External-Cavity Tunable Laser Using MEMS Technology

This paper introduces a tunable external-cavity diode laser using a MEMS vertical mirror fabricated on a silicon-on-insulator (SOI) wafer. This laser has the merits of simple alignment process, easy integration/packaging, and potentially large wavelength tuning range.

Fabrication of Fuze Micro-electro-mechanical System Safety Device

Fuze micro-electro-mechanical system（MEMS） has become a popular subject in recent years.Studies have been done for the application of MEMS-based fuze safety and arm devices.The existing researches mainly focused on reducing the cost and volume of the fuze safety device.The reduction in volume allows more payload and,thus,makes small-caliber rounds more effective and the weapon system more affordable.At present,MEMS-based fuze safety devices are fabricated mainly by using deep reactive ion ething or LIGA technology,and the fabrication process research on the fuze MEMS safety device is in the exploring stage.In this paper,a new micro fabrication method of metal-based fuze MEMS safety device is presented based on ultra violet（UV）-LIGA technology.The method consists of SU-8 thick photoresist lithography process,micro electroforming process,no back plate growing process,and SU-8 photoresist sacrificial layer process.Three kinds of double-layer moveable metal devices have been fabricated on metal substrates directly with the method.Because UV-LIGA technology and no back plate growing technology are introduced,the production cycle is shortened and the cost is reduced.The smallest dimension of the devices is 40 μm,which meets the requirement of size.To evaluate the adhesion property between electroforming deposit layer and substrate qualitatively,the impact experiments have been done on the device samples.The experimental result shows that the samples are still in good condition and workable after undergoing impact pulses with 20 kg peak and 150 μs duration and completely met the requirement of strength.The presented fabrication method provides a new option for the development of MEMS fuze and is helpful for the fabrication of similar kinds of micro devices.

Wireless passive flexible accelerometer fabricated using micro-electro-mechanical system technology for bending structure surfaces

We propose an inductor-capacitor(LC)wireless passive flexible accelerometer,which eliminates the difficulty in measuring the acceleration on the surface of a bending structure.The accelerometer is composed of a flexible polyimide(PI)substrate and a planar spiral inductance coil(thickness 300 nm),made using micro-electro-mechanical system(MEMS)technology.It can be bent or folded at will,and can be attached firmly to the surface of objects with a bending structure.The principle of radio frequency wireless transmission is used to measure the acceleration signal by changing the distance between the accelerometer and the antenna.Compared with other accelerometers with a lead wire,the accelerometer can prevent the lead from falling off in the course of vibration,thereby prolonging its service life.Through establishment of an experimental platform,when the distance between the antenna and accelerometer was 5 mm,the characterization of the surface of bending structures demonstrated the sensing capabilities of the accelerometer at accelerations of 20-100 m/s2.The results indicate that the acceleration and peak-to-peak output voltage were nearly linear,with accelerometer sensitivity reaching 0.27 mV/(m·s-2).Moreover,the maximum error of the accelerometer was less than 0.037%.

Temperature characteristics research of SOI pressure sensor based on asymmetric base region transistor

Based on the asymmetric base region transistor, a pressure sensor with temperature compensation circuit is proposed in this paper. The pressure sensitive structure of the proposed sensor is constructed by a C-type silicon cup and a Wheatstone bridge with four piezoresistors（R_1, R_2, R_3 and R_4/locating on the edge of a square silicon membrane. The chip was designed and fabricated on a silicon on insulator（SOI） wafer by micro electromechanical system（MEMS） technology and bipolar transistor process. When the supply voltage is 5.0 V, the corresponding temperature coefficient of the sensitivity（TCS） for the sensor before and after temperature compensation are -1862 and -1067 ppm/℃, respectively. Through varying the ratio of the base region resistances r_1 and r_2, the TCS for the sensor with the compensation circuit is -127 ppm/℃. It is possible to use this compensation circuit to improve the temperature characteristics of the pressure sensor.