Lattice buffer effect of Ti film on the epitaxial growth of Ag nanotwins on Si substrates with various orientations

Abstract

Titanium thin film has been commonly used in the semiconductor industry as an adhesive layer to enhance the bonding strength between a metallic film and Si substrate. Depositing a Ti interlayer to alleviate the lattice mismatch for the epitaxial growth of nanotwinned Ag films on Si substrates with (100), (110) and (111) orientations by magnetron sputtering process provides an additional advantageous effect. The experimental results indicated that the deposited Ag films, consisting of columnar grains with a high density of nanotwins, grew normal to the Si substrates. The twin boundaries showed a strongly preferential orientation of (111), and the twin spacing ranged from 2 to 50 nm, with an average value of about 12 nm. Ag (111) nanotwins grew much better on Si (100) substrate than on Si (110) and Si (111) with Ti pre-coating, leading to the sputtered Ag nanotwinned film on Si (100) having the highest indentation hardness among the three combinations.