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Becoming another key technology for system integration, GaAs based millimeter wave antenna is fabricated by MEMS technology, with high permittivity dielectric substrates. To obtain good performance, it is necessary to achieve the equivalent of low dielectric constant of the local area below microstrip patch antenna. The article describes deep etching fabrication and multiple etching with thick photoresist masking to creat air cavity under the microstrip patch which usually has the height from 70% to 80% of the original media substrate, thus it forms the air-mixed media substrate. Especially for precision control of the substrate thickness, use back thinning and high-precision polishing processes. At last realize back cavity depth of 227μm in the GaAs substrate and complete the process of Ka band MEMS patch antenna. The measurement results: the center frequency is 37.9 GHz, bandwidth is 4.4%, radiation efficiency above 50%.

This is mainly due to the high chemical reactivity and spontaneous etching nature of the fluorine radicals towards silicon, and the high volatility of the silicon fluorides as reaction products. Anisotropy can only be achieved by the inclusion of sidewall passivation schemes to the process. The existing approaches to deep reactive ion etching (DRIE) of silicon are distinguished by the way sidewall passivation is achieved, the key to anisotropy and overall performance of the etch process. Cryogenic etching and the so-called Bosch process with alternating etch and passivation cycles are the two most well-known high-aspect-ratio silicon etch processes and are discussed in this paper.

The design and fabrication of MEMS capacitive differential pressure sensor is reported. Silicon membrane is used as movable electrode. Gold metal film on glass is used as fixed electrode. Anodic bonding is used to bond together the silicon and glass to form the capacitive pressure sensor. The measurement capacitance of the sensors is 5.37 pF at an applied pressure of 0 kPa and 7.26 pF and the full operating range of 40 kPa.The ratio of changed to initial capacitance was 0.35. The error of the MEMS capacitive pressure sensor is less than 4‰ full-scale(FS) by using quadratic curve fitting which can meet most application requirements.

In this paper the oxygen plasma dry release process for membrane-bridge RF MEMS switches is studied and several methods are used to improve the dry release process. The residual PR (Photoresist) on the device substrate after different process time are observed and measured in this paper. The measured data shows that the residual PR exponentially reduces with etch time. It is found that the residual PR on the bottom surface of the membrane bridge is more than that on the substrate. The completely released RF MEMS switch using oxygen plasma dry etch process is obtained.

In this paper, a novel RF MEMS switch driven by combs with low insertion loss is presented. The developed SPST RF MEMS switch with a lateral resistive contact and gold structure layer on a silicon substrate has been fabricated by surface micromachining process. The RF performance of the switch indicates an insertion loss below 0.30 dB at 20 GHz, a return loss better than 20 dB and isolation greater than 30 dB. Good RF characteristics have been achieved by the large contact area and a lateral Au-to-Au resistive contact.

We report our efforts towards designing and fabricating capacitive microaccelerometers with flat bottom surfaces free from the notching effects of Deep Reactive Ion Etching (DRIE) based on SOI process. The substrate layer under the device structure is etched and a metal film is deposited to the backside of moving structure for protecting the bottom surfaces so that the stiction problem and notching effects are avoided. The test results demonstrate that SOI accelerometers have been released successfully. The measured sensitivity is 169.1mV/g and the linearity of output is within 0.202%.

We report our efforts towards fabricating nanomechanical resonators patterned by optical lithography in silicon nitride. Optical lithography has advantages of low cost and high efficiency over electron-beam lithography. Double clamped beam resonators with thickness 150nm, length and lateral dimensions 20um, 800nm have been designed. Through utilizing reactive ion etching and controlling gas flow, reaction time of CF4 and O2 plasma and power of the upper and lower electrode, nanomechanical resonators with lateral dimensions within 200nm are demonstrated.

The study is performed to implement the Gold-Gold thermocompression bonding for the wafer-level packaging of MEMS chips. Numerous experimental attempts have been carried out to select the metal film adhesive to avoid the Au-Si melt together and optimize bonding processes to intensify the Au-Au eutectic bonding. Finally the results display that the eutectic bonding of the gold-gold are arrived as electrical as well as mechanical interconnection of the MEMS structure and as seal as well as bonding intension.

A method of fabrication of micro via-hole by wet-etching of Pyrex glass is presented in the paper. The through holes with double funnel-shape have been fabricated attribute to isotropic etching. Furthermore, the funnel-shape holes are advantageous to the joint sealing and have been applied to fabricate microfluid chips. The results show that the proportioning of corrosion solution is HF:HCl:H2O=3:6:10, and the corrosion rate is about 0.67um/min, the diameter of the holes on the both-side of the wafer is only 750 um, the middle ones are 300um

This paper presents a kind of fine polishing technique that adopts three-step polishing procedure and keeping-wafer-wet method. In order to remove the damaged layer created by lapping process or improve surface condition of silicon wafer, polishing process is needed. In this paper, techniques of improving the surface roughness of silicon are studied, three different polishing processes are presented, and optimum condition has been attained. Experiments of Si-Si bonding are also performed, and results show that after polishing ends, keeping surface of wafer wet is necessary to avoid slurry agglomerating.

Both triangular lattice and square lattice photonic crystals with lattice constant 400 nm and the radius 200 nm of the air pores in the silicon substrate have been designed, fabricated and realized. The processes of the fabrication of the two-dimensional photonic crystals, based on silicon, including mask making, electron-beam lithography, and inductively coupled plasma etching are introduced.

Cantilever beam DC-contact RF MEMS switches, with bias electrodes physically insulated from the RF/microwave transmission line (t-line), have been developed for broadband communication system applications. The paper presents the design, optimization and equivalent circuit model for the MEMS switches. The beam is composed of multilayer thin films formed by a slightly tensile stressed dielectric and metal layer. A MEMS switch sample has been fabricated based on a low temperature surface micromachining process. On-wafer measurement results are as follows: insertion loss less than 0.8 dB; isolation more than 26 dB at 0.1-26 GHz; applied voltage 30-80 V.