Specific Process Knowledge/Wafer cleaning/7-up & Piranha: Difference between revisions

'''Feedback to this page''': '''[mailto:wetchemistry@danchip.dtu.dk?Subject=Feed%20back%20from%20page%20http://labadviser.danchip.dtu.dk/index.php/Specific_Process_Knowledge/Wafer_cleaning/7-up click here]'''

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.

[[Image:7-up_6inch.jpg|300x300px|right|thumb|7-up 6" in cleanroom D3. <br\> -Up to 25 wafers of 4" or 6" at a time.<br\> -Materials allowed: Silicon, Poly Silicon, Silicon Oxide, Silicon Nitride, Silicon Oxynitride,Quartz/fused silica]]

[[Image:7-up_Mask.jpg|300x300px|right|thumb|7-up for masks and glass wafers positioned in cleanroom D3:<br\> -Up to 25 glass wafers of 4" at a time or 4 masks.<br\> -Materials allowed: Silicon, Poly Silicon, Silicon Oxide, Silicon Nitride, Silicon Oxynitride, Quartz/fused silica, glass (Pyrex and Soda Lime), chromium]]

<!-- [[Image:7-up_RR3.jpg|300x300px|right|thumb|7-up 4": positioned in cleanroom C1<br\> -Up to 19 wafers of 4" at a time.<br\> -Materials allowed: Silicon, Silicon oxide, Silicon nitride, PolySi]]-->

'''The APV for working with piranha in fumehood can be found by clicking'' [http://labmanager.danchip.dtu.dk/d4Show.php?id=2479&mach=197 here]

===Comparing the 7-up cleans and Piranha clean===

! 7-up wafers

! 7-up Masks

! Piranha

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.

|98% Sulfuric acid and Ammonium sulfate

|98% Sulfuric acid and Ammonium sulfate

|98% Sulfuric acid and Hydrogen peroxide 4:1 add H₂O₂ to H₂SO₄

|80 ^oC

|80 ^oC

|~70 ^oC the chemicals will heat up to working temperature during mixing, '''therefore be careful!''' First ad H₂SO₄ then H₂O₂^{{fn|1}}.

All materials (in beaker).

{{fnb|1}} In preparing a solution involving an acid, always add the acid last. The exception to this rule is Piranha, in which case you add H₂O₂, which is a very strong base, to H₂SO₄, which is a very strong acid. This is done because it is potentially explosive and at the very least will cause the solution to become very warm.