Alkaline Etching of Silicon

Alkaline etching of crystalline using KOH (potassium hydroxide), TMAH (tetramethyl ammonium hydroxide), or EDP (ethylenediamene pyrocatecol) is performed for creating various feature definition in MEMS (micro electrical mechanical structures, solar cells, and integrated circuit manufacturing. KOH will be discussed in this section. The alkaline chemistries have the ability to preferentially etch silicon along the crystal orientation. This makes it possible to create geometries difficult to produce with other micromachining techniques (for example V-grooves). The etching rate is dependent on the orientation of the silicon's crystal planes, orientations of <100> and <110> etch differently than <111> due to the arrangement of atoms at these orientations. Silicon <100> etches anisotropically along the <111> crystal plane, with a 54.74° angle from the <100> plane. Silicon <100> that is masked etches as shown in Figure 1.