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==LPCVD (Low Pressure Chemical Vapor Deposition) Silicon Nitride==
'''Feedback to this page''': '''[mailto:labadviser@nanolab.dtu.dk?Subject=Feed%20back%20from%20page%20http://labadviser.nanolab.dtu.dk/index.php/Specific_Process_Knowledge/Thin_film_deposition/Furnace_LPCVD_Nitride click here]'''
[[image:DC_nyhed_3.jpg|300x300px|right|thumb|6" LPCVD nitride furnace (new nitride furnace) positioned in cleanroom 14]]
[[image:Furnace_nitride1.jpg|300x300px|right|thumb|LPCVD nitride furnace (old nitride furnace) positioned in cleanroom 2]]
At Danchip there are two LPCVD nitride furnaces for deposition of silicon nitride: A 6" furnace (installed in 2008) for deposition of stoichiometric nitride on 4" or 6" wafers and a 4" furnace (installed in 1995) for deposition of stoichiometric nitride and silicon rich (i.e. low stress) nitride on 4" wafers. In LabManager the two furnaces are named "Furnace: LPCVD nitride (6")" and "Furnace: LPCVD nitride", respectively. Please be aware of that it is not allowed to deposit silicon rich nitride in the 6" nitride furnace to avoid problems with particles. Both furnaces are Tempress horizontal furnaces.  


The LPCVD silicon nitride deposition is a batch process, where nitride can be deposited on a batch of up to 35 wafers (in the 6" nitride furnace) or 15 wafers (in the 4" nitride furnace) at a time. The deposition takes place at a temperature of 780-845 degrees Celsius and a pressure of 120-200 mTorr. The reactive gases are ammonia (NH<sub>3</sub>) and dichlorsilane (SiH<sub>2</sub>Cl<sub>2</sub>). The LPCVD nitride has a good step coverage, and the film thickness is very uniform over the wafers.
<i> Unless otherwise stated, this page is written by <b>DTU Nanolab internal</b></i>


At moment there is only a standard recipe for deposition of silicon rich nitride (SRN) on 4" wafers on the 4" nitride furnace. On the 6" nitride furnace there are two standard recipes for deposition of stoichiometric nitride (Si<sub>3</sub>N<sub>4</sub>), one for 4" wafers and one for 6" wafers.
[[Category: Equipment|Thin film F]]
[[Category: Thin Film Deposition|LPCVD nitride]]
[[Category: Furnaces|LPCVD nitride]]


To get information on how to operate the furnaces please read the user manuals which are uploaded to LabManager on the machine page or consult the Furnace group at Danchip (furnace@danchip.dtu.dk).
[[image:DC_nyhed_3.jpg|320x320px|right|thumb|6" LPCVD nitride furnace (E3) located in cleanroom E-6]]
[[image:Furnace_nitride1.jpg|300x300px|right|thumb|4" LPCVD nitride furnace (B2) located in cleanroom B-1]]


==Process Knowledge==
Please take a look at the process side to get more information about deposition of silicon nitride using an LPCVD furnace:
[[Specific Process Knowledge/Thin film deposition/Deposition of Silicon Nitride/Deposition of Silicon Nitride using LPCVD|Deposition of Silicon Nitride using LPCVD]]
<br clear="all" />


==Overview of the performance of LPCVD Silicon Nitride and some process related parameters==
==Deposition of Silicon Nitride using LPCVD==


{| border="2" cellspacing="0" cellpadding="10"  
DTU Nanolab has two LPCVD (Low Pressure Chemical Vapour Deposition) furnaces <!--[[Specific Process Knowledge/Thin film deposition/B2 Furnace LPCVD Nitride|LPCVD furnaces]]--> for deposition of silicon nitride:
|-
*A 4" furnace (installed in 1995) for deposition og stoichiometric nitride on 4 inch wafers.
!style="background:silver; color:black;" align="left"|Purpose
*A 6" furnace (installed in 2008) for deposition of low stress/silicon rich nitride on 4 inch and 6 inch wafers. Deposition of stoichiometric nitride on 4 inch wafers is also allowed in this furnace.
|style="background:LightGrey; color:black"|Deposition of silicon nitride  
In LabManager the two furnaces are named "Furnace: LPCVD nitride (4") (B2)" and "Furnace: LPCVD nitride (6") (E3)", respectively. Both furnaces are Tempress horizontal furnaces.
|style="background:WhiteSmoke; color:black"|Stoichiometry:
 
*Si<sub>3</sub>N<sub>4</sub> (only 6" nitride furnace at the moment)
Please check the cross contamination information in LabManager before you use any of the two furnaces.
*SRN (only 4" nitride furnace, only 4" wafers)
 
Si<sub>3</sub>N<sub>4</sub>: Stoichiometric nitride
The LPCVD silicon nitride deposition is a batch process, where nitride can be deposited on a batch of up to 15 wafers (in the 4" nitride furnace) or 25 wafers (in the 6" nitride furnace) at a time. The deposition takes place under vacuum (120-200 mTorr, depending on the process) and at high temperature (780-845 C, depending on the process). The reactive gases are ammonia (NH<sub>3</sub>) and dichlorsilane (SiH<sub>2</sub>Cl<sub>2</sub>).
 
The LPCVD nitride has a very good step coverage, and the film thickness is very uniform over the wafers.
 
 
'''The user manuals, quality control procedures and results, user APVs, technical information and contact information can be found in LabManager:'''
 
[http://labmanager.dtu.dk/function.php?module=Machine&view=view&mach=84 4" LPCVD nitride furnace (B2)]
 
[http://labmanager.dtu.dk/function.php?module=Machine&view=view&mach=250 6" LPCVD nitride furnace (E3)]
 
[https://labmanager.dtu.dk/d4Show.php?id=1926 Furnace computer manual]
 
 
== Manual for the furnace computer to the A, B, C and E stack furnaces ==
 
The A, B, C and E stack furnaces can be controlled either from a touch screen by each furnace or from a furnace computer. The user manual for the furnace computer can be found here:
 
[[media:Furnace_computer_manual.pdf|Manual for furnace computers for the A, B, C and E stack furnaces]]
 
 
<!--hide text
[[/Standard recipes, QC limits and results for the 4" nitride furnace|Standard recipes, QC limits and results for the 4" nitride furnace]]
<br/>
[[/Standard recipes, QC limits and results for the 6" nitride furnace|Standard recipes, QC limits and results for the 6" nitride furnace]]
<br/>
hide text-->
 
== Process information ==
 
*[[/Deposition of stoichiometric nitride using the 4" LPCVD nitride furnace|Deposition of stoichiometric nitride using the 4" LPCVD nitride furnace]]
*[[/Deposition of low stress nitride using the 4" LPCVD nitride furnace|Deposition of low stress nitride using the 4" LPCVD nitride furnace <span style="color:Red">(Low stress nitride depositions are no longer available in this furnace - use the 6" nitride furnace instead)</span>]]
 
*[[/Deposition of low stress nitride using the 6" LPCVD nitride furnace|Deposition of low stress nitride using the 6" LPCVD nitride furnace ]]
*[[/Deposition of stoichiometric nitride using the 6" LPCVD nitride furnace|Deposition of stoichiometric nitride using the 6" LPCVD nitride furnace <span style="color:Red">(4" wafers need a special permission using as a back up of 4" LPCVD nitride furnace, B2)</span>]]
 
*[[/Using LPCVD silicon nitride as a masking material for KOH etching|Using LPCVD silicon nitride as a masking material for KOH etching]]
 
==Equipment performance and process related parameters==
 
{| border="2" cellspacing="0" cellpadding="2"


SRN: Silicon rich nitride (low stress nitride)
!colspan="2" border="none" style="background:silver; color:black;" align="center"|Equipment
|style="background:WhiteSmoke; color:black"|<b>6" LPCVD nitride furnace (E3)</b>
|style="background:WhiteSmoke; color:black"|<b>4" LPCVD nitride furnace (B2)</b>
|-
|-
!style="background:silver; color:black" align="left" valign="top" rowspan="4"|Performance
!style="background:silver; color:black;" align="center"|Purpose
|style="background:LightGrey; color:black"|Film thickness
|style="background:LightGrey; color:black"|Deposition of
|style="background:WhiteSmoke; color:black"|
|style="background:WhiteSmoke; color:black"|
*Si<sub>3</sub>N<sub>4</sub>: ~0 - 1400Å
*Silicon rich (low stress) nitride
*SRN: ~ ~0 - 2800Å
*Stoichiometric nitride
Thicker layers have to be deposited over more runs
|style="background:WhiteSmoke; color:black"|
*Stoichiometric nitride
|-
|-
!style="background:silver; color:black" align="center" valign="center" rowspan="2"|Performance
|style="background:LightGrey; color:black"|Step coverage
|style="background:LightGrey; color:black"|Step coverage
|style="background:WhiteSmoke; color:black"|
|style="background:WhiteSmoke; color:black"|
*Good
*Very good
|style="background:WhiteSmoke; color:black"|
*Very good
|-
|-
|style="background:LightGrey; color:black"|Film quality
|style="background:LightGrey; color:black"|Film quality
|style="background:WhiteSmoke; color:black"|
|style="background:WhiteSmoke; color:black"|
*Deposition on both sides of the substrate
*Deposition on both sides of the substrate
*Dense film
*Dense film  
*Few defects
*Few defects
|style="background:WhiteSmoke; color:black"|
*Deposition on both sides of the substrate
*Dense film
*Very few defects
|-
|-
|style="background:LightGrey; color:black"|Nitride thickness uniformity
!style="background:silver; color:black" align="center" valign="center" rowspan="3"|Process parameter range
|style="background:LightGrey; color:black"|Temperature
|style="background:WhiteSmoke; color:black"|
|style="background:WhiteSmoke; color:black"|
6" nitride furnace (Si<sub>3</sub>N<sub>4</sub>):
*810-845 <sup>o</sup>C
*Uniformity within wafer: <2.5 %
The temperature vary over the furnace tube
*Wafer-to-wafer uniformity: <4.5 %
*Run-to-run uniformity: <3 %
4" nitride furnace (SRN):
*Uniformity within wafer: <2.5 %
*Wafer-to-wafer uniformity: <6 %
*Run-to-run uniformity: <3 %
|-
!style="background:silver; color:black" align="left" valign="top" rowspan="3"|Process parameter range
|style="background:LightGrey; color:black"|Process Temperature
|style="background:WhiteSmoke; color:black"|
|style="background:WhiteSmoke; color:black"|
6" nitride furnace (Si<sub>3</sub>N<sub>4</sub>):
*780-790 <sup>o</sup>C
*780-790 <sup>o</sup>C
*The process temperature vary over the furnace tube
The temperature vary over the furnace tube
4" nitride furnace (SRN):
*830-845 <sup>o</sup>C
*The process temperature vary over the furnace tube
|-
|-
|style="background:LightGrey; color:black"|Process pressure
|style="background:LightGrey; color:black"|Pressure
|style="background:WhiteSmoke; color:black"|
*150 mTorr
|style="background:WhiteSmoke; color:black"|
|style="background:WhiteSmoke; color:black"|
6" nitride furnace (Si<sub>3</sub>N<sub>4</sub>):
*200 mTorr
*200 mTorr
4" nitride furnace (SRN):
*120 mTorr
|-
|-
|style="background:LightGrey; color:black"|Gas flows
|style="background:LightGrey; color:black"|Gas flows
|style="background:WhiteSmoke; color:black"|
|style="background:WhiteSmoke; color:black"|
6" nitride furnace (Si<sub>3</sub>N<sub>4</sub>):
For Low stress nitride
*Dichlorsilane (SiH<math>_2</math>Cl<math>_2</math>): 30-33 sccm
*Dichlorsilane (SiH<sub>2</sub>Cl<sub>2</sub>): 200 sccm
*Ammonia (NH<math>_3</math>): 100-120 sccm
*Ammonia (NH<sub>3</sub>): 50 sccm
*The gas flows depend on whether nitride is deposited on 4" or 6" wafers
For Stoichiometric nitride on 6" wafers
4" nitride furnace (SRN):
*Dichlorsilane (SiH<sub>2</sub>Cl<sub>2</sub>): 45 sccm
*Dichlorsilane (SiH<math>_2</math>Cl<math>_2</math>): 80 sccm
*Ammonia (NH<sub>3</sub>): 180 sccm
*Ammonia (NH<math>_3</math>): 20 sccm
 
|style="background:WhiteSmoke; color:black"|
*Dichlorsilane (SiH<sub>2</sub>Cl<sub>2</sub>): 20 sccm
*Ammonia (NH<sub>3</sub>): 80 sccm
The gas flows depend on whether nitride is deposited on 4" or 6" wafers
|-
|-
!style="background:silver; color:black" align="left" valign="top" rowspan="2"|Substrates
!style="background:silver; color:black" align="center" valign="center" rowspan="3"|Substrates
|style="background:LightGrey; color:black"|Batch size
|style="background:LightGrey; color:black"|Batch size
|style="background:WhiteSmoke; color:black"|
|style="background:WhiteSmoke; color:black"|
6" nitride furnace:
*1-25 100 mm wafers
*1-25 4" or 6" wafers per run
*1-25 150 mm wafers
4" nitride furnace:
Including a test wafer
*1-15 4" wafers per run
|style="background:WhiteSmoke; color:black"|
*1-15 100 mm wafers
Including a test wafer
|-
|-
| style="background:LightGrey; color:black"|Substrate material allowed
| style="background:LightGrey; color:black"|Allowed materials
|style="background:WhiteSmoke; color:black"|
*Silicon wafers (new or RCA cleaned)
**with layers of silicon oxide or silicon (oxy)nitride
**from the A, B and E stack furnaces
*Quartz/fused silica wafers (RCA cleaned)
|style="background:WhiteSmoke; color:black"|
|style="background:WhiteSmoke; color:black"|
*Silicon wafers (new wafers or RCA cleaned wafers)
*Silicon wafers (new or RCA cleaned)
**with layers of silicon oxide or silicon (oxy)nitride  
**with layers of silicon oxide or silicon (oxy)nitride  
**from furnaces in stack A or B in cleanroom 2
**from the A, B and E stack furnaces
*Pure quartz (fused silica) wafers (RCA cleaned)
*Quartz/fused silica wafers (RCA cleaned)
|-  
|-  
|}
|}
<!--hide text
==Using LPCVD silicon nitride as a masking material for KOH etching==
Stoichiometric silicon nitride is mainly used as masking material for potassium hydroxide (KOH) etching. The etch rate of the nitride in 80 <sup>o</sup>C KOH is expected to be less than 1 Å/min.
There are regularly users having problems with pinholes in the silicon nitride after KOH etching. It is not always clear what the reasons are, but we suspect problems can arise due to
*too many or too large particles in the nitride.
*too rough handling of the wafers after the nitride deposition.
*too much stress between the nitride and the underlying layer.
===Our recommendations to try and avoid pinhole problems are:===
'''To avoid too many or too large particles in the nitride'''<br\>
*If possible, use the new nitride furnace to deposit stoichiometric nitride. In order to avoid problems with particles it is not allowed to deposit low stress nitride in this furnace, and the particles level is therefore low compared to the older nitride furnace.
*Before running a process keep in close contact with the Nanolab staff (especially the process specialist on the furnace) or take a look at the logbook to make sure that the nitride furnace is expected to be in a good state.
'''To avoid too rough handling of the wafers after the nitride deposition'''<br\>
*After the deposition handle the wafers with a clean glove on the edge of the wafers (no tweezers).
*Be careful not to scratch wafers with nitride (e.g. up against each other or on the spinner or the aligner).
*If you have nitride on the back side of a wafer while aligning, consider if you can protect it with e.g. a photoresist layer before loading it onto the aligner. Or use a non-vacuum aligner chuck with a big hole in the middle, so that the wafer is only laying on the edge. Avoid hard contact in the aligner if possible.
'''To avoid too much stress between the nitride and the underlying layer'''<br\>
*It is recommended to have a of silicon oxide layer between the silicon substrate and the nitride layer to reduce the stress level between the layers. The silicon nitride is then expected to have less tendency to break.
hide text-->
== Rules for storage and RCA cleaning of wafers to the B2 and E3 furnaces ==
*[[Specific_Process_Knowledge/Thermal_Process/Storage_and_cleaning_of_wafer_to_the_A,_B,_C_and_E_stack_furnaces|Storage and cleaning of wafer to the B2 and E3 furnaces]]

Latest revision as of 09:31, 6 February 2024

Feedback to this page: click here

Unless otherwise stated, this page is written by DTU Nanolab internal

6" LPCVD nitride furnace (E3) located in cleanroom E-6
4" LPCVD nitride furnace (B2) located in cleanroom B-1


Deposition of Silicon Nitride using LPCVD

DTU Nanolab has two LPCVD (Low Pressure Chemical Vapour Deposition) furnaces for deposition of silicon nitride:

  • A 4" furnace (installed in 1995) for deposition og stoichiometric nitride on 4 inch wafers.
  • A 6" furnace (installed in 2008) for deposition of low stress/silicon rich nitride on 4 inch and 6 inch wafers. Deposition of stoichiometric nitride on 4 inch wafers is also allowed in this furnace.

In LabManager the two furnaces are named "Furnace: LPCVD nitride (4") (B2)" and "Furnace: LPCVD nitride (6") (E3)", respectively. Both furnaces are Tempress horizontal furnaces.

Please check the cross contamination information in LabManager before you use any of the two furnaces.

The LPCVD silicon nitride deposition is a batch process, where nitride can be deposited on a batch of up to 15 wafers (in the 4" nitride furnace) or 25 wafers (in the 6" nitride furnace) at a time. The deposition takes place under vacuum (120-200 mTorr, depending on the process) and at high temperature (780-845 C, depending on the process). The reactive gases are ammonia (NH3) and dichlorsilane (SiH2Cl2).

The LPCVD nitride has a very good step coverage, and the film thickness is very uniform over the wafers.


The user manuals, quality control procedures and results, user APVs, technical information and contact information can be found in LabManager:

4" LPCVD nitride furnace (B2)

6" LPCVD nitride furnace (E3)

Furnace computer manual


Manual for the furnace computer to the A, B, C and E stack furnaces

The A, B, C and E stack furnaces can be controlled either from a touch screen by each furnace or from a furnace computer. The user manual for the furnace computer can be found here:

Manual for furnace computers for the A, B, C and E stack furnaces


Process information

Equipment performance and process related parameters

Equipment 6" LPCVD nitride furnace (E3) 4" LPCVD nitride furnace (B2)
Purpose Deposition of
  • Silicon rich (low stress) nitride
  • Stoichiometric nitride
  • Stoichiometric nitride
Performance Step coverage
  • Very good
  • Very good
Film quality
  • Deposition on both sides of the substrate
  • Dense film
  • Few defects
  • Deposition on both sides of the substrate
  • Dense film
  • Very few defects
Process parameter range Temperature
  • 810-845 oC

The temperature vary over the furnace tube

  • 780-790 oC

The temperature vary over the furnace tube

Pressure
  • 150 mTorr
  • 200 mTorr
Gas flows

For Low stress nitride

  • Dichlorsilane (SiH2Cl2): 200 sccm
  • Ammonia (NH3): 50 sccm

For Stoichiometric nitride on 6" wafers

  • Dichlorsilane (SiH2Cl2): 45 sccm
  • Ammonia (NH3): 180 sccm
  • Dichlorsilane (SiH2Cl2): 20 sccm
  • Ammonia (NH3): 80 sccm

The gas flows depend on whether nitride is deposited on 4" or 6" wafers

Substrates Batch size
  • 1-25 100 mm wafers
  • 1-25 150 mm wafers

Including a test wafer

  • 1-15 100 mm wafers

Including a test wafer

Allowed materials
  • Silicon wafers (new or RCA cleaned)
    • with layers of silicon oxide or silicon (oxy)nitride
    • from the A, B and E stack furnaces
  • Quartz/fused silica wafers (RCA cleaned)
  • Silicon wafers (new or RCA cleaned)
    • with layers of silicon oxide or silicon (oxy)nitride
    • from the A, B and E stack furnaces
  • Quartz/fused silica wafers (RCA cleaned)


Rules for storage and RCA cleaning of wafers to the B2 and E3 furnaces

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