High pressure high power microwave plasma chemical vapor deposition of large area diamond films

Uniform, large area, smooth, and chemically clean diamond films having low residual stress are important for many applications such as electronic packaging, metallurgical and optical coatings, and X-ray lithography masks. Uniform diamond films were deposited on 75 mm diameter p-type (100) silicon substrates using a Wavemat Inc. microwave plasma disc reactor (MPDR) which was modified for high pressure and high power operations. These high pressure high power deposited films yielded much better quality even though the deposition rate increased by more than 50% when compared to films deposited under low pressures and powers. A dry abrasive seeding technique was used that was simple but offered very high nucleation density. The CH4 concentration was varied over 0.5-3.0% and the deposition pressure and power were set at 67 Torr and 3500 W, respectively. Deposited films were characterized by SEM, AFM, Raman, and X-ray diffraction (XRD) techniques. For increasing CH4 flow from 0.5 to 3%, the deposition rate increased by four times without much reduction in the film quality, as observed by Raman spectroscopy. For CH4 flow rate of up to 2%, the film texture was (111) whereas it changed to [220] for films deposited at 3% CH4. The macro-and micro-stress in the films were measured by XRD d-sin(2) psi technique and diffraction peak broadening, respectively. All the deposited films showed moderate compressive macro-stress; the micro-stress values for these samples were much less than observed for films deposited in low-pressure low power regime. (C) 1997 Elsevier Science S.A.