Influence of the magnetron on the growth of aluminum nitride thin films deposited by reactive sputtering

Abstract

Aluminum nitride (AlN) thin films deposited on high-vacuum systems without substrate heating generally exhibit a poor degree of c-axis orientation. This is due to the nonequilibrium conditions existing between the energy of the sputtered particles and the energy at the substrate surface. The application of substrate bias or substrate temperature is known to improve the adatom mobility by delivering energy to the substrate; both are hence well-established crystal growth promoting factors. It is well known that low sputtering pressures can be used as a parameter improving the growth of highly c-axis oriented aluminum nitride films at room temperature even without applying bias voltage to the substrate. Generally, the use of high pressures implies thermalization of particles within the gas phase and is considered to increase the energy gap between these and the substrate surface. However, in later experiments we have learned that the use of high processing pressures does not necessarily implies a detriment of crystallographic orientation in the films. By measuring (for the first time to the author’s knowledge) the full width at half maximum value of the rocking curve of the 0002-AlN peak at several positions along the 100mm diameter (100)-silicon wafers on which aluminum nitride thin films were deposited by reactive sputtering, a new effect was observed. Under certain processing conditions, the growth of the AlN thin films is influenced by the target magnetron. More precisely, their degree of c-axis orientation varies at wafer areas locally coincident under the target magnetron. This effect should be considered, especially where large area substrates are employed such as in silicon wafer foundry manufacturing processes.