JP2005316445A - Lift-off positive resist composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lift-off positive resist composition capable of forming a fine lift-off pattern. <P>SOLUTION: The lift-off positive resist composition comprises a base resin component (A) and an acid generator component (B) which generates an acid by exposure, wherein the base resin component (A) is a silicone resin. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a positive resist composition for lift-off.

  In the manufacture of semiconductor elements, liquid crystal display elements, etc., microfabrication techniques based on lithography techniques are used. The three-dimensional microfabrication technology applying the lithography technology is called micromachining, and is a sophisticated small system in which various elements such as sensors, circuits, and fine structures are integrated on a substrate, so-called MEMS, MRAM, etc. Used for manufacturing.

One application of such lithography technology is a lift-off method. The lift-off method is used, for example, for manufacturing a fine structure in a lead portion (reading head portion) of a magnetic head of a magnetic recording medium (see, for example, Patent Document 1).
FIG. 1A to FIG. 1E are schematic views (side cross-sectional views) of each process of forming a general magnetic head.
First, as shown in FIG. 1A, a magnetic film 2 ′ is laminated on a substrate 1, and a base film 3 ′ soluble in an alkali developer and a resist film 4 ′ are sequentially formed thereon. Laminate.
Next, selective exposure is performed from above the resist film 4 ′ through a mask pattern using a KrF excimer laser or the like. Next, when alkali development is performed, a predetermined range of the resist film 4 ′ (exposed portion if positive, unexposed portion if negative) is dissolved and removed, and a resist pattern 4 is obtained. At this time, the base film 3 ′ located under the etched portion of the resist film 4 ′ is also removed together with the alkaline developer to form the base pattern 3. The base film 3 ′ is usually formed of a resist. The alkali solubility is higher than that of the film 4 ′, and the width W ¹ of the base pattern 3 is narrower than the width W ² of the resist pattern 4. Due to this difference in dissolution rate, as shown in FIG. 1 (b), a lift-off pattern 5 having a cross-sectional wing plate shape, which is composed of a base pattern 3 having a narrow width and a resist pattern 4 having a wider width than that, is obtained.
Next, when ionic etching is performed using the lift-off pattern 5 as a mask, the magnetic film 2 ′ around the lift-off pattern 5 is etched as shown in FIG. Then, the magnetic film pattern 2 is formed. As the ionic etching, ion milling is frequently used.
Further, when sputtering is performed, an electrode film 6 is formed on the lift-off pattern 5 and the substrate 1 around the magnetic film pattern 2 as shown in FIG.
Finally, the lift-off pattern 5 is removed (lifted off) by dissolving the ground pattern 3 using an alkali developer or the like and removing the resist pattern 4. By such lift-off of the lift-off pattern 5, as shown in FIG. 1E, the substrate 1, the magnetic film pattern 2 having a predetermined width formed thereon, and the electrode film 6 formed around the substrate 1 are formed. Thus, the magnetic head 10 is obtained.
JP 2002-110536 A

  Currently, the demand for miniaturization is increasing. For example, in order to improve the recording density of a magnetic recording medium, it is required to achieve miniaturization of the magnetic head as described above, and in order to miniaturize the magnetic head, a fine resist pattern (isolated pattern) is required. It is necessary to form and thereby form a fine magnetic film pattern.

However, the positive resist composition used in the past has a problem that sufficient fine processing cannot be performed and a fine lift-off pattern cannot be formed.
For example, it is conceivable to reduce the thickness of the resist film as one of the fine processing techniques, but the positive resist composition used in the past does not have sufficient resistance to ionic etching such as ion milling, and the resist film is not suitable. There is a problem that the etching of the substrate and the magnetic film cannot be performed sufficiently because the film is reduced or the rectangularity of the resist pattern is deteriorated.
Further, it is difficult to control the size of the width W ¹ (see FIG. 1B) of the base pattern 3 when forming the lift-off pattern, and the base pattern 3 becomes too thin during overetching, resulting in pattern collapse. There are problems such as.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a lift-off positive resist composition capable of forming a fine lift-off pattern.

As a result of intensive studies, the present inventors have found that the above problems can be solved by a positive resist composition containing a silicone resin as a base resin, and have completed the present invention.
That is, the present invention provides a positive resist composition for lift-off comprising a base resin component (A) and an acid generator component (B) that generates an acid upon exposure, wherein the base resin component (A) is a silicone resin. There is a positive resist composition for lift-off.

  In the present invention, “structural unit” means a monomer unit constituting a polymer. The exposure also includes electron beam irradiation.

  With the lift-off positive resist composition of the present invention, a fine lift-off pattern can be formed.

Hereinafter, the present invention will be described in more detail.
The positive resist composition for lift-off of the present invention comprises a base resin component (A) (hereinafter sometimes referred to as (A) component) and an acid generator component (B) that generates acid upon exposure (hereinafter referred to as (B). ))).
In such a positive resist composition, when the acid generated from the component (B) acts, the entire positive resist composition changes from alkali-insoluble to alkali-soluble. Therefore, in the formation of the resist pattern, when the positive resist composition applied on the substrate is selectively exposed through the mask pattern, the alkali solubility of the exposed portion increases and alkali development can be performed.

The positive resist composition of the present invention is for lift-off. For example, as described in the section <Method for forming lift-off pattern and patterning method> described later, a magnetic resist provided on the substrate or on the substrate. A resist film is provided on the film via a base film, and the resist film is selectively exposed, and then subjected to alkali development to form a resist pattern. Using the resist pattern as a mask, dry etching such as oxygen plasma etching is performed. Suitable for a method for forming a lift-off pattern having a cross-sectional structure of a wing plate having a base pattern and a resist pattern wider than the base pattern by over-etching the base film to form a base pattern. Used for.
The lift-off pattern formed in this way is, for example, formed by performing ion etching such as ion milling using the lift-off pattern as a mask to form a pattern on a substrate or a magnetic film, and then optionally forming a thin film by sputtering or the like. And a patterning method for removing the lift-off pattern (lift-off).

<(A) component>
The positive resist composition of the present invention is characterized in that the component (A) is a silicone resin.
The silicone resin is a resin having an organic group such as an alkyl group or an aryl group among polysiloxanes having a repeating structure of siloxane bonds in which silicon atoms and oxygen atoms are bonded.
As the silicone resin, a silicone resin generally proposed as a base resin for a positive resist composition can be used. For example, 3/2 oxygen atoms and one organic resin per one silicon atom. Examples thereof include silsesquioxane resin having a structural unit having a group bonded thereto.

  In the present invention, since the component (A) is a silicone resin, a fine lift-off pattern can be formed. That is, conventionally, when a resist film is provided on an alkali-soluble organic film (underlying film) and a pattern for lift-off is formed by performing over-etching after exposure, by alkali development, simultaneously with development of the resist film, The base film is excessively dissolved in alkali to form a lift-off pattern. However, in such a method, it is difficult to finely control the size of the resist pattern and the base pattern during development. On the other hand, in the present invention, by using a resist composition containing a silicone resin, resistance to dry etching of the resist film is increased, and at the same time, dry etching that allows easy dimension control by overetching of the base film can be used. As a result, it is considered that a fine lift-off pattern can be formed. Note that the conventional resist film has low resistance to dry etching such as oxygen etching, so that dry etching cannot be used.

In the present invention, the content ratio (silicon content) of the silicon atom derived from the component (A) to the total solid content of the positive resist composition (silicon content) in the component (A) is 5 to 30% by mass. Preferably, it is 8-20 mass%. By being above the lower limit value, the resistance to dry etching such as oxygen plasma etching is sufficient to form a fine lift-off pattern. Moreover, when it is below the upper limit, the quantitative balance with other components is good, and therefore the balance of various properties is also good.
The silicon content can be adjusted by adjusting the silicon content of the silicone resin used for the component (A) and / or the blending amount of the component (A) in the positive resist composition.

In the present invention, examples of the component (A) include an acid dissociable, dissolution inhibiting group, a resin component (A1) that has an acid dissociation-dissolving group that is dissociated by the action of an acid to increase alkali solubility, and an alkali-soluble component. Resin component (A2).
When the component (A) is the resin component (A1), the acid dissociable, dissolution inhibiting group contained in the resin component (A1) is dissociated by the acid generated from the component (B), thereby exposing the resin component (A1). The alkali solubility of the part increases.
When the component (A) is the resin component (A2), the positive resist composition of the present invention has an acid dissociable, dissolution inhibiting group, which will be described later, and the acid dissociable, dissolution inhibiting group by the action of an acid. Contains a low molecular weight dissolution inhibitor (C) that dissociates. That is, the acid generated from the component (B) dissociates the acid dissociable dissolution inhibiting group contained in the low molecular weight dissolution inhibitor (C), thereby increasing the alkali solubility in the exposed area.

The following silsesquioxane resin (A11) and silsesquioxane resin (A12) are preferable as the resin component (A1).
Moreover, as a suitable thing as a resin component (A2), the following silsesquioxane resin (A21) is mentioned.

(Silsesquioxane resin (A11))
The silsesquioxane resin (A11) has the following general formula (I)

（式中、Ｒ^１は炭素数１〜５の直鎖状または分岐状のアルキレン基を表す。）
で表される構成単位（ａ１）と、下記一般式（ＩＩ）

(In the formula, R ¹ represents a linear or branched alkylene group having 1 to 5 carbon atoms.)
A structural unit (a1) represented by the following general formula (II)

（式中、Ｒ^２は炭素数１〜５の直鎖状または分岐状のアルキレン基を表し、Ｒ^３は酸解離性溶解抑制基を表す。）
で表される構成単位（ａ２）と、下記一般式（ＩＩＩ）

(In the formula, R ² represents a linear or branched alkylene group having 1 to 5 carbon atoms, and R ³ represents an acid dissociable, dissolution inhibiting group.)
A structural unit (a2) represented by the following general formula (III)

で表される構成単位（ａ３）とを有する。

And a structural unit (a3) represented by

In the structural unit (a1), R ¹ is preferably a lower alkylene group having 1 to 5 carbon atoms, and more preferably a methylene group, from the viewpoint of resin synthesis. The position of the hydroxyl group may be o-position, m-position or p-position, but p-position is industrially preferable.

In the structural unit (a2), R ² is preferably a lower alkylene group having 1 to 5 carbon atoms, and more preferably a methylene group, from the viewpoint of resin synthesis.

R ³ in the structural unit (a2) is an acid dissociable, dissolution inhibiting group.
In the present invention, the “acid dissociable, dissolution inhibiting group” means an alkali dissolution inhibiting property that makes the entire positive resist composition insoluble in an alkali before exposure in the process of resist pattern formation using the positive resist composition. In addition, after exposure, it is a group that dissociates by the action of an acid generated from the component (B) described later, and changes the entire positive resist composition to alkali-soluble.
Accordingly, when a resist composition containing the silsesquioxane resin (A11) is applied onto a substrate and exposed through a mask pattern, the alkali solubility of the exposed portion increases, and alkali development is performed to form a resist pattern. be able to.

R ³ may be any acid dissociable, dissolution inhibiting group capable of substituting for a hydrogen atom of a phenolic hydroxyl group, and can be appropriately selected from those proposed in accordance with the light source used. Specific examples include tertiary alkyloxycarbonyl groups such as tert-butoxycarbonyl group and tert-amyloxycarbonyl group; tertiary alkyl groups such as tert-butyl group and tert-amyl group; tert-butoxycarbonylmethyl group. Tertiary alkoxycarbonylalkyl groups such as tert-butoxycarbonylethyl group; 1-ethoxyethyl group, 1-isopropoxyethyl group, 1-methoxy-1-methylethyl group, 1-methoxypropyl group, 1- Examples thereof include alkoxyalkyl groups such as n-butoxyethyl group; cyclic ether groups such as tetrahydropyranyl group and tetrahydrofuranyl group.
Among these, an alkoxyalkyl group is particularly preferable from the viewpoint that the lithography characteristics can be improved because the elimination energy is low and a dissolution contrast can be easily obtained. In the alkoxyalkyl group, the alkoxy group preferably has 1 to 3 carbon atoms, and the alkyl group preferably has 1 to 6 carbon atoms. As the alkoxyalkyl group, a 1-ethoxyethyl group is particularly preferable.
The position of —OR ³ may be any of the o-position, m-position, and p-position, but the p-position is industrially preferable.

The silsesquioxane resin (A11) may contain a structural unit (a4) that does not impair the effects of the present invention, in addition to the structural units (a1) to (a3).
Specific examples of such a structural unit (a4) include structural units represented by the following general formula (VI).

（式中、Ｒ^４は炭素数１〜１５の直鎖状、分岐状、または環状のアルキル基を示す。）

(Wherein R ⁴ represents a linear, branched, or cyclic alkyl group having 1 to 15 carbon atoms.)

The proportion of each structural unit in the resin is such that the total content of the structural unit (a1) and the structural unit (a2) is 50 mol% or more with respect to the total of all the structural units of the silsesquioxane resin (A11). It is preferable that If the total of the structural unit (a1) and the structural unit (a2) is less than 50 mol%, the solubility in the alkali development step may be insufficient.
On the other hand, the structural unit (a3) is a structural unit that contributes to the improvement of heat resistance. When the content of the structural unit (a3) in the silsesquioxane resin (A11) is less than 10%, a sufficient heat resistance improvement effect is achieved. Therefore, the total of the structural unit (a1) and the structural unit (a2) is preferably 90 mol% or less.
Therefore, the total of the structural unit (a1) and the structural unit (a2) is preferably 50 to 90 mol%, more preferably 60 to 80 mol%. Moreover, a structural unit (a3) is 10-50 mol%, Preferably it is 20-40 mol%.

And it is preferable that the content rate of a structural unit (a2) is 8 mol% or more with respect to the sum total of a structural unit (a1) and a structural unit (a2).
The smaller the content ratio of the structural unit (a2) with respect to the total of the structural unit (a1) and the structural unit (a2), the lower the dissolution inhibiting effect due to the introduction of the acid dissociable dissolution inhibiting group (R ³ ). Therefore, the difference in alkali solubility before and after exposure of the silsesquioxane resin (A11) is reduced. On the other hand, if the content ratio of the structural unit (a2) is too large, part of the acid dissociable, dissolution inhibiting group may remain without being completely dissociated after the exposure and PEB steps. The acid dissociable, dissolution inhibiting group remaining without being completely dissociated often causes a defect without being removed by rinsing. Moreover, when there are many structural units (a2), there exists a tendency for the heat resistance of (A) component to fall.
Therefore, the content ratio of the structural unit (a2) to the total of the structural unit (a1) and the structural unit (a2) is preferably about 8 to 25 mol%, more preferably about 10 to 20 mol%.

When the shape of the resist pattern to be obtained is a line and space pattern, the line edge roughness increases as the content ratio of the structural unit (a3) in the silsesquioxane resin (A11) increases, and is suitable for fine processing. It will be. In this case, the content ratio of the structural unit (a3) is preferably 25 to 50 mol%, more preferably 30 to 40 mol%. The line edge roughness is uneven unevenness of the line side wall. 3σ, which is a scale indicating the line edge roughness of the line-and-space pattern, was obtained by measuring the width of the resist pattern of the sample at 32 locations using a side length SEM (manufactured by Hitachi, Ltd., trade name “S-9220”). It is a triple value (3σ) of the calculated standard deviation (σ). This 3σ means that the smaller the value, the smaller the roughness and the uniform width resist pattern was obtained.
Further, when the shape of the resist pattern to be obtained is a hole pattern, if the content ratio of the structural unit (a3) in the silsesquioxane resin (A11) is large, the edge roughness of the hole pattern is improved, but the resolution is improved. Since there exists a tendency for property to fall, the content rate of the said structural unit (a3) has preferable 25-35 mol%, More preferably, it is 25-30 mol%.

  Moreover, when making the said silsesquioxane resin (A11) contain the said other structural unit (a4), it is preferable that the content rate shall be 25 mol% or less, More preferably, it is 15 mol% or less.

  In the silsesquioxane resin (A11), the remainder other than the structural unit (a1) and the structural unit (a2), that is, 50 mol% or less is the structural unit (a3) or the structural unit (a3) and the structural unit ( A total of a4) is preferred. That is, it is preferable that the silsesquioxane resin (A11) is composed of only the structural units (a1) to (a3) or only the structural units (a1) to (a4).

The mass average molecular weight (Mw) of the silsesquioxane resin (A11) (polystyrene conversion by gel permeation chromatography (hereinafter sometimes abbreviated as GPC), the same shall apply hereinafter) is not particularly limited. , Preferably 2000 to 15000, more preferably 5000 to 10000. If it is larger than this range, the solubility in an organic solvent is deteriorated, and if it is smaller, the resist pattern cross-sectional shape may be deteriorated.
Moreover, although Mw / number average molecular weight (Mn) is not specifically limited, Preferably it is 1.0-6.0, More preferably, it is 1.0-2.0. If it is larger than this range, the resolution and pattern shape may deteriorate.

  The silsesquioxane resin (A11) in the present invention is a polymer composed of the structural unit (a1) and the structural unit (a3), for example, using the method described in Japanese Patent No. 2567984 as shown in the following synthesis example, or A polymer comprising the structural unit (a1), the structural unit (a3), and the structural unit (a4) is obtained, and then the hydrogen atom of the phenolic hydroxyl group in a part of the side chain of the structural unit (a1) is acid dissociated by a well-known method. It can be produced by forming a structural unit (a2) by substituting with a soluble dissolution inhibiting group. Note that as the structural unit (a4), alkyltrialkoxysilane or alkyltrichlorosilane can be used as the monomer.

In the step of introducing an acid dissociable, dissolution inhibiting group, the above polymer is dissolved in an organic solvent, and a base or an acidic catalyst, and a compound corresponding to the acid dissociable, dissolution inhibiting group to be introduced are added thereto, and 20-70 After reacting at a temperature of about 1 ° C. for about 1 to 10 hours, the reaction solution is neutralized by adding an acid or base, and then stirred into water to precipitate a polymer, whereby the structural unit (a1 ), A structural unit (a2) and a structural unit (a3), or a polymer composed of the structural unit (a1), the structural unit (a2), the structural unit (a3) and the structural unit (a4). In addition, a base or an acidic catalyst may be properly used depending on the compound corresponding to the acid dissociable, dissolution inhibiting group.
The content ratio of the structural unit (a1) and the structural unit (a2) can be controlled by the amount of the compound corresponding to the acid dissociable, dissolution inhibiting group to be introduced.

(Silsesquioxane resin (A12))
The silsesquioxane resin (A12) includes the structural unit (a1) represented by the general formula (I) and the following general formula (V).

（式中、Ｒ^５は炭素数１〜５の直鎖状または分岐状のアルキレン基を表し、Ｒ^６は炭素数１〜５のアルキル基を表し、Ｒ^７は炭素数１〜５のアルキル基または水素原子を表し、Ｒ^８は炭素数５〜１５の脂環式炭化水素基を表す。）
で表される構成単位（ａ５）とを有する。

(In the formula, R ⁵ represents a linear or branched alkylene group having 1 to 5 carbon atoms, R ⁶ represents an alkyl group having 1 to 5 carbon atoms, and R ⁷ represents an alkyl group having 1 to 5 carbon atoms. Alternatively, it represents a hydrogen atom, and R ⁸ represents an alicyclic hydrocarbon group having 5 to 15 carbon atoms.
And a structural unit (a5) represented by

In the silsesquioxane resin (A12), from a point on the resin synthesis as R ¹ in the structural unit (a1), R ¹ is a linear or branched alkylene group having 1 to 5 carbon atoms, more A linear or branched alkylene group having 1 to 3 carbon atoms is more preferable. The position of the hydroxyl group may be any of o-position, m-position and p-position, but p-position is industrially preferable.

In the structural unit (a5), R ⁵ is a linear or branched alkylene group having 1 to 5 carbon atoms from the viewpoint of resin synthesis similarly to R ¹ , and further having 1 to 3 carbon atoms. A linear or branched alkylene group is more preferable.
R ⁶ is a linear or branched alkyl group having 1 to 5 carbon atoms, preferably a methyl group or an ethyl group.
R ⁷ is a linear or branched alkyl group having 1 to 5 carbon atoms or a hydrogen atom, preferably a hydrogen atom.
R ⁸ is an alicyclic hydrocarbon group having 5 to 15 carbon atoms, preferably a cycloalkyl group having 5 to 7 carbon atoms such as a cyclopentyl group or a cyclohexyl group, and industrially, a cyclohexyl group is most preferable because of its low cost. .

The functional group represented by the following general formula (VI) in the structural unit (a5) acts as an acid dissociable, dissolution inhibiting group.
Therefore, when a resist composition containing this silsesquioxane resin (A12) is applied onto a substrate and exposed through a mask pattern, the alkali solubility of the exposed portion increases, and alkali development develops to form a resist pattern. be able to.

  The position of the acid dissociable, dissolution inhibiting group represented by the general formula (VI) may be any of the o-position, m-position and p-position, but the p-position is industrially preferred.

  The proportion of each structural unit in the resin is such that the total content of the structural unit (a1) and the structural unit (a5) is 50 mol% or more with respect to the total of all the structural units of the silsesquioxane resin (A12). Preferably, it may be 100 mol%. If the total of the structural unit (a1) and the structural unit (a5) is less than 50 mol%, the solubility in the alkali development step may be insufficient. The total of the structural unit (a1) and the structural unit (a5) is preferably 50 to 90 mol%, more preferably 60 to 80 mol%.

  The content ratio of the structural unit (a5) is preferably 5 to 50 mol%, more preferably 5 to 15 mol%, based on the total of the structural unit (a1) and the structural unit (a5). is there. Since the dissolution inhibiting effect by the acid dissociable, dissolution inhibiting group decreases as the content of the structural unit (a5) decreases with respect to the sum of the structural unit (a1) and the structural unit (a5), the silsesquioxane resin The difference in alkali solubility before and after the exposure of (A12) becomes small. On the other hand, if the content ratio of the structural unit (a5) is too large, a part of the acid dissociable, dissolution inhibiting group may remain without being completely dissociated after exposure and PEB steps. The acid dissociable, dissolution inhibiting group remaining without being completely dissociated often causes a defect without being removed by rinsing. In the case of a hole pattern in particular, defects are likely to occur. Moreover, when there are many structural units (a5), there exists a tendency for the heat resistance of (A) component to fall.

The silsesquioxane resin (A12) may further contain the structural unit (a3) represented by the general formula (III).
The structural unit (a3) is not essential, but when the silsesquioxane resin (A12) contains the structural unit (a3), the heat resistance of the resist pattern is improved.
Moreover, when the shape of the resist pattern to be obtained is a line and space pattern, the line edge roughness is effectively improved by incorporating the structural unit (a3) into the silsesquioxane resin (A12). In this case, the content ratio of the structural unit (a3) in the silsesquioxane resin (A12) is preferably 20 to 50 mol%, more preferably 30 to 40 mol%.

Further, the silsesquioxane resin (A12) may contain the above-described structural unit (a4) that does not impair the effects of the present invention in addition to the structural units (a1), (a5), and (a3). Good.
When the other structural unit (a4) is contained in the silsesquioxane resin (A12), the content is preferably 20 mol% or less, more preferably 15 mol% or less.

  In the silsesquioxane resin (A12), the remainder other than the structural unit (a1) and the structural unit (a5), that is, 50 mol% or less is the structural unit (a3) or the structural unit (a3) and the structural unit ( A total of a4) is preferred. That is, the silsesquioxane resin (A2) may consist of only the structural units (a1), (a5) and (a3), or only the structural units (a1), (a5), (a3) and (a4). preferable.

Although the mass average molecular weight (Mw) of silsesquioxane resin (A12) is not specifically limited, Preferably it is 2000-15000, More preferably, it is 5000-10000. If it is larger than this range, the solubility in an organic solvent is deteriorated, and if it is smaller, the resist pattern cross-sectional shape may be deteriorated.
Mw / Mn is not particularly limited, but is preferably 1.0 to 6.0, more preferably 1.0 to 2.0. If it is larger than this range, the resolution and pattern shape may deteriorate.

When the silsesquioxane resin (A12) in the present invention is composed of the structural unit (a1) and the structural unit (a5), the production method first obtains a polymer composed of the structural unit (a1) by a well-known polymerization method. Then, it can be produced by forming the structural unit (a5) by introducing an acid dissociable, dissolution inhibiting group into the phenolic hydroxyl group of a part of the side chain of the structural unit (a1) by a known method.
A silsesquioxane resin composed of the structural unit (a1), the structural unit (a5), and the structural unit (a3) can be produced by using a method described in Japanese Patent No. 2567984, for example, as shown in a synthesis example described later. By obtaining a polymer comprising the unit (a1) and the structural unit (a3), and then introducing an acid dissociable, dissolution inhibiting group into the phenolic hydroxyl group of a part of the side chain of the structural unit (a1) by a well-known method Can be manufactured.
The silsesquioxane resin comprising the structural unit (a1), the structural unit (a5), the structural unit (a3), and the structural unit (a4) is, for example, the structural unit (a1), the structural unit (a3), and the structural unit ( It can be produced by obtaining a polymer comprising a4) and then introducing an acid dissociable, dissolution inhibiting group into the phenolic hydroxyl group of a part of the side chain of the structural unit (a1) by a known method. As the structural unit (a4), alkyltrialkoxysilane or alkyltrichlorosilane can be used as the monomer.

The step of introducing the acid dissociable, dissolution inhibiting group includes a polymer comprising the structural unit (a1), a polymer comprising the structural unit (a1) and the structural unit (a3), or a structural unit (a1) and the structural unit (a3). A polymer composed of the unit (a4) is dissolved in an organic solvent, a base or an acidic catalyst, and a compound corresponding to the acid dissociable, dissolution inhibiting group to be introduced are added thereto, and the temperature is about 20 to 70 ° C. After performing the reaction for about 10 hours, the reaction solution is neutralized by adding an acid or a base, and then stirred into water to precipitate a polymer, whereby the polymer having the above respective structural units is converted into a structural unit. A polymer to which (a5) has been added is obtained. In addition, a base or an acidic catalyst may be properly used depending on the compound corresponding to the acid dissociable, dissolution inhibiting group.
The content ratio of the structural unit (a5) can be controlled by the amount of the compound corresponding to the acid dissociable, dissolution inhibiting group to be introduced.

(Silsesquioxane resin (A21))
The silsesquioxane resin (A21) includes the structural unit (a1) represented by the general formula (I) and the following general formula (VII).

（式中、Ｒ^９は炭素数１〜５の直鎖状または分岐状のアルキレン基を表し、Ｒ^１０は炭素数１〜５の直鎖状または分岐状のアルキル基を表す。）
で表される構成単位（ａ７）と、前記一般式（ＩＩＩ）で表される構成単位（ａ３）とを有する。

(In the formula, R ⁹ represents a linear or branched alkylene group having 1 to 5 carbon atoms, and R ¹⁰ represents a linear or branched alkyl group having 1 to 5 carbon atoms.)
And the structural unit (a3) represented by the general formula (III).

In the general formula (VII), R ⁹ is a linear or branched alkylene group having 1 to 5 carbon atoms from the viewpoint of resin synthesis as in R ¹ , and further has 1 to 3 carbon atoms. The linear or branched alkylene group is more preferable.
R ¹⁰ is most preferably a methyl group.
In addition, the bonding position of —OR ¹⁰ in the general formula (VII) may be any of o-position, m-position and p-position, but industrially preferred is p-position.

  The content ratio of these structural units is 10 to 70 mol%, preferably 20 to 55 mol%, 5 to 50 mol%, preferably 10 to 40 mol%, and 10 to 40 mol% of the structural unit (a7). a3) It is preferably selected within the range of 10 to 60 mol%, preferably 20 to 40 mol%.

  The structural unit (a7) in this has the effect | action which adjusts the solubility with respect to an alkali, suppresses film reduction, and prevents the roundness which arises in a resist pattern cross section. Since this structural unit (a7) is the same as the starting material of the structural unit (a1), it can be advantageously introduced by suppressing the dissociation degree of the alkoxy group.

Further, the silsesquioxane resin (A21) may contain the above-described structural unit (a4) that does not impair the effects of the present invention in addition to the structural units (a1), (a7), and (a3). Good.
When the silsesquioxane resin (A21) contains the other structural unit (a4), the content is preferably 20 mol% or less, more preferably 15 mol% or less.

In the positive resist composition of the present invention, the constitutional unit (a7) in the silsesquioxane resin (A21) is increased or decreased, and the dissolution rate of the silsesquioxane resin (A21) in the alkali is 0.05 to 50 nm. / Sec, preferably 5.0 to 30 nm / sec.
Here, the dissolution rate of the silsesquioxane resin (A21) with respect to alkali is preferably a dissolution rate with respect to an aqueous solution of 2.38% by mass of TMAH (tetramethylammonium hydroxide).
By having a dissolution rate of 50 nm / sec or less, film loss is sufficiently suppressed, and roundness occurring in the resist pattern cross section can be prevented. In addition, effects such as improved resolution and reduced defect can be obtained. Moreover, by setting it as 0.05 nm / sec or more, it can melt | dissolve in an organic solvent and can be set as a resist.
The dissolution rate can be adjusted, for example, by changing the proportion of the structural unit (a7). For example, the dissolution rate can be reduced by increasing the proportion of the structural unit (a7).

Specifically, the value of the dissolution rate with respect to alkali is a value obtained as follows.
First, a solution in which a silsesquioxane resin (A21) is dissolved in an organic solvent is applied onto a silicon wafer, and the organic solvent is volatilized by heating [pre-baking (PAB)] by a heat treatment, thereby forming a resin coating (thickness 500). ˜1300 nm, for example, a thickness of 1000 nm). The organic solvent is appropriately selected from known ones used for chemically amplified positive photoresist compositions as described later. Further, the concentration of the silsesquioxane resin (A21) can be the same as the concentration of the base resin in the resist composition, but is, for example, 10 to 25% by mass, for example 20% by mass. Next, after measuring the film thickness of the resin film, the wafer is immersed in a 2.38 mass% TMAH aqueous solution at 23 ° C. Then, the time for the resin film to completely dissolve is measured, and from this, the amount of reduction in the thickness of the resin film per unit time (nm / second) is obtained.
The amount of reduction of the resin film thus obtained is the dissolution rate of the silsesquioxane resin (A21).

Although the mass average molecular weight (Mw) of silsesquioxane resin (A21) is not specifically limited, What is in the range of 1500-20000 is preferable. If it is larger than this range, the solubility in an organic solvent is deteriorated, and if it is smaller, the resist pattern cross-sectional shape may be deteriorated.
Mw / Mn is not particularly limited, but is preferably 1.0 to 6.0, more preferably 1.0 to 2.0. If it is larger than this range, the resolution and pattern shape may deteriorate.

<(B) component>
In the present invention, the component (B) can be used without particular limitation from known acid generators used in conventional chemically amplified resist compositions. Examples of such acid generators include onium salt acid generators such as iodonium salts and sulfonium salts, oxime sulfonate acid generators, bisalkyl or bisarylsulfonyldiazomethanes, poly (bissulfonyl) diazomethanes, There are various known diazomethane acid generators such as diazomethane nitrobenzyl sulfonates, imino sulfonate acid generators and disulfone acid generators.

  Specific examples of the onium salt-based acid generator include diphenyliodonium trifluoromethanesulfonate or nonafluorobutanesulfonate, bis (4-tert-butylphenyl) iodonium trifluoromethanesulfonate or nonafluorobutanesulfonate, and triphenylsulfonium trifluoromethane. Sulfonate, its heptafluoropropane sulfonate or its nonafluorobutane sulfonate, tri (4-methylphenyl) sulfonium trifluoromethane sulfonate, its heptafluoropropane sulfonate or its nonafluorobutane sulfonate, (4-methylphenyl) diphenylsulfonium trifluoromethane Sulfonate, its heptafluoropropane sulphonate or its Fluorobutanesulfonate, trifluoromethanesulfonate of (4-methoxyphenyl) diphenylsulfonium, its heptafluoropropanesulfonate or its nonafluorobutanesulfonate, trifluoromethanesulfonate of dimethyl (4-hydroxynaphthyl) sulfonium, its heptafluoropropanesulfonate or its nona Fluorobutane sulfonate, trifluorone methane sulfonate of monophenyl dimethyl sulfonium, heptafluoropropane sulfonate or nonafluorobutane sulfonate thereof. Of these, onium salts having a fluorinated alkyl sulfonate ion as an anion are preferable.

  Specific examples of the oxime sulfonate acid generator include α- (methylsulfonyloxyimino) -phenylacetonitrile, α- (methylsulfonyloxyimino) -p-methoxyphenylacetonitrile, α- (trifluoromethylsulfonyloxyimino)- Phenylacetonitrile, α- (trifluoromethylsulfonyloxyimino) -p-methoxyphenylacetonitrile, α- (ethylsulfonyloxyimino) -p-methoxyphenylacetonitrile, α- (propylsulfonyloxyimino) -p-methylphenylacetonitrile, α- (methylsulfonyloxyimino) -p-bromophenylacetonitrile, bis-O- (n-butylsulfonyl) -α-dimethylglyoxime and the like can be mentioned. Among these, α- (methylsulfonyloxyimino) -p-methoxyphenylacetonitrile and bis-O- (n-butylsulfonyl) -α-dimethylglyoxime are preferable.

Among diazomethane acid generators, specific examples of bisalkyl or bisarylsulfonyldiazomethanes include bis (isopropylsulfonyl) diazomethane, bis (p-toluenesulfonyl) diazomethane, bis (1,1-dimethylethylsulfonyl) diazomethane, Examples include bis (cyclohexylsulfonyl) diazomethane, bis (2,4-dimethylphenylsulfonyl) diazomethane, and the like.
Examples of poly (bissulfonyl) diazomethanes include 1,3-bis (phenylsulfonyldiazomethylsulfonyl) propane (Compound A, decomposition point 135 ° C.), 1,4-bis (phenyl) having the following structure. Sulfonyldiazomethylsulfonyl) butane (compound B, decomposition point 147 ° C.), 1,6-bis (phenylsulfonyldiazomethylsulfonyl) hexane (compound C, melting point 132 ° C., decomposition point 145 ° C.), 1,10-bis (phenyl) Sulfonyldiazomethylsulfonyl) decane (compound D, decomposition point 147 ° C.), 1,2-bis (cyclohexylsulfonyldiazomethylsulfonyl) ethane (compound E, decomposition point 149 ° C.), 1,3-bis (cyclohexylsulfonyldiazomethylsulfonyl) ) Propane (Compound F, decomposition point 153 ° C.), , 6-bis (cyclohexylsulfonyldiazomethylsulfonyl) hexane (Compound G, melting point 109 ° C., decomposition point 122 ° C.), 1,10-bis (cyclohexylsulfonyldiazomethylsulfonyl) decane (Compound H, decomposition point 116 ° C.), etc. Can be mentioned.

  As the component (B), one type of acid generator may be used alone, or two or more types may be used in combination.

  In the present invention, among these, onium salt acid generators and / or diazomethane acid generators are preferable. Further, it is preferable to use an onium salt acid generator in combination with 10 to 80% by mass of a diazomethane acid generator based on its mass because line edge roughness at the contact hole is reduced.

In the present invention, the component (B) is an onium salt-based acid generator (hereinafter abbreviated as C3-4 onium salt) having a C3 or C4 perfluoroalkylsulfonate as an anion. When contained, the mask linearity is improved, and patterns having various sizes can be faithfully reproduced on the mask, which is preferable. Further, the proximity effect, DOF, exposure margin and the like are also excellent. The alkyl group of perfluoroalkyl sulfonate may be linear or branched, but is preferably linear.
(B) When mix | blending C3-4 onium salt as a component, the compounding quantity of C3-4 onium salt in (B) component has preferable 50-100 mass%.
Further, when a C3-4 onium salt is blended as the component (B), an onium salt acid generator (hereinafter referred to as C1 onium salt) having a perfluoroalkyl sulfonate having 1 carbon as an anion may be used. ) Is preferably used in combination.

  (B) Content of a component is 0.5-30 mass parts with respect to 100 mass parts of (A) component, Preferably it is 1-10 mass parts. If the amount is less than the above range, pattern formation may not be sufficiently performed, and if the amount exceeds the above range, a uniform solution is difficult to obtain, which may cause a decrease in storage stability.

<(C) component>
In addition to the above essential components (A) and (B), the positive resist composition of the present invention has an acid dissociable, dissolution inhibiting group, if necessary, and the acid dissociable, soluble by the action of an acid. A low molecular weight dissolution inhibitor (C) (hereinafter referred to as the component (C)) in which the inhibitory group is dissociated can be blended. In particular, when the component (A) includes an alkali-soluble resin component (A2) such as a silsesquioxane resin (A21), it is necessary to blend the component (C). By including the component (C), the rectangularity and resolution of the resist pattern, the edge roughness, and the like can be improved.
(C) As molecular weight of a component, 3000 or less are preferable and 500-2000 are more preferable.

  As the component (C), a known dissolution inhibitor already used in a chemically amplified positive resist composition can be used. For example, phenol having a phenolic hydroxyl group protected with an acid dissociable dissolution inhibiting group Examples thereof include a compound or a carboxy compound in which a carboxy group is protected with an acid dissociable, dissolution inhibiting group. Here, “protected” means that at least one of the phenolic hydroxyl group or the hydroxyl group of the carboxy group is substituted with an acid dissociable, dissolution inhibiting group.

  The phenol compound having a phenolic hydroxyl group that can constitute the component (C) by being protected with an acid dissociable, dissolution inhibiting group is a polyphenol compound having 3 to 5 phenol groups, for example, a hydroxyl group as a nuclear substituent. And triphenylmethane compounds, bis (phenylmethyl) diphenylmethane compounds, 1,1-diphenyl-2-biphenylethane compounds, and the like. In addition, 2-6 nuclei obtained by formalin condensation of at least one phenol selected from phenol, m-cresol, and 2,5-xylenol can also be used.

In addition, examples of the carboxy compound having a carboxy group that can constitute the component (C) by being protected with an acid dissociable, dissolution inhibiting group include biphenyl carboxylic acid, naphthalene (di) carboxylic acid, benzoyl benzoic acid, and anthracene. Examples thereof include carboxylic acid.
Examples of acid dissociable, dissolution inhibiting groups for protecting hydroxyl groups or carboxy groups in these phenol compounds or carboxyl compounds include tertiary butyloxy groups such as tertiary butyloxycarbonyl groups and tertiary amyloxycarbonyl groups. Tertiary alkyl groups such as carbonyl groups, tertiary butyl groups and tertiary amyl groups, tertiary alkoxycarbonylalkyl groups such as tertiary butyloxycarbonylmethyl groups and tertiary amyloxycarbonylmethyl groups, and tetrahydropyranyl And a cyclic ether group such as a tetrahydrofuranyl group.
And a compound suitable as these (C) components protects the tetranuclear obtained by condensing 2,5-xylenol and a formalin condensate with the tertiary alkoxycarbonylalkyl group.

These components (C) may be used alone or in combination of two or more.
The content of the component (C) in the positive resist composition of the present invention is preferably 0.5 to 40% by mass and more preferably 10 to 30% by mass with respect to the component (A). If the content is less than 0.5% by mass, a sufficient dissolution inhibiting effect cannot be obtained, and if it exceeds 40% by mass, the pattern shape may be deteriorated or the lithography properties may be deteriorated.

<(D) component>
In the positive resist composition of the present invention, a nitrogen-containing organic compound (D) (hereinafter referred to as “component (D)”) is further added as an optional component in order to improve the resist pattern shape, stability over time and the like. Can be blended.
Since a wide variety of components (D) have already been proposed, any known one may be used, but amines, particularly secondary lower aliphatic amines and tertiary lower aliphatic amines are preferred. .
Here, the lower aliphatic amine refers to an alkyl or alkyl alcohol amine having 5 or less carbon atoms, and examples of the secondary and tertiary amines include trimethylamine, diethylamine, triethylamine, di-n-propylamine, Tri-n-propylamine, tripentylamine, diethanolamine, triethanolamine and the like can be mentioned, and tertiary alkanolamines such as triethanolamine are particularly preferable.
These may be used alone or in combination of two or more.
(D) component is normally used in 0.01-5.0 mass parts with respect to 100 mass parts of (A) component.

<(E) component>
Further, for the purpose of preventing the deterioration of sensitivity due to the blending with the component (D) and improving the resist pattern shape, the stability over time, and the like, an organic carboxylic acid or phosphorus oxo acid or a derivative thereof is further included as an optional component. (E) (hereinafter referred to as component (E)) can be contained. In addition, (D) component and (E) component can also be used together, and any 1 type can also be used.
As the organic carboxylic acid, for example, malonic acid, citric acid, malic acid, succinic acid, benzoic acid, salicylic acid and the like are suitable.
Phosphorus oxoacids or derivatives thereof include phosphoric acid, phosphoric acid di-n-butyl ester, phosphoric acid diphenyl ester and other phosphoric acid or derivatives thereof such as phosphonic acid, phosphonic acid dimethyl ester, phosphonic acid- Like phosphonic acids such as di-n-butyl ester, phenylphosphonic acid, phosphonic acid diphenyl ester, phosphonic acid dibenzyl ester and derivatives thereof, phosphinic acids such as phosphinic acid, phenylphosphinic acid and their esters Among these, phosphonic acid is particularly preferable.
(E) A component is used in the ratio of 0.01-5.0 mass parts per 100 mass parts of (A) component.

<Other optional components>
The positive resist composition of the present invention further contains miscible additives as desired, for example, additional resins for improving the performance of the resist film, surfactants for improving coating properties, dissolution inhibitors, A plasticizer, a stabilizer, a colorant, an antihalation agent, and the like can be appropriately added and contained.

<Organic solvent>
The positive resist composition of the present invention can be produced by dissolving materials such as the above-described components (A) and (B) in an organic solvent.
Any organic solvent may be used as long as it can dissolve each component to be used to form a uniform solution, and one or two kinds of conventionally known solvents for chemically amplified resists can be used. These can be appropriately selected and used.
For example, γ-butyrolactone; ketones such as acetone, methyl ethyl ketone, cyclohexanone, methyl isoamyl ketone, 2-heptanone; ethylene glycol, ethylene glycol monoacetate, diethylene glycol, diethylene glycol monoacetate, propylene glycol, propylene glycol monoacetate, dipropylene glycol or Polyhydric alcohols and derivatives thereof such as monomethyl ether, monoethyl ether, monopropyl ether, monobutyl ether or monophenyl ether of dipropylene glycol monoacetate; cyclic ethers such as dioxane; methyl lactate, ethyl lactate (EL) , Methyl acetate, ethyl acetate, butyl acetate, methyl pyruvate, ethyl pyruvate, methoxypropio Methyl acid, esters such as ethyl ethoxypropionate can be exemplified.
These organic solvents may be used independently and may be used as 2 or more types of mixed solvents.

In the present invention, a mixed solvent of propylene glycol monomethyl ether (PGME) and a solvent having a boiling point higher than that of PGME is preferably used. As a result, the resist pattern shape such as line edge roughness, line width roughness (non-uniformity in the width of the left and right lines) is improved. In addition, the depth of focus (DOF) at the contact hole is increased.
As the solvent having a higher boiling point than PGME, for example, among the solvents exemplified above, those having a boiling point exceeding 120 ° C. which is the boiling point of PGME, preferably those having a boiling point of 20 ° C. or more higher than PGME, more preferably than PGME Those having a boiling point of 25 ° C. or higher are preferred. The upper limit of the boiling point is not particularly limited, but is preferably about 200 ° C. or lower. Examples of such a solvent include propylene glycol monomethyl ether acetate (boiling point 146 ° C.), EL (boiling point 155 ° C.), γ-butyrolactone (boiling point 204 ° C.) and the like. Among these, EL is preferable.
10-60 mass% is preferable in all the mixed solvents, and, as for the compounding quantity of PGME in a mixed solvent, 20-40 mass% is more preferable. Within the above range, the above effect is excellent.

The amount of the organic solvent used is not particularly limited, and is a concentration that can be applied to a substrate and the like, and is appropriately set according to the coating film thickness. Generally, the solid content concentration of the resist composition is 2 to 2. The amount is 20% by mass, preferably 5 to 15% by mass.
When the above-mentioned mixed solvent of PGME and a high-boiling solvent is used as the organic solvent, a solid film can be formed with a small resist solid content, so that the solid content concentration can be reduced and a film having sufficient etching resistance can be obtained.

<Pattern formation method and patterning method for lift-off>
The positive resist composition of the present invention can be suitably used in a method for forming a lift-off pattern, a method for patterning a substrate or a magnetic film provided on the substrate, etc. using the lift-off pattern.
Hereinafter, the lift-off pattern forming method and patterning method using the positive resist composition of the present invention will be described in more detail with reference to FIG. 1 and an embodiment applied to the manufacture of a magnetic head lead. Fig.1 (a)-FIG.1 (e) are the schematic diagrams (side sectional drawing) of each process concerning this embodiment.

"Pattern formation method for lift-off"
[Process of forming magnetic film 2 ']
First, as shown in FIG. 1A, a magnetic film 2 ′ is formed on a substrate 1 such as a silicon wafer by a sputtering apparatus.
The substrate is not particularly limited, and a conventionally known substrate can be used. For example, a substrate for an electronic component can be exemplified. Examples of the material for the substrate include silicon wafers, metals such as copper, chromium, iron, and aluminum, and glass.
As the magnetic material used for the magnetic film 2 ′, a material containing an element such as Ni, Co, Cr, Pt or the like is used.

[Formation process of base film 3 ']
Next, a resist composition or a resin solution for forming a base film is applied to the formed magnetic film 2 ′ by a spinner or the like, preferably at 200 to 300 ° C. for 30 to 300 seconds, preferably 60 to 180. A baking process is performed under heating conditions for 2 seconds to form a base film 3 ′.
The base film is an organic film that is insoluble in an alkali developer used for development after exposure and can be etched by a conventional dry etching method.
By using such a base film 3 ′, as described later, only the resist film 4 ′ is exposed and alkali-developed by ordinary photolithography to form a resist pattern 4, and then the resist pattern 4 is used as a mask. The resist pattern 4 is transferred by dry-etching the base film 3 ′, and the base pattern 3 is formed on the base film 3 ′.
The material for forming the base film 3 ′ does not necessarily require photosensitivity like the resist film 4 ′, and is generally used as a base material in the manufacture of semiconductor elements and liquid crystal display elements. A resist or resin may be used.
Further, since it is necessary to transfer the resist pattern 4 to the base film 3 ′, the base film 3 ′ is preferably a material that can be etched by oxygen plasma.
As such a material, it is easy to perform etching by oxygen plasma, and at the same time, it is used for etching a fluorocarbon gas used for etching a substrate such as silicon or a substrate or a magnetic film in a later process. In view of strong resistance to dry etching such as ionic etching such as ion milling, a material mainly composed of at least one selected from the group consisting of novolak resin, acrylic resin and soluble polyimide is preferably used.
Among these, a novolak resin and an acrylic resin having an alicyclic moiety or an aromatic ring in the side chain are preferably used because they are inexpensive and widely used and have excellent dry etching resistance in the subsequent steps.

As the novolac resin, those generally used in positive resist compositions can be used, and i-line and g-line positive resists containing a novolac resin as a main component can also be used.
The novolak resin can be obtained, for example, by addition condensation of an aromatic compound having a phenolic hydroxyl group (hereinafter simply referred to as “phenols”) and an aldehyde under an acid catalyst.
Examples of phenols include phenol, o-cresol, m-cresol, p-cresol, o-ethylphenol, m-ethylphenol, p-ethylphenol, o-butylphenol, m-butylphenol, p-butylphenol, 2, 3 -Xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4-xylenol, 3,5-xylenol, 2,3,5-trimethylphenol, 3,4,5-trimethylphenol , P-phenylphenol, resorcinol, hydroquinone, hydroquinone monomethyl ether, pyrogallol, phloroglicinol, hydroxydiphenyl, bisphenol A, gallic acid, gallic acid ester, α-naphthol, β-naphthol and the like.
Examples of aldehydes include formaldehyde, furfural, benzaldehyde, nitrobenzaldehyde, and acetaldehyde.
The catalyst for the addition condensation reaction is not particularly limited. For example, hydrochloric acid, nitric acid, sulfuric acid, formic acid, oxalic acid, acetic acid and the like are used as the acid catalyst.
The novolak resin has a mass average molecular weight of 5,000 to 50,000, preferably 6,000 to 9000, and more preferably 7,000 to 8,000.
By setting the Mw of the novolak resin to 50000 or less, excellent embedding characteristics with respect to a substrate having fine irregularities are excellent. Further, it is preferable to set Mw to 5000 or more because etching resistance to a fluorocarbon gas or the like can be obtained.
On the other hand, if the mass average molecular weight is less than 5,000, it may sublime when baked at a high temperature. If the mass average molecular weight exceeds 50,000, dry etching tends to be difficult, which is not preferable.

As the novolak resin, a commercially available product can be used, but the content of low molecular weight components having a molecular weight of 500 or less, preferably 200 or less, is preferably 1 in the gel permeation chromatography method. A novolak resin having a mass% or less, preferably 0.8 mass% or less, is preferred. The content of the low nucleus is preferably as small as possible, and is desirably 0% by mass.
The “low molecular weight having a molecular weight of 500 or less” is detected as a low molecular fraction having a molecular weight of 500 or less when analyzed by GPC using polystyrene as a standard. “Low-nuclear bodies having a molecular weight of 500 or less” include monomers that have not been polymerized and those having a low degree of polymerization, such as those obtained by condensing 2-5 molecules of phenols with aldehydes, depending on the molecular weight. .
The content (mass%) of the low-nuclear body having a molecular weight of 500 or less is graphed with the analysis result by the GPC method taking the fraction number on the horizontal axis and the concentration on the vertical axis, and the molecular weight of 500 or less with respect to the area under the entire curve. It is measured by determining the percentage (%) of the area under the curve of the low molecular fraction.
Regarding the significance and content of “low molecular weight having a molecular weight of 200 or less”, “500” may be replaced with “200” in the meaning and content measurement method of “low molecular weight having a molecular weight of 500 or less”.
When the content of the low-nuclear substance having a molecular weight of 500 or less is 1% by mass or less, the embedding characteristic for a substrate having fine irregularities is improved. Although the reason why the embedding property is improved by reducing the content of the low nuclei is not clear, it is presumed that the degree of dispersion becomes small.

As the acrylic resin, those generally used in positive resist compositions can be used. For example, a structural unit derived from a polymerizable compound having an ether bond and a polymerizable compound having a carboxy group can be used. Mention may be made of acrylic resins containing derived structural units.
Examples of the polymerizable compound having an ether bond include 2-methoxyethyl (meth) acrylate, methoxytriethylene glycol (meth) acrylate, 3-methoxybutyl (meth) acrylate, ethyl carbitol (meth) acrylate, phenoxy polyethylene glycol (meta And (meth) acrylic acid derivatives having an ether bond and an ester bond such as acrylate, methoxypolypropylene glycol (meth) acrylate, and tetrahydrofurfuryl (meth) acrylate. These compounds can be used alone or in combination of two or more.
Examples of the polymerizable compound having a carboxy group include monocarboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid; dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid; 2-methacryloyloxyethyl succinic acid, and 2-methacryloyloxyethyl. Examples include maleic acid, 2-methacryloyloxyethyl phthalic acid, 2-methacryloyloxyethyl hexahydrophthalic acid and other compounds having a carboxy group and an ester bond, preferably acrylic acid and methacrylic acid. These compounds can be used alone or in combination of two or more.

  The soluble polyimide is a polyimide that can be made liquid by the organic solvent as described above.

[Process for forming resist film 4 ']
Next, the positive resist composition solution of the present invention is applied onto the lower layer film 3 ′ using a spinner or the like, and then pre-baked (PAB treatment) to form a resist film 4 ′. A laminated body is obtained in which a base film 3 ′ and a resist film 4 ′ made of the positive resist composition of the present invention are laminated on the magnetic film 2 ′.
Although prebaking conditions change with kinds of each component in a composition, a mixture ratio, a coating film thickness, etc., they are 70-150 degreeC normally, Preferably it is 80-140 degreeC, and is about 0.5 to 60 minutes.
An organic or inorganic antireflection film may be provided between the base film and the resist film.

In this laminated body, the thickness of the base film 3 ′ and the resist film 4 ′ is preferably 15 μm or less in total from the balance of throughput considering the target aspect ratio and the time required for etching the base film 3 ′. More preferably, it is 5 μm or less. The total lower limit value is not particularly limited, but is preferably 0.1 μm or more, more preferably 0.35 μm or more.
The thickness of the base film 3 ′ is preferably 20 to 10,000 nm, more preferably 30 to 5000 nm, and still more preferably 30 to 3000 nm. By setting the thickness of the base film 3 ′ within this range, there are effects that a resist pattern with a high aspect ratio can be formed and sufficient etching resistance can be secured during substrate etching.
The thickness of the resist film 4 ′ is preferably 50 to 1000 nm, more preferably 100 nm to 800 nm, and still more preferably 100 to 500 nm. By setting the thickness of the resist film 4 ′ within this range, there are effects that the resist pattern 4 can be formed with high resolution, and etching resistance to an alkaline developer, ionic etching, etc. can be sufficiently obtained.

In a resist laminate in which a resist pattern is formed, it is preferable that a pattern with a high aspect ratio can be formed without causing pattern collapse or the like. As the pattern has a higher aspect ratio, the fine pattern can be formed on the support as described later with higher accuracy.
The aspect ratio here is the ratio (y / x) of the height y of the base pattern 3 to the pattern width x of the resist pattern. The pattern width x of the resist pattern is the same as the width of the base pattern 3 after being transferred to the base pattern 3.
The pattern width means the width of a ridge (line) when the resist pattern is a line pattern such as a line and space pattern or an isolated line pattern. When the resist pattern is a hole pattern, the pattern width refers to the inner diameter of the formed hole (hole). Further, when the resist pattern is a cylindrical dot pattern, it means the diameter. Each of these pattern widths is a width below the pattern.
According to the positive resist composition of the present invention, a pattern with a high aspect ratio can be easily provided. In the case of a dot pattern or an isolated line pattern, for example, a dot pattern or an isolated line pattern having an aspect ratio of 8 or more and 20 or less that cannot be achieved by a conventional resist composition with respect to the base pattern 3 having a film thickness of 2.5 μm is created. Can do. In the case of a trench pattern, for example, a trench pattern having an aspect ratio of 10 to 20 that cannot be achieved by a conventional resist composition can be formed on the underlying pattern 3 having a film thickness of 2.5 μm. In any case, the conventional resist composition has a limit of around an aspect ratio of 5.

[Resist pattern formation process]
Next, the resist film 4 ′ is selectively exposed through a desired mask pattern. The wavelength used for the exposure is not particularly limited, and ArF excimer laser, KrF excimer laser, F ₂ excimer laser, EUV (extreme ultraviolet), VUV (vacuum ultraviolet), EB (electron beam), X-ray, soft X-ray, etc. Can be used. In particular, the photoresist composition according to the present invention is effective for KrF excimer laser and EB (electron beam). When EB is used, selective electron beam irradiation through a mask or drawing may be used.

Next, after the exposure process is completed, PEB (post-exposure heating) is performed.
The PEB condition varies depending on the type of each component in the composition, the blending ratio, the coating film thickness, and the like, but is usually 70 to 150 ° C., preferably 80 to 140 ° C., and about 0.5 to 60 minutes.

  Subsequently, when development processing is performed using an alkaline developer composed of an alkaline aqueous solution, for example, an aqueous solution of 0.05 to 3% by mass, preferably 0.05 to 3% by mass of tetramethylammonium hydroxide, a predetermined film of the resist film 4 ′ is obtained. The range (exposed portion) is developed, and a resist pattern 4 is obtained as shown in FIG.

[Over-etching process]
Next, using the obtained resist pattern 4 as a mask pattern, the base film 3 ′ is dry-etched to form the base pattern 3 on the base film 3 ′.
At this time, by performing over-etching of the base film 3 ′, the base film 3 ′ located under the resist pattern 4 is removed, and only the lower part near the center of the resist pattern 4 remains. As a result, as shown in FIG. 1 (b), 'and base pattern 3, which from the width W ² resist film 4' narrow base film 3 having a width W ¹ of a resist pattern 4 which in cross-section battledore A lift-off pattern 5 is obtained.
In the present invention, as described above, since dry etching can be used for over-etching when the lift-off pattern 5 is formed, fine dimensional control can be performed as compared with the conventional method using alkali development. Therefore, for example, the width W ¹ of the base pattern can be controlled to about 40 nm.

  Known dry etching methods include chemical etching such as downflow etching and chemical dry etching; physical etching such as sputter etching and ion beam etching; and chemical and physical etching such as RIE (reactive ion etching). This method can be used.

  The most common dry etching is parallel plate RIE. In this method, first, a resist laminate is put in a chamber of an RIE apparatus, and a necessary etching gas is introduced. When a high frequency voltage is applied to the holder of the resist laminate placed in parallel with the upper electrode in the chamber, the gas is turned into plasma. In the plasma, there are charged particles such as positive and negative ions and electrons, and neutral active species. When these etching species are adsorbed on the lower organic layer, a chemical reaction occurs, the reaction product is detached from the surface and exhausted to the outside, and etching proceeds.

  Etching gas includes oxygen, sulfur dioxide, etc., but the etching with oxygen plasma has high resolution, the silicone resin used in the present invention, particularly the silsesquioxane resins (A11), (A12), Oxygen is preferably used because (A21) and the like have high etching resistance to oxygen plasma and are used for general purposes.

"Patterning method"
[Ionic etching process of magnetic film 2 ']
Next, the lead portion of the magnetic head is manufactured using the lift-off pattern 5 obtained as described above.
When ionic etching is performed using the lift-off pattern 5 composed of the tapered resist pattern 4 and the base pattern 3 shown in FIG. 1B as a mask, the lift-off pattern is obtained as shown in FIG. 5 is etched, the magnetic film 2 'below the lift-off pattern 5 remains, and the magnetic film pattern 2 is printed.
Examples of ionic etching at this time include anisotropic etching such as ion milling. A conventionally well-known method can be applied to ion milling, and for example, it can be performed by an ion beam milling apparatus IML series manufactured by Hitachi, Ltd.

[Sputtering process]
When sputtering is further performed, an electrode film 6 is formed on the lift-off pattern 5 and on the substrate 1 around the magnetic film pattern 2 as shown in FIG.
For this sputtering, a conventionally known method can be applied. For example, it can be carried out by using a sputtering apparatus ISM-2200 or ISP-1801 manufactured by Hitachi, Ltd.

[Lift-off process]
Finally, the base pattern 3 is etched by dry etching to remove the lift-off pattern 5 (lift-off), whereby the substrate 1 and the magnetic film pattern 2 formed thereon are formed as shown in FIG. And the lead part 20 of the magnetic head which consists of the electrode film 6 formed in the periphery is manufactured.

  In the above embodiment, the magnetic film 2 is laminated on the substrate 1 for the manufacture of the magnetic head. However, the present invention is not limited to this, and the positive resist according to the present invention is used. The composition should be suitably used for all applications for forming a lift-off pattern, for example, when no magnetic film is provided, for example, for manufacturing MRAM (Magnetic Random Access Memory), MEMS (Micro Electro Mechanical Systems), etc. Can do.

  As described above, a fine lift-off pattern can be formed by using the positive resist composition of the present invention. Further, the lift-off pattern obtained in this way has a good resist pattern portion with a highly rectangular cross-sectional shape, is less prone to pattern collapse, and has excellent resolution.

EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated in detail, the scope of the present invention is not limited to these Examples.
Synthesis Example 1 (Synthesis example of silsesquioxane resin (A11))
Into a 500 ml three-necked flask equipped with a stirrer, a reflux condenser, a dropping funnel and a thermometer, 84.0 g (1.0 mol) of sodium hydrogen carbonate and 400 ml of water were added, and then, p-methoxybenzyl trichloride was added from the dropping funnel. A mixture of 51.1 g (0.20 mol) of chlorosilane, 21.1 g (0.10 mol) of phenyltrichlorosilane and 100 ml of diethyl ether was added dropwise over 2 hours, and the mixture was further aged for 1 hour. After completion of the reaction, the reaction mixture is extracted with ether, the ether is distilled off under reduced pressure, 0.2 g of a 10% by weight potassium hydroxide solution is added to the resulting hydrolysis product, and the mixture is heated at 200 ° C. for 2 hours. by, to obtain a copolymer a ₁ consisting of p- methoxybenzyl silsesquioxane and phenyl silsesquioxane.

Next, 50 g of the obtained copolymer A ₁ is dissolved in 150 ml of acetonitrile, 80 g (0.40 mol) of trimethylsilyl iodide is added thereto, and the mixture is stirred for 24 hours under reflux, then 50 ml of water is added, and further for 12 hours. The reaction was stirred under reflux. After cooling, free iodine is reduced with an aqueous sodium hydrogen sulfite solution, the organic layer is separated, the solvent is distilled off under reduced pressure, and the resulting polymer is reprecipitated with acetone and n-hexane and dried by heating under reduced pressure. it is to give a 70 mole% p-hydroxybenzyl silsesquioxane, a copolymer a ₂ comprising a pyrimidin silsesquioxane 30 mol%.

Next, 40 g of the obtained copolymer A ₂ was dissolved in 200 ml of tetrahydrofuran (THF), and 1.0 g of p-toluenesulfonic acid monohydrate and 5.0 g of ethyl vinyl ether were added thereto as an acidic catalyst. The reaction was carried out at 23 ° C. for about 3 hours. Thereafter, the reaction solution was poured into water while stirring to precipitate a polymer, thereby obtaining 40 g of a silsesquioxane resin (X1) represented by the following formula (IX). In the formula, l: m: n = 50 mol%: 20 mol%: 30 mol%, and the mass average molecular weight is 7,500. The degree of dispersion was about 1.7.

Synthesis Example 2 (Synthesis example of silsesquioxane resin (A12))
Into a 500 ml three-necked flask equipped with a stirrer, a reflux condenser, a dropping funnel and a thermometer, 84.0 g (1.0 mol) of sodium hydrogen carbonate and 400 ml of water were added, and then, p-methoxybenzyl trichloride was added from the dropping funnel. A mixture of 51.1 g (0.20 mol) of chlorosilane, 21.1 g (0.10 mol) of phenyltrichlorosilane and 100 ml of diethyl ether was added dropwise over 2 hours, and the mixture was further aged for 1 hour. After completion of the reaction, the reaction mixture is extracted with ether, the ether is distilled off under reduced pressure, 0.2 g of a 10% by weight potassium hydroxide solution is added to the resulting hydrolysis product, and the mixture is heated at 200 ° C. for 2 hours. by, to obtain a copolymer a ₁ consisting of p- methoxybenzyl silsesquioxane and phenyl silsesquioxane.

Next, 50 g of the obtained copolymer A ₁ is dissolved in 150 ml of acetonitrile, 80 g (0.40 mol) of trimethylsilyl iodide is added thereto, and the mixture is stirred for 24 hours under reflux, then 50 ml of water is added, and further for 12 hours. The reaction was stirred under reflux. After cooling, free iodine is reduced with an aqueous sodium hydrogen sulfite solution, the organic layer is separated, the solvent is distilled off under reduced pressure, and the resulting polymer is reprecipitated with acetone and n-hexane and dried by heating under reduced pressure. it is to give p- hydroxybenzylsilsesquioxane and oxane 70 mol%, the copolymer a ₂ consisting of a phenyl silsesquioxane 30 mol%.

Next, 40 g of the obtained copolymer A ₂ was dissolved in 200 ml of tetrahydrofuran (THF), and 1.0 g of p-toluenesulfonic acid monohydrate and 6.5 g of cyclohexyl vinyl ether were added thereto as an acidic catalyst. The reaction was carried out at 23 ° C. for about 3 hours. Thereafter, the reaction solution was poured into water while stirring to precipitate a polymer, thereby obtaining 40 g of a silsesquioxane resin (X2) represented by the following formula (X). In the formula, l: m: n = 55 mol%: 15 mol%: 30 mol%, and the mass average molecular weight is 7,600.

Example 1
100 parts by mass of the silsesquioxane resin (X1) obtained in Synthesis Example 1 is dissolved in 950 parts by mass of ethyl lactate, 3 parts by mass of triphenylsulfonium trifluoromethanesulfonate, and 2 parts by mass of bis (cyclohexylsulfonyl) diazomethane. And 0.25 parts by mass of triethanolamine were added to prepare a positive resist composition (silicon content (Si content) 16.20% by mass relative to the total solid content).

Next, on the silicon substrate, TBLC-100 (manufactured by Tokyo Ohka Kogyo Co., Ltd.) was applied as a base film material using a spinner and baked at 230 ° C. for 90 seconds to form a base film having a thickness of 2500 nm.
On the base film, the positive resist composition obtained previously was applied using a spinner, baked at 95 ° C. for 90 seconds, and dried to form a resist film having a thickness of 300 nm.
Next, a KrF excimer laser (248 nm) was applied to the resist film with a halftone type (transmission) using a KrF exposure apparatus NSR-S203B (Nikon Corporation; NA (numerical aperture) = 0.68, σ = 0.75). Irradiation selectively through a mask pattern with a rate of 6%).
Then, PEB treatment was performed at 95 ° C. for 90 seconds, and development treatment was further performed at 23 ° C. with a 2.38 mass% tetramethylammonium hydroxide aqueous solution for 60 seconds to obtain an isolated line pattern (I) of 250 nm. .
The isolated line pattern (I) is dry-etched with oxygen plasma using a high vacuum RIE apparatus (manufactured by Tokyo Ohka Kogyo Co., Ltd.), and the isolated line pattern (II) is transferred to the underlying film, thereby producing a line width. A lift-off pattern consisting of an isolated line pattern (II) having a thickness of 250 nm and a thickness of 2500 nm was obtained.
The obtained pattern had very high perpendicularity and an aspect ratio of 10. Moreover, when a 300 nm dot pattern was formed using the same method and dry etching was performed, a dot pattern (II) ′ having a line width of 300 nm and a film thickness of 2500 nm (aspect ratio of 8.3) was obtained. The obtained patterns (II) and (II) ′ had very high verticality, were fine and had a high aspect ratio.

Example 2
100 parts by mass of the silsesquioxane resin (X2) obtained in Synthesis Example 2 is dissolved in 950 parts by mass of ethyl lactate, 3 parts by mass of triphenylsulfonium trifluoromethanesulfonate, 0.3 parts by mass of triethanolamine. And 15 parts by mass of a low molecular weight dissolution inhibitor (DI22) represented by the following formula (XI) were added to prepare a positive resist composition.

（Ｒは−ＣＨ_２ＣＯＯ−ｔｅｒｔ−ブチル基である）

(R is a —CH ₂ COO-tert-butyl group)

  Using the obtained positive resist composition, pattern formation was performed using the same method as in Example 1, and the underlying film was etched. As a result, an isolated line pattern having a line width of 250 nm and a film thickness of 2500 nm (aspect ratio: 10) As a result, a dot pattern (aspect ratio 8.3) having a line width of 300 nm and a film thickness of 2500 nm was obtained. The obtained pattern was very vertical, fine and had a high aspect ratio.

Comparative Example 1
100 parts by mass of a copolymer composed of hydroxystyrene / styrene / tert-butyl acrylate (molar ratio 66.5 / 8.5 / 25), and 2 parts of bis (tert-butylphenyl) iodonium nonafluorobutanesulfonate as an acid generator Part, 0.07 parts by mass of triethylamine and 0.09 parts by mass of salicylic acid were dissolved in 300 parts by mass of a mixed solvent of propylene glycol monomethyl ether acetate and propylene glycol monomethyl ether (mass ratio 2: 8) to obtain a positive resist composition. It was adjusted.

Next, the positive resist composition obtained above was applied onto a silicon substrate using a spinner, baked at 130 ° C. for 150 seconds, and dried to form a 2500 nm-thick resist film.
Next, a KrF excimer laser (248 nm) is selectively applied to the resist film through a mask pattern by a KrF exposure apparatus FPA3000EX3 (manufactured by Canon; NA (numerical aperture) = 0.55, σ = 0.55). Irradiated.
Then, PEB treatment was carried out at 120 ° C. for 150 seconds, and further development treatment was carried out at 23 ° C. with a 2.38 mass% tetramethylammonium hydroxide aqueous solution for 120 seconds, whereby an 563 nm isolated line pattern (aspect ratio 4.4) was obtained. )

Example 3
100 parts by mass of the silsesquioxane resin (X1) obtained in Synthesis Example 1, 8 parts by mass of bis-O- (n-butylsulfonyl) -α-dimethylglyoxime, 0.4 parts by mass of triphenylsulfonium nonafluorobutanesulfonate Part, 1.5 parts by weight of trioctylamine, and 4 parts by weight of a low molecular weight dissolution inhibitor (DI22) represented by the formula (XI) are dissolved in 950 parts by weight of propylene glycol monomethyl ether acetate to form a positive resist composition (Si content 16.2%).
The positive resist composition was applied to an 8-inch silicon substrate subjected to hexamethylsilazane treatment or an 8-inch silicon substrate coated with a lower layer film based on a novolac resin. Thereafter, a baking process was performed at 90 ° C. for 90 seconds to obtain a resist film having a thickness of 300 nm. The substrate is drawn with an EB drawing apparatus (Hitachi High Technology Co., Ltd., HL-800D, acceleration voltage 70 kV), baked at 100 ° C. for 90 seconds, developed with TMAH 2.38% for 60 seconds, with pure water After rinsing and shaking off for 30 seconds, baking was performed at 100 ° C. for 60 seconds. By this processing, a resolution of 150 nm was obtained for L / S and 150 nm for the Dot pattern.
Using the resist pattern as a mask, the lower layer film 2500 nm based on the novolak resin was etched to form a lift-off pattern with a thickness of 2500 nm and 150 nm L / S and 150 nm Dot.
The obtained L & S and dot patterns were very high in perpendicularity, fine and had a high aspect ratio with an aspect ratio of 16.7.

Example 4
A positive resist composition (Si content of 11.1) was obtained in the same manner as in Example 1 except that the silsesquioxane resin (X1) was changed to 100 parts by mass of the silsesquioxane resin (X2) obtained in Synthesis Example 2. 8%), a resist pattern is formed in the same manner as in Example 3, and the lower layer film 2500 nm based on the novolak resin is etched by using the resist pattern as a mask to have a film thickness of 2500 nm. A fine pattern for lift-off of S and 150 nm Dot was formed.
The obtained L & S and dot patterns were very high in perpendicularity, fine and had a high aspect ratio with an aspect ratio of 16.7.

In Examples 1 to 4, a pattern with high verticality, fineness, and high aspect ratio could be formed. By using this positive resist composition for lift-off, further miniaturization of semiconductor elements such as MRAM, MEMS, and magnetic head can be realized.
In Comparative Example 1, an attempt was made to form a pattern with a high aspect ratio as in the Examples using a conventional resist composition without using the lift-off pattern forming method. However, since the resist film is thick, the resolution is poor and the aspect ratio is low, which is inferior to the present invention. Even if the lift-off pattern forming method as in the examples is used, the resist film cannot withstand dry etching when the pattern is transferred to the lower layer because the conventional resist composition has poor etching resistance. Since it is obvious to those skilled in the art that the high-aspect-ratio pattern cannot be formed by eroding to the lower layer film, no confirmation experiment was performed.

It is a schematic diagram for demonstrating the process of forming a magnetic film pattern using the lift-off method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 '... Magnetic film, 2 ... Magnetic film pattern, 3' ... Base film, 3 ... Base pattern, 4 '... Resist film, 4 ... Resist pattern, 5 ... Lift-off pattern, 6 ... Electrode film, 10 ... Magnetic head (lead part)

Claims (14)

In a positive resist composition for lift-off comprising a base resin component (A) and an acid generator component (B) that generates acid upon exposure,
A positive resist composition for lift-off, wherein the base resin component (A) is a silicone resin.   The lift-off positive resist composition according to claim 1, wherein the lift-off positive resist composition has a silicon content of 5 to 30 mass% with respect to the total solid content.   3. The resin component (A1) according to claim 1, wherein the base resin component (A) is a resin component (A1) having an acid dissociable, dissolution inhibiting group, and the dissolution inhibiting group is dissociated by the action of an acid to increase alkali solubility. A positive resist composition for lift-off. The resin component (A1) is represented by the following general formula (I)

(In the formula, R ¹ represents a linear or branched alkylene group having 1 to 5 carbon atoms.)
A structural unit (a1) represented by the following general formula (II)

(In the formula, R ² represents a linear or branched alkylene group having 1 to 5 carbon atoms, and R ³ represents an acid dissociable, dissolution inhibiting group.)
A structural unit (a2) represented by the following general formula (III)

The positive resist composition for lift-off of Claim 3 containing the silsesquioxane resin (A11) which has a structural unit (a3) represented by these.   The total content of the structural units (a1) and (a2) with respect to the total of all the structural units of the silsesquioxane resin (A11) is 50 mol% or more, and the structural units (a1) and (a2) The lift-off positive resist composition according to claim 4, wherein the content ratio of the structural unit (a2) with respect to the total is 8 mol% or more.   The positive resist composition for lift-off according to claim 4 or 5, wherein the acid dissociable, dissolution inhibiting group is an alkoxyalkyl group.   The positive resist composition for lift-off according to claim 6, wherein the alkoxyalkyl group is a 1-ethoxyethyl group. The resin component (A1) is represented by the following general formula (I)

(In the formula, R ¹ represents a linear or branched alkylene group having 1 to 5 carbon atoms.)
A structural unit (a1) represented by the following general formula (V)

(In the formula, R ⁵ represents a linear or branched alkylene group having 1 to 5 carbon atoms, R ⁶ represents an alkyl group having 1 to 5 carbon atoms, and R ⁷ represents an alkyl group having 1 to 5 carbon atoms. Alternatively, it represents a hydrogen atom, and R ⁸ represents an alicyclic hydrocarbon group having 5 to 15 carbon atoms.
The positive resist composition for lift-off of Claim 3 containing the silsesquioxane resin (A12) which has a structural unit (a5) represented by these. The silsesquioxane resin (A12) is further represented by the following general formula (III)

The positive resist composition for lift-off of Claim 8 which has a structural unit (a3) represented by these.   The total content of the structural units (a1) and (a5) with respect to the total of all the structural units of the silsesquioxane resin (A12) is 50 mol% or more, and the structural units (a1) and (a5) The positive resist composition for lift-off according to claim 8 or 9, wherein a content ratio of the structural unit (a5) with respect to the total is 5 mol% or more and 50 mol% or less.   The lift-off according to any one of claims 1 to 10, further comprising a low molecular weight dissolution inhibitor (C) having an acid dissociable dissolution inhibiting group, which is dissociated by the action of an acid. Positive resist composition.   The low molecular weight dissolution inhibitor (C) is a phenol compound in which a phenolic hydroxyl group is protected with an acid dissociable dissolution inhibiting group, or a carboxy compound in which a carboxy group is protected with an acid dissociable dissolution inhibiting group. The positive resist composition for lift-off as described.   The positive resist composition for lift-off according to any one of claims 1 to 12, wherein the acid generator component (B) is an onium salt acid generator and / or a diazomethane acid generator. Furthermore, the positive resist composition for lift-off as described in any one of Claims 1-13 containing a nitrogen-containing organic compound (D).

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