STS APS DGRIE/Processes/uk submicron etch
The uk submicron etch is designed for thin-film (up to 8 μm) etching of silicon dioxide. Etch rate up to 2600 Å/min, depending on feature size. The etch exhibits extremely vertical sidewalls and can achieve down to 100 nm feature resolution.
|About this Process|
|Equipment||STS APS DGRIE|
|Mask Materials||SPR 220, KMPR, Polysilicon|
|Gases Used||C4F8, He|
|Authored By||SPTS, Kevin Owen|
Follow the SOP as shown on the STS APS DGRIE page and choose the uk_submicron etch.
Etch rate is feature size dependent - smaller features will etch slower than larger ones. Bulk etch rate is approximately 2500 Å/min. The etch exhibits minimal loading effect.
- Thermal oxide: 2450 Å/min
- GSI Oxide 200C: 3500 Å/min
- GSI Oxide 350C: 3000 Å/min
- GSI Oxide 350 thin: 2900 Å/min
Etch uniformity is < 1% across a 6" wafer.
The etch rate of SPR 220 is approximately 1600 A/min (selectivity 1.5:1). Selectivity will be lower on smaller features, due to the decrease in oxide etch rate. This is the etch rate on a 6" wafer. Selectivity may be lower on samples/wafers mounted to a carrier due to increased sample heating.
- SPR 200: 1600 Å/min (selectivity 1.5:1)
- PMMA: approximately 1800 Å/min (selectivity ~1.3:1).
- Stoichiometric LPCVD silicon nitride (Si3N4): 1750 Å/min (selectivity 1.4:1).
- GSI nitride 200C: 2400 Å/min
- Poly-Si: 450 Å/min
The process has a standard 30sec Ar breakthrough which can be helpful to get through photoresist scum. If you are using very thin e-beam resist you many want to remove the breakthrough step.
The etch depths below are on 6" blanket films with the 30 sec breakthrough step.
- SPR 220 ː 59nm
- SiO2 ː 37nm
The etch may be run for a maximum of 30 minutes.
The bulk oxide etch rate is tested after each maintenance (every 1-2 weeks) by running a 2 min etch on an oxide coated 6" wafer and measured at 25 points around the wafer.