Integration of in situ spectral ellipsometry with MMST machine control

The transformation of desired physical effects to process settings has been achieved through extensive use of appropriate in situ sensors for the MMST program. In situ sensors like an ellipsometer can be used to monitor film thicknesses as well as etch or growth rate in real time, and to determine endpoint time. This capability is opposed to conventional processing, which uses pilot wafers and ex situ statistical process control. In situ sensors enable real-time wafer-to-wafer compensation for equipment and process drifts and also diagnosis of equipment status for preventive maintenance. This paper discusses the use of a spectral ellipsometer (SE) developed at Texas Instruments and the issues involved in the integration of this SE to the machine control as well as to the factory-wide computer integrated manufacturing (CIM) environment for feedforward and feedback control