RBS study of the effect of arsenic and phosphorus interfacial segregation upon the sintering of contacts between implanted polycrystalline silicon and aluminum: Silicon(1%)

Abstract

The sintering behavior of the interface between Al: Si(1%) alloy and polycrystalline Si (poly-Si) was studied as a function of the poly-Si implantation dose by combining RBS, SEM, TEM and X-ray microanalysis. Two different N-dopants were used: arsenic and phosphorus. The dopants were implanted in the poly-Si layer and thermal annealing was used to obtain dopant segregation towards the poly-Si interfaces.After sintering, two main effects were detected: (1) AlSi eutectic phase precipitates and Si crystallites are formed at the interface. (2) The density of precipitates is a function of the implantation dose. For doses above 1 × 10 15 at./cm 2, segregated arsenic and phosphorus are found to completely inhibit this precipitation process, provided that the segregation peak of the dopant profile is preserved before metallization.Several conclusions can be drawn: for surface concentrations higher than 8 × 10 19 at./cm 3, arsenic and phosphorus inhibit the precipitation of the AlSi eutectic phase, and thus inhibit interactions between the films at the interface. Moreover, argon gas, used for sputtering deposition of aluminum, segregated at the poly-Si/Al: Si(1%) interface and may also inhibit the metal-semiconductor interdiffusion.