A single-chip silicon condenser microphone with a single deeply corrugated diaphragm (SDCD) has been developed. The fundamental characteristics, including mechanical sensitivity, resonance frequency, zero-pressure offset and temperature dependence of the diaphragm, are simulated using a finite element model (FEM). An analytical model is presented to validate that the higher mechanical sensitivity of the SDCD compared with the flat diaphragm with clamped edges is achieved by both releasing the residual stress and reducing the effective mechanical constant of the diaphragm structure. The electrostatic–structural coupling FEM analysis is used in combination with equivalent circuits to evaluate and understand the mechanical, electrostatic and acoustic performances of the microphone. The measurements show reasonable agreements with the theoretical predictions.

An integrated system of a silicon-based microfabricated polymerase chain reaction (microPCR) chamber and microfabricated electrophoretic glass chips have been developed. The PCR chamber was made of silicon and had aluminum heaters and temperature sensors integrated on the glass anodically bonded cover. Temperature uniformity in the reaction chamber was +/-0.3 degrees C using an improved novel "joint-heating" scheme. Thermal cycling was digitally controlled with a temperature accuracy of +/- 0.2 degrees C. Small operating volumes together with high thermal conductivity of silicon made the device well suited to rapid cycling; 16 s/cycle were demonstrated. For analysis of the PCR products, the chamber output was transferred to the glass microchip by pressure. Analysis time of PCR amplified genomic DNA was obtained in the microchip in less than 180 s. The analysis procedure employed was reproducible, simple and practical by using viscous sieving solutions of hydroxypropylmethylcellulose and dynamically coated microchip channels with poly(vinylpyrrolidone). DNA fragments that differ in size by 18 base pairs (bp) were resolved. Analysis of genomic male and female amplified DNA by microPCR was achieved in microchip, and application of the integrated microPCR-microchip for the identification of bird sex was tested. Genomic DNA samples from several bird species such as pigeon and chicken were analyzed. Hence, the system could be used as well to determine the sex of avian species.

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A novel silicon condenser microphone with a corrugated diaphragm has been proposed, designed, fabricated and tested. The microphone is fabricated on a single wafer by use of silicon anisotropic etching and sacrificial layer etching techniques, so that no bonding techniques are required. The introduction of well-performing corrugations has greatly increased the mechanical sensitivities of the microphone diaphragms due to the reduction of the initial stress in the thin fdms. For the purpose of further decreasing the thin film stress, composite diaphragms consisting of multilayer (polySi/Siz N,/polySi) materials have been fabricated, reducing the initial stress to a much lower level of about 70 MPa in tension. Three types of corrugation placements and several corrugation depths in a diaphragm area of 1 mm2 have been designed and fabricated. Microphones with flat frequency response between 100 Hz and 8-16 kHz and opencircuit sensitivities as high as 8.1-14.2 mV/Pa under the bias voltages of 10-25 V have been fabricated in a reproducible way. The experimental results proved that the corrugation technique is promising for silicon condenser microphone. [185]

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