Oxygen Plasma System Recipes
Back to Dry Etching Recipes.
Ashers (Technics PEII)
CF4/O2 PEii
Gas is CF4 / O2 (88%/12%)
SiN Etching
- Pressure = 300mT–350mT
- Power = 100W
- Etch Rate ≈ 50-100 nm/min. Varies.
Chamber Clean after CF4 Etching
- Pressure = 300mT–350mT
- Power = 100W
- Time = 10min
O2 Ashing
O2; 300mT / 100W - on either Technics asher.
~15sec to make a surface hydrophilic, eg. before wet etching or applying photoreist.
~30-120sec to improve wirebonding pad metal prior to deposition of liftoff metal.
~1-5min to remove polymerized photoresist/scum after dry etching
~5-10min to strip ~0.5-1.0µm photoresist. Rotate wafer 180° halfway through etch. Optionally increase to 200W for faster etching.
Use glass slides to prevent wafers from sliding on platen.
Plasma Clean (Gasonics 2000)
Recipes are posted at the tool, with photoresist etch rates.
Plasma Clean (YES EcoClean)
Some negative photoresists (eg. UVN) do not strip well without ion bombardment (requiring Technics PEii or RIE/ICP instead). We believe that the UV exposure from plasma may increase hardening via crosslinking.
Recipe Temperature control is by the lift-pins , with hotplate at 200°C
N2/O2 Recipes
Recipe Names:
- TO BE RENAMED: "STD-N2-O2-180C-3kW-3min"
- These recipes used to be named “180C-3kW-3min”, prior to 2023-09-15.
- The new renamed recipes are identical, except have a 1x pump/purge added to the start of the cycle to improve repeatability.
- Variations: (underlined portion of filename)
- Temperature: 100C, 130C, 150C,180C
- Power: 3kW, 0.7kW
- 3kW is very fast for full PR strip, but often increases substrate temperature significantly.
- 0.7kW reduces substrate temperature, although exact values are not known.
- Time: Various times are available, with strings such as "30sec", "1min", "3min" etc.
Recipe Characterization:
3kW recipes appear to gradually heat wafers beyond the hotplate temperature, and also expose the underside of the wafer. Very efficient cleaning of positive photoresists, but exact temperature is unknown and may increase with time.
N2/O2 effect on Gold contacts & Substrate Temperature
These recipes, at both 3kW and 0.7kW, have a tendency to oxidize Gold, turning Gold contacts brown. The optical emission of the N2 plasma emits strongly in the visible, which is absorbed by many metals (especially Blue/UV), causing additional heating of the surface. If your devices contain gold contacts, or are very temperature sensitive, consider using our O2-only recipe below.
O2-Only Recipes
O2-only recipes do not oxidize gold contacts, and have been found to have stable/repeatable temperatures, and lower PR etch rates than N2-O2 recipes. See below for PR etch rates.
NOTE: The O2 plasma does not emit much light, because the plasma is remote. The tool is etching even if the porthole does not look brightly lit.
- Recipe Names: "STD-O2-100C-3kW-3min"
- Variations:
- Temperature: 100C, 130C, 150C, 180C
- Power: 3kW
- Time: Various times are available, with strings such as "30sec", "1min", "3min" up to "15min"
O2 Recipe Characterization
- O2 only recipes without N2 gas: SPR220-7 at 3kW various temperature
- Comparison of ash rate for O2-only vs O2/N2 mixture
- Gold surface oxidation (darkening) due to O2/N2 plasma; the need for O2 only recipes
Internal To Add: • PR Etch rates for each recipe
UV Ozone Reactor
The UV Ozone Reactor is used for two purposes:
- Etch away organic residue with no ion bombardment
- Oxidize surface (monolayers) of a substrate, which has been used for
- Providing a wet-etchable sacrifical surface layer which is removed prior to deposition or regrowth
- Controlled digital etching, by wet etching the oxide and then repeating the oxidation/etch cycle.
Plasma Activation (EVG 810)
O2 and N2 plasma activation recipes are available on this tool.
These are the qualified recipes provided by EVG and will not require adjustment of the RF Match:
