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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.


== 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 ===


{| border="1" cellpadding="1" cellspacing="1" style="text-align:center;"
{| border="1" cellpadding="1" cellspacing="1" style="text-align:center;"
Line 39: Line 52:
| [[file:S004679 edge.jpg |250px|frameless ]]
| [[file:S004679 edge.jpg |250px|frameless ]]
|-
|-
! width="100"| Continuous isotropic silicon etch called isoslow7
| width="100"| 1 minute, 10 degrees, 10 mTorr, 80 SF<sub>6</sub>, 150 W coil, 3 W platen
| S003900
| 4" wafer, 50 % load
|
[[file:S003900-01.jpg |120px|frameless ]]
[[file:S003900-02.jpg |120px|frameless ]]
[[file:S003900-03.jpg |120px|frameless ]]
[[file:S003900-04.jpg |120px|frameless ]]
[[file:S003900-05.jpg |120px|frameless ]]
[[file:S003900-06.jpg |120px|frameless ]]


| S00XXX
| No test yet
| [[file:S00XX centre.jpg |250px|frameless ]]
|-
|}
|}


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




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


{| border="1" cellpadding="1" cellspacing="0" style="text-align:center;"
{| border="1" cellpadding="1" cellspacing="0" style="text-align:center;"
Line 159: Line 157:
|}
|}


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




Line 229: Line 227:
|}
|}


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




Line 391: Line 389:
| [[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 -->
|-
|-
|}
|}

Latest revision as of 09:32, 4 September 2025

Feedback to this page: click here


Modification of showerhead on Pegasus 1 in december 2014

Unless otherwise stated, all content on this page was created by Jonas Michael-Lindhard, DTU Nanolab

This page describes why the showerhead has been changed and what process changes have been found.

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

Process Before (Old showerhead) After (New showerhead)
Name/Type Description/parameters Wafer ID Comment SEM images Wafer ID Comment SEM images
Continuous black silicon recipe on blank wafer 15 mins, -10 degrees, 32 mtorr, 60 sccm SF6, 55 sccm O2, 70 W platen S004592 Wafer centre S004679 Wafer centre
S003900 Wafer edge S004679 Wafer edge

Comparison of switched processes on Pegasus 1

Process A

Recipe Name Temp. Deposition step Etch step Comments
Time Pres. C4F8 SF6 O2 Coil Time Pres. C4F8 SF6 O2 Coil Platen Showerhead Runs Key words
Process A Step1 11 cyc 20 4 25 200 0 0 2000 7.0 25(1.5s) 90>>150 0 350(1.5s) 550 5 2800 120>>140(1.5s) 45 Old 1
Step2 44 cyc 4 25 200 0 0 2000 7.0 25(1.5s) 150 0 350(1.5s) 550 5 2800 140(1.5s) 45
Step1 11 cyc 20 4 25 200 0 0 2000 7.0 25(1.5s) 90>>150 0 350(1.5s) 550 5 2800 120>>140(1.5s) 45 New 1 Profile improved
Step2 44 cyc 4 25 200 0 0 2000 7.0 25(1.5s) 150 0 350(1.5s) 550 5 2800 140(1.5s) 45

SOI

Recipe Name Temp. Deposition step Etch step Comments
Time Pres. C4F8 SF6 O2 Coil Time Pres. C4F8 SF6 O2 Coil Platen Showerhead Runs Key words
SOI etch SOI 20 2 25 250 0 0 2000 3 30 0 400 40 2800 75 (0.025s, 75%) Old 1
SOI 20 2 25 250 0 0 2000 3 30 0 400 40 2800 75 (0.025s, 75%) New 1 OK

Process D

Recipe Name Temp. Deposition step Etch step Comments
Time Pres. C4F8 SF6 O2 Coil Time Pres. C4F8 SF6 O2 Coil Platen Showerhead Runs Key words
Process D Original 0 2 20 150 0 0 2000 2.4 26 0 275 5 2500 35 Old 1
Original 0 2 20 150 0 0 2000 2.4 26 0 275 5 2500 35 New 1
New Process D 0 1 20 150 0 0 2000 3 26 0 275 5 2500 35 New 4 Large undercut
PrD01 0 1 20 150 0 0 2000 2.4 26 0 275 5 2500 35 New 2
PrD02 0 1.1 20 150 0 0 2000 2.4 26 0 275 5 2500 35 New 1
PrD-3 0 1 20 150 0 0 2000 2.5 26 0 275 5 2500 35 New 1
PrD-4 0 1 20 150 0 0 2000 2.2 26 0 275 5 2500 35 New 1 Best one so far!
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