Structural Properties of Sputtered MgO Films : Dielectric Breakdown and Scratch Failure

Structural properties of magnesium oxide (MgO) thin films are discussed from the dielectric breakdown measurement. Films of MgO of about 80 nm in thickness were prepared by rf-sputtering in an argon atmosphere at pressures of 0.24, 1.32 and 2.85 Pa. The breakdown took place suddenly in a staircase voltage-elevation measurement. Films sputtered at low pressures had a high breakdown strength. We observed a slow breakdown by employing the current-limitation mode, and a characteristic behavior appeared in the I-V profiles. As the current increased, the voltage was apt to decrease in films sputtered at 0.24 Pa, but it increased in films prepared at high pressures. The difference also appeared in the surface morphology of the breakdown points and the mechanical damage of the films in the scratch test. The correlation suggests that the grain boundary structure of MgO films plays an important role on these fracture properties