Hisao Okuda

A rotational comb-driven micromirror with a large deflection angle and low drive voltage

We have designed, fabricated, and tested a V-shaped torsion bar for use with a comb-driven micromirror. This torsion bar suppressed undesired sticking of the comb teeth, and enabled a large rotational angle and a low drive voltage. We observed 5-degree rotation of a comb-driven micromirror with a drive voltage of 90 V.

A 2-axis comb-driven micromirror array for 3D MEMS switches

Presents a new architecture of a 2-axis comb-driven micromirror array that combines a large deflection angle in a stationary operation, a low drive voltage, and easy scalability for a 3D MEMS switch. By using an SOI wafer with 100-/spl mu/m thick top and bottom Si layers and a 1-/spl mu/m buried oxide layer and, bulk micromachining with DRIE, we fabricated a 2-axis comb-driven micromirror array with a V-shaped torsion bar and comb teeth. The V-shaped torsion bar that has an optimized spring constant that enables both a large rotational angle and a low drive voltage without creating the undesired pull-in motion of the comb teeth. To implement a 2-axis tilt motion, we fabricated a gold bump for creating a gap under the comb teeth on the electrode substrate and mounted the mirror array substrate onto the electrode substrate by using the flip-chip-transfer technique. We fabricated an 80/spl times/80 switch chip and achieved a +/-5 degree rotation of the 2-axis stationary operation with a 60-V drive voltage.

A full-time accelerated vertical comb-driven micromirror for high speed 30-degree scanning

This paper presents a new structure and driving method for a vertical comb-driven micromirror which enables full-time acceleration and mechanical 30-degree scanning with a 4-mm long mirror. Its optimal application is as a scanning mirror for laser beam printers, replacing polygon mirrors which have technical limits in relation to scanning speed.

A multi-chip directly mounted 512-MEMS-mirror array module with a hermetically sealed package for large optical cross-connects

A 512 MEMS mirror array module with a hermetically sealed package for large optical cross-connects is constructed by using newly developed multi-chip direct mounting (MCDM) technology and is demonstrated to enable a plusmn5 degree rotation of the two-axis stationary operation under a drive voltage of 160 V, while having a high resonance frequency of 2 kHz

A multi-step DRIE process for a 128 /spl times/ 128 micromirror array

A multi-step DRIE process for fabricating a vertical comb-driven micromirror array with five different heights was developed. This process was used to fabricate a dual-axis 128 /spl times/ 128 micromirror array with a high resonance frequency.

A highly reliable single-crystal silicon RF-MEMS switch using Au sub-micron particles for wafer level LTCC cap packaging

This paper presents a small packaged, reliable and low-voltage driven RF-MEMS switch for wireless communication. We developed novel fabrication process of an RF-MEMS switch using a PZT actuator without a backside cavity to realize wafer-level-packaging (WLP). We also developed organic-free WLP process using sub-micron Au particles simultaneously to contact electrically and to seal hermetically with a low temperature co-fired ceramics (LTCC) wafer as a cap on a multilevel height RF switch. As a result, we obtained a small packaged SPST switch, which is in the small size of 1.4 × 0.9 × 0.8 mm. The RF-MEMS switch operated keeping a low contact resistance (<;3 Ω) up to 1 billion cycles at a low-power condition (DC 1 mW).

Piezoelectric reliable RF-MEMS switch with narrow contact-gap using wafer-bond packaging

This paper presents a low-cost packaged and reliable piezoelectric-actuated RF-MEMS switch for mobile communications. We fabricated a stiff single crystal silicon (SCS) beam that has an actuator and a contact bump on an SOI wafer without backside etching. We bonded the wafer to a ceramic cap wafer, directly packaging a switch with a contact gap of 0.5-μm not using sacrificial layers. The switch operated up to 1 billion cycles keeping a low insertion loss (<;0.4 dB up to 5GHz) at 20-V driving voltage. The surface mountable SPST switch was 1.6 × 1.1 × 0.8 mm in size.

Effect of frequency in the 3D integration of a PZT-actuated MEMS switch using a single crystal silicon asymmetric beam

This paper presents the effect of frequency of radio frequency microelectromechanical system (RF MEMS) 3D integration with an actual device. A piezoelectric transducer (PZT)-actuated RF MEMS switch that uses a single crystal silicon asymmetric beam was designed, fabricated, and evaluated. We successfully drove a stiff beam (with spring constant >; 2,000 N/m) despite a low voltage (<;15 V). The switch lifetime was 4 × 107 cycles at low contact resistance and more than 1 × 109 cycles for the PZT actuator. The overall insertion loss and isolation were -0.3 dB and -25 dB, respectively, up to 5GHz. The effect of frequency of 3D integration was simulated with an RF MEMS switch and a ground plane placed over it. We discovered that a 3D IC comprising a control IC and an RF MEMS switch with a distance of more than 80 μm was successfully integrated.

A scanning mirror with extremely high resonance frequency up to 0.51 MHz using both torsion and buckling springs

This paper reports about a single-crystalline Si mirror of around a millimeter in size used for laser beam scanning in an optical measurement system in a vacuum. The miniature mirror is capable of scanning at an extremely high-speed of up to 0.5 MHz, and uses a new rotation vibration mechanism involving both torsion and buckling springs. The mirror is fabricated using deep reactive-ion-etch (DRIE) and anodic bonding technologies. The efficacy of the new mechanism is demonstrated by measuring two fabricated scanning mirrors, one having a 0.15 MHz resonance frequency and the other a 0.51 MHz resonance frequency. This paper will explain the concept, fabrication process and discuss the experimental results.