Chemistry Reference
In-Depth Information
8.3.3. Pore Orientation and Shape
The growth of individual pores, or the dissolution at pore tips, is anisotropic and thus
depends on the orientation of the substrate. It is also determined by direction of the
carrier source; pores tend to grow toward the carrier source. The relative effect of sub-
strate orientation and direction of the carrier source on the orientation of pores is deter-
mined by the specific electrochemical reactions at the silicon/electrolyte interface at the
pore bottoms under a given set of formation conditions.
The orientation of primary pores is in general in the <100> direction for all of the
PS formed on (100) substrate.
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For PS with the dendritic structure shown in Fig.
8.32, pores propagate along the (100) direction even on(110)and(111)substrates.
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