Improvement in smoothness of anisotropically etched silicon surfaces: Effects of surfactant and TMAH concentrations

Cheng, Di; Gosálvez, Miguel A.; Hori, Tatsuya; Sato, Kazuo; Shikida, Mitsuhiro

doi:10.1016/j.sna.2005.08.022

Cited by 76 publications

(82 citation statements)

References 6 publications

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“…Many studies have been done on surface morphologies and etch rates of (100) and (110) Si planes so far (Bressers et al 1996;Sato et al 1999;van Veenendaal et al 2001;Gosalvez and Nieminen 2003;Cho Wen-June et al 2004;Cheng et al 2006). The etching processes were usually carried out in TMAH or KOH aqueous solutions, optionally with addition of surfactants or alcohols.…”

Section: Introductionmentioning

confidence: 99%

Impact of alcohol additives concentration on etch rate and surface morphology of (100) and (110) Si substrates etched in KOH solutions

Rola

Zubel

2012

Microsyst Technol

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The influence of alcohol concentration on etch rate and surface morphology of (100) and (110) Si planes was investigated in this paper. The etching processes were carried out in KOH solutions with different concentrations of isopropanol and butanols. The etch rate minima versus alcohol concentration were observed for all the alcohols used in the experiments. Furthermore, close to the concentrations of etch rate minima, the smooth (110) planes were obtained. However, the (100) surfaces were covered with hillocks at these concentrations. Based on the surface tension measurements and literature reports, the explanation of appearance of the etch rate minimum was suggested. In the proposed model, the adsorption maximum corresponds to the complete formation of an alcohol monolayer on Si surface and, consequently, to the etch rate minimum. At higher concentrations of alcohol, the monolayer disappears and the etch rate increases.

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Section: Introductionmentioning

confidence: 99%

Impact of alcohol additives concentration on etch rate and surface morphology of (100) and (110) Si substrates etched in KOH solutions

Rola

Zubel

2012

Microsyst Technol

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“…It means that the etched surface of Si{110} is not affected significantly when NH 2 OH is added into KOH solution. Main cause of surface roughness in the wet etching process is micromasking by the hydrogen bubbles and/or impurities on the surface during the etching process [24,[44][45][46].…”

Section: Etched Surface Morphologymentioning

confidence: 99%

“…Different kinds of additives (e.g. redoxsystem or complexants, oxidizing agent, surfactants, and metal impurities) [13][14][15][16][17] are Open Access *Correspondence: prem@iith.ac.in MEMS and Micro/Nano Systems Laboratory, Department of Physics, Indian Institute of Technology Hyderabad, Kandi, Sangareddy, India added into KOH to get high speed etching and the alcohols/surfactants are incorporated to improve the surface morphology [18][19][20][21][22][23][24]. Moreover, etching at the boiling point of the etchant [11,25], microwave irradiation of the etchant [26], ultrasonic agitation of the etchant [27] have been employed to increase the etch rate.…”

Section: Introductionmentioning

confidence: 99%

Etching characteristics of Si{110} in 20 wt% KOH with addition of hydroxylamine for the fabrication of bulk micromachined MEMS

Rao

Swarnalatha

Pal

2017

Micro and Nano Syst Lett

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Anisotropic wet etching is a most widely employed for the fabrication of MEMS/NEMS structures using silicon bulk micromachining. The use of Si{110} in MEMS is inevitable when a microstructure with vertical sidewall is to be fabricated using wet anisotropic etching. In most commonly employed etchants (i.e. TMAH and KOH), potassium hydroxide (KOH) exhibits higher etch rate and provides improved anisotropy between Si{111} and Si{110} planes. In the manufacturing company, high etch rate is demanded to increase the productivity that eventually reduces the cost of end product. In order to modify the etching characteristics of KOH for the micromachining of Si{110}, we have investigated the effect of hydroxylamine (NH 2 OH) in 20 wt% KOH solution. The concentration of NH 2 OH is varied from 0 to 20% and the etching is carried out at 75 °C. The etching characteristics which are studied in this work includes the etch rates of Si{110} and silicon dioxide, etched surface morphology, and undercutting at convex corners. The etch rate of Si{110} in 20 wt% KOH + 15% NH 2 OH solution is measured to be four times more than that of pure 20 wt% KOH. Moreover, the addition of NH 2 OH increases the undercutting at convex corners and enhances the etch selectivity between Si and SiO 2 .

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“…{100}, {110} and {111}) can easily be determined using {100}, {110} and {111} silicon wafers which are commonly available in the market. In order to obtain the detailed data on the crystal orientation dependence of the etch rate, either a wagon wheel structure (a series of narrow and long mask opening rotated by a small angle to each other about a center) as shown in Figure 4 [25, [150][151][152][153][154] or a silicon hemisphere as shown in Figure 5 [29, 34,37,38] is employed. Wagon wheel structure gives the etch rates of limited number of crystallographic planes, while silicon hemisphere provides etch rate data of all possible crystallographic planes as presented in Figure 5.…”

Section: Difference Between Etch Rate Underetching and Undercuttingmentioning

confidence: 99%

A comprehensive review on convex and concave corners in silicon bulk micromachining based on anisotropic wet chemical etching

Pal¹,

Sato²

2016

Nano Online

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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.

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Improvement in smoothness of anisotropically etched silicon surfaces: Effects of surfactant and TMAH concentrations

Cited by 76 publications

References 6 publications

Impact of alcohol additives concentration on etch rate and surface morphology of (100) and (110) Si substrates etched in KOH solutions

Impact of alcohol additives concentration on etch rate and surface morphology of (100) and (110) Si substrates etched in KOH solutions

Etching characteristics of Si{110} in 20 wt% KOH with addition of hydroxylamine for the fabrication of bulk micromachined MEMS

A comprehensive review on convex and concave corners in silicon bulk micromachining based on anisotropic wet chemical etching

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