Modeling and Control of Single Wafer Microelectronics Processes

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An emerging technology is the single wafer rapid thermal chemical vapor deposition (RTCVD) system. In these systems a single wafer is loaded into a cooled stainless steel chamber where low pressure gases react on the radiatively heated wafer surface. Compared to the multiwafer system, the RTCVD system represents considerably less cost both in initial capital and in required wafer fabrication floor space. In addition, cold wall operation in the RTCVD system eliminates the particulate generation occurring on the hot walls of the multiwafer system. Adding plasma enhancement to a CVD reactor (PECVD) prevents thermal damage to the wafer by permitting lower temperatures of operation. The throughput for single wafer reactors needs to be maximized (e.g. rapid thermal processing) to be competitive with multiwafer systems. This study will focus on deposition and etch technology using single wafer CVD and etching reactors with plasma enhancement and rapid thermal processing capability. For these unit operations, new fundamental (theoretical) mathematical models will be developed that relate the operating and equipment design variables to reactor performance. These models will be verified using data from two reactor configurations; one of these reactors is a flexible manufacturing reactor from Texas Instruments, which will be used to study silicon nitride deposition. The other is a reactive-ion etcher using carbon tetrafluoride CF4 and hydrogen H2. This project will also research new control strategies that permit design of model- based controllers for each reactor. Of particular interest will be a nonlinear programming-based technique called nonlinear model predictive control. Active collaboration with personnel at Texas Instruments and SEMATECH will facilitate ultimate transfer of this technology to the semiconductor industry.