SEQUENTIAL MULTIPLE-LASER-ASSISTED POLISHING OF FREESTANDING CVD DIAMOND SUBSTRATES

Diamond, the best thermal conductor known, is the ultimate choice as a substrate material for the fabrication of denser, smaller and faster electronic packages. Consequently, in recent years, worldwide efforts have focused on the design of manufacturing transparent technologies f or post-synthesis processing (polishing, planarization, metallization, die attach, etc.) of diamond substrates. In this study, a manufacturi ng-transparent, cost-effective, non-vacuum, laser-assisted coarse poli shing technique for thick free-standing CVD diamond substrates was inv estigated [2]. The thickness of the substrates varied from 700 to 1000 mu m, with the average grain size ranging from 150 to 200 mu m. The a verage surface roughness (R-a) of the substrates, measured using conta ct surface profilometry, was between 20 and 30 mu m. The substrates we re initially irradiated with a Nd-YAG laser (lambda = 532 nm) for coar se material removal, followed by an ArF excimer laser (lambda = 193 nm ) for finer surface finishing. Under optimized conditions, the average surface roughness (R-a) was reduced from 25 to 5 mu m with the Nd-YAG laser, and further to less than or equal to 1 mu m with the excimer l aser. The technique, which is the fastest processing technique known t o the authors, is capable of polishing a 1 cm x 1 cm x 0.07 cm substra te in 50 s. (C) 1997 Elsevier Science S.A.