ENDPOINT DETERMINATION OF ALUMINUM REACTIVE ION ETCHING BY DISCHARGE IMPEDANCE MONITORING

In reactive ion etching, it is found that CCl//4 discharge impedance is reduced during aluminum etching and changes markedly at the final aluminum interface. This phenomenon was monitored by measuring the target electrode voltage with a 2-in. aluminium-coated Si wafer. This measurement is compared with the 261. 6-nm Al-Cl optical emission spectrum and verified with SEM photographs of the etched wafer. As a result the end points detected by these two methods are consistent with each other and discharge impedance monitoring is applicable as an in-process monitoring method.