Method to deposit functionally graded dielectric films via chemical vapor deposition using viscous precursors
A method of forming a graded dielectric layer on an underlying layer including flowing a mixture of a silicon-carbon containing gas, an oxygen containing gas and a carrier gas through a showerhead comprising a blocking plate and a faceplate to form an oxide rich portion of the graded dielectric layer, where the silicon-carbon containing gas has an initial flow rate, flowing the silicon-carbon containing gas at a first intermediate flow rate for about 0.5 seconds or longer, where the first intermediate flow rate is higher than the initial flow rate, and flowing the silicon-carbon containing gas at a fastest flow rate higher than the first intermediate flow rate to form a carbon rich portion of the graded dielectric layer.
1. A method of forming a graded dielectric layer on an underlying layer, the method comprising:
flowing a mixture of a silicon-carbon containing gas, an oxygen containing gas and a carrier gas through a showerhead comprising a blocking plate and a faceplate to form an oxide rich portion of the graded dielectric layer, wherein the silicon-carbon containing gas has an initial flow rate;
flowing the silicon-carbon containing gas at a first intermediate flow rate for about 0.5 seconds or longer, wherein the first intermediate flow rate is higher than the initial flow rate; and
flowing the silicon-carbon containing gas at a fastest flow rate higher than the first intermediate flow rate to form a carbon rich portion of the graded dielectric layer, wherein the carrier gas has a carrier gas flow rate that stays constant unit after the silicon-carbon containing gas reaches the fastest flow rate.
2. The method of claim 1 , wherein the silicon-carbon containing gas is a liquid at room temperature.
3. The method of claim 1 , wherein the silicon-carbon containing gas is octamethylcyclotetrasiloxane (OMCTS).
4. The method of claim 1 , wherein the oxygen containing gas comprises oxygen (O 2 ).
5. The method of claim 1 , wherein the carrier gas comprises helium (He).
6. The method of claim 1 , wherein the underlying layer is a carbon-containing diffusion barrier layer.
7. The method of claim 6 , wherein the carbon-containing diffusion barrier layer comprises silicon oxycarbide (SiOCH).
8. The method of claim 1 , wherein the oxide rich portion of the graded dielectric layer has a thickness of about 70Å to about 80Å.
9. The method of claim 1 , wherein the silicon-carbon containing gas increases from the initial flow rate to the first intermediate flow rate at about 600 milligrams/sec or less.
10. The method of claim 1 , wherein the method comprises flowing the silicon-carbon containing gas at a second intermediate flow rate for about 0.5 seconds or longer, wherein the second intermediate flow rate is higher than the first intermediate flow rate.
11. The method of claim 1 , wherein a flow rate for the oxygen containing gas decreases when the silicon-carbon containing gas goes from the initial flow rate to the first intermediate flow rate.
12. A method of forming a graded dielectric layer on an underlying layer, the method comprising:
flowing a mixture of a silicon-carbon containing gas, an oxygen containing gas and a carrier gas through a showerhead comprising a blocking plate and a faceplate to form an oxide rich portion of the graded dielectric layer, wherein the silicon-carbon containing gas has an initial flow rate; and
increasing the silicon-carbon containing gas to a fastest flow rate to form a carbon rich portion of the graded dielectric layer, wherein the carrier gas has a carrier gas flow rate that stays constant until after the silicon-carbon containing gas reaches the fastest flow rate.
13. The method of claim 12 , wherein the silicon-carbon containing gas is octamethylcyclotetrasiloxane (OMCTS).
14. The method of claim 12 , wherein the carrier gas comprises helium (He).
15. The method of claim 12 , wherein the oxygen containing gas is oxygen (O 2 ).
16. The method of claim 12 , wherein the carrier gas flow rate decreases by about 50% or more after the silicon-carbon containing gas reaches the fastest flow rate.
17. The method of claim 12 , wherein the initial flow rate of the silicon-carbon containing gas is about 500 mgm and the fastest flow rate is about 3000 mgm.
18. The method of claim 17 , wherein the carrier gas flow rate decreases from about 5000 sccm to about 1000 sccm after the silicon-carbon containing gas reaches the fastest flow rate.
19. A method of forming a graded dielectric layer on an underlying layer, the method comprising:
flowing a mixture of a silicon-carbon containing gas, an oxygen containing gas and a carrier gas through a showerhead comprising a blocking plate and a faceplate to form an oxide rich portion of the graded dielectric layer, wherein the silicon-carbon containing gas has an initial flow rate; and
increasing the silicon-carbon gas to a fastest flow rate to form a carbon rich portion of the graded dielectric layer, wherein the carrier gas has a carrier gas flow rate that stays constant until after the silicon-carbon containing gas reaches the fastest flow rate, and wherein the carrier gas flow rate decreases by about 50% or more after the silicon-carbon containing gas reaches the fastest flow rate.
20. The method of claim 19 , wherein the carrier gas flow rate decreases from about 5000 sccm to about 1000 sccm after the silicon-carbon containing gas reaches the fastest flow rate.
21. The method of claim 19 , wherein the silicon-carbon containing gas comprises octamethylcyclotetrasiloxane (OMCTS).
22. The method of claim 19 , wherein the oxygen containing gas comprises oxygen (O 2 ) and the carrier gas comprises helium (He).