Aging Effects of KOH+NH₂OH Solution on the Etching Characteristics of Silicon

Abstract

Recently the effect of hydroxylamine (NH2OH) on the etching characteristics of alkaline solution (e.g. potassium hydroxide (KOH) and tetramethylammonium hydroxide (TMAH)) is studied to obtain improved etching characteristics, especially high etch rate and enhanced undercutting at convex corners. Alkaline solution modified with NH2OH provides improved etch rate of silicon (Si), high etch selectivity between silicon and silicon dioxide (SiO2), considerably high undercutting at convex corner. As the addition of NH2OH alters the etching properties of alkaline solution dramatically, it is indispensable to investigate the effect of aging of NH2OH-added alkaline solution on its etching characteristics. In this work, the influence of aging of 15% NH2OH-added 20 wt% KOH, which is referred to as an etchant, on the etching characteristics of Si{100} and Si{110} is studied in detail. The results are systematically presented. The etch rate of silicon and the undercutting at convex corners decrease significantly with etchant aging at etching temperature, while the etch rate of silicon dioxide and etched surface morphology are not considerably affected with the age of the etchant. This study is significantly important for the researchers and industries where silicon wet anisotropic etching is used for silicon micromachining.

Enhanced etching characteristics of Si{100} in NaOH-based two-component solution

“…Though a smooth surface can be obtained by the addition of surfactant, it impedes the etch rate, consequently inhibiting the commercial scale fabrication. Different methods such as ultrasonic agitations, microwave irradiation, and by adding additives in wet anisotropic etching have been employed to increase the etch rate [41][42][43][44][45][46][47][48][49][50][51][52][53][54][55]. However, each method has its pros and cons.…”

“…Other way of increasing the etch rate is etching at (or near) the boiling point of the etchant [11,56]. Recently, NH 2 OH-added TMAH and KOH solutions, which provide very high etch rate in comparison to pure KOH and TMAH, are explored for applications in wet bulk micromachining for the formation of MEMS structures [49][50][51][52][53][54]. Although NH 2 OH-added KOH/TMAH provides very high etch rate, the etch rate is reduced with the age of etchant [54,55].…”

“…Recently, NH 2 OH-added TMAH and KOH solutions, which provide very high etch rate in comparison to pure KOH and TMAH, are explored for applications in wet bulk micromachining for the formation of MEMS structures [49][50][51][52][53][54]. Although NH 2 OH-added KOH/TMAH provides very high etch rate, the etch rate is reduced with the age of etchant [54,55]. NaOH, a low-cost etchant, has been explored for the fabrication of microstructures with vertical walls, removal of the saw-damaged layer from the multi-crystalline as-cut silicon wafer and surface texturing for silicon solar cell [57][58][59].…”

Wet anisotropic etching characteristics of Si{111} in NaOH-based solution for silicon bulk micromachining

“…The salient factors that control the etching characteristics are etching time, etching temperature, agitation during etching, and the presence of an additive in the etchant. Lately, the influence of hydroxylamine (NH 2 OH) on the etching properties of KOH and TMAH is reported [37][38][39][40][41][42][43].…”

Electrochemically Oxidized Porous Silicon Uses as an Electrochemical Sensor for Ethanol Detection

“…The obtained results are in good agreement with those of other investigations. 23,24 It is important to note that the lower current density (<30 mA cm −2 ) favors for the formation of well defined diameter, orientation and highly separated ordered of nanopores; hence, it may lead to mass transportation within nano pores. As the current density reaches a certain value, a part of nanopores coagulate to larger structures.…”