Patent ID: 8426288

Claim:
A method for improving capacitance uniformity in a MIM device, for the purpose of improving uniformity of a thin film within the MIM device, comprising: step S 1 : loading a wafer into a reaction chamber, introducing into the reaction chamber a gas mixture comprising silane and ammonia for producing the thin film, and maintaining the pressure value in the reaction chamber at this time for a period of time to stablize the reaction chamber; step S 2 : introducing said gas mixture into the reaction chamber at different fluxes, introducing nitrogen into the reaction chamber, and maintaining the pressure value in the reaction chamber at this time to be stablized for a period of time; step S 3 : turning on a RF generator to start a discharge to ionize or decompose the reaction gas in said gas mixture, so that a thin film of silicon nitride is formed on the surface of wafer by chemical vapor deposition; step S 4 : turning off the RF generator, stopping the introduction of the gas mixture into the reaction chamber, introducing argon and nitrogen into the reaction chamber at the same time, changing the pressure value in the reaction chamber at this time, and maintaining the pressure value in the reaction chamber at this time to be stablized for a period of time to remove silane and ammonia remaining in the reaction chamber; step S 5 : continuing to introduce argon and nitrogen into the reaction chamber, keeping the pressure value in the reaction chamber constant, and turning on the RF generator for passivating the deposited thin film of silicon nitride so that it has a stable chemical property; step S 6 : continuing to introduce argon and nitrogen into the reaction chamber, and keeping the pressure value in the reaction chamber constant, to remove silane and ammonia remaining in the reaction chamber; step S 7 : moving the wafer away from the position corresponding to a showerhead for gas sources, stopping introducing argon, continuing to introduce nitrogen into the reaction chamber, keeping the pressure value in the reaction chamber constant, and maintaining this state for a period of time; and step S 8 : vacuating the reaction chamber with a vacuum pump, so that the by-products in the depositing reaction are pumped out along with the mainstream gases.