Chemistry Reference
In-Depth Information
In dry oxidation the first reaction dominates whereas the second reaction dominates in
wet oxidation. The growth rate is a function of temperature, oxide thickness, and sub-
strate orientation. As an example, the average growth rate on the (100) surface in wet
oxygen at 1000 °C after 1h of oxidation is about 1 Å/s. The structure of thermally grown
oxide is amorphous and typically has exact stoichiometric composition. The oxide layer
formed on a silicon substrate is about 2.27 times the thickness of the consumed silicon
and contains about 2.2 × 10
22
of
3.2.2. Chemical Vapor Deposition
Silicon oxide films can be deposited by the pyrolytic oxidation of a silane or
alkoxysilane in a chemical vapor deposition (CVD) system.
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In a process using silane
as the reactant, the reaction proceeds as follows:
Typically, this reaction is carried out at atmospheric pressure in a cold-wall CVD
system. The growth rate by the silane process is rather high, usually 8-17 Å/s.
3.2.3. Liquid-Phase Deposition
Liquid-phase deposition (LPD) of is a relatively new process.
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The
growth of the oxide is typically conducted in supersaturated hydrofluosilic acid
solution and results from the overall reaction between
and water:
According to this reaction, may be formed if the concentration of or
water is increased, or the concentration of HF is reduced. Experimentally, three
processes have been developed based on the above reaction to form
deposit simply
by adding either boric acid
0.01-0.07 Å/s depending on solution composition, is very low relative to that of thermal
or Al, or water to the solution. The deposition rate,
oxide.
3.2.4. Native Oxide and Anodic Oxide
The thin oxide film, usually no more than 1 or 2nm in thickness, which sponta-
neously forms in the air and in water, is referred to as native oxide. Native oxide of a
certain form and thickness exists essentially on all silicon surfaces due to the abun-
dance of air and water and the inevitable encounters with them during the production
and processing of silicon material and devices. Thicker oxides, up to
in thickness,
