Thermodynamic analysis of the growth of germanium-containing films from Ge(C2H5)4 + hydrogen mixtures

Low-pressure (1.33 and 13.3 Pa) chemical vapor deposition (CVD) of GeC _x from tetraethylger-manium + hydrogen mixtures has been analyzed in a wide range of deposition temperatures, 300–1300 K, using thermodynamic modeling. In low-pressure CVD processes, films can be contaminated with impurities, in particular with oxygen, which may originate in the system in question from the residual air pressure in the reactor. Modeling results for the Ge-C-H and Ge-C-H-O-N systems indicate that the presence of oxygen adds significant complexity to the composition of condensed phases. At sufficiently high temperatures (T > 550 K), one can obtain GeC _x films essentially free from oxygen impurities. We have identified deposition conditions (T > 650 K) under which the overall composition of the GeC _x carbon-containing germanium layers remains constant. Experimental data are presented on the growth of germanium-containing films from a gas mixture with GeEt₄: H₂ = 1: 10 in the temperature range 573–823 K by plasma-enhanced CVD. At high deposition temperatures (T > 700 K), the composition of the films was near GeC _x , in agreement with thermodynamic analysis results.