Semiconductor device manufacturing: process – Making device or circuit responsive to nonelectrical signal – Physical stress responsive
Reexamination Certificate
2002-02-26
2004-06-29
Kang, Donghee (Department: 2811)
Semiconductor device manufacturing: process
Making device or circuit responsive to nonelectrical signal
Physical stress responsive
C438S050000, C438S051000, C438S052000, C257S417000, C257S418000, C257S419000, C257S420000, C073S715000, C073S718000
Reexamination Certificate
active
06756248
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates generally to a pressure transducer such as a microphone designed to transform static pressure or dynamic pressure (e.g., acoustic vibration) into a corresponding electrical signal and a method of manufacturing the same.
2. Background Art
Japanese Patent Application No. 9-257618 teaches an electro-static capacitance type pressure sensor designed to convert the static or dynamic pressure into corresponding electrical signals. FIG.
7
(
h
) shows this pressure sensor. FIGS.
7
(
a
) to
7
(
g
) show a sequence of manufacturing processes.
First, the substrate
30
is made of a monocrystalline silicon material. Impurities are diffused into a major outer surface of the substrate
30
to form the fixed electrode
40
, the fixed electrode lead
41
, and the lower fixed electrode terminal
42
. Next, the first insulating layer
50
, as shown in FIG.
7
(
a
), is formed over the major outer surface of the substrate
30
. On the first insulating layer
50
, the sacrificial layer
60
, as shown in FIG.
7
(
b
), which is to be removed in a later process is formed.
The first insulating diaphragm layer
70
, as shown in FIG.
7
(
c
), is formed over the sacrificial layer
60
. The second conductive layer
80
is formed on the first insulating diaphragm layer
70
. Preselected portions of the second conductive layer
80
are removed to form the moving electrode
81
, the moving electrode lead
82
, and the lower moving electrode terminal
83
.
Subsequently, the second insulating diaphragm layer
90
, as shown in FIG.
7
(
d
), is formed. A plurality of holes
91
are formed which extend to the sacrificial layer
60
through peripheral portions of the first and second insulating diaphragm layers
70
and
90
. The holes
91
are used as etchant inlets.
Etching liquid is injected through the holes
91
to etch the sacrificial layer
60
isotropically to remove it, as shown in FIG.
7
(
e
), thereby forming the reference pressure chamber
96
between the first insulating layer
50
and the first insulating diaphragm layer
70
. The moving electrode connecting hole
92
and the fixed electrode connecting hole
94
are formed. The moving electrode connecting hole
92
extends to the lower moving electrode terminal
83
through the second insulating diaphragm layer
90
. The fixed electrode connecting hole
94
extends to the lower fixed electrode terminal
42
through the second insulating diaphragm layer
90
, the first insulating diaphragm layer
70
, and the first insulating layer
50
.
A conductive layer is formed on the second insulating diaphragm layer
90
, after which preselected portions of the conductive layer are removed to form, as shown in FIG.
7
(
f
), the moving electrode output terminal
93
and the fixed electrode output terminal
95
. The moving electrode output terminal
93
connects with the lower moving electrode terminal
83
through the moving electrode connecting hole
92
. The fixed electrode output terminal
95
connects with the lower fixed electrode terminal
42
through the fixed electrode connecting hole
94
.
A sealing layer is formed on the second insulating diaphragm layer
90
to seal the holes
91
and then removed, as shown in FIG.
7
(
g
), leaving portions around the holes
91
as sealing caps
97
.
In operation, when the pressure is applied, it will cause a diaphragm consisting of the first and second insulating diaphragm layers
70
and
90
to be deformed. Specifically, both the pressure in the reference pressure chamber
96
and the surrounding pressure act on the diaphragm in opposite directions, so that the diaphragm is deformed by an amount equivalent to a difference between those pressures. This will cause the capacitance of a capacitor consisting of the moving electrode
81
formed on the diaphragm and the fixed electrode
41
to change as a function of the deformation of the diaphragm. The difference between the pressure in the reference pressure chamber
96
and the surrounding pressure acting on the diaphragm is, thus, determined by measuring the value of the capacitance. The measurement of absolute pressure may be accomplished by decreasing the pressure in the reference pressure chamber
96
to a level much lower than a pressure measurable range of the pressure sensor.
The above conventional pressure sensor, however, has the following drawbacks. When the etching liquid used to etch the sacrificial layer
60
and the cleaning solvent therefor are dried, the surface tension of the liquid may cause damage to the diaphragm. The avoidance of this problem requires an additional process of replacing the etching liquid and the cleaning solvent with liquid whose surface tension is smaller before drying them or of drying the etching liquid and the cleaning solvent using a gas liquefied by pressurizing and cooling it.
The formation of the holes
91
for feeding the etching liquid may cause the diaphragm to change in mass and compromise the mechanical strength. In order to minimize this problem, the holes
91
may be formed in the periphery of the diaphragm, however, the drawback is encountered in that it takes much time to etch a central portion of the diaphragm distant from the holes
91
.
In a case where many pressure sensors are formed on a single substrate and separated using a dicing saw in mass production, the water used in the dicing will penetrate into cavities of the substrate, which may cause the pressure sensors to be broken when dried.
SUMMARY OF THE INVENTION
It is therefore a principal object of the present invention to avoid the disadvantages of the prior art.
It is another object of the present invention to provide a pressure transducer having the structure which allows the pressure transducer to be formed easily without damage to component parts such as a diaphragm etc.
According to one aspect of the invention, there is provided a pressure transducer designed to transform an applied pressure into a corresponding electrical signal. The pressure transducer comprises: (a) a substrate having a first surface and a second surface opposed to the first surface; (b) a fixed electrode formed in the first surface of the substrate; (c) a diaphragm attached at a peripheral portion thereof to the first surface of the substrate so as to form a cavity between a central portion thereof and the fixed electrode, the diaphragm having a moving electrode opposed to the fixed electrode through the cavity and being deformed in response to an applied pressure to change a distance between the moving electrode and the fixed electrode as a function of the applied pressure; and (d) a hole formed in the substrate which extends from the second surface to the cavity.
In the preferred mode of the invention, holes are further formed in the substrate which extend from the second surface to the cavity and which are so arranged that adjacent two of all of the holes are disposed at a regular interval away from each other.
The diaphragm is corrugated. Specifically, the diaphragm has a plurality of waved portions formed coaxially.
A groove is formed in the first surface of the substrate within the cavity and which leads to the holes.
A diaphragm support member is disposed within the cavity in contact with an inner wall of the peripheral portion of the diaphragm.
The substrate may be made of a semiconductor substrate having integrated circuit elements which form a detector designed to measure a capacitance between the fixed and moving electrodes.
The diaphragm may be made of an inorganic material such as a compound of silicon and one of oxygen and nitrogen.
The diaphragm may have a wave formed on the peripheral portion thereof. The wave projects to the first surface of the substrate to increase adhesion of the diaphragm to the first surface of the substrate. The wave may be formed by forming a groove in the first surface of the substrate so that the peripheral portion of said diaphragm partially projects to the groove.
According to the second aspect of the invention, there is provided a
Esashi Masayoshi
Ikeda Masaharu
Connolly Bove Lodge & Hutz
Kang Donghee
LandOfFree
Pressure transducer and manufacturing method thereof does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Pressure transducer and manufacturing method thereof, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Pressure transducer and manufacturing method thereof will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3347206