Radiant energy – Invisible radiant energy responsive electric signalling – Semiconductor system
Reexamination Certificate
2002-01-03
2003-07-15
Gutierrez, Diego (Department: 2859)
Radiant energy
Invisible radiant energy responsive electric signalling
Semiconductor system
C250S370080
Reexamination Certificate
active
06593577
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an electromagnetic wave detecting device which is capable of detecting electromagnetic waves including radiation such as x-rays, visible light and infrared light.
BACKGROUND OF THE INVENTION
Conventionally, known is a two-dimensional electromagnetic wave detecting device in which (a) a semiconductor film which generates an electric charge (an electron-hole pair) by sensing an electromagnetic wave such as X-ray, that is, an electromagnetic wave conductive semiconductor film, and (b) a semiconductor sensor which is made up of pixel electrodes and other elements are disposed in a two-dimensional manner, and in which a switching element is provided on each of the pixel electrodes. In the electromagnetic wave detecting device, the charge is read out column by column by turning on the switching element row by row.
For example, concrete structures and principles of two-dimensional image detecting device which corresponds to the above electromagnetic wave detecting device are disclosed in “A NEW DIGITAL DETECTOR FOR PROJECTION RADIOGRAFY” (D. L. Lee, et al., SPIE, 2432, pp.237-249, 1995). Referring to
FIG. 9
, the principle of the two-dimentional image detector is described below.
The two-dimensional image detecting device has bias electrodes
102
and a plurality of charge collector electrodes
103
which are respectively on upper and lower layers of a semiconductor film
101
made of Se showing electromagnetic wave conductivity. Each of the charge collector electrodes
103
are respectively connected to charge storage capacitor (having a capacitance of Cs)
104
and an active element (TFT)
105
. Note that, dielectric layers
106
and
107
as electron blocking layers are provided as needed between the semiconductor film
101
and the bias electrode
102
, and between the semiconductor film
101
and charge collector electrode
103
, respectively. In addition,
108
indicates an insulating substrate, and the bias electrode
102
is connected to a high voltage power source
109
.
When an electromagnetic wave, such as an x-ray, is directed to such a two-dimensional image detecting device, a charge (an electron-hole pair) is generated in the semiconductor film
101
. At this stage, the semiconductor film
101
and the charge storage capacitor
104
are serially connected electrically. Therefore, by previously applying a bias voltage to the bias electrode
102
, an electron of the charge (electron-hole pair) generated in the semiconductor film
101
moves to a positive (+) electrode side, and a hole moves to a negative (−) electrode side, thereby storing the charge in the charge storage capacitor
104
.
By turning on the active element
105
, the charge stored in the charge storage capacitor
104
can be taken outside. By (a) thus disposing the charge collector electrode
103
, the charge storage capacitor
104
and the active element
105
in a two-dimensional manner, and (b) reading out charges in a line-sequential manner, it becomes possible to obtain two-dimensional information of an electromagnetic wave which is a detection target.
Generally, Se, CdTe, CdZnTe, PbI
2
, HgI
2
, SiGe, Si, etc. are used as the semiconductor film
101
which has electromagnetic wave conductivity. Among them, an Se film has a small dark current (a leak current) characteristic and is capable of large-area deposition at a low temperature by vacuum evaporation. For those reasons, the Se film is widely used for the electromagnetic wave detecting device (particularly x-ray detecting device) having a structure in which a semiconductor film
101
is formed directly on an active matrix substrate
110
(see FIG.
9
).
As shown in FIG.
10
(
a
) and FIG.
10
(
b
), the two-dimensional electromagnetic wave detecting device using the above-described active matrix substrate
110
has a structure where a driving signal (scanning signal) for driving the active element
105
in a line-sequential manner is inputted from the circumference of the active matrix substrate
110
, and each pixel, that is, charges stored in the charge storage capacitor
104
are outputted outside in response to the detection of x-ray (electromagnetic wave). Note that, reference numeral
116
indicates a projection region which is pixel electrode alignment region, shown by a thick line in FIG.
10
(
b
).
The active matrix substrate
110
has scanning lines and readout lines in a lattice manner (usually, matrix of 500×500−3000×3000 pixels). These scanning line and readout line are connected respectively to a signal input terminal
111
and a signal output terminal
112
which are formed in the circumference of the active matrix substrate
110
. On the active matrix substrate
110
shown in FIG.
10
(
a
) and FIG.
10
(
b
), the signal input terminals
111
connected to the scanning line are formed along first two sides facing each other (left and right sides), and the signal output terminals
112
connected to the readout line are formed along second two sides facing each other (upper and lower sides).
Further, a gate driver
113
(a driving LSI) is connected to the signal input terminal
111
by a mounting method such as TAB or COG and a readout amplifier
114
which is made up of LSI is connected to the signal output terminal
112
by the same method.
The signal input terminals
111
and the signal output terminals
112
are arranged so as to divide one side into plural divisions corresponding to a plurality of gate drivers
113
(for example, TAB) and readout amplifiers
114
(for example, TAB) connected thereto. For example, in case where TABs for the readout amplifier
114
having 128-channel input terminals are connected with respect to the active matrix substrate
110
having 1536×1536 matrix, twelve TABs per one side are allocated along each side of active matrix substrate
110
. Accordingly, it is designed to arrange signal output terminals
112
of the active matrix substrate
110
so as to divide one side into twelve divisions. Further, arrangement of the signal input terminals
111
and the signal output terminals
112
is substantially symmetrical with respect to the center Vo in the vertical direction and the center Ho in the horizontal direction, respectively. Note that, for purpose of explanation,
FIG. 10
(
a
) shows an example that the signal input terminals
111
and the signal output terminals
112
are arranged at four divisions and seven divisions, respectively. In addition, the vertical direction and the horizontal direction are established for purpose of explanation; for example, the directions can be established conversely.
On the other hand, a voltage is applied to the bias electrode
102
from an external power source, that is, a high voltage power source shown in
FIG. 9 through a
bias supply line
115
. Thus, the bias supply line
115
is connected to a connecting section
102
a
of the bias electrode
102
. For limitation of space, the connecting section
102
a
of the bias electrode
102
is provided in the vicinity of the signal input terminal
111
and the signal output terminal
112
.
Incidentally, with respect to the electromagnetic wave detecting device, a high voltage applied to the bias electrode
102
makes it effective to improve the sensitivity for detection of x-ray. Thus, if a-Se film which is capable to form a film easily, for example, is used as a semiconductor film
101
which has electromagnetic wave conductivity, nearly 5000V-15000V of a high voltage can be applied to the bias electrode
102
.
However, with respect to the active matrix substrate
110
, as described above, in case where the connecting section
102
a,
to which the bias supply line
115
is connected, of the bias electrode
102
is arranged in the vicinity of the signal input terminal
111
and the signal output terminal
112
, application of a high voltage to the bias electrode
102
causes generation of an electrical discharge such as atmospheric discharges and surface creepage between the connecting section
102
a
and the signal input te
Guadalupe Yaritza
Gutierrez Diego
Nixon & Vanderhye P.C.
Sharp Kabushiki Kaisha
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