Specific Process Knowledge/Wafer cleaning/7-up & Piranha

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Cleaning of wafers or masks

Cleaning of wafers or masks with sulphuric acid can be done either in a dedicated tank "7-up" or in the fume hood in a beaker "Piranha". Both 7-up and Piranha removes heavy organics. Always use one of these after KOH etch or hot phosphoric acid etch to remove alkali ions before further processing. 7-up and Piranha are also used as cleaning solutions after stripping resist.

The user manual, user APV and contact information can be found in LabManager: 7-up 6" info page in LabManager,7-up Mask info page in LabManager

Comparing data for "7-up" and Piranha

	7-up wafers	7-up Masks	Piranha
General description	Cleaning of wafers using the dedicated tank in cleanroom D3.	Cleaning of masks using the dedicated tank in cleanroom D3.	Cleaning of wafers using a beaker in the fumehood in cleanroom B1. Used for glass wafers or wafers with metal or other materials that you are not allowed to put in the 7-up for wafers or masks.
Chemical solution	98% Sulfuric acid and Ammonium sulfate	98% Sulfuric acid and Ammonium sulfate	98% Sulfuric acid and Hydrogen peroxide 4:1 add H₂O₂ to H₂SO₄
Process temperature	80 ^oC	80 ^oC	~70 ^oC the chemicals will heat up to working temperature during mixing, therefore be careful!First ad H2SO4 then H2O2
Process time	10 min.	10 min.	10 min.
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 Soda lime glass Wafers with Cr	All materials (in beaker).
Batch size	1-25 4" or 6" wafers	1-25 4" or 6" wafers or 1-4 5" masks	1-5 4" wafer at a time
Size of substrate	4-6" wafers	4-6" wafers or 5" masks	All sizes that can fit into the beaker in a dedicated holder