Wet Anisotropic Etching Characteristics of Si{100} in TMAH+Triton at near the Boiling Point

2015 ◽  
Vol 645-646 ◽  
pp. 58-63 ◽  
Author(s):  
Ming Qiu Yao ◽  
Bin Tang ◽  
Wei Su ◽  
Gang Tan
Keyword(s):  
Boiling Point ◽  
Etch Rate ◽  
Etching Rate ◽  
Ammonium Hydroxide ◽  
Optical Microscope ◽  
Atomic Force ◽  
Tetramethyl Ammonium Hydroxide ◽  
Wet Anisotropic Etching ◽  
Etched Surface ◽  
Anisotropic Silicon Etching

The anisotropic silicon etching characteristics of TMAH(tetramethyl ammonium hydroxide)+Triton at near the boiling point were investigated. The etch rate of Si {100}, the convex corners, and the roughness of the etched surface contact with the fabrication of bulk microstructures and thus micromechanical devices in silicon. This study presents that the etch rate of Si {100} in 25 wt.% TMAH with 0.1% Triton at near boiling point (112°C) is 1.37μm/min, it is three times higher than it at 80°C. The surface roughness and convex corners of Si {100} after etching at different temperature were investigated by optical microscope, scanning electron microscope (SEM) and atomic force microscope (AFM). The etching rate and smoothness of an etched surface can be improved simultaneously at near boiling point, meanwhile, the undercutting on convex corner should be accepted.

Removal of Mechanical-Polishing-Induced Surface Damages on 4H-SiC Wafers by Using Chemical Etching with Molten KCl+KOH

2014 ◽  
Vol 778-780 ◽  
pp. 746-749 ◽  
Author(s):  
Yong Zhao Yao ◽  
Yukari Ishikawa ◽  
Yoshihiro Sugawara ◽  
Koji Sato
Keyword(s):  
Chemical Etching ◽  
Etch Rate ◽  
Mechanical Polishing ◽  
Nanometer Scale ◽  
Force Microscopy ◽  
Damage Layer ◽  
Atomic Force ◽  
Surface Damages ◽  
Etched Surface ◽  
Koh Etching

High temperature (>1000 °C) chemical etching using molten KCl or molten KCl+KOH as the etchant has been carried out to remove the mechanical-polishing (MP) induced damage layer from 4H-SiC surface. Atomic force microscopy observations have shown that line-shaped surface scratches that have appeared on the as-MPed surface could be completely removed by KCl-only etching or by KCl+KOH etching (KCl:KOH=99:1 in weight) at ~1100 °C. Between the two recipes, KCl+KOH etching has shown a higher etch rate (6~7 times) and is able to remove ~9 μm and ~36 μm-thick damage layer from the Si (0001) and the C(000-1) surface, respectively. Besides, KCl+KOH etching seems to have formed a Si (0001) surface covered with atomic steps while KCl-only etched surface is featured with nanometer-scale pores.

Study of Under Etching Characters of Si (100) in Surfactant Added TMAH

2011 ◽  
Vol 483 ◽  
pp. 34-37
Author(s):  
Qi Fang Hu ◽  
Cheng Chen Gao ◽  
Yi Long Hao ◽  
Yang Xi Zhang
Keyword(s):  
Ethylene Oxide ◽  
Silicon Wafer ◽  
Fatty Alcohol ◽  
Etching Rate ◽  
Ammonium Hydroxide ◽  
Experimental Result ◽  
Alcohol Ethoxylate ◽  
Deep Etching ◽  
Tetramethyl Ammonium Hydroxide ◽  
Etching Effect

This work focuses on the etching characteristic of (100) silicon wafer in surfactant added tetramethyl-ammonium-hydroxide (TMAH:( CH3)4NOH) solution. The experimental result shows that under etching effect in TMAH achieves a significant reduction by adding fatty alcohol ethoxylate (R-O (CH2-CH2)n-OH) in the solution. Synperonic-A series fatty-alcohol-ethoxylate with increasing length of ethylene oxide segments are used to carry out the experiment. Comparing with the pure TMAH, the maximum under etching rate in the surfactant added TMAH is reduced to three quarters. The etching loss of convex corners is negligible for shallow to medium-deep etching (<30μm).

Smoothness Control of Wet Etched Si{100} Surfaces in TMAH+Triton

2014 ◽  
Vol 609-610 ◽  
pp. 536-541 ◽  
Author(s):  
Bin Tang ◽  
Ming Qiu Yao ◽  
Gang Tan ◽  
Prem Pal ◽  
Kazuo Sato ◽  
...  
Keyword(s):  
Chemical Etching ◽  
Electrochemical Etching ◽  
Optical Microscope ◽  
Smooth Surfaces ◽  
High Quality ◽  
Atomic Force ◽  
Wet Anisotropic Etching ◽  
Triton X ◽  
Galvanic Interaction ◽  
Micro Accelerometer

The effect of galvanic interaction between the evolving facets of the etch front on the Si {100} surface smoothness during wet anisotropic etching in surfactant-added tetramethylammonium hydroxide (TMAH) is studied by etching different mask patterns. Triton X-100, with formula C14H22O(C2H4O)n, where n=9-10, is used as the surfactant. The different smoothness of wet etched Si {100} surfaces, evaluated by atomic force microscope (AFM) and optical microscope, indicates that the wet etched Si {100} surfaces could become extremely smooth after the onset of the electrochemical etching contribution. A model to account for the galvanic interaction between the evolving facets is proposed, demonstrating that the chemical etching can be significantly surpassed by the electrochemical etching when the relative area of the exposed {100} surfaces are relatively small in comparison to that of the developed {111} sidewalls. Additionally, silicon beams with smooth surfaces are presented in the fabrication of a sandwich micro accelerometer to avoid the risk of device invalidation. This study is useful for engineering applications where the fabrication of microstructures for high quality devices should contain smooth surfaces.

scholarly journals High speed silicon wet anisotropic etching for applications in bulk micromachining: a review

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Prem Pal ◽  
Veerla Swarnalatha ◽  
Avvaru Venkata Narasimha Rao ◽  
Ashok Kumar Pandey ◽  
Hiroshi Tanaka ◽  
...  
Keyword(s):  
Microwave Irradiation ◽  
Boiling Point ◽  
Etch Rate ◽  
Microelectromechanical Systems ◽  
Crystalline Silicon ◽  
Potassium Hydroxide Solution ◽  
Anisotropic Etching ◽  
Irradiation Damage ◽  
Silicon Bulk ◽  
Wet Anisotropic Etching

AbstractWet 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 (NH2OH) on the etching characteristics of TMAH and KOH is investigated in detail. The concentration of NH2OH 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.

Wet Etching Technique to Reduce Pyramidal Hillocks for Anisotropic Silicon Etching in NaOH/IPA Solution

2015 ◽  
Vol 659 ◽  
pp. 681-685
Author(s):  
Chu Pong Pakpum
Keyword(s):  
Etch Rate ◽  
Wet Etching ◽  
High Yield ◽  
Solution Temperature ◽  
Silicon Etching ◽  
Etching Technique ◽  
Ultrasonic Agitation ◽  
The Difference ◽  
Etched Surface ◽  
Anisotropic Silicon Etching

The various methods of silicon wet etching techniques, which utilize ultrasonic agitation to reduce pyramidal hillocks in etched patterns, were evaluated in NaOH+IPA solution. The comparison of the etching methods composed of; 1.) no agitation + sample horizontally orientated, 2.) ultrasonic agitation + sample horizontally orientated, 3.) ultrasonic agitation + sample vertically orientated, and 4.) ultrasonic with rotation agitation + sample vertically orientated. It was found that the percentages of the etched patterns presenting hillocks after etching were 100%, 79.77%, 32.67% and 2.62%, respectively. Ultrasonic coupled with rotation agitation along with the sample vertically orientated is the most powerful etching technique, offering a high yield of smooth etched surface. The difference in etch rate between without agitation and applying ultrasonic agitation was not observed in this experiment, as it was operated in a solution temperature 60-65°C and a 275nm/min etch rate was achieved. The theories that relate to each evaluated method are also discussed.

Advanced Wet Etch Bulk Micromachining in {100} Silicon Wafers

2009 ◽  
Vol 1222 ◽  
Author(s):  
Prem Pal ◽  
Kazuo Sato
Keyword(s):  
Silicon Dioxide ◽  
Microelectromechanical Systems ◽  
Ammonium Hydroxide ◽  
Anisotropic Etching ◽  
Tetramethyl Ammonium Hydroxide ◽  
Local Oxidation ◽  
Wet Anisotropic Etching ◽  
Triton X ◽  
Wet Etch ◽  
Sharp Corners

AbstractIn this work we have developed novel microfabrication processes using wet anisotropic etchants to perform advanced bulk micromachining in {100}Si wafers for the realization of microelectromechanical systems (MEMS) structures with new shapes. The etching is performed in two steps in pure and Triton-X-100 [C14H22O(C2H4O)n, n = 9-10] added 25 wt% tetramethyl ammonium hydroxide (TMAH) solutions. The local oxidation of silicon (LOCOS) is attempted after the first anisotropic etching step in order to protect the exposed silicon. Two types of structures (fixed and freestanding) are fabricated. The fixed structures contain perfectly sharp corners and edges. Thermally grown silicon dioxide (SiO2) is used for the fabrication of freestanding structures. Present research is an approach to fabricate advanced MEMS structures, extending the range of 3D structures fabricated by silicon wet anisotropic etching.

Fine MCP Decapsulation Technology Development

2006 ◽  
Author(s):  
Jianwei Zhou ◽  
Wei Zheng ◽  
Taekoo Lee
Keyword(s):  
Chemical Etching ◽  
Etch Rate ◽  
Technology Development ◽  
New Technology ◽  
Ammonium Hydroxide ◽  
Mechanical Polishing ◽  
Technology Process ◽  
Tetra Methyl Ammonium Hydroxide ◽  
Die Surface

Abstract Multi-Chip Package (MCP) decapsulation is now becoming a rising problem. Because for traditional decapsulation method, acid can’t dissolve the top silicon die to expose the bottom die surface in MCP. It makes inspecting the bottom die in MCP is difficult. In this paper, a new MCP decapsulation technology combining mechanical polishing with chemical etching is introduced. This new technology can remove the top die quickly without damaging the bottom die using KOH and Tetra-Methyl Ammonium Hydroxide (TMAH). The technology process and relative application are presented. The factors that affect the KOH and TMAH etch rate are studied. The usage difference between the two etchant is discussed.

Sloped Sidewalls in 4H-SiC Mesa Structure Formed by a Cl2-O2 Thermal Etching

2007 ◽  
Vol 556-557 ◽  
pp. 733-736 ◽  
Author(s):  
S. Takenami ◽  
Tomoaki Hatayama ◽  
Hiroshi Yano ◽  
Yukiharu Uraoka ◽  
Takashi Fuyuki
Keyword(s):  
Electrical Properties ◽  
Etching Rate ◽  
Mesa Structure ◽  
Thermal Etching ◽  
Etching Method ◽  
Pn Junction ◽  
Etched Surface

Sloped sidewalls in 4H-SiC mesa structures on the (000-1) C face were formed by a Cl2-O2 thermal etching method. The etching rate of 4H-SiC (000-1) C face was 10 times faster than that of (0001) Si face, and the etching rate at 910oC was about 18μm/h. The etched surface was rather smooth, and the sidewall of the mesa was inclined to the off-axis substrate. Taking into account the off angle of about 8o toward [11-20] off direction, the angles of the sidewalls were 52-56o for the <1-100> and 55-57o for the <11-20> directions from the crystallographically accurate (000-1) C face. Epitaxial pn junction diodes with the sloped sidewalls structure were fabricated, which had good electrical properties.

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