In this paper, we describe a directional thin-film silicon photodetector with the objective of optical micro-encoder application. A directional photodetector with high absorption efficiency at a specific angle of incident light is based on guided-mode resonance (GMR) of subwavelength grating. The sensitive direction is tunable by changing the grating period. Numerical analysis, fabrication and device performance are presented.

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Parylene has intrinsic tensile stress on account of mismatch of thermal coefficient of expansion (TCE) between the substrate and the deposited film. Therefore, the stiffness k of a Parylene suspended structure under tensile stress is much higher than that under no stress, which also leads to its higher resonant frequency of f_r. The Parylene accelerometer being developed by authors, in which a proof mass is supported by several beams, is focused on. The FEM simulation is employed for the structure with straight beams, and it is proven that f_r∝1/l^0.45 holds true under tensile stress of 10 MPa, while f_r∝1/l^1.5 holds true under no tensile stress, where l is the beam length. This fact means a relatively long beam is necessary under tensile stress for the purpose of lowering f_r, i.e., increasing the sensitivity of 1/f_r². To cope with this problem, a structure with spiral shaped beams is proposed, and its f_r is simulated. Parylene suspended microstructures are practically fabricated, and their experimental are obtained. By comparing the experimental results with the simulated ones, the validity of the simulation is proven, and the effectiveness of spiral beam is confirmed in the viewpoint of not only realizing a long beam in a limited space but also realizing stress relaxation.

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This article proposes an accelerometer, that consists of a dielectric seismic mass and a comb-shaped planar capacitor below it. Because the simple structure of the device allows using polymer Parylene as the proof mass and the support beams, the technology is greatly simplified and only surface micromachining is required. Measurement principle is based on detecting the capacitance change with respect to the dielectric mass movement in the fringe electrical field. This principle is verified by both a theoretical calculation using an approximate model and a FEM simulation. As Parylene has intrinsic tensile stress, comparatively long beams are necessary for lowering the resonant frequency f_r of the sensor structure, i.e., increasing the accelerometer sensitivity. A spiral beam is effective for not only realizing a long beam in a limited space, but also realizing the stress relaxation, which leads to the high sensitivity. Parylene accelerometers with straight beams and spiral beams are fabricated. Their sensitivities are characterized with the aid of an off-chip capacitive readout IC, confirming the good linearity of the output voltage to the input acceleration and the effectiveness of utilizing spiral beams.

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A new method to obtain the output voltage V_o proportional to the absolute temperature T is proposed. The linear relationship between V and T in the measurable temperature range of about 77-470 K is achieved using a commercial Si-pn diode. In this temperature-sensor the ac voltage change in the pn junction diode due to the temperature change is measured for a constant amplitude of superimposed ac small signal of current δI on the constant forward dc current I₀. This sensor has merits that it can be calibrated at only one temperature point, that the output voltage is proportional to the absolute temperature T and that the ac signal circuits can be isolated from dc bias voltage circuits. In addition, we have ascertained that a square wave as the superimposed ac signal of current δI is superior to the sine wave because of easy connection to the digital circuits and easy measurement of the amplitude of the ac output voltage.

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