Claims
- 1. A nanoporous silica precursor composition which comprises at least one alkoxysilane; at least one relatively low volatility solvent composition comprising an ether of a C.sub.1 to C.sub.4 alkylene glycol which is miscible in water and alkoxysilanes, having a hydroxyl concentration of 0.021 mole/cm.sup.3 or less, a boiling point of about 175.degree. C. or more at atmospheric pressure and a weight average molecular weight of about 100 or more; at least one relatively high volatility solvent composition having a boiling point below that of the relatively low volatility solvent composition; optional water and an optional catalytic amount of an acid.
- 2. The composition of claim 1 which comprises water.
- 3. The composition of claim 1 which comprises a catalytic amount of an acid.
- 4. The composition of claim 1 which comprises both water and a catalytic amount of an acid.
- 5. The composition of claim 1 which is absent of water and absent of an acid catalyst.
- 6. The composition of claim 1 wherein the alkoxysilane comprises one or more components selected from the group consisting of alkoxysilanes having the formula: ##STR2## wherein at least 2 of the R groups are independently C.sub.1 to C.sub.4 alkQxy groups and the balance, if any, are independently selected from the group consisting of hydrogen, alkyl, phenyl, and halogen.
- 7. The composition of claim 6 wherein each R is methoxy, ethoxy or propoxy.
- 8. The composition of claim 1 wherein the alkoxysilane comprises one or more components selected from the group consisting of tetraethoxysilane and tetramethoxysilane.
- 9. The composition of claim 1 wherein the relatively high volatility solvent composition has a boiling point of about 120.degree. C. or less.
- 10. The composition of claim 1 wherein the relatively high volatility solvent composition comprises one or more components selected form the group consisting of methanol, ethanol, n-propanol, isopropanol, n-butanol and mixtures thereof.
- 11. The composition of claim 1 wherein the relatively low volatility solvent composition comprises di(ethylene)glycol, tri(ethylene)glycol, tetra(ethylene)glycol; penta(ethylene)glycol, di(propylene)glycol, hexa(ethylene)glycol or mixtures thereof.
- 12. The composition of claim 1 wherein the precursor composition has no more than about 250 parts per billion of trace metal impurities.
- 13. A process for forming a nanoporous dielectric coating on a substrate which comprises
- a) blending a nanoporous silica precursor composition comprising at least one alkoxysilane; at least one relatively low volatility solvent composition comprising an ether of a C.sub.1 to C.sub.4 alkylene glycol which is misciblc in water and alkoxysilanes, having a hydroxyl concentration of 0.021 mole/cm.sup.3 or less, a boiling point of about 175.degree. C. or more at atmospheric pressure and a weight average molecular weight of about 100 or more; at least one relatively high volatility solvent composition having a boiling point below that of the relatively low volatility solvent composition; optional water and an optional catalytic amount of an acid, thus forming a mixture and causing a partial hydrolysis and partial condensation of the alkoxysilane;
- b) depositing the composition onto a substrate while evaporating at least a portion of the relatively high volatility solvent composition;
- c) exposing the composition to a water vapor and a base vapor; and
- d) evaporating the relatively low volatility solvent composition, thereby forming a silicon containing polymer composition on the substrate, wherein the silicon containing polymer composition has a dielectric constant of from about 1.3 to about 3.5. and a density in the range of from about 0.25 to about 1.9 g/cm.sup.3.
- 14. The process of claim 13 wherein step (a) comprises blending water in the composition.
- 15. The process of claim 13 wherein step (a) further comprises blending a catalytic amount of an acid in the composition.
- 16. The process of claim 13 wherein the alkoxysilane comprises one or more components selected from the group consisting of alkoxysilanes having the formula: ##STR3## wherein at least 2 of the R groups are independently C.sub.1 to C.sub.4 alkoxy groups and the balance, if any, are independently selected from the group consisting of hydrogen, allyl, phenyl, and halogen.
- 17. The process of claim 16 wherein each R is methoxy, ethoxy or propoxy.
- 18. The process of claim 13 wherein the alkoxysilane comprises one or more components selected from the group consisting of tetraethoxysilane and tetramethoxysilane.
- 19. The process of claim 13 wherein the relatively high volatility solvent composition has a boiling point of about 120.degree. C. or less.
- 20. The process of claim 13 wherein the relatively high volatility solvent composition comprises one or more components selected form the group consisting of methanol, ethanol, n-propanol, isopropanol, n-butanol and mixtures thereof.
- 21. The process of claim 13 wherein the relatively low volatility solvent composition comprises di(ethylene)glycol, tri(ethylene)glycol, tetra(ethylene)glycol; penta(ethylene)glycol, di(propylene)glycol, hexa(ethylene)glycol or mixtures thereof.
- 22. The process of claim 13 wherein the base vapor comprises one or more components selected from the group consisting of ammonia, amines and mixtures thereof.
- 23. The process of claim 13 wherein the mole ratio of water vapor to base vapor ranges from about 1:3 to about 1:100.
- 24. The process of claim 13 wherein the base vapor has a pKb of from about less than 0 to about 9.
- 25. The process of claim 13 wherein the substrate comprises raised pattern of lines comprising a metal, silica, silicon nitride, titanium nitride, tantalum nitride or silicon oxynitride.
- 26. The process of claim 13 wherein the substrate comprises a semiconductor material.
- 27. The process of claim 13 wherein the substrate comprises silicon or gallium arsenide.
- 28. The process of claim 13 wherein the mole ratio of water vapor to base vapor ranges from about 1:3 to about 1:100.
- 29. The process of claim 13 wherein the precursor composition has no more than about 250 parts per billion of trace metal impurities.
CROSS REFERENCE TO RELATED APPLICATION
This application claims the benefit of provisional application 60/063,816 filed Oct. 31, 1997 which is incorporated herein by reference.
Foreign Referenced Citations (3)
Number |
Date |
Country |
0459003 |
Dec 1991 |
EPX |
0775669 |
May 1997 |
EPX |
0776925 A2 |
Jun 1997 |
EPX |