Mechanical/Structural Properties of the Key Thin Film Materials Ag, Cu, & Ni for Electronics Applications

Abstract

Metallic films of Ag, Cu, and Ni each of 150, 300, 600 and 1000 nm thick were deposited on Si using E-beam evaporation deposition technique. A shutter was used to successively cover increments of 1² of the wafer at a time, starting with the wafer fully uncovered. A thin titanium layer of 10 nm is first deposited over the entire Si wafers followed by 150, 300, 600, and 1000 nm of the 2² target material. Vacuum conditions at the start were ~1x10-7 torr and reached as high as 2x10-6 torr during the copper deposition due to outgassing. The structural and surface properties were explored using field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). The nanomechanical properties were measured using nanoindentation to determine the modulus and hardness of the Ag, Cu, and Ni films. Nanocrystalline grain structure formation is observed to dominate the crystal film growth. The hardness increases as the film thickness decreases and remains nearly flat for the same film with depth except for the very thin films as they suffer what is known as tapping effect.