Temperature effects on the electrical properties and structure of interfacial and bulk defects in Al/SiNx : H/Si devices

Bulk properties of SiNx:H thin film dielectrics and interface characteristi cs of SiNx:H/Si devices are studied by a combination of electrical measurem ents (capacitance-voltage and current-voltage characteristics) and defect s pectroscopy (electron spin resonance). The SiNx:H films were deposited by a n electron cyclotron resonance plasma method and subjected to rapid thermal annealing postdeposition treatments at temperatures between 300 and 1050 d egreesC for 30 s. It is found that the response of the dielectric to the th ermal treatments is strongly affected by its nitrogen to silicon ratio (N/S i=x) being above or below the percolation threshold of the Si-Si bonds in t he SiNx:H lattice, and by the amount and distribution of the hydrogen conte nt. The density of Si dangling bond defects decreases at moderate annealing temperatures (below 600 degreesC) in one order of magnitude for the compos itions above the percolation threshold (nitrogen rich, x=1.55, and near sto ichiometric, x=1.43). For the nitrogen rich films, a good correlation exist s between the Si dangling bond density and the interface trap density, obta ined from the capacitance measurements. This suggests that the observed beh avior is mainly determined by the removal of states from the band tails ass ociated to Si-Si weak bonds, because of the thermal relaxation of the bondi ng strain. At higher annealing temperatures the deterioration of the electr ical properties and the increase of the Si dangling bonds seem to be associ ated with a release of trapped hydrogen from microvoids of the structure. F or the silicon rich samples rigidity percolates in the network resulting in a rigid and strained structure for which the degradation phenomena starts at lower temperatures than for the other two types of samples. (C) 2001 Ame rican Institute of Physics.