JP2532645B2 - Solid-state imaging device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a solid-state imaging device having an electronic shutter function.

2. Description of the Related Art Conventionally, when an image is captured using a video camera, for example, as a means for electrically controlling the exposure time, the vertical blanking is performed from the time when the optical signal charge during one field period is read out to the vertical register. Utilizing a period up to time, the optical signal charge accumulated in the photoelectric conversion unit during the period is read out from the vertical register, transferred at high speed and swept out, or a predetermined voltage is supplied to the semiconductor substrate, A solid-state imaging device using a method of sweeping out the optical signal charges accumulated in the public-electric conversion unit during the period to the semiconductor substrate has already been proposed.

FIG. 4 shows a sectional view of a photoelectric conversion part of a conventional solid-state imaging device. In FIG. 4, 1 is an N-type silicon substrate, 2 is a P-type diffusion layer formed on the N-type silicon substrate,
3 is an N-type diffusion layer formed on the P-type diffusion layer 2 and 4 is an N-type diffusion layer.
A P-type diffusion layer 5 formed on the type diffusion layer 3 is a switch circuit, one of which is connected to a DC voltage source 6 of 10V and the other of which is connected to a DC voltage source 7 of 20V, and a fixed terminal is a silicon substrate 1 8 is a signal input terminal for controlling the switch circuit 5.

The operation of the photoelectric conversion unit of the solid-state imaging device configured as described above will be described below.

First, when a signal for connecting the switch circuit 5 to the DC voltage source 6 of 10 V is input from the signal input terminal 8, the potential in the depth direction of the photoelectric conversion portion is N as shown in FIG. 2X. Since the potential of the type diffusion layer 3 is lower than the potentials of the P type diffusion layers 2 and 4, photoelectric conversion photoelectric signal charges are accumulated in the N type diffusion layer 3. Next, when a signal for connecting the switch circuit 5 to the 20V DC voltage source 7 is input from the signal input terminal 8, the potential of the photoelectric conversion unit is as shown by Z in FIG. , A voltage such that the potential of the P-type diffusion layer 2 becomes lower than the potential of the N-type diffusion layer 3 is applied to the silicon substrate. Therefore, the optical signal charges accumulated in the N type diffusion layer 3 are swept out to the silicon substrate 1 having a lower potential.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the above-described conventional configuration, since the vertical signal register used for transferring the optical signal charge is used to sweep out the optical signal charge accumulated in the predetermined region of the photoelectric conversion unit other than the exposure time, , It is necessary to perform high-speed transfer between the reading of the optical signal charge and the vertical blanking time. Therefore, the exposure time can only be changed by some fixed time,
In addition, it has the drawback of consuming extra power.

Also, as shown in the example of FIG. 4, in the method of sweeping to the semiconductor substrate without using the vertical register, the exposure time can be variably controlled, but a voltage source capable of supplying a large voltage to the semiconductor substrate is required. It had the drawback of being

The present invention solves the above-mentioned conventional problems. By supplying a predetermined voltage to the surface of the photoelectric conversion unit, the optical signal charge accumulated in a predetermined region of the photoelectric conversion unit is applied to the semiconductor substrate at a low voltage. An object of the present invention is to provide a solid-state imaging device that can be swept out and variably controlled to a desired exposure time.

Means for Solving the Problem In order to solve this problem, the solid-state imaging device of the present invention is
A semiconductor substrate having one conductivity type, and a first region formed on the semiconductor substrate and having a conductivity type opposite to the one conductivity type,
The second region of the one conductivity type formed on the first region and the third region of the opposite conductivity type formed on the second region separately from the first region. And a first power source for supplying a first predetermined voltage to the semiconductor substrate, and a second power source for directly supplying the second predetermined voltage between the semiconductor substrate and the third region. The semiconductor device further includes a second power supply capable of sweeping out the charges supplied and accumulated in the second region to the semiconductor substrate.

With this configuration, the second predetermined voltage is directly supplied to the third region, and the charges accumulated in the second region can be swept out to the semiconductor substrate. The optical signal charge can be swept out at an arbitrary time until the optical signal is read, and the exposure time can be from the time when the charge is swept out to the time when the next optical signal charge is read out. That is, it is possible to control to any desired exposure time.

In addition, the voltage supplied to the third region when sweeping out the charges accumulated in the second region may be a voltage such that the potential of the second region is higher than the potential of the first region, and thus is low. Sweep can be done with voltage.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a photoelectric conversion portion of a solid-state image pickup device according to an embodiment of the present invention. In FIG.
9 is a semiconductor substrate made of N-type silicon, 10 is a P-type diffusion layer formed on the surface of the semiconductor substrate 9, and 11 is a P-type diffusion layer 10.
The N-type diffusion layer forming the photoelectric conversion part formed on the surface of the N-type diffusion layer, the P-type diffusion layer 12 formed on the surface of the N-type diffusion layer 11 separately from the P-type diffusion layer 10, and the semiconductor 13 A DC voltage source for supplying a predetermined voltage to the substrate, 14 is a switch circuit, one of the fixed contacts is connected to the DC voltage source 15, and the other is grounded. Reference numeral 16 is a signal input terminal for controlling the switch 14.

The operation of the solid-state imaging device having the photoelectric conversion unit configured as described above will be described below.

First, when a signal that connects the switch 14 to the ground side is input from the signal input terminal 16, the potential in the depth direction of the photoelectric conversion unit illustrated in FIG. 1 is X in FIG. As shown, the N-type conductive region 11 has a lower potential than the P-type conductive regions 10 and 12, so
Optical signal charges can be stored at 11. Furthermore, the P-type conductive region 10
Has a lower potential than the P-type conductive region 12, so even if the photo-signal charge accumulated in the N-type conductive region 11 continues to increase and the potential of the N-type conductive region 11 increases, the potential of the P-type conductive region 10 increases. The optical signal charges corresponding to the amount exceeding the above are automatically swept out to the semiconductor substrate 9, and so-called blooming can be suppressed.

In addition, switch 14 from signal input terminal 16 to DC voltage source 15
In the case where a signal that is connected to the input terminal is input, the potential in the depth direction of the photoelectric conversion unit illustrated in FIG.
As indicated by Y in the figure, the potential of the N-type conductive region 11 becomes higher than the potential of the P-type conductive region 10 by raising the potential of the P-type conductive region 12.
The optical signal charges accumulated in the N-type conductive region 11 can be swept out to the N-type silicon substrate 9 having a lower potential.

Furthermore, since the optical signal charge can be swept without using the vertical register, the sweep pulse shown in B of FIG. 3 can be set at an arbitrary time. Therefore, the exposure time is the third
As shown in the figure, it is the time from the supply of the sweep pulse to the supply of the next read pulse, which can be controlled to any desired time.

Further, a DC voltage source of a voltage, for example, 10V, which lowers the potential of the P-type conductive region 10 than the N-type conductive region 11 having the Y potential of FIG. 2, is used as the DC voltage source 15. In the conventional example in which a voltage is supplied to the substrate 9 to achieve the above-mentioned object, the semiconductor substrate 9 is exposed during the exposure time.
Since, for example, 10 V is supplied to the device, a DC voltage source of, for example, 20 V is required to achieve the above object. Therefore, in this embodiment, power consumption can be reduced.

As described above, according to the present embodiment, by providing the switch circuit 14 capable of supplying a predetermined voltage to the P-type conductive region 12, it is possible to control any desired exposure time and reduce the consumption. It can operate on electricity.

The vertical register section, the horizontal register section, and the output section in the periphery of the embodiment of FIG.

As described above, according to the present invention, by connecting the switch circuit capable of supplying a predetermined voltage to the fourth conductivity type region separated from the periphery, it is possible to variably control the exposure time, Moreover, since the optical signal charges are swept out at a low voltage, it is possible to realize an excellent solid-state imaging device that can reduce power consumption.

[Brief description of drawings]

FIG. 1 is a sectional view of a photoelectric conversion part of a solid-state image pickup device in one embodiment of the present invention, FIG. 2 is a potential diagram in the depth direction in one embodiment of the present invention and a conventional example, and FIG. 3 is FIG. FIG. 4 is a sectional view of a photoelectric conversion unit of a conventional solid-state imaging device, and FIG. 1 ... N type silicon substrate, 2 ... P type diffusion layer, 3 ... N
Type diffusion layer, 4 ... P type diffusion layer, 5 ... switch circuit, 6
...... DC voltage source, 7 ...... DC voltage source, 8 ...... Switch control terminal, 9 ...... N type silicon substrate, 10 ...... P type diffusion layer,
22 …… N type diffusion layer, 12 …… P type diffusion layer, 13 …… DC voltage source, 14 …… Switch circuit, 15 …… DC voltage source, 16 …… Switch control terminal.

Claims (1)

(57) [Claims] 1. A semiconductor substrate having one conductivity type, a first region formed on the semiconductor substrate and having a conductivity type opposite to the one conductivity type, and the one region formed on the first region. A second region of conductivity type, a third region of opposite conductivity type formed separately from the first region on the second region, and a first predetermined voltage are applied to the semiconductor substrate. A second predetermined voltage is directly supplied by connecting the first power source to be supplied and the first power source between the semiconductor substrate and the third region, and the second predetermined voltage is stored in the second region. A solid-state imaging device comprising a second power supply capable of sweeping charges to the semiconductor substrate.