JPH02237067A - Solid-state image sensing device - Google Patents

Abstract

PURPOSE:To change solid-state image sensor optionally in exposure time through control by a method wherein a switching circuit capable of supplying a prescribed voltage is connected to a fourth conductivity type region isolated from its peripheral part. CONSTITUTION:A prescribed voltage is applied to a P-type diffusion layer or a fourth conductivity type region 12 which is formed on the surface of an N-type diffusion layer 11 as isolated from a P-type diffusion layer 10, whereby optical signal charges stored in a photoelectric conversion section are discharged to a semiconductor substrate. Therefore, optical signal charges can be discharged at an optional time between two optical signal readout times in succession. By this setup, a time between the discharge time of charges and a succeeding optical signal readout time can be defined as an exposure time, so that an optional, required exposure time can be set.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a solid-state imaging device having an electronic shutter function.

2. Description of the Related Art Conventionally, when taking an image using a video camera, for example, vertical planking is used as a means to electrically control the exposure time, from the time when the optical signal charge during one field period is read out to the vertical register. A method of reading out the optical signal charge accumulated in the photoelectric conversion unit during the period up to the time period from the vertical register and transferring it at high speed to sweep it out, and a method of supplying a predetermined voltage to the semiconductor substrate, A solid-state imaging device using a method of sweeping out optical signal charges accumulated in the photoelectric conversion section during the period to the semiconductor substrate has already been proposed.

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

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

First, when a signal is input from the signal input terminal 8 to connect the switch circuit 5 to the 10V DC voltage source 6, the potential in the depth direction of the photoelectric conversion section is N, as shown in FIG. Since the potential of the type diffusion layer 3 is lower than the potential of the P type diffusion layers 2 and 4, the photoelectrically converted optical signal charges are accumulated in the N type diffusion layer 3. next,
When a signal is input from the signal input terminal 8 to connect the switch circuit 5 to the 20V DC voltage source 7, the potential of the photoelectric conversion section is P-type, as shown by Z in FIG. A voltage is applied to the silicon substrate such that the potential of the diffusion layer 2 is lower than the potential of the N-type diffusion layer 3. Therefore, the optical signal charges accumulated in the N-type diffusion layer 3 are swept out to the silicon substrate 1, which has a lower potential.

Problems to be Solved by the Invention However, in the conventional configuration described above, the vertical register used to transfer the optical signal charge is used to sweep out the optical signal charge accumulated in the photoelectric conversion section at times other than the exposure time. It is necessary to perform high-speed transfer between the time when the data is read and the vertical blanking time. For this reason, the exposure time can only be changed by several types of fixed times, and furthermore, it has the drawback of consuming excess power.

In addition, as shown in the example in Fig. 4, the method of sweeping onto the semiconductor substrate without using a vertical register allows variable control of the desired exposure time, but requires a voltage source that can supply a large voltage to the semiconductor substrate. It had the disadvantage of being

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

Means for Solving the Problems In order to solve the problems, the solid-state imaging device of the present invention includes a first conductivity type semiconductor substrate, a first conductivity type semiconductor substrate formed on the first conductivity type semiconductor substrate, and a first conductivity type semiconductor substrate formed on the first conductivity type semiconductor substrate. is a second conductivity type region opposite to the second conductivity type region, a third conductivity type region opposite to the second conductivity type formed on the second conductivity type region, and a third conductivity type region formed on the third conductivity type region. In a photoelectric conversion section of a solid-state imaging device having a fourth conductivity type region opposite to the third conductivity type region formed separately from the second conductivity type region, a predetermined voltage is applied to the fourth conductivity type region. The optical signal charge accumulated in the charge conversion section can be swept out to the first semiconductor substrate at a low voltage.

Function: With this configuration, a predetermined voltage is supplied to the fourth conductivity type region, and the optical signal charge accumulated in the photoelectric conversion section can be swept out to the first semiconductor substrate, so that it is possible to sweep out the optical signal charge accumulated in the photoelectric conversion section to the first semiconductor substrate. The optical signal charge can be swept out at an arbitrary time from the time of reading out the next optical signal, and the time from the time when this charge is swept out to the time when the next optical signal charge is read can be set as the exposure time. That is, it is possible to control the exposure time to any desired value.

Further, the voltage supplied to the fourth conductivity type region when sweeping out the optical signal charges accumulated in the photoelectric conversion section is set such that the potential of the third conductivity type region is higher than the potential of the second conductivity type region. Sweeping can be done with a low voltage.

EXAMPLE An example of the present invention will be described below with reference to the drawings.

FIG. 1 shows a cross-sectional view of a photoelectric conversion section of a solid-state imaging device according to an embodiment of the present invention. In Figure 1, 9
10 is a P-type diffusion layer formed on the surface of the semiconductor substrate 9; 11 is an N-type diffusion layer forming the photoelectric conversion section formed on the surface of the P-type diffusion layer 10; , 12 is a P-type diffusion layer formed on the surface of the N-type diffusion layer 11 separately from the P-type diffusion layer 10, 13 is a DC voltage source that supplies a predetermined voltage to the semiconductor substrate, and 14 is a switch circuit. One of the fixed contacts is connected to the DC voltage source 15, and the other is grounded. 16 is a signal input terminal for controlling the switch 14.

The operation of the solid-state imaging device having the photoelectric conversion section 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 section shown in the example in Fig. 1 is expressed as X in Fig. 2. As shown, the N-type conductive region 11 is connected to the P-type conductive region 1.
Since the potential is lower than that of 0 and 12, optical signal charges can be accumulated in this N-type conductive region 11. Furthermore, since the potential of the P-type conductive region 10 is lower than that of the P-type conductive region 12, even if the optical signal charge accumulated in the N-type conductive region 11 continues to increase and the potential of the N-type conductive region 11 becomes high. , optical signal charges corresponding to exceeding the potential of the P-type conductive region 10 are automatically swept out to the semiconductor substrate 9, so that so-called blooming can be suppressed.

In addition, if a signal that connects the switch 14 to the DC voltage source 15 is input from the signal input terminal l6, the first
The potential in the depth direction of the photoelectric conversion section shown in the example is
As shown by Y in FIG. 2, by raising the potential of the P-type conductive region 12, the potential of the N-type conductive region 11 becomes higher than the potential of the P-type conductive region 10, and the potential is accumulated in the N-type conductive region 11. The optical signal charges that have been stored can be swept out to the N-type silicon substrate 9, which has a lower potential.

Furthermore, since the optical signal charge can be swept out without using a vertical register, the sweep pulse shown in B in FIG. 3 can be set at any desired time. Therefore, as shown in FIG. 3, the exposure time is the time from when the sweep pulse is supplied until the next readout pulse is supplied, and can be controlled to any desired time.

Further, a DC voltage source 15 with a voltage such as IOV that makes the potential of the P-type conductive region 10 lower than that of the N-type conductive region 11, which has the potential of Y in FIG. 2, is used as the DC voltage source 15. In the conventional example in which the above objective is achieved by supplying voltage to the semiconductor substrate 9, for example, IOV is supplied to the semiconductor substrate 9 during the exposure time, so in order to achieve the above objective, for example, 20 V DC is required. A voltage source is required. Therefore, in this embodiment, power consumption can be reduced.

As described above, according to this embodiment, by providing the switch circuit 14 capable of supplying a predetermined voltage to the P-type conductive region 12, any desired exposure time can be controlled.
Additionally, it can operate with low power consumption.

The peripheral vertical register section, horizontal register section, and output section of the embodiment shown in FIG. 1 are not shown, but are constructed in a conventionally known manner.

Effects of the Invention As described above, in the present invention, by connecting a switch circuit capable of supplying a predetermined voltage to a fourth conductivity type region separated from the surroundings, it is possible to variably control the exposure time at any desired time. Furthermore, since optical signal charges are swept out with a low voltage, an excellent solid-state imaging device that can reduce power consumption can be realized.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a photoelectric conversion section of a solid-state imaging device according to an embodiment of the present invention, FIG. 2 is a potential diagram in the depth direction in an embodiment of the present invention and a conventional example, and FIG. 3 is a diagram similar to that shown in FIG. FIG. 4 is a timing chart for reading and sweeping out charges necessary for explaining an example, and is a sectional view of a photoelectric conversion section of a conventional solid-state imaging device. 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. Name of agent゜Patent attorney Shigetaka Awano and 1 other person

Claims (1)

[Claims] 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 a second region having the one conductivity type formed on the first region. and a third region of the opposite conductivity type formed on the second region and separated from the first region, supplying a predetermined voltage to the third region of the photoelectric conversion unit, A solid-state imaging device characterized in that optical signal charges accumulated in the photoelectric conversion section can be swept out to the semiconductor substrate.