invention is characterized by an α-methylstyrene unit containing α-methylstyrene units and α-methyl chloroacrylate units, a copolymer of α-methyl chloroacrylate and a molecular weight distribution (Mw/Mn) of Less than 1.25, the molecular weight is less than 6000 The percentage of points is more than 0.5%. Furthermore, the polymer of the present invention contains a structural unit derived from an α-chloroacrylate having a chlorine group (-Cl) in the α position (α-chloroacrylate unit). If free radiation is irradiated (eg, Electron beam, KrF laser, ArF laser, EUV laser, etc.), the main chain is easily cut and the molecular weight is reduced. In addition, since the molecular weight distribution (Mw/Mn) of the polymer of the present invention is less than 1.25 and the proportion of components with a molecular weight of less than 6000 is more than 0.5%, the tailing when used as a positive type photoresist is sufficiently suppressed, and the sensitivity High, can be used as a positive type photoresist of main chain cutting type.

<α-methylstyrene unit>

Here, the α-methylstyrene unit is a structural unit derived from α-methylstyrene. In addition, since the polymer of the present invention has an α-methylstyrene unit, when used as a positive photoresist, it exhibits excellent dry etching resistance due to the protective stability of the benzene ring.

In addition, the polymer of the present invention preferably contains α-methylstyrene units in a proportion of 30 mol% or more and 70 mol% or less.

<α-methyl acrylate unit>

In addition, the α-methyl chloroacrylate unit is a structural unit derived from α-methyl chloroacrylate. In addition, since the polymer of the present invention has α-methyl chloroacrylate units, the main chain is easily cleaved by detachment of chlorine atoms and β cleavage reactions when free radiation or the like is irradiated. Therefore, the positive resist formed by the polymer of the present invention shows high sensitivity.

In addition, the polymer of the present invention preferably contains α-methyl chloroacrylate units in a proportion of 30 mol% or more and 70 mol% or less.

<Molecular weight distribution>

The molecular weight distribution (Mw/Mn) of the polymer of the present invention is required to be less than 1.25, preferably 1.20 or less, preferably 1.18 or less, and more preferably 1.17 or less. When the molecular weight distribution (Mw/Mn) of the polymer is 1.25 or more, the tailing when used as a positive photoresist cannot be sufficiently suppressed, and the sensitivity cannot be sufficiently improved. From the viewpoint of ease of preparation of the polymer, the molecular weight distribution (Mw/Mn) of the polymer of the present invention is preferably 1.10 or more.

[Weight average molecular weight]

The weight average molecular weight (Mw) of the polymer of the present invention is preferably 25,000 or less, preferably 18,000 or less, more preferably 12,000 or less, particularly preferably 10,000 or less, and most preferably 9,000 or less. If the weight average molecular weight (Mw) of the polymer is 25,000 or less, the sensitivity is sufficiently improved when used as a positive photoresist, and tailing can be further suppressed. In addition, from the viewpoint of ensuring the formability of the photoresist pattern, the weight average molecular weight (Mw) of the polymer of the present invention is preferably 7,000 or more.

<number average molecular weight>

The number average molecular weight (Mn) of the polymer of the present invention is preferably 20,000 or less, more preferably 16,000 or less, even more preferably 10,000 or less, and particularly preferably 8,000 or less. If the number average molecular weight (Mn) of the polymer is 20,000 or less, the sensitivity when used as a positive photoresist can be sufficiently improved, and the tailing can be further suppressed. In addition, from the viewpoint of ensuring the formability of the photoresist pattern, the number average molecular weight (Mn) of the polymer of the present invention is preferably 6000 or more.

<Proportion of components with molecular weight less than 6000>

In the polymer of the present invention, the proportion of components with a molecular weight of less than 6000 is necessary to exceed 0.5%, preferably 3.0% or more, more preferably 8.0% or more, and 9.0% or more To be even better, more than 20% is particularly good. When the proportion of the component with a molecular weight of less than 6000 is 0.5% or less, smearing when used as a positive photoresist cannot be suppressed, and sensitivity cannot be sufficiently improved. In addition, from the viewpoint of ensuring the formability of the photoresist pattern, the proportion of the component having a molecular weight of less than 6000 is preferably 45% or less.

<Proportion of components with molecular weight exceeding 20,000>

In the polymer of the present invention, the proportion of components having a molecular weight of more than 20,000 is preferably 70% or less, preferably 45% or less, more preferably 20% or less, particularly preferably 13% or less, and most preferably 4% or less. If the proportion of components with a molecular weight of more than 20,000 is 70% or less, the sensitivity when used as a positive type photoresist can be sufficiently improved, and tailing can be further suppressed.

<Proportion of components with a molecular weight of more than 40,000>

In the polymer of the present invention, the proportion of components having a molecular weight of more than 40,000 is preferably 4.0% or less, preferably 1.0% or less, and the polymer of the present invention is more preferably not containing components having a molecular weight of more than 40,000. If the proportion of components with a molecular weight of more than 40,000 is 4.0% or less, the sensitivity when used as a positive type photoresist can be sufficiently improved, and tailing can be further suppressed.

In addition, in the present invention, the "proportion of components with a molecular weight of more than 40,000" can be obtained by using a chromatogram obtained by gel permeation chromatography. The ratio of the total area (A) of the peaks in the chromatogram (=(D/A)x100%) is calculated and calculated.

<Proportion of components with molecular weight exceeding 60,000>

In the polymer of the present invention, the proportion of components having a molecular weight of more than 60,000 is preferably 1.0% or less, and the polymer of the present invention is more preferably not containing components having a molecular weight of more than 60,000. If the ratio of components with a molecular weight of more than 60,000 is Below 1.0%, the sensitivity when used as a positive photoresist can be sufficiently improved, and the tailing can be further suppressed.

In addition, in the present invention, "the ratio of components with a molecular weight of more than 60,000" can be obtained by using a chromatogram obtained by gel permeation chromatography. The total area of the peaks of the components with a molecular weight of more than 60,000 in the chromatogram (E) The ratio of the total area (A) of the peaks in the chromatogram (=(E/A)×100%) was calculated and calculated.

(Method of preparing polymer)

Further, for example, by polymerizing a monomer composition containing α-methylstyrene and α-methyl chloroacrylate, and purifying the obtained polymer, a polymer having the above-mentioned properties can be prepared.

In addition, the composition, molecular weight distribution, weight average molecular weight and number average molecular weight of the polymer, and the proportion of each molecular weight component in the polymer can be adjusted by changing the polymerization conditions and purification conditions. Specifically, for example, if the polymerization temperature is increased, the weight average molecular weight and the number average molecular weight can be reduced. In addition, if the polymerization time is shortened, the weight average molecular weight and the number average molecular weight can be reduced.

<Polymerization of monomer composition>

Here, as the monomer composition for preparing the polymer of the present invention, a monomer containing α-methylstyrene and α-methyl chloroacrylate, a solvent, a polymerization initiator, and optionally added additives can be used mixture. In addition, the polymerization of the monomer composition can be carried out by a known method. Among them, it is preferable to use cyclopentanone or the like as a solvent, and it is preferable to use a radical polymerization initiator such as azobisisobutyronitrile as a polymerization initiator.

In addition, the composition of the polymer can be adjusted by changing the content ratio of each monomer used in the monomer composition for polymerization. In addition, by changing the poly The amount of the initiator is adjusted to adjust the proportion of the polymer containing high molecular weight components. For example, if the amount of the polymerization initiator is reduced, the proportion of high molecular weight components can be increased.

In addition, the polymer obtained by polymerizing the monomer composition is not particularly limited. After adding a good solvent such as tetrahydrofuran to the solution containing the polymer, the solution added with the good solvent is dropped into a poor solvent such as methanol (poor The solvent can be recovered by solidifying the polymer and can be purified as described below.

<purification of polymer>

The purification method used when purifying the obtained polymer to obtain a polymer having the above-mentioned properties is not particularly limited, and known purification methods such as a reprecipitation method and column chromatography can be used. Among them, the reprecipitation method is preferably used as the purification method.

In addition, the purification of the polymer may be repeated several times.

Furthermore, the purification of the polymer by the reprecipitation method is preferably, for example, as follows. After the obtained polymer is dissolved in a good solvent such as tetrahydrofuran, the resulting solution is dropped into a mixed solvent of a good solvent such as tetrahydrofuran and a poor solvent such as methanol. To precipitate part of the polymer. In this way, if the polymer solution is dropped into a mixed solvent of a good solvent and a poor solvent to purify the polymer, the molecular weight of the obtained polymer can be easily adjusted by changing the types and mixing ratios of the good solvent and the poor solvent Distribution, weight average molecular weight, number average molecular weight, and ratio of low molecular weight components. Specifically, for example, the higher the ratio of the good solvent in the mixed solvent, the higher the molecular weight of the polymer precipitated in the mixed solvent.

In addition, in the case of purifying the polymer by the reprecipitation method, as long as the desired properties are satisfied, the polymer precipitated in the mixed solvent of the good solvent and the poor solvent can be used, or the polymerization not precipitated in the mixed solvent can be used. Things (also That is, a polymer dissolved in a mixed solvent) serves as the polymer of the present invention. Here, the polymer not precipitated in the mixed solvent can be recovered from the mixed solvent by a known method such as concentration drying.

(Positive photoresist composition)

The positive-type photoresist composition of the present invention contains the above-mentioned polymer and solvent, and optionally, further contains known additives that can be formulated with the photoresist composition. Furthermore, since the positive resist composition of the present invention contains the above-mentioned polymer as a positive resist, the photoresist film obtained by coating and drying the positive resist composition of the present invention can form a high resolution well Degree pattern.

<solvent>

In addition, a known solvent that can dissolve the above-mentioned polymer solvent can be used as the solvent. Among them, from the viewpoint of obtaining a moderately viscous positive photoresist composition and improving the coatability of the positive photoresist composition, it is preferable to use anisole as a solvent.

【Example】

Although the present invention will be specifically described below based on examples, the present invention is not limited to these examples. In addition, in the following description, "%" and "parts" indicating quantities are quality standards unless otherwise specified.

Moreover, in the examples and comparative examples, the weight average molecular weight, number average molecular weight and molecular weight distribution of the polymer, the proportion of each molecular weight component in the polymer, and the sensitivity and drag of the positive photoresist formed by the polymer Tail, measured and evaluated by the following method.

<weight average molecular weight, number average molecular weight and molecular weight distribution>

The weight average molecular weight (Mw) and number average molecular weight (Mn) of the obtained polymer were measured by gel permeation chromatography, and the molecular weight distribution (Mw/Mn) was calculated.

Specifically, using a gel permeation chromatograph (manufactured by Dongchu, HLC-8220), using tetrahydrofuran as a developing solvent, and using standard polystyrene as a conversion value, the weight average molecular weight (Mw) and number average of the polymer are obtained Molecular weight (Mn). Furthermore, the molecular weight distribution (Mw/Mn) was calculated.

<Proportion of components of each molecular weight in the polymer>

Using a gel permeation chromatograph (manufactured by Dong Chu, HLC-8220), using tetrahydrofuran as a developing solvent, a chromatogram of the polymer was obtained. From the obtained chromatogram, the total area of the peaks (A), the total area of the peaks of the components with a molecular weight of less than 6000 (B), the total area of the peaks of the components with a molecular weight of more than 20,000 (C), and the molecular weight are The total area (D) of the peaks of components exceeding 40000 and the total area (E) of the peaks of components exceeding 60,000. In addition, the ratio of each molecular weight component is calculated using the following formula.

Proportion of components with molecular weight less than 6000 (%) = (B/A) x100

Proportion of components with a molecular weight exceeding 20,000 (%) = (C/A) x 100

Ratio of components with molecular weight exceeding 40000 (%) = (D/A) x100

Proportion of components with a molecular weight exceeding 60,000 (%) = (E/A) x 100

<sensitivity>

Using a spin coater (manufactured by Mikasa, MS-A150), the positive photoresist composition was coated on a silicon wafer with a diameter of 4 inches to a thickness of 500 nm. Then, the applied positive-type photoresist composition was heated on a hot plate at a temperature of 180° C. for 3 minutes to form a photoresist film on the silicon wafer. Then, using an electron beam lithography apparatus (manufactured by Elionix, ELS-5700), multiple lithography of a pattern (size 500 μm×500 μm) with different irradiation doses of electron beams was applied to the photoresist film, and amyl acetate (manufactured by Ruion, Japan) was used. ZED-N50) As a developer for photoresist, after a 1 minute development process at a temperature of 23° C., rinse with isopropyl alcohol for 10 seconds. In addition, the irradiation amount of the electron beam is in the range of 4 μC to 152 μC, and is changed by 4 μC each time. Then, the thickness of the photolithography portion of the photoresist film was measured with an optical film thickness agent (made by Dainippon Screen, Lambda Ace), and the common logarithm indicating the total irradiation amount of the electron beam and the residual film rate of the photoresist film after development ( = Sensitivity curve of the relationship between the film thickness of the developed photoresist film/the film thickness of the photoresist film formed on the silicon wafer). In addition, the obtained sensitivity curve (horizontal axis: common logarithm of the total irradiation amount of the electron beam; vertical axis: residual film rate of the photoresist film (0≦residual film rate≦1.00)) has a residual film rate of 0.20 to 0.80 Range, fitting a quadratic function to the sensitivity curve, making a straight line connecting the point of the residual film rate 0 and the point of the residual film rate 0.50 on the resulting quadratic function (a function of the common logarithm of the residual film rate and the total exposure) (Approximate line of the slope of the sensitivity curve). Then, when the residual film rate of the obtained straight line is 0, the total irradiation amount Eth (μC/cm ² ) of the electron beam is obtained. And evaluated according to the following criteria. The smaller the value of Eth, the higher the sensitivity of the photoresist.

A: Eth is less than 55μC/cm ²

B: Eth is 55μC / cm ² or more and less than 60μC / cm ²

C: Eth is 60μC/cm ² or more

<trailing>

Similar to the evaluation of "sensitivity", a photoresist film is formed on a silicon wafer, and a sensitivity curve is prepared. In addition, from the obtained sensitivity curve (horizontal axis: common logarithm of the total irradiation amount of the electron beam; vertical axis: residual film rate of the photoresist film (0≦residual film rate≦1.00)), the residual film rate is obtained from 0.1 up to 0.01 E becomes required irradiation amount of the electron beam _{1 (μC} / cm ^2), the residual film rate becomes 0.07 to 0.01 until the desired amount of irradiation of the electron beam ^{_{E 2 (μC / cm 2)}} , and the residual film rate The amount of electron beam exposure E ₃ (μC/cm ² ) required from 0.05 to 0.01 is evaluated based on the following criteria. The smaller the values of E ₁ , E ₂ and E ₃ , the higher the solubility of the exposed photoresist film, which means that tailing is suppressed.

[Trailing (1)-E-beam exposure E ₁ -]

A: E ₁ is 3μC/cm ² or less

B: E ₁ is more than ^{3μC / cm 2, 5μC / cm} 2 or less

C: E ₁ is more than 5μC/cm ² and 10μC/cm ² or less

D: E ₁ is more than 10μC/cm ² and 15μC/cm ² or less

E: E ₁ is more than 15μC/cm ²

[Trailing (2)-E-beam exposure E ₂ -]

A: E ₂ is less than 2μC/cm ²

B: E ₂ exceeding ^{2μC / cm 2, 5μC / cm} 2 or less

C: E ₂ is more than 5μC/cm ² and 10μC/cm ² or less

D: E ₂ is more than 10 μC/cm ² and 15 μC/cm ² or less

E: E ₂ is more than 15μC/cm ²

[Trailing (3)-E-beam exposure E ₃ -]

A: E ₃ is less than 3μC/cm ²

B: E ₃ is more than ^{3μC / cm 2, 5μC / cm} 2 or less

C: E ₃ is more than 5μC/cm ² and 10μC/cm ² or less

D: E ₃ is more than 10μC/cm ²

(Example 1)

<modulation of polymer>

[Polymerization of monomer composition]

Will contain as monomers 3.0g of α-chloroacrylate and α-methylstyrene A monomer composition of 6.88 g, 2.47 g of cyclopentanone as a solvent and 0.08728 g of azobisisobutyronitrile as a polymerization initiator was placed in a glass container, the glass container was sealed and replaced with nitrogen, and under a nitrogen atmosphere, Stir in a constant temperature bath at 78°C for 6.5 hours. Then, after returning to room temperature and exposing the glass container to the atmosphere, 30 g of tetrahydrofuran (THF) was added to the resulting solution. Then, the solution added with THF was dropped into 300 g of methanol to precipitate a polymer. Then, the solution containing the precipitated polymer was filtered with a Kiriyama funnel to obtain a white coagulum (polymer). The weight average molecular weight (Mw) of the obtained polymer was 17,000, and the molecular weight distribution (Mw/Mn) was 1.46. In addition, the obtained polymer contained 50 mol% each of α-methylstyrene units and α-methyl chloroacrylate units.

[Purification of polymer]

Next, the obtained polymer was dissolved in 100 g of THF, and the resulting solution was dropped into a mixed solvent of 500 g of THF and 500 g of methanol (MeOH) to make a white coagulum (containing α-methylstyrene units and The polymer of α-methyl chloroacrylate unit) is precipitated. Then, the solution containing the precipitated polymer was filtered with a Kiriyama funnel to obtain a white polymer. In addition, the weight average molecular weight, number average molecular weight and molecular weight distribution, and the proportion of each molecular weight component in the polymer were measured for the obtained polymer. The results are shown in Table 1.

<Preparation of positive photoresist composition>

The obtained polymer was dissolved in anisole as a solvent, and a photoresist solution (positive photoresist composition) having a polymer concentration of 11% by mass was prepared. Also, evaluate the sensitivity and tailing of the photoresist. The results are shown in Table 1.

(Example 2)

In addition to the use of azobis as a polymerization initiator when polymerizing the monomer composition The amount of isobutyronitrile was changed to 0.10910 g, and the polymer, polymer, and positive photoresist composition were prepared in the same manner as in Example 1. In addition, measurement and evaluation were performed in the same manner as in Example 1. The results are shown in Table 1.

In addition, the weight-average molecular weight (Mw) of the polymer before purification was 15,000, and the molecular weight distribution (Mw/Mn) was 1.42.

(Example 3)

The polymer, polymer, and positive photoresist composition were prepared in the same manner as in Example 1, except that the amount of azobisisobutyronitrile used as a polymerization initiator during polymerization of the monomer composition was changed to 0.21821 g. . In addition, measurement and evaluation were performed in the same manner as in Example 1. The results are shown in Table 1.

In addition, the weight average molecular weight (Mw) of the polymer before purification was 10,000, and the molecular weight distribution (Mw/Mn) was 1.47.

(Example 4)

In addition to changing the amount of azobisisobutyronitrile used as the polymerization initiator during the polymerization of the monomer composition to 0.32731 g, and using a mixed solvent of 450 g of THF and 550 g of methanol as the mixed solvent during polymer purification Except for the rest, the polymer, the polymer, and the positive resist composition were prepared in the same manner as in Example 1. And the same measurement and evaluation as Example 1 were performed. The results are shown in Table 1.

In addition, the weight-average molecular weight (Mw) of the polymer before purification was 8,200, and the molecular weight distribution (Mw/Mn) was 1.48.

(Example 5)

In addition to changing the amount of azobisisobutyronitrile used as the polymerization initiator during the polymerization of the monomer composition to 0.43641 g, and using a mixed solvent of 450 g of THF and 550 g of methanol as the mixed solvent during polymer purification In addition, the rest and implementation Example 1 prepared a polymer, a polymer, and a positive photoresist composition in the same manner. And the same measurement and evaluation as Example 1 were performed. The results are shown in Table 1.

In addition, the weight average molecular weight (Mw) of the polymer before purification was 6,700, and the molecular weight distribution (Mw/Mn) was 1.48.

(Example 6)

In addition to changing the amount of azobisisobutyronitrile used as a polymerization initiator during the polymerization of the monomer composition to 0.54552 g, and using a mixed solvent of 400 g of THF and 600 g of methanol as the mixed solvent during the purification of the polymer Except for the rest, the polymer, the polymer, and the positive resist composition were prepared in the same manner as in Example 1. And the same measurement and evaluation as Example 1 were performed. The results are shown in Table 1.

In addition, the weight-average molecular weight (Mw) of the polymer before purification was 5900, and the molecular weight distribution (Mw/Mn) was 1.47.

(Example 7)

In addition to changing the amount of azobisisobutyronitrile used as the polymerization initiator during the polymerization of the monomer composition to 0.81827 g, and using a mixed solvent of 350 g of THF and 650 g of methanol as the mixed solvent during polymer purification Except for the rest, the polymer, the polymer, and the positive resist composition were prepared in the same manner as in Example 1. And the same measurement and evaluation as Example 1 were performed. The results are shown in Table 1.

In addition, the weight average molecular weight (Mw) of the polymer before purification was 5000, and the molecular weight distribution (Mw/Mn) was 1.43.

(Example 8)

In addition to changing the amount of azobisisobutyronitrile used as a polymerization initiator during the polymerization of the monomer composition to 1.09103 g, and the use of a mixed solvent of 300 g of THF and 700 g of methanol as the mixed solvent for the purification of the polymer In addition, the rest and implementation Example 1 prepared a polymer, a polymer, and a positive photoresist composition in the same manner. And the same measurement and evaluation as Example 1 were performed. The results are shown in Table 1.

In addition, the weight-average molecular weight (Mw) of the polymer before purification was 4000, and the molecular weight distribution (Mw/Mn) was 1.38.

(Comparative example 1)

The amount of azobisisobutyronitrile used as a polymerization initiator during the polymerization of the monomer composition was changed to 0.01091 g, and the polymerization was recovered without the purification of the polymer, but was recovered by filtration when polymerizing the monomer composition The polymer was used directly as a polymer to prepare a positive-type photoresist composition, except that a polymer (a polymer containing α-methylstyrene units and α-methyl chloroacrylate units) was prepared in the same manner as in Example 1. And positive photoresist composition. And the same measurement and evaluation as Example 1 were performed. The results are shown in Table 2.

(Comparative example 2)

In addition to changing the amount of azobisisobutyronitrile used as a polymerization initiator during the polymerization of the monomer composition to 0.01091 g, and using a mixed solvent of 600 g of THF and 400 g of methanol as the mixed solvent during the purification of the polymer Except for the rest, the polymer, the polymer, and the positive resist composition were prepared in the same manner as in Example 1. And the same measurement and evaluation as Example 1 were performed. The results are shown in Table 2.

In addition, the weight average molecular weight (Mw) of the polymer before purification was 55,000, and the molecular weight distribution (Mw/Mn) was 1.85.

(Comparative example 3)

<modulation of polymer>

[Polymerization of monomer composition]

In addition to the polymerization initiator used in the polymerization of the monomer composition The amount of azisobutyronitrile was changed to 0.01091 g, and the rest was polymerized in the same manner as in Example 1 to obtain a polymer. In addition, the weight average molecular weight (Mw) of the polymer was 55,000, and the molecular weight distribution (Mw/Mn) was 1.85.

[Purification of polymer]

The obtained polymer was dissolved in 100 g of THF, and the resulting solution was dropped into a mixed solvent of 600 g of THF and 400 g of methanol to precipitate a white coagulum. Then, the solution containing the coagulum was filtered with a Tongshan funnel, and the filtrate was recovered. Furthermore, the filtrate was concentrated and dried to obtain a white coagulum (a polymer containing α-methylstyrene units and α-methyl acrylate units). In the same manner as in Example 1, the weight average molecular weight, number average molecular weight and molecular weight distribution, and the proportion of each molecular weight component in the polymer were measured for the obtained polymer. The results are shown in Table 2.

<Preparation of positive photoresist composition>

A positive photoresist composition was prepared in the same manner as in Example 1, except that the polymer prepared as described above was used. In addition, evaluation was performed in the same manner as in Example 1. The results are shown in Table 2.

(Comparative example 4)

<modulation of polymer>

[Polymerization of monomer composition]

The monomer composition was polymerized in the same manner as in Example 1 except that the amount of azobisisobutyronitrile used as a polymerization initiator during polymerization of the monomer composition was changed to 0.01091 g to obtain a polymer. In addition, the weight average molecular weight (Mw) of the polymer was 55,000, and the molecular weight distribution (Mw/Mn) was 1.85.

[Purification of polymer]

The obtained polymer was dissolved in 100 g of THF, and the resulting solution was dropped into 600 g In the mixed solvent of THF and 400g of methanol, white coagulum precipitated. Then, the solution containing the coagulated substance was filtered with a Tongshan funnel to obtain a white coagulated substance precipitated. The weight-average molecular weight (Mw) of the obtained coagulum was 65,000, and the molecular weight distribution (Mw/Mn) was 1.47.

Next, the obtained coagulated product was dissolved again in 100 g of THF, and the resulting solution was dropped again into a mixed solvent of 650 g of THF and 350 g of methanol to precipitate white coagulated product again. Then, the solution containing the coagulated substance precipitated again was filtered with a Tongshan funnel, and the filtrate was recovered. Furthermore, the filtrate was concentrated and dried to obtain a white coagulum (a polymer containing α-methylstyrene units and α-methyl acrylate units). In the same manner as in Example 1, the weight average molecular weight, number average molecular weight and molecular weight distribution, and the proportion of each molecular weight component in the polymer were measured for the obtained polymer. The results are shown in Table 2.

<Preparation of positive photoresist composition>

A positive photoresist composition was prepared in the same manner as in Example 1, except that the polymer prepared as described above was used. In addition, evaluation was performed in the same manner as in Example 1. The results are shown in Table 2.

(Comparative example 5)

In addition to changing the amount of azobisisobutyronitrile used as a polymerization initiator during the polymerization of the monomer composition to 0.02182 g, and using a mixed solvent of 600 g of THF and 400 g of methanol as a mixture during the purification of the polymer The polymer, the polymer, and the positive resist composition were prepared in the same manner as in Example 1 except for the solvent. And the same measurement and evaluation as Example 1 were performed. The results are shown in Table 2.

In addition, the weight-average molecular weight (Mw) of the polymer before purification was 35,000, and the molecular weight distribution (Mw/Mn) was 1.60.

(Comparative example 6)

In addition to changing the amount of azobisisobutyronitrile used as the polymerization initiator during the polymerization of the monomer composition to 0.02182 g, and using a mixed solvent of 550 g of THF and 450 g of methanol as the mixed solvent during polymer purification Except for the rest, the polymer, the polymer, and the positive resist composition were prepared in the same manner as in Example 1. And the same measurement and evaluation as Example 1 were performed. The results are shown in Table 2.

In addition, the weight-average molecular weight (Mw) of the polymer before purification was 35,000, and the molecular weight distribution (Mw/Mn) was 1.60.

(Comparative example 7)

In addition to changing the amount of azobisisobutyronitrile used as the polymerization initiator during the polymerization of the monomer composition to 0.03273 g, and using a mixed solvent of 550 g of THF and 450 g of methanol as the mixed solvent during polymer purification Except for the rest, the polymer, the polymer, and the positive resist composition were prepared in the same manner as in Example 1. And the same measurement and evaluation as Example 1 were performed. The results are shown in Table 2.

In addition, the weight average molecular weight (Mw) of the polymer before purification was 29,000, and the molecular weight distribution (Mw/Mn) was 1.56.

(Comparative Example 8)

In addition to changing the amount of azobisisobutyronitrile used as the polymerization initiator during the polymerization of the monomer composition to 0.04364 g, and using a mixed solvent of 550 g of THF and 450 g of methanol as the mixed solvent during polymer purification Except for the rest, the polymer, the polymer, and the positive resist composition were prepared in the same manner as in Example 1. And the same measurement and evaluation as Example 1 were performed. The results are shown in Table 2.

In addition, the weight average molecular weight (Mw) of the polymer before purification was 24,000, and the molecular weight distribution (Mw/Mn) was 1.53.

(Comparative Example 9)

In addition to changing the amount of azobisisobutyronitrile used as a polymerization initiator during the polymerization of the monomer composition to 0.06546 g, and using a mixed solvent of 550 g of THF and 450 g of methanol as the mixed solvent during polymer purification Except for the rest, the polymer, the polymer, and the positive resist composition were prepared in the same manner as in Example 1. And the same measurement and evaluation as Example 1 were performed. The results are shown in Table 2.

In addition, the weight average molecular weight (Mw) of the polymer before purification was 20,000, and the molecular weight distribution (Mw/Mn) was 1.48.

It can be understood from Tables 1 and 2 that examples 1 to 8 using polymers having a molecular weight distribution (Mw/Mn) of less than 1.25 and a molecular weight of less than 6000 in the proportion of more than 0.5% can provide tailing Positive photoresist that is fully suppressed and has high sensitivity.

Industrial possibilities

The polymer of the present invention can provide a positive photoresist with sufficiently suppressed tailing and high sensitivity.

In addition, the positive-type photoresist composition of the present invention can efficiently form a high-resolution photoresist pattern.

Claims (4)

A polymer comprising: α-methylstyrene units and α-methyl chloroacrylate units, wherein the molecular weight distribution (Mw/Mn) is 1.18 or less, and the proportion of components with a molecular weight of less than 6000 is more than 0.5%, weight average The molecular weight (Mw) is 13,000 or less. As for the polymer described in item 1 of the patent application scope, the proportion of components with a molecular weight of less than 6000 is 3.0% or more. The polymer as described in item 1 of the patent application, wherein the proportion of components having a molecular weight of more than 20,000 is 70% or less. A positive-type photoresist composition, comprising: the polymer as described in any one of patent application items 1 to 3; and a solvent.