Si-TiO2 interface evolution at prolonged annealing in low vacuum or N2O ambient

Titanium dioxide layers were obtained by the low-pressure chemical vapour deposition (LPCVD) method from a TiCl4, H-2 and N2O mixture at 630 degrees C and had rutile modification. The dielectric constant of the titanium dioxide is high, approximately 110, and the breakdown electric field strength more than 1 MV/cm. The fixed charge for the Si-TiO2 structures is negative and has a value in the order of 5 X 10(-8) C cm(-2) and the interface state density of these structures is 6 x 10(10) eV(-1) cm(-2). After annealing in oxidizing ambient, the dielectric constant is found to fall off, and the interface density of states of the Si-TiO2 structures is increased. It is proposed that this is connected with the Si-TiO2 interface evolution by the formation of a superthin silicon dioxide layer. (C) 2000 Elsevier Science B.V. All rights reserved.