Patent ID: 6162488
Filing Date: 2000-12-19
Classification: C23C

Abstract:
A method for controlling the application of a surface coating to a substrate by chemical deposition from a gaseous phase, in a reaction chamber containing the gaseous phase, the method comprising the steps of:comparing a measure of growth rate of the surface coating to a preselected setpoint for desired growth rate of the surface coating to determine a growth rate error signal;determining a primary corrective input signal from the growth rate error signal wherein the selected primary corrective input signal is selected from the group consisting of (i) mass flow rate into the reaction chamber of a component in the gaseous phase (ii) total mass flow rate into the reaction chamber, (iii) total pressure in the reaction chamber, (iv) heating power input into the reaction chamber, (v) intensity of radiation input into the reaction chamber, (vi) and energy level of radiation input into the reaction chamber, wherein the selected primary corrective input signal has the largest ratio of gain-to-time constant in the group for change in growth rate of the surface coating in response to change in the input parameter; andadjusting the deposition process based on the selected primary corrective input signal to reduce the magnitude of the growth rate error signal.