JPS63119260A - Picture reader and manufacture of the same - Google Patents

Abstract

PURPOSE:To reduce electrode areas significantly and improve the yield from a unit substrate by more than 5 times by a method wherein semiconductor layers of photosensors and semiconductor layers of thin film transistors which constitute analog switches and shift resisters which drive the photosensors successively are made of material of a specific composition and formed on a same substrate. CONSTITUTION:Semiconductor layers 6 of thin film transistors which are made of material which is composed of at least two components among CdS, CdSe and CdTe and has the same composition as the material of semiconductor layers 3 of photosensors and can be formed and processed simultaneously are formed on an insulating substrate 1 and on gate insulating layers 18 which are made of SiO2, Al2O3, Ta2O5 or the like and are formed on gate electrodes 17 which are made of Cr, Al, Ta or the like. Source electrode 15 and drain electrodes 16 which are made of Al, Cr, In, Au or the like are formed on the semiconductor layers 6. If necessary, contact holes 7 which facilitate connection with other devices are provided. The area occupied by a photosensor part 2, an analog switch part 4 and a shift register part 5 can be very small and the number of electrodes which send signals to the outside can be significantly reduced to about 6 totally including voltage application terminals 8.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an image reading device having a one-to-one size with respect to a document, which is used as an input device for various office automation equipment such as a facsimile machine, and a method for manufacturing the same.

2. Description of the Related Art Conventionally, in this type of image reading device, the first
The configuration is shown in the perspective view of FIG. That is, a semiconductor layer 3 of an optical sensor made of a Cd5-CdSe solid solution is formed in a line in the main scanning direction on a glass substrate 1 with an element density of 8 elements Amn5 pages or more, and is placed in a semi-closed container in a cdC12 atmosphere at 6oO Heat treat at ~6oO<0>C. After that, in order to extract a signal, a common electrode 29 in which the semiconductor layers 3 of the optical sensors are grouped together in a certain number of units and individual electrodes 30 corresponding to the semiconductor layers 3 of each optical sensor are formed. By connecting the individual electrodes 3o in the same order with the connection portion 31 of the flexible cable 32 in an IJ sock-like connection, a signal is output to the outside.

Specifically, as shown in the circuit shown in FIG. 14, while the common side switches 33 are sequentially turned on, the individual side switches 34 are sequentially moved. By repeating this scanning for each common electrode 19, a signal photoelectrically converted in the semiconductor layer 3 of each optical sensor is read as a voltage generated in the load resistor 36.

Problems to be Solved by the Invention However, in the image reading device having the above configuration, only the semiconductor layer 3 of the optical sensor and the matrix wiring section consisting of the flexible cable 32 are formed on the same substrate. The drive circuit for the side signal reading switch 33, 34, etc. is externally connected to the I
It is composed of C, etc. For example, an A4 with a semiconductor layer 3 of a photosensor of 1728 elements formed at a rate of 8 elements/m.
A format image reading device requires a very large number of extraction electrodes, 64 common electrodes and 32 individual electrodes, 86 in total.

Furthermore, since a flexible cable is used, the wiring pitch cannot be made finer, and for example, the width in the sub-scanning direction is required to be about 25M, and the width of the semiconductor layer 3 of the optical sensor in the sub-scanning direction is about 100 μm. If you think about it, most of the board is occupied by the wiring section, which poses a problem in the utilization efficiency of the board and in turn, in mass production.

Furthermore, if the electrical signal is minute due to the optical sensor structure,
Stray capacitance caused by long wiring with flexible cables limits high-speed driving and makes it impossible to increase the reading speed.

On the other hand, in order to solve the above problems, a method has been considered in which a thin film transistor (hereinafter abbreviated as TPT) using Cd's is generally formed on the same substrate. Problems due to increase in the number of processes caused by different semiconductors and differences in processing conditions for each semiconductor layer and interactions occurring during processing have a large influence, making it difficult to control process conditions. Further, the Cd5e TFT itself cannot be controlled to have arbitrary characteristics due to compositional deviation due to vapor pressure difference and difficulty in controlling defects. Furthermore, the temperature characteristics are poor due to the many levels of traps, etc., and it is difficult to obtain uniform characteristics over a large area by heat treatment alone.

Means for Solving the Problems In order to solve the above problems, the present invention provides that the semiconductor layer of the optical sensor and the semiconductor layer of the TPT constituting the analog switch and shift register that sequentially drive the optical sensor have the same composition. Furthermore, I[-Vl group compound semiconductors containing the same impurity, particularly CdS and CdSe.

The problem can be easily solved by using a solid solution of CdTe or at least two of them, or by using a semiconductor layer containing impurities such as Cu or C7l in the solid solution.

Function The present invention can greatly reduce the number of processes by forming the semiconductor layer of the optical sensor and the semiconductor layer of the TPT using the same material and composition, and by simultaneous processing, and also can be made mutually compatible due to the same processing conditions. This completely eliminates the impact on Furthermore, since the drive circuit is incorporated using TPT on the same substrate, the number of electrodes taken out to the outside can be reduced to just a few, and the electrode area can also be formed using a photolithography process, making it possible to reduce the area to less than the conventional method. can. In terms of reading speed, stray capacitance due to unnecessarily long wiring can be reduced by providing a drive circuit near the optical sensor, allowing high-speed drive.

In addition, by making the semiconductor layer of TPT a solid solution film, it is possible to control defects, and in particular, it is possible to increase the stability of temperature characteristics by expanding the band gap, and by introducing impurities such as Cu and CAi, it is possible to increase the ON current of pTFT. A sufficient ON-OFF ratio can be obtained, and the uniformity can be further improved.

Example The first embodiment of the present invention will be described below from Fig. 1 to page 69. This will be explained using figures.

FIG. 1 is a partial plan view of an image reading device according to a first embodiment of the present invention. This image reading device includes an optical sensor section 2 formed on an insulating substrate 1 such as glass, an analog switch section 4 for reading signals from each optical sensor 3, a shift register section 5 for driving each analog switch, and an external It consists of a lead-out electrode part and a lead-out electrode part. 6a to 6q are
It is a TPT that drives one element of the photosensor.The shaded area indicates the semiconductor layer 6, and the source and drain electrodes are on both sides thereof. Specifically, the structure of the TPT is shown in the plan view of FIG. 2 and the cross-sectional view of FIG. 3. That is, CdS and CdSe are formed on the insulating substrate 1.

The semiconductor layer 6 of TPT, which is made of CdTe or at least two of them and has the same composition as the semiconductor layer 3 of the optical sensor and can be formed and processed simultaneously, is made of, for example, CdTe.
r, AI! , a thin film formed on the gate electrode 17 such as Ta,
For example, SiO2, A12o3. Formed on the gate insulating layer 18 such as T&206. On top of that, A#, Cr, In
A source electrode 15 and a drain electrode 16 are formed of , Au, etc., and a contact hole 7 is provided as necessary to enable connection with other elements. This means, for example, that a material having the same composition as the semiconductor layer 3 of the optical sensor consisting of a Cd5-CdSe solid solution, and a CdCl
This is based on the discovery that even a film treated in an activation heat treatment step at 5oO to 6oO<0>C in a 2 atmosphere has sufficient TPT characteristics. This specific reading method is explained in the 6th section.
As shown in the cross-sectional view of the figure, light from a light source 19 such as an LED is irradiated onto the document 2°, and the reflected light is transmitted to the focusing fiber array 21.
The image is formed on the optical sensor 3 of the image sensor section 22, and the TP
It is read by the drive circuit of T.

As shown in FIG. 1, the area occupied by the optical sensor section 2, analog switch section 4, and shift register section 5 is, for example, T.
Even if the dimensions of the PT are approximately 50 μm×10 μm, it will be extremely small. Furthermore, there are a total of 6 electrodes for outputting signals to the outside, including an applied voltage terminal 8, a ground terminal 9, a signal output terminal 10, and shift register drive pulse input terminals 11 to 13.
This can be significantly reduced to about a book.

11 FIGS. 4 and 5 are an equivalent circuit diagram of the image reading device and a timing chart at each read terminal, respectively. The shift register section 5 turns on the TPT of the analog switch 6a using the two-phase clocks φ1 and φ2, and transfers the pulse input to IN as an input signal to the next stage shift register. analog switch 6
When a is turned on, a voltage Vα is generated across the external load resistor 14 by a signal photoelectrically converted by the optical sensor 3.
This is to read the bar as an image signal.

In this way, by configuring the semiconductor layer of the optical sensor and the semiconductor layer of the analog switch and shift register made of TPT to be made of the same material and formed and processed simultaneously, the number of external lead-out terminals can be significantly reduced. Furthermore, it is possible to significantly reduce the area occupied by the electrode portion, which was conventionally required.

Furthermore, compared to the large increase in the number of processes required when different materials are used, this can be achieved with the same number of processes as just the optical sensor section, dramatically improving productivity and reliability while reducing costs. It is.

Below, the manufacturing method in the first embodiment of the present invention will be explained in the seventh embodiment.
This will be explained in detail using figures.

As shown in Figure 7(,), in order to remove thermal strain in advance,
Or and Ta were deposited on an insulating substrate 1 such as Corning 7059 Terrace, which had been heat treated at 50°C and cleaned.

Al or the like is deposited by a vacuum evaporation method, an electron beam method, or the like, and a gate electrode 17 is formed in a predetermined shape and position by a lift-off method, a photoetching method, or the like. Next, as shown in FIG. 7(c), at least the gate electrode 17 is covered with Si.
o2. Sputtering of AlI2O3, Ta205°S i3N4, etc., electron beam method.

With plasma CVD method, ECR method and anodic oxidation method, several hundred
~1000 people, preferably 500-5000 people. After that, as shown in FIG. 7(C), the gate electrode 17
A contact hole 7 is formed in a tapered shape using an etching method or a lift-off method for connection with the contact hole 7. This is to prevent the electrode from breaking. Furthermore, Figure 7 (d
), the semiconductor layer 3 of the optical sensor and the semiconductor layer 6 of TPT. For example, 0.1mol of Cu as an impurity
A Cd5-13 beno-Cd's solid solution film containing approximately 100% of Cd5-13 benoCd's is made into a film of several 100 to several 1000%, specifically, a film of approximately 5000% that can obtain the photosensitivity of an optical sensor and the characteristics of TPT at the same time. It is deposited thickly by vacuum evaporation, electron beam or sputtering. Next, as shown in FIG. 7(e), the semiconductor layer 3 of the optical sensor, the TPT semiconductor layer 6a of the analog switch section 4, the TPT semiconductor layer 6b of the shift register section 5, etc. are formed by photolithography. Using one photomask, place the
After patterning the shape, it contains impurity Cl,
For example, Cd (500 to 60σ in a semi-closed container with J2 atmosphere)
Activation heat treatment is performed at C. This provides stability in film quality through doping with J impurities and recrystallization, and also imparts photosensitivity to the photosensor. Here, Cd5- containing Cu and C1l as impurities is Cd
Although Se solid solution has been described, it is not limited to Cd5-CdSe (Cd5-CdTe, etc.).

Solid solution impurity C1f such as Cd5-Cd5e-CdTe
It goes without saying that a film or a doped film may be used, but a film doped with impurities is especially suitable for photosensor 14.
This is mentioned because it can easily satisfy the characteristics of both Henosa and TFT.

Next, as shown in FIG. 7(f), the connection electrode is connected to the optical sensor,
7NiCr-Au, Cr, A, L? were formed at predetermined positions using the Otolithography method or soft-off method to interconnect analog switches and shift registers. , In, etc. Although not shown in FIG. 7, a protective layer is finally formed of polyimide or the like.

According to the above manufacturing method, since the semiconductor layer of the optical sensor and the semiconductor layer of the TPT are made of materials with the same composition and are formed and processed simultaneously, the process is faster than when using different compositions and materials. The number can be significantly reduced, productivity can be improved, and characteristics can be easily made uniform. Additionally, Cu is added as an impurity.

Since the Cl-doped film undergoes recrystallization through the activation heat treatment during Cβ doping, the properties caused by the interface state of TPT are significantly improved. moreover,
By forming a solid solution film, it is easy to adjust the spectral sensitivity, and a wider bandgap can be obtained than in the conventional Cd5e TFT, and the safety against temperatures of 15V is improved.

Next, a second embodiment of the present invention and its manufacturing method will be described using FIG.

8, the difference from FIG. 3 is that the gate insulating layer 18 has a multilayer structure, and the insulating layer 19 in contact with at least the semiconductor layer 3 of the optical sensor and the semiconductor layer 6 of the TPT is made of a material having a thermal expansion coefficient as described above. For example, Cd5-CdS
In the case of e solid solution, it can be easily formed by sputtering Corning 7o59 glass or the like. Here, the fact that the coefficients of thermal expansion are about the same means that the thermal expansion coefficients are at a level that will not cause racks in the semiconductor layer that would be detrimental to the properties during subsequent heat treatment.

With this multilayer structure, it is possible to stop thermal diffusion of the gate electrode material into the semiconductor layer during the formation of the gate insulating layer and the activation heat treatment, and it is also possible to prevent insulation defects due to pinholes and the like. Furthermore, it is possible to prevent cracks caused by differences in thermal expansion coefficients from diffusing into the semiconductor layer of the optical sensor and the insulating layer of the semiconductor layer material of TPT, thereby reducing interface defects and the like. Further stabilization and uniformity of characteristics can be achieved.

Next, a third embodiment of the present invention and its manufacturing method will be described using FIGS. 9 to 11.

As shown in the plan view of FIG. 9, the difference from the first embodiment shown in FIG. The structure and reading principle are different from the first embodiment. The specific structure is as shown in the partially enlarged view of FIG. 10 and the sectional view of FIG. 11.

The reading principle is that light 27 from a light source enters from the back surface of the transparent insulating substrate 1 through the illumination window 24, and in the case of a pitch of 8 elements/m+n, a transparent protective layer 26 of about 80 μm, such as micro sheet glass, is formed at regular intervals. The reflected light 28 on the surface of the original document 20, which is maintained at a constant level, is photoelectrically converted by the optical sensor 3, and read out by a drive circuit provided on the same substrate and constituted by a TPT. In addition, in the manufacturing method, when forming the gate electrode 17 shown in FIG. 7, at the same time a light shielding layer 25 having an illumination window 24 is formed by a photolithography method or a 17-page lift-off method, and then it is formed in the same manner as shown in FIG. 7, and finally, The transparent protective layer 26 that maintains the original 20 and the optical sensor 3 at a constant interval is made of, for example, Sio2 or A42o3°siN.
It may be formed by sputtering or electronic beam method using SiC, Sn◯21, or the like, or by pasting thin glass such as micro sheet glass.

By adopting the above-mentioned configuration, the focusing fiber array can be omitted, making it possible to achieve a very small size with a thickness of about one stroke, and to achieve a reduction in cost. In addition, when a conventional flexible cable is used, the flexible cable may be peeled off due to an original running on a transparent protective layer, and the drive circuit may be formed on the same substrate using TPT.
Reliability at the connection part can be easily obtained without any problems.

FIG. 12 shows a fourth embodiment of the present invention, which is
This is an application of the second embodiment to the third embodiment, and the resulting effect is one that takes both of them into account, and further achieves uniformity of characteristics, cost reduction, and ultra-miniaturization. It is.

18 Effects of the Invention According to the present invention, by forming a drive circuit consisting of an optical sensor and an analog switch consisting of a TPT and a shift register on the same substrate, it is possible to eliminate the problem that was conventionally used for connecting flexible cables. Since the electrode area can be significantly reduced to less than 100%, the yield from the same substrate can be increased by more than 5 times.

Furthermore, the semiconductor layer of the optical sensor and the TPT semiconductor, and thus the cost reduction, can be easily achieved with almost no decrease in yield. On the other hand, since there is no deterioration in the reliability of the connection part due to bonding when a flexible cable is used, the industrial advantage is immeasurable. Also,
The effect of impurity doping with Cu and C1j further increases stability and uniformity.

Furthermore, by making the insulating layer multi-layered, pinholes are eliminated, the number of cracks is reduced, etc., not only reliability but also productivity can be further improved.

Furthermore, by creating a structure that does not include a focusing fiber array, the effect of miniaturization and cost reduction is very large.

[Brief explanation of the drawing]

FIG. 1 is a plan view of an image reading device according to a first embodiment of the present invention, FIG. 2 is a plan view of the same thin film transistor, FIG. 3 is a sectional view thereof, and FIG. 4 is an equivalent circuit diagram of the image reading device. , 5th
4 is a timing chart showing the relationship between input and output in the circuit shown in FIG. 4, FIG. 6 is a reading configuration diagram of an image reading device according to the first embodiment of the present invention, and FIG.
FIG. 8 is a cross-sectional view of the image reading device according to the second embodiment of the present invention, and FIG. 9 is a cross-sectional view showing the method of manufacturing the image reading device according to the third embodiment of the present invention. FIG. 10 is an enlarged plan view of the optical sensor section in FIG. 9, FIG. 11 is a cross-sectional view showing the reading configuration of an image reading device according to the third embodiment of the present invention, and FIG. 12 is a plan view of the device. A sectional view of an image reading device according to a fourth embodiment of the invention, FIG. 13 is a perspective view of a conventional image reading device,
FIG. 14 is a diagram showing an equivalent circuit of FIG. 13. DESCRIPTION OF SYMBOLS 1... Insulating substrate, 2... Optical sensor section, 3... Optical sensor and semiconductor layer, 4...
...Analog switch section, 6...Shift register section, 5 B~6q...Thin film transistor, 1
7... Gate electrode, 18... Gate insulating layer, 2o... Original, 23... Insulating layer with equal expansion coefficient, 24...・Lighting window, 25...
... Light shielding layer, 26 ... Transparent protective layer, 28.
·····reflected light. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
Figure 4 Figure 5 A B □□ Vυrishijmr ^ ″.

Claims (9)

[Claims] (1) A group of optical sensors formed linearly on an insulating substrate,
The semiconductor layer of the photosensor group includes a thin film transistor group constituting an analog switch and a shift register formed on the insulating substrate to scan the photosensor group, and a connection electrode group between the photosensor group and the thin film transistor group. and the semiconductor layer of the thin film transistor group are made of a II-VI compound semiconductor material having the same composition and containing the same impurities. (2) A group of optical sensors formed on an insulating substrate, a gate electrode formed on the insulating substrate, a gate insulating layer existing at least on the gate electrode, and a semiconductor formed on the gate insulating layer a thin film transistor group consisting of a layer, a connection electrode between the photosensor group and the thin film transistor, a focusing fiber array, and a light source, the document is irradiated with the light source, and the reflected light is reflected by the focusing fiber array. An image reading device characterized by reading by a configuration that forms an image on a group of sensors. (3) A light-shielding layer and a gate electrode having an illumination window on a light-transmitting insulating substrate, a light-transmitting insulating layer present at least on the light-shielding layer and the gate electrode, and the light-shielding layer near the illumination window. a group of photosensors formed on the top, a group of thin film transistors formed on the gate electrode, a connection electrode between the group of photosensors and the group of thin film transistors, a transparent protective layer, and a light source; An image reading apparatus characterized in that the image reading apparatus is characterized in that the light from the light source is irradiated onto the document on the transparent insulating layer through the illumination window, and the reflected light is read by the optical sensor group. (4) The semiconductor layer of the photosensor group and the semiconductor layer of the thin film transistor group are CdS, CdSe, CdTe, or a solid solution consisting of at least two constituents thereof. The image reading device described in Section 1. (5) The image according to claim 3, wherein the semiconductor layer of the photosensor group and the semiconductor layer of the thin film transistor group contain Cu as an impurity and are films heat-treated in an atmosphere containing Cl. reading device. (6) A patent claim characterized in that the gate insulating layer and the light-transmitting insulating layer are made of multilayer films, and the layers in contact with the semiconductor layers of the optical sensor group and the thin film transistor group have approximately the same coefficient of thermal expansion. The image reading device according to item 3. (7) forming a gate electrode on the insulating substrate;
A step of forming a gate insulating layer existing at least on the gate electrode, a step of forming a contact hole, and a semiconductor layer of a photosensor group consisting of a group II-VI compound semiconductor layer having the same composition and containing the same impurities. An image characterized by comprising the steps of simultaneously forming a semiconductor layer of a group of thin film transistors constituting an analog switch and a shift register, simultaneously performing heat treatment, forming a connecting power source, and forming a protective layer. A method of manufacturing a reading device. (8) forming a light-shielding layer having an illumination window and a gate electrode on a light-transmitting insulating substrate; and forming a light-transmitting insulating layer existing at least on the light-shielding layer and the gate electrode. 8. A method of manufacturing an image reading device according to claim 7. (9) The method for manufacturing an image reading device according to claim 7, wherein the heat treatment step is performed in an atmosphere containing Cl.