PRECURSOR OXIDATION-STATE CONTROL OF FILM STOICHIOMETRY IN THE METAL-ORGANIC CHEMICAL-VAPOR-DEPOSITION OF TIN OXIDE THIN-FILMS

A new tin(IV) hexafluoroisopropoxide complex and a related tin(II) com pound were used as low-pressure chemical vapor deposition precursors t o tin oxide thin films. The films were characterized by backscattering and elastic recoil spectrometries, Auger and UV-vis spectroscopies, a nd nuclear reaction analysis. Sn(OCH(CF3)(2))(4)(HNMe(2))(2), a volati le solid (subl 70-75 degrees C at 0.06 Torr), was synthesized in high yield by reacting Sn(NMe(2))(4) with (CF3)(2)-CHOH. A crystal structur e determination shows that it has an octahedral structure with trans-a mine ligands. Low-pressure chemical vapor deposition using Sn(OCH(CF3) (2))(4)(HNMe(2))(2) and air as precursors gave fluorine-doped tin oxid e films (O/Sn = 1.8-2.4; F/Sn = 0.005-0.026) at substrate temperatures of 200-450 degrees C. The films are highly transparent in the visible region (>85%) and have resistivities as low as 2.1 x 10(-3) Omega cm. In contrast to the results obtained for the tin(IV) precursor, the ti n(II) compound Sn(OCH(CF3)(2))(2)(HNMe(2)) in combination with air or water vapor gave nonconductive transparent films at substrate temperat ures of 180-250 degrees C having composition SnO0.9-1.3F0.1-0.4. These film stoichiometries suggest that hydrolysis was the primary film-for ming reaction and that the tin was not oxidized in the deposition proc ess.