JPH06236980A - Photosensor - Google Patents

Abstract

PURPOSE:To have high sensitivity and high resolution by forming a light-guiding window for irradiating light from a light source on a detected object in the centers of the respective sensor devices. CONSTITUTION:Light applied to the respective sensor parts 11 from a source of light is transmitted through a first light-guiding window 14 formed on a light-shielding layer 13 and a second light-guiding window 17 formed on a channel region 16a of a silicon thin film layer 16 and is applied to source document 30. Further, the light-shielding layer 13 is not formed between the sensor parts 11, 11 so that light goes through also this part for being irradiated on the source document 30. Then, the light is irregularly reflected by the source document 30 while reflected light reflected in the direction shown by an arrow is incident on the channel regions 16a of the respective sensor parts 11. Of the reflected light to be incident on the channel regions 16a, the reflected light of the light transmitted the first and second light-guiding windows 14, 17 has a small angle of reflection on the surface of the source document 30 and a short optical path length because the second light-guiding window 17 is formed about in the central part of the channel region 16a. Accordingly, the reflected light incident on the channel region 16a has large intensity of light.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called contact type photosensor used in a facsimile apparatus, a scanner apparatus or the like.

[0002]

2. Description of the Related Art In a facsimile apparatus, a scanner apparatus or the like, a so-called contact type photosensor is used for downsizing, and the conventional contact type photosensor is constructed as shown in FIG. ing.

That is, in FIG. 4, the photo sensor 1
The light-shielding layer 3 is linearly formed on the transparent substrate 2, and the light-shielding layer 3 is formed with a plurality of light guide windows 4 at predetermined intervals. A photoelectric conversion layer 5 is formed on each light-shielding layer 3, and constitutes a sensor element portion 6. A protective film 7 is formed so as to cover the transparent substrate 2, the light shielding layer 3 and the photoelectric conversion layer 5. And each light guide window 4 is normally one side.
It is formed in a quadrangle of about 00 μm.

In this photosensor 1, light emitted from a light source (not shown) such as a fluorescent lamp or a light emitting diode provided on the transparent substrate 2 side is applied to the original 8 through the light guide window 4, and the original 8 is applied to the original 8. The emitted light is reflected by the original 8,
Of this reflected light, only the reflected light reflected in the oblique direction where the sensor element portion 6 adjacent to the light guide window 4 through which the light is transmitted is incident on the photoelectric conversion layer 5, and the photoelectric conversion layer 5 Is photoelectrically converted by, and the amount of light is detected.

[0005]

However, in such a conventional photo sensor 1, since the sensor element portions 6 are formed adjacent to each other with the light guide window 4 interposed therebetween, each pixel, that is, each There are problems that the resolution of each sensor element unit 6 is poor and that the light receiving efficiency is poor and the sensitivity is poor.

That is, in the conventional photosensor 1, as shown in FIG. 4, the light-shielding sensor element portions 6 are formed adjacent to each other with the light guide window 4 interposed therebetween, and irradiation from the light source is performed. Since the light is shielded by the light-shielding layer 3, the light emitted from the light guide window 4 to the document 8 is reflected in various directions, but among them, two sensor element portions 6 adjacent to the light guide window 4 are adjacent to each other. Only the light that is obliquely reflected in the direction is incident on the photoelectric conversion layer 5 of each sensor element unit 6, and the optical path length of the reflected light from the document 8 to the photoelectric conversion layer 5 becomes long. Since the light intensity of the reflected light is attenuated by the square of the optical path length of the reflected light, the reflected light intensity with respect to the distance from the pixel is maximum at the center between the sensor element portions 6, that is, at the end side of each sensor element portion 6. And the distance decreases from the end position in proportion to the square of the distance. As a result, there is a problem that the light receiving efficiency of the photoelectric conversion layer 5 is reduced and the sensitivity of the photosensor 1 is poor due to the long optical path of the reflected light.

Further, as described above, the light incident on the original 8 through the light guide window 4 is reflected by the photoelectric conversion layer 5 of the sensor element portion 6 adjacent to the light guide window 4, respectively. As shown in FIG. 5, the closer the incident light is to the photoelectric conversion layer 5, the shorter the optical path length of the reflected light reflected by the photoelectric conversion layer 5, and the incident position of the incident light is the central portion of the light guide window 4. The closer to, the closer the optical path length of the reflected light reflected by the adjacent photoelectric conversion layers 5 becomes. Therefore, the light intensity of the reflected light of the light incident on the position near the center of the light guide window 4 becomes the same in the adjacent photoelectric conversion layers 5. And
In the photo sensor 1, since the sensor element portions 6 and the light guide windows 4 are alternately arranged, the photoelectric conversion layer 5 of each sensor element portion 6 is provided with the light guide window 4 formed adjacent thereto. Such reflected light is incident. As a result, the reflected light of the light incident from the two light guide windows 4 adjacent to the photoelectric conversion layer 5 is incident on each photoelectric conversion layer 5 with the light intensity as described above, and each photoelectric conversion layer 5 is incident. In which of the light guide windows 4 of the adjacent light guide windows 4 the incident light is reflected light,
There is a problem that it is difficult to make a distinction only by the light intensity of the incident light and the resolution of each photoelectric conversion layer 5 is poor.

Therefore, the present invention uses a so-called MOS type thin film and forms a light guide window for irradiating the object to be detected such as a document with light from a light source at the center of each sensor element portion, thereby improving the performance. It is intended to provide a photosensor with high sensitivity and high resolution.

[0009]

A photosensor according to the present invention comprises a substrate having light transmissivity, a light-shielding layer formed on the substrate for shielding irradiation light, and a light-shielding layer formed on the light-shielding layer from the substrate side. A first light guide window which transmits irradiation light; a silicon thin film layer which is formed on the light shielding layer and has a channel region and a source region and a drain region which face each other across the channel region; A second light guide window formed in a position opposite to the first light guide window in the channel region and transmitting the irradiation light transmitted through the first light guide window, and a transparent gate electrode formed on the silicon thin film layer. And are formed by being laminated, and the light emitted from the substrate side passes through the first light guide window and the second light guide window and is irradiated to the detection target located on the transparent gate electrode side. , The reflected light from the detected object Serial a photo sensor for receiving the channel region of the silicon thin film, the first light guide window and the second light guide window is longer in the longitudinal direction of the channel region,
The above-described object is achieved by forming the channel region in a short shape in the width direction.

[0010]

According to the present invention, the first light guide window formed in the light shielding layer and the second light guide window formed in the channel region of the silicon thin film layer.
Irradiation light passes through the light guide window, and the reflected light reflected on the substrate side is applied to the channel region of the silicon thin film.

That is, since the center of the reflected light coincides with the center of the channel region which is the photoelectric conversion portion of the photosensor, the optical path length of the reflected light irradiated on the channel region of the silicon thin film is greatly increased. The length can be shortened, and the light intensity of the reflected light reflected by the channel region can be increased. As a result, the sensitivity of the photo sensor can be improved. In this case, the second formed in the channel region
Since the light guide window is formed long in the channel length direction and short in the channel width direction, it is possible to suppress a decrease in photocurrent due to the formation of the second light guide window.

Further, since the periphery of each of the first light guide window and the second light guide window is shielded by the light shielding layer, the adjacent second light guide window is closed.
Even if the reflected light of the light incident from the light guide window is incident on the channel region, the optical path length of the reflected light is equal to that of the reflected light of the light incident through the second light guide window formed in the channel region. The reflected light of the light, which is much longer than the optical path length and is incident from the adjacent second light guide window, is attenuated more than the reflected light of the light incident through the second light guide window formed in the channel region. As a result, it is possible to reliably separate the reflected light of the light incident through the second light guide window formed in each channel region and the reflected light of the light incident through the adjacent second light guide window, The resolution of each pixel of the photo sensor can be improved.

[0013]

EXAMPLES The present invention will be described below based on examples.

1 to 5 are views showing an embodiment of the photosensor of the present invention.

FIG. 1 is a partial top view of the photo sensor, FIG. 2 is a sectional view taken along the line II--II of FIG. 1, and FIG.
FIG. 4 is a diagram showing the relationship between the distance from the pixel center of the photo sensor and the reflected light intensity.

The photosensor 10 is formed as a photosensor array in which a plurality of sensor parts 11 as shown in FIGS. 1 and 2 are formed in a line shape in the left-right direction in FIGS. 1 and 2, and each sensor part 11 is formed. As shown in FIGS. 1 and 2, a rectangular light shielding layer 13 is formed on a transparent insulating substrate 12 made of glass or the like, and the light shielding layer 13 has a light shielding property such as Cr. It is formed of a metal film, a silicon vapor deposition film, or the like. A rectangular first light guide window 14 is formed substantially at the center of the light shielding layer 13.

A transparent insulating film 15 is formed so as to cover the light shielding layer 13 and the insulating substrate 12, and a silicon thin film layer 16 is formed on the light shielding layer 13 with the transparent insulating film 15 interposed therebetween. The silicon thin film layer 16 is preferably i
Type amorphous silicon (ia-Si), and has a central channel region 16a and source / drain regions 16b formed on both sides with the channel region 16a sandwiched therebetween. In the channel region 16a, a rectangular second light guide window 17 having a shape similar to the first light guide window 14 and slightly larger than the first light guide window 14 is formed.

A source electrode 18 and a drain electrode 19 are formed on the source / drain regions 16b of the silicon thin film layer 16.
Are formed so as to face each other, and the silicon thin film layer 1
6 and the source electrode 18 and the drain electrode 19 are directly
Alternatively, they are connected through an n + silicon layer (not shown) made of amorphous silicon in which a dopant such as phosphorus is diffused.

These silicon thin film layer 16 and source electrode 1
8, a protective film 20 is formed so as to cover the drain electrode 19 and the transparent insulating film 15, and the protective film 20 is made of a material having a light transmitting property and an insulating property, for example, silicon nitride (Si
N).

A gate electrode 21 is formed in the protective film 20 and above the silicon thin film layer 16, and the gate electrode 21 is an end of the source electrode 18 and the drain electrode 19 on opposite sides. It is formed in a size that covers the part as well. The gate electrode 21 is a transparent conductive film (ITO)
It is formed of and transmits light.

Each sensor section 11 of this photo sensor 10
As described above, the source electrode 18 and the drain electrode 19 are formed in the source / drain regions 16b of the silicon thin film layer 16.
Are connected to each other, and the gate electrode 21 is formed at a position facing the channel region 16a of the silicon thin film layer 16 via the protective film 20 which is an insulator, and functions as a MOS transistor.

The first light guide window 14 and the second light guide window 17 are, as shown in FIG. 1, in the channel length direction of the channel region 16a forming the MOS transistor, that is, the source electrode 18-drain electrode. It is formed in a rectangular shape that is long in 19 directions and short in its width direction.

The manufacturing method of the photosensor 10 is not particularly limited, and it can be formed by a usual film forming technique such as a vacuum vapor deposition method, a sputtering method or a plasma CVD method.

This photosensor 10 is, as described above,
Since the light shielding layer 13 is formed in each sensor portion 11, the light emitted from the light source to each sensor portion 11 is shielded by the light shielding layer 13, but the first light guide window 14 is formed in the light shielding layer 13.
And the first light guide window 1 is formed in the channel region 16a of the silicon thin film layer 16 formed on the light shielding layer 13.
Since the second light guide window 17 is formed at a position opposed to 4, the original 30 is transmitted through the first light guide window 14 and the second light guide window 17. Further, in the present embodiment, since the light shielding layer 13 is not formed between each sensor portion 11 and the sensor portion 11, the light from the light source passes through this portion and is applied to the original document 30. .

The light applied to the original 30 in this manner is diffusely reflected by the original 30, but the reflected light reflected in the direction shown by the arrow in FIG. 3 is the channel of the silicon thin film layer 16 of each sensor section 11. It is incident on the region 16a. Then, of the reflected light incident on the channel region 16a, the first
As for the reflected light of the light transmitted through the light guide window 14 and the second light guide window 17, the second light guide window 17 is formed in the substantially central portion of the channel region 16a, and therefore, as shown in FIG. The angle of reflection on the surface is small, and the optical path length can be made shorter than that of a conventional photosensor having a light guide window adjacent to a pixel. As a result, the light intensity of the reflected light input to the channel region 16a of the silicon thin film layer 16 is the same as that of the first light guide window 14
Also, it becomes large at the portion that has passed through the second light guide window 17, and the light receiving efficiency can be improved.

[0026]

According to the photosensor of the present invention, the irradiation light passes through the first light guide window formed in the light shielding layer and the second light guide window formed in the channel region of the silicon thin film layer. The reflected light reflected on the substrate side is applied to the channel region of the silicon thin film.

That is, since the center of the reflected light coincides with the center of the channel region which is the photoelectric conversion portion of the photo sensor, the optical path length of the reflected light irradiated on the channel region of the silicon thin film is greatly increased. The length can be shortened, and the light intensity of the reflected light reflected by the channel region can be increased. As a result, the sensitivity of the photo sensor can be improved. In this case, the second formed in the channel region
Since the light guide window is formed long in the channel length direction and short in the channel width direction, it is possible to suppress a decrease in photocurrent due to the formation of the second light guide window.

Further, since the periphery of each of the first light guide window and the second light guide window is shielded by the light shielding layer, the adjacent second
Even if the reflected light of the light incident from the light guide window is incident on the channel region, the optical path length of the reflected light is equal to that of the reflected light of the light incident through the second light guide window formed in the channel region. The reflected light of the light, which is much longer than the optical path length and is incident from the adjacent second light guide window, is attenuated more than the reflected light of the light incident through the second light guide window formed in the channel region. As a result, it is possible to reliably separate the reflected light of the light incident through the second light guide window formed in each channel region and the reflected light of the light incident through the adjacent second light guide window, The resolution of each pixel of the photo sensor can be improved.

[Brief description of drawings]

FIG. 1 is a top view of an embodiment of a photo sensor according to the present invention.

FIG. 2 is a sectional view taken along the line II-II of FIG.

FIG. 3 is an operation explanatory diagram of the photosensor of the present invention.

FIG. 4 is a side sectional view of a conventional photo sensor.

[Explanation of symbols]

 10 Photosensor 11 Sensor part 12 Insulating substrate 13 Light-shielding layer 14 First light guide window 15 Transparent insulating film 16 Silicon thin film layer 16a Channel region 16b Source / drain region 17 Second light guide window 18 Source electrode 19 Drain electrode 20 Protective film 21 Gate electrode

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical indication location H01L 23/31 29/40 A 7376-4M 29/784 31/10 H04N 1/028 Z 8721-5C 9056-4M H01L 29/78 311 J 8422-4M 31/10 A

Claims (1)

[Claims] 1. A light-transmissive substrate, a light-shielding layer formed on the substrate to shield irradiation light, and a first light guide window formed in the light-shielding layer and transmitting irradiation light from the substrate side. A silicon thin film layer formed on the light shielding layer, the silicon thin film layer having a channel region and a source region and a drain region facing each other with the channel region interposed therebetween, and the silicon thin film layer facing the first light guide window in the channel region of the silicon thin film layer. A second light guide window that is formed at a position facing the first light guide window and transmits the irradiation light that has passed through the first light guide window; and a transparent gate electrode formed on the silicon thin film layer. The light emitted from the substrate side passes through the first light guide window and the second light guide window and is emitted to the detection target located on the transparent gate electrode side,
A photosensor for receiving reflected light from the detection target in a channel region of the silicon thin film, wherein the first light guide window and the second light guide window are long in a length direction of the channel region, and A photo sensor characterized by being formed in a short shape in the width direction of a channel region.