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= Modification of showerhead in december 2014 =
'''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/DRIE-Pegasus/nanoetch click here]'''
<!--Checked for updates on 14/5-2018 - ok/jmli -->
<!-- Page reviewed 9/8-2022 jmli -->
<!--Checked for updates on 4/9-2025 - ok/jmli -->


The showerhead that distributes the process gasses inside the plasma source has been changed. With the new design the gas flow resistance in the gas line from MFC to plasma has been reduced. This has very little or no impact on processes that have a continuous gas flow - i.e. processes that are not switched. However, for processes with several gas flows that switch on and off, the switching from one gas flow to another will be much more well defined. This enables us to run Bosch processes with shorter cycles times. Shorter cycles times means smaller scallops and hence lower roughness and better control.


As stated, we believe that only switched processes will be affected by this change. Continuous processes such as [[Specific Process Knowledge/Etch/DRIE-Pegasus/processC|Process C]], [[Specific Process Knowledge/Etch/DRIE-Pegasus/nanoetch/nano142|Nano1.42]], isotropic etches, barc etches or the black silicon recipes are not believed to be noticeably affected.
= Modification of showerhead on Pegasus 1 in december 2014 =
{{Template:Author-jmli1}}
<!--Checked for updates on 2/02-2023 - ok/jmli -->


= Comparison of continuous processes =
This page describes why the showerhead has been changed and what process changes have been found.


== Black silicon recipe ==
== Motivation ==
 
The showerhead that distributes the process gasses inside the Pegasus plasma source was changed. In the old design, the showerhead had a number of holes intended to distribute the gas uniformly inside the plasma source. The passage through the holes had a flow resistance that would cause the gasses coming from the MFC in a Bosch process to get mixed up - in this way working against the separation of the etch and dep cycles.
 
In the new design, the gas flow resistance has been reduced by increasing the diameter holes in the showerhead instead. This has no impact on processes that have a continuous gas flow - i.e. processes that are not switched. However, for processes with several gas flows that switch on and off, the switching from one gas flow to another will be much more well defined. This has enabled us to run Bosch processes with shorter cycles times. Shorter cycles times means smaller scallops and hence lower roughness and better control. We have not seen any changes to the uniformity of the plasma nor any other side effect. The modification was also done on Pegasus 2 and 3 before we started using them.
 
== Comparison of continuous processes on Pegasus 1==
 
=== Black silicon recipe ===


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= Comparison of switched processes =  
== Comparison of switched processes on Pegasus 1==  




== Process A ==
=== Process A ===


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== SOI ==
=== SOI ===




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== Process D ==
=== Process D ===




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| [[Specific Process Knowledge/Etch/DRIE-Pegasus/showerheadchange/ProcessD/PrD-4 | 1]]      <!-- link processes -->
| [[Specific Process Knowledge/Etch/DRIE-Pegasus/showerheadchange/ProcessD/PrD-4 | 1]]      <!-- link processes -->
| Best one so far!  <!-- keywords -->
| Best one so far!  <!-- keywords -->
|-
|}
== Polysilicon etch ==
{| border="1" cellpadding="1" cellspacing="0" style="text-align:center;"
|-
! rowspan="2" width="100"| Recipe description
! rowspan="2" width="20"| Name
! rowspan="2" width="20"| Temp.
! colspan="6" | Deposition step
! colspan="7" | Etch step
! colspan="3" | Comments
|-
! Time
! Pres.
! C<sub>4</sub>F<sub>8</sub>
! SF<sub>6</sub>
! O<sub>2</sub>
! Coil
! Time
! Pres.
! C<sub>4</sub>F<sub>8</sub>
! SF<sub>6</sub>
! O<sub>2</sub>
! Coil
! Platen
! Showerhead
! Runs
! width="100" | Key words
|-
! rowspan="7" | Polysilicon etch    <!-- recipe name -->
! polySi etch DUV mask  <!-- step -->
| 30      <!-- chiller temp -->
! 2.3      <!-- dep time -->
| 10      <!-- dep pressure -->
| 50      <!-- C4F8 flow -->
| 0      <!-- SF6 flow -->
| 0    <!-- O2 flow -->
| 600      <!-- coil power -->
| 5.0      <!-- etch time -->
| 10      <!-- etch pressure -->
| 20      <!-- C4F8 flow -->
| 60      <!-- SF6 flow -->
| 5      <!-- O2 flow -->
| 400      <!-- coil power -->
| 40      <!-- platen power -->
! Old      <!-- Showerhead -->
| [[Specific Process Knowledge/Etch/DRIE-Pegasus/showerheadchange/polySi/Cduv | 1]]      <!-- link processes -->
| Slightly over-etching to ensure complete absence of grass  <!-- keywords -->
|-
| polySi etch DUV mask  <!-- step -->
| 30      <!-- chiller temp -->
| 2.3      <!-- dep time -->
| 10      <!-- dep pressure -->
| 50      <!-- C4F8 flow -->
| 0      <!-- SF6 flow -->
| 0    <!-- O2 flow -->
| 600      <!-- coil power -->
| 5.0      <!-- etch time -->
| 10      <!-- etch pressure -->
| 20      <!-- C4F8 flow -->
| 60      <!-- SF6 flow -->
| 5      <!-- O2 flow -->
| 400      <!-- coil power -->
| 40      <!-- platen power -->
! New      <!-- Showerhead -->
| [[Specific Process Knowledge/Etch/DRIE-Pegasus/showerheadchange/polySi/Cduv | 1]]      <!-- link processes -->
|    <!-- keywords -->
|-
| Cpoly1      <!-- step -->
| 30      <!-- chiller temp -->
! 1.2      <!-- dep time -->
| 10      <!-- dep pressure -->
| 50      <!-- C4F8 flow -->
| 0      <!-- SF6 flow -->
| 0    <!-- O2 flow -->
| 600      <!-- coil power -->
| 5.0      <!-- etch time -->
| 10      <!-- etch pressure -->
| 20      <!-- C4F8 flow -->
| 60      <!-- SF6 flow -->
| 5      <!-- O2 flow -->
| 400      <!-- coil power -->
| 40      <!-- platen power -->
! New      <!-- Showerhead -->
| [[Specific Process Knowledge/Etch/DRIE-Pegasus/showerheadchange/polySi/Cpoly1 | 1]]      <!-- link processes -->
| Very aggressive, unusable  <!-- keywords -->
|-
| Cpoly2      <!-- step -->
| 30      <!-- chiller temp -->
! 1.4      <!-- dep time -->
| 10      <!-- dep pressure -->
| 50      <!-- C4F8 flow -->
| 0      <!-- SF6 flow -->
| 0    <!-- O2 flow -->
| 600      <!-- coil power -->
| 5.0      <!-- etch time -->
| 10      <!-- etch pressure -->
| 20      <!-- C4F8 flow -->
| 60      <!-- SF6 flow -->
| 5      <!-- O2 flow -->
| 400      <!-- coil power -->
| 40      <!-- platen power -->
! New      <!-- Showerhead -->
| [[Specific Process Knowledge/Etch/DRIE-Pegasus/showerheadchange/polySi/Cpoly2 | 1]]      <!-- link processes -->
|    <!-- keywords -->
|-
| Cpoly3      <!-- step -->
| 30      <!-- chiller temp -->
! 1.6      <!-- dep time -->
| 10      <!-- dep pressure -->
| 50      <!-- C4F8 flow -->
| 0      <!-- SF6 flow -->
| 0    <!-- O2 flow -->
| 600      <!-- coil power -->
| 5.0      <!-- etch time -->
| 10      <!-- etch pressure -->
| 20      <!-- C4F8 flow -->
| 60      <!-- SF6 flow -->
| 5      <!-- O2 flow -->
| 400      <!-- coil power -->
| 40      <!-- platen power -->
! New      <!-- Showerhead -->
| [[Specific Process Knowledge/Etch/DRIE-Pegasus/showerheadchange/polySi/Cpoly3 | 1]]      <!-- link processes -->
|    <!-- keywords -->
|-
| Cpoly4      <!-- step -->
| 30      <!-- chiller temp -->
! 1.8      <!-- dep time -->
| 10      <!-- dep pressure -->
| 50      <!-- C4F8 flow -->
| 0      <!-- SF6 flow -->
| 0    <!-- O2 flow -->
| 600      <!-- coil power -->
| 5.0      <!-- etch time -->
| 10      <!-- etch pressure -->
| 20      <!-- C4F8 flow -->
| 60      <!-- SF6 flow -->
| 5      <!-- O2 flow -->
| 400      <!-- coil power -->
| 40      <!-- platen power -->
! New      <!-- Showerhead -->
| [[Specific Process Knowledge/Etch/DRIE-Pegasus/showerheadchange/polySi/Cpoly4 | 1]]      <!-- link processes -->
|    <!-- keywords -->
|-
| Cpoly5      <!-- step -->
| 30      <!-- chiller temp -->
! 2.0      <!-- dep time -->
| 10      <!-- dep pressure -->
| 50      <!-- C4F8 flow -->
| 0      <!-- SF6 flow -->
| 0    <!-- O2 flow -->
| 600      <!-- coil power -->
| 5.0      <!-- etch time -->
| 10      <!-- etch pressure -->
| 20      <!-- C4F8 flow -->
| 60      <!-- SF6 flow -->
| 5      <!-- O2 flow -->
| 400      <!-- coil power -->
| 40      <!-- platen power -->
! New      <!-- Showerhead -->
| [[Specific Process Knowledge/Etch/DRIE-Pegasus/showerheadchange/polySi/Cpoly5 | 1]]      <!-- link processes -->
|    <!-- keywords -->
|-
|-
|}
|}
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