Thermal conductivity of aluminium nitride thin films prepared by reactive magnetron sputtering

Abstract

The relationship between thermal conductivity and microstructures of aluminium nitride films is reported. Films were deposited on silicon substrates by magnetron sputtering of a pure Al target in nitrogen argon plasma at low temperatures (<300 °C) with thickness ranging from 150 to 3500 nm. Balanced and unbalanced magnetron configurations were used for different nitrogen contents in the gas phase. Various microstructures were thus created and their thermal conductivity was measured with the transient hot strip technique. Depending on the crystalline structure of the films, the bulk thermal conductivity of the AlN films at room temperature varied between 2 and 170 W m−1 K−1. Unbalanced magnetron allowed achieving highly dense (0 0 2) oriented AlN films with a grain size in the 100 nm range, a low oxygen content close to 0.5 at% and a resulting bulk thermal conductivity as high as 170 W m−1 K−1. Such a crystalline quality resulted from the ion energy involved in the growth process. In contrast, balanced magnetron led to weakly textured AlN films containing 5 at% oxygen with a grain size in the 30 nm range and a resulting thermal conductivity ranging from 2 to 100 W m−1 K−1 depending on the microstructure. Otherwise, the thermal boundary resistance between AlN films deposited by unbalanced magnetron and the silicon substrate was found to be as low as 1.0 × 10−8 K m2 W−1. Such a value was in good agreement with the thickness of the interfacial amorphous layer determined in the 2 nm range by high resolution transmission electron microscopy.

Review—Investigation and Review of the Thermal, Mechanical, Electrical, Optical, and Structural Properties of Atomic Layer Deposited High-kDielectrics: Beryllium Oxide, Aluminum Oxide, Hafnium Oxide, and Aluminum Nitride

“…Sputter deposited AlN films with similar FWHM were found to exhibit poor to very poor crystallinity and bulk thermal conductivities of 2.6-22 W/mK. 173 Thus, our results are again consistent with the lower bounds observed for sputter deposited AlN. We also note that reductions in AlN thermal conductivity have been attributed to the presence of oxygen contamination.…”

“…173 In this regard, the FWHM for the PEALD AlN film in this study is ∼100 cm −1 . Sputter deposited AlN films with similar FWHM were found to exhibit poor to very poor crystallinity and bulk thermal conductivities of 2.6-22 W/mK.…”

“…The full width at half maximum (FWHM) for the LO mode has been previously correlated to the degree of order in amorphous and poly-crystalline AlN films as well as other properties such as thermal conductivity which will be discussed in more detail later. 168,173 In addition to the Al-N band, the T-FTIR spectrum for the PEALD AlN film also shows smaller absorption bands at 2110 and 3200 cm -1 that are related to Al-H and N-H stretching modes, respectively. 170 The clear presence of these absorption bands in the PEALD T-FTIR spectrum is consistent with the significant amount of hydrogen detected by NRA-RBS in this film.…”

“…For poly-crystalline AlN films deposited primarily by reactive magnetron sputtering, an equally wide range has been reported of 2-210 W/mK where the variation has been strongly correlated to the crystalline quality and grain orientation. 173,[310][311][312][313][314] Interestingly, unbalanced sputtering was found to produce highly crystalline wurtzite AlN films with a strong preferential (0001) c-axis orientation and out of plane thermal conductivities approaching 210 W/mK. 173,310 Balanced sputtering produced AlN films with poorer crystalline quality and greatly reduced values of thermal conductivity.…”

AlN film thickness effect on photoluminescence properties of AlN/carbon nanotubes shell/core nanostructures for deep ultra-violet optoelectronic devices

“…It can be used in several electronic and optoelectronic devices, ultraviolet detector, light emitting diodes and thermal interface materials, to name a few [2,3]. The large Eg value for AlN permits its incorporation into deep UV LEDs [4][5][6] and extreme UV detectors [7], the devices that can be employed for probing intrinsic florescence in protein, equipment/personnel decontamination, photocatalysis and astronomy [1,8].…”