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Shifat ASMZ, Stricklin I, Chityala RK, Aryal A, Esteves G, Siddiqui A, Busani T. Vertical Etching of Scandium Aluminum Nitride Thin Films Using TMAH Solution. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:274. [PMID: 36678027 PMCID: PMC9863442 DOI: 10.3390/nano13020274] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Revised: 01/02/2023] [Accepted: 01/07/2023] [Indexed: 06/17/2023]
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.
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Affiliation(s)
- A. S. M. Zadid Shifat
- Center for High Technology Materials (CHTM), University of New Mexico, Albuquerque, NM 87131, USA
- Optical Science and Engineering (OSE), University of New Mexico, Albuquerque, NM 87131, USA
| | - Isaac Stricklin
- Center for High Technology Materials (CHTM), University of New Mexico, Albuquerque, NM 87131, USA
- Electrical and Computer Engineering (ECE), University of New Mexico, Albuquerque, NM 87131, USA
| | - Ravi Kiran Chityala
- Center for High Technology Materials (CHTM), University of New Mexico, Albuquerque, NM 87131, USA
- Electrical and Computer Engineering (ECE), University of New Mexico, Albuquerque, NM 87131, USA
| | - Arjun Aryal
- Center for High Technology Materials (CHTM), University of New Mexico, Albuquerque, NM 87131, USA
- Optical Science and Engineering (OSE), University of New Mexico, Albuquerque, NM 87131, USA
| | | | - Aleem Siddiqui
- Sandia National Laboratories, Albuquerque, NM 87123, USA
| | - Tito Busani
- Center for High Technology Materials (CHTM), University of New Mexico, Albuquerque, NM 87131, USA
- Optical Science and Engineering (OSE), University of New Mexico, Albuquerque, NM 87131, USA
- Electrical and Computer Engineering (ECE), University of New Mexico, Albuquerque, NM 87131, USA
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Vertical and Lateral Etch Survey of Ferroelectric AlN/Al1−xScxN in Aqueous KOH Solutions. MICROMACHINES 2022; 13:mi13071066. [PMID: 35888883 PMCID: PMC9324062 DOI: 10.3390/mi13071066] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/28/2022] [Revised: 06/24/2022] [Accepted: 06/27/2022] [Indexed: 02/01/2023]
Abstract
Due to their favorable electromechanical properties, such as high sound velocity, low dielectric permittivity and high electromechanical coupling, Aluminum Nitride (AlN) and Aluminum Scandium Nitride (Al1−xScxN) thin films have achieved widespread application in radio frequency (RF) acoustic devices. The resistance to etching at high scandium alloying, however, has inhibited the realization of devices able to exploit the highest electromechanical coupling coefficients. In this work, we investigated the vertical and lateral etch rates of sputtered AlN and Al1−xScxN with Sc concentration x ranging from 0 to 0.42 in aqueous potassium hydroxide (KOH). Etch rates and the sidewall angles were reported at different temperatures and KOH concentrations. We found that the trends of the etch rate were unanimous: while the vertical etch rate decreases with increasing Sc alloying, the lateral etch rate exhibits a V-shaped transition with a minimum etch rate at x = 0.125. By performing an etch on an 800 nm thick Al0.875Sc0.125N film with 10 wt% KOH at 65 °C for 20 min, a vertical sidewall was formed by exploiting the ratio of the 1011¯ planes and 11¯00 planes etch rates. This method does not require preliminary processing and is potentially beneficial for the fabrication of lamb wave resonators (LWRs) or other microelectromechanical systems (MEMS) structures, laser mirrors and Ultraviolet Light-Emitting Diodes (UV-LEDs). It was demonstrated that the sidewall angle tracks the trajectory that follows the 1¯212¯ of the hexagonal crystal structure when different c/a ratios were considered for elevated Sc alloying levels, which may be used as a convenient tool for structure/composition analysis.
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Linkohr S, Pletschen W, Schwarz S, Anzt J, Cimalla V, Ambacher O. CIP (cleaning-in-place) stability of AlGaN/GaN pH sensors. J Biotechnol 2013; 163:354-61. [DOI: 10.1016/j.jbiotec.2012.08.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Revised: 08/16/2012] [Accepted: 08/21/2012] [Indexed: 11/30/2022]
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