Polysilicon RTCVD Process Optimization for Environmentally- Conscious Manufacturing
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In the semiconductor manufacturing industry, optimization of advanced equipment and process designs must include both manufacturing metrics (such as cycle time, consumables cost, and product quality) and environmental consequences (such as reactant utilization and by-product emission). We have investigated the optimization of rapid thermal chemical vapor deposition (RTCVD) of polysilicon from SiH4 as a function of process parameters using a physically-based dynamic simulation approach. The simulator captures essential time-dependent behaviors of gas flow, heat transfer, reaction chemistry, and sensor and control systems, and is validated by our experimental data. Significant improvements in SiH4 utilization (up to 7 x) and process cycle time (up to 3 x) can be achieved by changes in (i) timing for initiating wafer heating relative to starting process gas flow; (ii) process temperature (650 - 750oC ) ; and (iii) gas flow rate (100 - 1000 sccm). Enhanced gas utilization efficiency and reduced process cycle time provide benefits for both environmental considerations and manufacturing productivity (throughput). Dynamic simulation proves to be a versatile and powerful technique for identifying optimal process parameters and for assessing tradeoffs between various manufacturing and environmental metrics.