Shoichi Tanifuji

P1H-4 FBAR Characteristics with AlN Film Using MOCVD Method and Ru/Ta Electrode

Film bulk acoustic resonator (FBAR) was fabricated using high oriented AlN(0002) film obtained through the metal-organic chemical vapor deposition (MOCVD) method. We used the Ru/Ta bottom electrode to improve the FBAR resonant characteristics because Ru has a high acoustic impedance and a hexagonal crystalline that is effective to obtaine the high oriented AlN(0002) film. The Ru/Ta electrode had good characteristics under 1100degC in points of the full width at half maximum (FWHM) of Ru(0002), the surface roughness and the electrode resistivity. The evaluated FWHM of AlN(0002) on Ru/Ta at 1050degC was exellent value of 1.2deg. The resonant frequency and anti-resonant frequency of the fabricated FBAR using the Ru/Ta bottom electrode were 5.217 GHz and 5.479 GHz, respectively. The resistance of the FBAR electrodes and of the series-resonance part in modified Butterworth Van Dyke (MBVD) equivalent circuit were improved to 4.3 Omega from 7.0 Omega and to 0.5 Omega from 3.0 Omega compared to the results of previous Mo bottom electrode, respectively. The effective electro-mechanical coupling coefficient (keff 2) of the fabricated FBAR was exellent value of 7.0 % and the evaluated Qr was 329. We successfully fabricated the FBAR with the small insertion loss and the large keff 2 using the Ru/Ta bottom electrode and high oriented AlN(0002) film.

A 3-D radiation pattern measurement method for a 60-GHz-band WPAN phased array antenna

Using 60-GHz band, multi-GHz bandwidth can be achieved for wireless personal area network (WPAN). However, WPAN requires high gain wide coverage area phased array antenna (PAA) for practical uses. In measurement of PAA, 3-D radiation pattern measurement is preferred. However, 2-D measurement is usually used because of limitations of measurement system. In this work, we propose a measurement method that can reduce measurement time for PAA while providing all radiation patterns; and a fixture to measure the 3-D radiation pattern which is compact and provides low interference on antennas radiation pattern.

A high-gain planar dipole antenna for 60-GHz band 3-D system-in-package modules

We propose a novel high-gain 60-GHz band planar dipole antenna for 60-GHz band 3-D system-in-package (SiP) front-end modules. To achieve high gain, we extend a dielectric substrate to main-beam direction. As a result of optimization of dielectric substrate length l, optimal substrate length l is 29.2mm(5.84λ0) since maximum gain of 15.3 dBi is obtained. Compared with l = 1.2 [mm] (0.24λ0), gain enhancement of 10 dB is derived. Simulation results have good agreement with measurement results. Therefore, we confirm validity of configuration of the antenna for gain enhancement at 60-GHz band.

Discussion of millimeter wave FBAR with very thin AlN film fabricated using MOCVD method

We discuss millimeter-wave film bulk acoustic resonator (FBAR) with very thin aluminium nitride (AlN) film fabricated using metal organic chemical vapor deposition (MOCVD) method. In previous works, we have successfully grown c-axis oriented AlN film using MOCVD method on Ru/Ta/SiO2/Si substrate. In this paper, we grew excellent orientation films of AlN and Ru electrodes in MOCVD, although their film thickness were very thin. Experimental results show that full width at half maximum (FWHM) is 1.3° at AlN thickness of 30 nm. In calculating analysis, when both top and bottom electrode thicknesses were 20 nm and AlN thickness was 30 nm, we obtained that resonant frequency was higher than 50 GHz. Therefore, FBAR is possible to apply to millimeter-wave bands devices, also contribute to small-size, low power consumption and low cost for millimeter-wave terminals.

4D-4 Fabrication of FBAR for GHz Band Pass Filter with AlN Film Grown Using MOCVD

Film bulk acoustic resonator (FBAR) using AlN film was fabricated. Metal-organic chemical vapor deposition (MOCVD) was used to obtain high oriented AlN (0002) film. The unloaded Q factor (Qscrr) of fabricated FBAR was improved by reduction of Mo electrode resistance and optimization of cavity etching process. Since Mo nitridation degraded Mo resistance, reaction time between Mo and NH3 became shorter than conventional process to suppress the nitridation during AlN deposition. As a result, Mo resistance was improved to be 12.3 muOmegacm from 26.4 muOmegacm. In conventional process using Bosch process to fabricate cavities, insufficient etching selection ratio between Si/SiO2 of 200 brought incomplete structure of cavities. The etching selection ratio between Si/SiO2 was improved to be 650 by change of the etching process. The evaluated Qscrr of the fabricated FBAR was as high as 1557 at 3.698 GHz. We achieved the high Qscrr value FBAR using high oriented AlN (0002) film by the MOCVD method

A Millimeter-Wave WPAN Adaptive Phased Array Control Method Using Low-Frequency Part of Signal for Self-Directed System

In this paper, we propose a self-directed adaptive phased array control method using the low-frequency part of the signal for a millimeter-wave wireless personal area network, which can reduce the hardware requirement and power consumption compared with those of the conventional digital beamforming method. The signal from each element antenna of the antenna array is phase shifted and down converted to the baseband and then divided into two paths. The first paths are low-pass filtered to extract the low-frequency part of the signals for beamforming control. The second paths from all antennas are combined in-phase in an analog domain and then sampled by two high-speed A/D converters for demodulation. A beamforming algorithm using the sampled low-frequency part of the signal is also proposed. The beamforming calculation time is established as a function of the signal-to-noise ratio, the bandwidth of the low-frequency part, and the required phase control accuracy. The calculated values match the measured results. Using the IEEE 802.15.3c specifications with an eight-element array antenna, the calculation time is less than 5 μs for initial beam establishment and less than 30 μs for beam tracking. Therefore, high-speed beamforming is possible while reducing the power consumption.

5 GHz-band CMOS direct digital RF modulator using current-mode DAC

A 5 GHz-band direct digital radio frequency (RF) modulator is proposed and fabricated in 90-nm complementary metal oxide semiconductor (CMOS) process. Since this modulator directly converts digital base-band (BB) parallel input signal into RF signal, small die size and low d.c. operation are achieved. It consists of an inverter section to obtain digital differential BB signal, a differential current-mode digital-to-analog converter (DAC) section and a local oscillator (LO) switch section. The differential DAC configuration enables low glitch performance at the BB current output and low spurious emission at the RF output. The fabricated direct digital RF modulator performs RF output power of -38.6 dBm with LO leakage of -88.1 dBm at 5GHz LO and 1-MHz BB signals. The core size of fabricated integrated circuit (IC) is 200μm × 170μm and d.c. power consumption is 2.5 mW (2.1 mA/1.2 V).

High sampling rate 1 GS/s current mode pipeline ADC in 90 nm Si-CMOS process

We verifid possibility of high sampling rate and lower power consumption current mode ADC that focused on the most high-speed operation for millimeter-wave broad-band wireless terminal such as wireless personal area network (WPAN). A 5 bit 1 giga-samples-per-second (GS/s) current mode pipeline ADC has been designed and fabricated in 90 nm Si complementary metal oxide semiconductor (CMOS) process. The fabricated ADC has no miscode and increases monotonically. In addition, differential non linearity (DNL) is less than 1.0 and integral non linearity (INL) is less than 1.25, power consumption is 52.8mW on 1 GS/s.

Spurious vibration suppression by film thickness control for FBAR

We have successfully fabricated 5 GHz band FBAR using aluminium nitride (AlN) film by metal organic chemical vapor deposition (MOCVD) method on SiO2/Si substrate. However, large spurious existed between resonant frequency and antiresonant frequency on admittance characteristics of prototype FBAR. We analyzed spurious vibration mechanism using three-dimensional (3-D) simulation. Spurious vibration mode was longitudinal thickness mode by simulation results. Therefore, we completely suppressed the spurious vibration by designing film thickness.

60-GHz band beam forming receiver RFIC for broadband communication phased array antenna module

In order to extend the communication range of the 60-GHz band broadband communication system, beam forming technology has been introduced. Due to the relatively high insertion loss and high phase/amplitude errors of 60-GHz band radio frequency (RF) phase shifter, broadband base band (BB) phase shifter has been focused. In this paper, we have developed a beam forming CMOS receiver RF integrated circuits (RFIC) with 5-bit BB phase shifter for the use in phased array antenna (PAA) receiver module employing 3-dimensional (3-D) system in package (SiP) technology. The receiver RFIC consists of a 7-stages low noise amplifier (LNA), an on-chip balun, a down-mixer, a quadrature-mixer, and a 5bit BB phase shifter. To obtain the broadband characteristic of 2 GHz at RF (i.e., 1 GHz at BB), BB phase shifter has been carefully designed. By using fixed-gain amplifier matrix configuration instead of variable gain amplifiers, broadband and low phase/amplitude errors are obtained. The fabricated receiver RFIC in 90-nm CMOS process exhibits performance applicable to 60-GHz band broadband communication such as IEEE 802.15.3c (channel 2).