JPH05218483A - Photoelectric conversion device - Google Patents

Abstract

PURPOSE:To provide a photoelectric conversion device which is very excellent in reliability keeping high in dielectric breakdown strength without deteriorating in characteristics. CONSTITUTION:A first transparent electrode layer 2, a light shading layer 3, a second transparent electrode layer 4, and back electrode layers 6a and 6b are successively laminated on the rear of an insulating base 1 which transmits incident light, and a non-light receiving part is provided onto a semiconductor layer 5 with the light shading layer 3. A layer of two-layered structure composed of a light attenuating layer of semiconductor smaller than the semiconductor layer 5 in forbidden band width and a metal layer may be made to serve as a light shading layer, or the light attenuating layer may be set larger than the semiconductor layer 5 in defect density.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric conversion device such as a light receiving element, and more particularly to a photoelectric conversion device having a light shielding structure for improving electrostatic withstand voltage.

[0002]

2. Description of the Related Art Conventionally, a photoelectric conversion device having a diode structure generally has a structure in which a transparent electrode layer, a semiconductor layer, a back electrode layer, and a resin protective layer are sequentially laminated on a translucent glass substrate. .. Then, the incident light transmitted through the glass substrate causes the semiconductor layer sandwiched between the transparent electrode layer and the back electrode layer to generate power. This semiconductor layer also acts as a capacitor having a certain junction capacitance.

By the way, when static electricity is applied to the output terminal of the photoelectric conversion device, a voltage inversely proportional to the inter-terminal capacitance of the device is applied to the output terminal. However, if the photoelectric conversion device is a camera photodiode, for example, it is effective. Since the power generation area is very small and the inter-terminal capacitance is proportional to the area of the power generation area, the electrostatic withstand voltage is extremely low and it may be easily destroyed by static electricity in the measurement process and mounting process. It was a problem.

Therefore, a non-light-receiving portion is formed by covering a part of the semiconductor layer serving as a power generation region with a light-shielding layer, and the inter-terminal capacitance is determined by the junction capacitance formed in this non-light-receiving portion and the junction capacitance of the light-receiving portion. A technology has been proposed that improves electrostatic withstand voltage by configuring a large inter-terminal capacitance with respect to a very small area of the light receiving portion that is an effective power generation area (Actual Kaihei 1-139459).
No.

[0005]

However, in the above-mentioned conventional photoelectric conversion device, a metal layer having a high reflectance is used as a light-shielding layer, and a semiconductor layer for photovoltaic power generation is located on the metal layer. In such a photoelectric conversion device, since the semiconductor layer is directly laminated after the formation of the metal layer, the constituent elements of the metal layer are diffused in the semiconductor layer, and the defect level due to impurities is generated in the forbidden band width of the semiconductor layer. Generated, the photoexcited electrons and holes are trapped in this step, or the electrons and holes excited through this step recombine and disappear, leading to a decrease in power generation efficiency, As a result, there arises a problem that the characteristics of the photoelectric conversion device are deteriorated.

If the light-shielding layer is only a metal layer, multiple reflection occurs in the layer on the substrate side through which the light reflected by the light-reflecting surface of the light-shielding layer passes, and part of the reflected light is the light-receiving surface of the substrate. The ambient light adversely affects the linearity of the bright current with respect to the amount of light received by the photoelectric conversion device, and deteriorates the characteristics of the photoelectric conversion device even if the electrostatic withstand voltage can be improved. It is a problem.

Further, when a metal layer is formed on a substrate, the adhesion between the substrate and the metal layer may be a problem due to the difference in the coefficient of thermal expansion between the substrate and the metal layer. There is a problem that the photoelectric conversion device lacks reliability.

[0008]

[Object] Accordingly, the present invention provides a photoelectric conversion device having a light-shielding layer, which solves the above-mentioned problems of the related art and has an extremely high reliability that does not cause characteristic deterioration while maintaining the original electrostatic breakdown voltage. The purpose is to

[0009]

In order to achieve the above object, the photoelectric conversion device of the present invention comprises a first transparent electrode layer, a light shielding layer and a second transparent electrode layer on the back surface of an insulating substrate through which incident light is transmitted. The semiconductor layer and the back electrode layer are sequentially laminated, and the non-light-receiving portion is formed in the semiconductor layer by the light shielding layer.

The light-shielding layer may have a two-layer structure of a light attenuating layer made of a semiconductor having a forbidden body width smaller than that of the semiconductor layer and a metal layer, and the light attenuating layer has a higher defect density than the semiconductor layer. It may be configured.

[0011]

Embodiments of the present invention will be described in detail with reference to the drawings. <First Embodiment> First, the photoelectric conversion device S1 shown in FIG.
For example, it is a photodiode for a camera, in which a first transparent electrode layer 2 is laminated on a translucent insulating substrate 1 which receives the external light L, and is further patterned on the first transparent electrode layer 2 into a predetermined shape. The light shielding layer 3 and the second transparent electrode layer 4 are laminated. Here, the second transparent electrode layer 4 is connected to the first transparent electrode layer 2 and is formed so as to sandwich the light shielding layer 3 between the first transparent electrode layers 2. Further, a semiconductor layer 5 patterned into a predetermined shape is laminated on the second transparent electrode layer 4, and back electrode layers 6a and 6b are further laminated on the semiconductor layer 5 to form a second transparent electrode layer 4 on the second transparent electrode layer 4. Is connected to the back electrode layer 6a. The photoelectric conversion device S1 thus configured can accurately sense the amount of received light by detecting the power generated in the semiconductor layer 5.

Next, each layer of the photoelectric conversion device S1 will be described. As the insulating substrate 1, a transparent insulator such as a well-cleaned well-known glass substrate having a thickness of about 0.4 to 1.1 mm is used. For example, when the glass substrate contains a large amount of impurities such as alkali metal, It is preferable that an insulating film such as silicon oxide is deposited on the laminated surface side to prevent impurities from diffusing into the layer laminated on the insulating substrate 1.

The first transparent electrode layer 2 is provided to improve at least the adhesion to the light shielding layer 3 and the second transparent electrode layer described later. In this embodiment, the insulating substrate 1 is used.
It is heated to about 500 ℃ and tin oxide or ITO is applied on top of it.
A material mainly composed of (indium tin oxide) or the like is deposited to a thickness of about 600 to 4500Å by a well-known film forming method such as a CVD method, a sputtering method, an electron beam evaporation method, or a spray method.

The light-shielding layer 3 is made of, for example, a single metal such as aluminum, nickel, chromium, titanium, gold or silver, or an alloy of a combination thereof, which is formed by a vacuum deposition method or the like.
The transparent electrode layer 2 is deposited to a thickness of at least 3000 Å or more to prevent unnecessary expansion of the light receiving area.

The second transparent electrode layer 4 is formed with the same material and method as the first transparent electrode layer 2 to have a thickness of about several hundred Å. The material is the same as that of the light shielding layer 3 and the semiconductor layer 5. It is necessary that they are compatible with each other, that is, it is necessary to maintain the adhesive strength with both of these layers and make ohmic contact, and the material is not necessarily the same as that of the first transparent electrode layer 2. A two-layer structure of a fluorine-doped layer that improves the film quality and a non-doped layer that prevents the diffusion of fluorine into the semiconductor layer 5 so as not to impair the characteristics of the semiconductor layer 5 is obtained. You may form so that it may be formed.

The semiconductor layer 5 is formed on the second transparent electrode layer 4 by p-.
It is composed of hydrogenated amorphous silicon (hereinafter abbreviated as a-Si: H) having a three-layer structure of in, and each of these layers is formed by a well-known vapor phase growth method. Is formed. That is, the p layer is deposited on the second transparent electrode layer 4, and
i: H-forming gas such as silane is mixed with impurity doping gas such as diborane at a predetermined ratio to have a thickness of about
Form around 200Å. The i layer is formed only on the a-Si: H forming gas to a thickness of about 7,000 Å on the p layer, and the n layer is formed on the i layer by phosphine, which is a gas for doping the a-Si: H forming gas with impurities. Are mixed at a predetermined ratio to form a thickness of about 500Å.

The back electrode layers 6a and 6b are respectively the light shielding layer 3
The same material and method as described above are deposited on the semiconductor layer 5 to a thickness of about 2500 Å. Here, the back surface electrode layer 6a serving as an anode
Are also in contact with the second transparent electrode layer 4. The back electrode layers 6a and 6b are not necessarily made of the same material as the light shielding layer 3. The semiconductor layer 5 between these electrodes has an n layer etched.

Since the photoelectric conversion device S1 has a structure in which the light-shielding layer 3 is sandwiched between the first transparent electrode layer 2 and the second transparent electrode layer 4, a defect is caused by the metal element diffusing and penetrating into the semiconductor layer 5. It is possible to prevent as much as possible the problem that the tilting occurs, the power generation efficiency is significantly reduced, and the characteristics are deteriorated.
Moreover, since the first transparent electrode layer 2 is well compatible with the insulating substrate 1 and the light shielding layer 3, the light shielding layer 3 is not separated from the insulating substrate 1 as in the conventional case, and a highly reliable one can be provided. ..

<Second Embodiment> Next, as shown in FIG.
The photoelectric conversion device S2 of the second embodiment is one in which the light attenuation layer 7 is provided between the first transparent electrode layer 2 and the light shielding layer 3 of the photoelectric conversion device S1 of the first embodiment. A-S as 7
By using the i: H layer or the crystalline c-Si layer, the reflected light of the light-shielding layer 3 is attenuated by this layer to prevent the occurrence of ambient light on the light-receiving surface, and the photoelectric conversion device S2
The linearity of the bright current value can be maintained. The degree of attenuation is 1 × 10 ⁻⁵ cm ⁻¹ or more in light absorption coefficient, and the film thickness may be several hundred Å or more. Further, the film formation of the light attenuation layer 7 is similar to the formation of the i layer of the semiconductor layer 5,
This is achieved by laser annealing or epitaxial growth to obtain a complete crystal layer. In addition, the bandgap of this layer must be at least equal to or less than the bandgap of the semiconductor layer 5 in order to absorb and consume light of the sensitivity wavelength of the semiconductor layer 5 which is the power generation part. Layer 5
There is a method of using a-Si: Ge: H other than the crystallization of. Alternatively, non-hydrogenated amorphous silicon (a-Si) having a high localized density of defects (defect density) may be used.
Further, this material is not limited to the silicon type, and various semiconductors can be used.

<Third Embodiment> Next, a third embodiment of the present invention will be described. Photoelectric conversion device S3 of the third embodiment
Is at least the semiconductor layer of the light attenuation layer 7 of FIG.
Layer 8 with a higher defect density (for example, 2 to 3 digits)
By doing so, the photovoltaic layer 3 and the light attenuating layer 8 prevent the photovoltaic power generation due to the Schottky diode structure, and the light attenuating layer 8
The carriers generated in (1) are trapped in the structural defects and are eliminated by using them as recombination centers to suppress the photocurrent, so that it is possible to provide a more reliable photoelectric conversion device than the second embodiment.

A specific example of the light attenuation layer 8 is aS
i: H highly doped layer, that is, an impurity concentration of 1 × 10 ⁴
The density of defects is increased by about 2 to 3 orders of magnitude (1 × 10 ¹⁴ to 10 ¹⁶ cm ⁻³ ) from that of a-Si: H, for example, by setting it to about ppm or more or by forming an a-Si layer. make it happen.

In the above-mentioned embodiments, the example of the photodiode for the camera is shown, but it can be applied to various photoelectric conversion devices having a diode structure such as a color sensor. Also, regarding the semiconductor layer, the above-mentioned embodiment is only an example, and a well-known structure can be adopted.

[0023]

As described above, according to the photoelectric conversion device of the present invention, since the light-shielding layer is sandwiched between the second transparent electrode layer and the transparent electrode layer, the light-receiving surface serving as an effective power generation region is small. However, it is possible to maintain the original power generation characteristics and prevent deterioration of element characteristics.

Further, by providing the layer for attenuating the reflection of the light shielding layer, the linear characteristic of the bright current value with respect to the illuminance of the photoelectric conversion device can be maintained.

Furthermore, by making the attenuation layer a layer having a high defect density, the photocurrent in the light-shielding layer can be extinguished, and a more reliable photoelectric conversion device can be provided.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of essential parts showing a first embodiment of a photoelectric conversion device according to the present invention.

FIG. 2 is a cross-sectional view of essential parts showing second and third embodiments of the photoelectric conversion device according to the present invention.

[Explanation of symbols]

1 ... Insulating substrate 2 ... First transparent electrode layer 3 ... Light-shielding layer 4 ... Second transparent electrode layer 5 ... Semiconductor layer 6 ... Back electrode layer 7, 8 ... Light Attenuation layer S1, S2, S3 ... Photoelectric conversion device

Claims (3)

[Claims] 1. A first transparent electrode layer, a light shielding layer, a second transparent electrode layer, a semiconductor layer and a back surface electrode layer are sequentially laminated on the back surface of an insulating substrate through which incident light is transmitted, and the semiconductor layer is formed by the light shielding layer. A photoelectric conversion device, characterized in that a non-light-receiving portion is formed on the. 2. The light-shielding layer has a two-layer structure including a light-attenuating layer made of a semiconductor having a band gap smaller than that of the semiconductor layer and a metal layer laminated on the light-attenuating layer. The photoelectric conversion device described in 1. 3. The photoelectric conversion device according to claim 2, wherein the light attenuation layer has a defect density higher than that of the semiconductor layer.