Active solid-state devices (e.g. – transistors – solid-state diode – Integrated circuit structure with electrically isolated... – Passive components in ics
Reexamination Certificate
2000-10-04
2003-05-20
Thomas, Tom (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Integrated circuit structure with electrically isolated...
Passive components in ics
C381S113000, 43, C073S724000
Reexamination Certificate
active
06566728
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor device used for an electrostatic microphone and others.
Multiple electret capacitor microphones (hereinafter called ECM) which can be easily miniaturized are used for a mobile telephone. Technique for configuring a capacitor on a semiconductor substrate where integrated circuits such as an amplifier are configured to realize the further miniaturization is disclosed in Japanese Patent Publication No. 11-88992 for example. To detailedly describe the technique, a stationary electrode layer is formed on a semiconductor substrate, a vibrating diaphragm is attached over the stationary electrode layer via a spacer and a capacitor is composed by the stationary electrode layer and the vibrating diaphragm.
FIG. 4
shows the structure. A stationary electrode layer
112
, an insulating film
113
, a spacer
114
and a vibrating diaphragm
115
are sequentially laminated on the surface of a silicon semiconductor substrate
111
and the lamination is installed in a package
118
having a hole
116
. A reference number
117
denotes cloth and it is provided if necessary. A junction-type FET for impedance conversion, further an amplifier and a noise canceling circuit and others are integrated on the surface of the semiconductor substrate
111
according to a normal semiconductor process. The capacitance value of a capacitor formed by the vibrating diaphragm
115
and stationary electrode layer
112
varies because aerial vibration vibrates the vibrating diaphragm
115
, the variation of the capacitance value is input to the FET and the FET converts it to an electric signal.
However, the capacitor microphone cannot be housed in a complete sealed container because of its property. Structure that aerial vibration can reach the vibrating diaphragm
115
via the hole
116
is necessarily required. The maintenance of a state in which aerial vibration is enabled means that it is also impossible to completely intercept light.
At least a few circuit elements integrated in the semiconductor substrate
111
are composed of PN junction. When light is incident on such a silicon semiconductor substrate having PN junction, dark current is caused by photoelectromotive force. There is a defect that the caused dark current flows in the circuit element, noise is caused and the malfunction of the circuit is caused.
SUMMARY OF THE INVENTION
The present invention is made to solve the problem described above.
According to first aspect of the invention, a semiconductor device comprising: a semiconductor substrate in which circuit elements are integrated; a stationary electrode layer formed over the semiconductor substrate; a spacer formed around the stationary electrode layer over the semiconductor substrate, for attaching a vibrating diaphragm composing a capacitor together with the stationary electrode layer; a dummy island provided in the semiconductor substrate surrounding the stationary electrode layer; and means for applying fixed potential to the dummy island.
According to the second aspect of the invention, a semiconductor device defined as the first aspect of the invention, further comprising a shield metal for intercepting light, wherein the circuit element arranged around the stationary electrode layer, wherein the shield metal is formed so that the circuit element is covered, wherein the dummy island is arranged between the shield metal and the stationary electrode layer.
According to the third aspect of the invention, a semiconductor device defined as the first aspect of the invention, wherein the fixed potential is supply potential Vcc.
According to the fourth aspect of the invention, a semiconductor device comprising: a semiconductor substrate includes a one conductive type of semiconductor layer, a reverse conductive type of epitaxial layer formed on the semiconductor layer, and plural islands formed to separate the epitaxial layer by one conductive type of separated areas; a circuit element formed in the island; a stationary electrode layer formed over the semiconductor substrate; a spacer formed around the stationary electrode layer over the semiconductor substrate, for attaching a vibrating diaphragm composing a capacitor together with the stationary electrode layer; a dummy island separated by the separated area, which is provided in the semiconductor substrate surrounding the stationary electrode layer; and means for applying fixed potential to the dummy island.
According to the fifth aspect of the invention, a semiconductor device defined as the fourth aspect of the invention further comprising shield metal for intercepting light formed over the island having the circuit element.
According to the sixth aspect of the invention, a semiconductor device defined as the fifth aspect of the invention, wherein the shield metal further covers a part of the dummy island.
According to the seventh aspect of the invention, a semiconductor device defined as the fifth aspect of the invention, wherein the shield metal is separated from the stationary electrode layer in a horizontal direction by a clearance portion.
According to the eighth aspect of the invention, a semiconductor device defined as the seventh aspect of the invention, wherein the clearance portion is arranged above a part of the dummy island.
According to the ninth aspect of the invention, a semiconductor device defined as the fourth aspect of the invention, wherein the fixed potential is supply potential Vcc.
According to the tenth aspect of the invention, a semiconductor device defined as the fourth aspect of the invention, wherein a ground potential GND is applied to the semiconductor layer and the separated areas.
According to the eleventh aspect of the invention, a semiconductor device defined as the fourth aspect of the invention, wherein PN junction formed by the dummy island composes a dummy photodiode.
REFERENCES:
patent: 5321989 (1994-06-01), Zimmer et al.
patent: 5470797 (1995-11-01), Mastrangelo
patent: 6308398 (2001-10-01), Beavers
patent: Hei. 11-88992 (1999-03-01), None
patent: 112095 (2001-04-01), None
Ohbayashi Yoshiaki
Ohkoda Toshiyuki
Okawa Shigeaki
Osawa Shuji
Saeki Shinichi
Fish & Richardson P.C.
Nadav Ori
Sanyo Electric Co,. Ltd.
Thomas Tom
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