Silicon anisotropic

Aluminum, copper, diamond, gold, silicon Anisotropic etching, isotropic etching... 

FEATURES OF SILICON ANISOTROPIC ETCHING IN AQUEOUS KOH SOLUTIONS... 

Barycka and 1. Zubel, Silicon anisotropic etching in KOH-isopropanol etchant, Sensors Actuators A 48, 229, 1995. 

Z. Irena and B. Irena, Silicon anisotropic etching in alkaline solutions. I. The geometric description of figures developed under etching Si(lOO) in various solutions. Sensors Actuators A70, 250, 1998. 

J. Kasparian, M. Elwenspoek, and P. Allongue, Digital computation and in situ STM approach of silicon anisotropic etching. Surf. Sci. 388 50, 1997. 

Many models have been proposed for the mechanism of silicon anisotropic etching in alkaline solutions. They can be grouped into two categories those that attribute the relative slower etch rate of (111) planes to the presence of a passive oxide film on the surface, and those that consider the etch rate difference among different orientations to be governed by reaction kinetics. 

Aqueous alkaline etchants, such as TMAH [10], KOH [7], NaOH [11], and CsOH [12], all etch silicon anisotropically with good selectivity to silicon nitride or oxide. They are all dopant dependent, etching silicon layers highly doped with boron slowly or not at all. 

The reaction mechanism of the etch process is not fully clear. Several researchers proposed physical models for silicon anisotropic etching from the viewpoints of energy band gap [4, 5] and Gibbs free energy [6]. Over these models, one equation describing the simplified reaction mechanism is addressed as follow ... 

Bulk micromachining of silicon Anisotropic silicon micromachining... 

The most often used etchant for silicon anisotropic etching is KOH. The recipe is often mixed with isopropyl alcohol (IPA) to saturate the solution to increase the etch selectivity for (111) versus (100) planes. Generally, the etch selectivity on the (111) plane can be up to 400 times slower than on the (100) plane while using alkali hydroxide solutions as etchants for silicon anisotropic etching. In addition, the etch rate for KOH anisotropic etching... 

In5)urity doping can also be applied for slowing down the etch rate for silicon anisotropic etching in alkali... 

Table 10.7 shows that the KOH etch rate is strongly affected by the crystallography orientation of the silicon (anisotropic). 

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