REACTIVE ION ETCHING OF DIAMOND AS A MEANS OF ENHANCING CHEMICALLY-ASSISTED MECHANICAL POLISHING EFFICIENCY

Diamond. due to its unique combination of excellent thermal. electrica l and mechanical properties, is a candidate material for MCM thermal m anagement. However, because of inherent limitations in its growth, som e degree of post-deposition surface finishing is usually required. Thi s paper describes the results of reactive ion etching (RIE) of polycry stalline diamond films in an oxygen plasma. The etching procedure was characterized in terms of etch rate and impact on the surface morpholo gy of the diamond and its potential as a pretreatment for the chemical ly-assisted mechanical polishing (CAMP) of diamond films. Diamond film s deposited by both DC arcjet chemical vapor deposition (CVD) and micr owave plasma CVD (MPCVD) were used in this work. The etch rate is show n to increase with increasing RF power, chamber pressure and a restric ted range of oxygen flow rate. At low pressures, etching occurs primar ily in the grain boundary regions, whereas, at high pressures, microch annels are formed near the tips of individual crystallites. Etching at low powers produces uniform surface pitting and columnar structures o ver the entire surface. Etching also causes all films to darken in col or. The degree of darkening increases with increasing etch rate and et ch time. Etch rates are in the range of 50-100 nm/min for the DC arcje t films and 50-60 nm/min for the MPCVD films. Etching reduced the aver age surface roughness by approximately 50%. (C) 1997 Elsevier Science S.A.