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Book ChapterDOI

Etch Time Optimization in Bulk Silicon MEMS Devices Using a Novel Compensation Structure

01 Jan 2018-pp 33-40
TL;DR: In this article, the authors analyzed the use of different compensation structures in MEMS micromachining technology to determine the minimum release time as fast as possible where undercutting is desirable.
Abstract: The article aims to analyze the use of different compensation structures in MEMS micromachining technology to determine the minimum release time as fast as possible where undercutting is desirable A high undercutting rate is advantageous for the formation of suspended structures Thus, the implication of the present research includes analysis of corner undercutting behavior, their etching time, and etching characteristics using KOH and TMAH etchants In this paper, the effective time and etchant concentration are studied using 33% KOH at 80 °C and 25% TMAH at 85 °C It is found that wide bar with slit structure is the best compensation structure with minimum space competence
Citations
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Journal ArticleDOI
TL;DR: In this article, the simulation and experimental validation of damping for an MEMS (microelectromechanical systems) piezoresistive accelerometer with an optimized mass dimension and air gap is presented.
Abstract: This article presents the simulation and experimental validation of damping for an MEMS (micro-electromechanical systems) piezoresistive accelerometer with an optimized mass dimension and air gap. ...

7 citations

References
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Book
01 Jan 2002
TL;DR: In this paper, a comparison of top-down and bottom-up manufacturing methods for micro-manufacturing is presented, with a focus on the use of micro-processors.
Abstract: LITHOGRAPHY Introduction Historical Note: Lithography's Origins Photolithography Overview Critical Dimension, Overall Resolution, Line-Width Lithographic Sensitivity and Intrinsic Resist Sensitivity (Photochemical Quantum Efficiency) Resist Profiles Contrast and Experimental Determination of Lithographic Sensitivity Resolution in Photolithography Photolithography Resolution Enhancement Technology Beyond Moore's Law Next Generation Lithographies Emerging Lithography Technologies PATTERN TRANSFER WITH DRY ETCHING TECHNIQUES Introduction Dry Etching: Definitions and Jargon Plasmas or Discharges Physical Etching: Ion Etching or Sputtering and Ion-Beam Milling Plasma Etching (Radical Etching) Physical/Chemical Etching PATTERN TRANSFER WITH ADDITIVE TECHNIQUES Introduction Silicon Growth Doping of Si Oxidation of Silicon Physical Vapor Deposition Chemical Vapor Deposition Silk-Screening or Screen-Printing Sol-Gel Deposition Technique Doctors' Blade or Tape Casting Plasma Spraying Deposition and Arraying Methods of Organic Layers in BIOMEMS Thin versus Thick Film Deposition Selection Criteria for Deposition Method WET BULK MICROMACHINING Introduction Historical Note Silicon Crystallography Silicon As Substrate Silicon As A Mechanical Element In MEMS Wet Isotropic And Anisotropic Etching Alignment Patterns Chemical Etching Models Etching With Bias And/Or Illumination Of The Semiconductor Etch-Stop Techniques Problems With Wet Bulk Micromachining SURFACE MICROMACHINING Introduction Historical Note Mechanical Properties of Thin Films Surface Micromachining Processes Poly-Si Surface Micromachining Modifications Non-Poly-Si Surface Micromachining Modifications Materials Case Studies LIGA AND MICROMOLDING Introduction LIGA-Background LIGA and LIGA-Like Process Steps A COMPARISON OF MINIATURIZATION TECHNIQUES: TOP-DOWN AND BOTTOM-UP MANUFACTURING Introduction Absolute and Relative Tolerance in Manufacturing Historical Note: Human Manufacturing Section I: Top-Down Manufacturing Methods Section II: Bottom-Up Approaches MODELING, BRAINS, PACKAGING, SAMPLE PREPARATION AND NEW MEMS MATERIALS Introduction Modeling Brains In Miniaturization Packaging Substrate Choice SCALING, ACTUATORS, AND POWER IN MINIATURIZED SYSTEMS Introduction Scaling Actuators Fluidics Scaling In Analytical Separation Equipment Other Actuators Integrated Power MINIATURIZATION APPLICATIONS Introduction Definitions and Classification Method Decision Three OVERALL MARKET For MICROMACHINES Introduction Why Use Miniaturization Technology ? From Perception to Realization Overall MEMS Market Size MEMS Market Character MEMS Based on Si Non-Silicon MEMS MEMS versus Traditional Precision Engineering The Times are a'Changing APPENDICES Metrology Techniques WWW Linkpage Etch Rate for Si, SiO2 Summary of Top-Down Miniaturization Tools Listing of names of 20 amino acids & their chemical formulas Genetic code Summary of Materials and Their Properties for Microfabrication References for Detailed Market Information on Miniature Devices MEMS Companies Update Suggested Further Reading Glossary Symbols used in Text INDEX Each chapter also contains sections of examples and problems

1,930 citations

Journal ArticleDOI
TL;DR: In this article, a review of the fabrication techniques for the realization of convex corners in silicon bulk micromachining technology is presented, which is restricted to the wet anisotropic etching process.
Abstract: Silicon bulk micromachining using the wet anisotropic etching process is widely employed for the development of commercial products such as an inkjet printer head, a pressure sensor, accelerometers, infrared sensors, etc using (1 0 0) silicon wafers. In wet anisotropic etching, the resultant shape and size of the microstructures are restricted by crystallographic properties of silicon. If structures such as seismic mass in an accelerometer are required to be created, convex corners will emerge in the etching process. Considerable deformation occurs at convex corners resulting in poor control on the shape and size of the microstructure. Various methods/techniques are developed to overcome the problem of undercutting at convex corners in a (1 0 0) silicon wafer. Here, we have reviewed the fabrication techniques for the realization of convex corners in silicon bulk micromachining technology. The review is restricted to the wet anisotropic etching process which is usually performed in potassium hydroxide solution, ethylenediamine pyrocatechol solution, tetramethylammonium hydroxide, etc. The corner compensation method is the most widely used technique for the fabrication of convex corners. Various types of corner compensating design have been proposed by different research groups. The corner compensation method gives nearly sharp corners. Recently developed techniques, which do not use any compensating design, give perfect convex corners. The limitations and advantages of all the techniques have been discussed. (Some figures in this article are in colour only in the electronic version)

98 citations

Journal ArticleDOI
TL;DR: In this paper, the fabrication techniques of convex corner on {100} and {110} silicon wafers using anisotropic wet chemical etching are discussed. And the pros and cons of all these techniques are discussed as well as the shape and size of the compensating design strongly depend on the type of etchant, etching depth and the orientation of wafer surface.
Abstract: Wet anisotropic etching based silicon micromachining is an important technique to fabricate freestanding (e.g. cantilever) and fixed (e.g. cavity) structures on different orientation silicon wafers for various applications in microelectromechanical systems (MEMS). {111} planes are the slowest etch rate plane in all kinds of anisotropic etchants and therefore, a prolonged etching always leads to the appearance of {111} facets at the sidewalls of the fabricated structures. In wet anisotropic etching, undercutting occurs at the extruded corners and the curved edges of the mask patterns on the wafer surface. The rate of undercutting depends upon the type of etchant and the shape of mask edges and corners. Furthermore, the undercutting takes place at the straight edges if they do not contain {111} planes. {100} and {110} silicon wafers are most widely used in MEMS as well as microelectronics fabrication. This paper reviews the fabrication techniques of convex corner on {100} and {110} silicon wafers using anisotropic wet chemical etching. Fabrication methods are classified mainly into two major categories: corner compensation method and two-steps etching technique. In corner compensation method, extra mask pattern is added at the corner. Due to extra geometry, etching is delayed at the convex corner and hence the technique relies on time delayed etching. The shape and size of the compensating design strongly depends on the type of etchant, etching depth and the orientation of wafer surface. In this paper, various kinds of compensating designs published so far are discussed. Two-step etching method is employed for the fabrication of perfect convex corners. Since the perfectly sharp convex corner is formed by the intersection of {111} planes, each step of etching defines one of the facets of convex corners. In this method, two different ways are employed to perform the etching process and therefore can be subdivided into two parts. In one case, lithography step is performed after the first step of etching, while in the second case, all lithography steps are carried out before the etching process, but local oxidation of silicon (LOCOS) process is done after the first step of etching. The pros and cons of all techniques are discussed.

86 citations

Journal ArticleDOI
TL;DR: In this article, three ion-typed surfactants, including anionic SDSS, cationic ASPEG and non-ionic PEG, which are powerful wetting agents in electroforming, were added to 30.wt.% KOH and 10.1% TMAH solutions.
Abstract: Three ion-typed surfactants, including anionic SDSS, cationic ASPEG and non-ionic PEG, which are powerful wetting agents in electroforming, were added to 30 wt.% KOH and 10 wt.% TMAH solutions to evaluate the silicon anisotropic etching properties of the (1 0 0) silicon plane without agitation and no IPA additive. The results indicate that the surfactant ion-types are not the main determinants of the silicon anisotropic etching properties in KOH and TMAH solutions. The wetting capacity of the etchants causes the efficacies of the etchants on the roughness to follow the order anionic SDSS, cationic ASPEG, non-ionic PEG and pure solution in KOH solutions, and the order cationic ASPEG, non-ionic PEG, pure solution and anionic SDSS in TMAH solutions, especially at higher etching temperatures. Moreover, the chemical activities of etchants differ so that the etching rates follow the order anionic SDSS, pure solution, non-ionic PEG and cationic ASPEG in KOH solutions, and the order anionic SDSS, pure solution, cationic ASPEG and non-ionic PEG in TMAH solutions at a given etching temperature. Anionic SDSS has the highest etching rate of 5.4 μm/min and the lowest surface roughness of 7.5 nm, which are about 1.69 times higher and 7.87 times lower, respectively, than those obtained in pure KOH solution. The cationic ASPEG has a reasonable etching rate of 0.7 μm/min and the lowest surface roughness of 4 nm in TMAH solutions for etching temperature of 100 °C. Furthermore, the surfactants used here were demonstrated to allow the utilization of usual mask materials and anionic SDSS can even increase the selectivity of silicon dissolution toward silicon dioxide in KOH solutions. A drastic reduction of the undercutting of the convex corners is obtained in TMAH solutions with non-ionic PEG surfactant. This finding reveals that the addition of non-ionic PEG to TMAH solutions is ideal when accurate profiles are required without extremely deep etching.

82 citations

Journal ArticleDOI
TL;DR: In this paper, a modified convex corner compensation with a 〈100〉 bar for (100) silicon rectangular etching has been investigated, and the theoretical analysis and the experimental result are given in this paper.
Abstract: The method of convex corner compensation with a 〈100〉 bar for (100) silicon rectangular etching proposed by Mayer et al. ( J. Electrochem. Soc., 137 (1990) 3947–3951) has been investigated. Limitations of the method are discussed, and a modified method is put forward. Both the theoretical analysis and the experimental result are given in this paper.

69 citations