JPH02229470A - Photoelectric converting device - Google Patents

Abstract

PURPOSE:To provide a defect-free and long size photoelectric converting apparatus by constructing semiconductor sections of a photoelectric converting element and signal transferring means of a semiconductor thin film while providing an insulating layer in a signal processing circuit section, the insulating layer being possessed commonly by a signal storing means and the signal transferring means. CONSTITUTION:On a long board 504, there are juxtaposed transversely a photoelectric converting element 501, a storing capacitor 502, a thin-film transistor 503 including a cross-talk preventing diode, an interconnecting section 505 on the side of the photoelectric converting element and an interconnecting section 506 on the side of the transistor. A photoelectric converting section including a photoelectric converting element 602 and a signal processing circuit section consisting of a storing capacitor 603 for storing signals converted photoelectrically by the element 602 and of a thin-film transistor 604 as means for transferring the signals stored in the capacitor 603 are provided on the same board 601. The semiconductor sections of the element 602 and transferring means 604 are constituted of a semiconductor thin film and the signal processing circuit section includes an insulating layer 607 which is possessed commonly by the capacitor 603 and the means 604.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is applicable to photoelectric conversion devices, particularly optical information input units of 7-axis, digital cobia, laser recording devices, barcode reading devices, and other text and image reading devices. The present invention relates to a solid-state photoelectric conversion device.

Recently, due to the trend toward smaller overall devices, photoelectric conversion devices have been used as optical information input units of facsimile machines, digital copiers, laser recording devices, and other devices that read characters and images written on manuscripts. A photoelectric conversion device that has a light-receiving surface that is equal to or close to the size of the original image, has excellent resolution, can faithfully read the original image, and is compact and has a so-called elongated light-receiving surface. There has been significant progress in the development of equipment.

However, the photoelectric conversion device having the elongated light-receiving surface as described above has a major problem in the signal processing circuit section attached to the photoelectric conversion section.

That is, the signal processing circuit section occupies a much larger space than the photoelectric conversion section, and by making the photoelectric conversion section longer, the optical path length can be made very short, which is an advantage of miniaturization. The point is that it cannot be fully utilized.

Normally, one way to solve this problem is to divide the pixels (photoelectric conversion elements) of the photoelectric conversion unit into multiple blocks, wire each block in a matrix, and operate this signal processing circuit for each block. is taken.

The problem with this matrix wiring is that a bonding process is required to connect the photoelectric conversion element and the signal processing section and take out the signal to the outside, but the photoelectric conversion element and the signal processing section must be integrated. , the number of bonding steps becomes extremely large.

Normally, in order to solve this problem, a signal processing section is provided on a crystalline Si substrate, and a photoelectric conversion section is fabricated and integrated thereon.

However, in order to have an elongated light-receiving surface, it is necessary to provide a signal processing section adjacent to the elongated photoelectric conversion section, and using a crystal substrate does not fully meet this requirement.

The present invention has been made in view of the above points, and aims to improve conventional photoelectric conversion devices, and also to provide a defect-free and elongated photoelectric conversion device.

The photoelectric conversion device of the present invention includes a photoelectric conversion section in which N photoelectric conversion elements each having a light-receiving surface are arranged in a row, and a photoelectric conversion unit connected to the photoelectric conversion element to store signals output from the photoelectric conversion element. The present invention is characterized in that it includes a signal processing circuit section constituted by a crosstalk prevention diode and a transistor on the same substrate, and the photoelectric conversion element, the diode, and the transistor are constituted by a semiconductor thin film.

The present invention will be explained below with reference to the drawings.

FIG. 1 shows an equivalent circuit of the photoelectric conversion device of the present invention. This photoelectric conversion device has N photoelectric conversion elements PEI, P
E2, ..., PEN, capacitors CEI and CE as storage means for storing output signals of each photoelectric conversion element PE
2,..., CEN, crosstalk prevention diode D
I, D2... DN and transfer transistors SWI,..., SWN for sequentially transferring the charges stored in the storage capacitor to the output terminal OUT.

One electrode of the N photoelectric conversion elements is connected to a storage capacitor and an anode electrode of a crosstalk prevention diode, respectively. The counter electrodes of the storage capacitors are all grounded, and the cathode electrodes of the crosstalk prevention diodes are respectively grounded to the drain electrodes of the transfer transistors.

The other electrode of the photoelectric conversion element is connected every M pieces,
The signals are combined into M signal lines. This signal line is called a block selection line.

All source electrodes of the transfer transistors SW are connected to the output terminal OUT. The gate electrodes of the transfer transistors SW are grouped into L signal lines that are commonly connected to M gate electrodes. This signal line is called a gate selection line.

The optical information incident on the photoelectric conversion unit is outputted from the photoelectric conversion element driven by the block selection line to the output terminal OUT through the transfer transistor SW selected by the gate selection line.

FIG. 2 shows a timing chart for driving the photoelectric conversion device of the present invention shown in FIG.

The driving frequency of the block selection signals DI, D2, . . . , DM is normally M times the driving frequency of the gate selection signals Gl, G2, .

The optical information incident on the photoelectric conversion section changes the resistance of the photoelectric conversion element, and the respective storage capacitors CE are charged by the clock of the block selection signal D. The charges stored in the storage capacitor CE are sequentially outputted by the transfer transistor turned on by the gate selection signal G in accordance with the selection signal clock.

In this photoelectric conversion device, the photoelectric conversion element, the transfer transistor, and the crosstalk prevention diode are all formed of a semiconductor thin film on the same substrate.

The photoreceptor layer constituting the photoelectric conversion element PE is made of, for example, amorphous hydrogenated silicon (hereinafter abbreviated as a-Si:H), PbO, CdSe, SbzSs. Se. Se-
Te, Se-Te-As, Se-Bi, ZnCdTe,
It is composed of highly sensitive photoconductive materials such as CdS, Cu, S amorphous germanium hydride, and amorphous hydrogenated GexSi (1-x).

The semiconductor thin film that constitutes the thin film transistors SW and S is
For example, CdSe, a-Si:H (amorphous hydrogenated silicon). a-Ge:H (amorphous germanium hydride), amorphous hydrogenated GexS i (1-
It is made of polycrystalline or crystalline silicon.

In the present invention, N , P * A S * S
An element of Group V A of the periodic table such as b, B i, or B,
Photoreceptor layers and thin film transistors can be made into a- Preferably, it is formed of Si:H.

In the present invention, the layer thickness of the photoreceptor layer is determined by the degree of diffusion of photocarriers caused by the incidence of optical information, but is usually 4,000 to 2 μm, preferably 6,000 to 2 μm.
It is desirable that the thickness be 1.5 μm. The thickness of the semiconductor layer of a thin film transistor is preferably thinner than the thickness of the depletion layer region generated by the voltage applied to the gate electrode provided through the insulating layer, and is usually 1000 to 1 μm.
is preferred.

The substrate on which the photoelectric conversion element and thin film transistor are formed is made of a translucent material, for example, when optical information is incident on the light receiving surface of the photoelectric conversion element from the substrate side. If optical information is incident on the light-receiving surface from the photoelectric conversion element side formed on the opposite surface, such restrictions can be removed.

Suitable materials to be used as the substrate in the present invention include those that are commercially available or can be obtained as long as they have excellent flatness, planar smoothness, heat resistance, and resistance to various chemicals during manufacturing. Many things can be mentioned. Specific examples of such a substrate forming material include glass, 7059
glass (manufactured by Dow Corning), translucent materials such as magnesia, beryllia, subinel, yttrium oxide, aluminum molybdenum, special stainless steel (JIS standard S
Examples include non-transparent metal materials such as uS) and tantalum.

FIG. 3 shows a schematic perspective view illustrating the structure of the photoelectric conversion element. In this embodiment, glass is used as the substrate material, and the light receiving surface is on the opposite side of the substrate to the side on which the photoelectric conversion element is formed. For this reason, the substrate-side light-receiving surface electrode 302 is commonly connected to the N photoreceptor layers and is made of a light-transmitting material. For example, a light-transmitting conductive film such as SnO, ITO (indium tin oxide), In20s, etc. is used.

The photoreceptor layer 303 is non-dope, n-type or i
It is formed of a-Si:H type a-Si:H, and is doped into an n+ type at the junction surface 304 of the light-receiving surface side electrode 302 and the upper pixel electrode 305. This n+ layer 304 is provided to establish an ohmic connection between the light receiving surface, the upper pixel electrode, and the photoreceptor layer.

The upper pixel electrode is made of a material such as Af, and is connected to the storage capacitor E and the transfer transistor SW.

The storage capacitor CE is the opposite electrode 3 of the insulating layer 306.
07,308. As the material of the insulating layer 306, for example, S 1 s Na made by glow discharge method is used.
+ S iO 2 by sputtering method, Sins by CVD method, etc. In the present invention, a-
Since Si:H can be produced by a glow discharge method, SisN4 produced by a glow discharge method is preferred.

FIG. 4 shows a schematic perspective view for explaining the structure of a thin film transistor.

A gate electrode 403 is formed across an insulating layer 402 on a semiconductor thin film layer 404 made of non-doped n-type or i-type a-Si:H, and an n+ type layer 405 is formed on top of the semiconductor thin film layer 404. Source electrodes 406 are formed between them. A bonding layer 408 between the drain electrode 407 and the semiconductor layer 404 is made of a material that forms a Schottky junction between the semiconductor layer 404 and the bonding surface thereof to form a diode for preventing crosstalk. When the semiconductor layer is a-Si:H, materials for forming a Schottky junction include Au, I
r, Pt, Rh, Pb, etc., and in the present invention, pt
is preferred. Drain electrode 407 is preferably made of Af.

As shown in FIG. 5, the photoelectric conversion device of the present invention includes N photoelectric conversion elements 501, N storage capacitors 502, and N crosstalk elements arranged horizontally on a long substrate 504. It is composed of a thin film transistor 503 having a structure including a prevention diode, a photoelectric conversion element side wiring section 505, and a transistor side wiring section 506.

FIG. 6 shows a schematic perspective view for explaining the structure of the device of the present invention. A storage capacitor 603 and a storage transistor 60 are connected to the upper electrode of the photoelectric conversion element 602.
It is connected to the drain electrode of No. 4. A Schottky diode for crosstalk prevention is formed at the drain electrode of this thin film transistor 604. A gate electrode 605 and a source electrode 606 of the thin film transistor 604 are wired in a matrix in a two-layer structure with an insulating layer 607 interposed therebetween.

The light-receiving surface side electrode 608 of the photoelectric conversion element is formed of ITO, and is arranged on the substrate on the opposite side of the photoelectric conversion element 602 from the thin film transistor 604 .

Glass is used for the substrate 601, and optical information is incident on the back surface of the substrate.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an equivalent circuit of the photoelectric conversion device of the present invention, FIG. 2 is a timing chart of the operation of the photoelectric conversion device of the present invention, and FIG. 3 is a schematic diagram showing the structure of the photoelectric conversion element in the present invention. FIG. 4 is a schematic perspective view showing the structure of a thin film transistor according to the present invention, FIG. 5 is a schematic diagram showing the configuration of a device according to the present invention, and FIG. 6 is an example of a wiring pattern according to the present invention. FIG.

Claims (1)

[Claims] a photoelectric conversion section in which N photoelectric conversion elements each having a light-receiving surface are arranged in a row; connected to the photoelectric conversion element;
A storage means for accumulating the signal output from the photoelectric conversion element and a signal processing circuit section composed of a diode and a transistor for preventing crosstalk are provided on the same substrate, and the photoelectric conversion element, the diode, and the transistor are formed using a semiconductor thin film. A photoelectric conversion device characterized by comprising: