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 (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.

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高速硅湿各向异性刻蚀技术在块体微加工中的应用

湿各向异性刻蚀广泛用于硅体微加工中，以制造微结构，以用于微机电系统（MEMS）领域的各种应用。另外，它最广泛地用于表面纹理化以最小化光的反射率以提高晶体硅太阳能电池的效率。在湿法批量微加工中，蚀刻速率是影响产量的主要因素。较慢的蚀刻速率会增加制造时间，因此在MEMS工业中备受关注，在MEMS工业中，采用湿法各向异性蚀刻进行硅块微加工，尤其是通过底切工艺去除下方材料来制造深腔和独立的微结构。已经提出了几种通过物理手段（例如，搅拌，微波辐射）或通过掺入化学添加剂来增加湿各向异性蚀刻剂中硅的蚀刻速率的方法。在蚀刻过程中的超声搅拌和对蚀刻剂的微波照射增加了蚀刻速率。然而，超声方法可能使易碎的结构破裂，并且微波辐射导致辐射损伤结构。另一种方法是将蚀刻温度提高至蚀刻剂的沸点。在KOH的沸点附近研究了纯氢氧化钾溶液（KOH）的蚀刻特性，而在更高的温度下研究了添加了四甲基氢氧化铵（TMAH）的表面活性剂以提高蚀刻速率。这两项研究都表明了一种通过将蚀刻剂的温度升高到其沸点来提高蚀刻速率的潜在方法，而沸点是蚀刻溶液浓度的函数。在TMAH和KOH中研究了各种添加剂对硅蚀刻速率的影响。在本文中，已经讨论了改善蚀刻速率的添加剂。最近，详细研究了羟胺（NH2OH）对TMAH和KOH蚀刻特性的影响。改变TMAH / KOH中NH 2 OH的浓度以优化蚀刻剂组成以获得改善的蚀刻特性，特别是蚀刻速率和底切，这是增加产量的重要参数。在本文中，