Patent ID: 7802538

Claim:
A system for forming a graded dielectric layer on an underlying layer, the system comprising: a showerhead comprising a blocking plate and a faceplate, wherein the showerhead is coupled to a gas supply inlet through which a process gas comprising a silicon-carbon containing gas, an oxygen containing gas and a carrier gas is introduced into the showerhead; a liquid flow meter to control a flow rate of the silicon-carbon containing gas to the showerhead; a mass flow controller to control the flow rate of the carrier gas; and a controller comprising: a memory storing information indicative of instructions that when performed result in operations comprising: flowing the silicon-carbon containing gas at an initial flow rate during the formation of an oxygen rich portion of the graded dielectric layer, then increasing the silicon-carbon containing gas flow rate from the initial flow rate to an intermediate flow rate, and maintaining the intermediate flow rate for about 0.5 seconds or longer, and then further increasing the silicon-carbon containing gas flow rate from the intermediate flow rate 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.