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A thin-film multijunction thermal converter was fabricated through the process using 6 inch silicon wafer semiconductor process and bulk micromachining. Evanohm R alloy and chromel-constantan were used as a heater and thermocouple materials, respectively. The temperature coefficient of resistance of Evanohm R heater was about 75.12 ppm/ and the voltage sensitivity of the thermal converter indicated about 5.75 mV/mW in air. The transfer differences, measured by FRDC-DC method in the frequency range from 20 Hz to 10 kHz, showed the value under about 1.36 ppm, 0.83 ppm for the film thickness of 500, 200 nm, respectively. And in case of a 200 nm-thick thermal converter, the AC-DC transfer differences seems to be stabilized below the value of 1 ppm in the frequency range from 1 kHz to 500 kHz.

A chromel-alumel thermoelectric flow sensor using thermal isolation membrane was fabricated. Temperature coefficient of resistance of thin film Pt-heater was about , and Seebeck coefficient of chromel-alumel thermocouple was about . The sensor showed that thermoelectric voltage decreased as thermal conductivity of gas increased, and -flow sensitivity increased as heater voltage increased or the distance between heater and thermocouple decreased. When heater voltage was about 2.5 V, -flow sensitivity and thermal response time of the sensor were about and 0.18 sec., respectively. Linear range in flow sensitivity of the flow sensor was wider than that of Bi-Sb flow sensor.

This paper proposes a thick oxide air-bridge structure which can be used as a substrate for RF circuits. The structure was fabricated by anodic reaction, complex oxidation and micromachining technology using TMAH etching. High quality films were obtained by combining low temperature thermal oxidation (, 1 hr at ) and rapid thermal oxidation (RTO) process (, 2 min). This structure is mechanically stable because of thick oxide layer up to and is expected to solve the problem of high dielectric loss of silicon substrate in RF region. The properties of the transmission line formed on the oxidized porous silicon (OPS) air-bridge were investigated and compared with those of the transmission line formed on the OPS layers. The insertion loss of coplanar waveguide (CPW) on OPS air-bridge was (about 2dB) lower than that of CPW on OPS layers. Also, the return loss of CPW on OPS air-bridge was less than about -20 dB at measured frequency region for 2.2 mm. Therefore, this technology is very promising for extending the use of CMOS circuitry to higher RF frequencies.

NiCr-heaters with three different thicknesses ranging from 400 nm to 800 nm were fabricated and their characteristics were compared for the purpose of developing a chromel-alumel multijunction thermal converter for low input voltage with low frequency. The thermoelectric effect-induced AC-DC voltage transfer difference of the thermal converter with a built-in NiCr-heater of 400 nm-thickness was in the DC reversing frequency of with appling and the difference was increased to in the frequency of , when both thermoelectric effects and frequency effects were considered, showing the thermal converter would be suitable for the low input voltage application with low frequency.