JPH06103743B2 - Image sensor - Google Patents

Description

The present invention relates to an image sensor typified by a contact type line sensor used in a facsimile, an image scanner, etc.
In particular, it relates to an image sensor having a reading unit having the same width as a document.

[Prior Art] Conventionally, this type of image sensor has been used on a long substrate such as glass using a photoconductive material such as hydrogenated amorphous silicon (hereinafter a-Si: H), CdS, or CdSe. It is formed and manufactured by a thin film deposition technique such as vapor deposition.

Furthermore, Japanese Patent Application No. 61-144 previously filed by the applicant.
No. 990 proposes a photoelectric conversion device in which a thin film transistor (hereinafter referred to as a TFT) made of a-Si: H or poly-Si, a TFT type sensor, a storage capacitor and the like are formed on the same substrate.

FIG. 5 shows an equivalent circuit of a matrix drive type image sensor.

S1 to S _{n ・ m} are TFT type sensors, C _{s1 to} C _{sn ・ m} are storage capacitors that store the photocurrent of the sensor, and U _{1 to} U _{n ・ m} are switches (TFT) for resetting the charge of the storage capacitors. ), T ₁ ~ I
_nm reads the charge of the storage capacitor C _{L1 to} C
_It is a switch (TFT) that transfers to _Ln . The reset TFT and the transfer TFT are divided into n × m blocks. 11
Is a shift register / driver that sequentially selects and drives the gate lines (1 to m + 1).

Reference numeral 12 is a switch array for reading the voltage of the signal lines (1 to n), converting it to serial and outputting it.

FIG. 6 shows a 1-bit wiring pattern diagram of the image sensor of the equivalent circuit of FIG. 13 is a signal line matrix section, 14 is a sensor, 15 is a contact hole, 16 is a storage capacitor, 17 is a transfer TFT, 18 is a reset TFT, 19 is a gate wiring section, and 20 is a window for illumination. In this example, the sensor 14 directly receives the reflected light of the document illuminated by the window 20 and has a lensless structure.

FIG. 7 shows a sectional view taken along the line XX 'in FIG. 6, and FIG. 8 shows a sectional view taken along the line YY' in FIG. 1 is a glass substrate, 21 is a lower electrode, 3 is an insulating layer, 4 is an a-Si: H layer, 5 is an n ⁺ doped layer, and 22 and 23 are upper electrode layers.

Since the TFT type sensor is used in the above conventional example, the photosensitivity is 10 to 100 times higher than that of the photodiode type. Also,
The lensless configuration has advantages such as high light transmission rate and high sensor surface illuminance.

[Problems to be Solved by the Invention] However, since the sensor photocurrent is large, the storage capacity is required in proportion to the photocurrent. Large storage capacity is S / N ratio,
It is very advantageous in terms of characteristics such as dynamic range, but not necessarily advantageous in terms of manufacturing cost. That is, as the storage capacity increases, the substrate size of the sensor increases, and the number of sensors taken per manufacturing batch decreases.

[Means for Solving the Problems] The present invention provides an image sensor in which a photoelectric conversion part, a charge storage part, a switch part, and a wiring part for matrix connection are provided on the same substrate. The image sensor is characterized in that is formed on the substrate by being laminated with the wiring pattern of the wiring portion.

Further, the present invention provides a photoelectric conversion unit, a charge storage unit that stores a signal from the photoelectric conversion unit, a switch unit for transferring the signal stored in the charge storage unit, and a gate wiring group for driving the switch. And a signal wiring group for transmitting the signal transferred by the switch, the photoelectric conversion unit, the switch unit, the gate wiring group and the signal wiring group are arranged side by side on the same substrate, Part of the charge storage unit is stacked on the wiring pattern of the gate wiring group, and another part of the charge storage unit is stacked on the wiring pattern of the signal line group and formed on the substrate. There is a gist in the image sensor.

[Operation] With the above configuration, the present invention can reduce the width of the sensor substrate because the storage capacitor and the wiring portion can be formed at the same portion on the substrate by providing the insulating layer and increasing the number of wiring layers.

[Embodiment] FIG. 1 shows an example of a pattern configuration diagram of an image sensor of the present invention. In the figure, the broken line is the wiring pattern of the first layer, the solid line is the wiring pattern of the second layer, and the shaded area is the wiring pattern of the third layer. 13 is a signal line matrix section, 14
Is a sensor, 16 is a signal line matrix section 13 and a gate wiring section
It is formed at 19. It is the storage capacity. Reference numeral 17 is a transfer TFT, 18 is a reset TFT, and 20 is a window for lighting.

FIG. 2 is a sectional view taken along the line AA ′ in FIG. 1, FIG. 3 is a sectional view taken along the line BB ′ in FIG. 1, and FIG. 4 is a sectional view taken along the line CC ′ in FIG. 1 is a glass substrate, 3 is an insulating layer, 4 is a-
Si: H layer, 5 is an n ⁺ a-Si: H doping layer, 6 is a first layer electrode forming a gate electrode, a sensor gate electrode, an electrode of a storage capacitor, and the like. Reference numeral 7 is a second layer electrode that forms the source electrode / drain electrode of the TFT and the counter electrode of the capacitor. 8 is an insulating layer,
Reference numeral 9 is a third layer electrode for routing the wiring in the longitudinal direction of the substrate.
10 is a transparent protective layer.

When the number of signal lines and gate lines is, for example, an A4 read width and a pixel density of 8 pels / mm, if the total number of pixels of 1728 pels is connected in a matrix of 32 × 54, 32 signal lines and 54 gate lines are formed. If the line width is 20 μm and the space between lines is 20 μm as the process rule, the wiring width of the signal line is (20 μm + 20 μm) × 32 = 1280 μm, and the wiring width of the gate line is (20 μm + 20 μm) × 54 = 2160 μm, and the wiring pattern required for matrix connection is The area occupied on the substrate is about 3.4 mm in the lengthwise direction of the substrate.

On the other hand, as the storage capacity, sensor photocurrent 40nA, storage time 5m
s, the storage capacitor C _s to the accumulation saturation voltage 5V is required is _{C s = 40nA × 5ms / 5V} = 40pF. As shown in FIG. 4, when the storage capacitor is formed by the MIS structure in which the gate insulating layer and the a-Si: H layer are stacked, the area required to form 40 pF is about 3 × 10 ^-3 cm ² Becomes This is 100 μm × 3 mm when a pattern is designed corresponding to a pixel pitch of 125 μm, which is a dimension that allows a sufficient wiring pattern portion to be formed. First
By adopting the configuration shown in the figure, the pattern area of the storage capacitor becomes unnecessary, and the board width can be designed to be about 3 mm thinner. In particular, when the photoconductive sensor shown in this example is used in the matrix driving method, the pattern area of the matrix wiring portion and the storage capacitor portion occupies more than half of the sensor substrate, and the reduction of the substrate width due to the configuration of the present invention is due to the manufacturing batch. The yield per hit is remarkably improved, and the cost can be reduced.

Further, in the configuration of FIG. 1, since the intermediate layer between the hot side of the storage capacitor and the wiring pattern is set to the ground potential, the influence of signal crosstalk from the wiring portion is also eliminated.

[Advantages of the Invention] As described above, by stacking and forming the storage capacitor at the same place as the wiring pattern, (1) the sensor substrate width can be reduced and downsized, and (2) the number of production batches per manufacturing batch. Increase, yield is improved, (3) Cost can be reduced, and (4) S / N ratio can be increased because a sufficiently large storage capacity can be formed.
The dynamic characteristics are improved, and (5) the width of the sensor substrate is reduced, the number of redundant wirings is reduced, and it is also resistant to external noise.

[Brief description of drawings]

FIG. 1 is a pattern configuration diagram of the present invention. FIG. 2 shows A of FIG.
-A 'cross-sectional configuration diagram, FIG. 3 is a BB' cross-sectional configuration diagram of FIG. 1, FIG. 4 is a C-C 'cross-sectional configuration diagram of FIG. 1, and FIG. 5 is an equivalent of a matrix type photoelectric conversion device. Circuit, FIG. 6 is a pattern configuration diagram of a conventional example, FIG. 7 is a XX 'sectional configuration diagram of FIG. 6, and FIG. 8 is a YY' sectional configuration diagram of FIG. 1 ... Glass substrate, 3 ... Gate insulating layer, 4 ... a-S
i: H layer, 5 ... n ⁺ a-Si: H doping layer, 6 ... first electrode layer, 7 ... second electrode layer, 8 ... insulating layer, 9 ... third electrode layer, 10 ... … Protective layer, 11 …… Gate drive shift register, 12 …… Switch array, 13 …… Signal line matrix section, 14 …… Sensor, 15 …… Contact hole, 16 …… Storage capacity, 17 …… Transfer TFT, 18 ...... Reset TFT, 19 …… Gate wiring part, 20 …… Lighting window, 21 …… Gate electrode, 2
2,23 …… Source and drain electrodes.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsuhiko Yamada 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) Reference JP-A-56-138968 (JP, A)

Claims (3)

[Claims] 1. An image sensor in which a photoelectric conversion part, a charge storage part, a switch part, and a wiring part for matrix connection are provided on the same substrate, wherein the charge storage part is laminated with a wiring pattern of the wiring part. And an image sensor formed on the substrate. 2. The charge storage unit stores the signal from the photoelectric conversion unit, and the switch unit transfers the signal stored in the charge storage unit. The image sensor according to the item. 3. A photoelectric conversion section, a charge storage section for storing a signal from the photoelectric conversion section, a switch section for transferring the signal stored in the charge storage section, and a gate wiring group for driving the switch. And a signal wiring group for transmitting the signal transferred by the switch, the photoelectric conversion unit, the switch unit, the gate wiring group and the signal wiring group are arranged side by side on the same substrate, Part of the charge storage unit is stacked on the wiring pattern of the gate wiring group, and another part of the charge storage unit is stacked on the wiring pattern of the signal wiring group and formed on the substrate. Image sensor.