Online proceedings - EDA Publishing Association

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11-13 May 2011, Aix-en-Provence, France
5700 Å. The etch rates were used as a reference for both the
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standard process and the comparable processes developed later
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for the ethanol catalyst. After each etching run, the oxide and
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nitride chips were placed on a hot plate for 30 seconds at
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200! to remove any residue that can be formed on a silicon
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nitride surface during HF etching as described in [2].
A. PECVD Oxide and Nitride with Water Catalyst:
At 25!, a low pressure of 8 Torr was used and for a high
pressure process, 11T was satisfactory. This was the standard
“base” recipe of 150 sccm aHF, with the remaining gas flow
from the nitrogen buffer and catalyst flows dependant on the
flow of the carrier gas. That is: 25 sccm and 175 sccm, 50 sccm
and 150 sccm and 75 sccm and 125 sccm respectively for the
carrier gas and nitrogen buffer gas flows. For etching at 10!,
a low pressure of 3.5 Torr and a high pressure of 4.5 Torr were
used. The gas flow of the carrier gas was again varied to study
the behaviour of the catalysts.
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Fig. 6. Showing the etch variance between a 2 minute and 3 minute etch of
Silicon Oxide to Silicon Nitride in a 10! etch regime at high and low
pressures as a function of water catalyst carrier gas flow.
B. PECVD Oxide and Nitride with Ethanol Catalyst:
A direct comparison of the etch of silicon nitride and oxide
could be conducted using the same gas flows as the water
catalyst tests. At 25!, a high pressure of 11 Torr was used and
a low pressure of 8 Torr was used. At 10!, the high and low
pressures were 4.5 Torr and 3.5 Torr respectively.
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Fig. 3. Selectivity of Silicon Oxide to Silicon Nitride in a 25! etch regime
at high and low pressures as a function of water catalyst carrier gas flow.
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849:"
-./001./"
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Fig. 4. Showing the etch variance between a 2 minute and 3 minute etch of
Silicon Oxide to Silicon Nitride in a 25! etch regime at high and low
pressures as a function of water catalyst carrier gas flow.
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Fig. 5. Selectivity of Silicon Oxide to Silicon Nitride in a 10! etch regime
at high and low pressures as a function of water catalyst carrier gas flow.
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Fig. 7. Selectivity of Silicon Oxide to Silicon Nitride in a 25! etch regime
at high and low pressures as a function of ethanol catalyst carrier gas flow.
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849:$
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Fig. 8. Showing the etch variance between a 2 minute and 3 minute etch of
Silicon Oxide to Silicon Nitride in a 25! etch regime at high and low
pressures as a function of ethanol catalyst carrier gas flow.
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+,--'"-*.,/*0#12*3/$$45*
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2345$-./001./$
Fig. 9. Selectivity of Silicon Oxide to Silicon Nitride in a 10! etch regime
at high and low pressures as a function of the catalyst carrier gas flow.
37