Oxford III-V
About
Films / Materials: This is an Oxford Instruments PlasmaPro 100 Cobra high-density plasma reactive ion etcher (ICP-RIE) optimized for III-V compound semiconductors (GaAs, InP, GaN, etc.), 2D materials (MoS₂, WSe₂, graphene), ITO, and other advanced semiconductors. It supports both room-temperature and cryogenic etching for smooth sidewalls, high selectivity, and low damage - critical for photonic, electronic, and quantum devices.
Hardware: Inductively Coupled Plasma (ICP) source with separate coil power (up to 1500 W) and table RF bias (up to 1500 W) at 13.56 MHz. Cryogenic cooling capability (down to -120°C) for reduced sidewall roughness and improved profiles in III-V etching, with heated operation up to 200°C. Helium backside cooling for temperature uniformity. 4" wafer clamp standard; carrier wafers for smaller pieces (2", 3", 6", 8" also possible). Load lock for contamination-free loading. Includes optical endpoint detection (Horiba Jobin Yvon LEM G50) for precise process termination.
Gases:
- Ar (argon – physical sputtering/milling component)
- O₂ (oxygen – for ashing, oxidation, or enhancing etch rates)
- SF₆ (sulfur hexafluoride – fluorine-based etching)
- CH₄ (methane – III-V etching with polymer control)
- H₂ (hydrogen – reduction or sidewall passivation)
- Cl₂ (chlorine – high-rate etching of III-Vs)
- BCl₃ (boron trichloride – chlorine-based etching with selectivity)
- SiCl₄ (silicon tetrachloride – specific III-V or Si etching)
Etch Properties:
- Smooth, vertical sidewalls (especially at cryogenic temperatures).
- High selectivity to masks (e.g., SiO₂, metals(Cr), resists).
- Low damage to III-V surfaces (important for optoelectronic performance).
- Tunable profiles via temperature, gas ratios, and bias power.
- Wide temperature range -120°C to 200°C allowed (-150°C to 400°C max) for process flexibility.
- Excellent process control for uniformity across up to 200 mm substrates.
Applications: Mesa etching for lasers, LEDs, and photodetectors (InP, GaAs, GaN); waveguide and photonic crystal fabrication; nanowire and quantum dot definition; etching of 2D materials (MoS₂, WSe₂, graphene); ITO patterning for transparent electrodes; high-selectivity etches in compound semiconductor devices. Not for exposed metals (except Cr) or deep polymer etches; polymer may be used as a mask only.
Usage: Load wafer (4" clamp or carrier for smaller pieces), pump down through load lock, select/load recipe, set temperature (cryo or heated), power, and gas flows, then run process. Use endpoint detection for timed or auto-stop processes. Monitor profile, sidewall smoothness, and damage post-etch (e.g., via SEM, AFM, or PL).
Detailed Specifications
- Model: PlasmaPro 100 Cobra III-V etcher
- Location: Etch Bay 1
- Substrate size: 4" wafer clamp standard; pieces/smaller on carrier wafers; 2", 3", 4", 6", 8" possible
- ICP coil power (max): 1500 W (13.56 MHz)
- Table RF bias power (max): 1500 W (13.56 MHz)
- Table temperature: --120°C to 200°C allowed (-150°C to 400°C max --> cryogenic cooling + helium backside cooling)
- Gases:
- Ar (max) 100 sccm
- O₂ (max) 50 sccm
- SF₆ (max) 100 sccm
- CH₄ (max) 50 sccm
- H₂ (max) 100 sccm
- Cl₂ (max) 100 sccm
- BCl₃ (max) 100 sccm
- SiCl₄ (max) 50 sccm
- Features: Cryogenic capability, helium backside cooling, optical endpoint detection (Horiba Jobin Yvon LEM G50), load lock, high selectivity and low damage for III-Vs and 2D materials
Restrictions and Materials Allowed
| Restrictions | Materials Allowed |
|---|---|
|
|
Safety & Emergency
Required PPE: Safety glasses, cleanroom gloves, bunny suit.
Toxic gases used: Cl₂, BCl₃, SiCl₄, SF₆, CH₄, H₂ O - chlorine and fluorine byproducts (HCl, HF) possible; CH₄ and H₂ are flammable. Do not open chamber if gas alarm is active.
If the tool alarms or gas cabinet shows red: Press EMO (Emergency Machine Off) - red button on the front panel. Evacuate Etch Bay 1 and notify staff immediately.
Call Nanofab staff: Chandan Ramakrishnaiah, +1 (213) 551-6726. After hours / life-threatening: USC DPS (213) 740-4321, or 911.
Gas leak or chemical exposure: Activate bay alarm, exit cleanroom, call DPS.
Chamber vent failure: Do NOT force open. Leave tool and contact staff.
Dry Etcher Comparison
Use this table to help choose the right etching tool for your process.
| Feature | Oxford RIE | Oxford DRIE | Oxford DRIE-ALE | Oxford III-V | XeF2 Etcher |
|---|---|---|---|---|---|
| Model | PlasmaPro 80 RIE | Oxford System 100 DRIE | Oxford DRIE + ALE | PlasmaPro 100 Cobra | Custom built (Armani group) |
| Location | Etch Bay 1 | Etch Bay 1 | Etch Bay 1 | Etch Bay 1 | Deposition Bay 1 |
| Substrate Size | Up to 200 mm (8") | Up to 4" clamp; 2", 3", 4", 6", 8" possible | Up to 4" clamp; 2", 3", 4", 6", 8" possible | Up to 4" clamp; 2", 3", 4", 6", 8" possible | Up to 6" |
| Etch Type | RIE (capacitively coupled) | DRIE / Bosch (ICP) | DRIE + Atomic Layer Etch | ICP-RIE (cryo capable) | Isotropic chemical etch |
| Table RF Power | 300 W max | 300 W max | 300 W max | 1500 W max | N/A |
| ICP Power | None (RIE only) | 3000 W max | 3000 W max | 1500 W max | N/A |
| Table Temperature | 20°C | 20°C | -120°C to 200°C allowed
(-150°C to 400°C max) |
-120°C to 200°C allowed
(-150°C to 400°C max) |
20°C |
| Gases | Ar, O₂, CF₄, CHF₃, SF₆ | Ar, O₂, CF₄, CHF₃, SF₆, C₄F₈ | Ar, O₂, C₄F₈, SF₆, BCl₃, Cl₂, H₂, N₂O, CH₄, CF₄, CHF₃ | Ar, O₂, SF₆, CH₄, H₂, Cl₂, BCl₃, SiCl₄ | XeF₂ (crystal source) |
| Allowed Materials | Si, SiO₂, Si₃N₄, oxide/nitride masks, Cr | Si, SiO₂, SiN, Parylene, Polyimide, LiNbO₃, BCB | InP, InAs, GaN, AlGaAs, GaAs, InGaAsP, ITO, Si, SiC, MoS₂, WSe, Graphene | InP, InAs, GaN, AlGaAs, GaAs, InGaAsP, ITO, Si, SiC, MoS₂, WSe, Graphene | Si only |
| Disallowed | No metals except Cr; no deep polymer >1 µm | No exposed metals except Cr | No metals except Cr; no deep polymer >1 µm | No metals except Cr; no deep polymer >1 µm | None listed |
| Endpoint Detection | Optical (LEM G50) | Not Available | TBD | Optical (LEM G50) | Not Available |
| Best For | Dielectric etching, passivation removal, via openings, resist descum | Deep Si etching, high-aspect-ratio structures, Bosch process | Precise atomic-layer-level etch control | III-V semiconductors, exotic/compound materials, cryo etching | Fast isotropic Si etching, high selectivity |
| Status | Operational | Operational | Operational | Operational | Operational |
| SOP | SOP | SOP | TBD | SOP | SOP |
Documentation
- SOP
- Quickstart Guide
- OES SOP
- Laser Endpoint SOP
- Training required – contact lab staff (Chandan Ramakrishnaiah) Request form
Recipes & Data
- Standard Recipes: Standard Recipe (GaAs/InP mesas with Cl₂/BCl₃/Ar, GaN with Cl₂/Ar, cryo Si etch, 2D material patterning)
- Process Control and Calibration Data: Standard Recipe Calibration
Recipe Control Charts
- GaAs/InP Etch Control Chart
- GaN Etch Control Chart
Troubleshooting
- Plasma won't ignite
- Check gas flows are stable, pressure is in range, and both ICP coil and RF bias matching networks are tuned.
- Etch rate dropped suddenly
- Chamber may need conditioning. Run an O₂/SF₆ clean recipe for 30 min.
- Endpoint detector not triggering
- Verify Horiba LEM G50 is on, lens is clean, correct wavelength is selected. See OES SOP.
- Chamber pressure won't drop
- Possible vacuum leak or pump issue. Stop process, notify staff.
Acknowledgment
If results from this tool appear in a publication, please acknowledge the facility:
"This work was performed in part at the USC Nanofab at the University of Southern California, Michelson Center for Convergent Bioscience."
Please also email the citation to chandanr@usc.edu so we can track facility output.