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Kazuo Sato - One of the best experts on this subject based on the ideXlab platform.
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High speed silicon wet anisotropic Etching for applications in bulk micromachining: a review
Micro and Nano Systems Letters, 2021Co-Authors: Prem Pal, Veerla Swarnalatha, Avvaru Venkata Narasimha Rao, Ashok Kumar Pandey, Hiroshi Tanaka, Kazuo SatoAbstract: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.
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experimental procurement of the complete 3d Etch Rate distribution of si in anisotropic Etchants based on vertically micromachined wagon wheel samples
Journal of Micromechanics and Microengineering, 2011Co-Authors: Miguel A. Gosálvez, Nestor Ferrando, Hirotaka Hida, Kazuo SatoAbstract:This is part I of a series of two papers dedicated to the presentation of a novel, large throughput, experimental procedure to determine the three-dimensional distribution of the Etch Rate of silicon in a wide range of anisotropic Etchants, including a total of 30 different Etching conditions in KOH, KOH+IPA, TMAH and TMAH+Triton solutions at various concentrations and temperatures. The method is based on the use of previously reported, vertically micromachined wagon wheels (WWs) (Wind and Hines 2000 Surf. Sci. 460 21–38; Nguyen and Elwenspoek 2007 J. Electrochem. Soc. 154 D684–91), focusing on speeding up the Etch Rate extraction process for each WW by combining macrophotography and image processing procedures. The proposed procedure positions the WWs as a realistic alternative to the traditional hemispherical specimen. The obtained, extensive Etch Rate database is used to perform wet Etching simulations of advanced systems, showing good agreement with the experimental counterparts. In part II of this series (Gosalvez et al J. Micromech. Microeng. 21 125008), we provide a theoretical analysis of the Etched spoke shapes, a detailed comparison to the Etch Rates from previous studies and a self-consistency study of the measured Etch Rates against maximum theoretical values derived from the spoke shape analysis.
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reliability assessment of the complete 3d Etch Rate distribution of si in anisotropic Etchants based on vertically micromachined wagon wheel samples
Journal of Micromechanics and Microengineering, 2011Co-Authors: Miguel A. Gosálvez, Nestor Ferrando, Kazuo SatoAbstract:As a sequel to part I (Gosalvez et al J. Micromech. Microeng. 12 125007), the present paper is part II of a series of two papers dedicated to the presentation of a novel, large-throughput, experimental procedure to determine the complete three-dimensional orientation dependence of the Etch Rate of silicon by using vertically micromachined wagon wheel samples. While the first part provides the experimental details and compares the results to realistic simulations, the present paper focuses on characterizing the reliability of the obtained Etch Rates. For this purpose, the shape of the Etched structures is analyzed and corresponding formulas are derived, enabling the estimation of an upper bound to the measured Etch Rates. It is shown that the measured Etch Rates remain below this limit, strongly indicating that the observed wedge retraction values are consistent with the assumed geometrical shape of the wedges. An exception to this rule are the Etch Rates of {1 1 0} obtained from 1 1 0-oriented wafers, which are systematically larger. This deviation is explained by a kinetic acceleration process due to the small size of the step-flow structures that are formed on the affected wagon wheel spokes. The comparison to previous experiments indicates that the proposed method provides similar or even more accuRate Etch Rates for some of the Etchants with a more affordable and less labor-intensive approach.
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reconstructing the 3d Etch Rate distribution of silicon in anisotropic Etchants using data from vicinal 1 0 0 1 1 0 and 1 1 1 surfaces
Journal of Micromechanics and Microengineering, 2011Co-Authors: Miguel A. Gosálvez, Kazuo SatoAbstract:We consider the reconstruction of the complete three-dimensional distribution of Etch Rates for crystalline silicon in a total of six markedly different Etching conditions. The procedure is based on data points that, on the unit sphere, are located along the high-symmetry lines connecting the three main surface orientations Si{1 1 1}, Si{1 1 0} and Si{1 0 0}. Novel, compact formulas are presented in order to perform trilinear, triquadratic and higher order interpolations in h k l space. A wide variety of surface triangulations and tessellations are proposed in order to apply the trilinear and higher order formulas. A statistical analysis concludes that trilinear interpolation over three particular triangulations, and triquartic interpolation over a specific tessellation provide the best reconstructions for the six considered Etching conditions. By combining the three triangulations and tessellation using a weighted average, the mean error is found to be less than 13% for reconstructions involving noisy experimental Etch Rates, while it decreases to 2–5% for less unruly distributions. The results strongly indicate that the complete orientation dependence of the Etch Rate can be derived from an alternative, more feasible experiment than the traditional hemispherical specimen.
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orientation and concentration dependent surfactant adsorption on silicon in aqueous alkaline solutions explaining the changes in the Etch Rate roughness and undercutting for mems applications
Journal of Micromechanics and Microengineering, 2009Co-Authors: Miguel A. Gosálvez, Kazuo Sato, Bin Tang, Prem Pal, Yasuo Kimura, Kenichi IshibashiAbstract:We combine spectroscopic ellipsometry (SE), Fourier transform infrared spectroscopy (FT-IR), kinetic Monte Carlo simulations (KMC) and convex corner undercutting analysis in order to characterize and explain the effect of the addition of small amounts of surfactant in alkaline aqueous solutions, such as Triton X-100 in tetra methyl ammonium hydroxide (TMAH). We propose that the surfactant is adsorbed at the silicon–Etchant interface as a thin layer, acting as a filter that modeRates the surface reactivity by reducing the amount of reactant molecules that reach the surface. According to the SE and FT-IR measurements, the thickness of the adsorbed layer is an orientation- and concentration-dependent quantity, mostly due to the orientation dependence of the surface density of H-terminations and the concentration dependence of the relative Rates of the underlying oxidation and Etching reactions, which have a direct impact on the number of OH terminations. For partial OH coverage of the surface, the hydration of the OH group effectively acts as an anchoring location for the hydration shell of a surfactant molecule, thus enabling the formation of hydration bridges that amplify the adsorption density of the surfactant. At high concentration, the model explains the large reduction in the Etch Rate of the exact and vicinal Si{1 1 0} surfaces, and the small changes in the Etch Rates for the exact and vicinal Si{1 0 0} surfaces. At low concentration, it explains how the Etch Rate for both families is significantly reduced. The orientation and concentration dependence of the surfactant adsorption explains the dramatic differences in the micron-scale wet-Etched patterns obtained using TMAH and TMAH+Triton for microelectromechanical systems applications.
T Bandyopadhyay - One of the best experts on this subject based on the ideXlab platform.
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study of variations in structural optical parameters and bulk Etch Rate of cr 39 polymer due to electron irradiation
Journal of Applied Physics, 2016Co-Authors: G S Sahoo, S P Tripathy, D S Joshi, T BandyopadhyayAbstract:In this work, electron induced modifications on the bulk Etch Rate, structural and optical parameters of CR-39 polymer were studied using gravimetric, FTIR (Fourier Transform Infrared) and UV–vis (Ultraviolet–Visible) techniques, respectively. CR-39 samples were irradiated with 10 MeV electron beam for different durations to have the absorbed doses of 1, 10, 550, 5500, 16 500, and 55 000 kGy. From the FTIR analysis, the peak intensities at different bands were found to be changing with electron dose. A few peaks were observed to shift at high electron doses. From the UV-vis analysis, the optical band gaps for both direct and indirect transitions were found to be decreasing with the increase in electron dose whereas the opacity, number of carbon atoms in conjugation length, and the number of carbon atoms per cluster were found to be increasing. The bulk Etch Rate was observed to be increasing with the electron dose. The primary objective of this investigation was to study the response of CR-39 to high elec...
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study of variations in structural optical parameters and bulk Etch Rate of cr 39 polymer due to electron irradiation
Journal of Applied Physics, 2016Co-Authors: G S Sahoo, S P Tripathy, D S Joshi, T BandyopadhyayAbstract:In this work, electron induced modifications on the bulk Etch Rate, structural and optical parameters of CR-39 polymer were studied using gravimetric, FTIR (Fourier Transform Infrared) and UV–vis (Ultraviolet–Visible) techniques, respectively. CR-39 samples were irradiated with 10 MeV electron beam for different durations to have the absorbed doses of 1, 10, 550, 5500, 16 500, and 55 000 kGy. From the FTIR analysis, the peak intensities at different bands were found to be changing with electron dose. A few peaks were observed to shift at high electron doses. From the UV-vis analysis, the optical band gaps for both direct and indirect transitions were found to be decreasing with the increase in electron dose whereas the opacity, number of carbon atoms in conjugation length, and the number of carbon atoms per cluster were found to be increasing. The bulk Etch Rate was observed to be increasing with the electron dose. The primary objective of this investigation was to study the response of CR-39 to high electron doses and to determine a suitable pre-irradiation condition. The results indicated that, the CR-39 pre-irradiated with electrons can have better sensitivity and thus can be potentially applied for neutron dosimetry.
Masahiko Aihara - One of the best experts on this subject based on the ideXlab platform.
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Etch Rate and surface morphology of polycrystalline β silicon carbide using chlorine trifluoride gas
Thin Solid Films, 2006Co-Authors: Hitoshi Habuka, Satoko Oda, Yasushi Fukai, Katsuya Fukae, Takashi Takeuchi, Masahiko AiharaAbstract:Abstract Etch Rates of polycrystalline β-silicon carbide (SiC) substRate in a wide range from less than one to more than 10 μm/min are obtained using chlorine trifluoride gas in ambient nitrogen at 673–973 K and atmospheric pressure in a horizontal reactor. Over the chlorine trifluoride gas concentrations of 10–100% used in this study, the Etch Rate increases at the substRate temperatures between 673 and 773 K. Additionally, the Etch Rate at temperatures higher than 773 K is independent of the substRate temperature, similar to the one obtained using chlorine trifluoride gas concentration of 100%. The root means square roughness of Etched surface tends to be small at high temperatures and high chlorine trifluoride gas concentrations. The polycrystalline β-SiC Etch Rate can be adjusted using a combination of gas flow Rate, chlorine trifluoride gas concentration, and substRate temperature in order to obtain surfaces suitable for various purposes.
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silicon carbide Etching using chlorine trifluoride gas
Japanese Journal of Applied Physics, 2005Co-Authors: Hitoshi Habuka, Satoko Oda, Yasushi Fukai, Katsuya Fukae, Takashi Takeuchi, Masahiko AiharaAbstract:The Etch Rate, chemical reactions and Etched surface of β-silicon carbide are studied in detail using chlorine trifluoride gas. The Etch Rate is greater than 10 µm min-1 at 723 K with a flow Rate of 0.1 l min-1 at atmospheric pressure in a horizontal reactor. The maximum Etch Rate at a substRate temperature of 773 K is 40 µm min-1 with a flow Rate of 0.25 l min-1. The step-like pattern that initially exists on the β-silicon carbide surface tends to be smoothed; the root-mean-square surface roughness decreases from its initial value of 5 µm to 1 µm within 15 min; this minimum value is maintained for more than 15 min. Therefore, chlorine trifluoride gas is considered to have a large Etch Rate for β-silicon carbide associated with making a rough surface smooth.
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silicon Etch Rate using chlorine trifluoride
Journal of The Electrochemical Society, 2004Co-Authors: Hitoshi Habuka, Takahiro Sukenobu, Hideyuki Koda, Takashi Takeuchi, Masahiko AiharaAbstract:The mechanism causing the behavior of the silicon Etch Rate using chlorine trifluoride gas, which appears to be independent of the substRate temperature in a horizontal cold-wall reactor, is clarified by means of numerical calculations taking into account the surface chemical reaction Rate on the silicon substRate surface and the transport phenomena in the entire reactor. The activation energy of the overall Rate constant of its surface chemical reaction is evaluated, for the first time, to be 6000 J mol -1 , which can reproduce the Etch Rate and its behavior obtained by the measurement. With increasing substRate temperature in the reactor, the effect of a modeRate increase in both the diffusivity of chlorine trifluoride gas and the overall Rate constant is considered to be compensated by the decrease in the chlorine trifluoride gas concentration due to the gas volume expansion in the gas phase above the substRate. Therefore, the Etch Rate can be independent of the substRate temperature.
Hitoshi Habuka - One of the best experts on this subject based on the ideXlab platform.
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4h silicon carbide Etching using chlorine trifluoride gas
Materials Science Forum, 2008Co-Authors: Hitoshi Habuka, Yutaka Miura, Yusuke Katsumi, Yasushi Fukai, Tomohisa Kato, Hajime Okumura, Keiko Tanaka, Takaya Fukae, Yuan Gao, Kazuo AraiAbstract:The Etching technology for 4H-silicon carbide (SiC) was studied using ClF 3 gas at 673-973K, 100 % and atmospheric pressure in a horizontal reactor. The Etch Rate, greater than 10 um/min, can be obtained for both the C-face and Si-face at substRate temperatures higher than 723 K. The Etch Rate increases with the increasing ClF 3 gas flow Rate. The Etch Rate of the Si-face is smaller than that of the C-face. The Etched surface of the Si-face shows many hexagonal-shaped Etch pits. The C-face after the Etching is very smooth with a very small number of round shaped shallow pits. The average roughness of the Etched surface tends to be small at the higher temperatures.
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Determination of Etch Rate Behavior of 4H–SiC Using Chlorine Trifluoride Gas
Japanese Journal of Applied Physics, 2007Co-Authors: Yutaka Miura, Hitoshi Habuka, Yusuke Katsumi, Satoko Oda, Yasushi Fukai, Katsuya Fukae, Tomohisa Kato, Hajime Okumura, Kazuo AraiAbstract:The Etch Rate of single-crystalline 4H–SiC is studied using chlorine trifluoride gas at 673–973 K and atmospheric pressure in a cold wall horizontal reactor. The 4H–SiC Etch Rate can be higher than 10 µm/min at substRate temperatures higher than 723 K. The Etch Rate increases with the chlorine trifluoride gas flow Rate. The Etch Rate is calculated by taking into account the transport phenomena in the reactor including the chemical reaction at the substRate surface. The flat Etch Rate at the higher substRate temperatures is caused mainly by the relationship between the transport Rate and the surface chemical reaction Rate of chlorine trifluoride gas.
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Etch Rate and surface morphology of polycrystalline β silicon carbide using chlorine trifluoride gas
Thin Solid Films, 2006Co-Authors: Hitoshi Habuka, Satoko Oda, Yasushi Fukai, Katsuya Fukae, Takashi Takeuchi, Masahiko AiharaAbstract:Abstract Etch Rates of polycrystalline β-silicon carbide (SiC) substRate in a wide range from less than one to more than 10 μm/min are obtained using chlorine trifluoride gas in ambient nitrogen at 673–973 K and atmospheric pressure in a horizontal reactor. Over the chlorine trifluoride gas concentrations of 10–100% used in this study, the Etch Rate increases at the substRate temperatures between 673 and 773 K. Additionally, the Etch Rate at temperatures higher than 773 K is independent of the substRate temperature, similar to the one obtained using chlorine trifluoride gas concentration of 100%. The root means square roughness of Etched surface tends to be small at high temperatures and high chlorine trifluoride gas concentrations. The polycrystalline β-SiC Etch Rate can be adjusted using a combination of gas flow Rate, chlorine trifluoride gas concentration, and substRate temperature in order to obtain surfaces suitable for various purposes.
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silicon carbide Etching using chlorine trifluoride gas
Japanese Journal of Applied Physics, 2005Co-Authors: Hitoshi Habuka, Satoko Oda, Yasushi Fukai, Katsuya Fukae, Takashi Takeuchi, Masahiko AiharaAbstract:The Etch Rate, chemical reactions and Etched surface of β-silicon carbide are studied in detail using chlorine trifluoride gas. The Etch Rate is greater than 10 µm min-1 at 723 K with a flow Rate of 0.1 l min-1 at atmospheric pressure in a horizontal reactor. The maximum Etch Rate at a substRate temperature of 773 K is 40 µm min-1 with a flow Rate of 0.25 l min-1. The step-like pattern that initially exists on the β-silicon carbide surface tends to be smoothed; the root-mean-square surface roughness decreases from its initial value of 5 µm to 1 µm within 15 min; this minimum value is maintained for more than 15 min. Therefore, chlorine trifluoride gas is considered to have a large Etch Rate for β-silicon carbide associated with making a rough surface smooth.
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silicon Etch Rate using chlorine trifluoride
Journal of The Electrochemical Society, 2004Co-Authors: Hitoshi Habuka, Takahiro Sukenobu, Hideyuki Koda, Takashi Takeuchi, Masahiko AiharaAbstract:The mechanism causing the behavior of the silicon Etch Rate using chlorine trifluoride gas, which appears to be independent of the substRate temperature in a horizontal cold-wall reactor, is clarified by means of numerical calculations taking into account the surface chemical reaction Rate on the silicon substRate surface and the transport phenomena in the entire reactor. The activation energy of the overall Rate constant of its surface chemical reaction is evaluated, for the first time, to be 6000 J mol -1 , which can reproduce the Etch Rate and its behavior obtained by the measurement. With increasing substRate temperature in the reactor, the effect of a modeRate increase in both the diffusivity of chlorine trifluoride gas and the overall Rate constant is considered to be compensated by the decrease in the chlorine trifluoride gas concentration due to the gas volume expansion in the gas phase above the substRate. Therefore, the Etch Rate can be independent of the substRate temperature.
G S Sahoo - One of the best experts on this subject based on the ideXlab platform.
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study of variations in structural optical parameters and bulk Etch Rate of cr 39 polymer due to electron irradiation
Journal of Applied Physics, 2016Co-Authors: G S Sahoo, S P Tripathy, D S Joshi, T BandyopadhyayAbstract:In this work, electron induced modifications on the bulk Etch Rate, structural and optical parameters of CR-39 polymer were studied using gravimetric, FTIR (Fourier Transform Infrared) and UV–vis (Ultraviolet–Visible) techniques, respectively. CR-39 samples were irradiated with 10 MeV electron beam for different durations to have the absorbed doses of 1, 10, 550, 5500, 16 500, and 55 000 kGy. From the FTIR analysis, the peak intensities at different bands were found to be changing with electron dose. A few peaks were observed to shift at high electron doses. From the UV-vis analysis, the optical band gaps for both direct and indirect transitions were found to be decreasing with the increase in electron dose whereas the opacity, number of carbon atoms in conjugation length, and the number of carbon atoms per cluster were found to be increasing. The bulk Etch Rate was observed to be increasing with the electron dose. The primary objective of this investigation was to study the response of CR-39 to high elec...
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study of variations in structural optical parameters and bulk Etch Rate of cr 39 polymer due to electron irradiation
Journal of Applied Physics, 2016Co-Authors: G S Sahoo, S P Tripathy, D S Joshi, T BandyopadhyayAbstract:In this work, electron induced modifications on the bulk Etch Rate, structural and optical parameters of CR-39 polymer were studied using gravimetric, FTIR (Fourier Transform Infrared) and UV–vis (Ultraviolet–Visible) techniques, respectively. CR-39 samples were irradiated with 10 MeV electron beam for different durations to have the absorbed doses of 1, 10, 550, 5500, 16 500, and 55 000 kGy. From the FTIR analysis, the peak intensities at different bands were found to be changing with electron dose. A few peaks were observed to shift at high electron doses. From the UV-vis analysis, the optical band gaps for both direct and indirect transitions were found to be decreasing with the increase in electron dose whereas the opacity, number of carbon atoms in conjugation length, and the number of carbon atoms per cluster were found to be increasing. The bulk Etch Rate was observed to be increasing with the electron dose. The primary objective of this investigation was to study the response of CR-39 to high electron doses and to determine a suitable pre-irradiation condition. The results indicated that, the CR-39 pre-irradiated with electrons can have better sensitivity and thus can be potentially applied for neutron dosimetry.