View source for Specific Process Knowledge/Wafer cleaning/7-up & Piranha

'''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==

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 user manual, user APV and contact information can be found in LabManager:'''
<!-- remember to remove the type of documents that are not present -->
[http://labmanager.danchip.dtu.dk/function.php?module=Machine&view=view&mach=135 7-up 6" info page in LabManager] or [http://labmanager.danchip.dtu.dk/function.php?module=Machine&view=view&mach=69 7-up (masks) info page in LabManager]

'''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===

{| border="2" cellspacing="0" cellpadding="4" align="left" width="570pt"
|-style="background:silver; color:black"
! 
! 7-up wafers
! 7-up Masks
! Piranha
|- 
|-style="background:WhiteSmoke; color:black"
|'''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.
|-
|-style="background:LightGrey; color:black"
|'''Chemical solution'''
|98% Sulfuric acid and Ammonium sulfate
|98% Sulfuric acid and Ammonium sulfate
|98% Sulfuric acid and Hydrogen peroxide 4:1 add H<sub>2</sub>O<sub>2</sub> to H<sub>2</sub>SO<sub>4</sub> (See [{{fnb|1}}] )
|-
|-style="background:WhiteSmoke; color:black"
|'''Process temperature'''
|80 <sup>o</sup>C
|80 <sup>o</sup>C
|~70 <sup>o</sup>C the chemicals will heat up to working temperature during mixing, '''therefore be careful!''' First ad H<sub>2</sub>SO<sub>4</sub> then H<sub>2</sub>O<sub>2</sub><sup>{{fn|1}}</sup>.
|-
|-style="background:LightGrey; color:black"
|'''Process time'''
|10 min.
|10 min.
|10 min.
|-
|-style="background:WhiteSmoke; color:black"
|'''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).
|-
|-style="background:LightGrey; color:black"
|'''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
|-
|-style="background:WhiteSmoke; color:black"
|'''Size of substrate'''
|
4-6" wafers
|
4-6" wafers or 5" masks
|
All sizes that can fit into the beaker in a dedicated holder
|-
|}

{{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 H<sub>2</sub>O<sub>2</sub>, which is a very strong base, to H<sub>2</sub>SO<sub>4</sub>, 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.