Influence of the growth conditions on the composition of Al nitride films by laser ablation

We have studied the growth of Al nitride films by laser ablation in order t o check the potential of the method. The influence of process parameters su ch as nature of the tal-get, laser energy density, nitrogen partial pressur e, etc, on the composition, chemical nature and structure of the films has been investigated. Rutherford backscattering spectrometry, nuclear reaction analysis, X-ray diffraction and X-ray photoelectron spectroscopy were used to characterize the films. Literature reports on AIN film growth by laser ablation but oxygen contamination is poorly discussed whereas it is the mai n problem encountered. The origin of this contamination and the mechanisms of incorporation were studied, and the crucial parameter was found to be th e residual pressure during ablation. Due to the difference in chemical reac tivity between oxygen and nitrogen atomic species, to obtain pure AIN films it is necessary to increase the concentration of atomic nitrogen. Thus, a RF discharge device was added allowing a better nitrogen molecule dissociat ion. Finally, despite composition deviations, the AIN phase can be formed i n the laser-deposited films. Highly textured films presenting; epitaxial re lationships with crystalline Al2O3 substrates can be grown even with a 10% oxygen concentration.