Metallurgical and electrical properties of chromium silicon interfaces

The effect of annealing treatment up to 500°C on CrSi contacts was studied from physico-chemical and electrical view points. The solid-solid reactions between a 1000 Å thick Cr layer and a 〈111〉N single crystal of silicon, were studied by the He⁺ ion backscattering method, X-ray diffraction and transmission electron microscopy. We first observed a growth in the Cr grains and then the nucleation and growth of the disilicide CrSi₂. For annealing temperatures greater than 415°C, the growth is linear in time with an activation energy of 1.5±0.1 eV and for lower temperatures it becomes superlinear. The growth mechanism is discussed in terms of growth limiting phenomena. The variations of the electrical parameters (ideality factor n and barrier height 0_Bn) as a function of 15 min anneals between 300 and 500°C were correlated to the physico chemical observations. We establish, firstly, an optimal temperature annealing range in order to obtain good Schottky CrSi diodes and, secondly, a low limit of Cr thickness which must be deposited to obtain acceptable Schottky CrSi₂  Si diodes after annealing.