Sound-electricity conversion device, array-type ultrasonic...

Details Sound-electricity conversion device, array-type ultrasonic... Sound-electricity conversion device, array-type ultrasonic...

2006-01-30

2010-10-19

Kuntz, Curtis (Department: 2614)

Electrical audio signal processing systems and devices

Electro-acoustic audio transducer

Microphone capsule only

C381S189000

Reexamination Certificate

active

07817811

ABSTRACT:
The present invention aims to stabilize sound-electricity conversion characteristics of a diaphragm-type sound-electricity conversion device as well as to decrease the noise level of an ultrasonic diagnostic apparatus using the sound-electricity conversion device. The sound-electricity conversion device is configured by a capacitor cell including a lower electrode formed on a silicon substrate and an upper electrode over the lower electrode, the lower and upper electrodes sandwiching a cavity. An electrode short-circuit prevention film is formed on the upper electrode on the cavity side. The electrode short-circuit prevention film is formed of a material with an electrical time constant shorter than 1 second and longer than 10 microseconds, such as silicon nitride containing a stoichiometrically excessive amount of silicon. As a result, the electrode short-circuit prevention film has small electric conductivity, and thus it is made possible to prevent the film from being charged with electric charge and to avoid the drift of the electric charge. Consequently, the sound-electricity conversion characteristics of the sound-electricity conversion device stabilize, and further the sound noise level of the ultrasonic diagnostic apparatus decreases.

REFERENCES:
patent: 6320239 (2001-11-01), Eccardt et al.
patent: 2004-350702 (2004-12-01), None
patent: 2005-528010 (2005-09-01), None
patent: PCT/FR03/000427 (2003-08-01), None
M. Haller and B.T. Khuri-Yakub, “A Surface Micromachined Electrostatic Ultrasonic Air Transducer” Proceedings of Ultrasonic Symposium, pp. 1241-1244, Nov. 1, 1994.

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