Patent ID: 7435447

Claim:
A method of treating a substrate comprising: placing said substrate in a high pressure processing chamber of a high pressure processing system onto a platen configured to support said substrate; forming a supercritical fluid from a fluid by adjusting a pressure of said fluid above the critical pressure of said fluid, and adjusting a temperature of said fluid above the critical temperature of said fluid; introducing said supercritical fluid to said high pressure processing chamber; introducing a process chemistry to said supercritical fluid; flowing said supercritical fluid and said process chemistry over said substrate; measuring a flow condition that varies with the concentration of said process chemistry in said supercritical fluid flowing past a flow condition measurement device; determining a flow rate of said supercritical fluid and process chemistry through said system from a variation of said measured flow condition; and recirculating said supercritical fluid through said high pressure processing chamber; said determining said flow rate comprising determining a volume of said supercritical fluid circulating through said high pressure processing system, and dividing said volume by a difference in time between a first variation in a signal from said flow condition measurement device as said process chemistry in said supercritical fluid passes said flow condition measurement device a first time and a second variation in said signal from said flow condition measurement device as said process chemistry in said supercritical fluid passes said flow condition measurement device a second time.