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Kazuo Sato - One of the best experts on this subject based on the ideXlab platform.

  • High speed silicon wet Anisotropic Etching for applications in bulk micromachining: a review
    Micro and Nano Systems Letters, 2021
    Co-Authors: Prem Pal, Veerla Swarnalatha, Avvaru Venkata Narasimha Rao, Ashok Kumar Pandey, Hiroshi Tanaka, Kazuo Sato
    Abstract:

    Wet Anisotropic Etching is extensively employed in silicon bulk micromachining to fabricate microstructures for various applications in the field of microelectromechanical systems (MEMS). In addition, it is most widely used for surface texturing to minimize the reflectance of light to improve the efficiency of crystalline silicon solar cells. In wet bulk micromachining, the etch rate is a major factor that affects the throughput. Slower etch rate increases the fabrication time and therefore is of great concern in MEMS industry where wet Anisotropic Etching is employed to perform the silicon bulk micromachining, especially to fabricate deep cavities and freestanding microstructures by removal of underneath material through undercutting process. Several methods have been proposed to increase the etch rate of silicon in wet Anisotropic etchants either by physical means (e.g. agitation, microwave irradiation) or chemically by incorporation of additives. The ultrasonic agitation during Etching and microwave irradiation on the etchants increase the etch rate. However, ultrasonic method may rupture the fragile structures and microwave irradiation causes irradiation damage to the structures. Another method is to increase the Etching temperature towards the boiling point of the etchant. The Etching characteristics of pure potassium hydroxide solution (KOH) is studied near the boiling point of KOH, while surfactant added tetramethylammonium hydroxide (TMAH) is investigated at higher temperature to increase the etch rate. Both these studies have shown a potential way of increasing the etch rate by elevating the temperature of the etchants to its boiling point, which is a function of concentration of etch solution. The effect of various kinds of additives on the etch rate of silicon is investigated in TMAH and KOH. In this paper, the additives which improve the etch rate have been discussed. Recently the effect of hydroxylamine (NH_2OH) on the Etching characteristics of TMAH and KOH is investigated in detail. The concentration of NH_2OH in TMAH/KOH is varied to optimize the etchant composition to obtain improved Etching characteristics especially the etch rate and undercutting which are important parameters for increasing throughput. In this article, different methods explored to improve the etch rate of silicon have been discussed so that the researchers/scientists/engineers can get the details of these methods in a single reference.

  • removal probability function for kinetic monte carlo simulations of Anisotropic Etching of silicon in alkaline etchants containing additives
    Sensors and Actuators A-physical, 2015
    Co-Authors: Hui Zhang, Yan Xing, M A Gosalvez, Kazuo Sato
    Abstract:

    Abstract A new Surfactant-based Removal Probability Function (S-RPF) is proposed to perform Kinetic Monte Carlo simulations of Anisotropic Etching of silicon in alkaline solutions containing additives, such as tetramethyl ammonium hydroxide (TMAH) or potassium hydroxide (KOH) with small amounts of surfactants (e.g., Triton) and/or alcohols (e.g., Isopropanol = IPA). The S-RPF is built as the product of (i) a modified removal probability function (M-RPF), for pure etchants, and (ii) an additive inhibition term (I-RPF), which describes the orientation-dependent reduction in certain etch rates due to the selective adsorption of the additive on particular silicon surfaces. By construction these functions depend only on a few parameters, whose values are determined by an evolutionary algorithm (EA), which minimizes the differences between the experimental and simulated etch rates for a small set of silicon surfaces. In this respect, the paper introduces a transformation matrix to constrain the evolutionary search space, thus accelerating the convergence for both the M-RPF and I-RPF parameters. The simulated etch rates for numerous silicon orientations in TMAH + trion at different temperatures as well as KOH + IPA show good agreement with the experimental data. Compared to previous studies, the new S-RPF model describes the anisotropy at local etch rate maxima and minima around Si(1 0 0) and Si(1 1 0) with much better accuracy. The simulation of three-dimensional microstructures confirms the validity of the new S-RPF model for MEMS fabrication in alkaline etchants containing additives.

  • forty five degree micromirror fabrication using silicon Anisotropic Etching with surfactant added tetramethylammonium hydroxide solution
    Japanese Journal of Applied Physics, 2010
    Co-Authors: Hiroyuki Yagyu, Tadahiro Yamaji, Makoto Nishimura, Kazuo Sato
    Abstract:

    Flat and smooth 45° micromirrors were successfully fabricated on a 4-in. silicon wafer by means of wet Anisotropic Etching at the industrially practical temperature of 80 °C using tetramethylammonium hydroxide (TMAH) solution with added NCW-1002, a nonionic surfactant with little environmental load. The effects of the TMAH concentration and the amount of NCW-1002 added were extensively investigated, and it was found that a high TMAH concentration (25 wt %) and a very low amount of NCW-1002, approximately 10 vol ppm, are the optimum conditions to fabricate optically smooth and geometrically flat micromirrors. The mechanism underlying the effects of the concentration of the surfactant is discussed in relation to the clouding point of the surfactant-added TMAH solution.

  • roughening of single crystal silicon surface etched by koh water solution
    Sensors and Actuators A-physical, 1999
    Co-Authors: Kazuo Sato, Mitsuhiro Shikida, Takashi Yamashiro, Masaki Tsunekawa
    Abstract:

    We investigated roughening of single-crystal silicon surface during chemical Anisotropic Etching using KOH water solution. The change in roughness strongly depends on the crystallographic orientation of the silicon. We plotted a map showing roughness distribution as a function of orientation. A smooth surface appears in a region including the (100), (211), and (311) planes. A very rough surface appears in a region including the (320) and (210) planes. It was observed that the roughened surface shows facet textures composed of certain crystallographic planes. We further studied the effects of KOH concentration and Etching temperature. The roughness of (110) plane decreases with an increase in KOH concentration and is independent of the Etching temperature.

  • characterization of orientation dependent Etching properties of single crystal silicon effects of koh concentration
    Sensors and Actuators A-physical, 1998
    Co-Authors: Kazuo Sato, Mitsuhiro Shikida, Takashi Yamashiro, Kazuo Asaumi, Yasuroh Iriye, Yoshihiro Matsushima, Masaharu Yamamoto
    Abstract:

    Abstract We have evaluated the orientation dependence in chemical Anisotropic Etching of single-crystal silicon. Etch rates for a number of crystallographic orientations have been measured for a wide range of Etching conditions, including KOH concentrations of 30 to 50% and temperatures of 40 to 90 °C. Though the etchants all consist of the same components KOH and water, the orientation dependence varies considerably with change in etchant temperature and concentration. The resulting etch-rate database allows numerical prediction of etch profiles of silicon, necessary for the process design of microstructures. Changing the KOH concentration yields different etch profiles both analytically and experimentally.

Ching-chung Tsai - One of the best experts on this subject based on the ideXlab platform.

  • use of Anisotropic laser Etching to the top n gan layer to alleviate current crowding effect in vertical structured gan based light emitting diodes
    Applied Physics Letters, 2007
    Co-Authors: Tron-min Chen, Shui-jinn Wang, Kai-ming Uang, Shiuelung Chen, Weichih Tsai, Weichi Lee, Ching-chung Tsai
    Abstract:

    To equalize the resistance of all possible current paths in regular vertical-conducting metal-substrate GaN-based light-emitting diodes (VM-LEDs), an Anisotropic laser Etching to the surface layer (n-GaN) of 40mil VM-LEDs for improving light emission uniformity and light output power is proposed and demonstrated. The feasibility of the proposed scheme was verified by current and light emission distribution as well as light extraction rate simulations. In conjunction with a nonuniform excimer laser beam irradiation through a mask and rotation of the epitaxy wafer, VM-LEDs with a concave-surface n-GaN layer were also fabricated. Typical improvement in light output power by 38%–26% at an injection current of 350mA as compared to the one without Anisotropic Etching has been obtained.

Shuji Nakamura - One of the best experts on this subject based on the ideXlab platform.

  • increase in the extraction efficiency of gan based light emitting diodes via surface roughening
    Applied Physics Letters, 2004
    Co-Authors: Tetsuo Fujii, Yan Gao, Rajat Sharma, Steven P Denbaars, Shuji Nakamura
    Abstract:

    Roughened surfaces of light-emitting diodes (LEDs) provide substantial improvement in light extraction efficiency. By using the laser-lift-off technique followed by an Anisotropic Etching process to roughen the surface, an n-side-up GaN-based LED with a hexagonal “conelike” surface has been fabricated. The enhancement of the LED output power depends on the surface conditions. The output power of an optimally roughened surface LED shows a twofold to threefold increase compared to that of an LED before surface roughening.

Michael Curt Elwenspoek - One of the best experts on this subject based on the ideXlab platform.

  • Anisotropic reactive ion Etching of silicon using sf 6 o 2 chf 3 gas mixtures
    Journal of The Electrochemical Society, 1995
    Co-Authors: R Legtenberg, Henricus V Jansen, Meint J De Boer, Michael Curt Elwenspoek
    Abstract:

    Reactive ion Etching of silicon in an RF parallel plate system, using SF6/O2/CHF3, plasmas has been studied. Etchingbehavior was found to be a function of loading, the cathode material, and the mask material. Good results with respect toreproducibility and uniformity have been obtained by using silicon as the cathode material and silicon dioxide as themasking material for mask designs where most of the surface is etched. Etch rate, selectivity, anisotropy, and self-biasvoltage have been examined as a function of SF6 flow, O2 flow, CHF3 flow, pressure, and the RF power, using responsesurface methodology, in order to optimize Anisotropic Etching conditions. The effects of the variables on the measuredresponses are discussed. The Anisotropic etch mechanism is based on ion-enhanced inhibitor Etching. SF6 provides thereactive neutral Etching species, O2 supplies the inhibitor film forming species, and SF6 and CHF3 generate ion species thatsuppress the formation of the inhibitor film at horizontal surfaces. Anisotropic Etching of high aspect ratio structures withsmooth etch surfaces has been achieved. The technique is applied to the fabrication of three-dimensional micromechanicalstructures.

  • Anisotropic reactive ion Etching of silicon using sf6 02 chf3 gas mixtures
    Journal of The Electrochemical Society, 1995
    Co-Authors: R Legtenberg, Henricus V Jansen, Meint J De Boer, Michael Curt Elwenspoek
    Abstract:

    Reactive ion Etching of silicon in an RF parallel plate system, using SF6/O2/CHF3, plasmas has been studied. Etchingbehavior was found to be a function of loading, the cathode material, and the mask material. Good results with respect toreproducibility and uniformity have been obtained by using silicon as the cathode material and silicon dioxide as themasking material for mask designs where most of the surface is etched. Etch rate, selectivity, anisotropy, and self-biasvoltage have been examined as a function of SF6 flow, O2 flow, CHF3 flow, pressure, and the RF power, using responsesurface methodology, in order to optimize Anisotropic Etching conditions. The effects of the variables on the measuredresponses are discussed. The Anisotropic etch mechanism is based on ion-enhanced inhibitor Etching. SF6 provides thereactive neutral Etching species, O2 supplies the inhibitor film forming species, and SF6 and CHF3 generate ion species thatsuppress the formation of the inhibitor film at horizontal surfaces. Anisotropic Etching of high aspect ratio structures withsmooth etch surfaces has been achieved. The technique is applied to the fabrication of three-dimensional micromechanicalstructures.

Irena Zubel - One of the best experts on this subject based on the ideXlab platform.

  • silicon Anisotropic Etching in alkaline solutions iv the effect of organic and inorganic agents on silicon Anisotropic Etching process
    Sensors and Actuators A-physical, 2001
    Co-Authors: Irena Zubel, Irena Barycka, Kamilla Kotowska, M Kramkowska
    Abstract:

    Abstract Silicon Anisotropic Etching process in organic and inorganic solutions has been studied. Experimental results on silicon Etching in KOH and TMAH solutions with and without IPA addition have been presented. Etching rate curves versus solution concentration were plotted for different crystallographic planes with special emphasis on high-indexed ones. A comparison of our own experimental results with the results of other authors, concerning silicon Anisotropic Etching process in hydroxides of other metals from the first group of periodic table, revealed that their ions and molecules contained in the solution play an important role in the process and influence its anisotropy. The observations led us to some general conclusions regarding physical and chemical phenomena associated with the silicon Anisotropic Etching. We have suggested that the lowering of Etching rates is connected with adsorption of cations and organic additions on some crystallographic planes.

  • silicon Anisotropic Etching in koh isopropanol etchant
    Sensors and Actuators A-physical, 1995
    Co-Authors: Irena Barycka, Irena Zubel
    Abstract:

    Abstract Silicon monocrystalline wafers of (100), (110) and (111) orientations are etched in KOH-isopropanol solution. SiO 2 layers patterned with a few types of figures are used as a mask for the Etching of holes or islands. The planes that disappear and develop during the Etching process are pointed out. the shapes of the etched figures are compared with the crystallographic description of silicon structure.