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.

scholarly journals Etching of Crystalline Silicon in Thermal Environment

2011 ◽  
Vol 2 ◽  
pp. 38-42
Author(s):  
Shobha Kanta Lamichhane ◽  
Min Raj Lamsal
Keyword(s):  
Process Control ◽  
Etch Rate ◽  
Crystalline Silicon ◽  
Thermal Environment ◽  
Anisotropic Etching ◽  
Wet Etching ◽  
Control Technique ◽  
Etching Solution ◽  
Wet Etch ◽  
Process Control Technique

Thin wafer have become a basic need for a wide variety of new microelectronic products. Wafers that have been thinned using wet etch process on the backside have less stress compared with standard mechanical back grinding. Isotropic wet etching of silicon is typically done with a mixture of nitric and hydrofluoric acids. As the silicon is etched and incorporated in the etching solution the etch rate will decrease with time. This variation has been modeled. The focus of this paper is to compare the process control technique for maintaining a consistent etch rate as a function of time and wafer processed.Keywords: Isotropic and anisotropic etching; MEMS; SOI; LPCVDThe Himalayan Physics Vol.2, No.2, May, 2011Page: 38-42Uploaded Date: 1 August, 2011

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.

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.

FABRICATION OF PYRAMIDAL CAVITY STRUCTURE WITH MICRON-SIZED TIP USING ANISOTROPIC KOH ETCHING OF SILICON (100)

2015 ◽  
Vol 74 (10) ◽  
Author(s):  
Ummikalsom Abidin ◽  
Burhanuddin Yeop Majlis ◽  
Jumril Yunas
Keyword(s):  
Model Comparison ◽  
3D Structure ◽  
Three Dimensional ◽  
Size Variation ◽  
Anisotropic Etching ◽  
Etching Solution ◽  
Cavity Structure ◽  
Wet Anisotropic Etching ◽  
Etching Selectivity ◽  
Koh Etching

Microelectromechanical System (MEMS) are systems of micron-sized structures and typically integrated with microelectronic components. Bulk micromachining using wet anisotropic etching is able to etch silicon substrates to a desired three-dimensional (3D) structure, depending on the silicon crystallographic orientation. To date, MEMS components i.e. thermal, pressure, mechanical, bio/chemical sensors have been fabricated with wet anisotropic etching of silicon. This paper presents the fabrication of a 3D pyramidal cavity structure with micron-sized tip of silicon (100) using anisotropic KOH etching of w/w 45 % at 80 oC temperature. Volume percent of 10 % IPA as a less polar diluent is added to the KOH etching solution in saturating the solution and controlling the etching selectivity and rate. Smooth etched silicon surface of hillock free is able to be achieved with IPA addition to the KOH etching solution. A characteristic V-shaped cavity with side angle of 54.8 degrees has successfully been formed and is almost identical to the theoretical structure model. Comparison of two different silicon nitride window masks on the micron-size tip formation is also investigated. Under etch, over etch and etching selectivity, as common problems effecting the micron-tip size variation, are also addressed in this work. In conclusion, anisotropic KOH etching as a simple, fast and inexpensive bulk micromachining technique, in fabricating 3D MEMS structure using silicon (100), is validated in this work.

The Improvement of Wet Anisotropic Etching with Megasonic Wave

2005 ◽  
pp. 557-561
Author(s):  
Woo Seong Che ◽  
Chang Gil Suk ◽  
Tae Gyu Park ◽  
Jun Tae Kim ◽  
Jun Hyub Park
Keyword(s):  
Anisotropic Etching ◽  
Wet Anisotropic Etching

Thermally Induced Activation Energy of Crystalline Silicon in Alkaline Solution

1970 ◽  
Vol 11 ◽  
pp. 215-222
Author(s):  
SK Lamichhane
Keyword(s):  
Activation Energy ◽  
Potassium Hydroxide ◽  
Etch Rate ◽  
Crystalline Silicon ◽  
Lattice Parameter ◽  
Device Fabrication ◽  
Strong Anisotropy ◽  
Temperature Dependent ◽  
Thermal Agitation ◽  
Thermally Induced

Etching of crystalline silicon by potassium hydroxide (KOH) etchant with temperature variation has been studied. Results presented here are temperature dependent ER (etch rate) along the crystallographic orientations. Etching and activation energy are found to be consistently favorable with the thermal agitation for a given crystal plane. Study demonstrates that the contribution of microscopic activation energy effectively controls the etching process. Such a strong anisotropy in ER on KOH allows us a precious control of lateral dimensions of the silicon microstructure as well as surface growth of the crystal during micro device fabrication. Key words: anisotropy; activation energy; etch rate; lattice parameter; micromachining DOI: 10.3126/njst.v11i0.4148Nepal Journal of Science and Technology 11 (2010) 215-222

THIN SILICON STRUCTURES FABRICATION BY WET ANISOTROPIC ETCHING

2003 ◽  
Vol 04 (02) ◽  
pp. 311-314
Author(s):  
AJAY AGARWAL ◽  
X. L. ZHANG ◽  
T. GAN ◽  
J. SINGH
Keyword(s):  
Anisotropic Etching ◽  
Silicon Structures ◽  
Wet Anisotropic Etching ◽  
Thin Silicon
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