Precise measurements are required in the photolithography portion of processing wafers. During the numerous times when a given wafer is in a photolithography tool for subsequent layers of the circuit to be patterned, a change in temperature of more than +/- 1 degree will cause alignment defects that could significantly reduce the yield on the wafer.
The high-power lamp used in the photolithography process generates a lot of heat inside the tool. This heat must be monitored and balanced with the right amount of cooling air to keep the tool interior and wafers at a constant temperature. The PDT-440 thermistor transmitter, or the PDT-444 high accuracy 4-wire transmitter can be used in conjunction with a high-stability, fast-response thermistor to monitor and control these air flows. With the PDT-444, control to +/- 0.01C is possible.