JPH06165049A - Solid-state image pickup device - Google Patents

Abstract

PURPOSE:To exactly perform the control of charge storage time or the gain setting of an external signal amplifier by exactly and speedily detecting the surface illuminance of a semiconductor substrate. CONSTITUTION:Plural photodiodes 3B for monitoring the surface illuminance of a semiconductor substrate 1, one impurity diffusing layer 5B connected through wiring 4B to the respective photodiodes 3B for illuminance monitor and a floating diffusion amplifier 7B connected through an output gate 6B to the impurity diffusing layer 5B are respectively formed on the surface of the semiconductor substrate 1. Since the photodiodes 3B for illuminance monitor are distributedly formed and a voltage signal outputted from the floating diffusion amplifier 7B is exactly reflected with the surface illuminance of the semiconductor substrate 1, the gain setting of the external signal amplifier or the control of signal charge storage time at the photodiode can be exactly and speedily performed.

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 which stores a signal charge generated by incident light for a certain period of time in a photodiode for image pickup and sequentially reads out the signal charge stored in the photodiode.

[0002]

2. Description of the Related Art In recent years, solid-state image pickup devices have come into widespread use and have come to be used under various environmental conditions. Along with this, there has been a demand for a technique capable of easily setting an appropriate imaging condition even under a wide range of illuminance conditions.

Therefore, in order to detect the illuminance on the surface of the semiconductor substrate, in the conventional solid-state image pickup device, after outputting all pixels, the gain setting of the external signal amplifier and the photodiode are performed based on the output levels of all the pixels. The signal charge storage time was controlled.

However, in this method, since the surface illuminance of the semiconductor substrate is monitored based on the output levels of all pixels, there is a problem that the surface illuminance of the semiconductor substrate cannot be determined until the read cycle is completed. It was

Therefore, in order to detect the illuminance on the surface of the semiconductor substrate easily and quickly, a photodiode for illuminance monitor is provided on the semiconductor substrate in addition to the photodiode for imaging, and the output of the photodiode for illuminance monitor on the substrate surface is provided. A solid-state imaging device has been proposed which estimates the illuminance on the surface of a semiconductor substrate by monitoring it externally.

FIG. 4 shows a schematic plane structure of this solid-state image pickup device. A plurality of image pickup photodiodes 2 arranged two-dimensionally on the semiconductor substrate 1 and the semiconductor substrate 1 are shown.
One illuminance monitoring photodiode 3A for monitoring the surface illuminance of the illuminant, an impurity diffusion layer 5A connected to the illuminance monitoring photodiode 3A, and a floating connection connected to the impurity diffusion layer 5A via an output gate 6A. A diffusion amplifier 7A is formed respectively. The output of the floating diffusion amplifier 7A is taken out from the monitor output terminal 8A, and the signal charge stored in the image pickup photodiode 2 is transferred to the outside by the charge transfer section 9 and then taken out from the image pickup data output terminal 10. Be done.

[0007]

However, in this solid-state image pickup device, since the surface illuminance of the semiconductor substrate is detected by one photodiode, only the local illuminance can be monitored, and the entire surface of the semiconductor substrate can be monitored. There was a problem that the illuminance of could not be accurately determined.

In view of the above, according to the present invention, the surface illuminance of the semiconductor substrate can be detected accurately and quickly, so that the charge storage time can be controlled and the gain of the external signal amplifier can be set accurately. The purpose is to

[0009]

In order to achieve the above object, the invention according to claim 1 or 2 provides a plurality of illuminance monitor photodiodes for monitoring the illuminance of the surface of the semiconductor substrate. However, the outputs of the plurality of illuminance monitoring photodiodes are output from one or a plurality of output circuits.

Specifically, the solution means taken by the invention of claim 1 is directed to a solid-state image pickup device in which photodiodes for image pickup are arranged one-dimensionally or two-dimensionally on a semiconductor substrate, and the semiconductor substrate A plurality of illuminance monitoring photodiodes formed on the semiconductor substrate for monitoring the surface illuminance of the semiconductor substrate; and a plurality of illuminance monitoring photodiodes formed on the semiconductor substrate and connected to the illuminance monitoring photodiodes, respectively. This structure is provided with one impurity diffusion layer and one floating diffusion amplifier formed on the semiconductor substrate and connected to the impurity diffusion layer via an output gate.

Further, specifically, the solution means devised by the invention of claim 2 is intended for a solid-state image pickup device in which photodiodes for image pickup are arranged one-dimensionally or two-dimensionally on a semiconductor substrate, and A plurality of illuminance monitor photodiode groups each including a plurality of illuminance monitor photodiodes formed on the semiconductor substrate to monitor the surface illuminance of the semiconductor substrate, and the plurality of illuminance monitor photodiodes on the semiconductor substrate. Formed corresponding to the photodiode group,
A plurality of impurity diffusion layers connected to each of the plurality of illuminance monitoring photodiodes forming a corresponding illuminance monitoring photodiode group, and formed on the semiconductor substrate corresponding to the plurality of impurity diffusion layers And a plurality of floating diffusion amplifiers connected to each of the plurality of impurity diffusion layers via output gates.

[0012]

According to the structure of claim 1 or 2, when the surface of the semiconductor substrate is irradiated with the incident light, the signal charges are accumulated in the photodiode for image pickup, and the plurality of the plurality of electrodes are dispersedly formed on the semiconductor substrate. The signal charges are also accumulated in the individual illuminance monitor photodiodes. The signal charge accumulated in the illuminance monitoring photodiode is transferred to the impurity diffusion layer and then output as a voltage signal from the floating diffusion amplifier to the outside through the output gate.

In this case, since the illuminance monitor photodiodes are formed dispersedly on the semiconductor substrate, the voltage signal output from the floating diffusion amplifier accurately reflects the surface illuminance of the semiconductor substrate. Therefore, the surface illuminance of the semiconductor substrate is determined based on the voltage signal output from the floating diffusion amplifier every predetermined time, and the gain setting of the external signal amplifier and the signal charge storage time in the photodiode are controlled according to this determination. You can

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a schematic structure of a solid-state image pickup device according to a first embodiment of the present invention, FIG. 2A shows a sectional structure of a main part of the solid-state image pickup device, and FIG. The potential distribution of the part corresponding to a) is shown, respectively.

As shown in FIG. 1, a plurality of two-dimensionally arranged imaging photodiodes 2 are formed on the surface of a semiconductor substrate 1, and the signal charges accumulated in the imaging photodiodes 2 are After being transferred by the charge transfer unit 9,
It is taken out from the imaging data output terminal 10.

Further, as shown in FIGS. 1 and 2 (a),
On the surface portion of the semiconductor substrate 1, a plurality of illuminance monitoring photodiodes 3B for monitoring the surface illuminance of the semiconductor substrate 1 are formed adjacent to the imaging photodiode 2 in a dispersed state. On the surface of
One impurity diffusion layer 5B connected to each of the plurality of illuminance monitoring photodiodes 3B via a wiring 4B, and one floating diffusion connected to the impurity diffusion layer 5B via an output gate 6B. An amplifier 7B is formed respectively, and the voltage signal from the floating diffusion amplifier 7B is taken out from the monitor output terminal 8B. Incidentally, FIG. 2 (a)
In the figure, 11 is an insulating film, and 12 is a source follower amplifier internal wiring.

FIG. 3 shows a schematic structure of a solid-state image pickup device according to the second embodiment of the present invention.

As shown in FIG. 3, a plurality of two-dimensionally arranged imaging photodiodes 2 are formed on the surface of the semiconductor substrate 1 as in the first embodiment. The signal charge accumulated in the diode 2 is transferred to the charge transfer unit 9
After being transferred by, the image data is taken out from the imaging data output terminal 10.

As shown in the figure, on the surface of the semiconductor substrate 1, a plurality of illuminance monitoring photodiodes 3C for monitoring the surface illuminance of the semiconductor substrate 1 are adjacent to the imaging photodiode 2. It is formed in a dispersed state. Further, on the surface portion of the semiconductor substrate 1, a plurality of impurity diffusion layers 5C are formed corresponding to a group of illuminance monitoring photodiodes composed of a plurality of illuminance monitoring photodiodes 3C. A plurality of floating diffusion amplifiers 7C are formed corresponding to the individual impurity diffusion layers 5C. The corresponding illuminance monitor photodiode group and the impurity diffusion layer 5C are connected by a wiring 4C, and the corresponding impurity diffusion layer 5C and the floating diffusion amplifier 7C are connected.
Are connected via the output gate 6C, and the voltage signal from the floating diffusion amplifier 7C is taken out from the monitor output terminal 8C.

[0021]

According to the invention of claim 1 or 2, since the illuminance monitor photodiodes are formed dispersedly on the semiconductor substrate, the voltage signal output from the floating diffusion amplifier accurately reflects the surface illuminance of the semiconductor substrate. Therefore, the surface illuminance of the semiconductor substrate is determined based on the voltage signal output from the floating diffusion amplifier every predetermined time, and the gain setting of the external signal amplifier and the signal charge storage time in the photodiode are controlled according to this determination. The gain setting and signal charge storage time can be controlled accurately and promptly.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a solid-state imaging device according to a first embodiment of the present invention.

FIG. 2A is a sectional view of a main part of the solid-state imaging device according to the first embodiment, and FIG. 2B is a diagram showing a potential distribution of a part corresponding to FIG.

FIG. 3 is a schematic configuration diagram of a solid-state imaging device according to a second embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of a conventional solid-state imaging device.

[Explanation of symbols]

1 Semiconductor Substrate 2 Imaging Photodiodes 3A, 3B, 3C Illumination Monitor Photodiodes 4B, 4C Wirings 5A, 5B, 5C Impurity Diffusion Layers 6A, 5B, 5C Output Gates 7A, 7B, 7C Floating Diffusion Amplifiers 8A, 8B, 8C Monitor terminal 9 Charge transfer section 10 Imaging data output terminal 11 Insulating film 12 Source follower amplifier internal wiring

Claims (2)

[Claims] 1. A solid-state image pickup device comprising photodiodes for image pickup arranged one-dimensionally or two-dimensionally on a semiconductor substrate, wherein the surface of the semiconductor substrate is dispersedly formed on the semiconductor substrate. A plurality of illuminance monitoring photodiodes for monitoring illuminance, one impurity diffusion layer formed on the semiconductor substrate and connected to each of the plurality of illuminance monitoring photodiodes, and formed on the semiconductor substrate And a floating diffusion amplifier connected to the impurity diffusion layer via an output gate. 2. A solid-state image pickup device comprising photodiodes for image pickup arranged one-dimensionally or two-dimensionally on a semiconductor substrate, the surface of the semiconductor substrate being dispersedly formed on the semiconductor substrate. A plurality of illuminance monitor photodiode groups consisting of a plurality of illuminance monitor photodiodes for monitoring illuminance and a plurality of illuminance monitor photodiode groups formed on the semiconductor substrate in correspondence with the illuminance monitor photodiode groups. A plurality of impurity diffusion layers connected to each of the plurality of illuminance monitoring photodiodes forming a photodiode group, and a plurality of impurity diffusion layers formed on the semiconductor substrate corresponding to the plurality of impurity diffusion layers. Each of the impurity diffusion layers is provided with a plurality of floating diffusion amplifiers connected via an output gate. And a solid-state image pickup device.