The mechanical properties of atomic layer deposited alumina for use in micro- and nano-electromechanical systems

Mechanical characterization of atomic layer deposited (ALD) alumina (Al2O3) for use in micro- and nano-electromechanical systems has been performed using several measurement techniques including: instrumented nanoindentation, bulge testing, pointer rotation, and nanobeam deflection. Using these measurement techniques, we determine Young's modulus, Berkovitch hardness, universal hardness and the intrinsic in-plane stress for ALD Al2O3. Specifically, measurements for ALD Al2O3 films deposited at 177 °C with thicknesses between 50 and 300 nm are reported. The measured Young's modulus is in the range of 168–182 GPa, Berkovitch hardness is 12.3 GPa, universal hardness is 8 GPa, and the intrinsic in-plane stress is in the range of 383–474 MPa. Multiple measurements of the same material property from different measurement techniques are presented and compared. ALD Al2O3 is an advantageous material to use over various forms of silicon nitride, for micro- and nano-electromechanical systems due in part to the low deposition temperature that allows for integration with CMOS processing. Also, Al2O3, unlike silicon nitride, has a high chemical resistance to dry-chemistry Si etchants. Although ALD Al2O3 has recently been used as both a coating and a structural layer for micro- and nano-electromechanical systems, its mechanical properties were not previously described.