Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Reexamination Certificate
2000-11-13
2002-08-27
Fourson, George (Department: 2823)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
Reexamination Certificate
active
06441413
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a semiconductor device in which thin film resistors made of bolometer materials are arranged in two-dimensional form corresponding to pixels. The present invention also relates to a trimming method performed in such a semiconductor device and a recording medium in which a program for executing the trimming is recorded.
(2) Description of the Prior Art
Semiconductor devices of this type include a thermal infrared imaging element, an infrared display apparatus, an ultrasonic sensor and the like in which the use of bolometer materials as a thin film resistor constituting part of a pixel or a sensor portion is typically known. For example, such devices include a thermal infrared imaging element which converts incident infrared rays into an electrical signal with a bolometer, an infrared display apparatus which provides a desired infrared image by supplying a bolometer with a predetermined bias voltage (or a bias current) to produce infrared rays (emit light), and the like. A configuration of such a thermal infrared imaging element is hereinafter described specifically as an example of the semiconductor device.
Each of Japanese Patent Laid-open. Publication No.8-105794 and Japanese Patent Laid-open Publication No.9-284651 discloses a thermal infrared imaging element comprising a plurality of thermoelectric converting elements arranged in matrix form which absorb and convert infrared rays radiated by respective portions of an object into heat which is converted into electrical signals for display as images. A pixel portion of the thermal infrared imaging element is shown in a sectional view in FIG.
1
and in a plan view in FIG.
2
.
Referring to
FIGS. 1 and 2
, there is shown semiconductor substrate
20
on which scanning circuit
21
comprising a switch element and a shift register is formed, and silicon oxide film
22
partially including cavity
23
is formed on scanning circuit
21
. A diaphragm (light receiving surface) defined by slit
26
is formed on cavity
23
in silicon oxide film
22
. The diaphragm section has a three-layered configuration in which titanium bolometer
27
, silicon oxide film
28
, and titanium nitride
29
are sequentially stacked on silicon oxide film
22
. On silicon oxide film
22
, ground line
24
, signal line
25
, and vertical select line
30
which are made of aluminum (Al) are also formed. Signal line
25
is a vertical signal line and connected to titanium bolometer
27
. Titanium bolometer
27
, silicon oxide film
28
, and titanium nitride
29
constituting the diaphragm are infrared absorbing layers in which the infrared rays reflected by titanium bolometer
27
is absorbed by titanium nitride
29
. A plurality of scanning circuits
21
and a plurality of the diaphragms are integrated on semiconductor substrate
20
corresponding to pixels such that two-dimensional infrared images can be produced.
In the thermal infrared imaging element, when the infrared rays are incident on the diaphragm from above, the temperature of the diaphragm is changed and the electrical resistance value of titanium bolometer
27
is changed in accordance with the change in the temperature. The change in the resistance value of titanium bolometer
27
is electrically acquired through a read circuit and read to the outside as an infrared image.
FIG. 3
is a circuit diagram of the aforementioned thermal infrared imaging element.
FIG. 4
is a timing chart for describing the operation of the thermal infrared imaging element.
As shown in
FIG. 3
, a pixel comprising bolometer
201
and vertical switch
202
is connected to vertical signal line
203
and further connected to horizontal switch
204
. Four horizontal switches
204
are connected to one read circuit
206
, and an output from each of read circuits
206
are sequentially provided through multiplexers
207
and output buffer
209
to the outside from output terminal
210
. Read circuit
206
can be formed of an integrating circuit, a sample hold circuit, or the like, for example.
In the thermal infrared imaging element, as shown in
FIG. 4
, while an output (for example, V
1
) from vertical shift register
205
is at “H” level, vertical switches
202
connected thereto are turned ON and one of four horizontal switches
204
connected to read circuit
206
is turned ON, thereby selecting a pixel. According to this configuration, one vertical period can be divided into four such that a pixel can be selected for every four pixels in the horizontal direction. The detailed description of the operation is described in Japanese Patent Laid-open Publication No.8-105794 and Japanese Patent Laid-open Publication No.9-284651.
In the aforementioned conventional thermal infrared imaging element shown in FIG.
1
and
FIG. 2
, since titanium bolometer
27
, ground line
24
, and signal line
25
are disposed on the same substrate surface, some of a pixel area is occupied by ground line
24
and signal line
25
, resulting in the problem of reducing the aperture rate (fill factor) for absorbing infrared rays.
Thus, for realizing an increased aperture rate, a thermal infrared imaging element with a three-dimensional structure is proposed in which lines such as a ground line and a signal line electrically connected to a read circuit are embedded in a layer under a diaphragm. An example of a thermal infrared imaging element with such a three-dimensional structure is hereinafter described.
FIG. 5
is a plan view of a pixel in a thermal infrared imaging element with a three-dimensional structure in which lines are embedded in a layer under a diaphragm, and
FIG. 6
is a sectional view taken substantially along the lines X-X′ of FIG.
5
. Diaphragm
4
with air gap
2
disposed in a layer thereunder is supported by two beams
3
on Si substrate
1
provided with a read circuit. Diaphragm
4
comprises SiN insulating protective film
5
, VOx bolometer material thin film
6
formed on protective film
5
, SiN insulating protective film
7
formed on thin film
6
through SiO insulating protective film
8
. Ti wire
11
surrounded by SiN insulating protective films
5
,
7
and another insulating protective film
9
is formed to pass through two beams
3
. Bolometer material thin film
6
within diaphragm
4
is connected to signal line
15
made of Al through Ti contact
12
and wire plug
13
made of tungsten, and signal line
15
is electrically connected to a read circuit within Si substrate
1
. Total reflection film
14
made of Ti is disposed on a portion of a surface of Si substrate
1
provided with a read circuit that faces air gap
2
.
In the thermal infrared imaging element, when infrared rays
10
are incident on diaphragm
4
, the incident infrared rays are absorbed by SiN insulating protective film
5
. Some of the infrared ray which cannot be absorbed by SiN insulating protective film
5
is reflected by total reflection film
14
toward diaphragm
4
, and the reflected infrared rays are again absorbed by SiN insulating protective film
5
. Since the line electrically connected to the read circuit is embedded in a layer under diaphragm
4
, a pixel area is not occupied by the wire to allow an increased aperture rate for absorbing the infrared ray.
When the wire is embedded in the layer under the diaphragm as described above, a contact is typically provided for connecting each wire embedded in the lower layer to the bolometer in the diaphragm portion.
FIG. 7
schematically shows a pixel arrangement and a positional relationship of contacts in a thermal infrared imaging element with wires embedded in a layer under a diaphragm. Ti contact
12
A is a contact connected to a vertical signal line, and Ti contact
12
B is a contact connected to a drain of a vertical switch constituting part of a pixel. In this configuration, the aperture rate can be further increased by reducing the size of each Ti contact and reducing a margin of the interval (interval between Ti contact
12
A and Ti contact
12
B in the lower right pixel) betw
Fourson George
Hutchins, Wheeler & Dittmar
Pham Thanh V
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