Solar Alkaline Etching of Single Crystal

What is alkaline etching?

Alkaline etching is an anisotropic process. It is used to smooth the surface, reveal defects, and make wafers thinner. Alkaline etchants are notable for different etching rates in various crystallographic directions. The etching rate of crystal planes varies in the order (100) > (110) > (111).

Why does alkaline etchant etch faster?

Thus, in alkaline etchant, the etching rate is faster along the directions of than that along other directions due to the lower activation energy of the atoms on {100} surface 8. Thereby, the etching mainly occurs along the directions and stops at the {111} planes, leading to the formation of upright pyramidal structures.

What is the etching rate of single crystal Si in an anisotropic etchant?

The etching rate of single crystal Si in an anisotropic etchant varies with the crystallographic orientation of the substrate, which generally decreases in the order of (100) ≈ (110) >  (111) 17, 18. The alkali etching process usually includes an oxidation step and a reduction step based on an electrochemical model.

Can anisotropic etching be used in industrial silicon solar cells?

Anisotropic etching of silicon has found broad acceptability in fabrication of industrial silicon solar cells also in order to reduce reflection losses from the front surface . Anisotropic etching of a (1 0 0) silicon wafer leads to formation of micro-pyramid structure on the surface of the wafer.

Is anisotropic etching of silicon in inorganic alkaline solution useful?

Conclusions Anisotropic etching of silicon in inorganic alkaline solution has been studied from the view point of its application in commercial silicon solar cell. Etch rate of boron doped (1 0 0) Cz silicon wafers of 1–2 Ω cm resistivity has been determined for alkaline solution used for removal of the surface damages.

What is the anisotropic factor for alkaline etchants?

While, for certain alkaline etchants, the etch rate of the direction is effectively zero. Thus, the anisotropic factor is usually over 100 for alkaline etchants. The etching rate of (111) substrate by Cu assisted anisotropic etching is much faster than alkali etching, which may have many potential applications.