Tsukasa Matsuura

Silicon micro optical switching device with an electromagnetically operated cantilever

Abstract We report on a new concept 2×2 fiber-optical switching device with an electromagnetically operated cantilever. The device is composed of a switching mirror module and a fiber array module. The switching mirror module consists of a fixed mirror, a moving mirror, a cantilever, support glasses and magnets. The mirrors and the cantilever are micromachined from one silicon wafer by deep silicon etching. As the cantilever has a magnetic film on its surface, it is driven by an electromagnet and latched by permanent magnets. The fiber array module consists of four optical fibers with graded index fibers, which are aligned parallel and fixed in a glass holder. The required current to operate the cantilever is 34 mA (0.3 V) and 20 ms for the pulse width, and the required magnetomotive force is 9.5 A·turns. The shortest switching time is 20 ms. The surface roughness of the mirrors are about 30 nm, the reflection loss of one mirror is −0.05 dB, crosstalk is smaller than −60 dB, and the insertion loss is −1.5 dB. Owing to the optical fibers preassembled as a module, the proposed device facilitates the optical path adjustment and the assembly.

A method to evade microloading effect in deep reactive ion etching for anodically bonded glass-silicon structures

Due to the microloading effect, an overetch in through wafer etchings by DRIE has to be taken into account in the fabrication of glass-silicon structures, which results in damages of the silicon surfaces exposed to an ion bombardment. This paper reports on a method, in which a metal layer located on the glass surface and electrically connected with the silicon substrate is used. Even though structures are overetched for a long time, the silicon surfaces remain intact. The results show interdependency between the position of the metal layer on the glass surface and the gap separating the silicon and glass surfaces.

Deformation control of microbridges for flow sensors

Abstract To obtain good performance from a microbridge flow sensor, we have investigated the buckling mechanism of microbridges by fabricating various shapes of bridges. We have achieved deformation control for both the longitudinal axis and the transverse axis of Pt/SiNx double-layered microbridges by appropriate selection of the residual bridge stress of Pt/SiNx structures and of the stress gradient between the Pt film and the SiNx film. The deformation directions of the longitudinal axis of bridges for the beam bridge (Type I) are all the same as that of cantilevers and may be predicted via the stress gradient between the Pt and SiNx films of the bridges. The deflection of the transverse axis of the table bridge supported by four beams (Type II) changes linearly with the residual bridge stress of the Pt/SiNx structure and the deformation changes for the transverse axis are the same as that of completely free films, as predicted from the stress gradient between the Pt film and the SiNx film. The interesting result is that the deformation direction for the longitudinal axis of the Type II bridge is opposite to that of the Type I with the same film structure. We discuss the reason for this opposition via differences in the progress of the anisotropic etching. We consider that this result will expand the range of manufacturable shapes and film structures of microbridges.

A method to evade silicon backside damage in deep reactive ion etching for anodically bonded glass–silicon structures

Abstract Due to the microloading effect, an overetch in through-wafer etchings by deep reactive ion etching (DRIE) has to be considered in the fabrication of glass–silicon structures, which results in damages of the silicon surfaces exposed to an ion bombardment. This paper reports on a new method, in which a metal layer is located on the glass surface and electrically connected with the silicon substrate. Although, structures are overetched for a long time, the silicon surfaces remain intact. The results show interdependency between the position of the metal layer on the glass surface and the gap separating the silicon and glass surfaces.

Micro-optical switch with uni-directional I/O fibers

The authors have developed a new 2/spl times/2 micro-optical switch. The switch features a uni-directional input/output and a drive mechanism with latch functions. The newly developed structure combines two moving mirrors and a fixed V mirror to implement a 2/spl times/2 micro-optical switch with uni-directional input/output. Furthermore, the moving mirrors have been reduced in size by integrating the drive and latch functions by the use of magnetic shaft mirrors and driving coils. The micro-optical switch has been implemented as a module mounted in a ceramic package. The modular switch is 23.5/spl times/9.86/spl times/6.76 mm in size and provides a switching time of 1.3 ms for 15 V (469 mA) and an input pulse width of 1 ms. The reflectivity of the moving mirror is 98.6% (reflection loss: 0.06 dB) and the connection loss between the fixed mirror surfaces is 5.4 dB.

New diaphragm structure based on SiNx/SOG for flow sensor

This paper describes the new diaphragm structure using SiNx/SOG for a micro flow sensor. Its purpose is the measurement of a correct flow rate of various gases or liquids. The proposed sensor consists of sputtered SiNx/Pt/SiNx thin film diaphragm structure, which reduces thermal capacitance. The platinum film resistors detect a change of the temperature distribution on the membrane caused by forced convection. In sensors having these film structures, sputtering methods make it much easier than other film fabrication methods, such as CVD (Chemical Vapor Deposition) to control the internal stress of SiNx film in order to stretch the diaphragm tight. However, the reliability is often spoiled by the column structue of the sputtered SiNx protective film which grows on the platinum film resistors. In order to prevent the growth of the column structure, Spin-On Glass (SOG) film is introduced between platinum film resistors and sputtered SiNx protective film. Because the SOG film is an amorphous structure. SiNx films on SOG films are dense. Additionally, SOG films reduce the step height of platinum film resistors, so the step-coverage of sputtered SiNx protective film is improved.

1/spl times/2 micro mechanical fiber optical switches using v-grooves on sidewall

Fiber optical switches become more important with the growth of fiber based optical telecommunication networks. 1/spl times/2 micro mechanical fiber moving optical switches without reflective index matching oil, using V-grooves on sidewall have been developed. A compact fiber optical switch without reflective index matching oil was fabricated using precise surfaces and accurate fiber positioning by anisotropic TMAH etched V-grooves. It exhibited good performance, of short switching time (2 m sec), low insertion loss (0.5 dB), and low back reflection.

Relationship between internal stress and deformation of diaphragm at elevated temperatures using SEM

This paper reports a study of the relationship between internal stress and deformation of diaphragm at elevated temperatures using scanning electron microscope. It is necessary to make a flat diaphragm in order to obtain good performance for various diaphragm-type sensors using heat transfer, such as flow sensors and accelerometers. When these sensors are used in high temperature environments, a flat diaphragm is required. Therefore, it is very important to observe and control the deformation behavior of a diaphragm at various temperatures. As far as we know, few results have been reported on the observation of deformed diaphragms at elevated temperatures.

Wear behavior of thin film heads for VCR in sliding with metal evaporated tapes

In order to apply thin film heads to digital video cassette recorders, wear behavior, machinability of head materials, and level difference of the heads were evaluated. The tests, performed with metal evaporated tapes, were divided into two stages. First, wear rate and machinability of individual materials were evaluated. It was found that adhesive wear was dominant for every material. Wear damage was especially-severe for metal magnetic films. Machinability was satisfactory for most bulk materials except for those with a hardness of more than 1000 kgf/mm2, ZrO2 ceramics and devitalized glass. Secondly, wear damage and level difference were evaluated using model heads. After the test, a number of flows were formed on sliding surfaces, mainly on the film surfaces, indicating that abrasive wear occurred. With bulk material of larger wear rate, the level difference reached the final value faster and its deviation was smaller. With Co-Zr-Nb magnetic metal and an Al2O3 protective layer, the level difference wa...