Insulation film on semiconductor substrate and method for forming same
An insulation film is formed on a semiconductor substrate by vaporizing a silicon-containing hydrocarbon compound to provide a source gas, introducing a reaction gas composed of the source gas and an additive gas such as an inert gas and oxidizing gas to a reaction space of a plasma CVD apparatus. The residence time of the reaction gas in the reaction space is lengthened by reducing the total flow of the reaction gas in such a way as to form a siloxan polymer film with a low dielectric constant.
1. A method for forming an insulation film on a semiconductor substrate by plasma reaction, comprising the steps of:
vaporizing a silicon-containing hydrocarbon compound to provide a source gas;
introducing the source gas into a reaction space for plasma CVD processing wherein a semiconductor substrate is placed;
introducing an additive gas selected from the group consisting of an inert gas and an oxidizing gas, said oxidizing gas being used in an amount less than the source gas, said source gas and said additive gas constituting a reaction gas; and
forming an insulation film on the semiconductor substrate by activating plasma polymerization reaction in the reaction space, wherein the plasma polymerization reaction is activated while controlling the flow of the reaction gas to lengthen a residence time, Rt, of the reaction gas in the reaction space, wherein 100 msec≦Rt,
Rt[s]= 9.42×10 7 ( Pr·Ts/Ps·Tr ) r w 2 d/F
wherein:
Pr: reaction space pressure (Pa)
Ps: standard atmospheric pressure (Pa)
Tr: average temperature of the reaction gas (K)
Ts: standard temperature (K)
r w : radius of the silicon substrate (m)
d: space between the silicon substrate and the upper electrode (m)
F: total flow volume of the reaction gas (sccm).
2. The method according to claim 1 , wherein the source gas and the additive gas are separately introduced into the reaction space.
3. The method according to claim 1 , wherein the plasma polymerization reaction comprises exciting the reaction gas and depositing the film on the substrate.
4. The method according to claim 1 , wherein the reaction space comprises a space for exciting the reaction gas and a space for depositing the film.
5. The method according to claim 4 , wherein the excitation of the reaction gas comprises exciting the additive gas and contacting the excited additive gas and the source gas.
6. The method according to claim 1 , wherein the reaction space comprises a space for heating the reaction gas and a space for exciting the reaction gas and depositing the film.
7. The method according to claim 1 , wherein the excitation of the reaction gas comprises exciting the additive gas and contacting the excited additive gas and the source gas.
8. The method according to claim 1 , wherein the additive gas is selected from the group consisting of nitrogen, argon, helium, and oxygen.
9. The method according to claim 1 , wherein the plasma polymerization reaction is conducted at a temperature of 350-450° C.
10. The method according to claim 1 , wherein the residence time is determined by correlating the dielectric constant with the residence time.
11. The method according to claim 1 , wherein the flow of the reaction gas is controlled to render the relative dielectric constant of the insulation film lower than 3.10.
12. The method according to claim 1 , wherein Rt is no less than 165 msec.
13. The method according to claim 1 , wherein said silicon-containing hydrocarbon has the formula Si α O α−1 R 2α−β+2 (OC n H 2n+1 ) β wherein α is an integer of 1-3, β is an integer of 0-2, n is an integer of 1-3, and R is C 1-6 hydrocarbon attached to Si, thereby forming, as the insulation film, a siloxan polymer film having —SiR 2 O— repeating structural units.
14. The method according to claim 13 , wherein the silicon-containing hydrocarbon compound has two alkoxy groups (β=2).
15. The method according to claim 13 , wherein the alkoxy present in the silicon-containing hydrocarbon has 1 to 3 carbon atoms.
16. The method according to claim 13 , wherein the hydrocarbon present in the silicon-containing hydrocarbon compound has 1 to 6 carbon atoms (n=1-6).
17. The method according to claim 13 , wherein the silicon-containing hydrocarbon compound has 1 to 3 silicon atoms.
18. The method according to claim 13 , wherein the silicon-containing hydrocarbon compound has 1 to 2 silicon atoms (α=1 or 2).
19. The method according to claim 1 , wherein the insulation film has a dielectric constant of 2.7 or less.
20. The method according to claim 19 , wherein the insulation film has a dielectric constant of 2.4 or less.