JPH05343656A - Image sensor - Google Patents

Abstract

PURPOSE:To eliminate adverse influence to a video signal due to unnecessary incident light ray such as an infrared ray, etc., without reducing sensitivity. CONSTITUTION:An image sensor has a pixel unit 9, and an optical black part 10, and comprises a filter layer 12 for cutting off light of wavelength near an infrared region on the part 10. The unit 9 is formed of a photodiode having a p<+> type semiconductor layer 4 and an n<-> type semiconductor layer 6, has a photoelectric converter 100 for converting incident light into an electric signal, an n-type semiconductor layer 5 covering with a shield layer 8a and a polysilicon layer 7, and a charge transfer unit 200 for transferring charge of the converter 100. The part 10 has the converter 100 formed of the photodiode, and the unit 200. The converter 100 and the unit 200 are covered with the layer 8a and the layer 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup device.

[0002]

2. Description of the Related Art In recent years, solid-state image pickup devices, which are widely used in image pickup devices, have been rapidly improved in performance, and the image pickup tubes that have been conventionally used in home movies and surveillance cameras, which are required to be downsized. Is used in place of completely. The solid-state image pickup device converts image information, which is incident on the solid-state image pickup device as a light beam, into an electric signal by using a photodiode called a pixel. By arranging these pixels horizontally and vertically, a video signal is captured. In order to improve the image quality of an image, it is necessary to increase the number of pixels.

When the amount of incident light is constant, the larger the photodiode, the higher the sensitivity, but it cannot be increased so much because of the need for high image quality and miniaturization. Therefore, by increasing the aperture ratio of the pixel by miniaturization technology, optimizing the amplifier structure, and providing a condenser lens on the color filter that hinders the high sensitivity, high sensitivity is achieved. There is.

Among the solid-state image pickup devices, the charge-coupled device (hereinafter referred to as "CCD") has been remarkably advanced in miniaturization of the device itself, high density of pixels and high sensitivity. Among them, the CCD mounted on the surveillance camera is required to have a particularly high sensitivity. Therefore, when colorization is not required, a color filter or an optical filter for shielding infrared rays, which tends to hinder the high sensitivity, is generally used. In many cases, it is not attached.

A conventional image pickup apparatus will be described below with reference to the drawings. Conventionally, an image pickup device includes a pixel unit and an optical black unit. FIG. 3 is a cross-sectional view of essential parts showing the configuration of the pixel portion of the image pickup device. In FIG. 3, 1 is an n-type semiconductor substrate, 2 is a p ⁻ -type semiconductor layer, 3 is a p-type semiconductor layer, 4 is a p ⁺ -type semiconductor layer, 5 is an n-type semiconductor layer, and 6 is n ^−. A semiconductor layer, a polysilicon layer 7 and a light-shielding layer 8 made of aluminum.

As shown in FIG. 3, the pixel section 9 includes a photoelectric conversion section 100 composed of a photodiode of a p ⁺ type semiconductor layer 4 and an n ⁻ type semiconductor layer 6 on a semiconductor substrate 1, and an n ^- type photoelectric conversion section.
And a charge transfer section 200 formed of a polysilicon layer 7 of the mold, and the charge transfer section 200 is covered with a light shielding layer 8. The light beam incident on the photoelectric conversion unit 100 is converted into an electric signal and transferred by the charge transfer unit 200. By covering the charge transfer unit 200 with the light-shielding layer 8, it is possible to prevent light rays from entering the charge transfer unit 200, and the photoelectric conversion unit 100 is prevented.
The light rays are made incident on only.

FIG. 4 is a cross-sectional view of the main parts showing the structure of the optical black portion of the conventional image pickup apparatus. In FIG. 4, 8a is a light-shielding layer made of aluminum.
The parts having the same reference numerals as those in FIG. As shown in FIG. 4, the optical black portion 40 includes a photoelectric conversion portion 100 including a photodiode of a p ⁺ type semiconductor layer 4 and an n ⁻ type semiconductor layer 6 and an n type semiconductor layer on the semiconductor substrate 1. 5 and charge transfer section 2 composed of polysilicon layer 7
00, and the photoelectric conversion unit 100 and the charge transfer unit 20.
By covering 0 with a light-shielding layer 8a, light rays are prevented from entering. This optical black part 40
Is for measuring the dark output level, and the black level, luminance signal and color difference signal of the video signal are processed by the video signal processing circuit (not shown) with this output level as a reference.

A video signal output from an image pickup device having the pixel portion 9 and the optical black portion 40 having the above-described structure is processed by a video signal processing circuit (not shown).
It is expressed and processed by two types of signals, a luminance signal and a color difference signal. The luminance signal indicates the intensity of the light ray incident on the image pickup element, and the color difference signal indicates the wavelength and color density of visible light rays such as red and blue. The output level of the optical black section 40 shown in FIG. 4 is used as the reference level of the luminance signal and the color difference signal for processing.

[0009]

However, in the conventional image pickup device, the light shielding layers 8 and 8a made of aluminum, which have a role of not transmitting light rays, are about 800.
It has a drawback that it slightly transmits light having a wavelength near infrared rays of [nm] or more. When a light ray having a wavelength near infrared rays passes through the light-shielding layer and is incident on a portion other than the photoelectric conversion portion 100 of the optical black portion 40 or the photoelectric conversion portion 100 of the pixel portion 9,
Unwanted charges are accumulated. The unnecessary charges adversely affect the normal video signal as noise. In particular, the unnecessary charges generated in the optical black portion 40 change the reference level of the above-described luminance signal and color difference signal as dark output noise, or cause dark current variations to generate fixed pattern noise on the imaging screen. There is a problem.

In the conventional image pickup apparatus, an optical filter (not shown) which does not transmit infrared rays is mounted on the entire surface of the solid-state image pickup element in order to prevent the above infrared rays from entering. However, when an optical filter is attached, visible light is blocked in addition to infrared light.
Since the optical filter in the conventional image pickup device covers not only the optical black portion 40 but also the pixel portion 9, the amount of light incident on the pixel portion 9 is reduced by the optical filter, which leads to a reduction in the sensitivity of the image pickup device. There was a problem. An optical filter that causes such a decrease in sensitivity is not suitable for application to a surveillance camera that requires particularly high sensitivity.

An object of the present invention is to solve the above-mentioned conventional problems, and to provide an image pickup apparatus which does not adversely affect the video signal due to the incidence of unnecessary light rays such as infrared rays without lowering the sensitivity. is there.

[0012]

The image pickup apparatus of the present invention comprises:
The photoelectric conversion part of the optical black part is covered with a filter layer that blocks light rays of a specific wavelength.

[0013]

According to the structure of the present invention, by covering the photoelectric conversion portion of the optical black portion with the filter layer for blocking the light rays of the specific wavelength, unnecessary light rays such as infrared rays are incident on the photoelectric conversion portion of the optical black portion. By preventing this, it is possible to eliminate the generation of unnecessary charges in the optical black portion.

Further, by providing the filter layer only on the optical black portion, the amount of light incident on the photoelectric conversion portion of the pixel portion does not decrease, and therefore the sensitivity does not decrease.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view showing the arrangement of an image pickup apparatus according to an embodiment of the present invention. 1 (a) is an external perspective view showing the configuration of an image pickup apparatus according to an embodiment of the present invention,
FIG. 1B is a cross-sectional view taken along the line AB of the image pickup apparatus in FIG.
FIG. 3C is a partial cross-sectional view showing the configuration of the optical black portion of the imaging device.

In FIG. 1, 1 is an n-type semiconductor substrate, 2
Is ap ⁻ type semiconductor layer, 3 is ap type semiconductor layer, 4 is ap ⁺ type semiconductor layer, 5 is an n type semiconductor layer, 6 is an n ⁻ type semiconductor layer, 7 is a polysilicon layer, and 8a is A light shielding layer made of aluminum, 9 is a pixel portion, 10 is an optical black portion,
12 is a filter layer, 100 is a photoelectric conversion unit, and 200 is a charge transfer unit.

As shown in FIGS. 1A and 1B, the image pickup device has a pixel portion 9 and an optical black portion 10, and a filter layer 12 is provided on the optical black portion 10. It is a thing. The pixel portion 9 is similar to that shown in FIG. 3, and the p ⁺ type semiconductor layer 4 and n ^{− are formed.}
A photoelectric conversion part 100 which is made up of a photodiode of a semiconductor layer 6 of the n-type and which converts an incident light beam into an electric signal, and an electric charge which is made up of an n-type semiconductor layer 5 and a polysilicon layer 7 and which transfers charges of the photoelectric conversion part 100. The transfer unit 200 is included. The charge transfer section 200 of the pixel section 9 is covered with the light shielding layer 8.

The optical black portion 10 is shown in FIG.
As shown in, the photoelectric conversion unit 1 including a photodiode
00 and the charge transfer unit 200. The photoelectric conversion unit 100 and the charge transfer unit 200 are provided with the shielding layer 8
It is covered with a and the filter layer 12. As shown in FIG. 2, the filter layer 12 has a property of hardly transmitting a light ray in the infrared region of about 800 nm or more. In addition, in FIG. 2, the horizontal axis represents each wavelength [nm] of the light beam incident on the filter layer 12, and the vertical axis transmits the filter layer 12 when the amount of the light beam incident on the filter layer 12 is 100%. Transmitting light ray [%]
Indicates.

In the image pickup device having such a configuration, the photoelectric conversion portion 10 of the optical black portion 10 is provided by providing the filter layer 12 having a characteristic of hardly transmitting light rays in the infrared region in the optical black portion 10.
By preventing infrared rays from entering 0, generation of unnecessary charges in the optical black portion 10 can be eliminated.

Since the filter layer 12 is provided only in the optical black portion 10, the photoelectric conversion portion 1 of the pixel portion 9 is provided.
The amount of light incident on 00 does not decrease, and thus the sensitivity does not decrease. Therefore, it is possible to obtain an image pickup apparatus without adversely affecting the video signal due to the incidence of infrared rays, that is, noise generation of the video signal, fluctuation of the reference level, etc.

Although the filter layer 12 of this embodiment has a characteristic that it hardly transmits light rays in the infrared region of about 800 nm or more, it does not transmit the luminance signal and the color difference signal of the video signal processing device. The type of wavelength of the light beam that is not transmitted is arbitrary as long as it does not adversely affect the image signal with respect to the reference level and the image information to be imaged. The type of the filter layer 12 is not particularly limited, and may be an interference filter or a metal layer.

Further, although the filter layer 12 of this embodiment is formed on the light shielding layer 8a via a protective layer, it is provided at a position where the light rays can be prevented from entering the photoelectric conversion portion 100 of the optical black portion 10. If it exists, it may be formed at any position and the same effect can be obtained. The image pickup device provided with the filter layer 12 is not particularly limited, and the filter layer is provided in the optical black portion of any image pickup device regardless of the type of the image pickup device due to the difference in use such as color and black and white and the characteristics. It doesn't matter.

[0023]

According to the image pickup device of the present invention, by covering the photoelectric conversion portion of the optical black portion with the filter layer that shields the light of a specific wavelength, infrared rays or the like to the photoelectric conversion portion of the optical black portion can be eliminated. By preventing the incidence of light rays, it is possible to eliminate the generation of unnecessary charges in the optical black portion.

Further, by providing the filter layer only on the optical black portion, the amount of light incident on the photoelectric conversion portion of the pixel portion does not decrease, and therefore the sensitivity does not decrease. As a result, it is possible to obtain an imaging device in which the adverse effect on the video signal due to the incidence of unnecessary light rays such as infrared rays is eliminated without lowering the sensitivity.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of an image pickup apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a light ray of each wavelength and a transmittance of the light ray to the filter layer 12.

FIG. 3 is a main-portion cross-sectional view showing the structure of a pixel portion of an imaging device.

FIG. 4 is a main-portion cross-sectional view showing a configuration of an optical black portion of a conventional imaging device.

[Explanation of symbols]

 100 Photoelectric conversion part 8 Light-shielding layer 8a Light-shielding layer 200 Charge transfer part 9 Pixel part 10 Optical black part 12 Filter layer

Claims (1)

[Claims] 1. A pixel portion in which a charge transfer portion is covered with a light shielding layer,
An image pickup device comprising: an optical black part in which a photoelectric conversion part and a charge transfer part are covered with a light-shielding layer, wherein the photoelectric conversion part of the optical black part is covered with a filter layer for shielding light rays of a specific wavelength. Image pickup device.