View source for Specific Process Knowledge/Wafer cleaning

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

== Cleaning of wafers ==

During processing it is sometimes mandatory, necessary or just recommended to clean the wafers or photo lithographic masks. This can be done by different cleaning procedures depending on what the wafers have been exposed to and where they are going to be further processed. As a general rule all wafers that go into the high temperature furnaces need a RCA clean directly before the furnace step. Wafers that have been etched in KOH is often transferred directly to the warm phosphoric acid for nitride strip. Therefore wafers that have been in the KOH baths, KOH BHF baths or the warm phosphoric acid always need at minimum a 7-up or Piranha clean before they can be further processed. Items that have been outside the cleanroom should always be cleaned in soap and ultra sound followed by a 7-up or Piranha clean before entering the cleanroom. Masks that has become dirty by dust particles and resist residues have to be cleaned in the 7-up (mask) bath before use. Sometimes the wafers need to be cleaned before they can enter certain equipments due to risk of cross contamination. Please consult the cross contamination scheme to see whether your wafers need a cleaning before the next processing sequence.

<br \>

==Comparison of Wafer Cleaning Methods==

{|border="1" cellspacing="1" cellpadding="3" style="text-align:left;" 
|-

|-
|-style="background:silver; color:black"
!
![[Specific Process Knowledge/Wafer cleaning/RCA|RCA]]
![[Specific Process Knowledge/Wafer cleaning/7-up & Piranha|7-up & Piranha]]
![[Specific Process Knowledge/Wafer cleaning/cleaning with HF|5% HF]]
![[Specific Process Knowledge/Wafer cleaning/IMEC|IMEC]]
![[Specific Process Knowledge/Wafer cleaning/Cleaning with Soap Sonic|Soap Sonic]]
|-

|-
|-style="background:WhiteSmoke; color:black"
!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
|-

|-
|-style="background:LightGrey; color:black"
!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.
|-

|-
|-style="background:WhiteSmoke; color:black"
!Substrate size
|
*<nowiki>#</nowiki>1-25 2", 4" and 6" wafers
|
*<nowiki>#</nowiki>1-25 2", 4" and 6" wafers
|
*<nowiki>#</nowiki>1-25 2", 4" and 6" wafers
|

*<nowiki>#</nowiki>1-25 2" and 4" wafers
|
*All sizes that can go into the bath
|-

|-
|-style="background:LightGrey; 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 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
|-

|}