JPH07107931B2 - Photoelectric conversion device manufacturing method - Google Patents

Description

The present invention relates to a photoelectric conversion device, and more particularly to a photoelectric conversion device used for reading a facsimile, an image reader, a digital copying machine, an electronic blackboard and the like.

[Prior Art] In recent years, in order to reduce the size and increase the performance of fax machines, image readers, and the like, a long line sensor having an equal magnification optical system has been developed as a photoelectric conversion device. Conventionally, a line sensor of this type is configured by connecting signal processing ICs (integrated circuits) each configured by a switch element or the like to each photoelectric conversion element arranged in a row in an array.
However, the number of photoelectric conversion elements is
According to G3 standard, 1728 A4 size is required, and a large number of signal processing ICs are required. For this reason, the number of mounting steps increases, and a satisfactory manufacturing cost and reliability are not obtained. On the other hand, as a configuration for reducing the number of signal processing ICs and reducing the mounting man-hour, a configuration using matrix wiring has been conventionally adopted.

FIG. 5 shows a block diagram of a photoelectric conversion device having matrix wiring. In FIG. 5, 1 is a photoelectric conversion element part, and 2 is
Is a scanning unit, 3 is a signal processing unit, and 4 is a matrix wiring unit. Further, FIG. 6 is a plan view of a conventional matrix wiring part, and FIGS. 7 (a) and 7 (b) are AA 'and B of FIG.
-B 'sectional drawing is each shown typically.

In FIG. 7, 601 is a substrate, 602 to 605 are individual electrodes, 606 is an insulating layer, 607 to 609 are common lines, and 610 is a through hole for making ohmic contact between the individual electrodes and the common line.

In the photoelectric conversion device that is matrix-wired in this way,
Since the number of signal processing circuits of the signal processing unit 3 is only the number of output lines of the matrix, there is an advantage that the signal processing unit can be downsized and the cost of the photoelectric conversion device can be reduced.

On the other hand, in a photoelectric conversion device using a thin film semiconductor, a thin film transistor (hereinafter referred to as TFT) that constitutes a photoelectric conversion element section and a transfer circuit is formed on the same substrate in the same process, thereby reducing the size and cost of the image reading device. It has also been proposed to measure (Figs. 8 and 9).

Further, for downsizing and cost reduction, there is also proposed a photoelectric conversion device in which a photoelectric conversion element directly detects reflected light from an original through a transparent spacer such as glass without using an equal-magnification fiber lens array. There is.

[Problems to be Solved by the Invention] However, in such conventional examples and prior examples,
There are the following problems.

That is, the first problem is that the weak output of the photoelectric conversion element is read out through the matrix wiring, so that the stray capacitance formed at the insulating intersection between the output individual electrode of the photoelectric conversion element and the common line of the matrix is reduced. Unless sufficiently small, crosstalk occurs between the output signals. This poses a severe constraint on the choice of interlayer dielectric material and matrix dimensioning.

Further, since the matrix common line is wired in the lengthwise direction, for example, a line sensor having an A4 size width has a length of 210 mm. Therefore, unless the line-to-line capacitance between the common lines is made sufficiently small, crosstalk occurs between the output signals. This leads to an increase in the size of the matrix part.

Further, the pitch of the output individual electrodes of the photoelectric conversion element is as narrow as 125 μm in a photoelectric conversion device having a resolution of 8 lines / mm. For this reason, unless the line capacitance between the individual electrodes is made sufficiently small, crosstalk occurs between output signals.

As a second problem, FIGS. 8 and 9 show an example of a conventional photoelectric conversion device in which photoelectric conversion elements, capacitors, wiring matrices, TFTs, etc. are formed on the same substrate. In the figure, 810 is a capacitor part, 811 is a thin film transistor part, and 812 is a matrix part. In FIG. 9, 901 is a glass substrate, 902 is a first conductor layer, 903 is an a-Si: N layer, and 904 is a-. A Si: H layer, 905 is an n ⁺ a-Si: H doping layer, 906 is a second conductor layer, and 907 is a channel. Further, in FIG. 8, 819 is a photoelectric conversion element, 816 is an entrance window, 811 is a thin film transistor, 810 is a capacitor, and 815 is a matrix.

As shown in FIGS. 8 and 9, scattered light L ′ from the original enters the thin film transistor arranged in the vicinity of the photoelectric conversion element, and a leak current is generated even during the OFF operation, which is a noise component. This is the cause of the decrease in S / N ratio. In addition, in the conventional single gate configuration, the TFT
There is a problem that the semiconductor layer is mainly used only in the vicinity of the interface between the first gate insulating film and the semiconductor layer, and the effect of using the semiconductor layer is small. Further, there is a problem that the interface of the semiconductor layer of the insulating layer on the side opposite to the gate is not electrically controlled at all, is electrically unstable, and leak current is likely to occur.

[Means for Solving the Problems] The present invention is directed to a plurality of one-dimensionally arranged photoelectric conversion elements having an amorphous silicon light-receiving layer and a plurality of thin film transistors connected to the plurality of photoelectric conversion elements. And a wiring portion for reading a signal from the plurality of photoelectric conversion elements via the plurality of thin film transistors on the surface of the same substrate, wherein the thin film transistor includes a source / drain electrode and an amorphous silicon layer. A channel portion and first and second gate electrodes provided above and below the channel portion, and the wiring portion is held at a predetermined potential with the first conductive layer. Of the first conductive layer and the third conductive layer such that the second conductive layer intervenes at the intersection of the first conductive layer and the third conductive layer. The amorphous silicon layer is interposed between the second conductive layer and the second conductive layer. A method of manufacturing a photoelectric conversion device, wherein a conductive layer and a third conductive layer are laminated on each other with an insulating layer interposed therebetween, wherein the first gate electrode and the first conductive layer are formed simultaneously. A first step of patterning and forming with a conductor; a second step of simultaneously forming the light receiving layer, the thin film transistor, and amorphous silicon of the wiring portion; the saw / drain electrode and the second A third step of forming a conductive layer with a conductor on which film formation and patterning are performed at the same time, and a conductor on which the second gate electrode and the third conductive layer are formed and patterned at the same time Formed in 4th
The gist exists in the manufacturing method of the photoelectric conversion device characterized by including the step of.

[Operation] According to the above configuration, a conductor layer capable of keeping a constant electric potential is provided at the intersection of the output individual electrode of the photoelectric conversion element and the common line, thereby forming the insulation intersection of the individual electrode and the common line. It is possible to eliminate the stray capacitance that is generated and to prevent the generation of capacitance between the electrodes and between the lines by providing wiring that can keep the potential constant between the individual electrodes and the common line. By forming the second gate electrode of the TFT using the same material as the electrode metal of the first gate and the same process, it is possible to prevent reflected light from the document surface and scattered light from entering the channel section of the TFT. Since it is formed by using the same process and the same material as the above matrix, it is not necessary to specially provide a light shielding means for TFT, and the process is simplified and the manufacturing cost can be reduced. Further, by providing the upper and lower two gate electrodes, the depletion layer in the semiconductor thin film spreads from the upper and lower sides when the TFT is turned off, and the carrier flow is blocked. Therefore, carriers are ejected from the vicinity of the interface with the insulating film having a large leakage current, and a large OFF resistance is obtained. Further, at the time of ON operation, the semiconductor layer / insulating layer interface on the first gate side and the second gate side is used, and the ON current also increases. As a result, a large improvement in S / N ratio can be obtained. Also the first
In the illustrated embodiment, the first gate and the second gate are connected through the contact hole 116 and are at the same potential, but the first gate and the second gate are separate wirings,
Different voltages may be applied to electrically control the interfaces between the upper and lower semiconductor layers and the insulating layer.

[Examples] Hereinafter, the present invention will be described in detail with reference to examples.
FIG. 1 is a plan view of an embodiment according to the present invention, and FIGS. 2 (A) and 2 (B) are A-A 'and B- in FIG. 1, respectively.
It is sectional drawing in B '. FIG. 3 is an equivalent circuit of the embodiment shown in FIGS. 1 and 2. FIG. 4 is a schematic view showing the manufacturing process of the present invention.

In addition, in the above-mentioned FIG. 1, FIG. 2, FIG. 3, and FIG.
115 is a TFT driving gate matrix, 117 is a contact hole, 109 is a photoelectric conversion element section, 116 is a light incident window, 111 is a TFT section, and 112 is a signal line matrix section.
Further, G _i is a gate line of the i block, V _S is a bias line of the photoelectric conversion element, V _SG is a lower electrode of the photoelectric conversion element section, V _R is a lower electrode of the capacitor, G _n is a ground line between common lines,
S _i is a common signal line. Further, 201 is a glass substrate, and the first conductor layer 202, a-Si: N is formed on the glass substrate 201.
The layer 203, the a-Si: H layer 204, the n ⁺ a-Si: H doping layer 205, the second conductor layer 206, the second insulator layer 207, and the third conductor layer 208 are sequentially stacked.

The photoelectric conversion device of the present invention has the above configuration, and the method for manufacturing the photoelectric conversion device in this embodiment will be described below with reference to FIG.

(A) A conductive film of Al, Cr or the like is deposited on a cleaned transparent substrate 201 such as glass by a sputtering method or a vapor deposition method, and patterned into a desired shape to form a first conductor layer 202.

(B) Further, using a well-known technique such as plasma CVD, an a-Si: N film 203, an a-Si: H film 204, and an n ⁺ -type doped a-Si: H film 205 are formed as a first insulating film. The elements are separated 213 by successively forming films and patterning the three layers into a desired shape to form a first contact hole 214.

(C) A second conductive layer 206 is formed by forming a conductive film of Al, Cr or the like by a sputtering method or a vapor deposition method and applying a pattern in a desired shape.

(D) The unnecessary n ⁺ a-Si: H doping layer such as the gap part of the photoelectric conversion device and the channel part of the TFT is removed by etching.

(E) After forming an a-Si: N film, a polyimide film, or the like as the second insulating film 207 on the second conductor layer, necessary patterning is performed to form a second insulating film on the first contact hole. A contact hole 215 is provided.

(F) A conductive film of Al, Cr, or the like is formed on the second insulating film by a sputtering method, a vapor deposition method, or the like, and patterned into a desired shape to form the third conductor layer 208. At this time, the third
The conductive layer is formed as a necessary wiring pattern in the matrix part, and is left to cover the channel part in the upper part of the TFT.

[Effect of the Invention] As described above, according to the present invention, by providing a conductor layer capable of keeping a constant electric potential at the intersection of the output individual electrode of the photoelectric conversion element and the common line, The stray capacitance formed at the insulated intersection with the common line can be reduced, crosstalk between signals due to the capacitance component can be reduced, and weak signals can be handled, and the S / N ratio can be improved.

Similarly, by providing wiring that can maintain a constant potential between individual electrodes and common lines, the capacitance between each electrode and each line can be reduced, crosstalk between signals can be reduced, and weak signals can be reduced. The S / N ratio is improved. Also,
Of the above wiring metals, by using the uppermost metal as the second gate of the TFT, the characteristics of the TFT are improved, and it is not necessary to provide special light shielding means for the TFT. Since they are manufactured in the same process, a simple process can be realized and the cost at the time of manufacturing can be reduced.

[Brief description of drawings]

FIG. 1 is a plan view of an embodiment according to the present invention. FIG. 2 is a sectional view taken along line AA 'and BB' in FIG. FIG. 3 is an equivalent circuit of the photoelectric conversion device shown in FIG. FIG. 4 is a schematic diagram showing a manufacturing process of the photoelectric conversion device of the present invention. FIG. 5 shows a block diagram of a matrix-wiring photoelectric conversion device. FIG. 6 shows a plan view of a conventional matrix wiring part, and FIGS. 7 (a) and 7 (b) show A- in FIG.
A ', BB' sectional drawing is shown. FIG. 8 shows a photoelectric conversion element,
This is an example in which capacitors, wiring matrix TFTs, etc. are integrally formed on the same substrate, and FIG. 9 shows A- in FIG.
It is A ', BB' sectional drawing. 109 ... Photoelectric conversion element section, 116 ... Light incident window section, 111 ...
… TFT section, 112 …… Signal line matrix section, 115 …… TFT driving gate matrix section, 117 …… Contact hole, 201 glass substrate, 202 …… First conductor layer, 203 …… a
-Si: N film, 204 ... a-Si: H layer, 205 ... n ⁺ a-Si: H doping layer, 206 ... second conductor layer, 207 ... second insulating layer,
208-third conductor layer, 213-element isolation part, 214-first contact hole, 215-second contact hole, 3
01 …… TFT second gate, 601 …… Substrate, 602-605 …… Individual electrodes, 606 …… Insulation layer, 607-609 …… Common line, 610 ……
Contact hole, 901 ... Glass substrate, 902 ... First conductor layer, 903 ... a-Si: N film, 904 ... a-Si: H layer, 905
...... n ⁺ a-Si: H doping layer, 906 …… second conductor layer, 90
7 ...... Channel part, V _SG ...... Sensor lower electrode, V _R・ ・ ・ Capacitor lower electrode, G _i …… Ground line between common lines, S _i …
… Common signal line, V _S …… Photoelectric conversion element bias line, V _Gi …
... Gate line of i-th block.

Claims (2)

[Claims] 1. A plurality of photoelectric conversion elements arranged in a one-dimensional array having an amorphous silicon light-receiving layer, a plurality of thin film transistors connected to the plurality of photoelectric conversion elements, and a plurality of photoelectric conversion elements. A wiring part for reading out a signal through the plurality of thin film transistors is provided on the surface of the same substrate, and the thin film transistor includes a source / drain electrode, a channel part of an amorphous silicon layer, and a channel part of the channel part. A first conductive layer, a first conductive layer, a second conductive layer having a predetermined potential, and a third conductive layer. Between the first conductive layer and the second conductive layer so that the second conductive layer is interposed at the intersection of the first conductive layer and the third conductive layer. Between the second conductive layer and the third conductive layer via the amorphous silicon layer In the production method of the photoelectric conversion device are laminated with each other through an insulating layer, first to form the said first gate electrode and the first conductive layer, simultaneously with the deposition and patterning made conductive body 1
And a second step of simultaneously forming the light receiving layer, the thin film transistor, and amorphous silicon of the wiring portion, and simultaneously forming and patterning the source / drain electrodes and the second conductive layer. And a third step of forming the second gate electrode and the third conductive layer with a conductor that is simultaneously formed and patterned.
The method of manufacturing a photoelectric conversion device, comprising: 2. The method according to claim 1, further comprising the step of providing a light source for certifying a document on the front surface side of the substrate through the substrate on the back surface side of the substrate. Manufacturing method of photoelectric conversion device.