STS Pegasus 4/Processes/LNF Recipe 3
 Warning: | This page has not been released yet. |
| About this Process | |
|---|---|
| Process Details | |
| Equipment | STS Pegasus 4 |
| Technology | DRIE |
| Material | Si |
| Mask Materials | PR, SiO2 |
| Gases Used | SF6, C4F8, O2 |
| Date Created | Jan 1, 2011 |
| Authored By | Kevin Owen |
Recipe 3 is designed for deep and through wafer etching particularly on masks with a large exposed area (>20%). Undercut and scalloping is larger than LNF Recipe 1, but etch rates are higher (4-16 μm/min).
Contents
Procedure
Run LNF Recipe 3 for up to 20 minutes with the 1 minute automated clean recipe, longer etches should be run with the 3 minute automated clean recipe.
Recipe Parameters
| Parameter | Dep | Etch |
|---|---|---|
| ICP Power | W | W |
| Bias Power | W | W |
| Bias Pulsing | ||
| Pressure | mTorr | mTorr |
| C4F8 Flow | sccm | sccm |
| SF6 Flow | sccm | sccm |
| O2 Flow | sccm | sccm |
| Time | s | s |
Characterization
Etch Rate
The etch rate will vary with the size of the trench being etched. Larger trenches tend to etch faster, this trend can be seen below.
Recipe 3 Etch Rate vs. Feature Size
Mask Selectivity
Side Profile
Trench
Running recipe 3 for 20 minutes with 3 µm of SPR 220 on a silicon wafer with our standard DRIE characterization mask can produce a profile like this.
Recipe 3 for 20 min, 2 µm Trench
Recipe 3 for 20 min, 10 µm Trench
Recipe 3 for 20 min, 100 µm Trench
Scallop
- 0.46 µm wide X 2.2 µm tall
Undercut
- 483 nm
Grassing
An example of grassing can be seen below. This can happen if there is too much exposed area (>25%) on the mask.
Grass (brown area) on perimeter of wafer
XXX find some SEM of grass XXX
Limitations
Etch Length
Feature Size
Aspect ratio
Open area
Multi-step etching
- Multi-step processing (i.e. running two or more etches with overlapping features) with the Bosch process is known to cause undesirable results. Please contact the tool engineers if you wish to run such a process so we can help reduce or eliminate issues.
Qualification
Every third Friday Recipe 3 is run for 10 minutes on a Si wafer with our standard DRIE characterization mask, with 3 µm of SPR 220. This is performed after the weekly clean, and a 100 µm trench is measured in 5 locations with the Zygo NewView 5000. This etch rate is reported in the chart below.
