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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.

The Space Infrared Telescope Facility (SIRTF), planned for an early 21st century launch, is the fourth of NASA's Great Observatories. It contains a 1-meter class Ritchey-Chretien telescope, all of whose components will be cryogenically cooled to superfluid helium temperatures. Achievement of diffraction-limited performance at wavelengths as short as 3 μm will likely require realignment of the secondary mirror following launch. Efficient use of SIRTF's limited cryogenic lifetime (5 years, with a sensitivity of 1 month/mW) requires a means for tilting the secondary mirror to rapidly relocate the telescope's line of sight and to map small regions of the sky. Furthermore, at the longest SIRTF wavelengths (200-1200 μm) the emission from the cooled telescope will be significant, thereby requiring the use of periodic tilt oscillations of the secondary mirror to modulate the signal.

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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 at constant temperature, the probe power is closely related to the energy flux carried by the effluent, which in turn correlates with chamber conditioning. We examine probe response to NF 3 plasma and etching of silicon specimens in a laboratory setting, and demonstrate successful end-pointing for both in situ and remote chamber clean on production tools. The probe results compare favorably with other coinstalled end-pointing solutions.