X-ray or gamma ray systems or devices – Electronic circuit – With display or signaling
Reexamination Certificate
1999-07-28
2001-12-18
Kim, Robert H. (Department: 2882)
X-ray or gamma ray systems or devices
Electronic circuit
With display or signaling
C378S041000, C250S21400C, C427S567000
Reexamination Certificate
active
06332016
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a photoelectric conversion device, a method of manufacturing the device, and an X-ray imaging system including the device. More particularly, it relates to a photoelectric conversion device wherein a plurality of sensor cells, in each of which a photoelectric element and a switching element are connected, are arrayed in two dimensions on a substrate, a method of manufacturing the device, and an X-ray imaging system including the device.
Also, the present invention is well suited for applications to a photoelectric conversion device which has photoelectric elements arrayed in two dimensions for actual-size reading in, for example, a facsimile equipment, a digital copier or an X-ray imaging apparatus, and to a method of repairing the photoelectric conversion device.
Further, the present invention pertains to an X-ray imaging system in which the above photoelectric conversion device having the photoelectric elements of two-dimensional arrayal is assembled.
2. Related Background Art
Heretofore, a reading system which is configured of a scaling-down optical system and a CCD (charge-coupled device) type sensor has been employed as the reading system of a facsimile equipment, a digital copier, an X-ray imaging apparatus or the like. In recent years, however, photoelectric semiconductor materials typified by hydrogenated amorphous silicon (hereinbelow, expressed as “a-Si”) have been being developed. This has resulted in the remarkable developments of so-called “close contact type sensors” in each of which photoelectric elements and a signal processing portion are formed on a substrate of large area so as to adopt an optical system for the actual-size reading of an information source.
In particular, the a-Si is usable, not only as the photoelectric material, but also as the material of thin-film field effect transistors (hereinbelow, simply expressed as “transistors”). Accordingly, it has the advantage that a semiconductor layer for photoelectric conversion and a semiconductor layer for the transistors can be formed at the same time.
An example of a photoelectric conversion device utilizing such a-Si is disclosed in the official gazette of Japanese Patent Application Laid-open No. 8-116044. It will now be explained with reference to FIG.
1
and
FIGS. 2A and 2B
of the accompanying drawings.
FIG. 1
is a circuit diagram showing the whole circuit of the photoelectric conversion device. Besides,
FIG. 2A
is a schematic plan view of constituent elements which correspond to one sensor cell of the photoelectric conversion device. Further,
FIG. 2B
is a schematic sectional view taken along line
2
B—
2
B indicated in FIG.
2
A.
First, the construction of the photoelectric conversion device will be explained. Referring to
FIG. 1
, each sensor cell is configured of a photoelectric element S, a capacitor C and a transistor T. In the photoelectric conversion device, the sensor cells totaling nine (3×3) are divided into three blocks of respective columns. That is, one block consists of three sensor cells.
In the figure, symbols S
11
to S
33
denote the photoelectric elements S. The lower electrode side of each photoelectric element S is indicated by letter G, while the upper electrode side thereof is indicated by letter D. In addition, symbols C
11
to C
33
denote the capacitors for storage, and symbols T
11
to T
33
the transistors for transferring data.
Besides, symbol Vs designates a power source (or supply voltage) for reading out a converted charge signal, and symbol Vg a power source (or supply voltage) for refreshment. These power sources Vs and Vg are respectively connected to the G electrodes of all the photoelectric elements S
11
to S
33
through a switch SWs and a switch SWg. The switch SWs is connected to a refreshment control circuit RF through an inverter, while the switch SWg is connected thereto directly. The switch SWg is controlled so as to turn “ON” during a refreshing time period.
Further, a part enclosed with a broken line in
FIG. 1
is formed on an identical insulated substrate of large area. In the enclosed part, the sensor cell having the photoelectric element S
11
is illustrated as the plan view in FIG.
2
A. Also, a plane along the dot-and-dash line
2
B—
2
B indicated in
FIG. 2A
is illustrated as the sectional view in FIG.
2
B.
Referring to
FIG. 2B
, the sensor cell generally shown in
FIG. 2A
includes a lower electrode
1
which forms a gate electrode on the insulating substrate, a gate insulator film
2
, an i-layer
3
which is a semiconductor layer effecting photoelectric conversion, an n-layer
4
which hinders the injection of holes, and an upper electrode layer
5
which forms source and drain electrodes. This sensor cell is fabricated in such a way that the lower electrode layer
1
, the gate insulator film
2
, the i-layer
3
, the n-layer
4
, and the upper electrode layer
5
serving as the source and drain electrodes are first stacked in the order mentioned, that the upper electrode layer
5
is subsequently etched to form the source and drain electrodes, and that the n-layer
4
is thereafter etched to form a channel portion.
In the above photoelectric conversion device, the capacitor C
11
and the photoelectric element S
11
are disposed without special isolation. This is because the photoelectric element S
11
and the capacitor C
11
are configured of the same layers. Such a configuration is also the feature of the photoelectric conversion device. Besides, the capacitor C
11
is formed while keeping the areas of the electrodes of the photoelectric element S
11
large. The reason therefor is that, when the areas of the electrodes of the photoelectric element S
11
are enlarged, the sensitivity of the sensor is enhanced, leading to decrease in the quantity of exposure to X-rays as is required for the photoelectric conversion device of, for example, the X-ray imaging apparatus.
In addition, a silicon nitride (SiN) film for passivation and a phosphor layer of cesium iodide (CsI) or the like are formed at the upper part of the sensor cell. When X-rays are caused to fall on the sensor cell, they are converted by the phosphor layer CsI into light or visible radiation (indicated by arrows of broken lines), which enters the photoelectric element S
11
.
Next, an example of the operation of the photoelectric conversion device will be explained. Referring also to
FIG. 1
, the output of the charge signal converted in each photoelectric element S is stored in the storage capacitor C. The stored signal is fetched on a signal wiring line SIG when the transistor T is turned “ON” by an output signal from a shift register SR
1
. The fetched charge signal is inputted to a detecting integrated circuit IC when a switch M is turned “ON” by a control signal delivered from a shift register SR
2
.
More concretely, electric signals outputted from the sensor cells of one block are simultaneously fetched on one signal wiring line SIG, and they are collectively transferred to the detecting integrated circuit IC by the shift register SR
2
. Each of the electric signals transferred to the detecting integrated circuit IC is amplified into an output voltage Vout by an amplifier Amp.
The operation of the photoelectric conversion device will now be detailed with reference to a timing chart illustrated in FIG.
3
. First of all, a high level voltage Hi is applied to control wiring lines g
1
to g
3
and s
1
to s
3
by the shift registers SR
1
and SR
2
, respectively. Then, the transistors T
11
to T
33
and the switches M
1
to M
3
are turned “ON” owing to the high level outputs Hi of the shift register SR
2
. Thus, the electrodes D of all the photoelectric elements S
11
to S
33
become a ground (GND) potential. This is because the input terminal of the integrating detector Amp is designed so as to have the GND potential.
A high level voltage Hi is outputted from the refreshment control circuit RF, thereby to turn “ON” the switch SWg. Thus, the electrodes G of all the photoelect
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Hobden Pamela R.
Kim Robert H.
LandOfFree
Photoelectric conversion device, manufacturing method... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Photoelectric conversion device, manufacturing method..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Photoelectric conversion device, manufacturing method... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2581674