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Doping and crystallographic effects in Cl-atom etching of silicon

1990; American Institute of Physics; Volume: 67; Issue: 6 Linguagem: Inglês

10.1063/1.345388

1520-8850

E. A. Ogryzlo, D. E. Ibbotson, Daniel Flamm, J. A. Mucha,

Thin-Film Transistor Technologies

Absolute rates for the intrinsic reaction between Cl atoms and surfaces of P-doped polycrystalline silicon, P-doped Si(100) and As, Sb-doped Si(111) substrates were measured for the first time as a function of dopant concentration (Ne) and substrate temperature in a downstream reaction system. This study clearly shows that when there is no ion bombardment, increasing Ne increases the Si-Cl reaction rate even when silicon is lightly doped (∼1015 cm−3), in contrast to in-discharge studies. Moreover, results showed that crystal orientation influences the Cl-Si reaction more than Ne, for Ne<1020 cm−3. The data are fitted to a modified Arrhenius expression, R=νNγenClT1/2e−E/kT, with R the etch rate and nCl the gas phase Cl concentration. The calculated values of the activation energy E are 4.1–4.7 kcal/mole for all doping levels and crystallographic orientations. Therefore, the doping effect is manifested solely in the preexponential (νNγe) of the Arrhenius expression, and the data qualitatively agree with a charge-transfer mechanism which facilitates chemisorption of chlorine.