Reactive sputter deposition of piezoelectric Sc_0.12Al_0.88N for contour mode resonators

Journal Article · Fri May 11 04:00:00 UTC 2018 · Journal of Vacuum Science and Technology B

DOI: https://doi.org/10.1116/1.5023918 · OSTI ID:1441480

Henry, Michael David ^[1]; Young, Travis Ryan ^[1]; Douglas, Erica Ann ^[1]; Griffin, Benjamin ^[1]

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1. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). MESA Fabrication Facility

Substitution of Al by Sc has been predicted and demonstrated to improve the piezoelectric response in AlN for commercial market applications in radio frequency filter technologies. Although cosputtering with multiple targets have achieved Sc incorporation in excess of 40%, industrial processes requiring stable single target sputtering are currently limited. A major concern with sputter deposition of ScAl is the control over the presence of non-c-axis oriented crystal growth, referred to as inclusions here, while simultaneously controlling film stress for suspended microelectromechanical systems (MEMS) structures. In this paper, we describe 12.5% ScAl single target reactive sputter deposition process and establishes a direct relationship between the inclusion occurrences and compressive film stress allowing for the suppression of the c-axis instability on silicon (100) and Ti/TiN/AlCu seeding layers. An initial high film stress, for suppressing inclusions, is then balanced with a lower film stress deposition to control total film stress to prevent Euler buckling of suspended MEMS devices. Contour mode resonators fabricated using these films demonstrate effective coupling coefficients up to 2.7% with figures of merit of 42. Finally, this work provides a method to establish inclusion free films in ScAlN piezoelectric films for good quality factor devices.

• Research Organization: Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: AC04-94AL85000; NA0003525
• OSTI ID: 1441480
• Report Number(s): SAND--2018-3433J; 662554
• Journal Information: Journal of Vacuum Science and Technology B, Journal Name: Journal of Vacuum Science and Technology B Journal Issue: 3 Vol. 36; ISSN 2166-2746
• Publisher: American Vacuum Society/AIPCopyright Statement
• Country of Publication: United States
• Language: English