AVS 45th International Symposium
    Electronic Materials and Processing Division Thursday Sessions
       Session EM1-ThA

Paper EM1-ThA10
Thermal Stability of a-SiNx:H Films Deposited by Plasma Electron Cyclotron Resonance

Thursday, November 5, 1998, 5:00 pm, Room 314/315

Session: Dielectrics
Presenter: A. del Prado, Universidad Complutense de Madrid, Spain
Authors: F.L. Martinez, Universidad Complutense de Madrid, Spain
A. del Prado, Universidad Complutense de Madrid, Spain
D. Bravo, Universidad Autonoma de Madrid, Spain
F.J. Lopez, Universidad Autonoma de Madrid, Spain
I. Martil, Universidad Complutense de Madrid, Spain
G. Gonzalez-Diaz, Universidad Complutense de Madrid, Spain
Correspondent: Click to Email
Amorphous hydrogenated silicon nitride is widely used in semiconductor devices. Its higher dielectric constant compared to silicon dioxide results in a larger gate insulator capacitance, which in its turn means a larger transconductance and a smaller threshold voltage shift for a given defect charge concentration. A Rapid Thermal Annealing (RTA) post-treatment can improve significantly the properties of the dielectric and the interface. We have analyzed the influence of RTA on Al/SiN@sub x@:H/Si structures with x=1.55. The silicon nitride is deposited by the Electron Cyclotron Resonance plasma method and the films were annealed at temperatures ranging from 300ºC to 1050ºC. Determination of the dangling bond density in the insulator was done with Electron Paramagnetic Resonance, while the density of interface states was obtained from the high-low frequency capacitance method. Resistivity and breakdown field were deduced from current measurements in accumulation. A pronounced dip in the density of dangling bonds is obtained for moderate annealing temperatures, from 1.85E18 cm@super -3@ for the as-deposited film down to 9.58E16 cm@super -3@ at the point of inversion of the trend between 500 and 600ºC. The density of interface states is also reduced in this range of temperatures from 3.6E11 eV@super -1@cm@super -2@ to 1.2E11 eV@super -1@cm@super -2@. Resistivity and breakdown field are maintained in the range 5E14-5E15 @OMEGA@cm and 6.4-6.6 MV/cm respectively up to a temperature of 600ºC. We attribute the improvement of the film properties and interface characteristics to a thermal relaxation and reconstruction of the silicon nitride lattice and its interface with the silicon substrate. In this range of temperatures we did not observe hydrogen evolution from the SiN@sub x@:H lattice. For temperatures above this threshold the electrical properties suddenly deteriorate and the density of dangling bonds increase. At even higher temperatures (above 800ºC) a release of hydrogen from N-H bonds takes place.