Method for closed loop control of chemical vapor deposition process

Claim 1

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; and adjusting the deposition process based on the selected primary corrective input signal to reduce the magnitude of the growth rate error signal.

Claim 2

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; and adjusting the deposition process based on the selected primary corrective input signal to reduce the magnitude of the growth rate error signal.

Claim 9

A method of 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 measurement 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; comparing a measure of temperature of the surface coating to a preselected setpoint for temperature of the surface coating to determine a surface temperature error signal; determining a first corrective input signal and a second corrective input signal from both the growth rate error signal and the surface temperature error signal; and adjusting a first input parameter based on the first corrective input signal, and adjusting a second input parameter based on the second corrective input signal, the first input parameter and the second input parameter each being 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 second input parameter is different from the first input parameter, and first input parameter 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.

Claim 10

A method of 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 measurement 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; comparing a measure of temperature of the surface coating to a preselected setpoint for temperature of the surface coating to determine a surface temperature error signal; determining a first corrective input signal and a second corrective input signal from both the growth rate error signal and the surface temperature error signal; and adjusting a first input parameter based on the first corrective input signal, and adjusting a second input parameter based on the second corrective input signal, the first input parameter and the second input parameter each being 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 second input parameter is different from the first input parameter, and first input parameter 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.

Claim 15

A method for applying a surface coating to a substrate by chemical deposition from a gaseous phase, in a reaction chamber containing the gaseous phase, the method comprising controlling the chemical deposition by: comparing a measurement 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; and adjusting a primary input parameter based on the primary corrective input signal, the primary input parameter being selected from the group consisting of mass flow rate into the reaction chamber of a component in the gaseous phase, total mass flow rate into the reaction chamber, total pressure in the reaction chamber, heating power input into the reaction chamber, intensity of radiation input into the reaction chamber, and energy level of radiation input into the reaction chamber, wherein thickness of the coating is monitored and, responsive to change in thickness of the coating, coating composition is changed by adjusting one or more parameters selected from the group consisting of mass flow rate into the reaction chamber of a component in the gaseous phase, total mass flow rate into the reaction chamber, total pressure in the reaction chamber, heating power input into the reaction chamber, intensity of radiation input into the reaction chamber, and energy level of radiation input into the reaction chamber.

Claim 16

A method for applying a surface coating to a substrate by chemical deposition from a gaseous phase, in a reaction chamber containing the gaseous phase, the method comprising controlling the chemical deposition by: comparing a measurement 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; and adjusting a primary input parameter based on the primary corrective input signal, the primary input parameter being selected from the group consisting of mass flow rate into the reaction chamber of a component in the gaseous phase, total mass flow rate into the reaction chamber, total pressure in the reaction chamber, heating power input into the reaction chamber, intensity of radiation input into the reaction chamber, and energy level of radiation input into the reaction chamber, wherein thickness of the coating is monitored and, responsive to change in thickness of the coating, coating composition is changed by adjusting one or more parameters selected from the group consisting of mass flow rate into the reaction chamber of a component in the gaseous phase, total mass flow rate into the reaction chamber, total pressure in the reaction chamber, heating power input into the reaction chamber, intensity of radiation input into the reaction chamber, and energy level of radiation input into the reaction chamber.