Pseudoline electron beam recrystallization of silicon-on-insulator

A pseudoline electron beam (e-beam) which is produced by scanning a spot e-beam along a line faster than the thermal response time of the substrate, has an advantage for recrystallization of silicon-on-insulator (SOI) structures in that the temperature profile along the line can be precisely controlled by the waveform of the scanning signal. In this paper, the current status of the pseudoline e-beam recrystallization method is reviewed, being focused on two essential problems: void generation and subboundary generation in the recrystallized films. First, in order to predict the temperature distribution during heating, the heat equation is solved for both static and dynamic cases using the Kirchhoff transformation and the Green function analysis, respectively. Then, generation mechanisms of voids and subboundaries are experimentally studied and the respective generation models are set up. It is concluded that voids are generated from isolated molten spots in the SOI film and a perforation seed structure in which rectangular seed regions are separately arranged along a line, is effective to suppress them. It is also concluded that subboundaries are generated at the interior corners of the folded 11facets which are formed at the solid-liquid interface. Other topics included in this paper are oblique scanning of the pseudoline e-beam, optimization of the scanning direction and scanning waveform, optimization of the seed direction, generation of twin defects, relation between the subboundary direction and the scanning velocity of the beam, and so on. As a result, a single-crystal SOI area of 100 μm square has been obtained.