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'''Feedback to this page''': '''[mailto:wetchemistry@danchip.dtu.dk?Subject=Feed%20back%20from%20page%20http://labadviser.danchip.dtu.dk/index.php/Specific_Process_Knowledge/Etch/Wet_Silicon_Oxide_Etch_(BHF) click here]'''
'''Feedback to this page''': '''[mailto:labadviser@nanolab.dtu.dk?Subject=Feed%20back%20from%20page%20http://labadviser.nanolab.dtu.dk/index.php/Specific_Process_Knowledge/Etch/Wet_Silicon_Oxide_Etch_(BHF) click here]'''


'''''Unless anything else is stated, everything on this page, text and pictures are made by DTU Nanolab.'''''


==Wet Silicon Oxide Etch (BHF, HF and SIO Etch (wetting agent))==
'''''All links to Kemibrug (SDS) and Labmanager Including APV, requires login.'''''


Silicon oxide can be etched using HF. At Danchip it is mainly used in a buffered version BHF (premixed). You can find the KBA [http://kemibrug.dk/KBA/CAS/106534/?show_KBA=1&portaldesign=1 here] The BHF has a more stable etch rate and is more gentle to photoresist due to an almost pH neutral solution which makes photoresist a good masking material for the oxide etch.
[[Category: Equipment|Etch Wet Silicon Oxide]]
[[Category: Etch (Wet) bath|Silicon Oxide]]


SIO etch (BHF with wetting agent) can also be used for etching silicon oxide. This is mainly for etching small holes. If you have wetting problems in BHF try the SIO etch. It is also a good idea to wet the sample in water for a few minutes before etching.
==Wet Silicon Oxide Etch (BHF, HF and BOE 7:1 Etchant VLSI with Surfactant (wetting agent))==


Wafers with metals or other materials, not allowed in the dedicated oxide etch baths, can be etched in the PP-bath positioned in the fume hood in cleanroom 2 or in a '''plastic''' beaker.  
Silicon oxide can be etched using HF. At DTU Nanolab it is mainly used in a buffered version BHF (premixed). You can find safety datasheets on Kemibrug [http://kemibrug.dk here] The BHF has a more stable etch rate and is more gentle to photoresist due to an almost pH neutral solution which makes photoresist a good masking material for the oxide etch.
 
BOE 7:1 Etchant VLSI with Surfactant (BHF with wetting agent) can also be used for etching silicon oxide. This is mainly for etching small holes. If you have wetting problems in BHF try the BOE 7:1 Etchant VLSI with Surfactant. It is also a good idea to wet the sample in water for a few minutes before etching.
 
Wafers with metals or other materials, not allowed in the dedicated oxide etch baths, can be etched using a '''plastic''' in Fume hood 01 or 02 (Acids/bases) in D-3. Samples with III-V materials (e.g. InP and GaAs) must be etched in Fume hood 07: III-V Avids/bases in D-3.
<br>
 
'''The user manual for Oxide etch 1: BHF, APV's and contact information can be found in LabManager''' [http://labmanager.dtu.dk/function.php?module=Machine&view=view&mach=389 by clicking here]
 
'''The user manual for Oxide etch 2: BHF (clean), APV's and contact information can be found in LabManager''' [http://labmanager.dtu.dk/function.php?module=Machine&view=view&mach=378 by clicking here]
 
'''The user manual for Oxide etch 3: 10% HF, APV's and contact information can be found in LabManager''' [http://labmanager.dtu.dk/function.php?module=Machine&view=view&mach=380 by clicking here]
 
'''The user manual for various HF baths in RCA and Fume hoods, APV's and contact information can be found in LabManager''' [http://labmanager.dtu.dk/function.php?module=Machine&view=view&mach=64 by clicking here]
 
'''<big>Working with HF above 13% is only allowed by Nanolab staff</big>'''


'''The user manual for all HF/BHF baths, APV's and contact information can be found in LabManager''' [http://labmanager.danchip.dtu.dk/function.php?module=Machine&view=view&mach=64 by clicking here]
<!-- remember to remove the type of documents that are not present -->
<!-- remember to remove the type of documents that are not present -->
'''Process information:''' <br>
See more [[/BHF etch rates|etch rates]] in HF solutions.




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!colspan="2" border="none" style="background:silver; color:black;" align="center"|Etchant  
!colspan="2" border="none" style="background:silver; color:black;" align="center"|Etchant  
|style="background:WhiteSmoke; color:black"|<b>[[Specific_Process_Knowledge/Etch/Wet_Silicon_Oxide_Etch_(BHF)#Comparing_different_BHF_baths|BHF]]</b>
|style="background:WhiteSmoke; color:black"|<b>[[Specific_Process_Knowledge/Etch/Wet_Silicon_Oxide_Etch_(BHF)#Comparing_different_BHF_baths|BHF]]</b>
|style="background:WhiteSmoke; color:black"|<b>[[Specific_Process_Knowledge/Etch/Wet_Silicon_Oxide_Etch_(BHF)#Comparing_different_5.25_HF_baths|5% HF]]</b>
|style="background:WhiteSmoke; color:black"|<b>[[Specific_Process_Knowledge/Etch/Wet_Silicon_Oxide_Etch_(BHF)#Comparing_different_5.25_HF_baths|1% HF / 5% HF / 10% HF]]</b>
|style="background:WhiteSmoke; color:black"|<b>[[Specific_Process_Knowledge/Etch/Wet_Silicon_Oxide_Etch_(BHF)#Comparing_different_40.25_HF_baths|40% HF]]</b>
|style="background:WhiteSmoke; color:black"|<b>[[Specific_Process_Knowledge/Etch/Wet_Silicon_Oxide_Etch_(BHF)#Comparing_different_40.25_HF_baths|40% HF]]</b>
|style="background:WhiteSmoke; color:black"|<b>[[Specific_Process_Knowledge/Etch/Wet_Silicon_Oxide_Etch_(BHF)#SiO_etch_bath|SiO etch]]</b>
|style="background:WhiteSmoke; color:black"|<b>[[Specific_Process_Knowledge/Etch/Wet_Silicon_Oxide_Etch_(BHF)#SiO_etch_bath|BOE 7:1 Etchant VLSI with Surfactant]]</b>
|-
|-
!style="background:silver; color:black;" align="center" width="60" rowspan="2"|Purpose  
!style="background:silver; color:black;" align="center" width="60" rowspan="2"|Purpose  
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*Mainly for removing native oxide
*Mainly for removing native oxide
|style="background:WhiteSmoke; color:black"|
|style="background:WhiteSmoke; color:black"|
*Mainly for etching deep into borofloat or quartz wafers
*Mainly for etching deep into borofloat or quartz wafers. '''Only Nanolab staff are allowed to work with this HF'''.
|style="background:WhiteSmoke; color:black"|
|style="background:WhiteSmoke; color:black"|
*Etching of silicon oxide - especially for etching small holes
*Etching of silicon oxide - especially for etching small holes
|-
|-
|style="background:LightGrey; color:black"|Link to safety APV and KBA
|style="background:LightGrey; color:black"|Link to safety APV and SDS (You must be logged in to Kemibrug to view SDSs)
|style="background:WhiteSmoke; color:black"|
|style="background:WhiteSmoke; color:black"|
*:[http://labmanager.danchip.dtu.dk/d4Show.php?id=1897&mach=64 see APV here]
*:[http://labmanager.nanolab.dtu.dk/d4Show.php?id=1897&mach=64 see APV here]
*:[http://kemibrug.dk/KBA/CAS/106534/?show_KBA=1&portaldesign=1 see KBA here]
*:[https://kemibrug.dk/Kemikalier/Action?id=RCU2MHolYzIlODIlN2UlYzIlODB2JWMyJTgxJTdleiVjMiU4N0RZeiVjMiU4OXYlN2UlYzIlODElYzIlODhESkhKSUxMVGQlYzIlODclN2N2JWMyJTgzJTdlJWMyJTg4diVjMiU4OSU3ZSVjMiU4NCVjMiU4MyVjMiU4OCU1ZVlSSQ==#K see SDS here]
|style="background:WhiteSmoke; color:black"|
|style="background:WhiteSmoke; color:black"|
*:[http://labmanager.danchip.dtu.dk/d4Show.php?id=1897&mach=64 see APV here]
*:[http://labmanager.danchip.dtu.dk/d4Show.php?id=1897&mach=64 see APV here]
*:[http://kemibrug.dk/KBA/CAS/106231/?show_KBA=1&portaldesign=1 see KBA here]
*:[https://kemibrug.dk/Kemikalier/Action?id=RCU2MHolYzIlODIlN2UlYzIlODB2JWMyJTgxJTdleiVjMiU4N0RZeiVjMiU4OXYlN2UlYzIlODElYzIlODhERkZMSkhFR1RkJWMyJTg3JTdjdiVjMiU4MyU3ZSVjMiU4OHYlYzIlODklN2UlYzIlODQlYzIlODMlYzIlODglNWVZUkk=#K see SDS here]
|style="background:WhiteSmoke; color:black"|
|style="background:WhiteSmoke; color:black"|
*:[http://labmanager.danchip.dtu.dk/d4Show.php?id=2479&mach=146 see APV here]
*:[http://labmanager.danchip.dtu.dk/d4Show.php?id=2479&mach=146 see APV here]
*:[http://kemibrug.dk/KBA/CAS/100648/?lang=da&show_KBA=1&portaldesign=1 see KBA here]
*:[https://kemibrug.dk/Kemikalier/Action?id=RCU2MHolYzIlODIlN2UlYzIlODB2JWMyJTgxJTdleiVjMiU4N0RZeiVjMiU4OXYlN2UlYzIlODElYzIlODhERkZMSkhOSVRkJWMyJTg3JTdjdiVjMiU4MyU3ZSVjMiU4OHYlYzIlODklN2UlYzIlODQlYzIlODMlYzIlODglNWVZUkk=#K see SDS here]
|style="background:WhiteSmoke; color:black"|
|style="background:WhiteSmoke; color:black"|
*:[http://labmanager.danchip.dtu.dk/d4Show.php?id=1897&mach=64 see APV here]
*:[http://labmanager.danchip.dtu.dk/d4Show.php?id=1897&mach=64 see APV here]
*:[http://kemibrug.dk/KBA/CAS/106534/?show_KBA=1&portaldesign=1 see KBA here]
*:[https://kemibrug.dk/Kemikalier/Action?id=RCU2MHolYzIlODIlN2UlYzIlODB2JWMyJTgxJTdleiVjMiU4N0RZeiVjMiU4OXYlN2UlYzIlODElYzIlODhERkVKS0lNTFRkJWMyJTg3JTdjdiVjMiU4MyU3ZSVjMiU4OHYlYzIlODklN2UlYzIlODQlYzIlODMlYzIlODglNWVZUkk=#K see SDS here]
|-
|-
!style="background:silver; color:black" align="center" valign="center" rowspan="3"|Performance
!style="background:silver; color:black" align="center" valign="center" rowspan="3"|Performance
Line 58: Line 78:
*Isotropic
*Isotropic
|-
|-
|style="background:LightGrey; color:black"|Etch rates
|style="background:LightGrey; color:black"|Etch rates  
[[/BHF etch rates|See more]]
|style="background:WhiteSmoke; color:black"|
|style="background:WhiteSmoke; color:black"|
*Wet thermal oxide:~80nm/min  
*Wet thermal oxide:75-80nm/min  
*PECVD1 (standard):~147nm/min
*TEOS:~265nm/min
*Stoichiometric Si3N4:~0.75nm/min (Morten Bo Mikkelsen, March 2013)
|style="background:WhiteSmoke; color:black"|
|style="background:WhiteSmoke; color:black"|
*Wet thermal oxide:~25nm/min  
*Wet thermal oxide:~6nm/min(1%) / 25nm/min(5%) / 52nm/min(10%)
*PECVD1 (standard):~87nm/min
*TEOS:~153nm/min
|style="background:WhiteSmoke; color:black"|
|style="background:WhiteSmoke; color:black"|
*Boronfloat and quartz: ~3-4 μm/min
*Boronfloat and quartz: ~3-4 μm/min
|style="background:WhiteSmoke; color:black"|
|style="background:WhiteSmoke; color:black"|
*A little higher etch rates than BHF
*Thermal oxide 80 nm/min
|-
|-
|style="background:LightGrey; color:black"|Lifetime of photoresist
|style="background:LightGrey; color:black"|Lifetime of photoresist
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|style="background:LightGrey; color:black"|Chemical solution
|style="background:LightGrey; color:black"|Chemical solution
|style="background:WhiteSmoke; color:black"|
|style="background:WhiteSmoke; color:black"|
*BHF 12%HF with Ammoniumflouride
*BHF (12%HF with Ammoniumflouride)
|style="background:WhiteSmoke; color:black"|
|style="background:WhiteSmoke; color:black"|
*5% HF
*1% / 5% HF
|style="background:WhiteSmoke; color:black"|
|style="background:WhiteSmoke; color:black"|
*40% HF
*40% HF
|style="background:WhiteSmoke; color:black"|
|style="background:WhiteSmoke; color:black"|
*SiO etch (BHF with a wetting agent)
*BOE 7:1 Etchant VLSI with Surfactant (BHF with a wetting agent)
|-
|-
|style="background:LightGrey; color:black"|Temperature
|style="background:LightGrey; color:black"|Temperature
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*Silicon nitride
*Silicon nitride
*Poly silicon
*Poly silicon
*photoresist
*Photoresist
*Blue film
*Blue film
|style="background:WhiteSmoke; color:black"|
|style="background:WhiteSmoke; color:black"|
*Silicon nitride
*Silicon nitride
*Poly silicon
*Poly silicon
*photoresist
*Photoresist
*Blue film
*Blue film
|style="background:WhiteSmoke; color:black"|
|style="background:WhiteSmoke; color:black"|
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*Silicon nitride
*Silicon nitride
*Poly silicon
*Poly silicon
*photoresist
*Photoresist
*Blue film
*Blue film
|-
|-
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<br clear="all" />
<br clear="all" />


<gallery caption="Different places to do wet silicon oxide etch" widths="220px" heights="225px" perrow="5"> image:BHF clean RR3.jpg|BHF clean in Cleanroom3. Wet silicon oxide etch bath positioned to the left in the bench.
<gallery caption="Different places to do wet silicon oxide etch" widths="420px" heights="425px" perrow="5"> image:BHF clean.JPG|BHF in wetbench 04 in D-3 (Oxide etch 2: BHF (clean)). Wet silicon oxide etch bath positioned to the right in the wetbench. This bath can also be used for BHF with wetting agent.  
image:KOH_4tommer.jpg|BHF in Cleanroom 3 (KOH bench 1+2.) The BHF bath is positioned between the two KOH baths. This is primarily used to remove oxide before and after a KOH etch.  
image:KOH_BHF.JPG|BHF in wetbench 01 Si etch in D-3 (Oxide etch 1: BHF). The BHF bath is positioned in the middle of the bench. This is primarily used to remove oxide before and after a Si etch.
image:KOH3 RR4 1.JPG|BHF in Cleanroom 4 (KOH bench 6".) The BHF bath is positioned to the right. This is primarily used to remove oxide before and after a KOH etch.
image:BHF clean.JPG|BHF in wetbench 05 in D-3 (Oxide etch 3: 10% HF). Wet silicon oxide etch bath positioned to the right in the wetbench. This bath can also be used for BHF, BHF with wetting agent or 40% HF on request. This bath is also used for cleaning quarts carriers from the PECVD4 system.
image:BHF-PolySi-Al Etch.jpg|SIO etch bath (BHF with wetting agent) are positioned to the left in the bench in cleanroom 4.  
image:RCA-HF.jpg|HF baths in RCA bench in B-1. These may only be used together with RCA cleaning and furnace processes.
image:Stinkskab RR2.jpg|PP-bath: positioned in the upper right corner of the fumehood in cleanroom 2. </gallery>
</gallery>




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|-style="background:silver; color:black"
|-style="background:silver; color:black"
!  
!  
! BHF clean in Cleanroom3
! BHF (KOH) in D-3(Oxide etch 1: BHF)
! BHF in Cleanroom3 (KOH bench 1+2)
! BHF clean in D-3 (Oxide etch 2: BHF)
! BHF in Cleanroom4 (KOH bench 6”)
! BHF in RCA Bench
! BHF in RCA Bench
! BHF in PP-bath
! BHF in PP-bath
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|1-25 wafers at a time
|1-25 wafers at a time
|1-25 wafer at a time
|1-25 wafer at a time
|1-25 wafers at a time
|1-25 wafers at a time
|1-25 wafers at a time
|1-25 wafers at a time
|1-25 wafers at a time
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|-style="background:LightGrey; color:black"
|-style="background:LightGrey; color:black"
!Size of substrate
!Size of substrate
|2"-4" wafers
|2"-6" wafers
|2"-4" wafers
|2"-6" wafers
|2"-6" wafers
|2"-6" wafers
|2"-6" wafers
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|-style="background:WhiteSmoke; color:black"
|-style="background:WhiteSmoke; color:black"
!Allowed materials
!Allowed materials
|
*Silicon
*Poly Silicon
*Silicon Oxide
*Silicon Nitride
*Silicon Oxynitride
*Photoresist
*Blue film
|
|
*Silicon
*Silicon
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|-style="background:LightGrey; color:black"
|-style="background:LightGrey; color:black"
!Restrictions
!Restrictions
|Wafers have to be cleaned in 7UP or RCA before further processing.
|No wafers with metal are allowed in this bath
|No wafers with metal are allowed in this bath
|Wafers have to be cleaned in 7UP or RCA before further processing.
|Wafers have to be cleaned in 7UP or RCA before further processing.
|Only for wafers with phosphor glass or boron glass that comes directly from one of the furnaces in stack A. All other substrates and material are strictly forbidden to go into the tank.
|Only for wafers with phosphor glass or boron glass that comes directly from one of the furnaces in stack A. All other substrates and material are strictly forbidden to go into the tank.
|None
|None
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<br clear="all" />
<br clear="all" />


==Comparing different 5% HF baths==
==Comparing different HF baths==
{|border="1" cellspacing="1" cellpadding="3" style="text-align:left;"  
{|border="1" cellspacing="1" cellpadding="3" style="text-align:left;"  
|-
|-
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|-style="background:silver; color:black"
|-style="background:silver; color:black"
!  
!  
! 5% HF in RCA Bench
! 1% HF in RCA Bench
! 5% HF PP-bath
! 10% HF in D3 wet bench 5 (Oxide etch 3)
! 5% HF Plastic beaker
! 1% HF Plastic beaker


|-  
|-  
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!Size of substrate
!Size of substrate
|2"-6" wafers
|2"-6" wafers
|2"- 4" wafers or any that fits in a dedicated holder
|2"- 6" wafers or any that fits in a dedicated holder
|2"- 4" wafers or any that fits in a dedicated holder
|2"- 4" wafers or any that fits in a dedicated holder
|-
|-
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<br clear="all" />
<br clear="all" />


==Comparing different 40% HF baths==
==40% HF==
{|border="1" cellspacing="1" cellpadding="3" style="text-align:left;"  
{|border="1" cellspacing="1" cellpadding="2" style="text-align:left;"  
|-
|-


|-style="background:silver; color:black"
|-style="background:silver; color:black"
!  
!  
! 40% HF PP-bath
! 40% HF in Plastic beaker, only done by Nanolab staff
! 40% HF Plastic beaker


|-  
|-  
|-style="background:WhiteSmoke; color:black"
|-style="background:WhiteSmoke; color:black"
!Batch size!
!Batch size!
|1-25 wafers at a time
|1 wafer at a time
|1 wafer at a time
|-
|-
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|-style="background:LightGrey; color:black"
|-style="background:LightGrey; color:black"
!Size of substrate
!Size of substrate
|Any that fits to a dedicated holder
|Any that fits to a dedicated holder
|Any that fits to a dedicated holder
|-
|-
|-style="background:WhiteSmoke; color:black"
|-style="background:WhiteSmoke; color:black"
!Allowed materials
!Allowed materials
|All materials
|All materials  
|All materials  
|-
|-
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<br clear="all" />
<br clear="all" />


==SiO etch bath==
==BOE 7:1 Etchant VLSI with Surfactant bath==
{|border="1" cellspacing="1" cellpadding="3" style="text-align:left;"  
{|border="1" cellspacing="1" cellpadding="3" style="text-align:left;"  
|-
|-
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|-style="background:silver; color:black"
|-style="background:silver; color:black"
!  
!  
! SiO etch bath
! BOE 7:1 Etchant VLSI with Surfactant bath
|-  
|-  
|-style="background:WhiteSmoke; color:black"
|-style="background:WhiteSmoke; color:black"
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*Silicon oxides  
*Silicon oxides  
*Photoresist
*Photoresist
 
|-
|-style="background:WhiteSmoke; color:black"
!Remark
|
Amorphous silicon can be used as a mask fro SiO2 etching.<br/>
For very long and deep etches of SiO2/Quartz (several hours/micrometers) <br/>
we have indications that show that it is not good to use the BOE 7:1 Etchant VLSI with Surfactant etch. <br/>
The amorphous silicon has small holes (etch pits) which the BOE 7:1 Etchant VLSI with Surfactant etch penetrates and the SiO2 below is etched.
|-
|-
|}
|}
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