Laser reactive ablation of thin nitride films

Abstract

Lasers provide appropriate approaches for the synthesis of materials of interest in modern technology. Laser chemical vapour deposition [ l ] and synthesis of compounds under direct laser i~radiation [2] are among the most successful methods. Also, congruent ablation deposition of compounds (mainly high critical temperature superconductors, but also titanium nitride) was successfully investigated [3, 4 3 . A different approach is now emerging [5]: laser reactive ablation (LRA) deposition of thin films. In the LRA deposition method a solid support collects the material ablated by the laser irradiation of the target and reacted with a low-pressure ambient gas. We deposited titanium and silicon nitride films on silicon wafers at room temperature and at moderate temperature (<300 C) by LRA. Traditional techniques (chemical vapour deposition, reactive evaporation, sputtering) require high-temperature thermal treatments for nitride synthesis, with the consequence of long-range diffusion of dopants and impurities into the substrate. Moreover, this method has the advantage of single-step synthesis and deposition of thin films.