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Proceedings Paper

Advanced statistical process control of a chemical vapor tungsten deposition process on an Applied Materials Centura reactor
Author(s): Jerry A. Stefani; Scott Poarch; Sharad Saxena; P. K. Mozumder
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Paper Abstract

An advanced multivariable off-line process control system, which combines traditional Statistical Process Control (SPC) with feedback control, has been applied to the CVD tungsten process on an Applied Materials Centura reactor. The goal of the model-based controller is to compensate for shifts in the process and maintain the wafer state responses on target. In the present application the controller employs measurements made on test wafers by off-line metrology tools to track the process behavior. This is accomplished by using model- bases SPC, which compares the measurements with predictions obtained from empirically-derived process models. For CVD tungsten, a physically-based modeling approach was employed based on the kinetically-limited H2 reduction of WF6. On detecting a statistically significant shift in the process, the controller calculates adjustments to the settings to bring the process responses back on target. To achieve this a few additional test wafers are processed at slightly different settings than the nominal. This local experiment allows the models to be updated to reflect the current process performance. The model updates are expressed as multiplicative or additive changes in the process inputs and a change in the model constant. This approach for model updating not only tracks the present process/equipment state, but it also provides some diagnostic capability regarding the cause of the process shift. The updated models are used by an optimizer to compute new settings to bring the responses back to target. The optimizer is capable of incrementally entering controllables into the strategy, reflecting the degree to which the engineer desires to manipulates each setting. The capability of the controller to compensate for shifts in the CVD tungsten process has been demonstrated. Targets for film bulk resistivity and deposition rate were maintained while satisfying constraints on film stress and WF6 conversion efficiency.

Paper Details

Date Published: 16 September 1994
PDF: 12 pages
Proc. SPIE 2336, Manufacturing Process Control for Microelectronic Devices and Circuits, (16 September 1994); doi: 10.1117/12.186797
Show Author Affiliations
Jerry A. Stefani, Texas Instruments Inc. (United States)
Scott Poarch, Texas Instruments Inc. (United States)
Sharad Saxena, Texas Instruments Inc. (United States)
P. K. Mozumder, Texas Instruments Inc. (United States)


Published in SPIE Proceedings Vol. 2336:
Manufacturing Process Control for Microelectronic Devices and Circuits
Anant G. Sabnis, Editor(s)

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