Self-Rolled-Up Aluminum Nitride-Based 3D Architectures Enabled by Record-High Differential Stress

Abstract

Aluminum nitride (AlN) continues to kindle considerable interest in various microelectromechanical system (MEMS)related fields because of its superior optical, mechanical, thermal, and piezoelectric properties. In this study, we use magnetron sputtering to tailor intrinsic stress in AlN thin films from highly compressive (−1200 MPa) to highly tensile (+700 MPa), with a differential stress of 1900 MPa. By monolithically combining the compressive and tensile ultrathin AlN bilayer membranes (20−60 nm) during deposition, perfectly curved three-dimensional (3D) architectures are spontaneously formed upon dry-releasing from the substrate via a 3D MEMS approach: the complementary metal-oxide-semiconductor (CMOS)-compatible strain-induced self-rolled-up membrane (S-RuM) method. The thermal stability of the AlN 3D architectures is examined, and the curvature of S-RuM microtubes and helical structures as a function of the cumulative membrane thickness and stress are characterized experimentally and simulated using a finite-element physiomechanic method. By combining AlN with various materials such as metal (Cu) and silicon nitride (SiN x ), AlN-based hybrid S-RuM microtubes with diameters as small as ∼6 μm are demonstrated with a near-unity yield (∼99%). Compared with other stressed thin films for S-RuMs, including PECVD SiN x , magnetron-sputtered AlN-based S-RuMs show better structural controllability and versatility, probably due to the high Young's modulus and stress uniformity. This work establishes the sputtered AlN thin film as a superior stress-configurable S-RuM shell material for high-performance applications in miniaturizing and integrating electronic components beyond those based on other materials such as SiN x . In addition, for the first time, a single-crystal Al 1−x Sc x N/AlN bilayer grown by molecular beam epitaxy is successfully rolled-up with the diameter varying from ∼9 to 14 μm, paving the way for 3D tubular Al 1−x Sc x N piezoelectric devices.

Synthesis and Characteristics of Transferrable Single‐Crystalline AlN Nanomembranes

“…[51] Recently, AlN thin film was grown on Ge and Si substrates by radio frequency magnetron reactive sputtering and molecular beam epitaxy (MBE), respectively, which was released by selective gas-phase dry etching of Ge and Si. [52,53] However, these AlN materials were not transferred to a foreign semiconductor substrate, which greatly limits their potential applications. Thus, it is very important not only to fabricate the electronic devices but also from a fundamental point of view to carry out a detailed study on the transfer of free-standing AlN NMs.…”

Micromachined piezoelectric Lamb wave resonators: a review

“…New structures are another direction of performance advancement for micromachined piezoelectric Lamb wave resonators. Optimization of Lamb wave resonators in the thickness direction is becoming possible with the development of piezoelectric thin film preparation technologies [163,165,166]. As illustrated in equation ( 3), the electromechanical coupling efficiency of a Lamb wave mode is determined by the integration of mutual energy, electric energy, and mechanical energy over the whole resonator.…”

Strain-Controlled Formation Energy and Migration of Nitrogen Vacancy in Al1–xScxN: A First-Principles Study

“…The continuous advancement of information technology demands the development of storage technologies that can efficiently manage the ever-increasing amount of data. In contrast to conventional semiconductor storage methods, ferroelectric memory storage presents a multitude of advantages including high charge density, low power consumption, rapid access speeds, and nonvolatility. − As a result, ferroelectric memory storage has emerged as a field of great potential for further investigation and development. The key part of ferroelectric memory is the ferroelectric material.…”