Science Letters:Mask synthesis and verification based on geometric model for surface micro-machined MEMS

Traditional MEMS （microelectromechanical system） design methodology is not a structured method and has become an obstacle for MEMS creative design. In this paper, a novel method of mask synthesis and verification for surface micro-machined MEMS is proposed, which is based on the geometric model of a MEMS device. The emphasis is focused on synthesizing the masks at the basis of the layer model generated from the geometric model of the MEMS device. The method is comprised of several steps： the correction of the layer model, the generation of initial masks and final masks including multi-layer etch masks, and mask simulation. Finally some test resuhs are given.

Enabling electrically tunable radio frequency components with advanced microfabrication and thin film techniques

Multi-function,multiband,cost-effective,miniaturized reconfigurable radio frequency(RF)components are highly demanded in modern and future wireless communication systems.This paper discusses the needs and implementation of multiband reconfigurable RF components with microfabrication techniques and advanced materials.RF applications of fabrication methods such as surface and bulk micromachining techniques are reviewed,especially on the development of RF microelectromechanical systems(MEMS)and other tunable components.Works on the application of ferroelectric and ferromagnetic materials are investigated,which enables RF components with continuous tunability,reduced size,and enhanced performance.Methods and strategies with nano-patterning to improve high frequency characteristics of ferromagnetic thin film(e.g.,ferromagnetic resonance frequency and losses)and their applications on the development of fully electrically tunable RF components are fully demonstrated.

A Generic MEMS Fabrication Process Based on a Thermal Budget Approach

A modular and generic monolithic integrated MEMS process for integrating CMOS technology with polysilicon microstructures is presented. The proposed process flow is designed with an intra CMOS approach to fabricate the microstructures into trenches without the need of planarization techniques. After annealing at 1000°C at significant period of time, it is shown that Id-Vg characteristics of the CMOS transistors remain almost unchanged, indicating their robustness to the intra process fabrication for the micromechanical structures. The CMOS module is designed with a 3 μm length as a minimum feature and this process results with a minimum of residual strain and stress on the micromechanical devices (ε = 1.28 × 10-4 and σ = -21 MPa).

A novel micro-rolling&incremental sheet forming hybrid process:Deformation behavior and microstructure evolution

Thin-walled metal parts with functional micro-featured surface have broad application prospects in the fields of resistance reduction,noise reduction,etc.In this study,a novel micro-rolling&incremental sheet forming hybrid process(μR-ISF)is proposed to fabricate thin-walled metal parts with microgroove arrays.An analytical model which relates the rolling force and microgroove depth in the micro-rolling stage was first established.Then,the formation mechanism of microgroove morphology during both micro-rolling stage and macro-shape forming stage are investigated.After the micro-grooved sheet being incrementally formed,a significant reduction(between 21%to nearly 60%)is occurred in the depth of both transverse and longitudinal grooves compared to the flat sheet.Meanwhile,the width of transverse grooves decreases slightly by about 10%on average,while the width of longitudinal microgrooves increases significantly by more than 30%on average.After micro-rolling,85°{102}tensile twins appear on the micro-grooved sheet and the percentage of 65°{112}compressive twins increases.After incremental forming,the percentage of low-angle grain boundaries and the density of geometrically necessary dislocations in the formed part increase significantly,and the grain size distribution becomes more uniform.The present work provides a new strategy for the fabrication of 3D metal thin-walled components with surface micro-features.

A Sacrificial Layer Etching Method Applied in Surface Micromachining Using Agitated BHF and Glycerol Solution

A modified buffered-HF solution with NH4 F ： glycerol ： HF（4 ： 2 ： 1）is studied. With the implementation of a heating and agitating mechanism, this method is applied in a sacrificial layer etching scheme that increases the selectivity between silicon dioxide and aluminum. The etching rates of SiO2 and Al as a function of solution temperature are determined. Moreover,the effects of adding glycerol and agitating the etchant are examined and compared with this method. Finally, this method is tested on an actual device, and its efficiency is scrutinized.

Investigation on surface structuring generated by electrochemical micromachining

Surface geometrical features and their function- ality depend on the manufacturing process which is employed for fabrication of surface structures. Maskless electrochemical micromachining （EMM） is used to generate various surface structures for diminishing and controlling friction and wear to increase the lifetime, reliability, and efficiency of mechanical systems. This paper presents a method for the generation of structured surfaces on stainless steel （SS-304） surfaces by using maskless EMM. The micropatterned tool is composed of 800 μm diameter circular holes in a 5 × 5 matrix form. The indigenously developed EMM set up consists of an EMM cell, electrical power supply system, and a controlled vertical cross-flow electrolyte circulation arrangement to control the influence of process parameters during the generation of the micro features of structured surfaces. The single structured cathode tool is used for the mass production of structured surfaces with a short fabrication time in the industrial context by avoiding the use of an individual masking process for each workpiece. The process has been characterized in terms of the effects of predominant process parameters such as machining voltage, electrolyte concentration, duty ratio, pulsed frequency, and machining time on the machined surface characteristics such as current efficiency, machining accuracy, and depth of the circular pattern on the stainless steel surfaces. A mathematical model is also developed to determine the theoretical depth of the dimple pattern and correlate the theoretical depths with actual depths as obtained by experimentation. Moreover, an effort has been made to study the structuringcharacteristics on the basis of micrographs obtained duringthe EMM.

Simulation and fabrication of thin film bulk acoustic wave resonator

In this paper, we present the simulation and fabrication of a thin film bulk acoustic resonator （FBAR）. In order to improve the accuracy of simulation, an improved Mason model was introduced to design the resonator by taking the coupling effect between electrode and substrate into consideration. The resonators were fabricated by tile eight inch CMOS process, and the measurements show that the improved Mason model is more accurate than a simple Mason model. The Qs （Q at series resonance）, Qp （Q at parallel resonance）, Qmax and k2 of the FBAR were measured to be 695, 814, 1049, and 7.01% respectively, showing better performace than previous reports.