Doping and strain effects on the microstructure of erbium silicide on Si:P

In pursuit of a potential low-resistive contact structure, ErSi2-x was grown on an excessively P-doped and highly strained epitaxial Si layer (Si:P with a P concentration of ∼2.8 at%), and its microstructure was investigated in comparison to that grown on a conventional Si(001) substrate. On the Si substrate, ErSi2-x grains nucleated with a local epitaxial relationship and grew to form a polycrystalline film with a preferred alignment of ErSi2-x(101¯0)//Si(001) in a largely strained state. However, the epitaxial relationship at the interface during the ErSi2-x nucleation stage was disrupted, and randomly oriented columnar ErSi2-x grains grew on the Si:P(001) layer. Several experiments to separate the possible strain and doping effects showed that inhibition of the epitaxial nucleation of ErSi2-x grains was induced by excessive P accumulation at the interface region rather than by the strain effect. P enrichment at the interface encouraged ErSi2-x film growth without a preferred orientation, and the intermittent P-deficient areas worsened the interface roughness by provoking the local intrusion of ErSi2-x grains toward the Si:P layer.