Institute for Systems Research
Permanent URI for this communityhttp://hdl.handle.net/1903/4375
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Item Real-Time Growth Rate Metrology for a Tungsten CVD Process by Acoustic Sensing(2000) Henn-Lecordier, Laurent; Kidder, John N., Jr.; Rubloff, Gary W.; Gogol, C. A.; Wajid, A.; ISRAn acoustic sensor, the Leybold Inficon ComposerTM, was implemented downstream to a production-scale tungsten chemical vapor deposition (CVD) cluster tool for in-situ process sensing. Process gases were sampled at the outlet of the reactor chamber and compressed with a turbo-molecular pump and mechanical pump from the sub-Torr process pressure regime to above 50 Torr as required for gas sound velocity measurements in the acoustic cavity. The high molecular weight gas WF6 mixed with H2 provides a substantial molecular weight contrast so that the acoustic sensing method appears especially sensitive to WF6 concentration.By monitoring the resonant frequency of exhaust process gases, the depletion of WF6 resulting from the reduction by H2 was readily observed in the 0.5 Torr process for wafer temperatures ranging from 300 to 350 C. Despite WF6 depletion rates as low as 3-5%, in-situ wafer-state metrology was achieved with an error less than 6% over 17 processed wafers.
This in-situ metrology capability combined with accurate sensor response modeling suggests an effective approach for acoustic process sensing in order to achieve run-to-run process control of the deposited tungsten film thickness.
Item Integrated Dynamic Simulation of Rapid Thermal Chemical Vapor Deposition of Polysilicon(1997) Lu, Guangquan; Bora, Monalisa; Tedder, Laura L.; Rubloff, Gary W.; ISRA physically-based dynamic simulator has been constructed to investigate the time-dependent behavior of equipment process, sensor, and control system for rapid thermal chemical vapor deposition (RTCVD) of polysilicon from SiH4. The simulator captures the essential physics and chemistry of mass transport, heat transfer, and chemical kinetics of the RTCVD process as embodied in equipment. In order to complete the system-level description, reduced-order models are also employed to represent processes involving high complexity of physics. Integration of individual simulator elements for equipment, process, sensors, and control systems enables the evaluation of not only the deposition rate and film thickness, but also of a broad range of dynamic system properties such as equipment performance, gas flow conditions, wafer temperature variation, wafer optical properties (absorptivity/emissivity), gas composition in reactor, total process cycle time, consumables volume, and reactant utilization. This makes the simulator directly applicable to the optimization of process recipe and equipment design, to process control strategy, and to fault classification. This case study of polysilicon RTCVD demonstrates (1) that integrated dynamic simulation is a versatile tool for representing system-level dynamics, and (2) that such representation is pivotal in successful application of modeling and simulation for manufacturing optimization and control.Item Education in Semiconductor Manufacturing Processes through Physically-Based Dynamic Simulation(1997) Lu, G. Brian; Oveissi, Mansour; Eckard, David; Rubloff, Gary W.; ISRWe have developed physically-based dynamic simulators relevant to semiconductor manufacturing processes, which realistically reflect the time-dependent behavior of equipment, process, sensor, and control systems using commercial simulation software (VixSimTm) under Windows. Following on their successful research use for engineering design, we are applying them to manufacturing education and training. Because they reflect quantitatively and visually the detailed response of the system to user-initiated actions in real time, these simulators promise a new paradigm of active learning through ﲨands-on operation of sophisticated, expensive processing equipment. The student experience is open- ended, offering not only guided exercises but also the chance to experiment freely with the virtual equipment. Simulator modules are in development for use by both experienced engineers and manufacturing operators, with enhanced graphical interfaces tailored to the student and application.Item Polysilicon RTCVD Process Optimization for Environmentally- Conscious Manufacturing(1996) Lu, Guangquan; Bora, Monalisa; Rubloff, Gary W.; ISRIn 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.