Thermodynamic Analysis of the Chemical Vapor Deposition of Phosphorus Nitride (P3N5) Thin Films

Thermodynamic analysis of the chemical vapor deposition (CVD) of P 3 N 5 has been performed using the method of the minimization of the Gibbs' free energy in order to evaluate the PH 3 -NH 3 -N 2 , PCl 3 -NH 3 -H 2 and PBr 3 -NH 3 -H 2 gaseous mixtures for their potential to synthesize single-phase P 3 N 5 films at high yields. The conditions for the deposition of P 3 N 5 have been determined as a function of input reactant gas ratio of PX 3 /(PX 3 +NH 3 ) (X=H or Cl or Br) and deposition temperature at atmospheric pressure. A single phase P 3 N 5 is deposited at almost all reactant ratios and at temperatures below about 700 K when the PH 3 -NH 3 -N 2 system is used. The use of halide gas mixtures limits the formation of single phase P 3 N 5 to narrow regions of temperature and input reactant gas ratio. The gaseous species generally present in greatest abundance are H 2 , N 2 , NH 3 , PH 3 , HCl, P 4 , PCl 3 , P 2 , HBr, PBr 3 and PN. The thermodynamic analysis suggests that among the systems investigated here, the PH 3 -NH 3 -N 2 mixture is the most promising because simultaneously it gives the highest P 3 N 5 deposition yield and allows better control of the CVD process for the synthesis of P 3 N 5 films.