Annealing effects in undoped and phosphorus doped low temperature oxide layers

Abstract

Properties of undoped and phosphorus doped low thermal oxides deposited by low pressure chemical vapour deposition and atmospheric chemical vapour deposition methods are compared. The evolution of stress after annealing treatments has been analysed with emphasis on its relationship with the local microscopic structure. Initial results indicate an apparent contradiction: whereas Fourier transform infrared spectroscopy indicates that the local structure of the layers expands and tends to relax as a function of annealing temperature, the macroscopic stress measured from wafer warpage suggests an increasing compressive stress after annealing. This behaviour is readily explained if the interfacial layer plays a major role, as the interface boundary condition of crystalline silicon becomes stronger on deposited oxides after annealing. Studies on bevelled samples have been carried out to support this hypothesis. The annealing behaviour of doped oxides has been found to be more complex as a consequence of phosphorus diffusion to the substrate; in addition, the stretching band of these oxides isfound to split into two separate bands.

MST/3338