Comparison of mechanical properties and composition of magnetron sputter and plasma enhanced atomic layer deposition aluminum nitride films

Abstract

A comparative study of mechanical properties and elemental and structural composition was made for aluminum nitride thin films deposited with reactive magnetron sputtering and plasma enhanced atomic layer deposition (PEALD). The sputtered films were deposited on Si (100), Mo (110), and Al (111) oriented substrates to study the effect of substrate texture on film properties. For the PEALD trimethylaluminum-ammonia films, the effects of process parameters, such as temperature, bias voltage, and plasma gas (ammonia versus N 2 /H 2 ), on the AlN properties were studied. All the AlN films had a nominal thickness of 100 nm. Time-of-flight elastic recoil detection analysis showed the sputtered films to have lower impurity concentration with an Al/N ratio of 0.95, while the Al/N ratio for the PEALD films was 0.81-0.90. The mass densities were ∼3.10 and ∼2.70 g/cm 3 for sputtered and PEALD AlN, respectively. The sputtered films were found to have higher degrees of preferential crystallinity, whereas the PEALD films were more polycrystalline as determined by x-ray diffraction. Nanoindentation experiments showed the elastic modulus and hardness to be 250 and 22 GPa, respectively, for sputtered AlN on the (110) substrate, whereas with PEALD AlN, values of 180 and 19 GPa, respectively, were obtained. The sputtered films were under tensile residual stress (61-421 MPa), whereas the PEALD films had a residual stress ranging from tensile to compressive (846 to −47 MPa), and high plasma bias resulted in compressive films. The adhesion of both films was good on Si, although sputtered films showed more inconsistent critical load behavior. Also, the substrate underneath the sputtered AlN did not withstand high wear forces as with the PEALD AlN. The coefficient of friction was determined to be ∼0.2 for both AlN types, and their wear characteristics were almost identical. Published by the AVS.

Thickness-dependent optical properties of aluminum nitride films for mid-infrared wavelengths

“…The measured density of about 3.2 g/cm 3 is the same as reported for the fully crystalline AlN. 53 On the contrary, the ALD samples have density values close to values reported for amorphous or polycrystalline ALD-deposited AlN films (2.5-2.8 g/cm 3 ). 52,55,56 Analysis of the roughness showed that ALD films were smoother compared to sputtered films.…”

“…These results are in a good agreement with reported in literature. 52,53 In addition, the roughness and thickness of thin films were independently estimated by AFM and ellipsometry measurements, respectively. To gain further information on the structural properties of the AlN thin films, X-ray diffraction measurements were performed using the same equipment as in the case of XRR.…”

“…The use of plasma enhanced atomic layer deposition (PEALD) allows much better quality, since it enables the deposition at lower temperatures. 52,53 However, optical properties and ENZ behaviour for mid-IR wavelengths have been mainly studied for AlN deposited by sputtering films 13,[24][25][26] or MBE. 27 In addition, there are very few studies whose optical properties were retrieved for films of different thicknesses.…”

Pulsed Laser Deposition of Aluminum Nitride Films: Correlation between Mechanical, Optical, and Structural Properties

“…The observed hardness behavior is closely related to the processes of film growth and the resulting film microstructure, which yielded variation in the film hardness values. Nevertheless, all H values were within 22-30 GPa range, superior to the ones registered in the case of films obtained by other deposition techniques [22,[42][43][44][45][46][47]. In general, a higher deposition temperature enhances the reaction at the surface of the substrate and promotes the formation of crystallites in the growing film [48].…”

“…From the dependence of these ranking parameters, one can state that the studied PLD AlN films had a very high H 3 /E 2 ratio compared to other AlN coatings [43,44]. From the dependence of these ranking parameters, one can state that the studied PLD AlN films had a very high H 3 /E 2 ratio compared to other AlN coatings [43,44].…”