JPH06120474A - Bidimensional closed contact type image sensor - Google Patents

Abstract

PURPOSE:To provide a two-dimensional closed contact type image sensor which can easily correct a defective portion in a pixel, prevent line defect point defect and improve the yield of a product. CONSTITUTION:In the two-dimensional closed contact type image sensor of the present invention, a plurality of photodetectors 2a, 2b and switching elements 3a, 3b are arranged two-dimensionally and a plurality of pairs of the photodetector and switching elements are formed in only one pixel and aperture regions 8, 9 for correction are provided in the connecting area, etc., of the photodetector and switching element in each pixel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-dimensional contact type image sensor in which a plurality of light receiving elements are arranged two-dimensionally and read in close contact with an original, and in particular, the manufacturing yield can be improved. A three-dimensional contact type image sensor.

[0002]

2. Description of the Related Art Conventionally, in order to read an image, a reduction type image sensor for reducing and forming a document image on a one-dimensional IC sensor such as a CCD (charge coupled device) sensor or a MOS type sensor, or a document width. By using a long one-dimensional image sensor having the same length, a unity-magnification sensor or the like has been used in which an equal-size erect image is formed on the sensor and read.

The former reduction type image sensor requires a long optical path length in order to form an image by reducing the document width to the IC chip length, and at the same time, in order to solve the problems such as aberrations in the lens peripheral portion, It was an obstacle to the reduction in size and weight.

The latter unity-size sensor has a shorter optical path length than the reduction sensor, but the optical fiber lens array provided for forming an erect image of unity size is expensive, and white light is used. There was a problem such as chromatic aberration in which light of a particular color was emphasized when passing through the lens.

Therefore, in recent years, a perfect contact type one-dimensional image sensor has been proposed as a solution to the above problems. In this one-dimensional perfect contact type image sensor, for example, as shown in the cross-sectional explanatory view of FIG. 5, a photoelectric conversion section 43 having a window section 42 for transmitting irradiation light from the back surface is formed on a transparent substrate 41. The transparent protective layer 44 is provided so as to cover the translucent substrate 41, the window portion 42, and the photoelectric conversion portion 43. Then, the irradiation light incident through the window portion 42 is applied to the original 45 on the transparent protective layer 44,
The reflected light was converted into an electric signal by the photoelectric conversion section 43 (see Japanese Patent Laid-Open No. 58-38060).

The reading operation of the two-dimensional image, that is, the scanning by the conventional reduction type, coordinate type or contact type one-dimensional image sensor, that is, the scanning, is performed by the one-dimensional sensor and the original document 45 to be read.
And (2) are electrically scanned in the reading direction of the sensor, that is, the main scanning direction, and at the same time, they are relatively moved in the sub scanning direction orthogonal to the main scanning direction by mechanical means. There are mainly two types of mechanical scanning methods for the one-dimensional image sensor in the sub-scanning direction: a type that conveys the document 45 and a type that moves the sensor unit itself. The type that conveys the document 45 is used in a facsimile or the like, and the type that moves the sensor unit is used in a scanner or the like.

However, in the conventional one-dimensional image sensor having the mechanical scanning means, the former type of original document conveyance is limited to a sheet-like original type and the latter type sensor unit is moved. Then, since the size of the entire apparatus becomes large and the shape of the sensor section is limited, it has been difficult to apply the above-mentioned perfect contact type image sensor to this type.

Further, in the construction of the one-dimensional image sensor which requires these mechanical scanning means, the means for mechanically scanning (moving) must have high performance in scanning accuracy, and the optical information sensor Since an optical system for guiding on the surface is required, the cost is high.

Further, in the one-dimensional image sensor, since the same sensor is repeatedly scanned line by line to read the charge, there is an unread portion of the signal charge, and the resolution is deteriorated due to the optical response characteristics of the light receiving portion of the sensor. I was invited.

Further, since the accumulation time corresponds to the scanning speed of one line, there is a problem that the signal charge becomes small for high-speed reading and the S / N ratio is lowered.

On the other hand, an attempt to develop a one-dimensional perfect contact type image sensor in two dimensions has been conventionally made, and as its configuration, for example, the one shown in the equivalent circuit diagram of FIG. 6 is considered. . According to this configuration, the vertical scanning circuit 51 and the horizontal scanning circuit 52 are provided, and the vertical scanning circuit 5 is provided.
1 includes Y electrode lines 53a, 53 which are vertical electrode lines.
b and 54c are connected to the horizontal scanning circuit 52,
X electrode lines 55a, 55b, which are horizontal electrode lines, via the normally open analog switches 54a, 54b, 54c,
55c is connected.

The vertical scanning circuit 51 includes a Y electrode line 53a,
53b and 53c are selectively scanned, and the horizontal scanning circuit 52 includes analog switches 54a and 54b.
According to the opening / closing operation of 54c, the corresponding X electrode line 55
The voltage is applied by selecting a, 55b and 55c. The vertical scanning circuit 51 constitutes Y electrode line scanning means, and the horizontal scanning circuit 52 and the analog switches 54a, 54b and 54c constitute X electrode line scanning means.

Thin film transistor switching elements (TFT) 56a, 56b, 5 are provided on the Y electrode line 53a.
The gate electrode of 6c is connected, and the gate electrodes of TFTs 56d, 56e and 67f are connected to the Y electrode line 53b. The drain electrodes of the TFTs 56a and 56d are connected to the X electrode line 55a, and the drain electrodes of the TFTs 56b and 56e are connected to the X electrode line 55b.
The drain electrodes of c and 56f are connected to the X electrode line 55c. The source electrode of the TFT 56 is connected to one end of the corresponding light receiving element 57a-f, and the other end of the light receiving element 57a-f is connected to the output amplifier 59 through the signal line 58.

A method of driving the two-dimensional image sensor will be described below.
By applying a voltage to the electrode line 53a, the TFT 56 in the first row
Turn on a, 56b and 56c. In this state, the analog switches 54a, 54b, 54c are sequentially selected and turned on, and a voltage is sequentially applied to the X electrode lines 55a, 55b, 55c. Then, each light receiving element 57a, 57b, 57c
The current flowing through is sequentially output as an output signal to the amplifier 59 via the signal line 58. After the reading is completed, the Y electrode line 53a is set to the low potential state, and the TFTs 56a, 56 of the first row are set.
Turn off b and 56c.

Next, a voltage is applied to the second Y electrode line 53b to turn on the TFTs 56d, 56e and 56f in the second row. In this state, the X electrode lines 55a,
55b and 55c are sequentially selected, a voltage is applied, and the output signals of the light receiving elements 57d, 57e and 57f are read. In this way, the Y electrode line 53 and the X electrode line 55 are scanned,
The entire two-dimensional image of the original is read as a time-series signal (see Japanese Patent Laid-Open No. 64-62980).

[0016]

However, in the above-mentioned conventional two-dimensional contact type image sensor, in order to perform reading without using the mechanical scanning means for feeding the original, it is the same as the object to be read (original). Although a light-receiving region of a certain size is required, the number of pixels in the two-dimensional contact type image sensor increases when trying to obtain the same resolution as that of the one-dimensional image sensor, which causes a decrease in yield. There was a problem.

The main factors that cause a decrease in yield will be described. Short circuit between the upper and lower electrodes of the light receiving element and the switching element section, a gate line arranged in the horizontal direction and a data line and a bias arranged in the vertical direction. Most of the causes were short-circuits between the wires and the interlayer insulating film and open (break) of each wire.

There is also a method of removing the defective portion by cutting the wiring connecting the defective portion to the short-circuited portion using a laser or the like, but in the prior art, each pixel has a light receiving element and a switching element. Since there is only one pixel, if a defective pixel is not separated and output, there is a problem that a line defect can be prevented but a point defect cannot be prevented.

When repairing with a laser or the like, for example, when cutting the gate line and the bias line with a laser beam, an insulating film is generally formed on the gate line and the bias line. In particular, when an organic film such as polyimide is used for this insulating film, the metal of the gate line and bias line sublimated by laser irradiation adheres to the side wall of the insulating film and becomes conductive, and Could not be fixed. Therefore, the current process technology and repair technology have a limit in repairing a defective portion as in the present case, and it is difficult to improve the manufacturing yield.

The present invention has been made in view of the above circumstances, and provides a two-dimensional contact type image sensor which can easily correct defective portions, prevent line defects and point defects, and improve product yield. The purpose is to do.

[0021]

According to the present invention for solving the above problems, a plurality of light receiving elements on a transparent substrate, switching elements respectively connected to the plurality of light receiving elements, and an original are irradiated. Irradiation windows for two-dimensionally arranged, a gate line for controlling the switching element, a data line for outputting charges generated in the light receiving element, and a bias line for applying a bias voltage to the light receiving element. A two-dimensional contact image sensor having: a plurality of the light receiving elements and a plurality of the switching elements, which constitute one pixel;
It is characterized in that an opening region for correction is provided in the one pixel.

[0022]

According to the present invention, in a two-dimensional contact type image sensor having a plurality of two-dimensionally arranged light receiving elements and a switching element, a plurality of light receiving elements and corresponding switching elements constitute one pixel. Since the correction opening area is provided in each pixel, even if a defect such as a short circuit occurs between the upper and lower electrodes of the light receiving element and the switching element, the correction opening area can easily perform the correction. Even if the defective element is cut off, the other elements in one pixel can operate, so that the product yield can be improved.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. 1 is a plan view of one pixel of a two-dimensional contact image sensor according to an embodiment of the present invention.
FIG. 3 is a cross-sectional explanatory diagram of an XY portion of FIG. 1.

As shown in FIG. 1, one pixel of the two-dimensional contact type image sensor of this embodiment has photodiodes 2a and 2b which are light receiving elements and a thin film transistor (TFT) 3a which is a switching element for pixel selection. 3b each 2
It is basically composed of individual pieces.

The photodiode 2a is connected to the TFT 3a as well as to the TFT 3b, and the photodiode 2b is connected to both the TFT 3b and the TFT 3a. Then, a TFT for selecting pixels
Of the gate electrodes 3aG, 3bG are connected in common to all pixels in one column in the horizontal direction to form a gate line 4, and two TFTs 3a, 3b are simultaneously turned on in one pixel. It is supposed to do.

Further, the source electrodes 3a of the TFTs 3a and 3b.
S and 3bS are connected to the data line 5 arranged in the vertical direction, all the pixels in the vertical direction are connected to the common data line, and the charges of both the photodiodes 2a and 2b are transferred from the data line 5. It is supposed to be done.

Then, as shown in FIG. 1, the TFT 3a,
In the portion of 3b where the gate electrodes 3aG and 3bG are connected to the gate line 4, an opening 8 for correction is formed for removing the insulating film on these metal layers and performing correction using laser light. . In addition, the photodiodes 2a and 2b and the TFT
Insulating films on these metal layers are removed at the portions of 3a and 3b where the drain electrodes 3aD and 3bD are connected to form a correction opening region 9.

Here, the specific structure of the photodiode and the TFT will be described with reference to the sectional explanatory view of FIG. In the TFT 3, a gate electrode 24 of chromium (Cr1) is formed on the substrate 1, and a gate insulating layer 25 of silicon nitride (SiNx), a channel layer 26 of amorphous silicon (a-Si), and SiNx are formed on the gate electrode 24. And a channel protective film 27 of n + a-S are formed in this order.
The i-type ohmic contact layer 28 has a reverse staggered transistor structure in which the drain electrode 31 and the source electrode 32 of chromium (Cr2) are formed on the ohmic contact layer 28.
Incidentally, SiNx of the gate insulating layer 25 becomes the first insulating layer 29 in the portions other than the TFT 3.

The drain electrode 31 of the TFT 3 is connected to the lower electrode 21 of the photodiode 2, that is, the drain electrode 31 of the TFT 3 and the lower electrode 21 of the photodiode 2 are formed of a common Cr2 layer. . On this lower electrode 21, a photoconductive layer 22 of a-Si and a transparent upper electrode 2 of indium tin oxide (ITO) 2 are formed.
And 3 are formed.

Further, a second insulating layer 30 made of polyimide is formed so as to cover the photodiode 2 and the TFT 3, and the upper electrode 23 of the photodiode 2 extends vertically through a contact hole formed in the second insulating layer 30. The source electrode 3 of the TFT 3 is connected to the arranged bias line 6.
Similarly, 2 is connected to the data line 5. As a result, two insulating films, that is, the first insulating layer 29 made of SiNx and the second insulating layer 30 made of polyimide are provided at the intersection of the bias line 6 and the gate line 4 of the TFT 3 which are vertically arranged. It is configured to be.

A correction opening 8 is provided above the connection between the gate electrodes of the TFTs 3a and 3b and the gate line 4, and the drain electrode 31 of the TFTs 3a and 3b and the lower electrodes of the photodiodes 2a and 2b are provided. An opening area 9 for correction is provided above the connection portion with 21. The correction opening region 8 is formed by partially removing the first insulating layer 29 and the second insulating layer 30 by photolithography, and the correction opening region 9 is formed by partially removing the second insulating layer 30 by photolithography etching. It is formed by removing. The photodiodes 2a and 2b divided into two pieces
The area between is used as an illumination window 7 for illuminating the original with light from the lower portion of the substrate 1.

Next, a method of manufacturing the two-dimensional contact type image sensor of the above embodiment will be described. Cr1 is deposited on the glass substrate 1 by sputtering to a thickness of about 500 to 1000 Å, and patterned into a predetermined shape.
An FT gate electrode 24 and a gate line 4 are formed.

Subsequently, by plasma CVD, SiNx, a-Si: H, and SiNx to be the gate insulating layer 25, the channel layer 26, and the channel protective film 27 are respectively made into several thousand angstroms and 500 to 1000 angstroms. Then, the channel protection film 27 is formed by patterning the upper SiNx into a desired shape by photolithography. The gate insulating layer 25 of the TFT forms the first insulating layer 29 in the portion other than the TFT.

After that, in order to make an ohmic contact with the a-Si: H, n + a-Si: H of the ohmic contact layer 28 is deposited by about several thousand angstroms by the plasma CVD method.

Further, a source electrode 32 and a drain electrode 31 of the TFT and Cr2 which becomes the lower electrode 21 of the photodiode serving as a light receiving element are deposited by the sputtering method to a thickness of about several thousand angstroms, and the photoconductivity of the photoelectric conversion portion is further formed. In order to form the layer 22, an a-Si: H layer is formed by plasma CVD using SiH ₄ gas to a thickness of several hundreds to several thousands angstroms.

Next, ITO of about several hundred angstroms is formed as a transparent electrode as the upper electrode 23 by the sputtering method, and then ITO and aS are formed by photolithography etching.
The upper electrode 23 and the photoconductive layer 22 are formed with i: H as a desired pattern. Next, by photolithography etching, Cr
2, n + a-Si: H is continuously etched to form a desired pattern. As a result, the TFT portion and the photodiode portion are formed. The light receiving element may be a PIN photodiode.

Next, the first insulating layer 29 and the SiNx to be the gate insulating layer 25 of the TFT are patterned by photolithographic process etching. At this time, a correction opening 8 is formed on the gate line by removing SiNx. Next, a polyimide to be the second insulating layer 30 is formed into a desired pattern by photolithography. At this time, the contact hole for the data line 5 and the bias line 6 is formed, and at the same time, the correction opening region 9 is formed.

After that, aluminum (A1) to be the data line 5 and the bias line 6 of the light receiving element is deposited to a thickness of several μm by the sputtering method, and is formed into a desired wiring pattern by photolithography. As a result, a two-layer insulating film of the first insulating layer 29 and the second insulating layer 30 is provided at the intersection of the bias line 6 of the light receiving element and the gate line 4 of the TFT.

The main body of the two-dimensional contact type image sensor of this embodiment is formed by forming the transparent protective film 33 or laminating thin glass on it. In addition, the defect correction, which is a cutting work for cutting off the short-circuited portion using the laser beam, is performed by the transparent protective film 3
By carrying out before the step of forming 3 or before the step of laminating the thin glass sheets, a two-dimensional contact image sensor can be produced without losing the passivation effect.

That is, as shown in FIG. 2, since the correction opening area 9 provided at the portion connecting the photodiode 2 and the TFT 3 is always covered with the transparent protective film 33, the entire sensor is covered. It will have a passivation effect. The same applies to the correction opening area 8 provided on the gate line 4.

Further, as shown in the plan view of FIG. 3, when a defect is present in the photodiode 2a, the defect can be repaired by opening the repair opening 9 between the photodiode 2a and the TFT 3a. By performing laser irradiation and cutting the photodiode 3a side at the wiring portion connecting the drain electrodes 3aD, 3bD and the photodiode 3a, only the defective photodiode 3a portion can be cut off.

Further, as shown in the plan view of FIG. 4, if there is a short-circuit defect between the drain electrode 3aD of the TFT 3a and the gate line 4, it is provided on the gate line 4 of the TFT 3a. The repair opening 8 is irradiated with laser to cut the gate line 4, and the repair opening 9 is further irradiated with laser to cut the drain electrode 3aD and the TFT 3
b and the photodiode 2b, the charges generated in the photodiode 2a and the photodiode 2b can be separated by T
One FT 3b can be operated and output, and this pixel can be normally read.

After the above correction work is completed, the analog multiplexer and the shift register are mounted on the same substrate or on another substrate to form a drive circuit, and the two-dimensional contact image sensor of this embodiment is completed. To do.

The output of the corrected defective pixel is about 1/2 of the output of a normal pixel when one photodiode of the two photodiodes in one pixel is corrected and separated from other elements. Therefore, it is possible to prevent point defects by using a correction circuit that corrects the output so as to match the output of other pixels.

According to this embodiment, a plurality of photodiodes 2 and the TFTs 3 connected to each of them are two-dimensionally arranged in a matrix on a translucent substrate having the same size as the object to be read (original). However, in the two-dimensional contact image sensor in which the gate line 4 for line selection is arranged in the horizontal direction and the data line 5 and the bias line 6 of the photodiode 2 are arranged in the vertical direction, the photodiode 2 in one pixel is And the TFT 3 are configured to be plural,
Photodiode and TFT in which a defect such as a short circuit exists between the upper and lower electrodes of the photodiode 2 and TFT 3.
Since only defective pixels need to be repaired and no defective pixels are separated so that no output is generated, it is possible to prevent not only line defects but also point defects by repairing even if the total number of pixels increases. There is an effect that the upper yield can be improved.

Further, according to the present embodiment, if at least one set of photodiodes 2 and the TFTs 3 connected to each of them operate normally, the correction circuit can be used to obtain an output equivalent to that of other normal pixels. Therefore, even if the total number of pixels increases, not only line defects but also point defects can be prevented by correction, and an appropriate output can be obtained, so that the yield can be improved.

Furthermore, an insulating layer is partially removed above the wiring portion connecting the photodiode 2 and the TFT 3 to provide a correction opening region 9, and a correction opening is similarly provided above the connection portion between the TFT 3 and the gate line 4. Since the area 8 is provided, the metal of the gate line 4 sublimated by the laser irradiation and the photodiode 2 and the TF even when repaired by using a laser or the like.
There is an effect that the metal of the wiring portion connecting T3 can be surely corrected without adhering to the side wall of the second insulating layer 30.

Further, the bias line 6 of the photodiode 2
The first insulating layer 29 is formed at the intersection of the gate line 4 of the TFT 3 and the gate line 4.
Since two layers of insulating films, that is, the second insulating layer 30 and the second insulating layer 30, are provided, the interlayer insulating film between the gate line 4 arranged in the horizontal direction and the data line 5 and the bias line 6 arranged in the vertical direction is formed. This has the effect of preventing short-circuiting via the device and improving the yield.

[0049]

According to the present invention, in a two-dimensional contact type image sensor having a plurality of two-dimensionally arranged light receiving elements and a switching element, one pixel is formed by the plurality of light receiving elements and the corresponding switching elements. Since it is configured and a correction opening area is provided in each pixel, even if a defect such as a short circuit occurs between the upper and lower electrodes of the light receiving element and the switching element, the correction opening area can easily perform the correction. There is an effect, and since the other elements in one pixel can operate even if the defective element is separated, there is an effect that the yield of products can be improved.

[Brief description of drawings]

FIG. 1 is an explanatory plan view of one pixel of a two-dimensional contact image sensor according to an embodiment of the present invention.

2 is a cross-sectional explanatory view of an XY portion of FIG.

FIG. 3 is an explanatory plan view of one pixel of a two-dimensional contact image sensor showing an example of a correction method in this embodiment.

FIG. 4 is an explanatory plan view of one pixel of a two-dimensional contact image sensor showing another example of the correction method in the present embodiment.

FIG. 5 is a cross-sectional explanatory view of a conventional one-dimensional contact image sensor.

FIG. 6 is an equivalent circuit diagram of a conventional two-dimensional contact image sensor.

[Explanation of symbols]

1 ... Substrate, 2 ... Photodiode, 3 ... TFT,
4 ... Gate line, 5 ... Data line, 6 ... Bias line,
7 ... Illumination window, 8 ... Correction opening area, 9 ... Correction opening area, 21 ... Lower electrode, 22 ... Photoconductive layer, 23 ... Upper electrode, 24 ... Gate electrode, 25 ... Gate insulating layer,
26 ... Channel layer, 27 ... Channel protective film, 28
... Ohmic contact layer, 29 ... First insulating layer, 30
... second insulating layer, 31 ... drain electrode, 32 ... source electrode, 33 ... transparent protective film

Claims (1)

[Claims] 1. A plurality of light receiving elements, a switching element connected to each of the plurality of light receiving elements, and an irradiation window for irradiating an original are two-dimensionally arranged on a light-transmissive substrate. A two-dimensional contact image sensor having a gate line for controlling, a data line for outputting charges generated in the light receiving element, and a bias line for applying a bias voltage to the light receiving element. And a plurality of the switching elements to form one pixel,
A two-dimensional contact image sensor, wherein an opening region for correction is provided in the one pixel.