4. (Thermal) Oxidation

Oxidation Rate: Crystal Orientation
(111)
(011)
(100)
• The parabolic rate depends on the D of oxidants through SiO 2 .
• On the other hand, the linear rate constant B/A depending on the reaction k S
at SiO 2 /Si interface is strongly related to the crystallographic orientation of Si.
• The growth rate ratio (v 111 /v 100 ) decreases at high temperatures and at long time
since the parabolic rate constant is predominant. (diffusion-limited)
Ø CO changes the # of Si bonds available at the surface
(100) silicon: the smallest number of unsatisfied Si bonds at the Si-SiO2
interface, and the choice of the (100) orientation yields the lowest number of
interface traps, leading to lowest oxidation rate.