Simple Method for the Calculation and Use of CVD Phase Diagrams with Applications to the Ti-B-Cl-H System, 1200 to 800 exp 0 K

摘要

A simple method for calculating multi-component gas-solid equilibrium phase diagrams for chemical vapor deposition (CVD) systems is presented. The method proceeds in three steps: dtermination of stable solid assemblages, evaluation of gas-solid stability relations, and calcuation of conventional phase diagrams using a new free energy minimization technique. The phase diagrams can be used to determine (1) bulk compositions and phase fields accessible by CVD techniques; (2) expected condensed phases for various starting gas mixtures; and (3) maximum equilibrium yields for specific CVD process variables. The three step thermodynamic method is used to calcuate phase diagrams for the example CVD system Ti-B-Cl-H at 1200 and 800 exp 0 K. Examples of applications of the diagrams for yield optimization and experimental accessibility studies are presented and discussed. Experimental verification of the TiB sub 2 + Gas/Gas phase field boundary at 1200 exp 0 K, H/Cl = 1 confirms the calculated boundary and indicates that equilibrium is nearly and rapidly approached under laboratory conditions. (ERA citation 05:026201)