SIMULATION OF MORPHOLOGICAL INSTABILITIES DURING DIAMOND CHEMICAL-VAPOR-DEPOSITION

The diamond chemical vapor deposition (CVD) process has been investiga ted theoretically and the morphological instabilities associated with the growth of diamond films have been examined with a model based on t he continuum species conservation equation coupled to surface reaction kinetics. A linear stability analysis and numerical calculations have been carried out to determine critical parameters affecting the diamo nd deposition layer morphology. A two-dimensional model describes the evolution of the gas-solid interface. The dynamic behavior of the inte rface depends on the reactants' diffusivity and surface kinetics. Thes e factors depend upon the reactant material properties and him growth conditions such as the reactor temperature and pressure. From the anal yses, it has been found that the ratio (D/k) of gas phase diffusivity (D) to the surface reaction rate constant (k) plays the critical role in promoting diamond morphological instabilities because the film morp hology stabilizing processes of surface diffusion and re-evaporation a re absent or negligible during diamond CVD. It is found that the film nonuniformity increases as the ratio (D/k) decreases. Increasing growt h rates also result in increasing morphological instability, leading t o rough surfaces. It is shown that increasing reactor pressure and dec reasing gas-phase temperature and/or substrate temperature promote dep osition layer nonuniformity. An approach to avoiding these instabiliti es is proposed. (C) 1997 Elsevier Science S.A.