Material to be Etched

Chemicals

Ratio

Comments

Silicon (Si)

HF : HNO₃ : Water

2:2:1

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Silicon (Si)

HNO₃: HF : Acetic Acid

5:3:3

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Silicon (Si)

NaOH in Water

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for dissolving the die from the package to allow inspection of eutectic die attach;

16 hours @ a temperature near boiling point

Silicon dioxide (SiO₂)-

thermally grown

NH₄F:HF

6:1

Buffered HF;

120 nm/min @ 25 C

Silicon dioxide (SiO₂)-

thermally grown

HF : Water

1:10

slower etch;

30 nm/min @ 25 C

Silicon dioxide (SiO₂)-

thermally grown

HF : Water

1:100

very slow etch;

1.8 nm/min @ 25 C

Silicon dioxide (SiO₂)-

thermally grown

HF

---

very rapid etch;

1.8 microns/min @ 25 C

Silicon dioxide (SiO₂)-

CVD

HF : Water

1:10

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Silicon dioxide (SiO₂)-

Phosphorus-doped

HF : Water

1:10

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Silicon nitride (Si₃N₄)

refluxing phosphoric acid

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use at 180C;

6.5 nm/min @ 25 C;

will also etch Al rapidly; plasma etching is preferred for removing Si₃N₄

Silver (Ag)

NH₄OH : H₂O₂

1:1

rapid etch

Silver (Ag)

HNO₃ : Water

1:1

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Tantalum (Ta)

HF : HNO₃ : Water

2:2:5

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Tin (Sn)

HF : HNO₃

1:1

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Tin (Sn)

H₂SO₄

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use at 80 C

Titanium (Ti)

HF : H₂SO₄ : Water

1:30:69

use at 70 C

Titanium-Tungsten (TiW)

H₂O₂

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very selective;

5 nm/min @ 25 C

Tungsten (W)

HF : HNO₃

1:1

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Vanadium (Va)

HF : HNO₃ : Water

1:1:1

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