Masataka Shinogi

Semiconductor acceleration sensor

This paper reports a practical semiconductor acceleration sensor especially suited for automotive air bag systems. The acceleration sensor includes four beams arranged in a swastika structure. Two piezoresistors are formed on each beam. These eight piezoresistors constitute a Wheatstone bridge. The swastika structure of the sensing elements, an upper glass plate and a lower glass plate exhibit the squeeze film effect which enhances air dumping, by which the constituent silicon is prevented from breakdown. The present acceleration sensor has the following features. The acceleration force component perpendicular to the sensing direction can be cancelled. The cross-axis sensitivity is less than 3 percent. And, the erroneous offset caused by the differences between the thermal expansion coefficients of the constituent materials can be canceled. The high aspect ratio configuration realized by plasma etching facilitates reducing the dimensions and improving the sensitivity of the acceleration sensor. The present acceleration sensor is 3.9 mm by 3.9 mm in area and 1.2 mm in thickness. The present acceleration sensor can measure from -50 to +50 G with sensitivity of 0.275 mV/G and with non-linearity of less than 1 percent. The acceleration sensor withstands shock of 3000 G.

OPTICAL MICROCANTILEVER CONSISTING OF CHANNEL WAVEGUIDE FOR SCANNING NEAR-FIELD OPTICAL MICROSCOPY CONTROLLED BY ATOMIC FORCE

We develop a novel optical microcantilever for scanning near‐field optical microscopy controlled by atomic force mode (SNOM/AFM). The optical microcantilever has the bent channel waveguide, the corner of which acts as aperture with a large tip angle. The resonance frequency of the optical microcantilever is 9 kHz, and the spring constant is estimated to be 0.59 N/m. The optical microcantilever can be operated in contact mode of SNOM/AFM and we obtain the optical resolution of about 200 nm, which is as same size as the diameter of aperture. We confirm that the throughput of optical microcantilever with an aperture of 170 nm diameter would be improved to be more than 10−5.

Fabrication of optical micro-cantilever consisting of channel waveguide for scanning near-field optical microscopy controlled by atomic force

We developed a novel optical micro-cantilever for scanning near-field optical microscopy (SNOM), evaluated its mechanical properties, and applied it for SNOM. A cantilever-shaped channel waveguide with an aperture is bent and it is operated in atomic force mode. By combining the conventional lithography techniques and the waveguide bending process, we can fabricate a probe with the shape and the mechanical properties most desirable for given samples and conditions. Our optical micro-cantilever has resonance frequency similar to the conventional optical fiber probe, and it has a spring constant much smaller. We used this optical micro-cantilever for SNOM in contact mode, and confirmed that it gives optical images with a resolution beyond the diffraction limit.

A novel structure of a piezoresistive accelerometer with lateral detection using precise fabrication techniques

A new type of accelerometer using precise fabrication techniques has been developed. The accelerometer is fabricated on a piezoresistive element with other necessary circuits and runs parallel to the direction of acceleration. The surface width of the fabricated circuit is a few hundred microns thick. The device uses lateral detection to obtain good sensitivity and has achieved sufficient performance in terms of chip miniaturization. The built-in amplifier has been successfully fabricated with a narrow width, and confirmed operation. This is a new approach for making an accelerometer and has a large potential for manufacturing an effective accelerometer.