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 KOH Etch

Standard Operating Procedure

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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 SiO₂ or Si₃N₄) will need to be removed prior to further cleaning. Submersion in Hydrofluoric Acid is typically the best method of doing so; this should be performed in the HF tank at Base Bench 91.

2) Piranha Cleaning

3) SC2 cleaning in Acid Bench 92

4) RCA cleaning in RCA Bench 81

• Inquire via the 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