Coating liquid for formation of protective film for semiconductor processing and method for preparation of the same

1. A coating liquid for formation of a protective film for semiconductor processing having a Young's modulus of at least 8 GPa and a specific dielectric constant in a range from 2.7 to 3.0, the coating liquid consisting essentially of:

(a) a silicon compound obtained by hydrolyzing tetraalkyl orthosilicate (TAOS) and alkoxysilane (AS) expressed by the following general formula (I) in the presence of tetramethyl ammonium hydroxide (TMAOH), optionally, tetrapropyl ammonium hydroxide (TPAOH), and water, wherein TMAOH functions as a catalyst for the hydrolysis reaction and as a template material for the protective film,

X n Si(OR) 4-n   (I)

,wherein

X denotes a hydrogen atom, a fluorine atom, an alkyl group having 1 to 8 carbon atoms, a fluorine-substituted alkyl group, an aryl group, or a vinyl group, and

R denotes a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group, or a vinyl group, and n is an integer from 1 to 3;

(b) an organic solvent including propylene glycol monomethyl ether (PGME); and

(c) water, wherein the water comprises 35% to 65% by weight of the liquid composition.

2. The coating liquid for formation of a protective film for semiconductor processing according to claim 1 , wherein the silicon compound is obtained by:

(i) hydrolyzing or partially hydrolyzing tetraalkyl orthosilicate (TAOS) in the presence of tetramethyl ammonium hydroxide (TMAOH) and water;

(ii) mixing the hydrolyzed or partially hydrolyzed product with alkoxysilane (AS) expressed by the general formula (I), or a hydrolyzed or partially hydrolyzed product thereof; and

(iii) hydrolyzing all or a portion of the mixture containing the reaction product of step (i) and the alkoxysilane (AS).

3. The coating liquid for formation of a protective film for semiconductor processing according to claim 1 , wherein the tetraalkyl orthosilicate (TAOS) is selected from the group consisting of tetraethyl orthosilicate (TEOS), tetramethyl orthosilicate (TMOS), and a mixture thereof.

4. The coating liquid for formation of a protective film for semiconductor processing according to claim 1 , wherein the alkoxysilane (AS) is selected from the group consisting of methyl trimethoxysilane (MTMS), methyl triethoxysilane (MTES), and a mixture thereof.

5. The coating liquid for formation of a protective film for semiconductor processing according to claim 1 , wherein the silicon compound is obtained by hydrolyzing the tetraalkyl orthosilicate (TAOS) and the alkoxysilane (AS) in the presence of tetrapropyl ammonium hydroxide (TPAOH), in addition to tetramethyl ammonium hydroxide (TMAOH) and water.

6. The coating liquid for formation of a protective film for semiconductor processing according to claim 1 , wherein number average molecular weight of the silicon compound is in a range from 10000 to 100000 in terms of polyethylene oxide.

7. The coating liquid for formation of a protective film for semiconductor processing according to claim 1 , wherein content of the silicon compound is in a range from 0.1 to 10% by weight of the liquid composition.

8. A method of preparing a coating liquid for formation of a protective film for semiconductor processing having a Young's modulus of at least 8 GPa and a specific dielectric constant in a range from 2.7 to 3.0, the method of preparation consisting essentially of:

(a) preparing a liquid composition containing a silicon compound obtained by hydrolyzing tetraalkyl orthosilicate (TAOS) and alkoxysilane (AS) expressed by the following general formula (I), which are contained in an organic solvent, tetramethyl ammonium hydroxide (TMAOH) and, optionally, tetrapropyl ammonium hydroxide (TPAOH), and water,

X n Si(OR) 4-n   (I)

,wherein

X denotes a hydrogen atom, a fluorine atom, an alkyl group having 1 to 8 carbon atoms, a fluorine-substituted alkyl group, an aryl group, or a vinyl group, and

R denotes a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group, or a vinyl group; and n is an integer from 1 to 3;

(b) substituting at least a portion of an organic solvent contained in the liquid composition obtained in step (a) with propylene glycol monomethyl ether (PGME); and

(c) adjusting quantity of the silicon compound contained in the liquid composition obtained in step (b), dependent upon a type or an application of a protective film for semiconductor processing to be formed, and adjusting water content of the liquid composition to a range from 35% to 65% by weight of the liquid composition.

9. The method of preparing a coating liquid for formation of a protective film for semiconductor processing according to claim 8 , wherein the silicon compound is obtained by

(i) hydrolyzing or partially hydrolyzing tetraalkyl orthosilicate (TAOS) which is contained in an organic solvent in the presence of tetramethyl ammonium hydroxide (TMAOH) and water:

(ii) mixing the hydrolyzed or partially hydrolyzed product with alkoxysilane (AS) expressed by the general formula (I), or a hydrolyzed or partially hydrolyzed product thereof, which is contained in an organic solvent; and

(iii) hydrolyzing all or a portion of the mixture containing the reaction product of step (i) and the alkoxysilane (AS).

10. The method of preparing a coating liquid for formation of a protective film for semiconductor processing according to claim 8 , wherein the organic solvent used in step (a) is an alcohol.

11. The method of preparing a coating liquid for formation of a protective film for semiconductor processing according to claim 8 , wherein the tetraalkyl orthosilicate (TAOS) used in step (a) is selected from the group consisting of tetraethyl orthosilicate (TEOS), tetramethyl orthosilicate (TMOS), and a mixture thereof.

12. The method of preparing a coating liquid for formation of a protective film for semiconductor processing according to claim 8 , wherein the alkoxysilane (AS) used in step (a) is selected from the group consisting of methyl trimethoxy silane (MTMS), methyl triethoxy silane (MTES), and a mixture thereof.

13. The method of preparing a coating liquid for formation of a protective film for semiconductor processing according to claim 8 , wherein the liquid composition prepared in step (a) includes a silicon compound obtained by hydrolyzing the tetraalkyl orthosilicate (TAOS) and the alkoxysilane (AS) in the presence of tetrapropyl ammonium hydroxide (TPAOH), in addition to tetramethyl ammonium hydroxide (TMAOH) and water.

14. The method of preparing a coating liquid for formation of a protective film for semiconductor processing according to claim 8 , including substituting the solvent in step (b) using a rotary evaporator.

15. The coating liquid for formation of a protective film for semiconductor processing according to claim 1 , wherein the silicon compound is obtained by hydrolyzing tetraalkyl orthosilicate (TAOS) and alkoxysilane (AS) with a molar ratio of TAOS:AS in a range from 6:4 to 2:8, in terms of SiO 2 , and a molar ratio of (TMAOH):(TAOS+AS) or (TMAOH+TPAOH):(TAOS+AS) in a range from 1:10 to 7:10, in terms of SiO 2 .

16. The method of preparing a coating liquid for formation of a protective film for semiconductor processing according to claim 8 , wherein the silicon compound is obtained by hydrolyzing tetraalkyl orthosilicate (TAOS) and alkoxysilane (AS) with a molar ratio of TAOS:AS in a range from 6:4 to 2:8, in terms of SiO 2 , and a molar ratio of (TMAOH):(TAOS+AS) or (TMAOH+TPAOH):(TAOS+AS) in a range from 1:10 to 7:10, in terms of SiO 2 .