Vertical Etching of Scandium Aluminum Nitride Thin Films Using TMAH Solution

Abstract

A wide bandgap, an enhanced piezoelectric coefficient, and low dielectric permittivity are some of the outstanding properties that have made ScxAl1−xN a promising material in numerous MEMS and optoelectronics applications. One of the substantial challenges of fabricating ScxAl1−xN devices is its difficulty in etching, specifically with higher scandium concentration. In this work, we have developed an experimental approach with high temperature annealing followed by a wet etching process using tetramethyl ammonium hydroxide (TMAH), which maintains etching uniformity across various Sc compositions. The experimental results of etching approximately 730 nm of ScxAl1−xN (x = 0.125, 0.20, 0.40) thin films show that the etch rate decreases with increasing scandium content. Nevertheless, sidewall verticality of 85°~90° (±0.2°) was maintained for all Sc compositions. Based on these experimental outcomes, it is anticipated that this etching procedure will be advantageous in the fabrication of acoustic, photonic, and piezoelectric devices.

High-Accuracy Prediction of ScAlN Thin Film Dry Etching Using Machine Learning Driven Regression Modeling

“…The Sc 0.20 Al 0.80 N layers were grown on 150 mm Si ⟨100⟩ substrates utilizing the SPTS Sigma-200 PVD system, adopting a reactive sputtering technique. Comprehensive methodologies for determining the specific concentrations of Al/Sc in the films have been documented thoroughly in the work of ref . A crucial step in effectively delineating the SiO 2 /SiN x hard mask (for ScAlN layer etching) involved employing a nickel metal film, approximately 100 nm in thickness, serving as a temporary mask.…”

“…This nickel layer was subsequently lifted off by utilizing acetone and isopropyl alcohol. Following this, an ICP fluorine process was applied to etch down the SiO 2 /SiN x hard mask layer, thereby exposing the underlying ScAlN layer, as described in refs and .…”

Design and analysis of dual‐band plasmonic band pass filter using meandering step impedance resonator

“…Photonic structures like grating, 5 multislot line, 6 periodic array of nano cavity, 7 and saw tooth‐shaped array 8 are the most common way to design a frequency selective device. In the last decade, several multiple interface systems have been realized for optical waveguides such as metal–insulator (MI), 9 insulator–metal–insulator, 10 piezoelectric material systems, 11–13 and metal–insulator–metal (MIM) 14 . In comparison with all the interface systems, MIM has low‐loss transmission, nanoscale miniaturization, high confinement, wide bandwidth, and large tunability.…”

Realization of high-Q Lamb wave resonator with smooth vertical etching profile for thin film lithium niobate

“…Piezoelectric materials such as AlN, ScAlN, and LiNbO3 (LN) have been widely considered for their use in MEMS devices, frequency control, and sensing applications [1][2][3]. In comparison to other piezoelectric materials, LN has a low intrinsic materials loss, a low-temperature coefficient of frequency (TCF), stable electromechanical responses, CMOS (Complementary Metal-Oxide Semiconductor) compatibility, moderate phase velocity but with low dispersion, low RF losses, GHz capability, and, most importantly, a high intrinsic electromechanical coupling coefficient, making it an excellent candidate for piezoelectric applications [4][5][6].…”