JP2001092951A - Two-dimensional image reading device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress occurrence of interlayer short-circuit and parasitic capacitance caused by a transparent conductive film formed on a photosensor device, to prevent a reading error operation, a decrease in detection sensitivity, a device damage, and the like. To provide a two-dimensional image reading apparatus capable of performing the above. A two-dimensional image reading apparatus includes a photosensor device formed by arranging a plurality of W-gate transistors on a glass substrate in a matrix.
A, a transparent conductive film 23A formed in a predetermined pattern on the surface of a protective insulating film formed by covering the W-gate transistor 10F, and a rear surface of the photosensor device 100A, And a surface light source 30 that irradiates the object to be detected in contact with the detection surface 20a provided on the side thereof and irradiates the object with uniform light. The transparent conductive film 23A is located immediately above the gap region between the W-gate transistors 10F. Is formed only.

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 two-dimensional image reading apparatus having a configuration in which an object to be detected is brought into contact with a photo sensor array in which photo sensors are arranged in a matrix to read a two-dimensional image. The present invention relates to a two-dimensional image reading device.

[0002]

2. Description of the Related Art Conventionally, a two-dimensional image reading apparatus for reading a printed material, a photograph, or a fine uneven pattern such as a fingerprint is provided with a photosensor constituted by arranging photoelectric conversion elements (photosensors) in a matrix. 2. Description of the Related Art There is an array having a structure in which a detection target is brought into contact with a detection surface provided on a photosensor array to read a two-dimensional image of the detection target. In a two-dimensional image reading apparatus having a structure in which the detection target directly contacts the detection surface, various methods are conceivable in order to suppress malfunction or damage due to static electricity or the like charged on the detection target. ing.

A configuration of a fingerprint reader will be described below as an example of a conventional two-dimensional image reader with reference to the drawings. The fingerprint reader shown in FIG. 10 includes a surface light source 101,
A plurality of photo sensors 1 provided above the surface light source 101
02a is provided with a photosensor device 102 arranged in a matrix and a transparent conductive film 103 formed on the photosensor device 102.
03, a light L from the surface light source 101 is applied to a detection target (for example, a finger) 110 contacting the detection target contact surface 103a on the upper surface.
By irradiating p, light / dark information is detected based on the reflected light Lr incident on the photosensor 102a corresponding to the concave / convex pattern of the fingerprint, and a fingerprint image is generated.

Here, the transparent conductive film 103 is made of ITO (In
It is formed of a transparent conductive material such as dium Tin Oxide (indium tin oxide), and is formed in a thin film over the entire upper surface of the photosensor device 102. The role of the transparent conductive film 103 is to discharge static electricity charged on the finger (human body) 110 contacting the detection object contact surface 103a to a ground potential or the like, thereby preventing a reading error operation or damage in the photosensor device 102. Things.

[0005] The fingerprint reader shown in FIG. 11 has a structure shown in FIG.
A pair of comb-teeth-shaped transparent conductive films 104a and 104b are formed such that the comb teeth are alternately arranged in an intricate manner, and a finger 110 is attached to both of the pair of transparent conductive films 104a and 104b.
The fingerprint reading operation is started by detecting a small current flowing when the contact is made, and the surface light source 101 irradiates the finger 110 with light Lp. Here, similarly to the fingerprint reader described above, the transparent conductive films 104a,
4b is formed of a transparent conductive material such as ITO,
By connecting one of the transparent conductive films 104a and 104b to, for example, a ground potential, the static electricity charged on the finger (human body) 110 is discharged, thereby preventing a reading malfunction or damage in the photosensor device 102. In the cross-sectional views of the photosensor shown in FIGS. 10 and 11, hatching is omitted for convenience of explanation and illustration.

[0006]

The above-described conventional two-dimensional image reading apparatus has the following problems. (A) For the purpose of discharging static electricity or switching the fingerprint reading operation, the transparent conductive films 103 and 10 are formed over the entire upper surface of the photosensor device 102 or in a comb shape.
4a and 104b, the photo sensor 10
If a defect such as a pinhole occurs in the protective insulating film (overcoat film) 102b between the transparent conductive film 2a and the transparent conductive films 103, 104a, and 104b, an interlayer short circuit occurs, and the yield as a photosensor device decreases. There is a problem that.

(B) Capacitive coupling (parasitic capacitance) occurs between the photosensor 102a and the transparent conductive films 103, 104a, and 104b, and noise is mixed in the detection signal of the photosensor 102a, causing a read malfunction. There is a problem that generation and a reduction in detection sensitivity are caused. (C) ITO, which is frequently used as a transparent conductive film in recent years,
The finger 110, which has low corrosion resistance and is an object to be detected as described above, is not directly connected to the transparent conductive films 103, 104a, and 10a.
4b, there is a problem that the progress of corrosion is further accelerated, which causes a reading malfunction and damages the photosensor device 102.

Accordingly, the present invention solves the above-mentioned problems and suppresses the occurrence of interlayer short-circuit and parasitic capacitance caused by a transparent conductive film formed on a photosensor device, thereby causing a reading malfunction and a reduction in detection sensitivity. It is another object of the present invention to provide a two-dimensional image reading apparatus capable of preventing a device from being damaged.

[0009]

According to a first aspect of the present invention, there is provided a two-dimensional image reading apparatus, wherein a plurality of photosensors arranged in a matrix on one surface of an insulating substrate are provided so as to cover the plurality of photosensors. In a two-dimensional image reading apparatus provided with a photosensor device having a light-transmitting insulating film formed, the light-transmitting film formed so as to cover a gap region between regions where the respective photosensors are formed. A conductive portion is formed only on the upper surface of the insulating film.

According to the first aspect of the present invention, only the light-transmitting insulating film is formed immediately above the photosensor, and the light-transmitting insulating film and the conductive film are formed only in the gaps between the photosensor formation regions. Since a portion is formed, even if a defect such as a pinhole occurs in the light-transmitting insulating film on the photosensor,
The interlayer short-circuit does not occur between the photosensor and the conductive portion, and the yield of the photosensor device can be improved. In addition, since the parasitic capacitance generated between the photo sensor and the conductive portion can be minutely suppressed,
Suppress noise from being mixed into the detection signal of the photo sensor,
Good reading operation and high detection sensitivity can be realized.

The conductive portion may have a structure in which a pair of conductive layers formed in a linear shape are provided to face each other, or may be formed in a comb-like shape. The pair of conductive layers may have a configuration in which the comb teeth are provided so as to face each other alternately.
Since one of the pair of conductive layers is electrically connected to the ground potential, the static electricity is discharged to the ground potential even if the detection target is charged with the static electricity, and the photo sensor is electrically connected to the ground. Since there is no influence, it is possible to prevent the occurrence of a reading error and the damage of the photo sensor device.

Further, the photosensor device may be controlled so as to start a reading operation by electrically connecting a pair of conductive layers by a detection object. In this case, switching operation of the reading operation can be controlled by the contact state of the object to be detected with the photosensor device, thereby suppressing occurrence of unnecessary driving states and poor reading in the case of insufficient contact of the object. Thus, appropriate drive control can be realized. further,
Since the formation positions of the photosensor and the conductive portion do not overlap each other, it is not necessary to use a transparent electrode material for the conductive portion, and the conductive portion is formed of an opaque conductive material having corrosion resistance against contact with the object to be detected. Therefore, it is possible to suppress the progress of corrosion due to the contact of the object to be detected, thereby preventing the occurrence of a reading error and the damage of the photo sensor device.

The photosensor includes a source electrode and a drain electrode formed with a channel region made of a semiconductor layer interposed therebetween, and a top gate electrode formed at least above and below the channel region with an insulating film interposed therebetween. And a bottom gate electrode, and in the channel region,
A so-called W-gate transistor may be used, in which charges corresponding to the amount of light reflected and incident on the detection object are generated and accumulated. In this case, the photosensor device may be thinned to read a two-dimensional image. The size of the device can be reduced, and the density of the detection pixels can be increased.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the configuration of a good photosensor applied to a two-dimensional image reading apparatus according to the present invention will be described. As a photosensor applied to the two-dimensional image reading device according to the present invention, a CCD (Charge Coupled Device) is used.
e) etc. can be used. CC
D, as is well known, has a configuration in which photosensors such as photodiodes and thin film transistors (TFTs) are arranged in a matrix, and electrons generated in accordance with the amount of light applied to the light receiving portion of each photosensor. The amount of hole pairs (the amount of charge) is detected by the horizontal scanning circuit and the vertical scanning circuit, and the luminance of irradiation light is detected.

In such a photosensor system using a CCD, it is necessary to separately provide a selection transistor for setting each of the scanned photosensors to a selected state. However, there is a problem that the size is increased. 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 W gate transistor) in which a photo sensor itself has a photo sensing function and a selection transistor function. Has been developed, and attempts have been made to reduce the size of the system and increase the density of pixels. This W-gate type transistor can be favorably applied to the two-dimensional image reading device of the present invention.

Hereinafter, the structure and function of the W gate type transistor will be described. FIG. 1 is a cross-sectional view illustrating the structure of a W-gate transistor. As shown in FIG. 1A, the W-gate transistor 10F includes a semiconductor layer 11 made of intrinsic amorphous silicon (ia-Si) or the like in which electron-hole pairs are generated when visible light is incident. Semiconductor layer 1
N ⁺ silicon layers 17, 1 provided at both ends of
8, the source electrode 12 and the drain electrode 13 formed on the n ⁺ silicon layers 17 and 18, and the block insulating film 14 and the top gate insulating film 15 above the semiconductor layer 11 (upper drawing). A top gate electrode 21;
And a bottom gate electrode 22 formed below the semiconductor layer 11 (below the drawing) with the bottom gate insulating film 16 interposed therebetween.

In FIG. 1A, the top gate electrode 21, the top gate insulating film 15, the bottom gate insulating film 16, and the protective insulating film 20 provided on the top gate electrode 21 are all semiconductor layers 11 The bottom gate electrode 22 is made of a material that blocks the transmission of visible light, while the bottom gate electrode 22 is made of a material that has high transmittance (high translucency) with respect to visible light that excites light. It has a structure to detect only the irradiation light (visible light) to be emitted.

That is, the W gate type transistor 10
The semiconductor layer 1 in which an electron-hole pair is generated when visible light is incident is used as a common channel region.
1, an upper MOS transistor formed by a source electrode 12, a drain electrode 13, and a top gate electrode 21, and a semiconductor layer 11, a source electrode 12, and a drain electrode 13.
And lower MOS formed by bottom gate electrode 22
A transparent insulating substrate 1 such as a glass substrate is formed by combining two MOS transistors each including a transistor.
9. Such a W-gate transistor 10 is generally represented by an equivalent circuit as shown in FIG. Here, TG is a top gate terminal, BG is a bottom gate terminal, S is a source terminal, and D is a drain terminal.

Next, a photo sensor system constituted by two-dimensionally arranging the above-mentioned W gate type transistors will be briefly described with reference to the drawings. FIG. 2 is a schematic configuration diagram of a photosensor system configured by two-dimensionally arranging W-gate transistors. As shown in FIG. 2, the photosensor system is roughly divided into a photosensor array 100F in which a large number of W-gate transistors 10F are arranged in a matrix, and each W-gate transistor 10F.
Top and bottom gate lines 101 and 102 connecting the top gate terminal TG and the bottom gate terminal BG in the row direction, respectively, and a top gate driver 111 and a bottom gate driver connected to the top gate line 101 and the bottom gate line 102, respectively. 112
A data line 103 in which the drain terminals D of the respective W-gate transistors are connected in the column direction;
3 is connected to the column switch 113. Here, φtg and φbg are reference voltages for generating a reset pulse φTn and a readout pulse φBn described later, respectively, and φpg is a precharge signal for controlling the timing of applying the precharge voltage Vpg.

In such a configuration, a photo sensing function is realized by applying a voltage from the top gate driver 111 to the top gate terminal TG, and a voltage is applied from the bottom gate driver 112 to the bottom gate terminal BG, and the data line 103 is applied. The selective read function is realized by taking in the detection signal to the column switch 113 through the interface and outputting it as serial data (Vout).

Next, a drive control method of the above-described photo sensor system will be described with reference to the drawings. FIG.
5 is a timing chart showing a drive control method of the photo sensor system. As shown in FIG. 3, first, in the reset operation, the top gate line 1 in the n-th row is set.
A pulse voltage (reset pulse; for example, a high level of +15 V) φTn is applied to 01 to release carriers (holes) accumulated in the semiconductor layer of each W-gate transistor 10F (reset period Treset).

Next, in the light (carrier) accumulation operation, a low level (for example, =) is applied to the top gate line 101.
By applying the bias voltage φTn (−15 V), the reset operation ends, and the carrier accumulation period Ta by the light accumulation operation starts. In the carrier accumulation period Ta, carriers are accumulated in the channel region according to the amount of light incident from the top gate electrode side. Then, in the precharge operation, a predetermined voltage (precharge voltage) Vpg is applied to the data line 103 in parallel with the carrier accumulation period Ta to cause the drain electrode 13 to hold a charge (precharge period Tprch).

Next, in the read operation, after the precharge period Tprch has elapsed, the bottom gate line 1
02 is a high-level (eg, +10 V) bias voltage (read selection signal; hereinafter, referred to as a read pulse) φ
By applying Bn, the W-gate type transistor 1
0F is turned on (reading period Tread). Here, in the read period Tread, the carriers (holes) accumulated in the channel region are the bias voltage φTn (−15 V) applied to the top gate line 101 having the opposite polarity.
Bottom gate line 102
The n-channel is formed by the bias voltage φBn applied to the data line 103, and the data line voltage VD of the data line 103 shows a tendency to gradually decrease from the precharge voltage Vpg over time according to the drain current.

That is, when the light accumulation state in the carrier accumulation period Ta is a dark state and holes are not accumulated (captured) in the channel region, a negative bias is applied to the top gate TG so that the bottom gate BG is not charged. The positive bias is canceled, and the W-gate type transistor 10F
The state becomes the FF state, and the drain voltage, that is, the voltage VD of the data line 103 is maintained substantially as it is. On the other hand, when the light accumulation state is the bright state, holes corresponding to the amount of incident light are trapped in the channel region, so that it acts to cancel the negative bias of the top gate TG. Due to the positive bias of the gate BG, the W-gate transistor 10F is turned on. Then, according to the ON resistance according to the amount of incident light,
The voltage VD of the data line 103 will decrease.

Therefore, the voltage V of the data line 103 is
The changing tendency of D depends on the amount of light received during the time period (the carrier accumulation period Ta) from the end of the reset operation by application of the reset pulse φTn to the top gate TG to the application of the readout pulse φBn to the bottom gate BG. It is closely related, and shows a tendency to decrease gradually when the amount of accumulated carriers is small, and shows a tendency to decrease sharply when the amount of accumulated carriers is large.

Therefore, the reading period Tread starts, and the voltage V of the data line 103 after a predetermined time has elapsed.
By detecting D, or by detecting a time until the voltage is reached with reference to a predetermined threshold voltage, the amount of irradiation light is converted. By repeating the same processing procedure for the W-gate transistor 10F in the (n + 1) -th row with the series of drive control described above as one cycle, the W-gate transistor 10F can be operated as a two-dimensional sensor system.

FIG. 4 is a sectional view of a main part of a two-dimensional image reading apparatus to which the above-described photo sensor system is applied. Here, for convenience of description and illustration, hatching indicating a cross-sectional portion of the photosensor system is omitted.
As shown in FIG. 4, when the finger 40 is placed on the fingerprint detection surface, that is, at the time of fingerprint detection, the translucent layer of the skin surface layer 40B of the finger 40 comes into contact with the light-transmitting insulating film, and thus the light is transmitted. An air layer having a low refractive index disappears at the interface between the optical insulating film and the skin surface layer 40B. Since the thickness of the skin surface layer 40B is greater than 650 nm, the red light La emitted at an angle equal to or larger than the critical angle and internally incident on the projection 40a of the fingerprint 40A propagates while scattering and reflecting the skin surface layer 40B. I do. The propagated light Lb enters the semiconductor layer 11 of the W-gate transistor 10F as excitation light.
By transmitting the transparent insulating films 20, 15, and 14 and the top gate electrode 21 and entering the semiconductor layer 11 as described above, carriers corresponding to the image pattern of the detection target 40 are accumulated, and the above-described series of driving is performed. According to the control method, the image pattern of the detection target 40 can be read as brightness information.

In the concave portion 40b of the fingerprint 40A, the irradiated red light La is emitted at an angle equal to or greater than the critical angle, so that the interface between the fingerprint detection surface 20a of the protective insulating film 20 and the air layer is formed. The light passes through, reaches the finger at the tip of the air layer, and is scattered in the skin surface layer 40B. However, since the skin surface layer 40 of the finger has a higher refractive index than air, the light in the skin surface layer 40 incident on the interface at a certain angle. Is W which is hard to escape into the air layer and corresponds to the concave portion.
The incidence of the gate transistor 10F on the semiconductor layer 11 is suppressed. Light transmitted through the finger through the air layer in the concave portion propagates through the skin surface layer 40 while repeating irregular reflection,
The light reaches the convex portion that is in contact with the fingerprint detection surface 20a, from which the light enters the semiconductor layer 11 of the W-gate transistor 10F corresponding to the convex portion via the protective insulating film 20. In each of the embodiments described below, a case will be described in which the above-described W-gate transistor is applied as a photosensor. However, the present invention is not limited to this.
Needless to say, a photodiode, a TFT, or the like can be favorably applied.

Next, an embodiment of a two-dimensional image reading apparatus according to the present invention will be described with reference to the drawings. <First Embodiment> FIG. 5 is a main part configuration diagram showing a first embodiment of a two-dimensional image reading apparatus according to the present invention. Here, the same components as those of the above-described W-gate type transistor are denoted by the same reference numerals, and description thereof will be simplified.
As shown in FIG. 5A and FIG.
The three-dimensional image reading apparatus includes a photosensor device 100A formed by arranging a plurality of the above-described W-gate transistors 10F in a matrix on a glass substrate 19;
A transparent conductive film (conductive portion) 23A formed in a predetermined pattern on the surface of a protective insulating film 20 formed by covering the gate transistor 10F;
A of the photo sensor device 100A
And a surface light source 30 for irradiating uniform light to an object to be detected (not shown) in contact with the upper surface (the transparent conductive film 23A).

Here, just above the formation region of the W gate type transistor 10F, only a transparent protective insulating film 20 such as a silicon nitride film is formed by lamination, and only above the gap region between the W gate type transistors 10F, A transparent conductive film 23A such as ITO is formed via the protective insulating film 20.
That is, the transparent conductive film 2 formed on the protective insulating film 20
3A is formed only on the gap region between the W-gate transistors 10F, avoiding the region directly above the W-gate transistors 10F provided in a matrix below the protective insulating film 20.

Further, as shown in FIG. 5A, the transparent conductive film 23A is constituted by a pair of conductive patterns 23a and 23b formed to have a comb-like shape in the left-right direction of the drawing.
In addition, the conductive patterns 23a and 23b are arranged such that the comb teeth alternately interlace. Furthermore, at least one of the pair of conductive patterns 23a and 23b (for example, the conductive pattern 23a)
Are electrically connected to the ground potential.

In the two-dimensional image reading apparatus having such a configuration, the object to be detected (for example, a finger) is placed so that the pair of conductive patterns 23a and 23b constituting the transparent conductive film 23A simultaneously contact each other. Then, the static electricity charged on the detection target is changed to one of the conductive patterns 23.
After being discharged to the ground potential via a, the reading operation of the object to be detected is performed normally based on the series of drive control methods shown in FIG. It should be noted that the top gate insulating film 1 is so arranged that light in the wavelength range that excites the semiconductor layer 11 does not propagate in each film.
5, the bottom gate insulating film 16 and the protective insulating film 20 are each a silicon nitride film having a refractive index of about 1.8 to 2.0, and have a thickness of 150 nm, 250 nm,
The top gate electrode 21 is preferably ITO having a refractive index of about 2.0 to 2.2, and the film thickness is preferably about 50 nm.

As described above, according to the two-dimensional image reading apparatus according to the present embodiment, the transparent conductive film 23A is disposed on the gap region between the W-gate transistors 10F, avoiding the region immediately above the W-gate transistor 10F. Formed only in
Since the gate-type transistor 10F and the transparent conductive film 23A are not disposed close to and opposite to each other, a defect such as a pinhole may occur in the protective insulating film 20 formed by covering the W-gate transistor 10F. Also, no interlayer short-circuit occurs in the protective insulating film 20. Further, the W gate type transistor 10F and the transparent conductive film 23A
Since the parasitic capacitance generated between the detection signal and the detection signal at the time of fingerprint reading can be suppressed minutely, noise can be suppressed from being mixed into the detection signal at the time of fingerprint reading.

Further, when the object to be detected contacts the transparent conductive film 23A during the reading operation, the static electricity charged on the object to be detected is discharged to the ground potential via the conductive pattern. Electrical influence on the photo sensor device 100A and the photo sensor device 100A can be prevented from occurring. In the two-dimensional image reading apparatus shown in the above-described embodiment, only one of the pair of conductive patterns 23a and 23b forming the transparent conductive film 23A is electrically connected to the ground potential. Conductive pattern 23a,
23b may be connected to a drive control circuit of a two-dimensional image reading device (not shown). The reading operation in this case will be described below. Here, description will be made with reference to the detailed structure of the W-gate transistor 10F shown in FIG. 4 as appropriate.

FIG. 6 is a schematic diagram showing a fingerprint reading operation when the two-dimensional image reading device according to the present embodiment is applied to a fingerprint reading device. Here, for convenience of description and illustration, hatching indicating a cross-sectional portion of the photosensor system is omitted. As shown in FIG. 6, first, a finger 40a, which is an object to be detected, is placed so as to simultaneously contact a pair of conductive patterns 23a and 23b constituting the transparent conductive film 23A. The charged static electricity is discharged to the ground potential via one of the conductive patterns, and the conductive patterns 23a and 23b are electrically connected to each other via the finger 40a, and the specific resistance value of the finger 40a Is supplied to a drive control circuit of a two-dimensional image reading apparatus (not shown), and the drive control circuit uses this as a trigger to control the start of the fingerprint reading operation.

Next, predetermined light Lp is emitted from the surface light source 30 to the finger 40a on the photosensor device 100A, and the finger 40a corresponding to the concave and convex pattern of the fingerprint is determined based on a series of drive control methods shown in FIG. Reads the brightness information and generates a fingerprint image. Here, the light Lp from the surface light source 30 is applied to the transparent insulating film (top gate insulating film) 1 formed in the gap region between the glass substrate 19 and the W-gate transistor 10F constituting the photosensor device 100A.
5. The light passes through the protective insulating film 20 and the transparent conductive film 23A, and is irradiated on the concave and convex portions of the fingerprint. Further, the light irradiated on the finger 40a and reflected in accordance with the concave and convex pattern of the fingerprint is transmitted through the transparent conductive film 23A, the protective insulating film 20, and the like.
The light enters the semiconductor layer 11 of the W-gate transistor 10F.

After the fingerprint reading is completed, the finger 40a is separated from the transparent conductive film 23A, whereby the pair of conductive patterns 23a and 23b are electrically insulated from each other. The reading operation end control is executed. Thus, the transparent conductive film 23A
Since the reading operation can be controlled in accordance with the contact state of the object to be detected with the photosensor device 100A by providing the switch function to It is possible to suppress a reading defect or the like in a sufficient contact state and realize appropriate drive control.

<Second Embodiment> FIG. 7 is a main part configuration diagram showing a second embodiment of a two-dimensional image reading apparatus according to the present invention. Here, the same components as those of the above-described W gate type transistor are denoted by the same reference numerals, and description thereof will be omitted. As shown in FIG. 7, the two-dimensional image reading apparatus according to the present embodiment differs from the first embodiment in that
Immediately above the gap region between the gate transistors 10F,
A pair of conductive patterns 23a and 23b formed in a comb shape (horizontal direction in the drawing) is formed by
3c is added to form a leaf vein. Here, the newly added protruding pattern 23c is also
The protective insulating film 20 is formed only directly above the gap region between the W-gate transistors 10F.

According to the two-dimensional image reading apparatus having such a configuration, the transparent conductive film 23A is formed only on the gap region between the W-gate transistors 10F, avoiding the region immediately above the W-gate transistor 10F. And
Conductive patterns 23a, 23 constituting transparent conductive film 23A
b, 23c correspond to the matrix arrangement of the W-gate transistors 10F,
Is formed in a shape pattern extending in the two-dimensional direction so as to surround the transparent conductive film 23A and the W-gate transistor 10F. The static electricity charged on the detection body can be satisfactorily discharged through the conductive pattern having a large area, and the occurrence of a reading malfunction due to the static electricity and the damage of the photo sensor device 100A can be further suppressed.

<Third Embodiment> FIG. 8 is a schematic diagram showing a two-dimensional image reading apparatus according to a third embodiment of the present invention, and FIG. 9 is a two-dimensional image reading apparatus according to the third embodiment. FIG. 11 is a schematic plan view illustrating another configuration example of the reading device. Here, the same components as those of the above-described W gate type transistor are denoted by the same reference numerals, and description thereof will be omitted. Further, for the sake of explanation and illustration, hatching indicating a cross-sectional portion of the photosensor system is omitted. As shown in FIG. 8, the two-dimensional image reading apparatus according to the present embodiment is formed with a protective insulating film 20 directly above the gap region between the W-gate transistors 10F in the first embodiment described above. IT
It is characterized in that a metal conductive film 23B having excellent corrosion resistance is applied instead of the transparent conductive film 23A such as O.

That is, as described in the prior art, the I-type which has been frequently used in liquid crystal display devices and reading devices in recent years.
TO has low corrosion resistance. In particular, the contact of an object to be detected such as a finger causes the corrosion of the conductive film surface to proceed more quickly, causing a reading error and damage to the photo sensor device.
Therefore, in the present invention, the transparent conductive film 23 such as ITO is used.
Instead of A, the conductive patterns 23d and 23e are formed using a metal material having excellent corrosion resistance, for example, a thin film of chromium Cr or tantalum Ta.

Here, the two-dimensional image reading apparatus according to the present invention, as shown in FIG.
A light L emitted from a surface light source 30 disposed on the back side of A
p transmits through the transparent insulating film (top gate insulating film) 15 and the protective insulating film 20 other than the formation region of the W-gate transistor 10F and the metal conductive film 23B constituting the photosensor device 100A, and A read image is generated by irradiating a certain finger 40a and reading reflected light Lr corresponding to a concave / convex pattern (image pattern) of the fingerprint as brightness information. Therefore, the metal conductive film 23B applied to the present embodiment needs to be formed so that at least the interruption of the light Lp from the back side can be limited to a minimum and the object to be detected can be irradiated with sufficient light Lp. is there.

That is, the metal conductive film 23B formed on the protective insulating film is formed only on the gap region between the W-gate transistors 10F, avoiding the region immediately above the W-gate transistor 10F, and The transmission and reflection paths of the light from the light source 30 are formed so as to be blocked in a minimum area, so that the reading operation function of the photosensor device 100A is not affected. Therefore, the progress of corrosion is suppressed even by the contact of the object to be detected, and high practicability of preventing the occurrence of a reading error and the damage of the photo sensor device while realizing static electricity removal and switch control of the reading operation satisfactorily is realized. A two-dimensional image reading device can be realized.

Incidentally, the metal conductive film shown in this embodiment is
The present invention can be applied to the two-dimensional image reading device according to the second embodiment. That is, as shown in FIG.
The metal conductive film 23B is formed only on the gap region between the W-gate transistors 10F, avoiding the region immediately above the W-gate transistor 10F.
Conductive patterns 23d, 23e, 23f constituting 3B
Are formed so as to surround each W-gate transistor 10F, corresponding to the matrix arrangement of the W-gate transistors 10F. Therefore, the metal conductive film 23B
And the occurrence of parasitic short-circuit and parasitic capacitance between the transistor and the W-gate transistor 10F can be prevented and suppressed.
Static electricity charged on the object to be detected can be satisfactorily discharged through a conductive pattern having a large area and having a characteristic of being hardly corroded with time, causing a reading malfunction due to static electricity and the photo sensor device 100A. Breakage and the like can be further suppressed.

In each of the embodiments described above, a pair of conductive patterns 2 forming the transparent conductive films 23A and 23B are used.
Although the configuration in which the combs 3a and 23b and the combs 23d and 23e are formed in the form of comb teeth and arranged so that the comb teeth intersect each other has been described, the present invention is not limited to this.
In other words, at least the pair of conductive patterns may be formed so as not to be directly above the formation region of the W-gate transistor 10F. For example, the pair of conductive patterns may be formed in a folded shape, a spiral shape, or the like. Needless to say, it may be one that is available. The source and drain electrodes 1 of the W-gate type transistor 10F
Reference numerals 2 and 13 are connected to an external circuit by wiring, and this wiring partially overlaps the transparent conductive film. However, this wiring is lower than the top gate electrode 21 of each of the above embodiments by the thickness of the top gate insulating film 15. Therefore, in order for the wiring and the transparent conductive film to be short-circuited, a pinhole must be formed in the protective insulating film 20 and the top gate insulating film 15 at the same location, and the probability is sufficiently low.

[0046]

According to the first aspect of the present invention, only the light-transmitting insulating film is formed immediately above the photosensor, and the light-transmitting insulating film is formed only in the gap between the photosensor formation regions. And the conductive portion is formed, so that even if a defect such as a pinhole occurs in the light-transmitting insulating film on the photosensor, no interlayer short-circuit occurs between the photosensor and the conductive portion, The yield of sensor devices can be improved. In addition, since the parasitic capacitance generated between the photosensor and the conductive part can be suppressed very small, noise is prevented from being mixed into the detection signal of the photosensor, and good reading operation and high detection sensitivity are realized. can do.

The conductive portion may have a structure in which a pair of conductive layers formed in a linear shape are provided facing each other, or may be formed in a comb shape. The pair of conductive layers may have a configuration in which the comb teeth are provided so as to face each other alternately.
Since one of the pair of conductive layers is electrically connected to the ground potential, the static electricity is discharged to the ground potential even if the detection target is charged with the static electricity, and the photo sensor is electrically connected to the ground. Since there is no influence, it is possible to prevent the occurrence of a reading error and the damage of the photo sensor device.

Further, the photosensor device may be controlled so that a reading operation is started by electrically conducting a pair of conductive layers by the object to be detected. In this case, switching operation of the reading operation can be controlled by the contact state of the object to be detected with the photosensor device, thereby suppressing occurrence of unnecessary driving states and poor reading in the case of insufficient contact of the object. Thus, appropriate drive control can be realized. further,
Since the formation positions of the photosensor and the conductive portion do not overlap each other, it is not necessary to use a transparent electrode material for the conductive portion, and the conductive portion is formed of an opaque conductive material having corrosion resistance against contact with the object to be detected. Therefore, it is possible to suppress the progress of corrosion due to the contact of the object to be detected, thereby preventing the occurrence of a reading error and the damage of the photo sensor device.

The photosensor comprises a source electrode and a drain electrode formed with a channel region made of a semiconductor layer interposed therebetween, and a top gate electrode formed at least above and below the channel region with an insulating film interposed therebetween. And a bottom gate electrode, and in the channel region,
A so-called W-gate transistor may be used, in which charges corresponding to the amount of light reflected and incident on the detection object are generated and accumulated. In this case, the photosensor device may be thinned to read a two-dimensional image. The size of the device can be reduced, and the density of the detection pixels can be increased.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a structure of a W-gate type transistor applied to a two-dimensional image reading device according to the present invention.

FIG. 2 is a schematic configuration diagram of a photosensor system configured by two-dimensionally arranging W-gate transistors.

FIG. 3 is a timing chart showing a drive control method of the photo sensor system.

FIG. 4 is a sectional view of a main part of a two-dimensional image reading apparatus to which the photo sensor system is applied.

FIG. 5 is a main part configuration diagram showing a first embodiment of a two-dimensional image reading apparatus according to the present invention.

FIG. 6 is a schematic diagram showing a fingerprint reading operation when the two-dimensional image reading device according to the first embodiment is applied to a fingerprint reading device.

FIG. 7 is a main part configuration diagram showing a second embodiment of the two-dimensional image reading apparatus according to the present invention.

FIG. 8 is a schematic diagram showing a third embodiment of the two-dimensional image reading apparatus according to the present invention.

FIG. 9 is a schematic plan view illustrating another configuration example of the two-dimensional image reading apparatus according to the third embodiment.

FIG. 10 shows a first example of a conventional two-dimensional image reading apparatus.
It is a schematic diagram showing an example of.

FIG. 11 illustrates a second example of the two-dimensional image reading apparatus according to the related art.
It is a schematic diagram showing an example of.

[Explanation of symbols]

10F W gate type transistor 11 Semiconductor layer 12 Source electrode 13 Drain electrode 14 Block insulating film 15 Top gate insulating film 16 Bottom gate insulating film 17, 18 n ⁺ silicon layer 19 Insulating substrate 20 Protective insulating film 20a Detection surface 21 Top gate electrode 22 Bottom gate electrode 23A Transparent conductive film 23B Metal conductive film 23a to 23f Conductive pattern 30 Surface light source 40 Detected object 40a Finger 100A Photosensor device 100F Photosensor array

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F065 AA56 CC00 DD16 GG21 JJ03 JJ26 MM22 UU02 4M118 AA05 AA08 AB10 BA05 BA10 BA14 CA09 CA32 CB06 CB14 DB01 DD12 FB09 FB13 GA02 GA03 GB11 GB15 5B047 AA25 BB04 BC14

Claims (7)

[Claims] 1. A photosensor device comprising: a plurality of photosensors arranged in a matrix on one surface side of an insulating substrate; and a light-transmitting insulating film formed so as to cover the plurality of photosensors. In the two-dimensional image reading device, a conductive portion is formed only on an upper surface of the translucent insulating film formed so as to cover a gap region between the regions where the photosensors are formed. Characteristic two-dimensional image reading device. 2. The two-dimensional image reading apparatus according to claim 1, wherein the conductive portion is provided with a pair of conductive layers formed in a linear shape so as to face each other. 3. The conductive portion according to claim 1, wherein a pair of conductive layers each formed in a comb-like shape are provided so as to face each other such that the comb-like teeth alternately interlace. Two-dimensional image reading device. 4. The two-dimensional image reading apparatus according to claim 2, wherein one of the pair of conductive layers is electrically connected to a ground potential. 5. The photosensor device is controlled to start a reading operation of the detection object by electrically connecting the pair of conductive layers by the detection object. Item 2. The two-dimensional image reading device according to any one of Items 2 to 4. 6. The device according to claim 1, wherein the conductive portion is formed of a conductive material having corrosion resistance at least against contact with the detection target. Dimensional image reading device. 7. The photosensor comprises a source electrode and a drain electrode formed with a channel region made of a semiconductor layer interposed therebetween, and a top gate electrode formed at least above and below the channel region with an insulating film interposed therebetween. And a bottom gate electrode, wherein a charge corresponding to an amount of light reflected and incident by the object to be detected is generated and stored in the channel region. A two-dimensional image reading device according to any one of the above.