James Welch

Application of a downstream calorimetric probe to reactive plasma

We explore the application of calorimetric probe located downstream from the plasma zone. By positioning the probe in a downstream location, the probe signal can be correlated with the integral energy flux carried by the effluent species as they propagate downstream from the plasma zone. Because the integral energy flux channeled downstream depends on the plasma conditions, it is possible to infer the plasma conditions from the probe response even though the probe is located away from the plasma zone. A calorimetric probe, based on resistance-temperature detector principle, adequate for fluorine plasma exposure is constructed. Probe operation is demonstrated for NF3–Ar plasmas.

Micromachined chemical sensor with dual-transduction mechanisms

Chemical sensors based on a microhotplate platform generally function via a conductometric or calorimetric transduction mechanism. In addition to these mechanisms, a mechanical transduction mechanism is proposed based on the detection of the microhotplate bending due to volume change of functional layers. In this letter, we demonstrate sensing of gaseous hydrogen based on volumetric expansion of Pd∕Y functional layers. In this case, the embedded polysilicon heater element also serves as the piezoresistive strain-detecting element, changing its resistance as the microhotplate bends. This transduction mechanism can be used independently of, or in conjunction with, a simultaneous conductometric or calorimetric mechanism.

End-pointing chamber clean by calorimetric probing of process effluent

The semiconductor industry employs gas-phase cleaning widely to remove materials deposited on the chamber walls during thin-film deposition processes. Chamber clean end-pointing—i.e., terminating the process when the chamber is clean—is desirable to manage cost of ownership and environmental impact. Existing end-pointing methods tend to rely on changes of plasma characteristics as the in situ plasma removes the deposit in time. Chamber clean technology is moving towards remote generation of plasma species for cleaning. In this arrangement, the chamber is located downstream from the plasma source. Because the etching reaction occurs ex situ, there are no relevant changes occurring in the plasma characteristics, and the effectiveness of many existing methods decreases. We report the development of a calorimetric probe for chamber clean end-pointing. The probe has an all solid-state construction and is engineered to be immersed in the process effluent during end-pointing operation. When the probe is operated...