Radical recombination sensor based on dual probe thermopile heat flux sensors
conference paper
Hydrogen radicals play an important role in, e.g., the cleaning of extreme ultraviolet reflective mirrors. Therefore, there is a need to quantify the surface radical flux in the various (plasma) setups where these effects are studied. In this paper, a catalytic radical sensor is presented, based on the measurement of the recombination heat of radicals on a surface, using dual probe thermopile heat flux sensors (HFSs). The first HFS1 has a high recombination (probability) coefficient coating, e.g., Pt. The second HFS2 has a low recombination coefficient coating, e.g., Al2O3. Signal subtraction largely eliminates common mode heat losses/gains such as conduction/convection and IR radiation, the net result representing the radical recombination heat. The signal can be improved by switching the radical source on/off at regular intervals. Radical recombination rates were measured in a remote microwave plasma chamber (38 Pa H2) over the range 1018−1021 atH/(m2 s), with nearly linear response as a function of plasma power setting. The sensor full scale limit is ∼1023 atH/(m2 s) and is dictated by the maximum allowable sensor surface temperature (<250 °C).
TNO Identifier
869269
Source
Journal of vacuum science and technology A, 37(November/December), pp. 061302-1 - 061302-7.
Publisher
American Vacuum Society AVS
Collation
7 p.
Place of publication
New York City, NY, USA
Pages
061302-1 - 061302-7
Files
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