Use of a capacitance voltage technique to study copper drift diffusion in (porous) inorganic low-k materials

Cu super(+) drift diffusion in two inorganic low-k materials is evaluated. The diffusion is investigated by measuring shifts in the flatband voltage of capacitance/voltage measurements on Cu gate capacitors after bias temperature stressing. The Cu super(+) drift rate in SiO sub(x)C sub(y) (2.7 less than or equal to k less than or equal to 3.1) is considerably lower than in PECVD oxide. This electrical method is not suited for a porous silicon resin (k approximately 2.0) because of the occurrence of instabilities in the metal/dielectric. A modification of the measurement technique is required. The modification consists of measuring the Cu super(+) ions, which have been diffused through the porous dielectric in an underlying thermal oxide layer. The Cu super(+) drift mobility in the porous dielectric as measured by this method appears to be lower than in thermal oxide. copyright 2002 Elsevier Science B.V. All rights reserved.