Deposition
Plasma deposition is typically used in circumstances that require the deposition of a film where temperature sensitivity is an issue. In semiconductor processing this issue often arises due to material properties in the complex devices being fabricated.
The fundamental principles of plasma deposition are similar to plasma etching except a film is deposited rather than removed. The following basic mechanisms steps are involved.
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Formation of active gas species.
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Transport of the active species to the surface.
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Reaction at the surface.
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Pump down of the reaction products.
The two most common films deposited are silicon oxide and silicon nitride however other films such as silicon carbide and amorphous silicon are also possible. The choice of reactive gases determines the film. For silicon oxide, the gases dichlorosilane or silane combined with an appropriate oxidizer such as nitrous oxide can be used. Silicon nitride is widely deposited with silane and ammonia or nitrogen. The choice of gases, pressures, and plasma power determine the film’s properties.
The chamber configuration may be as simple as parallel plate arrangement with capacitive coupling of the RF power or may involve a configuration similar to an inductively coupled plasma. In either case, the gas delivery system plays an important role in the resulting film uniformity. |
