JP2006330231A - Positive photoresist composition for lift-off process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoresist composition for a lift-off process which facilitates resist stripping by ozone water without using an organic solvent and facilitates formation of a wiring pattern with high processability and reliability by a lift-off process, for example, on a semiconductor substrate or a liquid crystal substrate. <P>SOLUTION: The photoresist composition for a lift-off process contains 100 parts by weight of a novolac resin having a structure expressed by formula (1): -(CH<SB>2</SB>-C<SB>6</SB>H<SB>4-x</SB>(OH)<SB>x</SB>-CH<SB>2</SB>-C<SB>6</SB>H<SB>3-y</SB>(OH)(CH<SB>3</SB>)<SB>y</SB>)<SB>z</SB>- and having 2,000 to 10,000 weight average molecular weight expressed in terms of polystyrene and 10 to less than 40 parts by weight of a naphthoquinonediazide group-containing compound having 1.4 to 2.6 ester linkages in average per one molecule. In formula (1), x represents 2 or 3; y represents 0, 1, 2 or 3; and z represents an integer of 1 or more. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a lift-off positive photoresist composition used, for example, when forming a wiring pattern on a semiconductor substrate or a liquid crystal substrate, and more specifically, a wiring pattern having high workability and reliability by a lift-off method. The present invention relates to a positive photoresist composition for lift-off that enables formation of a film.

  Conventionally, when a wiring pattern such as an aluminum electrode is formed on a semiconductor substrate or a liquid crystal substrate, an etching process such as dry etching or wet etching is performed.

  Non-Patent Document 1 below discloses a method of forming a wiring pattern by performing an etching process on the surface of a substrate. In Non-Patent Document 1, a metal layer is formed on a substrate by sputtering or vapor deposition, and after a resist film is further formed in a pattern on the metal layer, an etching process is performed on a non-formed portion of the resist film on the metal layer. ing. Thereafter, the resist film is stripped using a stripping solution to form a wiring pattern.

  In Non-Patent Document 1, when the metal layer is made of gold, tantalum, or the like, etching cannot be performed effectively, and it is difficult to form a wiring pattern.

  In recent years, a lift-off method has been used for forming a wiring pattern so that the wiring pattern can be easily formed even when the metal layer is made of gold, tantalum, or the like.

  In the lift-off method, a resist film is formed in a pattern on a substrate, and a metal layer made of gold or the like is further formed on the non-formed portion of the resist film and the resist film by sputtering or vapor deposition. Thereafter, the resist film and the metal layer formed thereon are stripped using a stripping solution, and the metal layer is left only in the non-formed portion of the resist film, thereby forming a wiring pattern. In the lift-off method, since the metal layer formed on the resist film is peeled off from the substrate as the resist film is peeled off, a wiring pattern made of a metal such as gold or tantalum that is difficult to etch can be easily formed.

  However, when a general positive resist composition is used when forming a wiring pattern by the lift-off method, the edge angle of the resist film is usually about 90 to 100 degrees. When forming the metal layer, the metal layer tends to be formed also on the side surface of the resist film. When the metal layer is formed on the side surface of the resist film, the resist film may not be easily peeled off by the stripping solution, and it is difficult to form a wiring pattern. Further, even if the resist film can be peeled off, metal burrs remain and it is difficult to form an accurate wiring pattern.

  Therefore, a negative resist composition in which the edge portion of the resist film can be formed in a reverse taper shape so that the resist film can be easily peeled even when a metal layer is formed on the side surface of the resist film. Has been developed.

Patent Document 1 listed below discloses a negative photosensitive composition capable of forming an overhang-like or inversely tapered resist film. The negative photosensitive composition described in Patent Document 1 includes (A) a component that is cross-linked by light exposure or a heat treatment subsequent to light exposure, (B) an alkali-soluble resin, and (C) a compound that absorbs light to be exposed. Contains at least one. In this negative photosensitive composition, an alkaline aqueous solution is used as a developer.
JP-A-5-165218 VLSI manufacturing technology, Nikkei Business Publications, 1989, page 259

  However, since the negative photosensitive composition described in Patent Document 1 is a negative resist composition, the resolution tends to be inferior to that of a positive resist composition. Furthermore, since the negative photosensitive composition described in Patent Document 1 has a property of crosslinking after exposure, the resist film itself may have poor peelability.

  On the other hand, the positive resist composition tends to be inferior in heat resistance to the negative resist composition. Further, when a positive resist composition is used, the development conditions tend to be limited.

  Moreover, when peeling a resist film, organic solvents, such as acetone, were conventionally used and the load with respect to the environment was large. Furthermore, since a large amount of energy is required to regenerate and reuse acetone after use, a resist composition that can form a resist film that can be easily removed without using acetone or the like is required. It was.

  The object of the present invention is to make it possible to easily remove a resist with ozone water without using an organic solvent in view of the current state of the prior art described above. For example, processing on a semiconductor substrate or a liquid crystal substrate by a lift-off method. An object of the present invention is to provide a lift-off positive photoresist composition that can form a highly reliable and reliable wiring pattern.

  The present invention has a structure in which the main chain has a structure represented by the following formula (1) and has a polystyrene-reduced weight average molecular weight in the range of 2000 to 10000, and an average of 1.4 to 1 per molecule. It contains 10 parts by weight or more and less than 40 parts by weight of a naphthoquinonediazide group-containing compound having 2.6 ester bonds.

_{- (CH 2 -C 6 H 4} -x (OH) x -CH 2 -C 6 H 3-y (OH) (CH 3) y) z - ··· Equation (1)
In the above formula (1), x represents 2 or 3, y represents 0, 1, 2 or 3, and z represents an integer of 1 or more.

In a specific aspect of the present invention, in the above-described formula (1), x is 2, and in the benzene ring represented by C ₆ H _4-x (OH) _x , the two hydroxyl groups are meta-positioned to each other. Is bound to.

In another specific aspect of the present invention, in the above-described formula (1), x is 3, and in the benzene ring represented by C ₆ H _4-x (OH) _x , three hydroxyl groups are adjacent to the benzene ring. Each is attached to three carbons.

In still another specific aspect of the present invention, in the above-described formula (1), y is 0, 1 or 2, and in the benzene ring represented by C ₆ H _3-y (OH) (CH ₃ ) _y , Hydrogen is bonded to a position that is para to the hydroxyl group.

  The present invention has a structure in which the main chain has the structure represented by the formula (1) described above and has a polystyrene-reduced weight average molecular weight in the range of 2000 to 10,000, and an average of 1.4 per molecule. It contains 10 parts by weight or more and less than 40 parts by weight of a naphthoquinonediazide group-containing compound having ˜2.6 ester bonds. Therefore, since it contains a novolak resin having many hydroxyl groups and a naphthoquinonediazide group-containing compound having an average of 1.4 to 2.6 ester bonds per molecule, resist removal using ozone water with a low environmental impact Can be easily performed. Furthermore, the resist composition of the present invention is excellent in developability and sensitivity. Therefore, in the resist composition of the present invention, the resist can be easily peeled off with ozone water, and is excellent in developability and sensitivity. For example, the resist composition is used on a semiconductor substrate or a liquid crystal substrate. A wiring pattern with high workability and reliability can be formed.

In the above formula (1), when x is 2, and in the benzene ring represented by C ₆ H _4-x (OH) _x , two hydroxyl groups are bonded to each other in the meta position, When forming a resist pattern, it is easy to form a surface hardly soluble layer, and it is easy to form a shape suitable for lift-off.

In the above formula (1), x is 3, and in the benzene ring represented by C ₆ H _4-x (OH) _x , three hydroxyl groups are respectively bonded to three adjacent carbons of the benzene ring. However, it is easy to form a surface poorly soluble layer when forming a resist pattern, and it is easy to form a shape suitable for lift-off. _{Furthermore, C 6 H 4-x (} OH) x for skeletal portion is asymmetric, for example, one C ₆ other two hydroxyl groups relative to the hydroxyl group is bonded at positions a meta position H _4-x Unlike the case where the (OH) _x skeleton is symmetrical, the solubility in a nonpolar organic solvent is high.

In the above-mentioned formula (1), y is 0, 1 or 2, and in the benzene ring represented by C ₆ H _3-y (OH) (CH ₃ ) _y , hydrogen at a position that is para to the hydroxyl group. Is more easily formed, it is easier to form a shape suitable for lift-off.

  Details of the present invention will be described below.

  The positive photoresist composition for lift-off of the present invention contains a novolak resin and a naphthoquinonediazide group-containing compound.

  The novolak resin has a structure in which the main chain is represented by the formula (1) described above, and has a polystyrene-equivalent weight average molecular weight in the range of 2000 to 10,000.

  The novolak resin has a larger number of hydroxyl groups than a conventionally used novolak resin. In the decomposition of the novolak resin with ozone-dissolved water, the oxidation of the novolak resin proceeds with ozone. A novolak resin having a large number of hydroxyl groups is susceptible to decomposition by ozone. Therefore, in the positive photoresist composition for lift-off of the present invention, the resist can be easily removed with ozone water without using an organic solvent. On the other hand, the negative resist composition itself is cross-linked, and is difficult to remove with a solvent, and is difficult to remove with ozone water having a low environmental load.

In the above formula (1), as a raw material for constituting the benzene ring represented by C ₆ H _4-x (OH) _x (hereinafter also referred to as benzene ring A), specifically, catechol (1, 2-dihydroxybenzene), resorcinol (1,3-dihydroxybenzene), hydroquinone (1,4-dihydroxybenzene), pyrogallol (1,2,3-trihydroxybenzene), 1,2,4-trihydroxybenzene, or 1,3,5-trihydroxybenzene is mentioned. These may be used independently and 2 or more types may be used together.

In the above formula (1), as a raw material for constituting the benzene ring represented by C ₆ H _3-y (OH) (CH ₃ ) _y (hereinafter also referred to as benzene ring B), phenol, m-cresol 3,5-xylenol, p-cresol, 3,4-xylenol. These may be used independently and 2 or more types may be used together.

  For example, in the raw material constituting the benzene ring B described above, the novolac resin is obtained by alternately copolymerizing methylol groups at two ortho positions with respect to the hydroxyl group by a conventional method and then alternately copolymerizing with the raw material constituting the benzene ring A described above. Obtainable.

  When a novolac resin is constituted using resorcinol or pyrogallol as a raw material for constituting the benzene ring A and using phenol, m-cresol or 3,5-xylenol as a raw material for constituting the benzene ring B, Since the surface can be made a poorly soluble layer when forming the resist pattern, it is preferable.

In the above formula (1), x is 2, and in the benzene ring represented by C ₆ H _4-x (OH) _x , two hydroxyl groups are bonded to each other in the meta position, A novolac resin in which the other hydroxyl group is bonded to the hydroxyl group in the meta position can be obtained using resorcinol (1,3-dihydroxybenzene) as a raw material for constituting the benzene ring A. . With this novolac resin, it is easy to form a surface hardly-solubilized layer when forming a resist pattern, and it becomes easy to form a shape suitable for lift-off.

In the above formula (1), x is 3, and in the benzene ring represented by C ₆ H _4-x (OH) _x , novolak in which three hydroxyl groups are respectively bonded to three adjacent carbons of the benzene ring. The resin can be obtained using pyrogallol (1,2,3-trihydroxybenzene) as a raw material for constituting the benzene ring A. With this novolac resin, it is easy to form a surface hardly-solubilized layer when forming a resist pattern, and it becomes easy to form a shape suitable for lift-off.

In the above-mentioned formula (1), y is 0, 1 or 2, and in the benzene ring represented by C ₆ H _3-y (OH) (CH ₃ ) _y , hydrogen at a position that is para to the hydroxyl group. Can be obtained using phenol, m-cresol or 3,5-xylenol as a raw material for constituting the benzene ring B. In this novolac resin, it is easier to form a surface hardly-solubilized layer when forming a resist pattern, and it becomes easier to form a shape suitable for lift-off.

  In constituting the novolak resin, the molar ratio of the raw material for constituting the benzene ring A and the raw material for constituting the benzene ring B is preferably 1: 0.5 to 1: 1. : 0.65 to 1: 0.9 is more preferable. When the ratio of the raw material for constituting the benzene ring B is less than 0.5, the polystyrene-equivalent weight average molecular weight may be less than 2000. When it is more than 1, the polystyrene-equivalent weight average molecular weight may exceed 10,000. is there. When the molar ratio is 1: 0.65 to 1: 0.9, it is easy to make the polystyrene equivalent weight average molecular weight weight of the novolak resin in the range of 2000 to 10,000.

  The novolak resin has a polystyrene equivalent weight average molecular weight in the range of 2000 to 10,000. If the weight average molecular weight in terms of polystyrene is less than 2,000, the resolution becomes low, and if the weight average molecular weight in terms of polystyrene exceeds 10,000, development becomes difficult.

  The naphthoquinonediazide group-containing compound has an average of 1.4 to 2.6 ester bonds per molecule. If the average number of ester bonds is less than 1.4, the resolution decreases. The average number of ester bonds in the naphthoquinonediazide group-containing compound is 2.6 or less per molecule. If the average number of ester bonds is more than 2.6, the sensitivity may decrease.

  The ester bond per molecule of the naphthoquinonediazide group-containing compound is more preferably 1.8 to 2.3.

  Specifically, the naphthoquinonediazide group-containing compound is obtained by esterifying a naphthoquinonediazide-based photosensitizer with compound X having 1 to 6 benzene rings per molecule and a hydroxyl group bonded to the benzene ring. It is done.

  The naphthoquinone diazide photosensitizer is not particularly limited, but naphthoquinone diazide sulfonic acid chloride, an ester of naphthoquinone diazide sulfonic acid and a polyhydric phenol, for example, 1,2-naphthoquinone diazide-5-sulfonic acid and 2,3 , 4-trihydroxybenzophenone, 1,2-naphthoquinone-diazide-5-sulfonic acid and 2,3,4,4'-tetrahydroxybenzophenone.

  In order to increase the crosslinking efficiency of the resist composition, a naphthoquinonediazide group-containing compound having two ester bonds per molecule is preferable. However, when synthesizing a naphthoquinonediazide group-containing compound, one, two, or three or more different numbers of ester bonds are formed in a plurality of molecules, respectively.

  In synthesizing a naphthoquinonediazide group-containing compound, in order to make the number of ester bonds to a plurality of molecules within an appropriate range, the ratio of the compound X to the naphthoquinonediazide-based photosensitizer is 1: 2-1. : 4 is preferred. If the number of naphthoquinone diazide photosensitizers is less than 2, the average number of ester bonds in one molecule of the naphthoquinone diazide group-containing compound may be less than 1.4. If more than 4, the number of ester bonds is May be larger than 2.6 on average.

  In order to increase the mixing property between the naphthoquinonediazide group-containing compound and the novolak resin, it is necessary to appropriately adjust the hydrophobicity and hydrophilicity. Therefore, the number of hydroxyl groups per molecule of the compound X is 2 to 10. It is preferable that it is 3-6. Further, when the resist composition is used, it is preferable that the number of benzene rings per molecule of the compound X is 4 in order to make it easier to form a surface hardly soluble layer with an alkali developer. More preferably, compound X has 1 to 6 benzene rings and 2 to 10 hydroxyl groups bonded to the benzene ring per molecule. In addition, when the compound X has a plurality of benzene rings, the plurality of benzene rings are preferably located in a straight line.

  Examples of the naphthoquinonediazide group-containing compound include 1,2-benzoquinonediazide-4-sulfonyl group, 1,2-naphthoquinonediazide-4-sulfonyl group, 1,2-naphthoquinonediazide-5-sulfonyl group, and 2,1-naphtho. Quinonediazide-4-sulfonyl group, 2,1-naphthoquinonediazide-5-sulfonyl group, 2,1-naphthoquinonediazide-6-sulfonyl group, 2,1-naphthoquinonediazide-7-sulfonyl group, 2,1-naphthoquinonediazide- Examples thereof include compounds having an 8-sulfonyl group and the like. The naphthoquinonediazide group-containing compound may have these groups alone or may have two or more. Among these, 1,2-naphthoquinonediazide-4-sulfonyl group and 1,2-naphthoquinonediazide-5-sulfonyl group are particularly preferable.

  When a compound having a 1,2-naphthoquinonediazide-4-sulfonyl group is used as the naphthoquinonediazide group-containing compound, the resist composition is particularly sensitive to irradiation with ultraviolet rays having a wavelength in the range of 330 to 420 nm. High resolution. When a compound having a 1,2-naphthoquinonediazide-5-sulfonyl group is used as the naphthoquinonediazide group-containing compound, the resist composition has a high resolution especially for irradiation with ultraviolet rays having a wavelength in the range of 330 to 450 nm. Pattern profile is obtained.

  The naphthoquinonediazide group-containing compound is blended in the range of 10 parts by weight or more and less than 40 parts by weight with respect to 100 parts by weight of the novolak resin. If the naphthoquinonediazide group-containing compound is less than 10 parts by weight, the developability may be inferior, and if it is 40 parts by weight or more, the sensitivity may decrease. The naphthoquinonediazide group-containing compound is preferably blended in the range of 15 to 30 parts by weight with respect to 100 parts by weight of the novolak resin. When the naphthoquinonediazide group-containing compound is blended in the range of 15 to 30 parts by weight, developability, ozonolysis and sensitivity can be further enhanced.

  The present invention uses the above-mentioned naphthoquinonediazide group-containing compound as a photosensitive material. Other materials may be added to the resist composition as long as the effects of the present invention are not impaired. For example, a photosensitive material or the like may be added. Within the scope of the present invention, the resist composition of the present invention may contain two or more kinds of novolak resins, and may contain two or more kinds of the naphthoquinonediazide group-containing compounds.

  A solvent that dissolves the novolak resin and the naphthoquinonediazide group-containing compound is preferably added to the resist composition of the present invention. As the solvent, THF or the like is preferably used.

  In the resist composition of the present invention, it is preferable to add a surfactant such as polyoxyethylene ethers and fluorine-based alkyl esters in order to improve poor application of striations. The surfactant is more preferably added at 1% by weight or less, and further preferably 0.01% by weight or less.

  The resist composition of the present invention is used in steps such as coating, exposure and development on a substrate according to a known method. Examples of the substrate include a silicon wafer and a liquid crystal substrate material.

  When applying the resist composition to the substrate, for example, first, the resist composition is dissolved in an organic solvent so that the total amount of the novolak resin and the naphthoquinonediazide group-containing compound is 5 to 50% by weight. Thereafter, a resist composition is applied to the substrate using a spin coater so as to have a film thickness of about 0.3 to 5 μm. The rotation speed of the spin coating is preferably 500 to 10,000 rotations, and more preferably 3000 to 5000 rotations. The boiling point of the organic solvent for dissolving the resist composition is preferably in the range of 100 to 200 ° C. in order to make the film thickness uniform.

  After applying the resist composition, the substrate is heated on a hot plate to remove the solvent. Thereafter, exposure is performed using a mask, and a desired pattern is printed on the substrate. In the exposure, it is preferable to irradiate light having a wavelength of 436 nm, g-line, 365 nm, i-line, or 330-450 nm. After the exposure, the substrate is subjected to a heat treatment usually called PEB (post-exposure bake) at about 90 to 120 ° C. for about 60 to 120 seconds as necessary. Thereafter, development is performed using an alkaline aqueous solution or the like.

  Specific examples of the alkaline aqueous solution include an aqueous solution of a quaternary ammonium salt such as tetramethylammonium hydroxide. In particular, in the semiconductor process, quaternary ammonium hydroxide is preferably used in order to suppress contamination by alkali metals.

  Hereinafter, the present invention will be described in more detail by giving specific examples and comparative examples of the present invention.

  The polystyrene equivalent weight average molecular weight of the following novolak resin is a value measured by gel permeation chromatography.

(Synthesis of novolac resin R1)
110 g of resorcinol (1,3-dihydroxybenzene), 128 g of 2,6- (bishydroxymethyl) -3,4-xylenol, 1600 g of ethyl lactate and 0.64 g of p-toluenesulfonic acid are placed in a separable flask, and a nitrogen flow. The mixture was stirred at room temperature for 1 hour under reflux with heating. Thereafter, the mixture was stirred at 130 ° C. for 1 hour and cooled to room temperature over 1 hour. Next, reprecipitation treatment was performed using 8 liters of ion-exchanged water, and the solvent was removed by drying under reduced pressure at 60 ° C. to obtain a novolak resin R1. The resulting novolac resin R1 had a polystyrene-reduced weight average molecular weight of 3900.

  The obtained novolac resin R1 was dissolved in THF so that it might become 0.1 weight%.

(Synthesis of novolac resin R2)
In the synthesis of the novolak resin R1, the same procedure was followed except that 2,6- (bishydroxymethyl) -3,5-xylenol was used instead of 2,6- (bishydroxymethyl) -3,4-xylenol. A novolac resin R2 was obtained. The resulting novolak resin R2 had a weight average molecular weight in terms of polystyrene of 4100.

(Synthesis of novolac resin R3)
In the synthesis of the novolak resin R1, a novolak resin R5 was obtained in the same manner except that 144 g of pyrogallol (1,3,5-trihydroxybenzene) was used instead of 110 g of resorcin (1,3-dihydroxybenzene). The resulting novolak resin R5 had a polystyrene-reduced weight average molecular weight of 5,500.

(Synthesis of novolac resin R4)
A novolak resin R3 was obtained in the same manner except that the amount of 2,6- (bishydroxymethyl) -3,4-xylenol was changed from 128 g to 100 g in the synthesis of the novolak resin R1. The resulting novolac resin R3 had a polystyrene equivalent weight average molecular weight of 1,900.

(Synthesis of novolac resin R5)
A novolac resin R4 was obtained in the same manner except that the amount of 2,6- (bishydroxymethyl) -3,4-xylenol was changed from 128 g to 167 g in the synthesis of the novolak resin R1. The resulting novolac resin R4 had a weight average molecular weight in terms of polystyrene of 11,500.

(Synthesis of novolac resin R6)
In the synthesis of the novolak resin R1, a novolak resin R6 was obtained in the same manner except that p-cresol was used instead of resorcin (1,3-dihydroxybenzene). The resulting novolak resin R6 had a weight average molecular weight in terms of polystyrene of 4800.

(Synthesis of novolac resin R7)
In the synthesis of the novolak resin R1, an attempt was made to obtain the novolak resin R7 in the same manner except that 1,3,5-trihydroxybenzene was used instead of resorcin (1,3-dihydroxybenzene). , 3,5-trihydroxybenzene could not be dissolved in a predetermined amount of ethyl lactate, and novolak resin R7 could not be synthesized.

(S1 synthesis of naphthoquinonediazide group-containing compound)
2 moles of 2,3,4,4'-tetrahydroxybenzophenone (2 benzene rings and 4 hydroxyl groups per molecule) and 2 moles of 1,2-naphthoquinonediazide-5-sulfonic acid chloride Dissolved in THF. To this solution, 105% equivalent of triethylamine of 1,2-naphthoquinonediazide-5-sulfonic acid chloride was dropped and reacted over 10 minutes to synthesize naphthoquinonediazide group-containing compound S1. The number of ester bonds per molecule of the obtained naphthoquinonediazide group-containing compound S1 was 2.0 on average.

(Examples and Comparative Examples)
Among the obtained novolak resins R1 to R7, the novolak resins R1 to R3 and R6 have the structure represented by the above-described formula (1) and have a polystyrene equivalent weight average molecular weight in the range of 2000 to 10,000.

  In Examples and Comparative Examples, 100 parts by weight of any of the novolak resins R1 to R7 shown in Table 1 below and the compounding amount of naphthoquinonediazide group-containing compound shown in Table 1 below were dissolved in 4 parts by weight of ethyl lactate. Thus, a positive photoresist composition for lift-off was prepared.

  In addition, application | coating to the board | substrate of resist composition, exposure, and image development were performed as follows.

  The resist composition was dissolved in ethyl lactate so that the resin component of the novolak resin and the naphthoquinone diazide group-containing compound was 20% by weight to prepare an ethyl lactate solution.

  An ethyl lactate solution was applied on a 3-inch silicon wafer so that the spin coat rotation speed was 3000 rpm and the film thickness after drying was 1 μm. Thereafter, the silicon wafer coated with the ethyl lactate solution was heated at 120 ° C. for 1 minute to remove the solvent. Further, after being exposed to 365 nm i-line, it was further heated at 120 ° C. for 1 minute, and post-exposure baking (PEB).

  In the development, the silicon wafer was treated for 1 minute with an aqueous solution of 0.476% by weight of tetramethylammonium hydroxide, and then washed with pure water.

  The positive photoresist composition for lift-off was evaluated for developability, ozone decomposability, lift-off shape, and sensitivity as follows.

(Developability)
Using an aqueous solution of tetramethylammonium hydroxide, the exposed part was removed within 1 minute, and the film reduction rate of the non-exposed part when the exposed part was completely removed was observed and evaluated according to the following evaluation criteria.
○: Film reduction rate is 3% or less ×: Film reduction rate is greater than 3%

(Ozone degradability)
The peeling rate was measured using 100 ppm ozone water and evaluated according to the following evaluation criteria.
○: 500 nm / min or more ×: Slower than 500 nm / min

(Lift-off shape)
At the edge of the resist film, the angle of the internal angle formed by the resist film and the substrate surface was observed and evaluated according to the following evaluation criteria.
○: Less than 75 degrees ×: 75 degrees or more

(sensitivity)
The necessary exposure was measured and evaluated according to the following evaluation criteria.
○: 250 mJ / cm ² or less ×: More than 250 mJ / cm ²

  The results are shown in Table 1.

(Evaluation results)
In the resist composition of Comparative Example 1, since the molecular weight of the novolak resin was too small, dissolution of the non-exposed area could not be suppressed and development could not be performed.

  In the resist composition of Comparative Example 2, the sensitivity was poor because the molecular weight of the novolak resin was too large. Further, since the molecular weight of the novolak resin is large, the performance as a resist that is usually used is improved, and the lift-off shape is difficult to be a T-top shape.

  The resist composition of Comparative Example 3 was inferior in ozone decomposability because the novolak resin had one hydroxyl group in the benzene ring A.

  In the resist composition of Comparative Example 4, the sensitivity was poor because the amount of the naphthoquinonediazide group-containing compound was too large. Further, since the esterification rate is too high, the performance as a resist that is usually used is improved, and the lift-off shape is difficult to be a T-top shape.

  In the resist composition of Comparative Example 5, the amount of the naphthoquinonediazide group-containing compound was too small, so there was no difference in solubility between the unexposed area and the exposed area, and development was not possible.

Claims (4)

100 parts by weight of a novolak resin having a main chain having a structure represented by the following formula (1) and having a polystyrene-reduced weight average molecular weight in the range of 2000 to 10,000, and an average of 1.4 to 2.6 per molecule A positive photoresist composition for lift-off, comprising 10 parts by weight or more and less than 40 parts by weight of a naphthoquinonediazide group-containing compound having an ester bond.
_{- (CH 2 -C 6 H 4} -x (OH) x -CH 2 -C 6 H 3-y (OH) (CH 3) y) z - ··· Equation (1)
In the above formula (1), x represents 2 or 3, y represents 0, 1, 2 or 3, and z represents an integer of 1 or more. In the formula (1), x is 2, and in the benzene ring represented by C ₆ H _4-x (OH) _x , two hydroxyl groups are bonded to each other in the meta position. The positive photoresist composition for lift-off as described. In the formula (1), x is 3, and in the benzene ring represented by C ₆ H _4-x (OH) _x , three hydroxyl groups are respectively bonded to three adjacent carbons of the benzene ring. Item 2. A positive photoresist composition for lift-off according to Item 1. In the formula (1), y is 0, 1 or 2, and in the benzene ring represented by C ₆ H _3-y (OH) (CH ₃ ) _y , hydrogen is present at the position that is para to the hydroxyl group. The positive photoresist composition for lift-off according to any one of claims 1 to 3, which is bonded.