Wet Etching Recipes
Revision as of 21:33, 15 June 2023 by John d (talk | contribs) (→Table of Wet Etching Recipes: added selective substrate removal recipes for GaAs/AlGaAs (from Garrett Cole), oxide removal dips for InP, GaAs (from memory))
Chemicals Available
- The Chemical Lists show stocked chemicals, photolithography chemicals, and how to bring new chemicals.
Table of Wet Etching Recipes
Use the ↑ ↓ Arrows in the header row to sort the entire table by material, selectivity, etchant etc.
| Material | Etchant | Rate (nm/min) | Anisotropy | Selective to | Selectivity | Ref. | Notes | Confirmed By/Date |
|---|---|---|---|---|---|---|---|---|
| InP | H3PO4:HCl = 3:1 | ~1000 | Highly | InGaAs | High | Lamponi (p.102) | Bubbles while etching | |
| InP | H3PO4:HCl = 3:1 | ~1000 | Highly | InGaAsP | High | Lamponi (p.102) | Bubbles while etching | |
| InGaAsP | To Be Added | InP | High | |||||
| InGaAs | To Be Added | InP | High | |||||
| GaAs | NH4OH:H2O2 = 1:30 | - | AlGaAs, Al%>>80% | High, AlGaAs ≥200nm | Garrett Cole | |||
| AlGaAs, Al ≥80% | HF:H2O = 1:20 | - | GaAs | High | Garrett Cole | |||
| Oxide of InP | NH4OH:H2O = 1:10 | 1min to remove | InP | unknown | Ning Cao | |||
| Oxide of GaAs | HCl:H2O = 1:10 | 1min to remove | GaAs | unknown | Demis D. John | |||
| Al2O3 (ALD Plasma 300C) | Developer: 300MIF | ~1.6 | None | Most non-Al Materials. | High | Measured in-house | Rate slows with time. | JTB |
| Al2O3 (ALD Plasma 300C) | Developer: 400K | ~2.2 | None | Most non-Al Materials. | High | Measured in-house | Rate slows with time. | JTB |
| Al2O3 (ALD Plasma 300C) | Developer: 400K (1:4) | ~1.6 | None | Most non-Al Materials. | High | Measured in-house | Rate slows with time. | JTB |
| Al2O3 (ALD Plasma 300C) | NH4OH:H2O2:H2O (1:2:50) | ~<0.5 | Measured in-house | Rate slows with time | JTB | |||
| Al2O3 (IBD) | HF ("Buffered HF Improved", Transene) | ~170 | None | Photoresist | High | Measured in-house | May need to increase adhesion with thin SiO2 layer, and 100°C baked HMDS. | Biljana Stamenic,
2017-12 |
| Al2O3 (IBD) | Developer: 726 MiF | 3.5 | None | Most non-Al Materials. | High | Measured in-house | Demis D. John,
2017-11 | |
| Al2O3 (AJA#4) | Developer: 300 MiF | 4.30 | None | Most non-Al Materials. | High | Measured in-house | Demis D. John
2018-02 | |
| SiO2 (PECVD #1) | HF ("Buffered HF Improved", Transene) | ~500 | None | Photoresist | High | Measured in-house | May need to increase adhesion with 100°C baked HMDS. | Biljana Stamenic
2017 |
| SiO2 (PECVD #2) | HF ("Buffered HF Improved", Transene) | ~500 | None | Photoresist | High | Measured in-house | May need to increase adhesion with 100°C baked HMDS. | Biljana Stamenic
2017 |
| SiO2 (IBD) | HF ("Buffered HF Improved", Transene) | ~350 | None | Photoresist | High | Measured in-house | Biljana Stamenic
2016 | |
| Si3N4 (PECVD#1) | HF ("Buffered HF Improved", Transene) | 85 | None | Photoresist | High | Measured in-house | Biljana Stamenic
2018-04 | |
| Si3N4 (PECVD#2) | HF ("Buffered HF Improved", Transene) | 35–45 | None | Photoresist | High | Measured in-house | Biljana Stamenic
2018-05 | |
| Si3N4 Low-Stress (PECVD#2) | HF ("Buffered HF Improved", Transene) | 35–50 | None | Photoresist | High | Measured in-house | Biljana Stamenic
2018-05 | |
| Si3N4 (IBD) | HF ("Buffered HF Improved", Transene) | 5–15 | None | Photoresist | High | Measured in-house | Biljana Stamenic
2014 | |
| Ta2O5 (IBD) | HF ("Buffered HF Improved", Transene) | 0.4 | None | Photoresist | High | Measured in-house | Biljana Stamenic
2016-12 | |
| TiO2 (IBD) | HF ("Buffered HF Improved", Transene) | 1.0–2.0 | None | Photoresist | High | Measured in-house | Biljana Stamenic
2014-12 | |
| Si (<100> crystalline) | KOH (45%) @ 87°C | ~730 | High, Crystallographic, ~55° | Low-Stress Si3N4 - either PECVD #2 or Commercial LPCVD Si3N4
Other Si3N4 also OK. |
LS-SiN: High
PR etches quickly, SiO2 etches slowly. |
Measured In-House
- Search online. |
Use the Covered, Heated vertical bath (Dedi cated bath in Bay 4). Slight Bubbler. | Brian Thibeault
2017 |
| Material | Etchant | Rate (nm/min) | Anisotropy | Selective to | Selectivity | Ref. | Notes | Confirmed By/Date |
Adding a new entry to the Table
When entering a new etch into the table:
- Make a row for every etchant used in the solution such that the information can be sorted by etchant. For example, the InP etch HCl:H3PO4(1:3) and H3PO4:HCl(3:1).
- Likewise, if etch is known to be selective to multiple materials the etch should have a row for each material. For example HCl:H3PO4(1:3) is selective to both InGaAs and InGaAsP.
This multiple entry method may seem laborious for the person entering a new etch, however the power of sorting by selective materials and chemicals in a table with all materials is great.
| Material | Etchant | Rate (nm/min) | Anisotropy | Selective to | Selectivity | Ref. | Notes | Confirmed by | Extra column |
|---|---|---|---|---|---|---|---|---|---|
| InP | H3PO4:HCl(3:1) | ~1000 | Highly | InGaAs | High | Lamponi (p.102) | Example | Jon Doe | Example |
| InP | H3PO4:HCl(3:1) | ~1000 | Highly | InGaAsP | High | Lamponi (p.102) | Example | Jon Doe | Example |
Wet Etching References
- Etch rates for Micromachining Processing (IEEE Jnl. MEMS, 1996) - includes tables of etch rates of numerous metals vs. various wet and dry etchants.
- Etch rates for micromachining-Part II (IEEE Jnl. MEMS, 2003) - expanded tables containing resists, dielectrics, metals and semiconductors vs. many wet etch chemicals.
- Guide to references on III±V semiconductor chemical etching - exhaustive list of wet etchants for etching various semiconductors, including selective etches.
- Transene's Chemical Compatibility Chart provides a useful quick-reference for which Transene etchants attack which materials.
- As a side-note, Transene provides many pre-mixed solutions that you can order, saving you the time and uncertainty of measuring/mixing such chemicals yourself. Make sure you check with us before ordering so we know how to handle the chemical before it arrives.
Compound Semiconductor Etching
Guide to references on III±V semiconductor chemical etching
Please add any confirmed etches from this reference to the The Master Table of Wet Etching (Include All Materials).
Metal Etching
- Selective Wet Etch of Cr over Ta using Cr Etchant
- Wet Etch of ITO using Heated, Diluted HCl Solution
Silicon etching
Etch rates for micromachining processing
Etch rates for micromachining processing-part II
Please add any confirmed etches from this reference to the The Master Table of Wet Etching (Include All Materials).
Organic removal
- Piranha Solution. Careful! Read about how to prepare and handle this safely:
- MIT's Piranha Solution safety document
- Harvard EHS's Handling Document
- Can be used for etching away Photoresist residues after dry etching
- PureStrip @ 70°C (Transene)
- Vertical heated bath on Wafer Toxic-Corrosive bench in Bay 4
- After a few days heated, it loses potency - must drain + replenish with fresh solution.
- ~30-90min will remove stubborn, microscopic PR residues from dry etching.
Gold Plating
To Be Added
Chemi-Mechanical Polishing (CMP)
To Be Added
Mechanical Polishing (Allied)
To Be Added