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Wet etchants for silicon and silicon compounds

Mumbai University > Electronics Engineering > Sem 8 > MEMS Technology

Marks: 3M

1 Answer
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  • HNA for isotropic etching at room temperature.
  • Alkaline chemicals with ph> 12 for anisotropic etching.
  • Popular anisotropic etchants are:

    KOH (potassium hydroxide)

    EDP (Ethylene-diamine and pyrocatecol)

    TMAH (Tetramethy ammonium hydroxide)

    Hydrazine

  • Most etchants are used with 1 : 1 by weight mixture with water.
  • Typical etching rates are:
Materials Etchants Etch Rates
Silicon in<100>
Silicon in <100>
KOH
EDP
0.25 – 1.4 µm/min
0.75 µm/min
Silicon dioxide
Silicon dioxide
KOH
EDP
40 -80 nm / hr
12 nm/hr
Silicon nitride
Silicon nitride
KOH
EDP
5 nm/hr
6 nm/hr
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