Toru Kasanami

Characteristics of Zinc Oxide Films on Glass Substrates Deposited by RF-Mode Electron Cyclotron Resonance Sputtering System

There are two types of electron cyclotron resonance (ECR) sputtering systems, DC-mode and RF-mode. In this paper, the properties of zinc oxide (ZnO) film deposited by an RF-mode ECR sputtering system capable of long-term stable deposition are investigated. It is confirmed for the first time that this system is capable of depositing a ZnO film having a sidewall structure without columnar or fibrous grains on an interdigital transducer (IDT)/glass substrate. The ZnO films so deposited were capable of driving the 1.1 GHz fundamental mode in a Rayleigh surface acoustic wave (SAW) without the large propagation loss at high frequencies of conventional ZnO films. Furthermore, ZnO films deposited by this system exhibited 1.7 dB lower insertion loss and a closer agreement between effective electromechanical coupling factors (keff) and the corresponding values calculated with the finite element method (FEM) in comparison with the films deposited by the DC-mode ECR sputtering system.

Ceramic Resonators Using BGS Waves

The BGS wave has generally a large electromechanical coupling factor and a characteristic of complete reflection at stress-free edges of substrates. Therefore, a broad-band super-miniature resonator with a small capacitance ratio can be made utilizing the free-edge reflection property of a BGS wave. A BGS wave resonator using PZT was developed for use as a resonator for an additional trap at fas (adjacent sound carrier frequency) in VIF circuits of TV sets and VCRs. Testing as a trap device in VIF showed that this device has better properties than LC trap circuits.

Piezoelectric Characteristics of ZnO Films Deposited Using an Electron Cyclotron Resonance Sputtering System

Piezoelectric properties of ZnO films were investigated for the first time by means of an electron cyclotron resonance (ECR) sputtering system. It is confirmed that this system is capable of depositing a ZnO film with a large specific resistance, a good piezoelectric property and good c-axis orientation on an interdigital transducer (IDT)/glass substrate at a low temperature (less than 200°C) and under low gas pressure (~10-4 Torr). These ZnO films exhibited excellent surface acoustic wave (SAW) characteristics (insertion losses) and effective electromechanical coupling factors (keff) compared with ZnO films deposited by a conventional RF magnetron sputtering system. Furthermore this ECR sputtering system was capable of depositing a ZnO film capable of driving a Rayleigh SAW of 700 MHz, without heating the substrate (room temperature), while it was impossible to drive such a wave conventionally, using other sputtering systems.

Epitaxially grown Al electrodes for high-power surface acoustic wave devices

A deposition process of epitaxial Al film on a quartz substrate was studied to obtain Al electrodes of surface acoustic wave (SAW) devices having high resistance to stress migration. A vapor deposition system was used under relatively moderate deposition conditions: (1) pressure range of 10 −5 Pa; (2) deposition temperature of 150°C; (3) deposition rate in the range of 120∼240 nm/min. The growth mode of epitaxial Al film differed from that of polycrystalline Al film on quartz

1.86 GHz SAW Filter

Using the third order harmonic wave of Sezawa-mode which propagates in ZnO films epitaxially deposited on R-plane sapphire, high performance filter which is a low insertion loss of 9 dB at 1.86 GHz has been realized.

Deposition and piezoelectric characteristics of ZnO films by using an ECR sputtering system

Piezoelectric properties of ZnO films, were investigated by using an Electron Cyclotron Resonance (ECR) sputtering system. It was confirmed that this system was capable of depositing a ZnO film with a large specific resistance, and good c-axis orientation on an interdigital transducer (IDT)/glass substrate at a low temperature (less than 200/spl deg/C) and in a low gas pressure (/spl sim/10/sup -4/ torr). Furthermore, these ZnO films exhibited excellent SAW characteristics (insertion losses) and effective electromechanical coupling factors (k/sub eff/) compared with ZnO films deposited by a conventional RF magnetron sputtering system. Further, this ECR sputtering system was capable of depositing a ZnO film, without heating the substrate, that was capable of propagating a Rayleigh SAW at 700 MHz for the first time.<<ETX>>

Frequency Trimming of ZnO/Glass SAW Filters

In the process of producing ZnO/glass SAW filters, a desired frequency cannot always be obtained after sputtering ZnO thin films on IDT/glass substrates. It is therefore necessary to adjust the center frequency of each SAW filter within 0.05% tolerance after sputtering. We have developed a method to adjust the center frequency in a mass production process by overlaying organic polymer resin on the substrates. The frequency deviation then becomes very small not only in one lot, but also between lots, and the mass production cost of SAW filters can be reduced tremendously.

VCO Resonators Using ZnO Sputtered Film

Unique, adjustment-free VCO oscillators for FM stereo demodulators have been developed by using ZnO piezoelectric thin films. The reactive sputtering method is employed for the deposition of ZnO thin film transducers onto tuning-bar resonators which are photolithographically fabricated from an ELINVAR alloy metal plate. These oscillators encapsulated in SIP type resin packages (2.5T×6W×8L mm) operate at 76 kHz, and are found to be practical and useful because of their superior features. Excellent performance characteristics are obtained from the FM multiplexer using this oscillator.

Ion Polishing of ZnO Films by an ECR System

SAW filters in the ZnO/IDT/glass type have periodic convexes of the same thickness as the IDT electrodes caused by the presence of IDT on the ZnO film surface and fine irregularities all over the ZnO film surface. These unevenness affects the SAW velocity dispertion. An attempt to smooth the unevenness, using the inclination effect in the ion polishing process, resulted in observation of an interesting surface smoothing phenomenon such as narrowing of the width of convex portions caused by IDT on ZnO film surface, smoothing of small convex spots of fine irregularities found all over the ZnO film surface, etc.

MHz VCO Resonators with ZnO/ELINVAR Structures

New piezoelectric resonators made of ZnO/ELINVAR structures have been developed for 3.58 MHz TV oscillators by utilizing expanding vibrations. In addition to superior features such as a miniature structure, low production cost and achievement of high productivity, the resonators possess a frequency pulling range several times as wide as a conventional 3.58 MHz TV resonator. Trimmer-less, adjustment-free TV chroma circuits have been realized by the incorporation of the new resonators.