JP2002094040A - Two-dimensional image reading device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a two-dimensional image reading device where an erroneous reading operation and the damage to a device are significantly suppressed by appropriately discharging the static electricity charge at an object to be detected, which is placed on a photosensor device. SOLUTION: There are provided a photosensor array 100, comprising a plurality of double gate photosensors 10 arrayed in a matrix form, a top gate driver 110 and a bottom gate driver 120 connected, respectively, to a top gate line 101 and a bottom gate line 102 which connect the double gate photosensors 10 in the row direction, and a driver 130 connected to a drain line 103, which connects the double gate photosensors 10 in the columnar direction. The electrostatic withstand voltage of the driver (bottom gate driver 120) connected to the conductive layer (bottom gate line 102) where a current is easy to concentrate under discharge of a static charge is set high.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-dimensional image reading apparatus, and more particularly, to a method of reading an image pattern by bringing a subject into contact with a photosensor array in which a plurality of photosensors are arranged in a matrix. The present invention relates to a three-dimensional image reading device.

[0002]

2. Description of the Related Art Conventionally, as a two-dimensional image reading device for reading the shape of fine irregularities such as a printed matter, a photograph, or a fingerprint, a photo-sensor constructed by arranging photoelectric conversion elements (photo sensors) in a matrix. The object to be detected is placed on and brought into contact with the detection surface provided on the sensor array, and the object to be detected 2
There is a structure that reads a two-dimensional image. In a two-dimensional image reading apparatus having a structure in which the detection target directly contacts the detection surface, various methods have been considered in order to suppress malfunction or damage due to static electricity or the like charged on the detection target. .

For example, Japanese Unexamined Patent Publication No. 11-259638 discloses a surface light source 2 as shown in FIGS.
01, and a plurality of photosensors 20
A fingerprint reader in which a transparent conductive layer 203 is formed on a photosensor device 202 in which 2a are arranged in a matrix is described. In such a fingerprint reader, the upper surface (detector contact surface) 203a of the transparent conductive layer 203 is provided.
The surface light source 2 is applied to the finger (detected body) 210
By irradiating light Lp from 01, the light Lp is reflected in accordance with the concave and convex pattern of the fingerprint, and based on the reflected light Lr incident on the photosensor 202a, light and dark information is detected to generate a fingerprint image. .

Here, the transparent conductive layer 203 is made of ITO (In
formed of a transparent conductive material such as dium Tin Oxide (indium tin oxide);
Is formed in a thin film shape over the entire upper surface or with a predetermined shape pattern. Such a transparent conductive layer 203
Plays a role of the finger 210 contacting the detection object contact surface 203a.
Fingerprint reader (two-dimensional image reader) by discharging static electricity charged to
Erroneous reading and damage of the photo sensor device 202 are prevented.

[0005]

However, in the conventional two-dimensional image reading apparatus as described above, there is a case where it is not possible to sufficiently and surely discharge the static electricity charged on the object to be detected. There has been a problem that a reading malfunction or breakage of the three-dimensional image reading device cannot be reliably prevented.

Specifically, for example, when a two-dimensional image reader is applied to a fingerprint reader, a voltage (charged voltage) due to static electricity charged on a finger (human body) to be detected is generally 10 kV or less (generally about 10 kV). (Approximately several kV), the withstand voltage of the transparent conductive layer and the photosensor device as described above is set. On the other hand, the charged voltage of the human body largely depends on the season, weather conditions, constitution, clothing, and the like. For example, on a dry sunny day in winter, the charged voltage may exceed 10 kV. In this case, static electricity is not removed (discharged) satisfactorily by the transparent conductive layer, and a current flowing through each wiring configuring the photosensor device is concentrated on a specific wiring due to a change in potential of the transparent conductive layer. There is a possibility that the driver connected to the wiring may be destroyed or malfunction.

In view of the above-mentioned problems, the present invention appropriately discharges static electricity charged on an object to be detected mounted on a photosensor device, and largely suppresses a reading malfunction and device damage. It is an object of the present invention to provide a two-dimensional image reading apparatus capable of performing the above-mentioned.

[0008]

According to a first aspect of the present invention, there is provided a two-dimensional image reading apparatus comprising: a photosensor array configured by arranging a plurality of photosensors; and a plurality of driving circuits for driving the photosensors. A two-dimensional image reading device for reading an image pattern of a detection target placed on the photosensor array, wherein the plurality of driving circuits detect the detection target in accordance with a wiring resistance of each signal path connected thereto. It is characterized in that resistance to static electricity charged on the body is set.

That is, among the signal paths connecting the photosensor array and the plurality of drive circuits, the circuit connected to the signal path having a low wiring resistance is designed to have a high withstand voltage against static electricity charged on the object to be detected. Constitute. Specifically, for example, among the plurality of drive circuits, a transistor configuring the wiring resistance of each connected signal path is the lowest,
The breakdown voltage is set to be the highest and the channel resistance is set to be the lowest.

In other words, by setting the withstand voltage of the transistor constituting the one having the lowest wiring resistance among the connected signal paths of the plurality of drive circuits to the highest, the static electricity charged on the detection target can be reduced. During the discharging operation, even if the current concentrates on the signal path with low wiring resistance and the large current flows, the withstand voltage of the drive circuit connected to the signal path is set high, so that the drive circuit may be damaged or damaged. Malfunction can be suppressed, and the off-resistance of the transistor is reduced so that the channel resistance of the transistor constituting the signal line having the lowest wiring resistance is minimized. Since the pressure can be reduced, the voltage due to static electricity can be more evenly dispersed, and breakage and malfunction of the drive circuit can be significantly suppressed.

According to a sixth aspect of the present invention, there is provided a two-dimensional image reading apparatus, comprising: a photosensor array configured by arranging a plurality of photosensors; and a plurality of drive circuits for driving the photosensors. In a two-dimensional image reading apparatus for reading an image pattern of a detection object mounted thereon, the plurality of drive circuits are set so as to make wiring resistance of each signal path connected thereto substantially uniform. And

That is, among the signal paths connecting the photosensor array and the plurality of drive circuits, for example, the wiring resistance of the signal path having a relatively low wiring resistance is increased to increase the wiring resistance of the other signal paths. The wiring resistance balance is set so as to be substantially uniform. Specifically, for example, the wiring resistance of each signal path is set to be balanced by arbitrarily controlling the film thickness and width, the film forming conditions, or the material and the like of the wiring configuring the signal path. . Accordingly, at the time of the discharging operation of the static electricity charged on the detection target, the current does not concentrate on the signal path having the low wiring resistance and is dispersed in each signal path, so that a large current flows to a specific driver or circuit. Damage and malfunction can be suppressed.

Here, the photosensor comprises a source electrode and a drain electrode formed with a semiconductor layer that generates carriers when excitation light is incident, and an insulating film at least above and below the channel region. A first gate electrode (top gate electrode) and a second gate electrode (bottom gate electrode) formed through the so-called double gate transistor,
The first gate electrodes are connected to a first driver, and the second
May be connected to the second driver and the drain electrodes are connected to an output circuit.

Therefore, even if the first gate electrode and the first gate line connecting the first gate electrode and the first driver are made of a transparent material having a high resistivity, the wiring connected to other circuits can be formed. , The wiring resistance can be made uniform, so that the electric charge due to the static electricity does not concentrate on a specific circuit, and destruction and malfunction can be suppressed. As a result, the photo sensor can be made significantly thinner, and the fingerprint sensor can be downsized.
The density of the detection pixels can be increased, and the two-dimensional image reading apparatus excellent in the electrostatic withstand voltage as described above can be realized.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a two-dimensional image reading apparatus according to the present invention will be described in detail. First,
The configuration of a good photosensor applied to the two-dimensional image reading apparatus according to the present invention will be described. The photo sensor applied to the two-dimensional image reading device according to the present invention includes CC
A solid-state imaging device such as D (Charge Coupled Device) can be used.

As is well known, a CCD is a single crystal silicon integrated circuit, a photodiode, a thin film transistor (TF), or the like.
T: Thin Film Transistor) and other photosensors are arranged in a matrix, and the amount (charge amount) of electron-hole pairs generated corresponding to the amount of light applied to the light receiving portion of each photosensor is determined. , A horizontal scanning circuit and a vertical scanning circuit to detect the luminance of irradiation light. by the way,
In a photosensor system using such a CCD, it is necessary to separately provide a selection transistor for setting each of the scanned photosensors to a selected state, so that the system itself becomes larger as the number of detected pixels increases. Have the problem of

Therefore, in recent years, as a configuration for solving such a problem, a thin film transistor having a so-called double gate structure (hereinafter, referred to as a “double gate”) in which a photo sensor itself has a photo sensing function and a selection transistor function. Type transistors) have been developed, and attempts have been made to reduce the size of the system and increase the density of pixels. Therefore, the double-gate transistor can also be favorably applied to the two-dimensional image reading device of the present invention.

Here, a photo sensor (hereinafter, referred to as a "double gate photo sensor") using a double gate transistor applied to the two-dimensional image reading apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram showing the basic structure of a double-gate photosensor.

As shown in FIGS. 1A and 1B, a double-gate type photosensor 10 is made of amorphous silicon in which electron-hole pairs are generated when excitation light (here, visible light) is incident. Semiconductor layers (channel layers) 11, etc., impurity layers 17, 18 made of n ⁺ silicon provided at both ends of the semiconductor layer 11, and chromium, chromium alloy, aluminum, Drain electrode 12 opaque to visible light selected from aluminum alloy or the like
And a transparent conductive layer such as ITO formed above the semiconductor layer 11 (above the drawing) via the block insulating film 14 and the upper (top) gate insulating film 15 and transmit visible light. Gate electrode 2 exhibiting properties
And a bottom gate electrode 22 opaque to visible light, such as chromium, a chromium alloy, aluminum, or an aluminum alloy, formed below the semiconductor layer 11 (below the drawing) via the lower (bottom) gate insulating film 16. , Is configured.
The double-gate photosensor 10 having such a configuration is formed on a transparent insulating substrate 19 such as a glass substrate. In FIG. 1A, 101 is a top gate line, 102 is a bottom gate line, 103
Is a drain line, and 104 is a source line.

Here, the top gate insulating film 15, the block insulating film 14, the bottom gate insulating film 16, and the protective insulating film 20 provided on the top gate electrode 21 shown in FIG. An insulating material having a high transmittance to visible light for exciting the layer 11, for example, silicon nitride, silicon oxide, or the like, and a ground electrode layer 30 for static electricity removal provided on the protective insulating film 20.
Is made of a material having a high transmittance to visible light that excites the semiconductor layer 11, for example, ITO, so that only the light hv (arrow) from above in the drawing is the semiconductor layer 1.
1 is provided.

Next, a photosensor system including a photosensor array (photosensor device) configured by two-dimensionally arranging the above-described double-gate photosensors will be briefly described with reference to the drawings. FIG.
1 is a schematic configuration diagram of a photosensor system including a photosensor array configured by two-dimensionally arranging double-gate photosensors. In the drawing, reference numeral 10 denotes an equivalent circuit of the above-described double gate photosensor, in which TG indicates a top gate terminal, BG indicates a bottom gate terminal, S indicates a source terminal, and D indicates a drain terminal.

As shown in FIG. 2, the photo sensor system is roughly divided into a large number of double gate type photo sensors 10.
Are arranged in a matrix of, for example, n rows × m columns, and a top gate terminal TG (top gate electrode 2) of each double gate type photo sensor 10.
1) and the bottom gate terminal BG (bottom gate electrode 2)
2) are connected in the row direction to extend the top gate line 101 and the bottom gate line 102, and the drain line (data line) in which the drain terminal D (drain electrode 12) of each double gate type photosensor 10 is connected in the column direction. ) 103 and a (common line) source line 104 in which source terminals S (source electrodes 13) are connected in the column direction.
, A top gate driver (first driver) 110 connected to the top gate line 101, and a bottom gate driver (second driver) connected to the bottom gate line 102.
120), a column switch 131 connected to the drain line 103, and a precharge switch 13
And a drain driver (output circuit) 130 composed of an amplifier 133.

Here, as shown in FIG. 1, the top gate line 101 is
The bottom gate line 102, the drain line 103, and the source line 104 are integrally formed of a transparent conductive layer such as TO, and the same material as the bottom gate electrode 22, the drain electrode 12, and the source electrode 13 is opaque to excitation light. It is formed integrally. Also, the source line 10
4, a constant voltage Vss set according to a precharge voltage described later is applied, but may be a ground potential.

In FIG. 2, φtg is a control signal for generating signals φT1, φT2,... ΦTi,... ΦTn selectively output as either the reset voltage or the optical carrier accumulation voltage. Is a control signal for generating signals φB1, φB2,... ΦBi,... ΦBn selectively output as either the read voltage or the non-read voltage, and φpg controls the timing of applying the precharge voltage Vpg. This is a precharge signal.

In such a configuration, from the top gate driver 110 through the top gate line 101,
A signal φTi (i = 1, 2,...) Is applied to the top gate terminal TG.
By applying n), the photo sensing function is realized, and the signal φB is applied from the bottom gate driver 120 to the bottom gate terminal BG via the bottom gate line 102.
i (i = 1, 2,..., n), the detection signal is taken into the drain driver 130 via the drain line 103, and output as serial data or parallel data (Vout), thereby providing a selective reading function. Is realized.

Next, a drive control method of the above-described photo sensor system will be described with reference to the drawings. FIG.
FIG. 4 is a timing chart illustrating an example of a drive control method of the photosensor system. FIG. 4 is a conceptual diagram of the operation of the double-gate photosensor, and FIG. FIG. Here, the configuration of the above-described double-gate photosensor and photosensor system (FIGS. 1 and 2) will be described with reference to the configuration as appropriate.

First, in the reset operation, as shown in FIGS. 3 and 4A, a pulse voltage (reset pulse; for example, Vtg =
+15 V (high level) φTi is applied, and carriers (here, holes) accumulated near the semiconductor layer 11 of each double-gate photosensor 10 and the interface with the semiconductor layer 11 in the block insulating film 14 are applied. (Reset period Treset).

Next, in the light accumulation operation, as shown in FIGS. 3 and 4B, a low level (for example, Vtg = −15 V) bias voltage φT is applied to the top gate line 101.
By applying i, the reset operation ends, and the light accumulation period Ta due to the carrier accumulation operation starts. In the light accumulation period Ta, an incident effective area of the semiconductor layer 11, that is, an electron-hole pair generated in the carrier generation area is generated according to the amount of light incident from the top gate electrode side, and the semiconductor layer 11 and Holes are accumulated near the interface between the block insulating film 14 and the semiconductor layer 11, that is, around the channel region.

In the precharge operation, as shown in FIGS. 3 and 4C, in parallel with the light accumulation period Ta, the drain line 1 is controlled based on the precharge signal φpg.
03, a predetermined voltage (precharge voltage) Vpg is applied,
The charge is held in the drain electrode 12 (precharge period Tprch). Next, in the read operation, FIG.
As shown in FIG. 4D, after a precharge period Tprch has elapsed, a high-level (for example, Vbg = + 10 V) bias voltage (read selection signal; hereinafter, referred to as a read pulse) φBi is applied to the bottom gate line 102. As a result, the double-gate photosensor 10 is turned on (readout period Tread).

Here, in the reading period Tread,
Carriers (holes) accumulated in the channel region act in a direction to reduce Vtg (−15 V) applied to the top gate terminal TG having the opposite polarity, so that Vbg of the bottom gate terminal BG is reduced.
As a result, an n-channel is formed, and the drain line voltage VD of the drain line 103 changes according to the drain current as shown in FIG.
As shown in (a), it tends to gradually decrease from the precharge voltage Vpg over time.

That is, when the light accumulation state in the light accumulation period Ta is a dark state and no carriers (holes) are accumulated in the channel region, as shown in FIGS. 4 (e) and 5 (a). By applying a negative bias to the top gate terminal TG, the positive bias of the bottom gate terminal BG is canceled and the double gate type photosensor 10 is turned off, and the drain voltage, that is, the drain line 1
The voltage VD of 03 is maintained almost as it is.

On the other hand, when the light accumulation state is a bright state, as shown in FIGS. 4D and 5A, carriers (holes) corresponding to the amount of incident light are captured in the channel region. Therefore, it acts to cancel the negative bias of the top gate terminal TG, and the bottom gate terminal B
Due to the positive bias of G, the double gate photosensor 10 is turned on. Then, the voltage VD of the drain line 103 is determined according to the ON resistance according to the amount of incident light.
Will decrease.

Therefore, as shown in FIG.
The tendency of the change in the voltage VD of the drain line 103 depends on the time from the end of the reset operation by the application of the reset pulse φTi to the top gate terminal TG to the application of the read pulse φBi to the bottom gate terminal BG (the light accumulation period Ta). ) Is closely related to the amount of light received, and tends to decrease slowly when the accumulated carrier is small,
When the amount of accumulated carriers is large, the carrier tends to decrease sharply. Therefore, by detecting the voltage VD of the drain line 103 after a predetermined time has elapsed after the start of the read period Tread, or by detecting a time required to reach the voltage based on a predetermined threshold voltage. By doing so, the amount of irradiation light is converted.

The above-described series of image reading operations is regarded as one cycle, and the same processing procedure is repeated for the double-gate photosensor 10 in the (i + 1) -th row, thereby making the double-gate photosensor 10 a two-dimensional sensor system. Can work. In the timing chart shown in FIG. 3, the precharge period Tprch
After a lapse of time, as shown in FIGS. 4F and 4G, when the state where a low level (for example, Vbg = 0 V) is applied to the bottom gate line 102 is continued, the double gate type photosensor 10 keeps the OFF state. Then, as shown in FIG. 5B, the voltage VD of the drain line 103 holds the precharge voltage Vpg. As described above, the selection function of selecting the read state of the double-gate photosensor 10 is realized by the voltage application state to the bottom gate line 102.

FIG. 6 is a sectional view of a main part of a two-dimensional image reading apparatus (fingerprint reading apparatus) to which the above-described photo sensor system is applied. Here, for the sake of explanation and illustration, hatching indicating a cross-sectional portion of the photosensor system is omitted. As shown in FIG. 6, in an image reading apparatus that reads a two-dimensional image such as a fingerprint, a glass substrate (insulating substrate) on which a double-gate photosensor 10 is formed.
Irradiation light La is made incident from a backlight (surface light source) 40 provided on the lower side of the double-gate photosensor 10 (specifically, the bottom gate electrode 2).
2. Except for the regions where the drain electrode 12 and the source electrode 13) are formed, the transparent insulating substrate 19 and the insulating films 15, 16, 20
And the detection surface 30a on the transparent earth electrode layer 30
Is irradiated on the finger (detected body) 50 placed on the.

When a fingerprint is detected by the fingerprint reader, the translucent layer of the skin surface 51 of the finger 50 contacts the transparent layer (the ground electrode layer 30) formed on the uppermost layer of the photosensor array 100. By doing so, there is no air layer having a low refractive index at the interface between the ground electrode layer 30 and the skin surface layer 51. Here, since the thickness of the skin surface layer 51 is thicker than the upper limit of visible light (about 800 nm), the visible light La incident inside the convex portion 52a of the fingerprint 52 propagates while scattering and reflecting inside the skin surface layer 51. I do. Part of the transmitted visible light Lb passes through the transparent ground electrode layer 30, the transparent insulating films 20, 15, and 14, and the top gate electrode 21, and the semiconductor layer 11 of the double gate photosensor 10
As excitation light.

As described above, carriers (holes) generated by the incidence of light on the semiconductor layer 11 of the double-gate type photosensor 10 arranged at the position corresponding to the convex portion 52a of the finger 50 are accumulated. Accordingly, the image pattern of the finger 50 can be read as light / dark information according to the above-described series of drive control methods. The concave portion 52 of the fingerprint 52
b, the irradiated light La is applied to the ground electrode layer 30.
Passes through the interface between the detection surface 30a and the air layer, reaches the finger at the tip of the air layer, and is scattered in the skin surface layer 51.
Since the skin surface layer No. 0 has a higher refractive index than air, the light Lc in the skin surface layer 51 incident on the interface at a certain angle hardly escapes to the air layer and is arranged at a position corresponding to the concave portion 52b. 10 is suppressed from entering the semiconductor layer 11.

<First Embodiment> Next, a specific embodiment of the two-dimensional image reading apparatus according to the present invention will be described. FIG. 7 shows a first example of the two-dimensional image reading apparatus according to the present invention.
FIG. 8 is a schematic configuration diagram showing the overall configuration of the embodiment of FIG.
Is the row direction (x) of the two-dimensional image reading apparatus according to the present embodiment.
FIG. 9 is a schematic cross-sectional view illustrating a configuration in the column direction (y direction) of the two-dimensional image reading apparatus according to the present embodiment. FIG. 10 is an equivalent circuit diagram corresponding to each configuration of the two-dimensional image reading apparatus according to the present embodiment. Note that FIG. 9 shows a cross-sectional structure of the configuration of the double-gate photosensor 10 viewed in the row direction for convenience of description. Here, the same components as those described above (FIGS. 1 and 6) are denoted by the same reference numerals, and description thereof will be simplified or omitted.

As shown in FIGS. 7 to 9, the photosensor array 100 applied to the two-dimensional image reading apparatus according to the present embodiment includes a plurality of double-gate photosensors 10 having the above-described configuration. Substrate (glass substrate) 19
An array region A, which is formed to be arranged in a matrix and has at least the double-gate photosensor 10 disposed thereon
An earth electrode layer 30 made of a transparent conductive material is provided on the light-transmitting protective insulating film 20 that is laminated so as to cover the entire region of a.

Further, similarly to the photo sensor system shown in FIG. 2, the top gate electrode 2 of a plurality of double gate type photo sensors 10 constituting the photo sensor array 100 is formed.
The first gate electrode 22 and the bottom gate electrode 22 are connected in the row direction (x direction) by a top gate line 101 and a bottom gate line 102, respectively.
And a bottom gate pad portion Pb, and is connected to the top gate driver 110 and the bottom gate driver 120. Further, the drain electrodes 12 of the plurality of double gate photosensors 10 are connected in the column direction (y direction) by the drain line 103, and the drain pad portion Pd
Is connected to the drain driver 130 via the.
The source electrodes 13 of the plurality of double-gate photosensors 10 are connected in the column direction (y direction) by source lines 104, and are supplied with a constant potential Vss via the source pad Ps. Although not shown, on the back side (the lower side in the drawing) of the photosensor array 100,
The upper surface side of the photo sensor array 100 (the ground electrode layer 30
A surface light source (surface light source 40 in FIG. 6) that irradiates a finger (detected body) 50 that is in contact with the upper surface of the light source (detected object) 50 with uniform light is disposed.

Here, as shown in FIG. 8, the top gate pad portion Pt is formed on the base pad 21 formed integrally with the top gate electrode 21 and the top gate line 101.
a and a top pad electrode layer 21b formed simultaneously with the ground electrode layer 30 formed on the protective insulating film 20, for example.
And a top gate driver 110 is electrically connected to the top gate pad portion Pt via, for example, a bump Bt. That is, the top gate pad portion Pt is
1 and a high-resistance transparent conductive layer such as ITO constituting the ground electrode layer 30.

The bottom gate pad portion Pb is formed as shown in FIG.
As shown in FIG. 3, a base pad 22a formed integrally with the bottom gate electrode 22 and the bottom gate line 102.
For example, a first bottom pad electrode layer 22b formed simultaneously with the drain electrode 12 and the source electrode 13,
For example, the second gate formed simultaneously with the top gate electrode 29
Of the bottom pad electrode layer 22c and, for example, the protective insulating film 2
And a 23rd bottom pad electrode layer 22d formed at the same time as the ground electrode layer 30 formed on the bottom gate pad portion Pb. The gate driver 120 is electrically connected. That is, the bottom gate pad portion Pb is provided with the bottom gate electrode 22 and the drain electrode 12.
And a low-resistance metal conductive layer such as chromium constituting the source electrode 13, the top gate electrode 21 and the ground electrode layer 30.
And a high-resistance transparent conductive layer such as ITO.

Further, as shown in FIG. 9, the drain pad portion Pd includes the drain electrode 12 and the drain line 103.
The first drain pad electrode layer 12b formed simultaneously with the top gate electrode 29, for example, on the base pad 12a integrally formed with the
It has a configuration in which a second drain pad electrode layer 12c formed simultaneously with the earth electrode layer 30 formed thereon is laminated. Then, the drain gate pad portion Pd
For example, the drain driver 130 is electrically connected via the bump Bd.

Further, as shown in FIG. 9, the source pad portion Ps is formed on the base pad 13a formed integrally with the source electrode 13 and the source line 104, for example, at the same time as the top gate electrode 21. One source pad electrode layer 13b and, for example, a second source pad electrode layer 13c formed simultaneously with the ground electrode layer 30 formed on the protective insulating film 20 are stacked. Then, for this source gate pad portion Ps,
For example, the constant potential Vss is connected via a wiring layer not shown.

That is, the drain pad portion Pd and the source pad portion Ps are connected to the drain electrode 12 and the source electrode 1.
3 and a low-resistance metal conductive layer such as chromium, and ITO forming the top gate electrode 21 and the ground electrode layer 30.
And the like. Note that, in the present embodiment, each pad portion has a configuration in which electrode layers formed simultaneously during the manufacturing process of another conductive layer are stacked, but the present invention is not limited to this. Alternatively, each pad may be formed using a single conductive material by a separate manufacturing process.

The configuration described above is similar to that of FIG.
0 can be represented by an equivalent circuit. That is,
As shown in FIG. 10, a wiring (not shown) for connecting to the ground electrode layer 30 and the ground potential includes a wiring resistance R30 based on a high-resistance conductive material such as ITO. A wiring capacitance C1 is formed between the first gate electrode 21 and the top gate line 101. The signal path including the top gate electrode 21, the top gate line 101, and the top gate pad portion Pt is based on a high resistivity conductive material such as ITO, a wiring length, and a high sheet resistance depending on a wiring cross-sectional area. Wiring resistance R1
01 is present, a wiring capacitance C2 is formed between the top gate line 101 and the drain line 103,
A wiring capacitance C3 is formed between the top gate line 101 and the source line 104.

The signal path including the drain electrode 12, the drain line 103, and the drain pad portion Pd includes:
A wiring resistance R103 mainly depending on a low-resistance conductive material such as chromium exists, a wiring capacitance C4 is formed between the drain line 103 and the source line 104, and the drain line 103 is connected to the bottom gate electrode. A wiring capacitance C5 is formed between the wiring capacitor C5 and the bottom gate line 102. Further, a signal path including the bottom gate electrode 22, the bottom gate line 102, and the bottom gate pad portion Pb is mainly provided with a low resistivity conductive material such as chromium, a low sheet resistance depending on a wiring length and a cross sectional area of the wiring. And a wiring resistance R102 based on the bottom gate line 10
A wiring capacitance C6 is formed between the line 2 and the source line 104. The source line 104 has a wiring resistance R
There are 104.

In FIG. 10, a top gate driver 110 connected to the top gate line 101, a bottom gate driver 120 connected to the bottom gate line 102, and a drain driver 130 connected to the drain line 103 are integrated circuits ( IC or LSI),
Alternatively, each pad portion Pt, which is configured as a transistor circuit such as an a-Si TFT or a p-Si TFT,
They are electrically connected via Pb and Pd.

Therefore, in the two-dimensional image reading device having such an equivalent circuit, the top gate electrode 21
The wiring resistance R101 of the top gate line 101 and the wiring resistance R30 of the ground electrode layer 30 are set to be high depending on a conductive material having a high resistivity such as ITO, while the wiring resistance R103 of the drain electrode and the drain line 103 is set high. ,
The wiring resistance R102 of the bottom gate electrode 22 and the bottom gate line 102 is set lower than the wiring resistance R101 depending on a low resistivity conductive material such as chromium.

Thus, when the object to be detected (finger) comes into contact with the earth electrode layer 30 and the static electricity charged on the object to be detected is discharged to the ground potential, the object is connected to the ground electrode layer 30 and the ground potential. Withstands static electricity (approximately 10
When a charged voltage exceeding about kV) is applied, a voltage (charge) higher than the electrostatic withstand voltage is not sufficiently discharged to the ground potential, and mainly remains on the object to be detected, and the wiring capacitance C1 is increased. In accordance with the wiring resistances R101 to R104 of the respective conductive layers (electrodes and lines) of the photosensor array 30 formed below the ground electrode layer 30 via .about.C6, the current flowing through the conductive layers is affected. At this time, current concentration on the conductive layer having the lowest resistance value becomes remarkable, and overcurrent flows to the driver connected to the conductive layer.
There is a possibility that the operating function of the driver is deteriorated or damaged.

Therefore, in the present embodiment, of the top gate driver 110, the bottom gate driver 120, or the drain driver 130, the wiring resistance is lower than the others, and the conductive layer (for example, the conductive layer (eg, The driver (bottom gate driver 120) connected to the bottom gate electrode 22 and the bottom gate line 102) is configured to have a high electrostatic withstand voltage.

Specifically, the bottom gate driver 120
Is different from the design rules of the transistors of other drivers. For example, the withstand voltage between the source and the drain is increased by increasing the distance between the source and the drain, an offset gate structure is formed, and the withstand voltage between the gate and the source and between the gate and the drain are increased by increasing the thickness of the gate insulating film. Alternatively, the channel resistance of the semiconductor layer is reduced by shortening the channel length of the semiconductor layer to make it easier to leak charges due to static electricity, so that the transistor resistance is reduced and the transistor voltage division ratio is reduced.

Therefore, when the voltage due to the electrostatic charge of the object to be detected is higher than the electrostatic withstand voltage set for the ground electrode layer 30, the current concentration on the conductive layer having a low wiring resistance causes Even if an overcurrent flows to the driver connected to the driver, the voltage applied to the transistor of the driver is reduced, so that the voltage due to the static electricity is distributed to the driver and other drivers in a more balanced manner. In addition, since the transistor withstand voltage can be increased, deterioration and breakage of the driver can be suppressed as much as possible.

<Second Embodiment> Next, a second embodiment of the two-dimensional image reading apparatus according to the present invention will be described with reference to the drawings. FIG. 11 is a schematic sectional view showing a configuration example of a second embodiment of the two-dimensional image reading apparatus according to the present invention, and FIG. 12 is another configuration example of the two-dimensional image reading apparatus according to the present embodiment. FIG. FIG.
FIG. 6 is a schematic cross-sectional view showing still another configuration example of the two-dimensional image reading device according to the embodiment. Here, the same components as those described above (FIGS. 8 and 9) are denoted by the same reference numerals, and description thereof will be simplified or omitted. Also,
This will be described with reference to the equivalent circuit shown in FIG.

The two-dimensional image reading apparatus according to the present embodiment
In order to improve the withstand voltage against the static electricity charged to the subject, a configuration in which the current concentration due to the static electricity in the conductive layer (electrode or line) constituting the photosensor array is suppressed instead of the above-described configuration in which the electrostatic withstand voltage of the driver is increased. are doing. Specifically, as shown in FIG. 11, for example, the bottom gate electrode 22 and the bottom gate line 10
2 is formed so that the film thickness of the metal conductive layer of chromium or the like constituting the layer 2 becomes smaller than the normal structure (see FIG. 8). Here, the film thickness St of the bottom gate electrode 22 and the bottom gate line 102 is set so as to balance the wiring resistances R101, R102, and R103 shown in FIG.

As another structure, as shown in FIG. 12, for example, the wiring width of the metal conductive layer forming the bottom gate line 102 is narrower than the normal structure (see FIG. 1). It is formed so that Here, the wiring width Sw of the bottom gate line 102 is set so as to balance the wiring resistances R101, R102, and R103 shown in FIG.

Further, as another configuration, for example, the film formation conditions and the like in the manufacturing process of the metal conductive layer forming the bottom gate electrode 22 and the bottom gate line 102 can be adjusted by increasing the wiring resistance of the metal conductive layer. To change. Here, for example, by setting the pressure in the step of forming the metal conductive layer to be higher than the normal pressure, the wiring resistances R101 and R10 shown in FIG.
2. Balance R103.

As still another configuration, for example,
The conductive material (material) forming the bottom gate electrode 22 and the bottom gate line 102 is changed to a material having a higher resistance than the wiring resistance of a metal conductive layer such as chromium. Here, for example, the wiring resistances R101, R102, and R103 shown in FIG. 10 are balanced by changing a metal material such as chromium to a high-resistance conductive material such as ITO. Alternatively, the bottom gate line 102 may be meandered to be longer than other low-resistance wirings to increase the resistance. Here, the wiring resistances R101, R102, R
Although the balance of 103 varies depending on the specifications of the photosensor array section, etc., in order to disperse the concentration of current to a specific conductive layer due to static electricity, the wiring resistances R101, R101
It is desirable to make the resistance values of R102 and R103 substantially equal.

In the present embodiment, the case where the configurations of the bottom gate electrode 22 and the bottom gate line 102 are changed to balance the wiring resistance has been described. However, the present invention is not limited to this. Alternatively, the configuration may be changed and set so as to increase the wiring resistance of another conductive layer, or a high resistance such as ITO may be used as long as the wiring resistance is balanced to make the wiring resistance substantially uniform. (For example, the top gate electrode 21 and the top gate line 10)
The wiring structure and the material may be changed and set so as to reduce the wiring resistance 1).

By the way, in each of the above configuration examples, for example, as shown in FIG. 11, the metal conductive layer forming the bottom gate electrode 22 and the bottom gate line 102 is formed to have a thin film thickness St. In a configuration in which the material is changed from a light-shielding conductive material such as chromium to a transparent conductive material such as ITO, light from below the double-gate photosensor 10 is applied to the semiconductor layer 1.
There is a possibility that the original light-shielding function of the bottom gate electrode 22, which is to prevent the light from being incident on the light emitting element 1, is impaired.

Therefore, such a bottom gate electrode 22
For example, as shown in FIG. 13, at least the bottom gate electrode 22A has a two-layer structure and the chromium layer having the above-mentioned thin film thickness or a transparent conductive material such as ITO as shown in FIG. Even when a thin film is formed, a configuration in which a light-shielding layer 22y having good light-shielding properties is provided under the upper conductive layer 22x made of a material can be favorably applied.

Therefore, according to the two-dimensional image reading apparatus according to the present embodiment, for example, a conductive material having a low wiring resistance is used so as to balance the wiring resistances R101, R102 and R103 of the conductive layers constituting the photosensor array. Since the resistance value of the layer is set to be high, even if the charged voltage due to the static electricity of the object to be detected is higher than the electrostatic withstand voltage set for the ground electrode layer 30, the conductive layer having a low wiring resistance is used. Current concentration to the driver, and the deterioration and breakage of the driver can be greatly suppressed.

<Third Embodiment> Next, a third embodiment of the two-dimensional image reading apparatus according to the present invention will be described with reference to the drawings. FIG. 14 is a schematic sectional view showing a schematic configuration of the third embodiment of the two-dimensional image reading apparatus according to the present invention. Here, the same components as those described above (FIG. 7) are denoted by the same reference numerals, and description thereof will be simplified or omitted.

As shown in FIG. 14, 2 according to the present embodiment,
The three-dimensional image reading apparatus is configured by a pair of rectangular electrode layers 31a and 31b separated from each other with a small gap so that the ground electrode formed on the photosensor array 100 divides the array area Aa into two. For example, one of the electrode layers 31a is provided with a power source 14 for constantly applying a predetermined DC voltage.
1 and the other electrode layer 31b is electrically connected to the ground potential. Also, one electrode layer 3
A detection unit 142 that detects a change in the voltage applied by the power supply 141 is connected to 1a. This detector 2
6 starts driving the photo sensor system when detecting a change in voltage specific to finger contact.

Therefore, when a detection object such as a finger is placed on the pair of electrode layers 31a and 31b, the detection unit 142 discharges the electric charge charged on the finger (human body) and discharges the electrode. A voltage change caused by a short circuit between the layers 31a and 31b is detected, and whether or not a finger is placed on the photosensor array 100 is determined.
0, bottom gate driver 120, drain driver 1
Output a control signal for controlling each of the operations 30;
The finger has a switch function of emitting light La from the surface light source 40 shown in FIG.

In the two-dimensional image reading apparatus having such a configuration, the object to be detected (for example, a finger) is placed so as to simultaneously contact the pair of electrode layers 31a and 31b constituting the ground electrode layer. Then, the static electricity charged on the detection target is discharged to the ground potential via the electrode layer 31b, and the contact state of the detection target is detected by the detection unit 142 connected to the electrode layer 31a. The reading operation of the image pattern (fingerprint) of the detection target is automatically executed and controlled based on the series of driving control methods described above. Therefore, similarly to the above-described embodiment, it is possible to increase the electrostatic withstand voltage by discharging the static electricity charged on the finger (human body) satisfactorily and suppressing the deterioration and damage of the driver against the excessive charged voltage. In addition, it is possible to provide a two-dimensional image reading apparatus that automatically executes the image reading operation by placing the object to be detected.

In each of the above-described embodiments, in order to suppress current concentration on a specific conductive layer due to static electricity, or to suppress deterioration or damage of the driver due to the static electricity, a structure in which the electrostatic withstand voltage of the driver is increased or a low Although the configuration in which the resistance of the conductive layer of the resistance is increased is individually shown, it is needless to say that the present invention can be suitably applied to a configuration in which these configurations are appropriately combined. Further, in each of the above-described embodiments, the case where a double gate type photo sensor is applied as the photo sensor has been described. However, the present invention is not limited to this. It goes without saying that it can be applied.

[0068]

According to the first aspect of the present invention, among the plurality of drive circuits, among the connected signal paths, the withstand voltage of the transistor constituting the one having the lowest wiring resistance is set to the highest. Due to this, at the time of discharging operation of static electricity charged on the detection target, current concentrates on the signal path with low wiring resistance,
Even when a large current flows, the withstand voltage of the drive circuit connected to the signal path is set high, so that damage and malfunction of the drive circuit can be suppressed, and the wiring resistance of the signal path is reduced. By lowering the off resistance of the transistor so that the channel resistance of the transistor that constitutes the lowest one becomes the lowest, it is easy to conduct static electricity,
Since the transistor voltage can be reduced, the voltage due to static electricity can be more evenly distributed, and breakage and malfunction of the drive circuit can be significantly suppressed.

According to the sixth aspect of the present invention, among the above-described signal paths, the wiring resistance of the signal path whose wiring resistance is low is increased, and becomes substantially uniform with the wiring resistance of the other signal paths. Thus, the balance of the wiring resistance is set. Specifically, for example, the thickness and width of the wiring constituting the signal path, the film forming conditions, or the material and the like are arbitrarily controlled so that the wiring resistance of each signal path is balanced. Therefore, at the time of discharging operation of static electricity charged on the detection target, current is not concentrated on a signal path having a low wiring resistance, but is dispersed in each signal path, so that a large current flows to a specific driver or circuit. It is possible to realize a two-dimensional image reading device capable of suppressing the occurrence of breakage and malfunction.

Here, the photosensor has a source electrode and a drain electrode formed with a semiconductor layer that generates carriers when excitation light is incident, and an insulating film at least above and below the channel region. A first gate electrode (top gate electrode) and a second gate electrode (bottom gate electrode) formed through the so-called double gate transistor,
The first gate electrodes are connected to a first driver, and the second
May be connected to a second driver, and the drain electrodes may be connected to an output circuit, thereby significantly reducing the thickness of the photo sensor and miniaturizing the fingerprint sensor. As a result, the density of the detection pixels can be increased, and the two-dimensional image reading apparatus excellent in the electrostatic withstand voltage as described above can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a basic structure of a double gate type photo sensor.

FIG. 2 is a schematic configuration diagram of a photosensor system including a photosensor array configured by two-dimensionally arranging double-gate photosensors.

FIG. 3 is a timing chart illustrating an example of a drive control method of the photo sensor system.

FIG. 4 is an operation conceptual diagram of a double gate type photo sensor.

FIG. 5 is a diagram showing a light response characteristic of an output voltage of the photo sensor system.

FIG. 6 is a cross-sectional view of a main part of a two-dimensional image reading apparatus to which a photo sensor system including a double gate type photo sensor is applied.

FIG. 7 is a schematic configuration diagram illustrating an overall configuration of a first embodiment of a two-dimensional image reading apparatus according to the present invention.

FIG. 8 is a schematic cross-sectional view illustrating a configuration in a row direction (x direction) of the two-dimensional image reading device according to the present embodiment.

FIG. 9 is a schematic cross-sectional view illustrating a configuration in a column direction (y direction) of the two-dimensional image reading apparatus according to the embodiment.

FIG. 10 is an equivalent circuit diagram corresponding to each configuration of the two-dimensional image reading apparatus according to the embodiment.

FIG. 11 is a schematic sectional view illustrating a configuration example of a two-dimensional image reading apparatus according to a second embodiment of the present invention.

FIG. 12 is a schematic cross-sectional view illustrating another configuration example of the two-dimensional image reading apparatus according to the embodiment.

FIG. 13 is a schematic sectional view showing still another configuration example of the two-dimensional image reading apparatus according to the embodiment.

FIG. 14 is a schematic sectional view showing a schematic configuration of a third embodiment of the two-dimensional image reading apparatus according to the present invention.

FIG. 15 is a schematic configuration diagram of a fingerprint reader having an electrostatic discharge structure according to the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Double gate photosensor 11 Semiconductor layer 12 Drain electrode 13 Source electrode 20 Protective insulating film 21 Top gate electrode 22, 22A Bottom gate electrode 30 Earth electrode layer 100 Photosensor array 101 Top gate line 102 Bottom gate line 110 Top gate driver 120 Bottom gate driver 130 Drain driver R30, R101 to R104 Wiring resistance

Continued on front page F-term (reference) 4M118 AA08 AB01 BA05 CA11 CA19 FB03 FB09 FB13 FB24 FB25 GA03 GA07 5B047 AA25 BB04 BC01 5C024 AX01 BX04 CY47 EX55 GX05 GX16 GX19 GY01 GZ02 HX35 HX40 HX41 NA14 5

Claims (8)

[Claims] 1. A photosensor array comprising a plurality of photosensors arranged therein, and a plurality of driving circuits for driving the photosensors, wherein a plurality of driving circuits drive the photosensors. In the two-dimensional image reading device for reading an image pattern, the plurality of driving circuits set resistance to static electricity charged on the detection target according to wiring resistance of each signal path connected to each of the plurality of driving circuits. Dimensional image reading device. 2. The photosensor has a source electrode and a drain electrode formed with a semiconductor layer that generates carriers when excitation light is incident thereon, and an insulating film above and below the channel region, respectively. A first gate electrode and a second gate electrode formed through the first and second gate electrodes, wherein the plurality of drive circuits are connected to the first gate line or the second gate line serving as the signal path. A first driver connected to a first gate electrode or a second gate electrode of a plurality of photosensors and controlling a photo-sensing operation, and a second gate line or a first gate line serving as the signal path; A second driver connected to the second gate electrode or the first gate electrode of the plurality of photosensors to control a selective read operation, and a drain line serving as the signal path. 2. The two-dimensional image reading device according to claim 1, further comprising: an output circuit connected to the drain electrodes of the plurality of photosensors and reading a voltage corresponding to carriers accumulated in the photosensors. . 3. The method according to claim 1, wherein the first gate line is made of a transparent conductive material, and the second gate line is made of a material having a lower resistivity than a material forming the first gate line. Item 3. The two-dimensional image reading device according to item 2. 4. The plurality of drive circuits each include a transistor, and among the plurality of drive circuits,
4. The two-dimensional image reading device according to claim 1, wherein a withstand voltage of a transistor of a circuit connected to a signal path having the lowest wiring resistance is higher than a withstand voltage of a transistor of another circuit. . 5. The plurality of driving circuits each include a transistor, and among the plurality of driving circuits, a channel resistance of a transistor connected to a signal path having the lowest wiring resistance is equal to a channel resistance of a transistor of another circuit. The two-dimensional image reading device according to claim 1, wherein the two-dimensional image reading device is smaller than a channel resistance. 6. A photosensor array comprising a plurality of photosensors arranged therein, and a plurality of driving circuits for driving the photosensors, wherein a plurality of driving circuits drive the photosensors. A two-dimensional image reading apparatus for reading an image pattern, wherein the plurality of drive circuits are set so as to make wiring resistance of each signal path connected to each substantially uniform. 7. The signal path has a substantially uniform wiring resistance by controlling at least one of a film thickness of a wiring constituting the signal path, a film forming condition of the wiring, a material of the wiring, and a width of the wiring. 7. The apparatus according to claim 6, wherein
The two-dimensional image reading device according to claim 1. 8. The photosensor includes a source electrode and a drain electrode formed with a semiconductor layer that generates carriers when excitation light is incident, and an insulating film above and below the channel region. A first gate electrode and a second gate electrode formed through the first and second gate electrodes, wherein the plurality of drive circuits are connected to the first gate line or the second gate line serving as the signal path. A first driver connected to the first gate electrode or the second gate electrode of the plurality of photosensors and controlling a photo sensing operation, and a second gate line or a first gate line serving as the signal path; A second driver connected to the second gate electrode or the first gate electrode of the plurality of photosensors to control a selective read operation, and a drain line serving as the signal path. An output circuit connected to the drain electrodes of the plurality of photosensors and reading a voltage corresponding to carriers accumulated in the photosensors, wherein the first gate line is made of a transparent conductive material, The two-dimensional image reading apparatus according to claim 6, wherein the second gate line is made of a material having a lower resistivity than a material forming the first gate line.