Specific Process Knowledge/Wafer cleaning/7-up & Piranha
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 fumehood in a beaker "Piranha" Both 7-up and Piranha removes heavy organics. Always use one of these after KOH to remove alkali ions before further processing. 7-up and Piranha are also used as cleaning solutions after stripping resist.
| 7-up | Piranha | |
|---|---|---|
| General description |
Cleaning of wafers or masks using the dedicated tanks. There are one tank for masks and glasswafers and one for 4-6" Si wafers in cleanroom 4 and one tank in cleanroom 3 for 4" Si wafers only. |
Cleaning of wafers using a beaker in the fumehood in cleanroom 2.Used for glass wafers or wafers with metal or other materials that you are not allowed to put in the 7-up for wafers. |
| Chemical solution | 98% Sulfuricacid and Ammoniumsulfat | 98% Sulfuricacid and Hydrogenperoxide 4:1 add HFailed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle _2} OFailed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle _2} to HFailed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle _2} SOFailed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle _4} |
| Process temperature | 80 oC | ~70 oC the chemicals will heat up to working temperature during mixing, therefore be carefull! |
| Process time |
10 min. |
10 min. |
| Allowed materials |
Dependent on which bath is used, look at the text in the pictures. |
All materials (in beaker). |
| Batch size |
1-19/25 4" wafers or 5 masks at a time |
1-5 4" wafer at a time |
| Size of substrate |
4-6" wafers |
2-4" wafers |