Thermal sensor microfabrication and related undergraduate research projects

We describe the microfabrication and characterization of thermopiles having up to 24 sensing junctions. Chromium-nickel devices were fabricated on glass substrates, and aluminum-silicon devices were processed on silicon wafers. Sensitivities as high as approximately 7 mV//spl square/C were measured for the aluminum-silicon devices. The thermal mass of the sensing region of these devices was reduced by etching a well in the back surface of the silicon substrate, beneath the sensing junctions. The time constants of our fastest sensors were 33 ms. This work represents one example of undergraduate research carried out in our microfabrication laboratory. Other examples are also described, including solid state electrochromic devices, and silicon photovoltaic cells with textured surfaces, conventional metal grid contacts, and transparent conducting oxide contacts.