Papers by Keyword: Wet Etching

Abstract: In this paper, we present our ongoing work on developing a microfabricated XYZ stage-needle arrayed single crystal silicon (SCS) structure for cellular delivery and surgery. We discuss the device design and working principle based on electrostatic actuation. We also briefly discuss our microfabrication process flow and show some preliminary results of fabricating arrays of microneedles that are 250 µm long and 5 µm at the tip diameter.

Abstract: Micro V-groove is an important optical component in the packaging of optoelectronic devices, which holds the position of the optical fibers. The micro V-groove can be fabricated by three main techniques on different materials: wet etching, ultra precision machining and molding press. The main parameters, which determine the micro V-groove quality, include core pitch, surface roughness and cured adhesive height. In this paper, three fabrication techniques are discussed to address the future needs of the next-generation optical fiber communication technology. The advantages and disadvantages of each fabrication technique are discussed with the quality issues. The findings can be served as guides for the materials and fabrication in micro V-groove in optoelectronic packaging.

Abstract: The purpose of this study is to propose and apply a MEMS-based gas chromatography (GC) device comprising a miniature serpentine column. A 2 m long, 200 μm wide and 250 μm deep column was fabricated using a wet etching process and bonded to a Pyrex cover plate. After the GC column was coated with Carbowax 20M as the stationary phase, the concentrations of benzene, toluene, Ethylbenzene and m-Xylene were successfully detected in the mixed sample. The leakage test and mixed gas separation test achieved a useful separation result for Ethylbenzene-Xylene and Benzene-Toluen mixture at a 17.1 cm/s linear flow rate in a GC chip column.

Abstract: A wet etching method for preparing silicon nanowires on silicon substrates at near room temperature is presented. The effect of experiment parameter on the silver nanoparticle forming including concentration of AgNO₃, immersing time and solution temperature, and the effect of etching time on the length of silicon nanowires are investigated. It is concluded that solution temperature has more impact to diameter of silicon nanowires than concentration of AgNO₃ and immersing time and longer etching time may result in longer silicon nanowires.

Abstract: This paper presents a simple but reliable fabrication process for microfluidic devices on glass substrate using wet etching technology. Instead of using expensive Pyrex glasses as substrates and depositing expensive metal or polysilicon/amorphous silicon as etch masks in conventional method, glass slide is used as substrate and a single-layer negative photoresist RFJ-220 is used as the etching mask. The etch rates, generation of defects, undercut ratio and surface roughness are studied. In order to achieve high etching depth and smooth surface, buffered oxide etching with hydrochloric acid as additive is proposed. By proper cleaning and long-time hard baking, the undercut ratio can approach to 1. An 110μm depth microchannel with smooth surface is achieved. This fabrication process leads to a considerable reduction of process steps, fabrication time and material consumption. With this technique, we successfully fabricated a microfluidic device, which is used in the capture of hepatoma cells HepG2.

Abstract: Warpage on the backside of silicon wafer after thinning process is examined. The thinning process includes back-grinding (BG) and wet chemical etching (WCE). Results of wafer warpage were compared to sub-surface damage from Transmission Electron Microscopy (TEM) analysis and showed that sub-surface damage on the backside of the silicon 100 would induce high wafer warpage, and reduced wafer strength. Further studies from surface roughness and topography of each surface finish is obtained by Atomic Force Microscopy (AFM) and SEM show that low surface roughness is in accordance with smooth surface condition, which comes after the wet etching process.

Abstract: This paper presents a simple process technique for the fabrication of valveless micro-pumps. The process design utilizes standard MEMS process using double-sided anisotropic silicon wet etching process with an additional adhesive bonding technique. The diffuser and nozzle element of the pump with depth of 50 µm, as well as a 150 µm thick silicon membrane are designed and fabricated using only 3 patterning process steps. A piezoelectric plate working at the frequency range from 0.1 kHz to 2 kHz is bonded on to the back side of the silicon membrane to create the membrane actuation. The patterning process of thick photoresist used as the adhesive layer for the substrate bonding is also discussed in detail. The fluid flow is observed and the process reproducibility is proven which show a good prospect for the future development of miniaturized valveless pump for biomedical application.

Abstract: We have proposed a new wet etching recipe using molten KOH and Na2O2 as the etchant (“KN etching”) for dislocation revelation in highly doped n-type 4H-SiC (n+-4H-SiC). Threading screw dislocations (TSDs) and threading edge dislocations (TEDs) have been clearly revealed as hexagonal etch pits differing in pit sizes, and basal plane dislocations (BPDs) as seashell-shaped pits. This new etching recipe has provided a solution to the problem that conventional KOH etching is not effective for dislocation identification in 4H-SiC if the electron concentration is high (>mid-1018 cm-3). We have investigated the effect of SiC off-cut angle on KN etching and it has been shown that the “KN etching” is applicable for the n+-SiC substrate with off-angle from 0o to 8o.

Abstract: With the development of economy and society, more and more energy is needed to meet the requirement of industries and social life. It is necessary to find new types of energy that is clear, high effective and non-polluted. Although wet etching is widely used in industries to prepare the silicon surface texture, the etching process is stochastic and the influence light trapping. Many efforts have been made such as adjusting the proportion of different acids, to improve the quality of silicon surface by wet etching, the result does not meet the ideal requirement by now. In this paper, a new approach is presented to prepare the surface texturing. By combining wet etching and ultrasonic vibration, the sodium or acid molecular motion can be controlled, and the pyramid structure in silicon surface can be made regular.

Abstract: With the development of economy and society, more and more energy is needed to meet the requirement of industries and social life. It is necessary to find new types of energy that is clear, high effective and non-polluted. Although wet etching is widely used in industries to prepare the silicon surface texture, the etching process is stochastic and the influence light is trapping. Many efforts have been made, such as adjusting the proportion of different acids, to improve the quality of silicon surface by wet etching, the effectiveness is still limited. In this paper, a new approach is presented to prepare the surface texturing. By combining wet etching and ultrasonic vibration, the sodium or acid molecular motion can be controlled, and the pyramid structure in silicon surface can be made regular.