Patent ID: 8795793

Claim:
A method of depositing a thin film on a substrate, comprising: placing a substrate in a process chamber with a diffuser plate having an upstream side, a downstream side, and a plurality of gas passages passing between the upstream and downstream sides, wherein each of the gas passages has a first cylindrical shape for a portion of its length extending from the upstream side, a first coaxial conical shape for a portion of its length extending from the downstream side, a second coaxial cylindrical shape with a smaller diameter than the first cylindrical shape disposed between the first cylindrical shape and the first coaxial conical shape, and a second coaxial conical shape connecting the second coaxial cylindrical shape with the first coaxial conical shape, wherein the first coaxial conical shape has a larger diameter at the downstream side than the diameter of the first cylindrical shape at the upstream side; flowing a gas through the plurality of gas passages; generating plasma between the diffuser plate and the substrate, such that a hollow cathode effect is created within the first coaxial conical shape of the gas passages; and depositing a thin film on the substrate in the process chamber.