Research/Optically Actuated Cantilever with Built-in Photovoltaic Cells

Optically Actuated Cantilever with Built-in Photovoltaic Cells†

As an extension of the optically actuated device, we have developed a fully integrated photovoltaic cells and micro actuators by using a series of photo diodes and an electrostatically driven actuator as schematically illustrated in the figure on the left. The P-I-N layers of silicon were epitaxially grown on the 30-microns-thick SOI layer, and etched by DRIE to make the isolation trenches to separate the cells. After making the surface insulation of silicon oxide, the N-type silicon was partially exposed to open a contact window. Electrical series connection was made by cascading the P- and N-contact with metallic interconnection.

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Prototype Development†

A cantilever made of metallic layers (40 nm thick chromium, 50 nm thick gold, and 120 nm thick chromium) was also integrated at the output port of the photovoltaic cell. Figure on the left shows a microphotograph of the developed chip. The photovoltaic cell size was 400 microns x 400 microns, and total 4x4 elements were arranged in an area of 1.5 mm x 1.5 mm. Maximum output voltage of 4.8 V was generated under a 1 mW He-Ne light of 632 nm, which was supplied to the actuator to show electrostatic motion at the tip of a 300 microns long cantilever.

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Electrostatic Torsion Mirror Scanner with Built-in Photovoltaic Cells†

By using the SOI part as a mechanical material, a bulk-micromachined optical scanner with integrated photovoltaic cells can be designed as illustrated in the figure on the left.