JPH0337742B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a photoelectric conversion device that photoelectrically converts an optical information signal and outputs it as an electric signal.
In particular, the present invention relates to a solid-state photoelectric conversion device suitable for character and image input devices such as facsimiles, digital copying machines, and laser recording devices.

[Prior art and problems to be solved by the invention]

A conventional photoelectric conversion device includes a group of photoelectric conversion elements (pixels) that have a photoelectric conversion function, and a circuit that has a scanning function that sequentially extracts electrical signals output from the group of photoelectric conversion elements in a chronologically arranged form. photodiode and MOS/FET (Field
(abbreviated as "MOS type") or CCD
(Charge Coupled Device) and BBD (Backet
Brigade Device), so-called CTD (Charge Device)
There are various methods, such as those that include (abbreviated as ``CTD type'') a ``Transfer Device'' as a component.

However, since both MOS and CTD types use Si single crystal (abbreviated as C-Si) wafer substrates, the area of the light-receiving surface of the photoelectric conversion section is the same as the size of the C-Si wafer substrate. It ends up being limited. That is, at present, it is possible to manufacture C-Si wafer substrates with a size of several inches at most, including uniformity in the entire area. use
In a photoelectric conversion device whose components are MOS type or CTD type, its light receiving surface cannot exceed the size of the aforementioned C-Si wafer substrate.

Therefore, in a photoelectric conversion device having a photoelectric conversion section whose light receiving surface has such a limited and small area, when used as an optical information input device of a digital copying machine, for example, it is difficult to copy an optical system with a large reduction magnification. It is necessary to interpose an optical image of the document on the light receiving surface via the optical system.

In such a case, there are technical limits to increasing the resolution, as described below.

In other words, the resolution of the photoelectric conversion device is, for example, 10 lines/
mm, and the length of the light receiving surface in the longitudinal direction is 3 cm,
When attempting to copy an A4 size original, the optical image of the original formed on the light receiving surface is reduced to approximately 1/69, and the actual resolution of the photoelectric conversion device for the A4 original is approximately 1.5 lines/mm. It will decline and end. As described above, as the size of the original to be copied increases, the actual resolution decreases at the ratio of (size of light-receiving surface)/(size of original).

Therefore, in order to solve this problem, manufacturing technology that increases the resolution of the photoelectric conversion device is required in such a method, but it is difficult to use a manufacturing technology that increases the resolution of the photoelectric conversion device. In order to obtain the required resolution, devices must be manufactured with extremely high integration densities and with defect-free components, but such manufacturing techniques have their own limitations.

On the other hand, a plurality of photoelectric conversion devices are arranged so that the length in the longitudinal direction of all light-receiving surfaces is 1:1 with the length in the main scanning direction of the maximum size document that can be copied, and an optical image of the document to be imaged is formed. A method has been proposed in which the resolution is divided into a number of photoelectric conversion devices to avoid a substantial drop in resolution.

However, even in such a method, there are disadvantages as described below. In other words, when a plurality of photoelectric conversion devices are arranged, a boundary area where no light-receiving surface exists is inevitably created between each photoelectric conversion device, and when viewed as a whole, the light-receiving surface is no longer continuous and the image of the document is not formed. The optical image is divided, and the portion corresponding to the boundary area is not input to the light-receiving surface of the photoelectric conversion device, and the copied image corresponds to a line-shaped white spot or a line-shaped white spot. Parts are removed and combined into an incomplete product. Furthermore, since the optical image that is divided into multiple light-receiving surfaces and formed is an optically reversed image on each light-receiving surface, the overall image is different from the optically reversed image of the original image. . Therefore,
If the optical image formed on the light-receiving surface is reproduced as it is, the original original image cannot be reproduced.

As described above, in conventional photoelectric conversion devices, it has been extremely difficult to reproduce information with high resolution because the light receiving surface is small.

Therefore, there is a demand for a photoelectric conversion device having a photoelectric conversion section having an elongated light-receiving surface and excellent resolution. In particular, when applied to optical information input devices of facsimiles, digital copying machines, or other image reading devices that read characters and images written on originals, it is recommended to use a light-receiving surface that is approximately the same size as the original that is to be reproduced. A photoelectric conversion device equipped with a photoelectric conversion section that can faithfully reproduce a document without reducing the resolution required for a reproduced image is essential.

[Purpose of the invention]

The present invention has been made in view of the above points, and its object is to provide a photoelectric conversion section having an elongated light-receiving surface and having high resolution and high sensitivity. An object of the present invention is to provide a photoelectric conversion device that is extremely lightweight.

Another object of the present invention is to provide a solid-state photoelectric conversion device that uses polycrystalline silicon for the amplification means, can be easily made long, operates at high speed, and has a high amplification factor.

Another object of the present invention is to provide a low-noise solid-state photoelectric conversion device suitable for increasing length, which can compensate for variations in environmental characteristics of each element and prevent the influence of interference between elements.

The above-mentioned purpose is to connect a plurality of photoelectric conversion elements: each photoelectric conversion element is electrically connected, and a signal is amplified according to the signal output from the photoelectric conversion element according to the amount of light incident on the photoelectric conversion element. a plurality of semiconductor elements whose semiconductor layers are made of polycrystalline silicon as signal amplification means for outputting: a compensation means provided for each photoelectric conversion element and having a silicon semiconductor thin film for compensating the environmental characteristics of each photoelectric conversion element; A plurality of photoelectric conversion signal output units comprising: a plurality of crosstalk prevention means provided for each signal amplification means to prevent crosstalk between signals output from each signal amplification means; and a plurality of photoelectric conversion signal output units comprising: , unit drive wiring for transmitting a unit selection signal for exclusively selecting the plurality of signal amplification means for each unit, and a common signal for transmitting the output signal of the signal amplification means of the same rank in each unit. This is achieved by a solid-state photoelectric conversion device characterized in that the output wiring and the output wiring are integrally provided on the same substrate.

In particular, if the photoelectric conversion layer is formed of amorphous silicon, it will have excellent photoelectric conversion ability based on the light absorption coefficient.

Furthermore, in a preferred embodiment of the present invention,
The semiconductor portion having a photoelectric conversion function as a component constituting the photoelectric conversion element is a semiconductor thin film of amorphous silicon (hereinafter abbreviated as "A-Si") or polycrystalline silicon (hereinafter abbreviated as "poly-Si"). It consists of a semiconductor thin film (abbreviated as ")". In particular, in the present invention, the semiconductor portion of the signal amplification means is made of poly-
Since it is composed of a semiconductor thin film of Si, it is desirable that the semiconductor part of the photoelectric conversion element is also preferably composed of a thin semiconductor film of poly-Si, from the viewpoint of further improving productivity and mass production, and improving reliability. It is.

[Description of implementation examples]

The scanning circuit according to the present invention will be explained below. FIG. 1 shows a scanning circuit according to a first embodiment of the present invention. 1728 (54×
32) photoconductive elements S _1-0 to S _5-31 are powered by an external bias power supply V _B1 . Also, a compensation element W _1-0 as a compensation means, which is formed of the same material as the photoconductive element or has the same environmental characteristics (for example, temperature, humidity, etc.) and has characteristics to compensate for changes in the photoconductive element. ~W _54-31 is powered by an external bias power supply V _B2 . Therefore, the potential at the connection point between the photoconductive element and the compensation element takes a value compensated for the environmental conditions corresponding to the amount of light incident on the photoconductive element.

Amplification MOS as selectable signal amplification means
(or MIS) A common drain side wiring for every 32 transistors A _1-0 to A _54-31 , such as a block drive line.
If voltage is exclusively supplied to b ₁ , the amplification MOS (or MIS) transistor will be biased according to the potential of the connection point, and each amplification MOS
(or MIS) transistors each have a channel resistance that corresponds to the amount of light incident on the photoconductive element to which it is connected. Therefore, the photoconductive elements S _1-0 to S _1-31 are automatically transferred onto the individual data lines D ₀ to _{D 31} .
A signal current corresponding to the amount of incident light is output. It is obvious that in order to ensure the above operation, the individual data lines D ₀ to _{D 31} should be connected to a low impedance input circuit such as a current amplifier. Here, the current separation diodes R _1-0 to _{R 54-31} as crosstalk prevention means ensure signal separation between the amplifying MOS (or MIS) transistors connected to the individual data lines (especially when not selected). It is set up for the purpose of

Furthermore, if the environmental characteristics of the selectable amplifying element are the same or similar (mainly transistor threshold voltage, etc.), it is possible to compensate for the environmental characteristics of the amplifying element by selecting appropriate values of V _B1 and V _B2 . This is obvious, especially when the amplifying element, the photoconductive element, and the compensating element, which will be described later, are manufactured using the same technology.

A scanning circuit according to a second embodiment is shown in FIG. The first example shown in Figure 1 is sufficient when high accuracy in reading out the amount of incident light is not required, or when the transistors used for amplification are products of the same lot and the transfer characteristics, especially the distribution of the threshold voltage, are small. It is expected to be effective and the circuit is simple. However, especially when reading light amount information with high accuracy, the distribution of the transfer characteristics may become a problem. In the example shown in Figure 2, in order to solve the above problem, resistors F _1-0 to F _54-31 are inserted into the source circuits of the amplification transistors A _1-0 to _{A 54-31} , and the current feedback is This is an example of achieving uniformity of complex transfer characteristics. The explanation of the circuit operation will be clear from the explanation of the scanning circuit of the first embodiment shown in FIG. 1, if it is understood that negative feedback using current feedback is applied to the operation of the amplifying transistor.

An example of a scanning circuit according to the third embodiment of the present invention is shown in FIG. 3a, and a modification thereof is shown in FIG. 3b.
In these examples, transistors P _1-0 to _{P 54-31} (only a part of which are shown in the figure), which are nonlinear operating elements, are used instead of resistors as elements to realize the current feedback, and an amplification transistor A is used. _MOS ( _or
MIS) transistors T _1-0 to T _54-31 are used,
In particular, the amplification transistors A _1-0 to _{A 54-31} , the current feedback transistors P _1-0 to _{P 54-31} , and the signal separation transistors T _1-0 to _{T 54-31} are manufactured using the same technology. By configuring this, a great effect is produced that it can be easily integrated.

Furthermore, in the case of Fig. 3a, the bias power supply to the common gate of the current feedback transistors P _1-0 to P _54-31 is applied.
It has the feature that the transfer characteristics can be programmed in combination by changing the power supply voltage from V _G. FIG. 4 shows the change in transfer characteristics for various common gate bias values.

The above-described scanning circuit always amplifies the output signal from the photoconductive element (in the above example, converts and amplifies it into a current) and sends the signal to the matrix wiring section. In general, the conductivity of photoconductive elements is quite low, and when applied to elongated image reading devices required for digital copying machines, facsimiles, etc., which are the main uses of the photoelectric conversion device of the present invention, , a wide matrix wiring is required, and weak electrical signals must be processed through long wiring.
In many cases, a good signal-to-noise ratio cannot be expected. One of the major features of the present invention is that, as shown in the above example, the selection element that selects the output signal of the photoconductive element has an amplifying effect, and the above matrix wiring can be driven with low impedance, reducing noise and other noise. This has greatly reduced the negative impact.

FIG. 5 shows a schematic explanatory diagram of the configuration of the photoelectric conversion device of the present invention. A group of photoconductive elements made in a row on a transparent substrate 50 such as glass (the element structure will be described later)
SB ₁ to _{SB 54} are scanning circuits integrated through electrode wiring formed using thin film technology on the same substrate.
Wires I ₁ to _{I 54} (only partially shown)
They are connected by bonding. The output lines from the scanning circuits _I1 to _I54 are also connected to electrodes formed on the substrate 50 by vapor deposition using wire bonding, guided to the matrix wiring section 51, and finally connected to the output electrodes. be done. drive line b ₁
External control lines such as ~ _b54 are also led to the scanning circuits _I1 to _I54 through the thin film electrode wiring on the substrate 50. The photoelectric conversion element having a hybrid structure shown in this example has the same structure as the photoconductive element having a monolithic structure shown in the following example, and will therefore be explained in detail at that time.

The embodiment shown in FIG. 6 is an example of a photoelectric conversion device of the present invention in which the scanning circuit shown in FIG. 1 is all deposited on one substrate using thin film technology. FIG. 6a is a plan view, and FIG. 6b is a sectional view taken along line X-X' in FIG. 6a. On the substrate 3100 are a photoelectric conversion section 3101, a compensation element section 3102, and a selectable amplification section 310.
3, a matrix wiring section, a signal input/output electrode, and a power supply electrode section, which are not shown but are located on the right side of the paper, are fabricated. A general schematic diagram of the matrix wiring section is shown in FIG.
Reference numerals 70 to 74 correspond to through-hole connection parts, and 75 corresponds to a photoelectric conversion part and a scanning circuit part.

The individual electrodes 3105 of the photoelectric conversion unit 3101 are formed of a transparent conductive material such as indium tin oxide (ITO) by vapor deposition thin film technology so that light passing through the transparent substrate 3100 can be incident. Around the pixel 3105, a light-shielding electrode 3107 made of chromium (Cr) or the like is formed independently for each pixel using vapor deposition technology and photo-etching technology in order to make the pixel shape uniform. Furthermore, on the individual electrode 3105
A glow discharge is generated in a mixed gas of SiH ₄ and H ₂ to form a photoconductive thin film of amorphous hydrogenated silicon (hereinafter abbreviated as "A-Si:H") that is deposited by decomposition of SiH _4. Then, this film is patterned pixel by pixel by photo-etching to fabricate an A-Si photoconductive element 3116. Subsequently, a common counter electrode 3108 is formed using a metal material such as Al by thin film technology via a vapor deposition etching process.

In addition, in the vapor deposition process using the glow discharge decomposition method described above, the doping amount can be varied over a wide range by mixing an appropriate concentration of PH ₃ gas or B ₂ H ₆ gas into the SiH ₄ /H ₄ gas. , thereby making it possible to produce an A-Si:H thin film with appropriate n-type conductivity or p-type conductivity, and
The A-Si layer can be successively deposited with layers of each conductivity type without being exposed to the outside air. For example, the above A-Si:H photoconductive film secures resistive contact with the electrode metal by forming its upper and lower surfaces with an n ⁺ layer of A-Si:H doped with a high concentration of P atoms. ing. Therefore,
In the following explanation, the method of forming the A-Si layer of each conductivity type will not be mentioned.

Each element 3117 of the compensation element section 3102 is manufactured at the same time as each element 3116 of the photoconductive element section 3101, but the compensation element 3117 is provided with a light shielding electrode 3107 instead of the light incident transparent electrode 3105 of the element 3116. The photoelectric conversion element 31
Different from 16. Therefore, as mentioned above, the bias voltage supply lines 3115 and 310 are connected from the V _B1 and V _B2 power supplies.
By supplying the voltage value applied to 4 so that it has the same absolute value with opposite polarity, it is possible to cancel the dark current that is common to both elements and is particularly sensitive to temperature, and to balance both elements appropriately. By doing so, it is also possible to compensate for the transfer characteristics of the MIS structure transistor 3112 for amplification.

In the selection drain electrode part 3111 of the transistor 3112 having a semiconductor part made of poly-Si, the n ⁺ layer is removed by taking advantage of the fact that the etching rate of the poly-Si thin film depends on the concentration of doped P atoms. As a drain electrode type material
By using metal such as Au, the drain electrode 3
111 and the semiconductor layer 3120 are shown in _FIG .
It forms a Schottky barrier diode designated R _54-31 which functions as an isolation diode. Further, an n ⁺ layer 3121 is left at the contact portion between the source side electrode 3113 and the n-type semiconductor layer 3120 to maintain ohmic contact. Insulating layer 3
119 is also made of an insulating material such as a sputtered film of Si ₃ N ₄ or SiO ₂ , and in particular, the selection electrode 3110 is formed for the purpose of reducing the electrostatic coupling with the light shielding electrode 3107 which is the output line from the photoelectric conversion section. ing.

The photoelectric conversion device shown in FIGS. 8a and 8b is an example in which current feedback resistors F _1-0 to F _54-31 shown in FIG. 2 are inserted,
FIG. 8a is a schematic plan view, and FIG. 8b is a cross-sectional view taken along line X-X' in FIG. 8a. The arrangement of each part is almost the same as in the case of Fig. 6, and the difference is that a resistor 3200 is provided, which is made of A-Si or poly-Si with an appropriate doping amount, or an appropriate metal oxide. , borides, nitrides, etc. The resistor section 3200 includes a resistive film 3204 having an appropriate resistance value on an insulating layer 3207, and electrodes 3205 and 32 provided on both sides of the resistive film 3204.
06 and an insulating film 3208 provided on the surface. The electrode 3205 is connected to the drain of the transistor of the amplification section 3203.

FIGS. 9a and 9b show an example in which an MIS transistor is used as the current feedback element and an MIS transistor is used as the separation element, and these are fabricated using poly-Si thin film technology. Figure 9a is a plan view, Figure 9b
is a cross-sectional view taken along line X-X' in FIG. 3a. The operation of the corresponding scanning circuit has already been described in FIG. 3a. The difference in the arrangement of components from the example shown in FIG.
305 is arranged in parallel with the light shielding electrode 3306, and the isolation transistor 3306 and the current feedback transistor 3307 are arranged independently. The difference between the MIS transistor 3300 for increasing the width and that shown in FIG. 6 is that the MIS transistor 330
The point is that the drain of 0 is designed to maintain ohmic contact with the electrode metal. Also, MIS for separation
It should be added as a supplementary explanation to the figure that the gate of the transistor 3306 is connected to the selection signal line, and the drain side is connected to the transistor power supply line _VDV .

As mentioned above, preferred embodiments of the present invention include A-
A photoconductive element whose semiconductor portion is made of a photoconductive thin layer made of Si:H or poly-Si, an integrated scanning circuit including an amplification means whose semiconductor portion is made of poly-Si, and a matrix wiring are mounted on a single substrate. An example of the hybrid method assembled above, and the photoconductive element,
Although an example in which the scanning circuit is formed in a monolithic manner has been described, the present invention is not limited to these embodiments.

〔effect〕

As shown in the embodiments above, in the present invention, in a conventional photoelectric conversion device that scans and outputs a large amount of optical information,
Created a photoelectric conversion device that can be made longer with high accuracy and greatly reduces the influence of noise, which can be a problem when photoconductive elements with high impedance are widely arranged, by configuring a scanning circuit with an amplification function. Make what you do possible. According to the present invention, low-noise signal output without interference can be achieved with high responsiveness under any environment.

[Brief explanation of drawings]

FIGS. 1 to 3 a and b are scanning circuit diagrams for explaining scanning circuits according to each embodiment of the present invention, and FIG. 4 is a diagram showing transfer characteristics for a common gate bias value in the present invention. Figures 5 and 6 a and b showing changes are explanatory diagrams for explaining other embodiments of the present invention, and Figure 6 b is the
-X' cross-sectional view, FIG. 7 is an explanatory diagram for explaining the matrix wiring part in the present invention, and FIGS. FIG. 8b is an explanatory diagram for explaining an example of the embodiment.
FIGS. 9a and 9b are cross-sectional views taken along line X-X' in FIG. 9a, respectively. 3100...Substrate, 3101...Photoelectric conversion unit,
3102... Compensation element section, 3103... Amplification section, 3105... Electrode, 3107... Light shielding electrode, 3108... Common counter electrode, 3115... Bias voltage supply line, 3120... Semiconductor layer, 32
00...Resistor part, 3203...Amplification part, 320
4...Resistive film.

Claims (1)

[Scope of Claims] 1 A plurality of photoelectric conversion elements: Each photoelectric conversion element is electrically connected and amplified according to the signal output from the photoelectric conversion element according to the amount of light incident on the photoelectric conversion element. A plurality of semiconductor elements each having a semiconductor layer made of polycrystalline silicon as a signal amplifying means for outputting a signal; a plurality of compensation means having: a plurality of crosstalk prevention means provided for each signal amplification means to prevent crosstalk between signals output from each signal amplification means; and a photoelectric conversion signal output comprising: A plurality of units, a unit drive wiring for transmitting a unit selection signal for exclusively selecting the plurality of signal amplification means for each unit, and a common unit for transmitting the output signal of the same level signal amplification means in each unit. A solid-state photoelectric conversion device characterized in that a signal output wiring and a signal output wiring are integrally provided on the same substrate. 2. The solid-state photoelectric conversion device according to claim 1, wherein the photoelectric conversion element includes a photoelectric conversion layer made of amorphous silicon.