Excimer laser recrystallization of amorphous Si films characterized by grazing X-ray diffraction and optical reflectivity

Abstract

The crystallization of amorphous silicon films with an Ar-F excimer laser pulse (λ = 193 nm, τ = 20 ns) was studied by grazing X-ray diffraction and optical reflectivity measurements performed with a Beckman spectrophotometer. The influence of the Si deposition technique on the crystallization process has been investigated: the initial amorphous Si films were deposited by sputtering or by chemical vapour deposition on amorphous substrates. The laser energy threshold Et for the crystallization is deduced from these experiments. For the films deposited by CVD, the found value of 85 mJ/cm2 is in good agreement with the calculated threshold energy for melting of amorphous silicon. Additional information was deduced from X-ray diffraction: a preferential 〈111〉 growth direction of the grains in the crystallized layer and differences between the dynamics of crystallization in relation with the deposition process were noted.