Specific Process Knowledge/Etch/Wet III-V Etches
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This is a collection of III-V wet-etches; the rates should be tested before use. Make sure you have the proper education in mixing of chemicals before use. Wet etching of III-V materials is primarily to be done in 'Fume hood 07: III-V acids/bases'. Contact information, risk assessment and manual regarding this fume hood can be found in LabManager:
Fume hood 07 Info page in LabManager
It is very important that you dispose off chemicals and process waste according to DTU Nanolab regulations and risk assessments for your work.
For the GaAs and InP substrate etching, waste should be collected and marked Carcinogenic. If it contains H2O2 use empty H2O2 bottles (since they should have a special lid that avoid over pressure).
There should be waste bottles in the fumehood for citric acid: H2O2 or H2SO4 (10%):H2O2 used to etch GaAs and InGaAsP substrates marked "for Carcinogenic materials like InP and GaAs in Acid and Hydrogenperoxide". And one for acid etch of InP marked "for Carcinogenic materials like InP and GaAs in Acid - NO H2O2"
This does not apply for etching epilayers.
If you need a new bottle, contact Nanolab.
For dry etching III-V materials see
- III-V ICP
- III-V RIE - Plassys (will be decommissioned October 2025)
HCl:H3PO4 etch
HCl(37%):H3PO4(85%) is a selective, anisotropic and slow etching of InP. Very slow rate in InGaAsP. The etch rates depend on the orientation of the features and have not yet been calibrated at DTU Nanolab.
See rates below for InP, PQ(1.n) and InGaAs lattice-matched to InP. The acronym PQ(1.n) denotes a lattice-matched InGaAsP on InP with a band gap corresponding to a wavelength of 1.n um.
The temperature is 22 degC +/- 1 degC.
H2SO4:H2O2:H2O etch
H2SO4(10%):H2O2(30%):H2O is a selective etch of InGaAsP with very low etch rate in InP. The acronym PQ(1.n) denotes a lattice-matched InGaAsP on InP with a band gap corresponding to a wavelength of 1.n um.
The etch rates have not yet been calibrated at DTU Nanolab. The temperature is 22 degC +/- 1 degC.
Concentrated H2SO4
Concentrated H2SO4(98%) is used for deoxidation of InP with a very low etch rate in InGaAsP.
| H2SO4(98%) etch rates, nm/min | |||||
|---|---|---|---|---|---|
| Etchant | InP | PQ(1.1) | PQ(1.3) | PQ(1.5) | InGaAs |
| H2SO4(98%) | 13 | ? | <1 | ||
H3PO4:H2O2:H2O etch
H3PO4(85%):H2O2(30%):H2O is a GaAs/AlGaAs-etch which gives a better surface quality than H2SO4-based etches.
BHF, HF etch
BHF etches SiO2 and partially removes native oxide on InGaAs and InP. Do not use BHF unless you know the dangers involved with this chemical and always use 4H gloves!.
Citric Acid etch
C6H8O7:H2O2 is a selective etch of GaAs; does not etch AlxGa{1-x}As if x > 0.45.
Solid C6H8O7 is mixed 1:1 by weight with H2O using magnetic stirring. The solution C6H8O7:H2O is thereafter mixed 4:1 volume ratio with H2O2(30%).
The above C6H8O7:H2O2 solution has an etch-rate of ~360 nm/min in GaAs and < 0.5 nm/min in AlAs @ 25 degC.
More info regarding etching of III-V materials
More info on etching of III-V materials (not the DTU Nanolab wiki) can be found here:
https://wiki.nanofab.ucsb.edu/wiki/Wet_Etching_Recipes (at the UCSB Nanofab Wiki)
and
https://www.sciencedirect.com/science/article/pii/S0927796X00000279 (at the UCSB Nanofab Wiki)