EXCIMER-LASER PHOTOFRAGMENTATION OF BORON-TRICHLORIDE AND ITS IMPLICATIONS FOR LASER VAPOR-DEPOSITION AND DOPING PROCESSES

The photolysis of BCl3 at the excimer-laser wavelengths of 193 and 248 nm has been investigated by mass spectroscopic and fluorescence techniques. At 193 nm, the BCl (A(1)II), excited B(B*) and BClx+ (x=0,...,3) species are detected, whereas at 248 nm, BCI (A(1)II), B*, Cl-2 (2(3)II(g)) and BClx+ (x = 1,2) are detected. The pressure and fluence dependences of the signals are determined. At 193 nm, BCI, is proposed to undergo one- and two-photon excitations, the former resulting in BCl2 and the latter in BCl (A(1)II) and BClx+ (x = 3,2). In the case of the 248 nm excitation, the observed emitting species are shown to derive from secondary reactions that take place following two-photon photoexcitation/fragmentation of BCl3. Implications of the observations herein for the vapour and doping processing by laser of BCl3 are discussed. In particular, for processing at 248 nm, the observed photoinduced reactivity may be significant and should be considered in addition to any pyrolytic mechanism.