It is useful to have an idea about the etch rate of (100) silicon in KOH for different concentrations and temperatures whenever you need to do some etching in KOH.

There is a very good book entitled: "Handbook of Microlithography, Micromachining, and Microfabrication, Volume 2: Micromachining and Microfabrication" edited by P. Rai-Choudhury, in which in chapter 2 D.L. Kendall and R.A. Shoultz give an empirical formula for the etch rate of silicon in KOH solutions:

R

_{100}=2.6*10

^{6}*W

^{2.5}*exp-(W/300+0.48)/k*(T+273) [μm/hr],

where W is the actual wt% of KOH in water, k is Boltzmann's constant 8.617*10

^{-5} eV/K and T is the temperature in degrees Celcius.

Using this formula one can calculate approximately what will be the etching rate of (100) silicon in KOH. However, the real etch rate may deviate significantly due to many factors.

Below, you will find a graph for the etching rate of silicon (in μm/hr) in KOH for different KOH concentrations and temperatures:

If you want to find out more about KOH etching then you can read the following article:

"

Overview of KOH etching in microfabrication of MEMS structures".