From ingot, substrate to epitaxy, each process are monitored.
The measurement operation (for epi wafers) includes inspection wafer measurement and production wafer measurement. For the inspection wafer, we mainly tests the stability of the equipment, or to adjust wafer structure, quality inspection shall be conducted every day or batch;The surface particle, wavelength, resistance, carrier mobility and Hall are measured, after that, carry out the visual inspection under the microscope, and then we packed them under 100 clean room.