Chil-Keun Park

A micromachined robust humidity sensor for harsh environment applications

This paper reports a high-sensitive robust humidity sensor using a pair of thermally isolated membranes on which includes meander shaped metal resistive elements are formed. The sensing mechanism of the humidity sensor is based on the difference of thermal conductivity with the amount of moisture in air. The sensor exhibits a sensitivity of 0.054 mV/%RH and a response time of 25 sec. Measurements show a remarkably small nonlinearity of 1% FS and a hysteresis of below 2% over a wide range from 40 to 90% RH. Various reliability tests required for practical use in food processing applications, such as a long-term stability test in high/low temperature (150/spl deg/C/-70/spl deg/C) and high humidity (95% RH) environment and a contamination test, reveal its superior durability in harsh environment.

Micromachined silicon optical bench for the low-cost optical module

A novel self-aligning silicon optical bench for fully passive alignment of optical components and its fabrication method are presented. Key technologies developed in this work are multi- step silicon anisotropic etching for manufacturing SiOB, photolithography on three-dimensional surface, precise size control of optical active chip, and flux- and pressure-free die bonding technology. The measured size tolerance of silicon grooves for the active chip and the fiber reveals less than plus or minus 0.5 micrometer. The photolithography process on three-dimensional surface of each site is investigated to get the patterns for deposition of electrodes, mirror, and solders, respectively. The precisely cleaved laser diode chip is obtained by V-groove etching to define the cleaving lane. This technique allows the chip to be defined with a dimensional accuracy of plus or minus 0.5 micrometer. In addition, the pressure-free bonding technique using the electroplated Au-Sn solder makes it possible to reduce the production cost. The fabricated SiOB does not need any pre- alignment process of the optical chip and fiber to desired position such as index alignment method. On the basis of these technologies, it is shown that the fully passive alignment of optical component packaging is successfully preformed. The measured results reveal that the coupling efficiency of the laser diode module was achieved better than 8% and the responsivity of the photo diode module was better than 0.85 A/W.