Wet Etching Recipes

See the Master Wet Etching Table at the bottom of this page for wet-etch rates in various experiments we have tested.

Chemicals Available

• The Chemical Lists show stocked chemicals, photolithography chemicals, and how to bring new chemicals.

References

1. Etch rates for Micromachining Processing (IEEE Jnl. MEMS, 1996) - includes tables of etch rates of numerous metals vs. various wet and dry etchants.
2. Etch rates for micromachining-Part II (IEEE Jnl. MEMS, 2003) - expanded tables containing resists, dielectrics, metals and semiconductors vs. many wet etch chemicals.
3. Guide to references on III±V semiconductor chemical etching - exhaustive list of wet etchants for etching various semiconductors, including selective etches.
4. Transene's Chemical Compatibility Chart provides a useful quick-reference for which Transene etchants attack which materials.
   1. 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

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	HCl:H3PO4(1:3)	~1000	Highly	InGaAs	High	Lamponi (p.102)	Example	Jon Doe	Example
InP	HCl:H3PO4(1:3)	~1000	Highly	InGaAsP	High	Lamponi (p.102)	Example	Jon Doe	Example
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

The Master Table of Wet Etching (Include All Materials)

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	HCl:H3PO4 (1:3)	~1000	Highly	InGaAs	High	Lamponi (p.102)		Jon Doe
InP	HCl:H3PO4 (1:3)	~1000	Highly	InGaAsP	High	Lamponi (p.102)		Jon Doe
InP	H3PO4:HCl (3:1)	~1000	Highly	InGaAs	High	Lamponi (p.102)		Jon Doe
InP	H3PO4:HCl (3:1)	~1000	Highly	InGaAsP	High	Lamponi (p.102)		Jon Doe
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