Its strongly enhanced piezoelectric response  makes aluminum scandium nitride (AlScxN) a very promising candidate for use in next generation RF filter devices, microphones and speakers, energy harvesting devices, piezoelectric micro-machined ultrasonic transducers and many other sensors and actuators. The industrial use of AlScxN requires a reliable deposition technology to control the growth of films in the correct (002) textured wurtzite structure within tight specifications regarding uniformity and repeatability. Further, the process has to be mastered on multiple substrate and electrode materials due to the wide variety of possible applications.
In a previous edition of LAYERS, we reported AlScxN films grown using Evatec Multisource Technology – a unique solution for deposition of AlScxN films by co-sputter of metallic aluminum and scandium targets. It enables the deposition of films with any desired Sc concentration independent of the availability of AlScx compound targets. For single target deposition of high uniformity AlScx compound films, targets with the size of 300mm diameter are required to coat 200mm substrates uniformly. Until now such targets have only been available with a limited Sc concentration below 10at%. Quite recently, target manufacturers succeeded in providing the first 300mm prototype targets to Evatec with a high scandium concentration. This article will report on AlScxN films sputtered from 300mm single compound targets with a nominal Sc concentration of 30at%. The obvious advantages of using larger compound targets instead of co-sputtering technology is the increased productivity (by a factor of 5) and significantly better film uniformity – in particular thickness and stress.