STS Pegasus 4/Processes/LNF Recipe 4
|Warning:||This page has not been released yet.|
|About this Process|
|Equipment||STS Pegasus 4|
|Mask Materials||PR, SiO2|
|Gases Used||SF6, C4F8, O2|
|Date Created||Jan 1, 2011|
|Authored By||Kevin Owen|
This highly specialized recipe is designed for high aspect ratio etching of small features (1-5 μm) with very low open area (<10%). The etch produces the most vertical sidewall with the least undercut, particularly at the top of the trench. It is primarily used with trench refill processes.
Run LNF Recipe 4 for up to 20 minutes with the 1 minute automated clean recipe, longer etches should be run with the 3 minute automated clean recipe.
|ICP Power||2000 W||2500 W|
|Bias Power||0 W||80-100 W*||30 W|
|Bias Pulsing||N/A||40 Hz 80%|
|Pressure||25 mTorr||30 mTorr|
|C4F8 Flow||90-140 sccm*||0 sccm|
|SF6 Flow||0 sccm||110 sccm|
|O2 Flow||0 sccm||10 sccm|
|Time||2.5 s||3 s||4 s|
* Ramped through process. Must be adjusted according to process time.
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.
- Photoresist Etch Rate
- SPR 220: 600 A/min
- Thermal oxide/HTO: unknown
Running recipe 4 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. The minimum trench size is 0.24 µm.
- 80 nm wide X 300 nm tall
- 225 nm
An example of grassing can be seen below. This can happen if there is too much exposed area (>25%) on the mask.
Feature sizes of 1-10 μm (exposed) are known to work well. Larger features may cause grass.
An exposed area of <10% across the wafer is recommended. Larger exposed area may cause grass.
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.
Currently Recipe 4 is not routinely qualified.