JPH0917987A - Contact type image sensor and manufacturing method - Google Patents

Abstract

PURPOSE: To provide a matrix drive type contact type image pickup sensor which is superior in the economy as being a low cost, operates at high speed with less dispersion of the characteristic and has a drive circuit which is composed of TFT elements and integrated on the same sensor substrate together with sensor elements. CONSTITUTION: The structure of a TFT element 4B which composes a drive circuit is at least composed of a gate electrode (first electrode layer 21), gate insulation layer 22, semiconductor layer 23 and impurity semiconductor layer 24 laminated in this order or reverse order on a glass substrate 20. The semiconductor layer 24 is composed of a layer deposited up to specified thickness by only one step of depositing operation to form a single layer structure without any discontinuity in its thickness direction and the layer 24 is contacted with both ends of a channel formed at the boundary between the insulation layer 22 and semiconductor layer 23, corresponding to a gate electrode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact image sensor for reading an image original or the like and a method for manufacturing the same, and more particularly to a photoelectric conversion sensor element array on the same insulating transparent substrate and a drive circuit for matrix driving the same. The present invention relates to a matrix drive type contact image sensor having an integrated structure and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, there has been an increasing trend toward miniaturization of devices used for image original reading devices such as facsimiles.
Document reading devices are roughly classified into a reduction optical system that reduces an image document by an optical system using a lens and combines it on a CCD to read it, and a plurality of substrates on which a substrate having a length larger than the document reading width is used. There is a contact image sensor system in which by arranging individual sensor elements, the sensor substrate is directly brought into close contact with the original and is read without using a reduction optical system. Of these, the contact image sensor method is attracting attention as a method that can easily achieve miniaturization as a reading device.

The contact image sensor is as shown in FIG.
In the housing 81, a sensor substrate 100 on which sensor elements are arranged, a light source 83 for illuminating a document, and a substrate 84 for mounting the light source are fixed. still,
LEDs are generally used as the light source 83, but the light source 83 is not limited to this. The light emitted from the light source 83 passes through a lighting window provided on the sensor substrate 100 and is applied to the image original 85 being conveyed while being in close contact with the sensor substrate 100 by the platen roller 86, and the reflected light thereof is reflected on the sensor substrate 100. By entering the sensor element formed on the surface of 100, the intensity of the reflected light is converted into the intensity of the electric signal.

FIG. 9 is a circuit diagram of a conventional contact image sensor, and the inside of the frame shown by the broken line in the figure is the circuit inside the sensor substrate 100. M × n sensor elements 1 are arranged in the original reading width direction, and a storage capacitor 2 and a transfer TFT element 3A are connected to each of these sensor elements. When light is incident on the sensor element 1, a photocurrent is generated and the charge is stored in the storage capacitor 2. Then, the driving wiring 51 is driven by the driving IC 50 to turn on the transfer TFT element 3A, the charges accumulated in the storage capacitor 2 are taken out to the reading wiring 61, and the charges are detected by the detection IC 60 to detect the original. A read operation is performed. The sensor element 1, the storage capacitor 2 and the transfer TFT element 3A are n
Each block is divided into m blocks, and the gate electrode of the TFT element 3A in each block is shared by the common drive wiring B _m.
Connect with. Further, the source electrodes of the n-th transfer TFT elements 3A of all the different blocks are connected by a common read wiring S _n to form a matrix wiring. Then, the gate electrode of the transfer TFT element 3A is time-divisionally driven in block units, and image reading signals are sequentially taken out for each block. By adopting such a matrix drive system,
It is possible to reduce the size by reducing the wiring area and reduce the cost by reducing the number of detection ICs.

More recently, the drive circuit, which is composed of the drive IC 50, is integrated in the sensor substrate by using the TFT element so that the drive circuit can be manufactured in the same manufacturing process as the sensor substrate. Some have been done. As a result, the driving IC becomes unnecessary, and the cost can be further reduced. FIG. 10 is a circuit diagram of a contact image sensor in which the above-described drive circuit is integrated in the sensor substrate 110 by using TFT elements, and the frame shown by the broken line in the drawing is the circuit in the sensor substrate. M × n sensor elements 1 are arranged in the document reading width direction, and each of these sensor elements has a storage capacitor 2 and a transfer TFT element 3.
A is connected. The driving TFT element 4A constitutes a driving circuit with the transistors Q ₁₁ , Q ₁₂ , and Q ₁₃ . When light is incident on the sensor element 1, a photocurrent is generated and the electric charge is stored in the storage capacitor 2. And drive TF
To turn on the transfer TFT element 3A by T elements Q _13, the document reading operation is performed by taking out the charges accumulated in the storage capacitor 2 to the read line 61 to detect it by detecting IC 60.

FIG. 11 is a plan view of the sensor substrate 110 of the contact image sensor shown in the circuit diagram of FIG. When the light incident from the back side of the sensor substrate through the lighting window 6 is reflected on the document and enters the sensor element 1, a photocurrent is generated and the electric charge is stored in the storage capacitor 2. Next, the transfer TFT element 3A is driven by the drive circuit 5 to be turned on, and the accumulated charge is taken out to the read wiring 61.

FIG. 12 shows the manufacturing process of the contact image sensor substrate, taken along the line Aa in FIG. First, a gate electrode is formed by depositing a first electrode layer 21 made of an opaque metal such as Cr or Al on the glass substrate 20 by a method such as sputtering and then patterning it by a method such as photolithography. (Fig. 12
(A)).

Next, by a method such as plasma CVD, a gate insulating layer 22 made of silicon nitride or the like, a semiconductor layer 23 made of amorphous silicon, and an impurity semiconductor made of amorphous silicon doped with impurities such as phosphorus. Layer 24 and is deposited sequentially. And the impurity semiconductor layer 24 of them
And after patterning the semiconductor layer 23, a contact hole is opened in the gate insulating layer 22 (FIG. 12).
(B)).

Subsequently, a second electrode layer 25 made of an opaque metal such as Cr or Al is deposited by a method such as sputtering and then patterned to form a source electrode, a drain electrode, a storage capacitor electrode and a wiring ( 12
(C)).

Next, after removing the impurity semiconductor layer 24 in the back channel portion of the sensor element 1, the transfer TFT element 3A and the driving circuit 5 TFT element 4A by etching, a protective insulating layer 26 is deposited on the entire surface of the substrate (FIG. 12
(D)).

In the contact image sensor whose manufacturing process is shown in FIG. 12, the sensor element 1, the transfer TFT element 3A and the TFT element of the drive circuit 5 are formed in the same manufacturing step. Therefore, an element structure and manufacturing process conditions are required to bring out the characteristics required for each of these elements in a well-balanced manner. 13 is the same as FIG.
Photocurrent of sensor element and TFT by the manufacturing process shown in
6 is a graph showing the relationship between the on-resistance of an element and the film thickness of amorphous silicon (hereinafter abbreviated as a-Si) that is a semiconductor layer. From the graph of FIG. 13, the photosensitivity of the sensor element can be increased by increasing the thickness of the a-Si film, and the S / N ratio of the contact image sensor can be improved. Further, it is found that the thickness of the semiconductor layer is preferably at least 3000 angstroms or more, and more preferably about 6000 angstroms in order to secure practical photosensitivity as a sensor element. On the other hand, regarding the TFT element, when the a-Si film thickness is increased, the on-resistance tends to significantly increase particularly in the region where the drain-source voltage is low. The cause of this is explained as follows. That is, in the TFT element shown in FIG. 12, the on-current passes from the impurity semiconductor layer 24 of the drain electrode through the thickness direction of the semiconductor layer 23, reaches the channel at the interface between the semiconductor layer 23 and the gate insulating layer 22, and then the semiconductor layer again. Since the impurity semiconductor layer 24 of the source electrode flows through the film thickness direction of the semiconductor layer 23, a non-linear resistance component in the film thickness direction of the semiconductor layer 23 exists in the path of the ON current. This nonlinear resistance component increases as the a-Si film thickness increases. Therefore, the overall on-resistance also increases as the a-Si film thickness increases. Such an increase in the on-resistance of the TFT element causes a decrease in the drive capability of the load, especially for the TFT element forming the drive circuit 5. Generally, in order to speed up the operation of the TFT element for the driving circuit, it is necessary to reduce the overlap capacitance between the gate electrode, the drain and the source electrode as much as possible. Therefore, the nonlinear resistance component increases as the overlap area is reduced. Therefore, the on-resistance further increases. Further, if the size of the TFT element is increased in order to increase the driving capability, the regulation capacity of the TFT element also increases, and the response speed of the drive circuit also decreases.
As described above, in the conventional contact image sensor, increasing the photosensitivity of the sensor element and decreasing the on-resistance of the TFT element have a trade-off relationship.

Therefore, in order to satisfy these conditions at the same time, it is conceivable that the on-current path does not pass through the semiconductor layer 23 in the film thickness direction. A TFT device having such a structure is described in Technical Bulletin of IEICE, 19
In February 1994, it was reported on pages 13-18 and a patent application has been filed (Japanese Patent Application Laid-Open No. 5-226656). That T
A sectional view of the FT element is shown in FIG. Figure 14 (a) shows TF
This is a pixel TFT of a T-LCD, and FIG. 14B is a drive circuit TFT. Referring to FIG. 14, the drive circuit T
To manufacture the FT, first, the gate electrode 21 is formed on the glass substrate 20 and patterned, and this is anodized and covered with the anodized film 41. Next, the gate insulating layer 22 and the first amorphous semiconductor layer 42 are deposited by plasma CVD. Next, the above-mentioned amorphous semiconductor layer 42 is irradiated with an excimer laser to be converted into a polycrystalline semiconductor layer 43, and then a second amorphous semiconductor layer 44 is deposited. Then, the second-layer amorphous semiconductor layer 44 and the first-layer amorphous semiconductor layer 42 are patterned. Further, after the impurity semiconductor layer 24 and the source / drain electrode 25 are sequentially deposited, the source / drain electrode 25 is patterned, and finally a predetermined portion of the impurity semiconductor layer is removed.

[0013]

In the TFT manufacturing method described in the above-mentioned technical report and publication, excimer laser annealing is used to improve the mobility of the TFT element. However, under the present circumstances, variations in mobility are likely to occur due to uneven annealing. This is also mentioned as an issue in the above-mentioned technical bulletin. Further, since the excimer laser annealing device used in the manufacture of the above-mentioned TFT element performs annealing while scanning the laser spot, not only the manufacturing throughput is bad, but also the device itself is effective. As a result, this leads to an increase in product cost.

By the way, the TFTs described in the above-mentioned technical bulletins and gazettes are supposed to be applied to a TFT-LCD, but the present invention is premised on an application to a contact image sensor. Therefore, the operation performance of the TFT element necessary for realizing the application to these is considered. First, T
Regarding the FT-LCD, when it is attempted to display a 480-line moving image used in a notebook personal computer or the like in 16 gradations, the load capacity per line is about 200.
The ON resistance value of the drive circuit required to drive pF in the address time of about 35 μs is about 63 kΩ. On the other hand, the contact image sensor, assuming a general facsimile application, has a reading width of B4 size and a resolution of 8d.
ot / mm, reading time 5 ms / line, 16 gradations,
If it is divided into 64 blocks, load capacity 50pF is about 80
The ON resistance value of the drive circuit required to drive in the address time of μs is about 580 kΩ.

As described above, when the application to the contact image sensor is considered, the drive capability required of the drive circuit is
It is about 1/10 of the application to the TFT-LCD. That is, the TFT element manufactured by the manufacturing method described in the above-mentioned Technical Bulletin and the above publication has a problem that the manufacturing cost is increased although the required performance is sufficient in terms of operation speed. Become.

In view of the above problems, the object of the present invention is to use a TFT element in a drive circuit to drive a TF for drive.
A contact image sensor in which a T element, a sensor element, and a transfer TFT element are integrally formed on the same substrate, and the characteristics required for a driving TFT element can be obtained without using a manufacturing method that requires laser annealing. An object of the present invention is to provide a contact image sensor that can be applied and has excellent economical efficiency.

[0017]

A contact image sensor according to the present invention is a photoelectric conversion device in which a circuit including a sensor element for photoelectric conversion and a switch element connected thereto is used as a unit and arranged in a plurality of column lines. A matrix drive type contact image sensor comprising at least a conversion unit and a drive circuit for matrix-driving the photoelectric conversion unit, wherein transistors constituting the switch element and the drive circuit are insulated gate thin film transistors. In the contact image sensor having the structure in which the photoelectric conversion unit and the driving circuit are integrated on the same insulating transparent substrate by the same manufacturing process, at least the driving circuit of the two types of thin film transistors is configured. The thin film transistor includes a gate electrode, a gate insulating layer, and the gate insulating layer on the insulating transparent substrate. A semiconductor layer forming a channel corresponding to the gate electrode on the surface, and an impurity semiconductor layer forming a drain region serving as a current inflow point into the channel and a source region serving as a current outflow point from the channel with respect to the semiconductor layer An inverted staggered type in which and are stacked in this order, or a transistor having a staggered type structure that is stacked in the reverse order, wherein the semiconductor layer is formed of layers stacked in a predetermined thickness by only one deposition operation, It has a single-layer structure having no discontinuity in its thickness direction, and is characterized in that the impurity semiconductor layer is in contact with both ends of the channel.

[0018]

Next, a preferred embodiment of the present invention will be described with reference to the drawings. In some embodiments described below, the circuit configuration is the same as the circuit diagram of the conventional contact image sensor shown in FIG. 10, and each functional block and each circuit element in the sensor substrate are planar. The arrangement is almost the same.

First, matters common to the respective embodiments will be described with reference to FIG. The circuit shown in FIG. 10 is a circuit of a contact image sensor in which a sensor element, a transfer switch element, and a drive circuit are integrated and formed in one sensor substrate, and a frame surrounded by a broken line in the drawing shows the inside of the sensor substrate. Circuit. M × n sensor elements 1 are arranged in the document reading width direction, and a storage capacitor 2 and a transfer TFT element 3A are connected to each of these sensor elements. The driving TFT element 4A constitutes a driving circuit with the transistors Q ₁₁ , Q ₁₂ , and Q ₁₃ . When light is incident on the sensor element 1, a photocurrent is generated and the electric charge is stored in the storage capacitor 2. The transfer TFT is driven by the driving TFT element Q13.
The original reading operation is performed by turning on the element 3A, taking out the electric charge accumulated in the storage capacitor 2 to the read wiring 61, and detecting it by the detection IC 16.

In the embodiments described below, an example of the structure of the driving TFT element and the transfer TFT element in the circuit shown in FIG. 10 and the manufacturing process for realizing the structure will be mainly described.

(Embodiment 1) FIG. 1 is a sectional view of a sensor substrate in a contact image sensor according to a first embodiment of the present invention. In this embodiment, the structure of the TFT element is mainly different from that of the conventional contact image sensor shown in FIG. That is, comparing FIG. 1 and FIG. 12D, in the present embodiment, the read wiring 61, the sensor element and the TF.
The impurity semiconductor layer 2 is provided between the gate insulating layer 22 and the second electrode layer 25 serving as the source and drain electrodes of the T elements 3B and 4B.
4 is interposed, the second electrode layer 25 is in direct contact with the gate insulating layer 22 in the conventional contact image sensor. Focusing on the transfer TFT element 3B and the driving TFT element 4B in this embodiment, both TFT elements have both ends of a channel formed at the interface between the gate electrode (consisting of the first electrode layer 21) and the semiconductor layer 23. The impurity semiconductor layer 24 forming the source region and the drain region is in contact therewith. In other words, the source regions and drain regions of the TFT elements 3B and 4B are the semiconductor layer 2
3 is formed not only on the upper surface of the semiconductor layer 23 but also along the side wall in the thickness direction of the semiconductor layer 23, and the channel and the second electrode layer 25 are directly connected to each other by the low resistance source region and drain region. Become. On the other hand, the conventional TFT
In the elements 3A and 4A, there is no impurity semiconductor layer between the channel and the source and drain regions on the upper surface of the TFT element. That is, the channel and the second electrode layer 25 are connected to each other with the current path in the thickness direction of the high resistance semiconductor layer 25 interposed therebetween.

FIG. 2 shows a cross section of the contact image sensor substrate of this embodiment in the order of manufacturing steps, taken along the line Aa in the plan view of the sensor substrate shown in FIG. To manufacture this embodiment, first, the first electrode layer 21 made of an opaque metal such as Cr or Al is deposited on the glass substrate 20 by a method such as sputtering, and then patterned by a method such as photolithography. By doing so, a gate electrode is formed (FIG. 2A).

Then, by a method such as plasma CVD,
A gate insulating layer 22 made of silicon nitride or the like is deposited, and a semiconductor layer 23 made of amorphous silicon is further deposited to a thickness of about 5000 Å. Then, after patterning the semiconductor layer 23, a contact hole is formed in the gate insulating layer 22 (FIG. 2B).

Subsequently, the impurity semiconductor layer 24 is deposited by a method such as plasma CVD, and the second electrode layer 25 made of an opaque metal such as Cr and Al is further deposited by a method such as sputtering. Then, the second electrode layer 25 is patterned to form source / drain electrodes, capacitor electrodes, and wiring (FIG. 2C).

Next, after removing the impurity semiconductor layer 24 in the back channel portion of the sensor element 1, the transfer TFT element 3B, and the TFT element 4B for the drive circuit 5 by etching, a protective insulating layer 26 is deposited on the entire surface of the substrate.

2 and 12, the manufacturing process of this embodiment is compared with the manufacturing process of a conventional contact image sensor. In this embodiment, the gate insulating process is performed in the process shown in FIG. 2B. After the layer 22 is deposited, first, only the semiconductor layer 23 is deposited, and immediately thereafter, the semiconductor layer 23 is patterned. Then, in a step shown in FIG. 2C, the impurity semiconductor layer 24 and the second electrode layer 25 are successively deposited,
First, a pattern is formed on the second electrode layer 25. And
In the step shown in FIG. 2D, the impurity semiconductor layer 24 is patterned using the pattern of the second electrode layer 25 as a mask. As a result, the impurity semiconductor layer 24 having the same pattern is formed below the pattern of the second electrode layer 25.

On the other hand, in the conventional contact image sensor, after the gate insulating layer 22 is deposited in the step shown in FIG. 12B, the semiconductor layer 23 and the impurity semiconductor layer 24 are successively deposited thereon. Then, the semiconductor layer 23 and the impurity semiconductor layer 24 are simultaneously patterned. Therefore, the semiconductor layer 23 and the impurity semiconductor layer 24 have the same pattern. After that, in a step shown in FIGS. 12C and 12D, the second electrode layer 25 is deposited and a pattern is formed on the second electrode layer 25. As a result, the second electrode layer 25 comes into direct contact with the gate insulating layer 22 without interposing the impurity semiconductor layer 24 therebelow.

FIG. 3 compares the ON resistance characteristics of the TFT element according to this embodiment with the conventional TFT element shown in FIG.

Referring to FIG. 3, particularly in a region where the drain-source voltage is low, that is, V _ds = 0.01 to 1 V, the on-resistance of the TFT device according to this embodiment is about 10 kΩ.
Is constant, and the on-resistance of the conventional TFT is 120k to 10k.
Compared with MΩ, it was 1/12 to 1/1000, and the resistance could be significantly reduced.

As described above, when the TFT element of this embodiment is used in the driving circuit, the size of the driving TFT element is such that the gate width W is W = 1 in the above-mentioned use for the facsimile.
This is 000 μm, which is about 1/9 of the device size in comparison with the case where the conventional TFT device has a gate width of W = 8700 μm. in this case,
The electrode overlap capacitance of the TFT of this embodiment is about 14p.
F. From this, it is clear that if the drive circuit is constructed by the TFT element according to the present embodiment, a circuit having sufficient response characteristics for use in the above-mentioned facsimile application can be constructed.

(Embodiment 2) FIG. 4 is a sectional view showing a cross section of a contact image sensor substrate according to a second embodiment of the present invention in the order of manufacturing steps. The cross section of the substrate is shown in the plan view of the sensor substrate shown in FIG. It is shown by the section Aa. Comparing the transfer TFT element 3C shown in FIG. 4D with the transfer TFT element 3B shown in FIG. 1, the following points are different between the present embodiment and the first embodiment. There is. That is, in the transfer TFT element 3B of the first embodiment, the impurity semiconductor layer 24 is connected to both ends of the channel formed at the interface between the gate insulating layer 22 and the semiconductor layer 23 along the sidewall of the semiconductor layer 23. On the other hand, in the transfer TFT element 3C of this embodiment, the impurity semiconductor layer 2 is formed.
4 is formed only on the upper surface of the element. That is, in the TFT element 3C of the present embodiment, the inflow and outflow of the on-current are
Limited to the top surface of the device only. Therefore, in the case of this embodiment, the semiconductor element 23 is provided in the on-current path of the TFT element 3C.
Since the non-linear resistance component in the thickness direction enters in series, the on-resistance increases, but on the other hand, the off-leakage current can be reduced.

By the way, in the case of a device using wirings connected in a matrix as seen in the application of the present invention, crosstalk due to a leak current from a non-selected block tends to be a problem in a transfer TFT element. In the circuit diagram shown in FIG. 10, when the m-th block is selected, the remaining m-1 blocks are in the non-selected state.
Especially in the case of an image original where the read signal of the selected block is small and the read signal of the non-selected block is large,
If the off-leakage current of the transfer TFT element of the non-selected block is large, the leak current is superimposed on the read signal of the selected block through the read wiring, and the output signal becomes gray even though the black original is read. turn into.

Therefore, according to this embodiment,
It is possible to realize a device less affected by the leak current without changing the manufacturing process of the sensor substrate.

FIG. 6 shows the relationship between the photocurrent of the sensor element and the on-resistance of the TFT element and the a-Si film thickness of the semiconductor layer, which was evaluated in the first or second embodiment described above. It is a graph shown. Referring to FIG. 6, the photocurrent of the sensor element increases as the thickness of the a-Si film increases,
It was found that the photocurrent reached its maximum when the a-Si film thickness was about 6000 angstroms, and the photocurrent was rather reduced even when the a-Si film was further thickened. Further, it was confirmed that the on-resistance of the TFT element did not depend on the a-Si film thickness and maintained a low resistance. On the other hand, from the viewpoint of the manufacturing process, there is a problem that film peeling occurs when the a-Si film thickness is 10,000 angstroms or more. Therefore, a-
The Si film thickness is 50 as in the first and second embodiments.
Not limited to 00 angstroms, 3000
It is desirable that the thickness is about 10,000 angstroms, and the high-speed contact image sensor according to the present invention can be realized.

Although amorphous silicon is used as the semiconductor layer in the above-mentioned first and second embodiments, it is not necessary to limit to this, and polycrystalline silicon can be formed without performing the laser annealing step. If possible, it is possible to realize a low-cost contact image sensor, which is the object of the present invention. However, as shown in FIG. 7, when the polycrystalline silicon is used for the TFT element, the leak current increases with the crystal grain size. Therefore, in the contact image sensor according to the present invention, this leak current is generated especially in the switch element. The above-mentioned problem of crosstalk is likely to occur. Further, when actually forming polycrystalline silicon, the manufacturing cost of the contact image sensor is high because the manufacturing apparatus is more expensive than the case of using amorphous silicon. Therefore, it is possible to realize the low-cost contact image sensor according to the present invention, preferably by using amorphous silicon as the semiconductor layer.

(Third Embodiment) In the first and second embodiments described above, the transfer TFT element and the drive circuit TF are used.
Although the inverted stagger type TFT element is taken as the T element, the invention is not limited to this, and it can be realized by using a forward stagger type TFT element. However, in the contact image sensor, as shown in FIG. 8, the light source 83 is arranged on the back surface of the sensor substrate 82. Therefore, in the forward stagger type TFT element, light from the light source is incident on the side opposite to the gate electrode, that is, the back channel side, so that a light leak current occurs and the above-described crosstalk problem occurs. Therefore, in order to prevent this, a method of forming a light-shielding film under the back channel of the TFT element is taken, but this light-shielding film must be formed in a step different from that of the TFT element, such as pattern formation. The number of steps is increased, resulting in an increase in cost, and the effect of the present invention cannot be fully exhibited. From the above, the transfer TF
As the T element and the driving circuit TFT element, it is desirable to use an inverted stagger type TFT element.

[0037]

As described above, according to the present invention, the structure of the TFT element forming the driving circuit of the contact image sensor, in particular, is formed at the interface between the gate insulating layer and the semiconductor layer corresponding to the gate electrode. The source and drain impurity semiconductor layers are in contact with both ends of the channel.

Therefore, according to the present invention, it is necessary to apply this to a TFT element and a contact image sensor without using laser annealing which causes characteristic variations and requires an expensive apparatus. It is possible to provide a contact image sensor at a low cost and at a high speed, since it is possible to provide such characteristics.

[Brief description of the drawings]

FIG. 1 is a sectional view of a contact image sensor substrate according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a cross section of the contact image sensor substrate according to the first embodiment in the order of manufacturing steps.

FIG. 3 shows the source-drain voltage dependence of on-resistance in a TFT device according to the first embodiment of the present invention.
It is a figure which compares and shows an element and the TFT element by the prior art.

FIG. 4 is a view showing a cross section of a contact image sensor substrate according to a second embodiment of the present invention in the order of manufacturing steps.

FIG. 5 is a plan view of a contact image sensor substrate according to a second embodiment.

FIG. 6 is a-Si of the photocurrent of the sensor element and the on-resistance of the TFT element according to the first embodiment or the second embodiment.
It is a figure which shows the dependence with respect to a film thickness.

FIG. 7 is a diagram showing a relationship between a leak current of a TFT element and a crystal grain size of a semiconductor layer.

FIG. 8 is a diagram showing a cross-sectional structure of a contact image sensor.

FIG. 9 is a circuit diagram of a sensor substrate in a contact image sensor using an IC as a drive circuit.

FIG. 10 is a circuit diagram of a sensor substrate in a contact image sensor in which a drive circuit is integrated on the sensor substrate.

11 is a plan view of the sensor substrate shown in FIG.

FIG. 12 is a diagram showing a cross section of the sensor substrate shown in FIG. 11 in the order of manufacturing steps.

FIG. 13 is a diagram showing the dependence of the photocurrent of the sensor element and the on-resistance of the TFT element on the a-Si film thickness according to the conventional technique.

FIG. 14 is a cross-sectional view of another example of a conventional TFT device.

[Explanation of symbols]

 1 Sensor Element 2 Storage Capacitance 3A, 3B Transfer TFT Element 4A, 4B Driving TFT Element 5 Driving Circuit 6 Lighting Window 20 Glass Substrate 21 First Electrode Layer 22 Gate Insulating Layer 23 Semiconductor Layer 24 Impurity Semiconductor Layer 25 Second Electrode Layer 26 Protective Insulating Layer 41 Anodized Film 42 First Amorphous Semiconductor Layer 43 Polycrystalline Semiconductor Layer 44 Second Amorphous Semiconductor Layer 50 Driving IC 51 Driving Wiring 60 Detection IC 61 Read Wiring 81 Housing 83 Light source 84 Mounting board 85 Image original 86 Platen roller 100, 110 Sensor board

Claims (6)

[Claims] 1. A photoelectric conversion unit formed by arranging a circuit including a photoelectric conversion sensor element and a switch element connected thereto in a plurality of column lines, and the photoelectric conversion unit is matrix-driven. A matrix drive type contact image sensor including at least a drive circuit for driving the switch element and the drive circuit, wherein the transistors forming the switch circuit are insulated gate thin film transistors, and the photoelectric conversion unit and the drive circuit are provided. In the contact image sensor having a structure in which and are integrated on the same insulating transparent substrate by the same manufacturing process, at least one of the two types of thin film transistors, which constitutes a drive circuit, has a gate electrode on the insulating transparent substrate. And a channel corresponding to the gate electrode is formed at the interface between the gate insulating layer and the gate insulating layer. An inverted staggered type in which a semiconductor layer that forms a drain region that serves as a current inflow point into the channel and a source region that serves as a current outflow point from the channel with respect to the semiconductor layer are stacked in this order, A transistor having a staggered structure laminated in the reverse order, wherein the semiconductor layer is a layer laminated to a predetermined thickness by only one deposition operation, and has no discontinuity in the thickness direction. A contact image sensor having a single-layer structure, wherein the impurity semiconductor layer is in contact with both ends of the channel. 2. The contact image sensor according to claim 1, wherein the switch element of the photoelectric conversion unit is formed of the thin film transistor having the structure according to claim 1. 3. The contact image sensor according to claim 1, wherein the thickness of the semiconductor layer forming the thin film transistor is 30.
A contact image sensor having a thickness of 00 to 10,000 angstroms. 4. The contact image sensor according to claim 1, wherein a semiconductor layer forming the thin film transistors of the sensor element, the switch element and the drive circuit is made of amorphous silicon. Contact image sensor. 5. The contact image sensor according to claim 1, wherein the switch element of the photoelectric conversion unit and the thin film transistor of the drive circuit are reverse stagger type thin film transistors. 6. A metal layer is deposited on the transparent insulating substrate,
A first patterned gate electrode including a gate electrode
A step of forming an electrode layer, and sequentially stacking a gate insulating layer and a semiconductor layer on the transparent insulating substrate on which the first electrode layer has been formed, and then, only on the semiconductor layer, on the gate electrode Patterning leaving a predetermined portion including: an impurity semiconductor layer made of a semiconductor layer doped with impurities and a second metal layer on the transparent insulating substrate after the semiconductor layer has been patterned. And then sequentially depositing the second
Forming a second electrode layer by patterning only a first metal layer, leaving a predetermined portion including a portion to be a source region or a drain region overlapping with the semiconductor layer on the gate electrode, and the impurity Removing a portion of the semiconductor layer exposed from the second electrode layer to a depth reaching at least the semiconductor layer on the gate electrode.
A method for manufacturing the contact image sensor according to [1].