Investigation of ScAlN for piezoelectric and ferroelectric applications

SCXAL1-XN is a promising material to expand the application range of nitride materials, since scandium increases the piezoelectric constants while retaining the crystalline wurtzite structure. In this work, stationary reactive pulse magnetron sputtering is usedfor the deposition offunctional layers with a scandium contentx =0EL0.44.Layer morphology, piezoelectric properties and breakdown voltage are studied XRD measurements reveal that high scandium content yields to a weak wurzite formation. The lattice constant dependent on the parameter x is calculated on the base ofXRD data and the curve characteristic agrees with the density functional theory. The highestpiezoelectric coefficient d33 was observed at a scandium content of36.6 %, it amounts to 27.5 pC/N.Parallel capacitor structures are generated by means of chlorine-basedICP etching and lift-offstructuring of the top electrodes. Technological details of the structuring process are presented The etch rate depends strongly on the scandium content. Thepermittivity was determined on the base of these test structures. It increases significantly with increasing scandium content. High capacitance values up to 7.4 nF were measured The adequate breakdown voltage of51 Vfor scandium concentrations of x=0.22 or higher suggest a use ofsuch layers for integrated thin film capacitors in addition to well-triedpiezoelectric applications.