USE OF OXYGEN GAS IN DIAMOND FILM GROWTH FOR IMPROVING STRESS AND CRYSTALLINITY PROPERTIES OF AN X-RAY MASK

In order to improve the properties, such as stress and crystallinity, of diamond films for use as x-ray masks, we have studied the effective ness of the addition of O-2 to a CH4/H-2 gaseous mixture in magnetical ly enhanced microwave plasma chemical vapor deposition. As the O-2 con centration was increased, diamond grain growth became more dominant ov er the nondiamond component and grain growth continued. As a result, s tress shifted toward the tensile regime. We explain the mechanism of t his diamond stress shift by using the stress generation model proposed by Chaudhari. Under the optimum deposition conditions, i.e., CH4/O-2 /H-2 = 2.0/0.5/97.5 vol % at 920 degrees C, we obtained (Ill)-textured polycrystalline diamond, which had high crystallinity and improved st ress properties. The average stress was 147 MPa (tensile) and the unif ormity was less than or equal to +21.1%; - 12.2% was achieved within a 50-mm-diam are,for a 2.3-mu m-thick film. The biaxial Young's modulus was evaluated by the bulge test, and was found to be 1000+/-51 GPa. T his diamond membrane caused little in-plane distortion-induced backetc hing, i.e., max (x,y) = (27,31) nm, due to its high biaxial Young's mo dulus. (C) 1998 American Vacuum Society.