JP2003168795A - Solid state image pickup element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate a defect wherein a handling amount of charges is small in the vicinity of a central part of a solid state image pickup element, and blooming resistance is small in the vicinity of a peripheral part of the solid state image pickup element. <P>SOLUTION: Transfer channel width at a central part in a horizontal direction of a solid state image pickup element is made larger than that of a peripheral part. The reading gate length of the peripheral part is made longer than that of the central part in the horizontal direction. <P>COPYRIGHT: (C)2003,JPO

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 sensor used in digital still cameras, video cameras and the like. More specifically, the present invention relates to a solid-state image sensor having a vertical transfer section independent of a light receiving section.

[0002]

2. Description of the Related Art A conventional CCD (Charge Coupled Devic)
e) In the solid-state imaging device, as shown in FIG. 7, a plurality of light receiving parts 101, ...
An image pickup unit having a vertical transfer unit 102 for transferring charges from each light receiving unit provided for each vertical column, and the vertical transfer unit 1.
, The horizontal transfer unit 103 that transfers the transferred charges in the horizontal direction and the output unit 104 that outputs the charges transferred from the horizontal transfer unit 103 as a voltage, and the vertical transfer unit. 102 is a vertical transfer clock 105
Is input from both sides of the pixel area.

In the conventional CCD solid-state image pickup device shown in FIG. 7, the transfer channel width of the vertical transfer portion and the read gate length are all the same width and the same length at any position in the horizontal direction. ing. Further, the transfer clock is applied to the vertical transfer portion by a wiring such as polysilicon provided on both sides of the light receiving portion.

[0004]

By the way, the conventional CC
In the D solid-state image pickup device, as shown in FIG. 8, the input waveform A from the vertical transfer clock is a waveform B near the center in the horizontal direction due to the electrical resistance and capacitance components of the polysilicon wiring, and a waveform B near the periphery. That is, the vertical transfer clock waveform becomes dull compared to the waveform C immediately before entering the screen from the wiring portion, and the stop time at the maximum / minimum voltage of the pulse becomes shorter, and the charge transfer capability is reduced. The amount of electric charge handled by the parts is reduced. On the other hand, in the peripheral portion in the horizontal direction, since the waveform of the vertical transfer clock is less blunt, the reading gate, which is a gate used for sweeping charges from the pixel provided between the pixel and the vertical transfer unit to the vertical transfer unit, is used. The potential is apt to change, and the difference in potential between the read gate and the overflow barrier in the overflow structure, that is, the blooming resistance is practically reduced as described in JP-A-60-182768. That is, the handled charge amount indicated by the symbol D in FIG. 9 is small in the horizontal central portion and is large in the peripheral portion, while the blooming resistance indicated by the symbol E in FIG. 9 is large in the horizontal central portion and is in the peripheral portion. However, there is a problem that it is difficult to satisfy both the handling charge amount and the blooming resistance.

The present invention was devised in view of the above points, and an object of the present invention is to provide a solid-state image pickup device capable of practically improving both the charge handling amount and the blooming resistance of the CCD solid-state image pickup device. It is what

[0006]

In order to achieve the above object, in a solid-state image pickup device according to the present invention, a plurality of light receiving portions are arranged in a matrix, and each light receiving portion is provided in each vertical column. An image pickup unit having a vertical transfer unit for transferring charges from the light receiving unit, a horizontal transfer unit for transferring charges from the vertical transfer unit and transferring the transferred charges in a horizontal direction, and a charge transferred by the horizontal transfer unit. In the solid-state imaging device having an output section for outputting the above, the transfer channel width of the vertical transfer section in the central part in the horizontal direction is made larger than the transfer channel width of the vertical transfer section in the peripheral part.

Here, the transfer channel width of the vertical transfer unit in the central portion in the horizontal direction is made larger than the transfer channel width of the vertical transfer unit in the peripheral portion because the amount of charges handled by the vertical transfer unit is as shown in FIG.
This is because the transfer channel width increases substantially in proportion to the size of the transfer channel width, so that the amount of charge handled in the central portion can be increased.

In order to achieve the above-mentioned object, in the solid-state image pickup device according to the present invention, a plurality of light receiving parts are arranged in a matrix, and an electric charge is supplied from each light receiving part provided in each vertical column of the light receiving parts. An image pickup unit having a vertical transfer unit for transferring the charges, a horizontal transfer unit for transferring the charges from the vertical transfer unit and transferring the transferred charges in the horizontal direction, and an output for outputting the charges transferred by the horizontal transfer unit. And a transfer channel width of the vertical transfer unit in the horizontal center is larger than the transfer channel width of the vertical transfer unit in the peripheral region, and the transfer channel width is larger than the read gate length in the horizontal center. The read gate length of the part was increased.

As described above, the amount of charge handled in the central portion can be increased by increasing the transfer channel width of the vertical transfer portion in the central portion in the horizontal direction, as described above. In addition, the read gate length in the peripheral portion is made larger than the read gate length in the central portion in the horizontal direction because the blooming resistance becomes large in proportion to the read gate length as shown in FIG. This is because the blooming resistance of the peripheral portion can be increased.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings, for the understanding of the present invention.

FIG. 3 is a block diagram showing an example of a solid-state image pickup device to which the present invention is applied. In FIG. 3, a plurality of light receiving portions 1, ... Are arranged in a matrix, and the light receiving portion 1
The vertical transfer section 2 that transfers charges from each light receiving section provided for each vertical column of the light receiving section 1 constitutes an imaging section. The horizontal transfer unit 3 is provided on the lower side of the imaging unit in the drawing.
Are arranged. Electric charges corresponding to one line are sequentially transferred from the plurality of vertical transfer units 2 to the horizontal transfer unit 3.

At the end of the transfer destination of the horizontal transfer section 3, a charge-voltage conversion section 4 having, for example, a floating diffusion amplifier configuration is provided. This charge-voltage converter 4
The charges are sequentially converted into voltage signals by the horizontal transfer unit 3 and output from the output unit 5. Further, the vertical transfer section 6 is configured so that the vertical transfer clock 6 is input from both sides of the pixel area.

In one example of the solid-state image pickup device to which the present invention is applied, vertical transfer can be performed by utilizing the characteristic of the solid-state image pickup device that the amount of charge handled in the vertical transfer portion becomes large in proportion to the size of the transfer channel width. The horizontal width of the vertical transfer unit 2 at the central portion in the horizontal direction of the solid-state imaging device in which the waveform of the clock 6 is dull, that is, the transfer channel width D ₁ is the vertical transfer unit 2 in the peripheral portion where the waveform of the vertical transfer clock 6 is not dull. Is larger than the transfer channel width D ₁ .

As described above, when the transfer channel width D ₁ of the vertical transfer unit 2 is set to be larger than the peripheral central portion of the solid-state image sensor, the transfer channel width D _{1 is set} to the horizontal direction of the solid-state image sensor. It is preferable to sequentially increase the size from the peripheral part to the central part.

Here, the transfer channel width D ₁ of the vertical transfer portion 2 of the solid-state image pickup device is gradually increased from the peripheral portion in the horizontal direction of the solid-state image pickup device toward the central portion thereof. _This is because if ₁ is larger than the transfer channel width D _{1 in the} peripheral portion, the handled charge amount in the central portion is large, and it is sufficient if the handled charge amount in the central portion is large. Transfer channel width D
₁ need not be successively increased, the transfer channel width D ₁ of the central portion may be greater than the transfer channel width D ₁ of the peripheral portion, but from the periphery of the handling charge amount of the vertical transfer portion 2 as it goes to the central portion The method of change gradually changes, that is, changes gradually, the increase is larger in the central part and the amount of increase is decreased gradually toward the peripheral part, and conversely the amount of charge handled is decreased at the peripheral end, and The transfer channel width D ₁ is preferably increased sequentially from the peripheral portion to the central portion because the transfer channel width D ₁ is substantially the same throughout the horizontal width.

The transfer channel width D ₁ of the vertical transfer unit 2
In the case where the horizontal central portion of the solid-state image sensor is made larger than the peripheral portion, the same transfer channel width is set for every several or several tens, and it is gradually increased from the peripheral portion toward the central portion. Adopting the method is preferable in actual design.

Here, the transfer channel width D ₁ of the vertical transfer section 2 of the solid-state image pickup device is set to the same transfer channel width every several or several tens, and is gradually increased from the peripheral portion toward the central portion. The reason is that if the transfer channel width D _{1 in the} central portion is larger than the transfer channel width D ₁ in the peripheral portion, the handled charge amount in the central portion becomes large, and it is sufficient if the handled charge amount in the central portion becomes large. Therefore, it is not always necessary to have the same transfer channel width for every several or several tens, and to increase the transfer channel width D ₁ in the central portion from the transfer channel width in the peripheral portion in a stepwise manner from the peripheral portion to the central portion. it may be greater than D _1, since the vertical transfer portion 2 of the solid-state imaging device is a very large number, the transfer channel width D ₁ is the same transfer channel width by one by several or several tens of, in the central portion than the peripheral portion Step by step Kikusuru of is on the actual design is preferred.

In the solid-state image sensor to which the present invention is applied, the phenomenon as shown in FIG. 9 in the case where the transfer channel width of the vertical transfer unit is the same at all positions in the horizontal direction of the solid-state image sensor, that is, the vertical transfer unit. The phenomenon that the amount of electric charge handled by the product is smaller in the horizontal center than in both peripheral parts is improved.
The amount of charge handled in the central portion becomes large.

Further, in another example of the solid-state image pickup device to which the present invention is applied, vertical transfer can be performed by utilizing the characteristic of the solid-state image pickup device that the blooming resistance becomes large substantially in proportion to the size of the read gate length. The transfer channel width D ₁ of the part 2 is made larger in the central part than in the peripheral part, and the vertical transfer part 2
The length between the light receiving portion 1 and the light receiving portion 1, that is, the read gate length D ₂ is made larger in the peripheral portion than in the central portion.

As described above, when the read gate length D ₂ is made larger in the horizontal peripheral portion of the solid-state image pickup element than in the central portion, the read gate length D ₂ is set from the horizontal central portion of the solid-state image pickup element to the peripheral portion. It is preferable to gradually increase the size as it goes to the section.

Here, the read gate length D ₂ is gradually increased from the central portion in the horizontal direction of the solid-state image pickup device to the peripheral portion, that is, the read gate length D _{2 in the} peripheral portion is larger than the read gate length D _{2 in the} peripheral portion. _This is because if the value of ₂ is large, the blooming resistance of the peripheral portion is large, and if the blooming resistance of the peripheral portion is large, it is sufficient, and the read gate length D ₂ is not necessarily the peripheral portion from the central portion in the horizontal direction of the solid-state imaging device. It is not necessary that the read gate length D _{2 in the} peripheral portion be larger than the read gate length D _{2 in the} central portion, as long as the read gate length D _{2 in the} central portion is larger than the read gate length D ₂ in the central portion. The way of change changes gradually, that is, it changes gently, the way of increasing is larger in the peripheral part and the amount of increase is gradually smaller as going to the center part, and in the center part it is blue on the contrary Reduced ring withstanding capability, since blooming capability through the horizontal full width of the solid-state imaging device becomes substantially equal, preferably it is readout gate length D ₂ keep sequentially increased as it goes from the central portion to the peripheral portion.

Further, when increasing the read gate length D ₂ of the peripheral portion than the read gate length D ₂ of the central portion in the horizontal direction, the read gate length D _2, the same length Satoshi one by one by several or several tens of In actual design, it is preferable to adopt a method of gradually increasing the size from the central part to the peripheral part.

Here, the read gate length D ₂ of the solid-state image pickup device is made to be the same length every several lines or every several tens lines, and is gradually increased from the central part toward the peripheral part.
Read gate length D ₂ of the peripheral portion than the read gate length D ₂ of the central portion is because blooming capability at the peripheral portion if the larger is large, blooming capability of the peripheral portion is a sufficient if a large, It is not always necessary to set the same length for every several lines or several dozen lines, and to increase the read gate length D in the central part stepwise from the central part to the peripheral part.
_Although the read gate length D ₂ in the peripheral portion may be set larger than ₂ , the read gate length of the actual solid-state image sensor is very large, so that it is easy to design in the actual design, and the total length of the solid-state image sensor in the horizontal direction is reduced. For the reason that the blooming tolerances are substantially the same, it is preferable to set the read gate length D ₂ to the same length by several lines or tens of lines, and gradually increase from the central part toward the peripheral part.

In the solid-state image pickup device to which the present invention is applied, the phenomenon as shown in FIG. 9 in the case where the read gate length is the same at all positions in the horizontal direction of the solid-state image pickup device, that is, the blooming resistance is horizontal. The phenomenon that the peripheral portion is smaller than the central portion is improved, and the blooming resistance of the peripheral portion is increased.

FIG. 4 shows still another example of the solid-state image pickup device to which the present invention is applied, that is, the transfer channel width D of the vertical transfer unit 2.
₁ sequentially increases from the horizontal peripheral portion to the central portion of the solid-state image sensor, and the read gate length D ₂ of the solid-state image sensor sequentially increases from the horizontal central portion to the peripheral portion. Under such conditions, the change state of the transfer channel width D ₁ and the read gate length D ₂ for each position in the horizontal direction when D ₁ + D ₂ is kept constant in order to maintain the pixel pitch is shown. It is a graph. Figure 4
In the figure, the code F indicates the change state of the transfer channel width D ₁ , and the code G
Shows the change state of the read gate length D ₂ , respectively, and the transfer channel width D ₁ of the vertical transfer unit 2 is gradually increased from the horizontal peripheral portion to the central portion of the solid-state imaging device, and By setting D ₁ + D ₂ constant under the condition that the read gate length D ₂ of the image pickup device is gradually increased from the central portion in the horizontal direction toward the peripheral portion, the pixel pitch of the solid-state image pickup element is kept constant. While maintaining
The amount of charge handled by the vertical transfer unit 2 and the blooming resistance are constant at any position in the horizontal direction.

In the solid-state image pickup device to which the present invention is applied, as shown in FIG.
As can be seen from the amount of charge handled in each horizontal position of the solid-state image sensor shown in FIG. 6 and the blooming tolerance of each horizontal position of the solid-state image sensor shown in FIG. The amount of electric charges handled by the vertical transfer unit is larger in the vicinity of the central portion as compared with the amount of electric charges handled by the vertical transfer unit of the conventional structure shown by symbol I in FIG. 5, and the blooming resistance is indicated by symbol J in FIG. The blooming resistance in the case of applying the present invention shown in FIG. 6 is increased in the vicinity of the peripheral portion as compared with the blooming resistance of the conventional structure shown by the symbol K in FIG. In this way, both the handling charge amount and the blooming resistance amount are improved.

[0027]

As described above, according to the present invention,
The vertical transfer section has a channel width that is larger in the central part in the horizontal direction and smaller in the peripheral part, and due to the influence of the propagation delay of the vertical transfer clock, the amount of charge handled becomes substantially constant at any position in the horizontal direction. Compared with, the handling charge amount increases and the sensitivity improves. In addition, due to the configuration that the read gate length from the light receiving part is small near the center of the screen and large near the screen, and due to the influence of the propagation delay of the vertical transfer clock, the blooming resistance becomes substantially constant at any position in the horizontal direction.
The blooming resistance is higher than that of the conventional structure.

[Brief description of drawings]

FIG. 1 is a transfer channel width D of a vertical transfer unit of a solid-state image sensor.
It is a graph which shows the relationship between ₁ and the amount of electric charges handled.

FIG. 2 is a graph showing a relationship between a read gate length D ₂ of a solid-state imaging device and blooming resistance.

FIG. 3 is a block diagram showing an example of a solid-state image sensor to which the present invention is applied.

FIG. 4 is a graph showing changes in transfer channel width D ₁ and read gate length D ₂ for each position in the horizontal direction of still another example of the solid-state imaging device to which the present invention is applied.

FIG. 5 is a graph showing the amount of charge handled for each horizontal position of the solid-state image sensor to which the present invention is applied.

FIG. 6 is a graph showing blooming resistance for each position in the horizontal direction of the solid-state image sensor to which the present invention is applied.

FIG. 7 is a block diagram of a conventional solid-state image sensor.

FIG. 8 is a graph showing the state of changes in the input waveform from the vertical transfer clock of the conventional solid-state imaging device depending on the location.

FIG. 9 is a graph showing a relationship between a handled charge amount and a blooming resistance amount for each horizontal position of a conventional solid-state image sensor.

[Explanation of symbols]

1 Light receiving part 2 Vertical transfer section 3 Horizontal transfer section 4 Charge-voltage converter 5 Output section 6 Vertical transfer clock

Claims (7)

[Claims] 1. An image pickup unit having a plurality of light receiving units arranged in a matrix and having a vertical transfer unit for transferring charges from each light receiving unit provided for each vertical column of the light receiving units; and a charge from the vertical transfer unit. In the solid-state imaging device having a horizontal transfer section for transferring the transferred charges in the horizontal direction and an output section for outputting the transferred charges from the horizontal transfer section, a vertical transfer section at a central portion in the horizontal direction. The transfer channel width of the solid state image pickup device is larger than the transfer channel width of the vertical transfer section in the peripheral portion. 2. The solid-state image pickup device according to claim 1, wherein the transfer channel width of the vertical transfer portion is gradually increased from the peripheral portion toward the central portion in the horizontal direction. 3. The solid-state image pickup device according to claim 1, wherein the transfer channel width of the vertical transfer unit is gradually increased from the peripheral portion to the central portion in the horizontal direction. 4. The solid-state image pickup device according to claim 1, wherein the read gate length of the peripheral portion is made larger than the read gate length of the central portion in the horizontal direction. 5. The solid-state imaging device according to claim 4, wherein the read gate length is gradually increased from the central portion in the horizontal direction toward the peripheral portion. 6. The solid-state imaging device according to claim 4, wherein the read gate length is increased stepwise from the central portion in the horizontal direction to the peripheral portion. 7. The size of the transfer channel width of the vertical transfer unit plus the read gate length is constant at any position in the horizontal direction. Item 7. The solid-state image sensor according to item.