Specific Process Knowledge/Etch/DRIE-Pegasus/processD
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Process D
In this section the original version of process D is described. Since the change of the showerhead in December 2014 an improved version of process D should be considered as well, see next section.
Mask information
- 1 µm of spin coated AZ5214E photoresist, no hardbake
- Patterned by UV lithography with the ‘Travka 50’ mask
- 50 % etch load
| Parameter | Specification | Average result |
|---|---|---|
| Etch rate (µm/min) | Not specified | 2.88 |
| Etched depth (µm) | 20-30 | 28.75 |
| Scallop size (nm) | < 30 | 46 |
| Profile (degs) | 85 +/- 5 | 89.7 |
| Selectivity to AZ photoresist | Not specified | 50 |
| Undercut (nm) | Not specified | 65 |
| Uniformity (%) | < 3.5 | 4.56-0.25 |
| Repeatability (%) | <4 |
| Main etch (D->E) | Etch | Dep |
|---|---|---|
| Gas flow (sccm) | SF6 275 O2 5 | C4F8 150 |
| Cycle time (secs) | 2.4 | 2.0 |
| Pressure (mtorr) | 26 | 20 |
| Coil power (W) | 2500 | 2000 |
| Platen power (W) | 35 | 0 |
| Cycles | 110 (process time 08:04) | |
| Common | Temperature 0 degs, HBC 10 torr, Long funnel, with baffle & 100 mm spacers | |
See results in the acceptance report: here.
Effects on Process D of showerhead change in December 2014
The effects of changing of the showerhead in December 2014 was investigated. Patterned wafers were processed before and after and the profile of the etched features were inspected in SEM.
Process D is intended to be used for imprinting purposes - that means smooth sidewalls at relatively shallow depths (that means 'not through wafer'). It is therefore natural to exploit the faster switching capability introduced with the new showerhead for this etch process. An improved version of Process D (called Process D4) was found - see the table below.
Click on the numbers in the 'Runs' column below to see the profiles.
| 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! | |