Crystallization of Si in Millisecond Time Domain Induced by Thermal Plasma Jet Irradiation

Abstract

Investigations on the temperature profiles and formation of crystalline Si in rapid thermal annealing induced by thermal plasma jet (TPJ) irradiation have been reviewed. Substrate surface temperature during annealing has been measured by an optical probe method which has an accuracy of 30 K and a time resolution of millisecond. By changing the annealing conditions such as scan speed (v), plasma–substrate gap (d) and Ar gas flow rate ( f), maximum surface temperature (Tmax) is controlled in the ranges of 960 to 1860 K with a typical annealing duration (ta) of ∼3 ms. On the basis of temperature measurement and in-situ reflectivity measurement techniques, the phase transformation of amorphous Si (a-Si) films has been investigated. When the a-Si films are heated to a temperature higher than the melting point, solid phase crystallization (SPC) followed by melting and resolidification of the films have been observed. It was found that SPC temperature increased from 1096 to 1284 K with decreasing crystallization time from 1.4 to 0.12 ms. Thin-film transistors (TFTs) fabricated using the SPC films show good electrical characteristics with an average field effect mobility of 61 cm2 ·V-1 ·s-1 and a threshold voltage of 3.4 V. By annealing SiOx films at temperatures higher than 1430 K using a TPJ, the precipitation of nanocrystalline Si with a size ranging from 10 to 250 nm has been observed.