JPH07231077A - Adherence type image sensor - Google Patents

Abstract

PURPOSE:To provide the adherence type image sensor, which can improve the S/N characteristic of a photodiode by improving the step coverage of an Sin. forming an insulating layer, and can improve the sensitivity of the photodiode by enlarging the area per photodiode. CONSTITUTION:A plurality of blocks comprising the sets of the same number of photodiodes 12 as the number of the channels of an output circuit and blocking diodes 14 are provided. The photodiodes 12 are connected to lines 101-10n which are provided in correspondence with the number of the channels of the output circuit, at each block unit by matrix connection. In this adherence type image sensor, the elements are isolated,by scraping the semiconductor layer at the surface between the photodiodes, for the photodiodes 121-12n.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact type image sensor used in a small facsimile or the like for reading a document without reducing it.

[0002]

2. Description of the Related Art A conventional contact image sensor will be described below with reference to FIGS. 6 is a schematic plan view showing a part of a conventional contact type image sensor, FIG. 7 is a schematic sectional view taken along line CC of the contact type image sensor shown in FIG. 6, and FIG. 8 is D of the contact type image sensor shown in FIG. -D schematic sectional view, FIG. 9 is a diagram showing the manufacturing process of the contact image sensor shown in FIG. 6 with a view corresponding to FIG. 7, and FIG. 10 is a schematic process of manufacturing the contact image sensor shown in FIG. It is the figure expressed using the top view.

A conventional contact-type image sensor has a plurality of blocks having the same number of sensor elements as the number of channels of the output circuit, and each sensor element is provided on each of a plurality of lines provided corresponding to the number of channels of the output circuit. It is a matrix connection in block units. The sensor element includes a photodiode that converts an optical signal into an electric signal according to the intensity of light, and a blocking diode that functions as a switching element for reading the signal accumulated in the photodiode.・
It was connected to the toe bag.

One block of a conventional contact image sensor will be described below with reference to FIGS. 6 to 8. The photodiodes 52 _{1 to} 52 _n are respectively formed on the lower electrodes 63 _{1 to} 63 _n arranged on the glass substrate 62. The lower electrodes 63 _{1 to} 63 _n are connected to the lines 50 ₁ to
50 _n respectively. As a result, the photodiodes 52 _{1 to} 52 _n are connected to the output circuit in a matrix. Above the photodiodes 52 _{1 to} 52 _n ,
A transparent electrode 64 made of ITO or the like and joined to the upper electrode 65 is formed. Blocking diodes 54 _{1 to} 54
_n is formed on the lower electrode 66 arranged on the glass substrate 62. Blocking diodes 54 _{1 to} 54
A transparent electrode 67 made of ITO or the like that is joined to the upper electrode 65 that is joined to the transparent electrode 64 of the corresponding photodiode 52 is formed above the _n . As a result, the photodiodes 52 _{1 to} 52 _n are connected front-to-front or back-to-back with the corresponding blocking diodes 54 _{1 to} 54 _n . Note that Cr is generally used for the line 50, the upper electrode 65, and the lower electrodes 63 and 66 (hereinafter, simply referred to as the photodiode 52, the blocking diode 54, and the line 50).

Next, the manufacturing process of the contact image sensor shown in FIG. 6 will be described. First, FIG. 9A and FIG.
As shown in 0 (a), Cr is deposited on the glass substrate 62 and patterned to form the lower electrodes 63 _{1 to} 6 3.
3 _n , 66 are formed. Next, FIG. 9B and FIG.
As shown in (b), the photodiodes 52 ₁ to 52 _n are formed on the lower electrodes 63 _{1 to} 63 _n , and the blocking diodes 54 _{1 to} 54 _n are formed on the lower electrode 66. That is, first, the lower electrodes 63 _{1 to} 63 _n , 66
On the glass substrate 62 on which is formed a-Si p layer, i
Layer and n layer are deposited in this order to form a semiconductor layer, and then IT0 is deposited and patterned to form a transparent electrode 64,
67 is formed. Next, the semiconductor layers are patterned to perform element isolation, and the photodiodes 52 _{1 to} 52 _1
n and blocking diodes 54 _{1 to} 54 _n are formed.

Next, as shown in FIGS. 9 (c) and 10 (c), the photodiode 52, the blocking diode 54 and the like are coated with SiO ₂ to form an insulating layer 61, and then the photodiode 52 and the blocking are formed. A contact hole 68 is formed on the diode 54 and the lower electrodes 63 _{1 to} 63 _n . Next, as shown in FIG. 9D and FIG. 10D, Cr is deposited on the insulating layer 61 and patterned to form the upper electrode 65 and the lines 50 ₁ to 50 _n . As a result, the contact image sensor shown in FIG. 6 is formed.

Since the conventional contact image sensor having the above-mentioned structure can read the original without using the reduction optical system, the optical path length is short, and therefore the apparatus can be downsized. Therefore, in recent years, it has been widely used as a reading device such as a small facsimile and a bar code reader.

[0008]

[Problems to be Solved by the Invention]
In the conventional contact type image sensor, the photodiode 52
₁~ 52_nPhotodiodes to separate the
The overhang around the 52 is large
And SiO₂Poor step coverage. For this reason,
A gap is created in the joint surface between the insulating layer 61 and the photodiode 52.
On the other hand, a space may be formed. Such space is shaped
When it is formed, the leakage current of the photodiode increases and S
There is a problem that the / N characteristic is deteriorated. In addition, conventional dense
In a wearable image sensor, between adjacent photodiodes 52
In addition, it is necessary to secure a separation interval for element separation.
Absent. For this reason, the lateral direction of the photodiode (the main direction)
The length of the
Since the area around is small, the sensitivity of the photodiode is
There is also a problem that is damaged. For example, 1 mm
If 8 photodiodes are arranged per
Without considering, the size of the photodiode is 125
Although the width is 125 μm and the width is 125 μm, the conventional contact type image sensor
Sensor, it is necessary to secure a separation interval of 20 μm.
Therefore, it is designed to have a length of 125 μm and a width of 105 μm.

The present invention has been made based on the above circumstances, and improves the S / N characteristics of a photodiode by improving the step coverage of SiO ₂ forming an insulating layer, and at the same time, the area per photodiode is increased. An object of the present invention is to provide a contact-type image sensor that can improve the sensitivity of the photodiode by increasing the size.

[0010]

In order to achieve the above object, a contact type image sensor according to the invention of claim 1 is provided with a plurality of photodiodes for converting an optical signal into an electric signal according to the intensity of light, and the photodiode. A contact-type image sensor including a switching element for reading out a signal stored in the plurality of photodiodes,
It is characterized in that element isolation is performed by scraping off a part or all of the semiconductor layer on the surface between the photodiodes.

According to a second aspect of the present invention, in the first aspect of the present invention, the photodiode is a pin structure diode, and the semiconductor layer on the surface is a p layer or an n layer. It is what

According to a third aspect of the present invention, in the contact type image sensor according to the first or second aspect, the switching element is a diode, and a part or all of the semiconductor layer on the surface between the diodes is scraped off. It is characterized in that the element is separated by doing so.

According to a fourth aspect of the present invention, in the contact type image sensor according to the third aspect, the switching element is a diode having a pin structure and the semiconductor layer on the surface is a p layer or an n layer. It is characterized by.

According to a fifth aspect of the present invention, in the contact type image sensor according to the third or fourth aspect, a part or the whole of the semiconductor layer on the surface is cut off between the photodiode and the switching element. It is characterized in that the element is separated by.

[0015]

According to the contact type image sensor of the first aspect of the present invention, since the plurality of photodiodes are used for element isolation by scraping off a part or all of the semiconductor layer on the surface between the photodiodes, Since the overhang in the peripheral portion is reduced, the step coverage of SiO ₂ forming the insulating layer is improved. Therefore, a gap is unlikely to be formed at the junction surface between the insulating layer and the photodiode, and thus the S / N characteristic of the photodiode can be improved. Further, since the separation distance for element separation between adjacent photodiodes can be reduced, the length of the photodiode in the lateral direction (main scanning direction) can be increased. Therefore, since the area per photodiode can be increased, the sensitivity of the photodiode can be improved.

In the contact image sensor according to the second aspect of the present invention, the photodiode is a pin structure diode and the surface semiconductor layer is a p layer or an n layer.
The semiconductor layer between adjacent photodiodes has a high resistance i
Since the layers are included, the insulation between the photodiodes can be improved.

The contact type image sensor according to the third aspect of the present invention has the same operation as the invention according to the first aspect due to the above-mentioned configuration.

According to a fourth aspect of the contact image sensor of the present invention, the switching element is a diode having a pin structure and the semiconductor layer on the surface is a p-layer or an n-layer, so that a semiconductor between adjacent switching elements is formed. Since the layer includes the i layer having a high resistance value, the insulation between the switching elements can be improved.

According to a fifth aspect of the contact image sensor of the present invention, between the photodiode and the switching element,
Since the element isolation is performed by scraping off a part or all of the semiconductor layer on the surface, the isolation interval when the photodiode and the switching element are isolated can be reduced.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A contact image sensor which is an embodiment of the present invention will be described below with reference to FIGS. 1 is a schematic plan view showing a part of a contact image sensor according to an embodiment of the present invention, FIG. 2 is a schematic sectional view taken along line AA of the contact image sensor shown in FIG. 1, and FIG. 3 is shown in FIG. FIG. 4 is a schematic cross-sectional view of the contact image sensor taken along the line BB, FIG. 4 is a diagram showing the manufacturing process of the contact image sensor shown in FIG. It is the figure which represented the manufacturing process of a sensor using the schematic plan view.

The contact-type image sensor of the present embodiment is provided with a plurality of blocks having the same number of sensor elements as the number of channels of the output circuit, and each sensor element is provided with a plurality of lines provided corresponding to the number of channels of the output circuit. Is a matrix connection in each block unit. The sensor element includes a photodiode that converts an optical signal into an electric signal according to the intensity of light, and a blocking diode that functions as a switching element for reading the signal accumulated in the photodiode. -It is connected to the toe bag.

One block of the contact image sensor of this embodiment will be described below with reference to FIGS. 1 to 3.
The photodiodes 12 _{1 to} 12 _n are respectively formed on the lower electrodes 23 ₁ to 23 _n arranged on the insulating substrate 22 made of glass or the like, and the photodiodes 12 _{1 to} 12 _n have a common p-layer and i-layer among the semiconductor layers. Is formed in. The lower electrodes 23 ₁ to 23 _n are connected to the lines 10 ₁ to 10 _n , respectively. As a result, the photodiodes 12 _{1 to} 12
_n are connected to the output circuit in a matrix. A transparent electrode 24 made of ITO or the like and joined to the upper electrode 25 is formed on the photodiodes 12 _{1 to} 12 _n . The blocking diodes 14 _{1 to} 14 _n are formed on the lower electrode 26 disposed on the insulating substrate 22, and each blocking diode 14 has the p layer and the i layer of the semiconductor layers formed in common. The corresponding photodiode 1 is provided above the blocking diodes 14 _{1 to} 14 _n.
A transparent electrode 27 made of ITO or the like is formed to be joined to the upper electrode 25 joined to the second transparent electrode 24. As a result, the photodiodes 12 _{1 to} 12 _n are paired with the blocking diodes 14 _{1 to} 14 _n and the front to
Connected to front or back to back. (Hereinafter, it may be simply referred to as the photodiode 12, the blocking diode 14, and the line 10.). The line 10, the upper electrode 25 and the lower electrodes 23, 26 are
Generally, Cr is used.

Next, the manufacturing process of the contact type image sensor of this embodiment will be described. First, FIG. 4 (a) and FIG.
As shown in (a), Cr is deposited on the glass substrate 22 and patterned to form the lower electrodes 23 ₁ to 23.
_n , 26 are formed. Next, as shown in FIG.
On the glass substrate 22 on which the lower electrodes 23 ₁ to 23 _n and 26 are formed, a-Si (amorphous silicon) is a p layer, i
After a layer and an n layer are deposited in this order to form a semiconductor layer, IT0 is deposited on this semiconductor layer. In this embodiment, the p layer is 50
Angstrom, i layer is 6000 angstrom,
Then, the n layer was deposited so as to have a thickness of 300 Å. Next, as shown in FIG. 4C, the transparent electrodes 24 and 27 are formed by patterning ITO.

Next, as shown in FIG. 4D, after reactive ion etching (RIE) is performed to etch the n layer of the semiconductor layer where the transparent electrodes 24 and 27 are not formed, As shown in FIG. 4E and FIG. 5B, by patterning the semiconductor layer, the photodiodes 12 _{1 to} 12 _n and the blocking diode 1 are formed.
4 _{1 to} 14 _n are formed. At this time, element isolation is performed by scraping off the n layer that is the semiconductor layer on the surface between the photodiodes 12 _{1 to} 12 _{n and} between the blocking diodes 14 _{1 to} 14 _{n, and} between the photodiodes 12 and the blocking diode 14. , All semiconductor layers,
That is, the p layer, the i layer, and the n layer are scraped off. As a result, in the photodiodes 12 _{1 to} 12 _n , the p layer and the i layer of the semiconductor layers are formed in common, and the blocking diodes 14 _{1 to} 14 _n are also
Of the semiconductor layers, the p layer and the i layer are commonly formed.

Next, as shown in FIGS. 4 (f) and 5 (c), the photodiode 12 and the blocking diode 1 are provided.
Insulating layer 2 by coating 4 such as of SiO ₂
1 is formed, a contact hole 28 is formed on the photodiode 12, the blocking diode 14, and the lower electrodes 23 ₁ to 23 _n . Next, FIG. 4 (g) and FIG.
As shown in (d), Cr is deposited on the insulating layer 21 and patterned to form the upper electrode 25 and the line 1.
0 ₁ to 10 _n are formed. As a result, the contact image sensor shown in FIGS. 1 to 3 is formed.

In the contact type image sensor having the above structure, the pulse voltages are simultaneously applied to the blocking diodes 14 _{1 to} 14 _{n so} that the blocking diodes 14 _{1 to} 14 _n are brought into a conductive state, so that the charges accumulated in the photodiodes 12 _{1 to} 12 _n are photoelectrically converted. It is taken out as an electric signal and outputted to the output circuit via the lines 10 ₁ to 10 _n . This operation is continuously performed in block units for all blocks.

According to the present embodiment, the n-layer, which is a semiconductor layer on the surface between the photodiodes 12, is removed by element isolation, so that the overhang in the peripheral portion of the photodiode 12 is reduced, so that the insulating layer 21 is formed.
The step coverage of SiO ₂ which forms the film is improved.
Therefore, the insulating layer 21 and the photodiodes 12 _{1 to} 12
_A gap is unlikely to be formed on the joint surface with _n, and thus the S / N characteristic of the photodiode can be improved.

Since the separation distance between adjacent photodiodes 12 for element separation can be made smaller than that of the conventional one, the lateral length (main scanning direction) of the photodiodes 12 can be increased. it can. Therefore, since the area per photodiode can be increased, the sensitivity of the photodiode can be improved. According to an experiment by the present inventor, when 8 photodiodes are arranged per 1 mm, the photodiode 1
The size of each piece could be 125 μm in length and 120 μm in width.

Further, according to the present embodiment, the i-layer having a high resistance value is included in the semiconductor layer between the photodiodes 12 and between the blocking diodes 14, so that the insulation between the respective elements can be improved.

The present invention is not limited to this embodiment, and various modifications can be made within the scope of the invention. For example, in this embodiment, a-Si is a p-layer on the lower electrode,
The photodiode 1 is formed by depositing the i layer and the n layer in this order.
2 and the blocking diode 14 are formed and the element isolation is performed by scraping off the n layer which is the semiconductor layer on the surface between the photodiodes and between the blocking diodes, but the present invention is not limited to this. By forming a photodiode and a blocking diode by depositing n-layer, i-layer, and p-layer in this order on the lower electrode, a p-layer that is a semiconductor layer on the surface between the photodiodes and between the blocking diodes is scraped off. The element may be separated.

Further, in the present embodiment, the case where the elements are separated by scraping off the semiconductor layer on the surface between the respective elements has been described, but the present invention is not limited to this, and insulation between the respective elements is performed. If sufficient protection can be ensured, element isolation may be performed by cutting off a part of the semiconductor layer on the surface.

Further, in the present embodiment, the blocking diode 14 having the pin structure is used as the switching element. However, the present invention is not limited to this, and a p-type blocking diode 14 may be used instead of the blocking diode.
An n-structure diode or a thin film transistor (TFT) may be used.

Further, in the present embodiment, the photodiode 12
Although the semiconductor layer between the blocking diode 14 and the blocking diode 14 is entirely removed to separate the elements, the present invention is not limited to this, and a part of the semiconductor layer on the surface between the photodiode and the blocking diode is described. Alternatively, the element may be separated by scraping off the whole. As a result, the separation interval can be reduced. However, when a thin film transistor is used as the switching element, the semiconductor layer has a different structure from that of the photodiode, so that the semiconductor layer must be completely removed between the photodiode and the switching element.

[0034]

As described above, according to the first aspect of the invention, with the above-mentioned structure, the step coverage of SiO ₂ forming the insulating layer is improved. Therefore, the junction between the insulating layer and the photodiode is improved. Since it becomes difficult to form a gap in the surface, the S / N characteristic of the photodiode can be improved, and the separation distance for separating the elements between adjacent photodiodes can be reduced, so that It is possible to provide a contact-type image sensor capable of increasing the area and thereby improving the sensitivity of the photodiode.

According to the second aspect of the present invention, since the semiconductor layer between the adjacent photodiodes includes the i layer having a high resistance value, the insulation between the photodiodes is improved. It is possible to provide a contact type image sensor capable of performing the above.

According to the third aspect of the invention, with the above configuration, it is possible to provide a contact image sensor having the same effect as that of the first aspect of the invention.

According to the invention described in claim 4, since the semiconductor layer between the adjacent switching elements includes the i layer having a high resistance value due to the above structure, the insulation between the switching elements is high. It is possible to provide a contact image sensor capable of improving the above.

According to the fifth aspect of the present invention, by virtue of the above configuration, it is possible to provide a contact type image sensor which can reduce the separation distance when the photodiode and the switching element are separated. You can

[Brief description of drawings]

FIG. 1 is a schematic plan view showing a part of a contact image sensor according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view taken along the line AA of the contact image sensor shown in FIG.

FIG. 3 is a schematic BB sectional view of the contact image sensor shown in FIG.

FIG. 4 is a diagram showing a manufacturing process of the contact image sensor shown in FIG. 1 by using a diagram corresponding to FIG. 2;

5A to 5D are views showing a manufacturing process of the contact image sensor shown in FIG. 1 by using a schematic plan view.

FIG. 6 is a schematic plan view showing a part of a conventional contact image sensor.

7 is a schematic cross-sectional view taken along line CC of the contact image sensor shown in FIG.

8 is a schematic cross-sectional view of the contact image sensor shown in FIG. 6 taken along the line D-D.

FIG. 9 is a diagram showing the manufacturing process of the contact image sensor shown in FIG. 6 using a diagram corresponding to FIG. 7.

FIG. 10 is a diagram showing the manufacturing process of the contact image sensor shown in FIG. 6 using a schematic plan view.

[Explanation of symbols]

10 ₁ to 10 _n line 12 _{1 to} 12 _n photodiode 14 _{1 to} 14 _n blocking diode 21 insulating layer 22 insulating substrate 23 ₁ to 23 _n , 26 lower electrode 24, 27 transparent electrode 25 upper electrode 28 contact hole

Claims (5)

[Claims] 1. A contact type image sensor comprising: a plurality of photodiodes for converting an optical signal into an electric signal according to the intensity of light; and a switching element for reading a signal accumulated in the photodiodes. The contact type image sensor characterized in that the photodiode is obtained by element isolation by scraping off a part or all of the semiconductor layer on the surface between the photodiodes. 2. The contact image sensor according to claim 1, wherein the photodiode is a pin structure diode, and the semiconductor layer on the surface is a p layer or an n layer. 3. The switching element is a diode, and element isolation is performed by cutting off a part or all of the semiconductor layer on the surface between the diodes. The contact image sensor described. 4. The switching element is a diode having a pin structure, and the semiconductor layer on the surface is a p layer or an n layer.
The contact image sensor according to claim 3, which is a layer. 5. The device isolation according to claim 3, wherein a part or the whole of the semiconductor layer on the surface is isolated between the photodiode and the switching device by element removal. Contact image sensor.