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We investigated the growth per cycle (GPC) for SiO2 and HfO2 on n-GaN/native oxide and p-Si/SiO2 substrates by plasma-enhanced atomic layer deposition using tris(dimethylamino)silane and tetrakis(dimethylamino)hafnium precursors, respectively, and O2 plasma gases. On the basis of the estimated GPC, we also examined the characteristics of n-GaN/Hf0.57Si0.43Ox/Pt capacitors with an inserted interfacial layer (IL) such as subnanometer-thick HfO2 and SiO2. We found that the GPC for SiO2 on n-GaN/native oxide was slightly smaller than that on p-Si/SiO2, whereas the GPC for HfO2 was the same on both substrates. The GPC for ALD-SiO2 could be reasonably plotted on the basis of the relationship between the GPC and the difference in electronegativity between the metal and oxygen in the metal-O underlayers including native oxide (Ga2O3) on GaN. On the basis of the GPC on n-GaN, Hf0.57Si0.43Ox (23 nm) capacitors were fabricated without and with a HfO2-IL (0.3 and 0.5 nm) or SiO2-IL (0.3 and 0.6 nm). These capacitors exhibited similar leakage current properties and a high breakdown electric field greater than 8.3 MV cm−1. No frequency dispersion and a flatband voltage (Vfb) hysteresis smaller than 50 mV were observed for all of the capacitors. Compared with the SiO2-IL [Si-rich HfSiOx (Si: > 0.43)] capacitors, the HfO2-IL [Hf-rich HfSiOx (Hf: > 0.57)] capacitors showed a smaller interface state density [(1.2–1.7) × 1011 cm−2 eV−1 at −0.4 eV from the conduction band] and a smaller negative Vfb shift. Therefore, the Hf-rich HfSiOx (Hf: > 0.57) grown using a HfO2-IL at the n-GaN/HfSiOx interface plays a substantial role in improving the electrical properties of n-GaN/HfSiOx capacitors. [ABSTRACT FROM AUTHOR]

A 16-element phased-array receiver has been developed for advanced W-band automotive radars. The phased-array receiver is based on a single SiGe chip with RF beamforming capabilities, which is packaged using low-cost bond-wire techniques and attached to a 16-element linear microstrip array. The antenna results in a directivity of 29.3 dB and a gain of 28.0 dB at 77–81 GHz, and can be scanned to \pm \50^\circ in the azimuth plane in \sim \ 1^\circ steps. The packaging details are presented together with the steps taken to ensure a wideband impedance match and low coupling between the phased-array channels. Gain measurements done at 79 GHz agree well with simulations. The 16-element phased array receiver was used with a 2-element frequency-modulated continuous-wave transmitter at 76.5–77 GHz and high-resolution millimeter-wave images were obtained. The work shows that complex millimeter-wave phased arrays can be packaged using traditional bond-wire techniques, and can be a powerful solution for advanced automotive radars. [ABSTRACT FROM AUTHOR]

e (for fabrication of advanced structures). Cu-Sn TLP bonding is employed herein because of its high remelting temperature and desirable thermal and electrical conductivities. The bonding starts with a stack of Cu-Sn-Cu metal layers that eventually transforms to Cu-Sn alloys. As the alloys have melting temperatures (Cu3Sn: > 600 ?C, Cu6Sn5: > 400 ?C) significantly higher than the process temperature, the process can be repeated without damaging previously bonded layers. A Cu-Sn TLP bonding process was developed using thin Sn metal sheets inserted between copper layers on silicon die and direct bonded copper substrates, emulating the process used to construct automotive power modules. Bond quality is characterized using (1) proof-of-concept fabrication, (2) material identification using scanning electron microscopy and energy-dispersive x-ray spectroscopy analysis, and (3) optical analysis using optical microscopy and scanning acoustic microscope. The feasibility of multiple-sided Cu-Sn TLP bonding is demonstrated by the absence of bondline damage in multiple test samples fabricated with double- or four-sided bonding using the TLP bonding process. [ABSTRACT FROM AUTHOR]