JP2008070480A - Photoresist solvent and photoresist composition for slit coating using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoresist solvent for enabling high speed application in slit coating without lowering a solid-contained content, and also to provide a photoresist composition for enabling the high speed application by the slit coating. <P>SOLUTION: In the photoresist solvent used for the photoresist composition applied on a substrate by a slit coating method, 10 wt.% or more by regarding the weight of the solvent as a reference is low-viscosity solvent of 1.1 cp or less of viscosity at a temperature of 20°C. The photoresist composition containing the above solvent, an alkali-soluble resin, and a photosensitive substance is provided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a solvent used in a photoresist composition. In particular, the present invention relates to a solvent suitable for use in a photoresist composition suitable for application at high speed by slit coating.

  For example, in the production process of a flat panel display (hereinafter sometimes referred to as FPD), the photosensitive composition is applied onto a glass substrate. Here, conventionally, a spin coating method has been used for coating a small-sized glass substrate. However, this spin coating method is not suitable for applying large size substrates. Therefore, a slit coating method or a slot coating method may be used as an alternative method. A feature of these methods is that a desired amount of resist composition is supplied from a nozzle moving on the surface of the substrate to form a film. In some cases, the nozzle is fixed and the glass substrate may move. The substrate coated in this way is subsequently dried and cured, the solvent in the composition is removed and further processing is performed. A faster manufacturing method is required for higher productivity and cost reduction as the size of the substrate increases. That is, it is necessary to increase the speed of the nozzle that moves on the substrate to shorten the time required for coating.

  On the other hand, the coating liquid capable of high-speed coating requires special characteristics, and it is important that the coating does not peel off during the coating process, and coating unevenness does not occur. In general, the coating speed of the recent slit coating is at most about 200 mm / s. In order to increase the productivity of the product, it is effective to increase the coating speed. However, in order to increase the upper limit of the coating speed, the viscosity of the coating liquid is an important parameter. It is expected that the coating speed can be increased by lowering the viscosity of the coating solution. It is well known that the viscosity of a photoresist composition depends on the solids content. Most of the solid content of the photoresist composition is a high molecular weight polymer, such as a novolac resin, and increasing its content increases the viscosity. Therefore, the viscosity can be lowered by lowering the solid content, that is, increasing the solvent content. However, if the solid content is lowered, that is, the solvent content is increased, a large amount of solvent must be removed in the drying step, which is not preferable. Moreover, when the dilution is high and the viscosity is low, the shelf life of the photoresist composition may be impaired. Furthermore, it is conceivable that the uniformity of the coating film after drying is impaired due to the large content of the solvent.

By the way, in the field of photoresist, various coating compositions have been studied, and the use of various solvents as components thereof has also been studied. In such examination, the example using a solvent with low viscosity is also made (patent documents 1-3). However, since these studies do not focus on the viscosity of the solvent, the solvents are not distinguished according to the viscosity. In addition, these techniques are intended for spin coating applications, what solvents are suitable for slit coating, and what solvents should be selected for high speed application in slit coating without problems. There was no suggestion about.
JP 9-21845 A Japanese Laid-Open Patent Publication No. 10-221841 JP 2001-117221 A

  An object of the present invention is to provide a photoresist solvent that enables high-speed application in slit coating without reducing the solid content, and a photoresist composition that can be applied at high speed by slit coating.

  The solvent for photoresist according to the present invention is used for a photoresist composition applied on a substrate by a slit coating method, and the viscosity at 20 ° C. is 10% by weight or more based on the weight of the solvent. It is a low-viscosity solvent of .1 cp or less.

  Moreover, the photoresist composition for slit coating according to the present invention comprises the above-mentioned photoresist solvent, an alkali-soluble resin, and a photosensitive substance.

  By using the photoresist solvent of the present invention, it is possible to obtain a photoresist composition that can be applied at high speed without causing film peeling or the like by slit coating. Furthermore, by using the photoresist solvent of the present invention, it is possible to apply a photoresist composition having a high solid content, and part of the solvent removal step can be omitted, and cost reduction can be achieved. Improvement in film thickness uniformity and pattern shape can be achieved.

  The present inventors have found that the problem in high-speed coating can be solved by using a specific photoresist solvent without using a highly diluted photoresist composition as described above. The greatest feature of such a solvent for photoresist is that it comprises a low viscosity solvent having a viscosity at 20 ° C. of less than 1.1 cp. Furthermore, these photoresist solvents need to be able to dissolve all of the components in the photoresist composition. In the photoresist composition for FPD application, the main components of the solid content are usually an alkali-soluble resin and a photosensitive substance. In the field, the most widely used solvents for photoresists are propylene glycol monomethyl ether acetate (PGMEA: viscosity 1.2 cp at 20 ° C.), propylene glycol methyl ether (PGME: viscosity 1.8 cp at 20 ° C.), And ethyl lactate (EL: viscosity at 20 ° C. 2.8 cp). The composition viscosity necessary for applying a photoresist composition at a high speed by the slit coating method is generally 4 cp or less, preferably 3 cp or less. Therefore, in the case of preparing a photoresist composition using a solvent having a high viscosity as described above. Solids content is limited. Since the viscosity of a photoresist composition is strongly dependent on the type of polymer used in the photoresist composition and in particular on its molecular weight, the relationship between solids content and viscosity cannot be fully correlated. In any case, in order to make the viscosity of the polymer solution constant, the lower the viscosity of the solvent itself, the higher the solid content.

The present inventors have prepared a carbonyl group (—C (O) —), a carboxylic acid ester group (—C (O) —O—), a carbonate group (—O—C (O) —O—), a cyano group ( It has been found that solvents having —CN), or ether linkages (—O—), or aromatic units, or combinations thereof are well suited to suitable photoresist compositions for use in high speed coating. That is, the solvent according to the present invention preferably contains these groups. On the other hand, hydroxy (—OH) and amine groups (—NH ₂ , —NHR: where R is a substituent such as an alkyl group) should be avoided, preferably not included at all. This is because these groups increase the viscosity of the solution by acting as a hydrogen bond hydrogen donor. Examples of such a solvent include ketones, carboxylic acid alkyl esters, dialkyl ethers, dialkyl carbonates, nitriles, and aromatic compounds.

  Further, a solvent for a photoresist is required to have a flash point higher than 21 ° C. from the viewpoint of practicality, thereby indicating the extreme flammability (danger sign F +) or high flammability (danger sign F). Can be avoided. Furthermore, it is also preferred not to have any toxic or extremely toxic (danger sign T or T +) properties.

  The boiling point of the solvent according to the present invention is preferably 110 to 210 ° C. at 760 torr. Since it cannot be completely removed in the drying or curing step, a solvent having a boiling point higher than 210 ° C. is not preferable, and the content of such a high boiling point solvent is preferably 10% or less.

  Examples of solvents that satisfy all of the above requirements include ketones having 7 carbon atoms (for example, methyl amyl ketone (2-heptanone), a viscosity of 0.77 cp at 20 ° C., a boiling point of 150 ° C. at 760 torr, a flash point of 49 ° C.), C6 carboxylic acid alkyl ester (eg n-butyl acetate, viscosity 0.73 cp at 20 ° C., boiling point 125 ° C. at 760 torr, flash point 25 ° C.), C 8 dialkyl ether (eg di-n-butyl ether, 20 Viscosity 0.70 cp at ° C, boiling point 142 ° C at 760 torr, flash point 25 ° C), C5 dialkyl carbonate (eg diethyl carbonate, viscosity 0.83 cp at 20 ° C, boiling point 126 ° C at 760 torr, flash point 33 ° C), C 5 nitrile (eg valeronitrile) A viscosity of 0.74 cp at 20 ° C., a boiling point of 141 ° C. at 760 torr, a flash point of 38 ° C., and an aromatic compound having 7 to 10 carbon atoms (for example, m-xylene, a viscosity of 0.62 cp at 20 ° C., a boiling point of 139 ° C. at 760 torr, A flash point of 25 ° C., and 1,3,5-trimethylbenzene, a viscosity of 0.95 cp at 20 ° C., a boiling point of 164 ° C. at 760 torr, and a flash point of 48 ° C.). In addition, it may contain two or more of the above functional groups, or may be combined with other functional groups (for example, diethyl ketone having 5 carbon atoms: acetylacetone (2,4-pentadione), viscosity at 20 ° C. of 0. 75 cp, 760 torr boiling point 140 ° C., flash point 38 ° C.).

  If necessary, these low-viscosity solvents can be mixed with other solvents. However, in order to keep the viscosity of the final photoresist composition at an appropriate viscosity, for example, 3 to 4 cp at 25 ° C., the content of the low-viscosity solvent contained in the mixed solvent is 10% by weight or more. , Preferably 30% by weight or more, more preferably 50% by weight or more. Most preferably, all of the solvents are the low viscosity solvents described above. Further, in the mixed solvent, the viscosity of the composition is generally 3.8 cp or less when the solvent of the photoresist composition not containing a low-viscosity solvent having a viscosity of 4.0 cp at 25 ° C. is replaced with the mixed solvent, preferably Is selected to be a mixed solvent of 3.6 cp or less. In addition, when using a mixed solvent, it is preferable that the viscosity of the solvent combined with a low-viscosity solvent is also low. Specifically, propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, and the like can be listed as solvents that can be combined with the low viscosity solvent specified in the present invention. For example, a photoresist composition can be obtained by mixing 10% by weight or more of the above-mentioned low-viscosity solvent such as acetylacetone with a commonly used propylene glycol monomethyl ether acetate (viscosity of 1.2 cp at 20 ° C.). The viscosity of the product can be reduced by 0.5 cp or more.

  The solid component contained in the photoresist composition that can be combined with the solvent according to the present invention is not particularly limited as long as it is generally used for the production of a photoresist film. The photoresist composition used for the production of a photoresist film generally contains an alkali-soluble resin, a photosensitizer, a solvent, and the like. If necessary, other additives such as a surfactant and a pigment may be contained. The components contained in the photoresist composition are arbitrarily selected according to the type of the desired photoresist film. Examples of the polymer that can be used include novolak resins, polymers having a silazane structure, acrylic polymers, silanol silicone, and polyimide. Of these, phenolic novolak resins such as phenol resins, particularly cresol novolak resins and xylenol novolak resins are preferred. The photosensitive agent used is appropriately selected according to the type of polymer to be combined and the light source used for exposure. Specific examples include naphthoquinonediazide-containing compounds, triphenylsulfonium compounds, diphenyliodonium compounds, and triazine compounds.

  The solvent for a photoresist according to the present invention is used for a photoresist composition applied by a slit coating method (sometimes called a slot coating method or a spinless coating method). When a photoresist composition is applied onto a substrate by this slit coating method, the photoresist composition is generally stored in a supply container and then applied onto the substrate via a pipe and a nozzle of an application device. The composition using the solvent for photoresist according to the present invention can apply an excellent coating film free from film peeling and coating unevenness at high speed by this slit coating method.

  The substrate on which the photoresist film is formed by slit coating using the photoresist solvent according to the present invention can then be processed by the same method as before. Generally, it is cooled to room temperature, the solvent is removed under reduced pressure or vacuum, the solvent is further removed by baking, the image is exposed in a desired pattern, developed, and the photoresist film is cured by heating. . These treatments are arbitrarily selected according to the use of the photoresist film to be produced, the type of the photoresist composition, and the like.

  Here, since the photoresist composition used in the conventional slit coating has a low solid content, the necessity for solvent removal under reduced pressure or vacuum conditions was high prior to solvent removal by baking. Furthermore, when a photoresist composition having a low solid content was used, a large amount of solvent was removed from the coating film, and the amount of change in film thickness before and after the solvent removal was large. For this reason, the uniformity of the applied film thickness is impaired, and the pattern shape to be formed tends to be a so-called T-top shape. On the other hand, when the photoresist solvent according to the present invention is used, it is possible to apply a photoresist composition having a high solid content, and therefore the removal of the solvent under reduced pressure or vacuum conditions may be omitted. This makes it possible to simplify the process and reduce costs. Furthermore, in order to increase the solids content of the photoresist composition, that is, to reduce the solvent content, the film thickness at the time of coating can be reduced, thereby improving the uniformity of the film thickness after drying. Further, a bad pattern shape such as T-top can be prevented. The effect obtained by reducing the film thickness at the time of application is particularly prominent when the solid content is 17.5% by weight or more.

The photoresist film or the photoresist substrate manufactured by such a method can be used for manufacturing various electronic components. In the photoresist film, since the uniformity of the film surface is particularly important, the coating method of the present invention is advantageous for producing an electronic component having excellent performance, for example, a semiconductor element. Further , it can be particularly preferably used in fields where it is required to form a photoresist film on a relatively large substrate by slit coating or the like, for example, in the production of flat panel displays.

＊１：溶媒
ＥＬ 乳酸エチル
ＰＧＭＥ プロピレングリコールメチルエーテル
ＰＧＭＥＡ プロピレングリコールモノメチルエーテルアセテート
ＡＡ アセチルアセトン
ＢＡ 酢酸ブチル
ＤＥＣ ジエチルカーボネート
ＭＡＫ メチルアミルケトン
＊２：粘度変化は比較例３のＰＧＭＥＡに対する変化 Examples 1-4, Comparative Examples 1-3
In order to examine how the viscosity of the photoresist composition depends on the solvent, a photoresist composition was prepared by changing the solvent while keeping the solid component constant, and the viscosity was measured with a Ubbelohde viscometer. The sample was esterified with a 60:40 weight ratio of m-cresol / p-cresol novolak resin (average molecular weight 8,500 g / mol) and a photosensitizer (partially 2,1-diazonaphthoquinone-5-sulfonyl chloride). 2,3,4-trihydroxybenzophenone) was dissolved in the solvent or mixed solvent shown in Table 1. Further, 0.5% by weight of a fluorosurfactant was added as a wetting agent based on the solid content of the photoresist composition.

* 1: Solvent EL Ethyl lactate PGMEA Propylene glycol methyl ether PGMEA Propylene glycol monomethyl ether acetate AA Acetylacetone BA Butyl acetate DEC Diethyl carbonate MAK Methyl amyl ketone * 2: Viscosity change relative to PGMEA in Comparative Example 3

From the results in Table 1, it can be seen that the solvent according to the present invention has a very low viscosity as compared with the solvent (PGMEA) that is usually used.

Comparative Example 4, Examples 5-9
A photoresist composition comprising m-cresol / p-cresol novolak resin (molecular weight 5,800 g / mol) and 10 mol% phenolic monomer esterified with 2,1-diazonaphthoquinone-5-sulfonyl chloride, Prepared using the solvents shown in Table 2. Further, 0.5% by weight of a fluorosurfactant was added as a wetting agent based on the solid content of the photoresist composition. The solids content of all samples was 16.4% by weight. The viscosity was measured with a Ubbelohde viscometer.

＊１：溶媒
ＰＧＭＥＡ プロピレングリコールモノメチルエーテルアセテート
ＡＡ アセチルアセトン
ＢＡ 酢酸ブチル
ＭＡＫ メチルアミルケトン
ＤＥＣ ジエチルカーボネート
ＤＩＢＫ ジイソブチルケトン
＊２：粘度変化は比較例４のＰＧＭＥＡに対する変化

* 1: Solvent PGMEA Propylene glycol monomethyl ether acetate AA Acetylacetone BA Butyl acetate MAK Methyl amyl ketone DEC Diethyl carbonate DIBK Diisobutyl ketone * 2: Viscosity change relative to PGMEA in Comparative Example 4

  From the results in Table 1, it can be seen that the solvent according to the present invention has a very low viscosity as compared with the solvent (PGMEA) that is usually used.

Comparative Examples 5-9, Examples 10-14
In order to show how the solids content of a photoresist composition affects viscosity, a photoresist composition using propylene glycol monomethyl ether acetate (PGMEA) or acetylacetone (AA) was prepared and a Ubbelohde viscometer The viscosity was measured at The sample was esterified with a 60:40 weight ratio of m-cresol / p-cresol novolak resin (average molecular weight 8,500 g / mol) and a photosensitizer (partially 2,1-diazonaphthoquinone-5-sulfonyl chloride). 2,3,4-trihydroxybenzophenone) was dissolved in the solvents or mixed solvents shown in Table 3. Further, 0.5% by weight of a fluorosurfactant was added as a wetting agent based on the solid content of the photoresist composition.

＊１：溶媒
ＰＧＭＥＡ プロピレングリコールモノメチルエーテルアセテート
ＡＡ アセチルアセトン

* 1: Solvent PGMEA Propylene glycol monomethyl ether acetate AA Acetylacetone

  From the results in Table 3, it can be seen that the photoresist composition using the solvent according to the present invention has a very low viscosity as compared with a composition containing PGMEA which has been generally used conventionally.

Measurement of Composition Viscosity Change in Mixed Solvents Mixed solvents in which the blending ratio of propylene glycol monomethyl ether acetate and acetylacetone was changed were prepared, and the solid content was 15.0% by weight or 17. A constant photoresist composition was prepared at 0 wt%. The viscosity change of the obtained composition was as shown in FIG. As can be seen from this figure, when a mixed solvent containing 10% acetylacetone with respect to propylene glycol monomethyl ether acetate is used, the viscosity of the composition is 0.5 cp compared to the case where only propylene glycol monomethyl ether acetate is used. This can be lowered. When the viscosity of the composition is lowered by 0.3 cp, the maximum application speed in slit coating can be increased by 20 to 30 mm / s.

Coating Tests To examine how the maximum speed in slit coating depends on the combination of solids content and solvent in the photoresist composition, some of the above compositions were applied with slit coating. The coating was performed on a 1300 mm × 1100 mm substrate using a TS slit nozzle coater manufactured by Toray Engineering Co., Ltd. The nozzle speed was increased by 10 mm / s until a void was generated, and the maximum coating speed was measured. The coating amount was calculated so that the film thickness after the removal of 95 to 99% of the solvent would be 1.5 to 1.6 μm. The obtained results were as shown in Table 4.

  From the results in Table 4, it can be seen that the solvent of the present invention can achieve a higher maximum coating speed. That is, Examples 1 and 4 for Comparative Example 3 and Examples 6 and 7 for Comparative Example 4 have the same highest solid content, respectively, and the photoresist composition using the solvent according to the present invention has a higher maximum. Application speed is achieved. Further, comparing Comparative Examples 5 and 7 with Examples 11 and 13, it can be seen that with the solvent according to the present invention, the viscosity of the photoresist composition can be lowered even with a higher solid content.

In the above example, the coating experiment and the viscosity measurement were performed at 25 ° C., and the viscosity at 20 ° C. of a pure solvent was measured as follows (unit cp).
EL ethyl lactate 2.8
PGME Propylene glycol methyl ether 1.8
PGMEA Propylene glycol monomethyl ether acetate 1.2
AA Acetylacetone 0.75
BA Butyl acetate 0.73
MAK Methyl amyl ketone 0.77
DEC Diethyl carbonate 0.83
DIBK diisobutyl ketone 1.05

The graph which shows the viscosity change of the photoresist composition using the mixed solvent of propylene glycol monomethyl ether acetate and acetylacetone.

Claims (7)

  A photoresist solvent used in a photoresist composition applied onto a substrate by a slit coating method, wherein the viscosity is 10 wt% or more based on the weight of the solvent, and the viscosity at 20 ° C. is 1.1 cp or less. A solvent for photoresist, which is a solvent.   The photoresist of claim 1 wherein the low viscosity solvent comprises in its structure a carbonyl group, a carboxylic ester group, a carbonate group, a cyano group, or an ether linkage, or an aromatic unit, or a combination thereof. Solvent.   The solvent for a photoresist according to claim 1 or 2, wherein a flash point of the low-viscosity solvent exceeds 21 ° C and / or a boiling point at 760 Torr is 110 to 210 ° C.   The solvent for photoresists according to any one of claims 1 to 3, wherein the low-viscosity solvent has no toxicity.   The solvent for photoresists according to claim 1, further comprising propylene glycol monomethyl ether acetate.   A photoresist composition for slit coating, comprising the photoresist solvent according to any one of claims 1 to 5, an alkali-soluble resin, and a photosensitive substance.   The photoresist composition for slit coating according to claim 6, which is used for producing a flat panel display.

Images