Sensor cell for measuring the concentration of a component in a two-component liquid mixture, method, apparatus and etching system

摘要

A sensor cell measures a component of a two-component liquid mixture. A control apparatus controls a concentration of the component in the mixture. The control apparatus can be applied to an etching system for etching a silicon nitride layer. The sensor cell contains a sample inlet for feeding the mixture, a sample drain, a vapor outlet, an apparatus for setting a temperature of the liquid mixture to a temperature below the boiling point, a heating element for elevating the temperature of the liquid mixture to a temperature above the boiling point, and a device for calculating the concentration of the component based on a temperature of the liquid versus temperature of the heating element characteristics. The concentration of the component can be assessed by determining a point at which a slope of the temperature of the liquid versus temperature of the heating element characteristics is changed.