Gradient magnetron co-sputtered μm-thick Al–Si films on dielectric substrates for operation in the millimeter-wave band

• Published in: Applied physics letters 2021-10, Vol.119 (16)
• Main Authors: Serdobintsev, Alexey A., Galushka, Victor V., Kozhevnikov, Ilya O., Pavlov, Anton M., Starodubov, Andrey V.
• Format: Article
• Language: English
• Subjects: Absorptivity; Aluminum; Applied physics; Codeposition; Electromagnetic interference; Electromagnetic radiation; Electronic devices; Interlayers; Millimeter waves; Process parameters; Recrystallization; Secondary ion mass spectrometry; Silicon films; Silicon substrates; Thick films; Transmission loss; Wave propagation; Wireless communications
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/5.0058572

Ongoing active development of modern radio frequency electronic devices operating in the millimeter (V) band, such as fifth-generation wireless communications, demands new materials to control electromagnetic interference, compatibility, and reliability of such systems. This work investigates feasibility absorptive non-reflective thin coatings deposition on dielectric substrates using simultaneous magnetron co-deposition. For this, electromagnetic waves propagation in the millimeter band through in micrometer-thick Al–Si films of varied composition was studied. The co-deposition process was controlled by the ratio of sputtered atoms fluxes. Graded segregation was observed under certain parameters of the co-deposition process, resulting in a depth gradient of an aluminum content, as confirmed by the secondary ion mass spectrometry study. A qualitative model was proposed involving aluminum-induced silicon recrystallization happening in the course of a known aluminum interlayer exchange process. The observed Al–Si segregation effect in micrometer-thick films allows for preparation of the non-reflective and absorptive material for operation in the V-band with reflection losses more than 10 dB and transmission losses around 5 dB in the bandwidth of up to 20 GHz.