AVS 47th International Symposium
    Manufacturing Science and Technology Thursday Sessions
       Session MS-ThM

Paper MS-ThM8
W CVD Thickness Metrology and Run-to-Run Control using Mass Spectrometry

Thursday, October 5, 2000, 10:40 am, Room 304

Session: Advanced Modeling and Control for IC Manufacturing
Presenter: Y. Xu, University of Maryland
Authors: Y. Xu, University of Maryland
T. Gougousi, University of Maryland
R. Sreenivasan, University of Maryland
G.W. Rubloff, University of Maryland
J.N. Kidder, University of Maryland
E. Zafiriou, University of Maryland
Correspondent: Click to Email
For a H2/WF6 CVD process for selective W deposition in an Ulvac cluster tool, mass spectrometry has been used to observe HF product generation and H2 depletion. HF signal was proportional to the deposited W thickness to about 7%, providing an in-situ thickness metrology as a candidate to drive run-to-run thickness control. To assess this possibility, a systematic temperature drift of -50C per wafer was introduced, which in the absence of control would cause the film thickness to decrease by 40-50% over a ten wafer lot. Using a robust control algorithm to maintain a constant integrated HF mass spec signal by adjusting the nominal deposition time, the effect of the temperature drift on deposited film thickness was largely compensated, and the W film thickness was maintained within 10% of the target value. The metrology accuracy was limited by the low (about 3%) reactant conversion rate of the process, coupled with significant background signals. Since blanket W CVD processes as employed in manufacturing achieve much higher conversion efficiencies (40-50%), we anticipate considerable improvement in the efficacy of metrology and control in these situations. Our results, and their projection to realistic manufacturing scenarios, present an encouraging opportunity to use in-situ chemical sensing for process metrology and control.