Papers by Keyword: Sacrificial Layer

Abstract: A selective wet etching process for fabricating SiGe and Ge nanowires for gate all around transistors is introduced in this paper. Two formulated proprietary chemical mixtures with highly selective etching properties (Si vs. SiGe and SiGe vs. Ge) can effectively dissolve the sacrificial layers with minimal damage to the interstitial nanowire materials. The Auger Electron Spectroscopy (AES) surface characterization indicates that no chemical contamination is left after the wet etching process.

Abstract: Attractive for MEMS, PZT thick films are often microstructured on Si supporting platforms to span the gap between ceramics and thin film technologies. Printing process might lead to lower cost than ceramic process to open routes for MEMS applications. In this paper processing by screen-printing of Au/PZT/Au thick-films supported on alumina or completely released from the substrate are described. Investigations of the film microstructures nevertheless show lower densification than those of bulk ceramics. Prior to selective coating deposition, routes to improve the reduction of the film’s porosity are proposed.

Abstract: Bilayer thick films of sacrificial titanium dioxide and Nb-doped lead zirconate titanate (PZTN) have been deposited on bare silicon wafers using electrophoretic deposition (EPD) technique. Deposition of such ceramic particles, dispersed ethanol-based suspensions, on semiconductor substrate has been made possible after preparation of alloyed junctions Al/Si characterized by ohmic behaviour. Sintering of green TiO₂/PZTN films was performed at 900 °C for 1 h. The composition of the films, the thickness and relative density of the deposited materials have been analysed by EDS-SEM analysis. The lead diffusion through the silicon wafer has been reduced.

Abstract: In order to obtain ultrasmooth polymer films, in combination with sacrificial layer a variety of impending structures in MEMS devices can be easily prepared. Two methods using polymer concentration control and spin speed adjustment to planarize polymer surface are presented. The influence of polymer concentration and spin speed on the effect of photoresist planarization is studied on. Through a large number of experiments, optimized process parameters are collected. It is found that the roughness was reduced effectively when the spin high speed was 5000rpm for 50 seconds under the condition of volume dilution ratio of 1:5. This process is able to produce a smooth surface structure.

Abstract: 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.

Abstract: The armature fabricated with the sacrificial layer techniques is an important part of micro electromagnetic relay. So the sacrificial layer is one of the key fabrication processes in the realization of prototype of micro electromagnetic relay. In this paper several sacrificial layers including Copper, Polyimide and Positive photoresist are studied based on the investigation of the research on sacrificial layer and binding the characteristic of micro electromagnetic relay’s fabrication process.

Abstract: The purpose of this paper is to demonstrate sensors and structures fabricated using the LTCC technology, which has been addressed and employed increasingly as a smart packaging approach for several applications. The focus will be on inclination and cantilever force sensors and micro-fluidic structures. Motivation for selection of LTCC for these applications in addition to fabrication and structuring of the devices will be explained in details. TGA (thermo-gravimetric analysis), dilatometer analysis, SEM (scanning electron microscopy), electronic equipment for measuring sensor performance will be extensively used for explanation of the results. It will also be shown that, compared to classical thick-film technology on alumina, LTCC allows a considerable increase in sensitivity, and is therefore better suited for the sensing of minute forces and pressures.

Abstract: During depositing a thin film as a structure layer, residual stress from thermal treatment of depositing process will cause deformation after release. Thus the yield ratio and deformation of the devices may be lowered. This work investigates the effect of sacrificial layer on deformation by residual stress causing when depositing a thin film as structure layer. A model is established by using theory of plates-and-shells to investigate the deformation caused by residual stress when the structure layers of the devices are center-anchored circular plate. Theoretically, it is found that the deformation would happen when depositing structure layer under higher temperature. And from the analysis, the thicker structure plate will cause less deformation. When the thickness of the structure layer is larger than 3μm , the maximum deformation will reduce to the order of μm. Furthermore, four cases of different sacrificial layer types and temperature distribution with effect on deformation are discussed. If the thickness of the structure layer is above 5μm, the deformation caused by residual stress is not so important. And it is found that if the thickness of structure layer is 10μm order or above, the residual stress effect on deformation can be neglected. It is found the sacrificial layer will affect the deformation. But it is found that with the same structure layer thickness, as the sacrificial layer thickness increasing, the four cases have different effect on deformation. The in-plane dimension effect is also considered. When the in-plane dimension of sacrificial layer is above 20 times of outer radius, the in-plane dimension effect is neglected and can considered as an infinite dimension.