Influence of metal electrodes on c‐axis orientation of AlN thin films deposited by DC magnetron sputtering

Abstract

Nanocrystalline aluminum nitride (AlN) thin films were deposited on two types of metallic seed layers on silicon substrates, (111) textured Pt and (110) Mo, by reactive DC magnetron sputtering at low temperature (200°C). Both textured films of Pt and Mo promote nucleation, thereby improving the crystallinity and epitaxial growth condition for AlN thin films. The deposited films were examined by X-ray diffraction, scanning electron microscopy and atomic force microscopy techniques. The results indicated that the preferred orientation of crystallites greatly depends upon the kinetic energy of the sputtered species (target power) and seed layers used. Furthermore, AlN thin films with c-axis perpendicular to the substrate grew on both types of metal electrodes at all power levels larger than 100 W. By comparing the structural properties and compressive stresses at perfect c-axis orientation conditions, it is evident that AlN films deposited on (110) oriented Mo substrates exhibited superior properties as compared with Pt/Ti seed layers. Furthermore, less values of compressive stresses (À3 GPa) as compared with Pt/Ti substrates (À7.08 GPa) make Mo preferentially better candidate to be employed in the field of suspended Micro/Nano -electromechanical systems (MEMS/NEMS) for piezoelectric devices.

Hetero-Epitaxial Growth of AlN Deposited by DC Magnetron Sputtering on Si(111) Using a AlN Buffer Layer

“…For that, the Si surface condition is very important. Generally, the wet etching method is used to clean the Si substrate surface [19][20][21]. The impact of the Si substrate surface on the epitaxial growth of AlN was studied [13], but, unfortunately, the mechanism is still not clear.…”

Preparation and Structural Investigation of Ultra-Uniform Mo Films on a Si/SiO2 Wafer by the Direct-Current Magnetron Sputtering Method

“…Molybdenum (Mo), as a kind of important strategic resource, has the advantages of high melting point, great thermal and chemical stability, good thermal and electrical conductivity, low expansion coefficient, and good corrosion resistance. , With the development of thin-film technology, Mo and its alloy compounds have been widely prepared and applied in various fields, such as the electronic industry, solar cells, liquid crystal displays, and 5G radio frequency communications . Among them, the application in filters has received increasing attention in recent years, in which Mo is used as an excellent electrode in the Mo/AlN/Mo sandwich piezoelectric device. − …”

Structural Analysis of Mo Thin Films on Sapphire Substrates for Epitaxial Growth of AlN

“…Therefore, AlN has been considered an optoelectronic material for ultraviolet (UV) light-emitting diodes (LED) and UV detectors [ 11 , 12 ]. In addition, AlN is useful in high-temperature and high-power electronics owing to its high-temperature stability, high thermal conductivity, and large dielectric breakdown field [ 13 , 14 ]. The piezoelectric nature of AlN renders it suitable for various MEMS devices such as bulk acoustic wave (BAW) resonators, thin film bulk acoustic resonators (FBAR), surface acoustic wave (SAW) devices, energy harvesters, microphones, and piezoelectric micromachined ultrasonic transducers (pMUT) [ 15 ].…”