JPH0318389B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an imaging device using a charge transfer device.

Charge transfer devices are being rapidly developed from the viewpoints of small size, light weight, low power consumption, and high reliability, which are characteristics of solid-state imaging devices.

However, when considering the benefits and disadvantages of charge transfer devices as imaging devices, in addition to the advantages of solid-state imaging mentioned above,
Although it is superior to currently used image pickup tubes in terms of noise, afterimage burn-in, etc., it is difficult to achieve high integration, so there remains a major problem in resolution.

Imaging devices using charge transfer devices have been developed in systems called a frame transfer method and an interline transfer method, and the present invention relates to a charge transfer imaging device using an interline transfer method.

As shown in FIG. 1, a conventional charge transfer imaging device using an interline transfer method includes a plurality of columns of vertical shift registers 1 driven by the same charge transfer electrode group, and
A photoconversion section 2 adjacent to one side of each vertical shift register and electrically isolated from each other and arranged in a matrix; a transfer electrode 3 for controlling signal charges between the vertical shift register and the photoelectric conversion section; It consists of a charge transfer horizontal shift register 4 electrically coupled to one end of each vertical shift register, and a device (output section) 5 for detecting signal charges at one end of the horizontal shift register.

A block diagram of a unit cell of the two-phase drive interline transfer method is shown in FIG. 2a. The unit cell is composed of a photoelectric conversion section 1, a transfer electrode 3, a vertical shift register 1 consisting of a barrier region 6 and a storage region 7, and a channel stop region 8 provided to separate adjacent cells. In other words, the photoelectric conversion unit 2 and the transfer electrode 3 are connected to each other during one pitch l in the horizontal direction.
It is composed of four areas: a vertical shift register 1, and a channel stop area 8. In order to increase the number of picture elements in order to increase the resolution in the horizontal direction using the interline transfer method, it is possible to simply increase the number of picture elements while keeping 1 pitch l, or to increase the number of picture elements by decreasing 1 pitch l. If the number of picture elements is increased without changing the pitch, the chip area will increase and the yield will decrease. Furthermore, in order to reduce the pitch l and increase the number of picture elements, it is necessary to reduce the pattern dimensions of each of the four regions: the photoelectric conversion section 2, the transfer electrode 3, the vertical shift register 1, and the channel stop region 8. The miniaturization of pattern dimensions is related to the process, and there is a limit to the miniaturization of pattern dimensions.

Therefore, a case where the unit cell is rotated by an angle θ is shown in FIG. 2b. The pitch in the horizontal direction is l'=lsinθ, and since sinθ≦1, the pitch l’ is smaller than l. That is, when unit cells are rotated by an angle θ and arranged in a matrix, the horizontal dimension within the same chip is reduced. However, the vertical pitch is m/sinθ (m: vertical pitch before rotation)
This increases the chip size in the vertical direction, which becomes a problem.

An object of the present invention is to provide a solid-state imaging device with a new structure that eliminates the above-mentioned drawbacks.

According to the present invention, a plurality of charge transfer electrode groups are formed on a semiconductor substrate and can be driven by a plurality of phase pulses, and a charge storage region and a current passing region can be driven by the plurality of charge transfer electrode groups. , a group of vertical shift registers that perform charge transfer in a plurality of columns that are electrically isolated from each other; and a group of vertical shift registers that are electrically isolated from each other by a channel stop means between the vertical shift registers, and are arranged in a matrix, and are capable of accumulating charges. a photoelectric conversion section, a transfer control section region that transfers charges photoelectrically converted in the photoelectric conversion section provided between the photoelectric conversion section and the charge accumulation region to the charge accumulation region, and one end of each of the vertical shift registers. a charge transfer horizontal shift register electrically coupled to a charge transfer horizontal shift register, and a charge detection device at one end of the horizontal shift register, the photoelectric conversion unit, the transfer control region, and the charge passing region of the vertical shift register; and a charge storage region are arranged in a matrix at an angle of 0° < θ < 90° with respect to the horizontal shift register, and the lower edge of the charge passing region of the vertical shift register. coincides with the upper edge of the charge accumulation region of the vertical shift register of the Nth unit cell, and the upper edge of this charge passing region coincides with the charge accumulation region of the vertical shift register of the (N-1)th unit cell. A charge transfer imaging device is obtained, characterized in that the vertical shift register is perpendicular to the horizontal register and also coincides with the lower edge.

Next, the present invention will be explained using drawings showing embodiments thereof.

FIG. 3 is a schematic structural diagram for explaining the solid-state imaging device of the present invention, FIG. 4 is an enlarged view of the present invention showing two cells in FIG. 3, and FIG. 5 is a diagram showing another embodiment of the present invention. be.

Since an interline transfer type charge transfer imaging device consists of four regions in the horizontal direction: a photoelectric conversion section, a transfer electrode, a vertical shift register, and a channel stop region, it is difficult to reduce the size in the horizontal direction. However, as already mentioned, if the unit cell is rotated by an angle θ, it can be reduced by a factor of sin θ in the horizontal direction, but it is enlarged by a factor of 1/sun θ in the vertical direction.
Since the vertical direction of the interline transfer method consists of a photoelectric conversion section and a channel stop region, or a vertical shift register is composed of two regions each, a barrier region and a storage region, it can be reduced in size compared to the horizontal direction. Therefore, in the interline transfer method, by rotating the unit cell by an angle θ with respect to the horizontal shift register and reducing the vertical pattern dimension, it is possible to increase the number of pixels in the horizontal direction with the same chip area. It is. FIG. 3 corresponds to FIG. 1 illustrating a conventional interline transfer device, and is a schematic diagram showing the basic configuration of the present invention. The charge transfer imaging device of the present invention includes a plurality of charge transfer electrode groups that are formed on a semiconductor substrate and can be driven by a plurality of phase pulses, and three rows that can be driven by the plurality of charge transfer electrode groups and that are electrically separated from each other. vertical shift register
R ₁ to _{R 3} and the vertical shift register are electrically isolated from each other by a channel stop 11;
Photoelectric conversion units P ₁₁ to _{P 33} arranged in a 3×3 matrix and capable of accumulating charges, and transfer control regions T ₁₁ to _{T 33} that control signal charge transfer between the vertical shift register and the photoelectric conversion units; Each vertical shift register R ₁
It consists of a charge transfer horizontal shift register electrically coupled to one end of ~ _R3 , and a device 10 for detecting signal charges at one end of the horizontal shift register.
Note that charge transfer electrodes for driving the vertical shift registers R ₁ to _{R 3} are omitted in FIG. 3 because the drawing is complicated. The unit cell in the charge transfer imaging device of the present invention includes, for example, a photoelectric conversion section _P11 , a transfer control region _T11 , a charge passing region ₁₁ , and a charge accumulation region _S11.
It is characterized by being rotated by an angle θ ₁ with respect to the horizontal shift register. In order to _obtain an _imaging output from _the charge transfer imaging device of the present invention, in _FIG . The charges are transferred to the charge storage regions S ₁₁ to _{S 33} of the corresponding vertical shift registers, and then the vertical shift registers sequentially transfer the charges, and
Signal charges are read out every horizontal scan through the horizontal shift register 9. In this way, the desired imaging output can be obtained from the output section of the horizontal shift register 9.

FIG. 4 shows an enlarged version of FIG. 3, which is a schematic diagram of the structure of the present invention. The unit cell consists of the photoelectric conversion section _P32 , the transfer region _T12 , and the charge storage region of the vertical shift register.
S ₂₂ and vertical shift register charge passing area B ₃₂
and a channel stop region 12. The unit cell is rotated by an angle θ ₁ with respect to the horizontal shift register, and the size of the charge passing region B ₂₂ of the vertical shift register is reduced in the vertical direction. Since the charge passing region B ₂₂ of the vertical shift register is a passing region for signal charges between the charge accumulation region S ₂₂ and the charge accumulation region S ₃₂ of the vertical shift register,
Both channel width and channel length can be made smaller. Therefore, with the same chip size, by using this structure, the number of picture elements in the horizontal direction can be increased. Furthermore, even if the unit cell is rotated, the upper edge of the charge passing region B ₃₂ must match the lower edge of the charge accumulation region S ₂₂ of the vertical shift register in the previous stage, so that the vertical shift register is arranged perpendicularly to the horizontal shift register. It is also necessary that the If the signal charges are not transferred vertically, an abnormality will occur in the imaging output. The vertical shift register shown in FIG. 4 is composed of a charge passing region B ₃₂ and a charge storage region S ₃₂ using the same transfer electrode. Charge passing area B ₃₂
When the channel width is narrowed, the channel potential of the charge passing region _B32 becomes shallower than the channel potential of the charge storage accumulation region due to the narrow channel effect, which acts as a barrier region and improves the directionality of signal charge transfer. It's coming. That is, it can be operated with two-phase drive. Further, in order to improve the directionality of charge transfer in two-phase drive, the charge passing region may be formed of a conductivity type different from that of the substrate semiconductor. It can be driven not only in two phases but also in 1 to n phases.

FIG. 5 is a schematic structural diagram showing an embodiment of another cell shape of the present invention. The unit cell includes a photoelectric conversion section P ₁₁ , a transfer region T ₁₁ , a charge storage region S ₁₁ of a vertical shift register, and a charge passing region B ₁₁ of a vertical shift register.
and a channel stop region 11. The difference from FIG. 3 is that the cell shape of the photoelectric conversion section is made into an ellipse so that the drop in sensitivity at high density can be minimized. In this way, the present invention can be practiced not only when the unit cell has a rectangular cell shape as shown in FIG. 3, but also when the unit cell has other shapes.

In the present invention, the angle θ of the unit cell with respect to the horizontal shift register is most ideal when it is 45°, but preferable results are obtained when 0°<θ<90°. Further, the semiconductor substrate may be of N type or P type,
The photoelectric conversion section may be a MOS type capacitor or a P-N junction, and the vertical shift register may be a surface channel type.
Even with the embedded channel type, the same operation can be achieved.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional charge transfer imaging device, FIG. 2 is a diagram for explaining the principle of the present invention, FIG. 3 is a schematic structural diagram of a charge transfer imaging device according to the present invention, and FIG. 4 is a diagram for explaining the principle of the present invention. A partially enlarged view of FIG. 3 and FIG. 5 show another example of application. In the figure, 1...vertical shift register, 2...
... Photoelectric conversion section, 3 ... Transfer electrode, 4 ... Horizontal shift register, 5 ... Output section, 6 ... Barrier region,
7... Storage area, 8... Channel stop area, 9... Horizontal shift register, 10... Output section, 11... Channel stop area, 12... Channel stop area, 13, 14... Transfer electrode of vertical shift register, 15 ... Channel stop region, 16 ... Horizontal shift register, 17 ... Output section, P ₁₁ to _{P 33} ... Photoelectric conversion section, S ₁₁ to _{S 33} ... Charge storage region of vertical shift register, B ₁₁ to B ₃₃ ...
...Charge passing region of vertical shift register, T ₁₁ ~
_T33 ...Transfer control area from the photoelectric conversion unit to the charge storage area of the vertical shift register.

Claims (1)

[Claims] 1 A charge transfer electrode group formed on a semiconductor substrate that can be driven by a plurality of phase pulses, and a charge storage region and a charge passage region that can be driven by the plurality of charge transfer electrode groups and are electrically separated from each other. a group of vertical shift registers that perform charge transfer in a plurality of columns; a photoelectric conversion unit that is electrically isolated from each other by a channel stop means between the vertical shift registers, is arranged in a matrix, and is capable of accumulating charges; a transfer control region that is provided between the conversion section and the charge storage region and transfers the charge photoelectrically converted in the photoelectric conversion section to the charge storage region; and a charge transfer region that is electrically coupled to one end of each of the vertical shift registers. In a charge transfer imaging device having a horizontal shift register and a charge detection device at one end of the horizontal shift register, an N-th charge transfer imaging device comprising the photoelectric conversion section, the transfer control region, and a charge passing region and a charge accumulation region of the vertical shift register. The Nth unit cells are arranged in a matrix at an angle of 0° < θ < 90° with respect to the horizontal shift register, and the lower edge of the charge passing area of the vertical shift register is perpendicular to the Nth unit cell. The upper edge of the charge accumulation region of the shift register coincides with the upper edge of this charge passing region, and the upper edge of this charge passing region coincides with the lower edge of the charge accumulation region of the vertical shift register of the (N-1)th unit cell, and the vertical shift A charge transfer imaging device characterized in that a register is perpendicular to the horizontal register.