Yoshikatsu Ishizuki

Integrated module structure of fan-out wafer level package for terahertz antenna

We propose a novel integrated antenna module based on fan-out wafer level package (FO-WLP) for terahertz applications. A patch structure is employed for an antenna since it is suited for low height module. Both an insulator made of polyphenylene ether (PPE) and a reflector made of copper block, together with a chip for high frequency operation, were embedded into a mold used for FO-WLP. A driven element of the antenna and an interconnection between the antenna and the chip were formed by redistribution layer (RDL) technology. The height of the insulator was set to 40 um in order to maximize the radiation efficiency of 300-GHz radio wave. We developed the module and evaluated the performances. Measured frequency characteristics were well matched to analytical result. The measured loss of reflection characteristics of developed module was 3 dB. Therefore, the module achieved 1.5-dB insertion loss even at terahertz frequency. These results exhibit proposing structure is effective as a terahertz module.

Behaviors of flexible vertically aligned carbon nanotube bumps under compression

In this research, bump-shaped Vertically Aligned Mutli-walled Carbon Nanotubes (VACNTs) were bonded to Au substrate as flip-chip interconnect, and the behaviors of the VACNT bumps under compression pressure were studied. In this model, it is considered that the VACNTs were deformed permanently by the friction among the VACNTs. In order to solve the cause of the permanent deformation of the VACNT bumps, the friction among the CNTs during the compression is calculated. Furthermore, the resistance of the VACNT bumps is measured, considering the amount of the deformation of the VACNT bumps.

Surface activated bonding and transfer of Carbon Nanotube bumps to Au substrates

In this research, bump-shaped Vertically Aligned Mutli-walled Carbon Nanotubes (CNTs) were bonded to Au substrate as multilayer interconnect. In order to lower interconnect resistance between the CNT bumps and the Au substrate, the CNT bumps were covered with Au layer by Ar magnetron sputter, subsequently the CNT bumps and the Au substrates were bonded by surface activated bonding using Ar plasma. As a result, the resistance of CNT bumps including interconnect resistance between them was achieved ~10-3 Ω, that was equivalent value with conventional solder alloy.

Surface Activated Bonding between Au layer and vertically aligned Multi-Wall Carbon Nanotubes

In this research, vertically aligned Muti-Walled Carbon Nanotubes (CNTs) and Au-layer were bonded by Surface Activated Bonding method. Vertically aligned CNTs were grown by acetylene-CVD with Fe catalyst and were formed bump shape with 200 µm diameter and around 200 µm height. These CNT bumps and Au layer were cleaned and activated by Argon Fast Atom Beam (Ar-FAB) process and bonded with some load. As a result, MWNTs-Au bonding was succeeded on condition that CNT bumps and Au layer were Ar-FAB processed longer than 300 sec, and bonding pressure was larger than 0.17 MPa, and the average resistance of CNT was 130 kΩ. Furthermore, when the bonding pressure was 0.7 MPa, the average resistance of one was 16 Ω.

A 77 GHz CMOS power amplifier module using multi-layered redistribution layer technology

This paper presents a new millimeter-wave module concept, which is an integration of CMOS monolithic microwave integrated circuits (MMICs) and passive devices fabricated using a redistribution layer (RDL) technology. To realize a low-loss passive circuit, we introduced a multi-metal-layer for the RDL. The first metal layer was used as ground to shield from substrates. The upper metal layers form passive RF components such as a thin film microstrip line (TFMSL), a spiral inductor, a balun, a power combiner, and an antenna. Detailed measurements and characterizations are presented, and we show their applicability in the millimeter-wave region. Moreover, this concept was applied to an integrating millimeter-wave module consisting of four identical CMOS power amplifiers and RDL power combiners to increase the output power. The module exhibited a saturation power of 15 dBm, which is almost four-times higher than that obtained from the single PA. The measured small-signal gain of the PA module was 5.4 dB. The total chip size was 2.2 × 1.5 mm2. The power consumption of the PA module was 800 mW.

Electrical properties of flexible Vertically aligned Carbon Nanotube bumps under compression

In this research, bump-shaped Vertically Aligned Multi-walled Carbon Nanotubes (VA-CNTs) were bonded to Au substrate as flip-chip interconnect, and the behaviors of the VA-CNT bumps under compression pressure were studied. The resistance of the bonded VA-CNT bumps with load was decreased under compression pressure. In this model, it is considered that the VA-CNTs were deformed permanently by the friction among the VA-CNTs. In order to solve the cause of the permanent deformation of the VA-CNT bumps, the friction among the CNTs during the compression is calculated.