View source for KOH Etch


Potassium Hydroxide, or KOH, etches silicon crystals anisotropically. In an anisotropic etch, the etch rate is different for all Si crystal planes. 
The etch rate for the Si(100) plane is about 1.4 um/min depending on the temperature and the KOH solution concentration, while on the Si(111) the etch rate is about 0.25 - 0.5 um/min.  The etch rate with various temperatures can be found in the standard operating procedure found below. It is important to notice that, by taking advantage of the difference in etch rate among the Si faces (i.e. selectivity), KOH etching offers unique etch profiles. 


Very good reference [https://repository.upenn.edu/cgi/viewcontent.cgi?article=1029&context=scn_protocols KOH Etch]

[[File:KOH etching.png|thumb]]

==Standard Operating Procedure==
{{#widget:GoogleDoc|key=171b2ZoVGWiBQY0UaNaANtHSF3SqnhobcHywbYqKA0eI}}

==Returning to the Cleanroom==
Wafers which have been polished using CMP, developed in metal-ion bearing developer (e.g. AZ 400K) or etched in KOH '''NEED''' to be thoroughly cleaned before being processed in the cleanroom. Such samples must undergo:


1) The etch mask (typically SiO<sub>2</sub> or Si<sub>3</sub>N<sub>4</sub>) will need to be removed prior to further cleaning. Submersion in [https://lnf-wiki.eecs.umich.edu/wiki/Hydrofluoric_acid Hydrofluoric Acid] is typically the best method of doing so; this should be performed in the HF tank at [https://lnf-wiki.eecs.umich.edu/wiki/Base_Bench_91 Base Bench 91].

2) [https://lnf-wiki.eecs.umich.edu/wiki/Piranha_Etch Piranha Cleaning]

3) SC2 cleaning in [https://lnf-wiki.eecs.umich.edu/wiki/Acid_Bench_92 Acid Bench 92]

4) RCA cleaning in [https://lnf-wiki.eecs.umich.edu/wiki/RCA_Bench_81 RCA Bench 81]

*Inquire via the [https://lnf-wiki.eecs.umich.edu/wiki/LNF_Helpdesk Helpdesk] if you have questions regarding any of these cleaning steps.

==Safety Data Sheet==
https://drive.google.com/file/d/0B8WeTTMTotIfMkxIQ0w4cFBUdVdPNUNHaE1BTnpGdw/view?usp=sharing

==Equipment==
[[Base_Bench_91|Base Bench 91]]