Active solid-state devices (e.g. – transistors – solid-state diode – Responsive to non-electrical signal – Physical deformation
Reexamination Certificate
2000-01-24
2002-05-14
Jackson, Jr., Jerome (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Responsive to non-electrical signal
Physical deformation
C257S417000, C257S600000, C073S514360
Reexamination Certificate
active
06388300
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application is based upon Japanese Patent Application Nos. Hei. 11-15573 filed on Jan. 25, 1999, and Hei. 11-304323 filed on Oct. 26, 1999, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention:
This invention generally relates to semiconductor physical quantity sensors, and particularly to a semiconductor physical quantity sensor including a beam-structure having a movable electrode for detecting physical quantity such as acceleration, yaw rate, vibration or the like.
2. Related Art:
Conventional semiconductor physical quantity sensor for detecting acceleration, yaw rate, vibration or the like is described in JP-A-9-211022. According to this sensor, abeam-structure having a movable electrode and a fixed electrode confronting with the movable electrode are integrally formed in a semiconductor substrate by processing the semiconductor substrate by using a micro-machine technology. This kind of sensor will be explained in detail hereinafter.
FIG. 83
is a plan view of a semiconductor acceleration sensor.
FIGS. 84
to
87
respectively shows sectional views taken along lines
84
—
84
,
85
—
85
,
86
—
86
and
87
—
87
in FIG .
83
.
In
FIGS. 83
,
84
, a beam-structure
501
ma de of monocrystalline semiconductor material is arranged above an upper surface of a substrate
500
. The beam-structure
501
is supported by four anchor portions
502
a
,
502
b
,
502
c
and
502
d
each of which is protruded from the substrate
500
side, and is arranged with keeping a predetermined distance from the upper surface of the substrate
500
. The beam-structure
501
has beam portions
503
,
504
, a mass portion
505
, and comb-shaped movable electrodes
506
a
to
506
d
,
507
a
to
507
d
. First fixed electrodes
508
a
to
508
d
,
509
a
to
509
d
, and second fixed electrodes
510
a
to
510
d
,
511
a
to
511
d
is fixed to the upper surface of the substrate
500
. Each of the fixed electrodes
508
a
to
508
d
,
509
a
to
509
d
,
510
a
to
510
d
and
511
a
to
511
d
are supported by anchor portions
512
each of which is protruded from the substrate
500
side, and is confronted with each one side of the movable electrodes
506
a
to
506
d
,
507
a
to
507
d
of the beam-structure
501
arranged with keeping the predetermined distance from the upper surface of the substrate
500
. Capacitors are formed between the movable electrodes
506
a
to
506
d
,
507
a
to
507
d
of the beam-structure
501
and the fixed electrodes
508
a
to
508
d
,
509
a
to
509
d.
As shown in
FIG. 84
, the substrate
500
has a structure in which a polysilicon thin film
514
, a lower layer side insulating thin film
515
, a conductive film
516
, and an upper layer side insulating thin film
517
are laminated on a silicon substrate
513
. As shown in
FIG. 83
, four wire patterns
518
to
521
are formed by the conductive thin film
516
. The wire patterns
518
to
521
are wires of the fixed electrodes
508
a
to
508
d
,
510
a
to
510
d
,
509
a
to
509
d
and
511
a
to
511
d.
In this structure, degree of acceleration can be detected by measuring displacements of the beam-structure
501
by way of capacitance changes of the capacitors between the movable electrodes and the fixed electrodes, when acceleration is acted on the beam-structure toward a direction parallel to the surface of the substrate.
The acceleration sensor is manufactured as follows. Here, a method of manufacturing will be explained with reference to
FIGS. 88
to
97
, which are sectional views taken along line
88
—
88
in FIG.
83
.
At first, as shown in
FIG. 88
, a monocrystalline silicon substrate
530
is provided, and a pattern of trenches
531
is formed in the silicon substrate
530
. After that, impurities such as phosphorus are implanted and diffused into the silicon substrate
530
to form electrodes for detecting electrostatic. capacitance. Next, as shown in
FIG. 89
, a silicon oxide film
532
as a sacrificial layer thin film is formed on the silicon substrate
530
, and a surface of the silicon oxide film
532
is flattened. After that, as shown in
FIG. 90
, a silicon nitride film
534
to be an etching stopper during a sacrificial layer etching is formed. Furthermore, openings
535
a
to
535
c
are formed in a laminated structure of the silicon nitride
534
and the silicon oxide film
532
at where anchor portions are to be formed.
Next, as shown in
FIG. 91
, a polysilicon thin film
536
is formed on the openings
535
a
to
535
c
and the silicon nitride film
534
. Impurities such as phosphorus are implanted and diffused to the poly silicon thin film
536
to be a conductive film. A wire pattern
536
a
, a lower electrodes
536
b
(see
FIG. 87
) and anchor portions
536
c
are formed by using a photolithography. As shown in
FIG. 92
, a silicon oxide film
537
is formed on the polysilicon thin film
536
and the silicon nitride film
534
. As shown
FIG. 93
, a polysilicon thin film
538
as a bonding thin film is formed on a surface of the silicon oxide film
537
, and a surface of the polysilicon thin film
538
is mechanically polished to a flat for the purpose of bonding.
Furthermore, as shown in
FIG. 94
, another monocrystalline silicon substrate
539
, which is different from the silicon substrate
530
, is provided, and the surface of the polysilicon thin film
538
and the silicon substrate
539
are bonded each other. As shown in
FIG. 95
, the silicon substrates
530
,
539
are reversed, and the silicon substrate
530
side is mechanically polished to a flat. As show in
FIG. 96
, an interlayer insulating film
540
is formed, and contact holes are formed by dry etching after the photolithography. Furthermore, a silicon nitride film
541
is formed at a predetermined area on the interlayer insulating film
540
, and aluminum electrode
542
is formed by depositing and photolithography.
Finally, as shown in
FIG. 97
, the silicon oxide film
532
is removed by etching using HF-based etchant to make the beam-structure having the movable electrode movable. In other words, the beam-structure
501
and the fixed electrodes (
508
a
,
508
b
etc) are formed in the silicon substrate
530
by removing a predetermined area of the silicon oxide film
532
by the sacrificial layer etching using the etchant.
In these ways, the semiconductor acceleration sensor using a laminated substrate can be manufactured.
However, in such kinds of semiconductor physical quantity sensor, a sensor structure may be complicated, because it needs to electrically isolate the movable electrode from each of the fixed electrodes from a viewpoint of the sensor structure, and it needs to connect wires with separated electrodes. Furthermore, it is difficult to lower a cost because there is a bonding step of the substrate (the substrate
530
and the substrate
539
) as shown in FIG.
94
.
SUMMARY OF THE INVENTION
This invention has been conceived in view of the background thus far described and its first object is to provide a semiconductor physical quantity sensor having a new electric isolation structure and a method of manufacturing the same.
Its second object is to provide a semiconductor physical quantity sensor, in which a beam-structure having a movable electrode and a fixed electrode confronted with the movable electrode are integrally formed in one substrate, having a new electric isolation structure and a method of manufacturing the same.
According to the present invention, a frame portion, a beam-structure and a fixed electrode are divided. Furthermore, at least one insulator is provided at least one of between the frame portion and the movable electrode, and between the frame portion and the fixed electrode. Therefore, it can easily electrically insulate the frame portion from at least one of the movable electrode and the fixed electrode.
According to another aspect of the present invention, a method comprising:
conducting an anisotropic etching from an upper surface of a semiconductor layer
Kano Kazuhiko
Ohara Junji
Ohya Nobuyuki
Denso Corporation
Jackson, Jr. Jerome
Pillsbury & Winthrop LLP
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