JPH0337743B2 - - 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) having a photoelectric conversion function, and a circuit having a scanning function that sequentially outputs electrical signals outputted from the group of photoelectric conversion elements in a chronologically arranged form. Includes photodiodes and MOS/FETs (Field
effect transistor) as a component (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 MOS type or CTD type photoelectric conversion device, 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.

That is, if the resolution of the photoelectric conversion unit is, for example, 10 lines/mm,
Assuming that the length of the light receiving surface in the longitudinal direction is 3 cm, A4
When attempting to copy a size original, the optical image of the original formed on the light receiving surface is reduced to approximately 1/69,
The actual resolution of the photoelectric conversion unit for an A4 document ends up being reduced to about 1.5 lines/mm.

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 part is required in such a system, but it is difficult to use a manufacturing technology that increases the resolution of the photoelectric conversion section, but it is difficult to use a manufacturing technology that increases the resolution of the photoelectric conversion section. 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 original is 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 has a linear white spot or a portion corresponding to a linear white spot. are removed and combined into an incomplete one. 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 document 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]

An object of the present invention is to improve conventional photoelectric conversion devices.

Another object of the present invention is to provide a solid-state photoelectric conversion device that has an elongated light-receiving surface, has a photoelectric conversion section with high resolution and high sensitivity, and is extremely lightweight. It's about doing.

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.

Still another object of the present invention is to provide a solid-state photoelectric conversion device with low noise and no afterimage, which is suitable for increasing length and can compensate for variations in the 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: a signal storage system that is electrically connected to each photoelectric conversion element and accumulates signals output from the photoelectric conversion element according to the amount of light incident on the photoelectric conversion element. A plurality of means: electrically connected to each signal storage means, and a plurality of initialization means for returning the signal storage means from a signal storage state to an initial state; and: electrically connected to each signal storage means. a plurality of semiconductor elements made of polycrystalline silicon, and a semiconductor layer serving as a signal amplification means for outputting a signal amplified in accordance with the signal stored in the signal storage means; provided for each signal amplification means; A plurality of standardization means for standardizing the transmission characteristics of signals by the corresponding signal amplification means between each signal amplification means: A plurality of standardization means are provided for each signal amplification means, and the signals output from each signal amplification means are crossed. a plurality of photoelectric conversion signal output units comprising: a plurality of crosstalk prevention means for preventing talk; and a unit selection signal for exclusively selecting each of the plurality of signal amplification means for each unit; Unit drive wiring, common control wiring that transmits control signals for controlling each initialization means in each unit, and common control wiring that transmits output signals of the same level signal amplification means in each unit. This is achieved by a solid-state photoelectric conversion device characterized in that the signal output wiring and the signal 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]

FIG. 1 shows a scanning circuit that is the basis of the present invention. 1728 (=54 x 32) required to achieve image reading at a density of approximately 8 pixels/mm in the short direction of A4
The photoconductive elements S _1-0 , ~S _54-31 are external bias power supplies.
Powered by V _B. Therefore, capacitors C _1-0 to _{C 54-31} for charge storage as charge storage means
Charges are accumulated at a rate corresponding to the amount of light incident on each photoconductive element. As a result, the capacitor
The connection point potential to the gates of the MOS transistors _A1-0 to _A54-31 as selectable signal amplification means for _C1-0 to _C54-31 varies depending on _the amount of incident light for a fixed charge accumulation time. It will have a corresponding value. In the scanning circuit shown in FIG. 1, the charge storage capacitor is expected to function as a low frequency filter circuit together with the photoconductive element. If a voltage is exclusively supplied to the drain side wiring common to every 32 amplification MOS transistors, for example, block drive line _b1 , the amplification MOS (or MIS) transistor _{A1- 0} to _A1-31 are biased, and each amplifying MOS (or MIS) transistor has a channel resistance corresponding to the amount of light incident on the individually connected photoconductive element. Therefore, a signal current corresponding to the amount of light incident on the photoconductive elements S _1-0 to _{S 1-31} is automatically output onto the individual data lines D ₀ to _{D 31} . 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, current separation diodes R _1-0 to _{R 54-31} as crosstalk prevention means are connected to individual data lines D ₀
This is provided to ensure isolation between the amplifying MOS (or MIS) transistors A _1-0 to A _54-31 connected to D ₃₁ (especially when not selected). Next, when voltage is supplied exclusively to the drive line _b2 , the discharge MOS (or
MIS) Transistors Q _1-0 to _{Q 1-31} become conductive and the data is stored in the storage capacitors C _1-0 to C _1-31 belonging to the first photoconductive element group S _1-0 to S _1-31 . Charges will be discharged through the transistors Q _1-0 to Q _1-31 .

The common gate line of the discharge transistors Q _1-0 to Q _1-31 is connected to the drain side of the amplification transistors A _2-0 to _{A 2-31} belonging to the second photoconductive element group S _2-0 to _{S 2-31} . Driving by connecting to a common line has the advantage of reducing the number of control lines from external equipment to the photoelectric conversion device of the present invention, but due to problems such as differences in drive voltage and drive timing settings, when driving separately. can also be easily inferred.

Also, taking into account the transfer characteristics of the threshold voltages and other factors of the amplification transistors A _1-0 to _{A 54-31} , the common source line of the discharge transistors Q _1-0 to _{Q 54-31} is supplied with power from a separate bias power supply. If so, it is clear that this has the effect of expanding the scope of element design.

A scanning circuit according to a first embodiment of the present invention 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 configuration is simple. However, especially when reading light amount information with high accuracy, the distribution of the transfer characteristics may become a problem. The example shown in Figure 2 uses an amplifying transistor to solve the above problem.
This is an example in which a resistor is connected as a source normalization means for each of A _1-0 to _{A 54-31} , and the composite transfer characteristics are made uniform by current feedback. The explanation of the circuit operation will be clear from the explanation of the scanning circuit of the first example if it is understood that negative feedback using current feedback is applied to the operation of the amplifying transistors A _1-0 to A _54-31 .

A scanning circuit according to a second embodiment of the present invention is shown in FIG. 3a, and a modification thereof is shown in FIG. 3b. In these examples, a nonlinear operating element is used instead of a resistor as an element of the normalization means to realize the current feedback.
Using P _1-0 ~ _{P 54-31} (only a part is shown in the figure),
In addition, a MOS (or MIS) transistor is used as a means for separating the amplification transistor from the common line on the drain side, and in particular, the amplification transistor A _1-0 ~
A _54-31 (only a part is shown in the diagram), discharge transistor Q _1-0 ~ _{Q 54-31} (only a part is shown in the diagram), and isolation transistor T _1-0 ~ _{T 54-31} (Only a part is shown in the figure) By configuring them with elements manufactured using the same technology, a great effect is created that they can be easily integrated.

In particular, in the case of the example shown in Fig. 3a, the transfer characteristic can be programmed in combination by changing the voltage of the common gate bias V _G for feeding power to the current feedback transistors P _1-0 to P _54-31 . have FIG. 4 shows changes in transfer characteristics for various common gate bias V _G values.

In the scanning circuit described above, the output from the photoconductive element is always amplified (in the above example, it is converted and amplified into a current) and the signal is sent out from 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, facsimile machines, etc., which are the main uses of the photoelectric conversion device of the present invention, Since a wide matrix wiring is required, weak electrical signals must be processed through long wiring, and a good signal-to-noise ratio cannot often be expected. One of the major features of the present invention is that, as in the previous examples, the selection element connected to the output terminal of the photoconductive element has an amplifying effect, and the above matrix wiring section is regarded as low impedance. Since each element can be driven, the negative effects of noise and the like are greatly reduced.

FIG. 5 shows a schematic diagram for explaining the configuration of the photoelectric conversion device of the present invention. A group of photoconductive elements (the element structure will be described later) SB ₁ to _{SB 54} (only up to SB ₁₅ is shown in the figure) formed in a line on a transparent substrate 500 made of glass etc. are also formed on the same substrate 500.
Scanning circuits I ₁ to _{I 54} (up _to I 15 are shown in the figure) integrated through electrode wiring formed on the top using thin film technology and capacitor groups CB ₁ to _{CB 54} (only up to CB ₁₅ is shown in the figure) (only shown) by wire bonding. Furthermore, the output lines from the scanning circuits I ₁ to _{I 54} are also connected by wire bonding to electrodes provided on the substrate and by evaporation technology, led to the matrix wiring section 501, and finally led to the output electrodes. It will be destroyed. Drive line b ₁ ~
External control lines such as b ₅₄ are also led through electrode wiring on the substrate 500 to the substrate where the scanning circuit is provided. The photoelectric conversion element in the hybrid structure photoelectric conversion device shown in this embodiment example has the same structure as the photoelectric conversion element in the monolithic structure photoconversion device shown in the following embodiment example. Explained in detail.

The structure shown in FIG. 6 is an example of a photoelectric conversion device in which all of the scanning circuit shown in FIG. 1 is realized on one substrate by vacuum deposition thin film technology. Figure 6a is a plan view, Figure 6b is the X-
FIG. 3 is a cross-sectional view at a position indicated by X'. On the substrate are a photoelectric conversion section 601, a charge storage section 602, a selectable amplification section 603, a discharge section 604, and a matrix wiring section, signal input/output electrodes, and power supply electrodes located on the right side of the paper (not shown). It is provided. A general schematic diagram of the matrix wiring section is shown in FIG.
04 and the like correspond to through-hole connection portions, and 705 corresponds to a photoelectric conversion portion and a scanning circuit portion.

The individual electrodes 605 of the photoelectric conversion unit 601 are formed by a vapor deposition method using a transparent conductive material such as indium tin oxide (ITO) so that light passing through the transparent substrate 600 can enter, and the pixel shape is uniform. In order to improve the image quality, an electrode 607 formed by vapor deposition using a light-shielding electrode material such as chromium (Cr) is fabricated independently for each pixel by photo-etching. Furthermore, a glow discharge is generated on the individual electrode 605 in a mixed gas of SiH ₄ gas and H ₂ gas, for example, and SiH ₄
A photoconductive thin film of amorphous hydrogenated silicon (hereinafter abbreviated as "A-Si:H") is deposited by decomposition of the silicon, and an A-Si:H photoconductive film 606 for each pixel is produced by photoetching. do. Subsequently, a common counter electrode 608 is wired using a metal material such as Al (via a vapor deposition and etching process) using thin film technology.

In addition, in the deposited film formation process using the glow discharge decomposition method described above, an appropriate concentration of SiH ₄ /H ₂ gas is used.
By mixing PH ₃ gas or B ₂ H ₆ gas, n
A-Si with type conductivity or p-type conductivity:
H thin films can also be produced, and A-Si:H thin films of each conductivity type can be formed continuously without being exposed to the outside air. For example, the above A-Si:H photoconductive film secures ohmic contact with the electrode metal by forming its upper and lower surfaces with an n ⁺ layer doped with P atoms at a high concentration. Therefore, in the following explanation, the method of forming the A-Si:H film of each conductivity type will not be discussed one by one.

Now, the charge storage part 602 is a vapor deposited thin film 6 formed by pattern etching a film made of SiO ₂ or Si ₃ N ₄ formed by sputtering method or the like.
It is composed of a capacitor made by wiring a ground electrode 609 across the capacitor 18 using a thin film formation method.

The amplification thin film transistor 612 is an MIS (metal-
It has an insulator-semiconductor) structure. An electrode 607 made for light shielding supplies a potential generated by the charges accumulated in the charge storage section 602 to the gate of the MIS structure transistor.

A poly-Si semiconductor thin film is used as the semiconductor thin film constituting the semiconductor portions of the amplification thin film transistor 612 and the discharge transistor 615.

Selection drain electrode part 6 of transistor 612
11, the n ⁺ layer is removed by taking advantage of the fact that the etching rate of the Si thin film depends on the doped P atom concentration, and by using a metal such as Al as the material for the drain selection electrode 610, the structure shown in FIG. TeR _1-0
It forms a Schottky barrier diode with the function of an isolation diode, denoted ~R _54-31 . Also, the contact part of the source side electrode 613 is
The n ⁺ layer remains to maintain ohmic contact.
The insulating layer 619 is also composed of an insulating film such as a sputtered film of Si ₃ N ₄ , SiO ₂ or the like, and particularly reduces the electrostatic coupling between the drain selection electrode 610 and the light shielding electrode 607 which is the output line from the photoelectric conversion section. formed for a purpose.

The MIS structure transistor 615 constituting the discharge section 604 has a drain side electrode and a source side electrode (614, 616, respectively) to maintain ohmic contact with each other.
They are connected via an n ⁺ layer of a poly-Si semiconductor thin film based on Si. The n ⁺ layer of the Si film between the drain electrode 614 and the source electrode 616 is removed by photoetching.

The photoelectric conversion device shown in FIGS. 8a and 8b has current feedback resistors F _1-0 to F _54-31 as shown in the circuit diagram in FIG. 2.
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 800 is provided, and this
Alternatively, poly-Si may be used, or an appropriate metal oxide such as boride or nitride may be used.

An example using an MIS transistor as a current feedback element is shown in FIGS. 9a and 9b. The corresponding scanning circuit diagram is shown in FIG. 3a. This embodiment is also similar in many respects to the arrangement of each part shown in FIG.
The only difference is that a MIS transistor 901 is similarly formed as a separation element between a charge storage section 906 and an amplifying MIS transistor 904. Furthermore, the MIS transistor 6 for amplification shown in FIG.
12 and an amplifying MIS transistor 90 shown in FIG.
4 in that the drain of the MIS transistor 904 is designed to maintain ohmic contact with the electrode metal. Furthermore, the gate 907 of the MIS transistor for separation 901 is connected to the input line 9 of the selection signal line bi.
02, and furthermore, the drain side is connected to the transistor power supply line V _D 903 as a supplementary explanation to the figure.

As mentioned above, preferred embodiments of the present invention include A-
A photoconductive element whose semiconductor part is made of a photoconductive thin layer made of Si:H or poly-Si, an integrated scanning circuit including an amplification means whose semiconductor part is made of poly-Si, and a matrix wiring are mounted on a single substrate. Although the above-mentioned hybrid method and the example in which the photoconductive element and the scanning circuit are formed in a monolithic method have 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, it is possible to realize signal output with high responsiveness without variations among elements, interference, or afterimages.

[Brief explanation of drawings]

Figure 1 is a scanning circuit diagram, Figures 2 and 3 a, b
4 is a scanning circuit diagram for explaining a scanning circuit according to each embodiment of the present invention, FIG. 4 is a diagram showing changes in transfer characteristics with respect to a common gate bias value in the present invention, and FIGS. Figures 6a and 6b are schematic explanatory diagrams for explaining the basic configuration of the present invention.
Figure 6b is a sectional view taken along line X-X' in Figure 6a;
The figure is an explanatory diagram for explaining the matrix wiring part in the present invention, and FIGS. FIG. 8b is a cross-sectional view of FIG. 8a, and FIG. 9b is a cross-sectional view taken along line X-X' of FIG. 9a. 500... Substrate, 501... Matrix wiring section, 601... Photoelectric conversion section, 602... Charge storage section, 603... Amplification section, 604... Discharge section, 60
5...Individual electrode, 606...Photoconductive layer, 607...
... Electrode, 608 ... Common counter electrode, 609 ... Ground electrode, 612 ... Amplification transistor, 615
...Discharge transistor, 619...Insulating layer, 7
00-704... Through-hole section, 705... Photoelectric conversion section and scanning circuit section.

Claims (1)

[Claims] 1. A plurality of photoelectric conversion elements: Each photoelectric conversion element is electrically connected to each other, and for accumulating signals output from the photoelectric conversion element according to the amount of light incident on the photoelectric conversion element. A plurality of signal storage means are electrically connected to each signal storage means, and a plurality of initialization means are electrically connected to each signal storage means for returning the signal storage means from a signal storage state to an initial state. a plurality of semiconductor elements whose semiconductor layers are made of polycrystalline silicon as signal amplification means which are connected to each other and output a signal amplified in accordance with the signal stored in the signal storage means; A plurality of standardization means are provided for each signal amplification means and standardize the signal transfer characteristics of the corresponding signal amplification means between each signal amplification means. a plurality of crosstalk prevention means for preventing signal crosstalk; a plurality of photoelectric conversion signal output units comprising: a unit selection signal for exclusively selecting the plurality of signal amplification means for each unit; unit drive wiring that transmits the signal, a common control wiring that transmits the control signal for controlling each initialization means in each unit, and a common control wiring that transmits the output signal of the signal amplification means of the same level in each unit. 1. A solid-state photoelectric conversion device characterized in that a common signal output wiring is 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.