Influence of silicon crystal orientation on piezoelectric textured aluminium nitride deposited on metal electrodes

• Stacks of metal/AlN were deposited on various Si wafer orientations.
• Reduced atomic mismatch between layers enhances textured c-axis (002) orientation of AlN.
• Piezoelectric properties increased with reduction in atomic mismatch amongst layers.
• Metal/AlN had enhanced performance regardless of metal when deposited on (111) Si.

There is a demand for enhancing the piezoelectric properties of aluminium nitride for MEMS applications. This paper investigates the crystallinity and piezoelectric properties of AlN and how they are affected by the crystal structure of the underlying layers. Stacks of metal/AlN were deposited on silicon wafers with different crystal orientations. Three different metals were used (Ti, Al, and Pt) as the bottom electrode in order to determine if the effects are dependent on a particular metal layer. The rocking-curve FWHM of AlN was decreased by approximately 32–35% when the metal/AlN layer was deposited on (111) Si compared to (100) Si, due to the reduced atomic mismatch. The increased (002) orientation of AlN significantly affected the piezoelectric properties resulting in a (d33) increase from 2.68 to 6.09 pm V−1 on Al, −5.01 to −6.31 pm V−1 on Ti, and −5.48 to −7.15 pm V−1 on Pt metal electrodes.