The silicon-glass MEMS high dose radiation sensor with the optical read-out, acting above 10 kGy has been presented. The sensor consists of a microchamber filled with small portion of high density polyethylene (HDPE) and thin silicon membrane. The principle of operation of the sensor is based on radiolysis effect of the HDPE which, upon radiation exposure, releases the hydrogen. The hydrogen increases the pressure inside the microchamber causing the deflection of the membrane, which is proportional to the pressure, thus to radiation dose. The sensor has been irradiated with high energy electron beam with dose 5÷40 kGy. The displacement of the membrane has been detected by optical interferometer. The relative generated pressure inside the sensor chamber has been found very high (up to 180 kPa). It shows that response of a micro-scaled MEMS sensor is much more effective in comparison to macro-scaled solutions.
Many today's microsystems like strain-gauge-based piezoresistive pressure sensors contain doped resistors. If one wants to predict correctly the temperature impact on the performance of such devices, the accurate data about the temperature coefficients of resistance (TCR) are essential. Although such data may be calculated using one of the existing mobility models, our experiments showed that we can observe the huge mismatch between the calculated and measured values. Thus, in order to investigate the TCR values, a set of the test structures that contained doped P-type resistors was fabricated. As the TCR value also depends on the doping profile shape, we decided to use the very thin, 340 nm thick SOI wafers in order to fabricate the quasi-uniformly doped silicon layers ranging from 2 × 10 17 at cm −3 to 1.6 × 10 19 at cm −3 . The results showed that the experimental data for the first-order TCR are quite far from the calculated ones especially over the doping range of 10 18 -10 19 at cm −3 and quite close to the experimental ones obtained by Bullis about 50 years ago for bulk silicon. Moreover, for the first time, second-order coefficients that were not very consistent with the calculations were obtained.
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