JPH0530434A - Solid-state image pickup device - Google Patents

Abstract

PURPOSE:To enable the device to cope with a change in the brightness momentarily without need of a new process in the solid-state image pickup element employing a laminated solid-state image pickup element. CONSTITUTION:A solid-state image pickup element made of an inter-line transfer CCD is formed on a P-channel semiconductor substrate 1, a photoelectric conversion film 11 is laminated onto a picture element electrode 10 connected to a metallic electrode 8 formed to each picture element and a transparent electrode 12 to apply an electric field is provided onto the photoelectric conversion film 11. Then an exposure detection means 13 comprising a current-voltage converter is connected to the transparent electrode 12 and a current supplied from the transparent electrode 12 is detected as exposure information.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state image pickup device including a stack type solid-state image pickup device having an exposure detection means.

[0002]

2. Description of the Related Art Conventionally, solid-state image pickup devices have been used in various fields such as movies, electronic cameras, and AF sensors. Accordingly, it is necessary to control the aperture and shutter speed (light integration time). Therefore, in the solid-state imaging device used for movies and the like, a method of feeding back the output of the previous frame to control exposure is used.

However, in the method of controlling the exposure by feeding back the output of the previous frame, the flicker is poor when the rapid lightness change has a poor followability or the light source is AC-changing. There was a problem such as occurrence of. Further, the method in which the exposure amount is once stored and imaged cannot cope with a sudden change in brightness, stroboscopic photography, or the like.

For this reason, in the interline CCD image pickup device, there has been proposed a method of providing a photometric photodiode on the transfer path (Japanese Patent Laid-Open No. 62-251395), which is an interline CCD. It has a problem that it can be applied only to an image pickup device and that the number of steps is newly added in the process.

In order to solve these problems, the applicant of the present application has found that carriers having opposite polarities generated by incident light at the same time as carriers accumulated as signal charges in the photodiode section of the image pickup device, for example, of the image pickup device. A method of detecting the current by connecting a current detection circuit to an electrode or the like provided on the back surface and using this information as real-time exposure control information is disclosed in JP-A-3-
Proposed in No. 36592.

[0006]

By the way, as one of the methods for increasing the sensitivity of an image pickup device, a so-called laminated solid-state image pickup device in which a photoelectric conversion layer is laminated on the image pickup device has been conventionally proposed. In such a type of solid-state imaging device, since carriers that become signals are generated by incident light in a laminated film that is a photoelectric conversion layer, as in the method previously proposed by the applicant of the present application, the imaging device substrate There is a problem in that it is impossible to detect a carrier having a polarity opposite to that of the signal carrier from the electrode provided in the above, and the above method cannot be applied as it is.

The present invention has been made in order to solve the above-mentioned problems in the solid-state image pickup device using the conventional laminated type image pickup device, does not require a new process step, and is capable of responding to a change in brightness. It is an object of the present invention to provide a solid-state image pickup device using a stacked type image pickup device provided with an exposure detection means capable of responding instantly.

[0008]

In order to solve the above problems, the present invention provides a photoelectric conversion in which an upper surface is connected to a light-transmissive electrode and a lower surface is connected to a pixel electrode provided for each pixel. In a solid-state imaging device using a laminated solid-state imaging device having a film having a function, carriers collected for each pixel as image information among electron-hole pairs generated by light incident on the photoelectric conversion film. And an exposure detection unit that detects a carrier having a polarity opposite to that of the carrier through an electrode provided on the upper surface to obtain exposure information.

In the solid-state imaging device having such a structure, when light enters the photoelectric conversion film, electron-hole pairs are generated, one carrier is collected for each pixel through the pixel electrode, and the other carrier is collected. Flows out through a light-transmissive electrode provided on the upper surface opposite to the pixel electrode, and the current resulting therefrom is detected by the exposure detection means. This current is proportional to the number of electron-hole pairs generated by the incidence of light in the photoelectric conversion film, so that exposure information corresponding to the amount of incident light can be obtained instantaneously.

[0010]

EXAMPLES Next, examples will be described. FIG. 1 is a cross-sectional view and a circuit configuration diagram showing an embodiment of a solid-state imaging device according to the present invention. In the figure, reference numeral 1 is a p-type semiconductor substrate, and on the surface of the substrate 1, an n-type diffusion layer 2 for forming an n ⁺ diode which becomes a pixel signal charge storage portion of an image pickup device is formed.
An n-type diffusion layer 3 for forming a signal charge transfer portion, and a p-type diffusion layer 4 for electrically isolating each pixel from each other. A transfer electrode 6 for transferring is provided, and an insulating layer 7 is provided on the transfer electrode 6. On the other hand, a metal electrode 8 is electrically connected to the n-type diffusion layer 2 for each pixel, and an insulating layer 9 for flattening the surface is formed on the metal electrode 8. The pixel electrode 10 is formed on the upper surface of the layer 9 so as to partially contact the metal electrode 8.
Further, on the pixel electrode 10, a film 11 having a photoelectric conversion function such as amorphous silicon is laminated,
A transparent electrode 12 for applying an electric field to the photoelectric conversion film 11 is provided on the uppermost surface. And on this transparent electrode 12,
Applying a negative bias V _R, the exposure detecting unit 13, exposure information by detecting a current flowing out from the transparent electrode 12 is connected. Note that this exposure detection means 13 includes an operational amplifier 21,
The current-voltage converter is composed of a negative power source 22 and a feedback resistor 23.

Next, the light integration operation in the solid-state image pickup device having the above-mentioned structure will be described. The n-type diffusion layer 2 for forming the n ⁺ diode which becomes the signal charge storage portion is
A positive potential is applied to the transfer electrode 6, and the channel between the n-type diffusion layer 2 and the n-type diffusion layer 3 for forming the signal charge transfer portion is turned on to be reset. At this time, the n-type diffusion layer 2 is reset to a positive potential as compared with the p-type semiconductor substrate 1, and the signal charge storage diode constituted by the n-type diffusion layer 2 and the p-type semiconductor substrate 1 is in a reverse bias state. Next, when the positive potential applied to the transfer electrode 6 is released, optical integration is started.

As shown in FIG.
When is incident, electron-hole pairs are generated in the photoelectric conversion film 11. At this time, the electrons travel according to the electric field in the photoelectric conversion film 11, reach the n-type diffusion layer 2 via the pixel electrode 10 and the metal electrode 8, and are accumulated. On the other hand, the holes travel along the electric field in the photoelectric conversion film 11 like the electrons, and the uppermost transparent electrode.
Reach twelve. Therefore, the transparent electrode 12 to the exposure detection means 13
A current I _P is generated toward. This current _IP is proportional to the electron-hole pair generated by the incidence of light. Therefore, by detecting this current I _P by the exposure detecting means 13, it is possible to obtain information on the average brightness of the entire light receiving surface (exposure information).

For example, in the example shown in FIG. 1, exposure detection means
13 is configured as a current-voltage converter as described above, and in this current-voltage converter, the transparent electrode 12 is applied with a voltage equal to that of the negative power source 22 by virtual grounding, and the output of the exposure detection means 13 is output. At the terminal 24, the output voltage V _OUT shown by the following equation (1) appears. V _OUT = − (I _P + I _L ) · R _L (1) where I _P is the photocurrent corresponding to the amount of incident light, I _L is the leak current that flows even in the dark, and R _L is the current. The resistance value of the feedback resistor 23 of the voltage converter. As can be seen from the above equation (1), the output voltage V _OUT is proportional to the photocurrent I _P, and because the light current I _P is proportional to the amount of incident light, the output voltage V _OUT
The information on the amount of incident light appears in. When the leak current I _L is sufficiently smaller than the photocurrent I _P , the above equation (1) is approximated by the following equation (2). V _OUT = −I _P · R _L (2) The relationship between the amount of incident light and the output voltage V _OUT under these conditions is shown in FIG. From this figure, the output voltage V _OUT fluctuates in accordance with the temporal change of the incident light amount, and this output voltage V _OUT
It can be seen that represents exposure information that follows changes in the amount of incident light.

In the above-mentioned embodiment, the description has been made of the one using the interline transfer type CCD as the solid-state image pickup device existing under the photoelectric conversion film. However, the point of the present invention is that in a so-called stacked type solid-state imaging device in which photoelectric conversion films are stacked, among the electron-hole pairs generated in the photoelectric conversion film, the information is accumulated in the signal electrode on the solid-state imaging device side and becomes image information. The purpose is to detect a carrier having a polarity opposite to that of the carrier via an exposure detection means connected to an electrode provided on the main surface of the photoelectric conversion film opposite to the solid-state imaging device. Therefore, the solid-state image pickup device existing under the photoelectric conversion film is not limited to the interline transfer type CCD, but may be a MOS type image pickup device, a TSL type image pickup device, a SIT type image pickup device, an FGA type image pickup device, a BASIS.
When a photoelectric conversion film is laminated in all solid-state image pickup devices having junction type diodes as signal accumulators such as image pickup devices and AMI-type solid-state image pickup devices having detection electrodes of in-pixel signal detection transistors It goes without saying that the exposure information can be detected in the same manner as in the above embodiment.

Further, in the above embodiment, an example in which the photocurrent by the carrier having the opposite polarity to the carrier stored as the image information in the solid-state image pickup device is used as the exposure information has been described. It is obvious that can be used as information other than exposure information.

[0016]

As described above on the basis of the embodiments,
According to the present invention, in a solid-state image pickup device using a stack-type image pickup element, by providing an exposure detection means having a simple structure without adding or changing a new process in the manufacturing process of the solid-state image pickup element, It is possible to obtain the exposure information that instantly corresponds to the light amount.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional configuration diagram showing an embodiment of a solid-state imaging device according to the present invention.

FIG. 2 is a diagram showing the relationship between the amount of incident light and the output voltage of the exposure detection means in the embodiment shown in FIG.

[Explanation of symbols]

 1 p-type semiconductor substrate 2 n-type diffusion layer 3 n-type diffusion layer 4 p-type diffusion layer 5 oxide film 6 transfer electrode 7 insulating layer 8 metal electrode 9 insulating layer 10 pixel electrode 11 photoelectric conversion film 12 transparent electrode 13 exposure detecting means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideaki Yoshida 2-43-2 Hatagaya, Shibuya-ku, Tokyo Inside Olympus Optical Co., Ltd.

Claims (1)

Claim: What is claimed is: 1. A stacked solid-state image sensor having a film having a photoelectric conversion function, the upper surface of which is connected to a light-transmissive electrode, and the lower surface of which is connected to a pixel electrode provided for each pixel. In the solid-state imaging device used, of the electron-hole pairs generated by the light incident on the photoelectric conversion film, a carrier having a polarity opposite to that of a carrier collected for each pixel as image information is provided on the upper surface. A solid-state image pickup device, comprising: an exposure detection unit that detects the information via an electrode to obtain exposure information.