MONOLITHIC MATERIAL FABRICATION BY CHEMICAL VAPOR-DEPOSITION

The subatmospheric pressure chemical vapor deposition (CVD) process has been used to fabricate theoretically dense, highly pure, void free and large area infrared-optical and ceramic materials such as ZnS, ZnSe, CdS, CdZnTe, Si and SiC. In this paper, an overview of a large scale CVD process is presented emphasizing the important technical and engineering issues such as control of material properties, injector heating and its effect on growth, selection of an appropriate mandrel material, grain growth, material bowing, nodular growth, and storage, transport and scrubbing of a large quantity of hazardous chemicals. Further, the flow pattern in CVD reactors is described and its importance in achieving good control over thickness and composition uniformity over large areas is discussed.