Deposition, Characterization, and Modeling of Scandium-Doped Aluminum Nitride Thin Film for Piezoelectric Devices.

Qiaozhen Zhang,Huiling Liu,Yanxue Tang,Xiaomei Qin,Mingzhu Chen,Keat Hoe Yeoh,Xiangyong Zhao,Khian-Hooi Chew,Xiaojuan Sun,Feifei Wang

doi:10.3390/ma14216437

Abstract

In this work, we systematically studied the deposition, characterization, and crystal structure modeling of ScAlN thin film. Measurements of the piezoelectric device’s relevant material properties, such as crystal structure, crystallographic orientation, and piezoelectric response, were performed to characterize the Sc0.29Al0.71N thin film grown using pulsed DC magnetron sputtering. Crystal structure modeling of the ScAlN thin film is proposed and validated, and the structure–property relations are discussed. The investigation results indicated that the sputtered thin film using seed layer technique had a good crystalline quality and a clear grain boundary. In addition, the effective piezoelectric coefficient d33 was up to 12.6 pC/N, and there was no wurtzite-to-rocksalt phase transition under high pressure. These good features demonstrated that the sputtered ScAlN is promising for application in high-coupling piezoelectric devices with high-pressure stability.

Highlights

Piezoelectric devices have received increasing interest in a variety of applications in advanced electronic and in-formation industries, where they are used as resonators, filters, sensors, and actuators [1,2,3,4,5]
aluminum nitride (AlN) has attracted much attention due to its outstanding features such as high thermal stability, high acoustic velocity, low acoustic loss, and in particular, good compatibility with the complementary metal–oxide–semiconductor (CMOS) manufacturing process, which is promising for integrated sensors/actuators on silicon substrates
The investigation results indicated that the ScAlN thin film could maintain material properties under high pressure, which is very important to ensure stable and reliable device performance, especially for piezoelectric pressure sensors

Summary

Introduction

Piezoelectric devices have received increasing interest in a variety of applications in advanced electronic and in-formation industries, where they are used as resonators, filters, sensors, and actuators [1,2,3,4,5]. Mass production of such ScAlN films (more than 20% Sc content) with good crystalline quality and excellent piezoelectric properties is still difficult, and gives rise to limitations in wide applications [19,20,21,22] To deal with this problem, the crystal structure of ScxAl1-xN thin film is worthy of being explored in great detail. Deng et al reported Raman scattering spectra for a sapphire substrate and ScxAl1−xN layers with x = 0–0.16 [24] These previous studies mainly focused on the influences of Sc concentration on piezoelectric properties, so there is still a lack of information from a systematic investigation. The investigation results indicated that the ScAlN thin film could maintain material properties under high pressure, which is very important to ensure stable and reliable device performance, especially for piezoelectric pressure sensors. It is worth mentioning that before sputtering the Mo layer, we used SiO2 and AlN as a seed layer to improve the quality of the ScAlN (002) with better crystal orientation

Characterization of ScAlN Thin Film

Crystal Structure Modeling of ScAlN Thin Film

Findings

High-Pressure Properties