Gas diffusion shower head design for large area plasma enhanced chemical vapor deposition

A method of depositing a thin film on a substrate, comprising:

• placing a substrate in a process chamber coupled to a silicon source, the process chamber having 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 second coaxial cylindrical shape with a smaller diameter than the first cylindrical shape for a portion of its length extending downstream of the first cylindrical shape, a first coaxial conical shape extending downstream from the second coaxial cylindrical shape, and a second coaxial conical shape extending downstream from the first coaxial conical shape to the downstream side of the diffuser plate, with the upstream end of the first coaxial conical shape having substantially the same diameter as the second coaxial cylindrical shape and the downstream end of the second coaxial conical shape having a larger diameter than the diameter of the first cylindrical shape;
• flowing a gas through each of the gas passages;
• generating plasma between the diffuser plate and the substrate, such that a hollow cathode effect is created within the second coaxial conical shape of each of the gas passages;
• and
• depositing a thin film on the substrate in the process chamber.

A method of cleaning a process chamber, comprising:

• placing a substrate in a process chamber coupled to a remote plasma source and the remote plasma source is coupled to a fluorine source, the process chamber having a diffuser plate with 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 second coaxial cylindrical shape with a smaller diameter than the first cylindrical shape for a portion of its length extending downstream of the first cylindrical shape, a first coaxial conical shape extending downstream from the second coaxial cylindrical shape, and a second coaxial conical shape extending downstream from the first coaxial conical shape to the downstream side of the diffuser plate, with the upstream end of the first coaxial conical shape having substantially the same diameter as the second coaxial cylindrical shape and the downstream end of the second coaxial conical shape having a larger diameter than the diameter of the first cylindrical shape;
• flowing a gas through each of the gas passages;
• generating plasma between the diffuser plate and the substrate, such that a hollow cathode effect is created within the second coaxial conical shape of each of the gas passages;
• depositing a thin film on the substrate in the process chamber;
• determining if the number of processed substrates has reached a pre-determined cleaning limit;
• repeating the placing a substrate in the process chamber, flowing a gas, generating a plasma, depositing a thin film on the substrate, and determining if the number of processed substrates has reached the pre-determined cleaning limit until the number of process substrates has reached the pre-determined cleaning limit;
• and
• cleaning the process chamber when the number of processed substrates reaches the pre-determined cleaning limit.