HF dip [HFDIP]
Setup time for this process is about 5 minutes. This process takes about 5 minutes to
complete.
Hydrofluoric acid (HF) is used to remove native silicon dioxide from wafers. Since it
acts quickly, one needs to only expose the wafer fro a short time (“dip”). HF is a
dangerous chemical and protective gear must be worn when using it, in particular,
neoprene or thick nitrile gloves and eye protection must be worn.
A prepared solution should already be available to you. If not, here is how to prepare a
2% solution.
480 ml water
20 ml HF (49%)
Wear heavy protective gloves and protective eye gear. Add 480 ml water to
polyproplene beaker then, add 20 ml HF. Never use a glass beaker with HF since HF
attacks glass. Label the bottle “2% HF solution-Dangerous acid!” then, add your name
and the date.
Soak the wafer for 2 minutes in this solution. Remove the wafer and rinse in running DI
water. Check for hydrophobicity by performing a wetting test. Pour a little DI water on
the surface. If the water beads up and rolls off, the surface is hydrophobic and water will
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