Specific Process Knowledge/Wafer cleaning

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Cleaning of wafers

During processing it is sometimes mandatory, necessary or just recommended to clean the wafers. This can be done by different cleaning procedures depending on what the wafers have been exposed to where they are going to be further processed. Please consult the cross contamination scheme for to see whether your wafers need a cleaning before the next processing sequence.

Comparison of Wafer Cleaning Methods

	RCA	7-up & Piranha	5% HF	IMEC	Soap Sonic
Generel description	Two step process to remove organics and metals	Removes organics and alkali ions	Removing native oxide	Cleaning before wafer bonding	Removing dust and particles
Purpose	Mandatory prior furnace processes	When needed and always after KOH etch and Nitride etch in Phosphoric acid. Sometimes mandatory before next processing step.	Optional during RCA cleaning	Recommended cleaning and treatment before wafer bonding	Mandatory cleaning of very dirty items that enters the cleanroom. Should always be followed by a piranha clean.
Substrate size	#1-25 2", 4" and 6" wafers	#1-25 2", 4" and 6" wafers	#1-25 2", 4" and 6" wafers	#1-25 2" and 4" wafers	All sizes that can go into the bath
Allowed materials	Silicon Poly Silicon Silicon Oxide Silicon Nitride Silicon Oxynitride Quartz/fused silica	Silicon Poly Silicon Silicon Oxide Silicon Nitride Silicon Oxynitride Quartz/fused silica Pyrex and wafers with Cr ONLY in Mask cleaning bath or beaker	Silicon Poly Silicon Silicon Oxide Silicon Nitride Silicon Oxy-nitride Quartz/fused silica Resists (depending on bath) Pyrex (depending on bath)	Silicon Poly Silicon Silicon Oxide Silicon Nitride Silicon Oxynitride Quartz/fused silica Pyrex	All materials