DIFFUSION OF GOLD INTO POLYCRYSTALLINE SILICON INVESTIGATED BY MEANS OF THE RADIOTRACER AU-195

Gold diffusion experiments were performed in three types of polycrysta lline silicon over the temperature range 551-1265 degrees C by using t he radiotracer Au-195, and the serial sectioning technique. Depending on temperature, material structure, and diffusion time, different type s of profiles were obtained, some of them being noninterpretable withi n the framework of classical solutions of Fick's equations in the pres ence of, grain boundaries. In contrast, all these experimental profile s were successfully analyzed by using a new diffusion model applicable to host material/impurity systems revealing strong segregation effect s and a negligible diffusion flux along the extended defects. At tempe ratures higher than about 1100 degrees C, effective diffusion coeffici ents slightly lower than true lattice diffusion coefficients previousl y reported in the literature were measured. Decreasing the temperature ,the effective Au diffusivity depends on the structure of the samples, which leads to different Arrhenius plots exhibiting a downward curvat ure. A gold segregation enthalpy of about 141 kJ mol(-1) was estimated from the observed diffusion behavior. (C) 1996 American Institute of Physics.