Control of Wafer Temperature Using a Vortex Water-Wall Argon Arc

This paper describes a constant switching frequency variable duty cycle control strategy that adjusts the current in a vortex water-wall argon arc lamp to achieve wafer temperature tracking in response to a temperature ramp request. The control system includes a model for the following: 1) the outer loop temperature controller; 2) the inner loop current controller; 3) the wafer temperature; and 4) the irradiation produced by the arc lamp in response to arc current changes. The controller design is able to provide a well-behaved arc current and good temperature tracking performance that accommodates for no temperature feedback below 300 °C and a bumpless transfer once temperature feedback is available.