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'''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/processB click here]'''
<!--Checked for updates on 28/6-2023 - ok/jmli -->
<!--Checked for updates on 2/10-2020 - ok/jmli -->
<!--Checked for updates on 14/5-2018 - ok/jmli -->
<!--Checked for updates on 4/9-2025 - ok/jmli -->
{{contentbydryetch}}
== Process B ==
Process B was run on a 150 mm wafer with 12-13 % etch load.
{| border="2" cellpadding="2" cellspacing="1" style="text-align:center;"
{| border="2" cellpadding="2" cellspacing="1" style="text-align:center;"
|+ '''Process A specifications'''
|+ '''Process B specifications'''
|-
|-
! Parameter
! Parameter
Line 7: Line 18:
|-
|-
! Etch rate (µm/min)   
! Etch rate (µm/min)   
| > 15
| > 10
| 18.9
| 10.7
|-
|-
! Etched depth (µm)
! Etched depth (µm)
| 150
| 100
| 189.1
| 107
|-
|-
! Scallop size (nm)
! Scallop size (nm)
| < 800
| < 800
| 718
| 685
|-
|-
! Profile (degs)
! Profile (degs)
| 91 +/- 1
| 91 +/- 1
| 91.1
| 90.7
|-
|-
! Selectivity to AZ photoresist  
! Selectivity to AZ photoresist  
| > 150
| > 100
| 310
| 183
|-
|-
! Undercut (µm)
! Undercut (µm)
| <1.5
| <1.5
| 0.84
| 0.89
|-
|-
! Uniformity (%)
! Uniformity (%)
| < 3.5
| < 3.5
| 3.0
| 2.7
|-
|-
! Repeatability (%)
! Repeatability (%)
| <4
| <4
| 0.43
| 0.47
|-
|-
|}
|}
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{| border="2" cellpadding="2" cellspacing="1" style="text-align:center;"
{| border="2" cellpadding="2" cellspacing="1" style="text-align:center;"
|+ '''Process A recipe'''
|+ '''Process B recipe'''
|-
|-
!
! colspan="2" | Step 1
! colspan="2" | Step 2
|-
|-
! width="120" | Parameter  
! width="120" | Main etch (D->E)  
! width="120" | Etch
! width="120" | Dep
! width="120" | Etch
! width="120" | Etch
! width="120" | Dep
! width="120" | Dep
|-
|-
! Gas flow (sccm)  
! Gas flow (sccm)  
| SF<sub>6</sub> 350 (1.5 s) 550
| SF<sub>6</sub> 350 O<sub>2</sub> 35
| C<sub>4</sub>F<sub>8</sub> 200
| SF<sub>6</sub> 350 (1.5 s) 550
| C<sub>4</sub>F<sub>8</sub> 200
| C<sub>4</sub>F<sub>8</sub> 200
|-
|-
! Cycle time (secs)  
! Cycle time (secs)  
| 7.0
| 4.0
| 7.0
| 7.0
| 4.0
| 4.0
|-
|-
! Pressure (mtorr)  
! Pressure (mtorr)  
| 25 (1.5 s) 90 >> 150
| 20 (1.5 s) 100
| 25
| 25 (1.5 s) 150
| 25
| 25
|-
|-
! Coil power (W)  
! Coil power (W)  
| 2800  
| 2800  
| 2000
| 2800
| 2000
| 2000
|-
|-
! Platen power (W)
! Platen power (W)
| 120 >> 140 (1.5) 45
| 130 (1.5) 40
| 0
| 0
| 140 (1.5) 45
| 0
|-
|-
! Cycles   
! Cycles   
| colspan="2" | 11 (keep fixed)
| colspan="2" | 55 (process time 10:05)
| colspan="2" | 44 (vary this)
|-
|-
! Common  
! Common  
| colspan="4" | Temperature 20 degs, HBC 10 torr, Short funnel, with baffle & 5mm spacers
| colspan="2" | Temperature 10 degs, HBC 10 torr, Short funnel, with baffle & 5mm spacers
|}
 
 
== Experiment with process B performance ==
 
=== Purpose ===
 
Perhaps the most commonly occuring question posed by users of the dry etch tools is something like ' I want to etch my trenches down to a depth of 40 microns, how long should I etch?'. The answer is that it depends on the width of the trench and on the etch load of your design (that is how many percent of the wafer it etched).
 
An experiment has been set up to investigate the etched depth of a number of different trenches (with widths ranging from 2 microns to 300 microns) as a function of etch load (the exposed area ranges from 5 % to 65 %)
 
=== Results ===
 
A number of wafers are patterned with the [[Specific Process Knowledge/Pattern Design/Travka|Travka mask set]] in 4 microns of AZ photoresist. The wafers are then etched using two different durations of process B in the DRIE-Pegasus.
 
{|
| STYLE="vertical-align: top"|
{| border = 1
|+ '''Wafers'''
|-
! width="70" |Wafer number
! width="70" |Mask
! Process B duration
|-
| 2
| Travka 05
| 17 cycles, 3:07 mins
|-
| 3
| Travka 05
| 34 cycles, 6:14 mins
|-
| 5
| Travka 10
| 17 cycles, 3:07 mins
|-
| 6
| Travka 10
| 34 cycles, 6:14 mins
|-
| 8
| Travka 20
| 17 cycles, 3:07 mins
|-
| 9
| Travka 20
| 34 cycles, 6:14 mins
|}
| STYLE="vertical-align: top"|
{| border = 1
|+ '''Wafers'''
|-
! width="70" |Wafer number
! width="70" |Mask
! Process B duration
|-
| 11
| Travka 35
| 17 cycles, 3:07 mins
|-
| 12
| Travka 35
| 34 cycles, 6:14 mins
|-
| 14
| Travka 50
| 17 cycles, 3:07 mins
|-
| 15
| Travka 50
| 34 cycles, 6:14 mins
|-
| 17
| Travka 65
| 17 cycles, 3:07 mins
|-
| 18
| Travka 65
| 34 cycles, 6:14 mins
|}
|}
|}
After etching each wafer is cleaved in two places: Both cleavage lines run across the [[Specific Process Knowledge/Pattern Design/Travka/fields/Aline|A-line fields]]. This produces three sites on each wafer where the depth of the trenches can be determined using an SEM.
<gallery caption="The results of process B after 17 and 34 cycles of etching"  widths="500" heights="350" perrow="2">
image:Travkatesting1a.jpg|
image:Travkatesting1b.jpg|
</gallery>
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