Measuring and testing – Fluid pressure gauge – Electrical
Reexamination Certificate
1999-03-31
2001-02-27
Oen, William (Department: 2855)
Measuring and testing
Fluid pressure gauge
Electrical
Reexamination Certificate
active
06192761
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sensor chip (semiconductor component for sensors) used for sensors for measuring pressure, acceleration, flow rate, temperature and the like, manufacturing method of the sensor chip and a laminated wafer used for manufacturing the sensor chip.
2. Description of Related Art
Japanese Patent Application Laid-Open No. Hei 8-235387 discloses a sensor chip used, for example, for electro-capacitance type pressure sensor.
The chip has a laminated structure where an electrode layer
200
is sandwiched between two glass substrates
201
and
202
. As shown in
FIG. 15
, the electrode layer
200
is composed of a conductive silicon substrate and has a thick portion
200
B around thin diaphragm
200
A. The first glass substrate
201
and the second glass substrate
202
is bonded to the peripheral thick portion
200
B. A predetermined gap is respectively formed between the respective glasses
201
,
202
and the diaphragm
200
A because the diaphragm
200
A is thin relatively to the thick portion
200
B.
When pressure is applied from a pressure inlet (not shown) provided to the second glass substrate
202
in the chip, the diaphragm
200
A bends toward the first glass substrate
201
by the pressure from the second glass substrate
202
. An electrode (not shown) is disposed on the first glass substrate
201
opposing the diaphragm
200
A and electro-capacitance between the electrode and the diaphragm
200
A changes when the diaphragm
200
A bends. The pressure can be measured by electrically processing the change in the electro-capacitance.
For conducting such electric processing, respective signal receiving portions
203
and
204
for taking out electric potential of the electrodes (usually provided in plural) disposed on the first glass substrate
201
through a through-hole and another signal receiving portion
205
for taking out electric potential of the diaphragm
200
A through the side of the chip are provided on a surface of the first glass substrate
201
(remote from the electrode layer
200
). The signal receiving portions
203
to
205
and an outside circuit substrate for signal-processing are wired by wire-bonding etc. In the signal receiving portions
203
to
205
, the signal receiving portion
205
for the diaphragm
200
A has a terminal
205
A provided in advance on the first glass substrate
201
and a continuous conductive layer
205
B connecting the terminal
205
A and an end of the thick portion
200
B of the silicon substrate exposed on a side of the sensor chip. The conductive layer
205
B is formed by vapor deposition, thermal spraying etc.
However, since the conductive layer
205
B of the signal receiving portion
205
stretches to a lower end (a periphery of the second glass substrate
202
remote from the diaphragm
200
A) of the sensor chip, the circuit substrate touches the conductive layer
205
B when the chip is mounted to the circuit substrate, thereby causing possible electric failure such as noise pickup.
For overcoming above disadvantage, some special jig may be used for vapor deposition to prevent the conductive layer
205
B from stretching to the lower end of the lower glass
201
.
However, the structure of the jigs can be too complicated in the above arrangement, thereby making the attachment of the chip difficult. Additionally, since the small chip has to be carefully handled by a pair of tweezers and the like and the chips are collectively produced from a single wafer by a order of some hundreds pieces when the chip is attached to the jig, enormous time is necessary for attaching all the chips.
In order to cope with the electric failure and the disadvantage in productivity according to the structure shown in
FIG. 15
, another sensor chip is proposed, in which the thick portion
200
B of the silicon substrate is exposed by a cut
206
as shown in FIG.
16
and the signal of the diaphragm
200
A is directly taken out therefrom.
Such sensor chip can be manufactured by following steps of: drilling an opening of circular shape, for example, to the first glass substrate
201
in advance; forming the laminated wafer for sensor chip by laminating the first glass substrate
201
to the silicon substrate; and cutting the wafer at the position crossing the opening. According to the sensor chip, since the upper side of the silicon substrate exposed by the cut
206
is used as the signal receiving portion, the signal receiving portion is not required to be provided around the side of the chip, thereby making the vapor deposition on the side of the chip (cut surface exposed by cutting the wafer) unnecessary. Accordingly, when the signal receiving portion is formed, the vapor deposition can be done in the state of the wafer, i.e. without being cut into respective chips for forming the signal receiving portion, thereby greatly facilitating the attachment of the jigs and the like in vapor depositing step.
However, since the surface of the electrode layer
200
of the sensor chip exposed by the cut
206
forms a signal receiving portion as shown in
FIG. 16
, the size of the sensor chip increases. In other words, the surface of the electrode layer
200
exposed by the cut
206
has to be of a certain size for bonding and the like. However, the thick portion
200
B used for the signal receiving portion also works for bonding the respective glass substrate
201
and
202
on the periphery of the diaphragm
200
A. Accordingly, it is difficult to secure an area for the signal receiving portion to ensure the bonding strength and the electrode has to be extended to the outside. The above disadvantage is especially prominent in making a square diaphragm in line with the ordinarily square glass substrates
201
and
202
, thereby eliminating useless area to increase area utilization efficiency for improving responsivity.
On the other hand, for overcoming the size-increase problem in the sensor chip shown in
FIG. 16
, though the electrode layer
200
is exposed by the cut
206
, the signal receiving portion may be formed on the surface of the first glass substrate
201
as in
FIG. 15
, thereby connecting respective portions by the conductive layer
205
B formed by vapor deposition etc.
However, following disadvantage occur in the above arrangement.
First, since the opening based on which the cut
206
is formed, is desirably formed as small as possible in forming the conductive layer
205
B, it is difficult to conduct vapor deposition to the opening on the wafer, so that sufficient conductive layer
205
B is not formed toward the bottom. Especially, the conductive layer
205
B is likely to be discontinued at a corner of the bottom surface, as shown in FIG.
17
.
Further, a break or a roll is likely to be generated to the edge portion around the opening
207
for the cut
206
previously formed on the first glass substrate
201
. In this case, the aforesaid discontinuation of the conductive layer
205
B is more likely to be caused since the break etc. forms concave when the first glass substrate
201
is laminated to the electrode layer
200
.
In addition, the aforesaid conventional sensor chip has a disadvantage accompanied by anodic bonding electrode as well as the above-described disadvantage of signal receiving portion.
In the conventional sensor chip, a plurality of layers such as glass substrates and silicon substrates are laminated and often bonded by the anodic bonding. The anodic bonding is a bonding technique, in which a high electric voltage is applied to, for example, the fuirt glass substrate
201
and the electrode layer
200
under high temperature to bond them. In some cases, the plurality of layers is collectively anodic-bonded.
For conducting the anodic-bonding, an anodic-bonding electrode
208
is formed on the surface of the first glass substrate
201
in the sensor chip shown in FIG.
15
.
The anodic-bonding is conducted in an area of the thick portion
200
B where the first glass substrate
201
and the electrode layer
200
touches. The anodic-bonding electrode
Kaise Fumio
Sekimori Yukimitsu
Yokoyama Seiichi
Flynn ,Thiel, Boutell & Tanis, P.C.
Nagano Keiki Co. Ltd.
Oen William
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