Highly textured AlN thin films on Si by reactive High Power Impulse Magnetron Sputtering
2015 (English)In: 42nd ICMCTF 2015 International Conference on Metallurgical Coatings and Thin Films, 20–24 April, San Diego, USA: C5. Thin Films for Active Devices, 2015Conference paper, Abstract (Refereed)
Piezoelectric AlN films for electroacoustic devices are typically deposited by magnetron sputtering. Sputtering is compatible with standard microelectronic fabrication processes and requires lower deposition temperatures than other techniques. In order to enhance the texture of AlN, metal seed layers, such as molybdenum, are usually used. Low temperature growth of AlN films for devices where the seed layer cannot be used is challenging.
Here we report on the growth of thin textured (002) AlN layers directly on Si substrates without any metal seed layer. The films were deposited by reactive High Power Impulse Magnetron sputtering (HiPIMS) from an aluminium target in argon/nitrogen atmosphere. Because in HiPIMS very high degree of ionization of the sputtered material is achieved, this technique provides highly ionized flux to the substrate and thus promotes surface diffusion. Moreover, nitrogen dissociation which occurs in the high density HiPIMS plasma increases reactivity of the nitrogen. For comparison, pulsed DC sputtering was also performed under identical conditions.
We show that for 200 nm thick AlN films grown on (100) Si, the HiPIMS process produces well textured (002) films already at room temperature while the pulsed DC films are very poor. At 400°C, which is the optimal temperature for pulsed DC deposition, the HiPIMS films are superior with the FWHM value of 5.1 and 14.2° for the HiPIMS and pulsed DC, respectively. No appreciable stresses were observed in the films. The HiPIMS deposition process is more robust than standard DC sputtering and provides sufficient energy input even for configurations with relatively large target-to-substrate distance. It is therefore suitable also for co-sputtering of ternary nitrides based on AlN.
Place, publisher, year, edition, pages
Other Materials Engineering
IdentifiersURN: urn:nbn:se:uu:diva-269737OAI: oai:DiVA.org:uu-269737DiVA: diva2:885078
42nd ICMCTF 2015 International Conference on Metallurgical Coatings and Thin Films, 20–24 April, San Diego, USA