JPH07231082A - Solid-state image pick-up device - Google Patents

Abstract

PURPOSE:To reduce the amount of saturation signal at a vertical transfer region consisting of CCD and to reduce the occupied area of the vertical transfer region consisting of the CCD by forming a horizontal or vertical separation region or an overflow drain provided at the periphery of a photoelectric conversion region. CONSTITUTION:A plurality of photoelectric conversion regions 1 are provided in a matrix. A vertical separation region 2 is laid out between the vertical directions of the photoelectric conversion region 1. Also, a vertical transfer region 3 consisting of a CCD is laid out along the row direction of the photoelectric conversion region 1. namely the vertical direction and via a gate region 5. Then, a horizontal separation region 4 is laid out continuously in the vertical direction between the vertical transfer region 3 and the photoelectric conversion region 1 along the vertical transfer region 3.

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 suitable for use in a video camera or the like.

[0002]

2. Description of the Related Art FIG. 7 is a plan view of a main part of a solid-state image pickup device used in a conventional video camera. Referring to FIG. 7, 1 is a plurality of matrix elements, for example 41
Photoelectric conversion area where millions are arranged, 2 is this photoelectric conversion area 1
The vertical separation regions 3 arranged between the vertical regions of the photoelectric conversion regions 1 are arranged in the column direction of the photoelectric conversion regions 1, that is, in the vertical direction, and the gate regions 5 are formed.
A vertical transfer region 4 composed of a CCD arranged via a horizontal separation region 4 arranged continuously along the vertical transfer region 3 in the vertical direction between the vertical transfer region 3 and the photoelectric conversion region 1. Show.

FIG. 8 is a sectional view taken along the line AA in the horizontal direction of FIG. 7, and FIG. 9 is a sectional view taken along the line BB of the vertical direction in FIG. An example of the conventional solid-state imaging device will be further described with reference to FIGS. 8 and 9.

[0004] In FIGS. 8 and 9, 6 denotes an N-type semiconductor substrate, over the entire region on the N-type semiconductor substrate 6 P ^-
A P-type well 7 having a concentration is provided. In the photoelectric conversion region 1 shown in FIG. 7, an N-type region 1N for accumulating charges according to the intensity of light is formed on the P-type well 7 and the N-type region 1 is formed.
A P-type region 1P having a P ⁺ concentration is formed on N.

In this example, a vertical overflow drain is formed, and the potential in the depth direction of this photoelectric conversion region 1 is P on the surface as shown by a curve 8 in FIG.
In the N-type region 1N, which is a charge storage region, lower than the type region 1P to a minimum value (φ _sens ) and becomes maximum in the P-type well 7,
N forming a drain and forming a barrier 8a in the depth direction
Type semiconductor substrate 6 such that the potential drops to a predetermined potential,
When the accumulated charges 9 exceed the barrier 8a in the depth direction, the exceeded charges flow out to the N-type semiconductor substrate 6 forming the drain.

Further, as shown in FIG. 9, the vertical isolation region 2 arranged between the photoelectric conversion regions 1 in the vertical direction is formed by forming a P-type P-type region 2P on the P-type well 7. As shown by the curve 10 in FIG. 10, the potential of the vertical isolation region 2 in the depth direction is relatively higher in the P-type region 2P and the P-type well 7 than in the surface, and then sharply decreases in the N-type semiconductor substrate 6. The photoelectric conversion regions 1 are vertically separated from each other in terms of electric charge.

Further, as shown in FIG. 8, the vertical transfer region 3 composed of CCDs arranged in the column direction of the photoelectric conversion regions 1, that is, in the vertical direction, and via the gate region 5, has the P-type well 7 formed in the vertical direction. A P-type region 3P having a P width and having a predetermined width is formed on the N-type region 3N having an N ⁺ concentration on the P-type region 3P.

Further, P on the N-type region 5N with the gate region 5 is formed an N-type region 5N the same concentration as the N-type semiconductor substrate 6 on the P-type well 7 ^- forming a concentration of P-type region 5P By supplying a predetermined voltage to the electrode provided on the gate region 5, the signal charge accumulated in the N-type region 1N of the photoelectric conversion region 1 is passed through the gate region 5 to the vertical transfer region 3 To the N-type region 3N.

A horizontal separation region 4 continuously arranged in the vertical direction between the vertical transfer region 3 and the photoelectric conversion region 1 along the vertical transfer region 3 has a predetermined width on the P-type well 7. An N-type region 4N having the same concentration as that of the N-type semiconductor substrate 6 is formed, and a P-type P-type region 4P having a P concentration is formed on the N-type region 4N.
Are formed, and the horizontal direction of the photoelectric conversion region 1 is electrically separated.

In such a solid-state image sensor as described above,
Signal charges accumulated by photoelectric conversion by a plurality of photoelectric conversion regions 1 are sent to a vertical transfer region 3 constituted by a CCD at a predetermined timing, sequentially transferred in the vertical direction by the vertical transfer region 3, and constituted by a CCD (not shown). The video signal is transferred to the horizontal transfer area, and the video signal is taken out from the output terminal of the horizontal transfer area.

[0011]

In the photoelectric conversion region 1 of such a conventional solid-state image pickup device, photoelectrically accumulated charges 9 are accumulated up to the depth direction barrier 8a. The amount of charges accumulated up to the depth direction barrier 8a is called a saturation signal amount Qs, and this saturation signal amount Qs is controlled by the potential φOFB of the depth direction barrier 8a.

In the conventional vertical overflow drain of the photoelectric conversion region 1, when signal charges are accumulated in the N-type region 1N of the photoelectric conversion region 1, the curve 8 of FIG. 10 is affected by the accumulated signal charges. Since the barrier 8a in the depth direction becomes shallow and the saturation signal amount Qs becomes large, the light amount-output signal characteristic of the photoelectric conversion region 1 is constant at the saturation signal amount Qs as shown by the curve b as shown in FIG. The output signal that should reach the level increases as shown by the curve a.

Therefore, it is necessary to ensure that the saturation signal amount Qv of the vertical transfer area 3 composed of CCD for transferring the signal charge can be accumulated and transferred up to the output signal Qknee in the case of a large light quantity c. There is an inconvenience that the occupied area becomes so large.

In view of the above point, the present invention has an object to make it possible to reduce the occupied area of the vertical transfer region composed of this CCD.

[0015]

The solid-state image pickup device of the present invention is, for example, as shown in FIG. 1, a plurality of photoelectric conversion regions 1 and horizontal and vertical separation regions 4 and 2 provided around the plurality of photoelectric conversion regions 1. And a vertical transfer region 3 for vertically transferring the signal charges from the photoelectric conversion region 1, in the solid-state image pickup device, an overflow drain is formed in the horizontal or vertical separation region 4 or 2.

[0016]

According to the present invention, since the overflow drain is formed in the horizontal or vertical separation region 4 or 2 provided around the photoelectric conversion region 1, even if the signal charges are accumulated in the photoelectric conversion region 1, The saturation signal amount Qs is constant,
It is possible to reduce the saturation signal amount Qv of the vertical transfer area 3 including the CCD, and reduce the occupied area of the vertical transfer area 3 including the CCD.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the solid-state image pickup device of the present invention will be described below with reference to FIGS. 1, 2 and 7. 1 and 2, parts corresponding to those in FIGS. 9 and 8 are designated by the same reference numerals. In this example, an overflow drain is formed below the vertical isolation region 2.

A plan view of the main part of the solid-state image sensor of this example is shown in FIG.
Similarly, a plurality of, for example, 410,000 photoelectric conversion regions 1 are provided in a matrix, and vertical separation regions 2 are arranged between the photoelectric conversion regions 1 in the vertical direction. Further, a vertical transfer area 3 composed of a CCD is arranged along the column direction, that is, the vertical direction of the photoelectric conversion area 1 and via a gate area 5, and along the vertical transfer area 3, the vertical transfer area 3 and the photoelectric conversion area 3 are arranged. 1
A horizontal separation region 4 is continuously arranged in the vertical direction between and.

2 which is a sectional view taken along the line AA in the horizontal direction of FIG. 7 is substantially the same as that shown in FIG. 8, but in this embodiment, a sectional view taken along the line BB in the vertical direction is constructed as shown in FIG. To do. The solid-state image sensor of this example will be described with reference to FIGS. 1 and 2.

In this example, as shown in FIGS. 1 and 2, N
Except for the portion corresponding to the vertical separation region 2 on the type semiconductor substrate 6 P ^- forming a concentration of P-type well 7a. In this case P
The impurity concentration of the type well 7a is set to be higher than that of the conventional P-type well 7.

Further, as shown in FIGS. 1 and 2, in the photoelectric conversion region 1 shown in FIG. 7, an N-type region 1N for accumulating electric charges according to the intensity of light is formed on the P-type well 7a. The P-type region 1P having a P ⁺ concentration is formed on the N-type region 1N.

The potential in the depth direction of the photoelectric conversion region 1 is the P-type region 1P on the surface as shown by the curve 11 in FIG.
Further, in the N-type region 1N which is the charge storage region, it is lowered to the minimum value (φ _sens ) and is maximized in the P-type well 7a to form the barrier 11a in the depth direction to form the drain N.
In the semiconductor substrate 6, the potential is lowered to a predetermined potential (determined by the bias voltage).

In this example, the photoelectric conversion region 1
As shown in FIG. 1, the vertical separation regions 2 arranged between the vertical directions of the above are formed by forming P-type regions 2P of P concentration on the N-type semiconductor substrate 6. The potential of the vertical isolation region 2 in the depth direction gradually decreases from the surface P-type region 2P as shown by the curve 12 in FIG. 3, and then drops to a predetermined potential (determined by the bias voltage) on the N-type semiconductor substrate 6. Like that.

In this case, the potential curve 12 in the depth direction of the vertical separation region 2 and the potential curve 11 in the depth direction of the photoelectric conversion region 1 are the descending part of the curve 12 and the curve 1.
1 has an intersection 13 with the rising portion of 1, and since this intersection 13 is lower than the barrier 11a in the depth direction of the N-type region 1N which is the charge storage region, this intersection 13 is the charge storage region N.
When the accumulated charge 9 of the N-type region 1N exceeds the potential of the intersection 13, that is, the barrier, the excess charge passes through the lateral P-type region 2P as indicated by an arrow in FIG. It flows out to the N-type semiconductor substrate 6 forming the drain. That is, in this example, the vertical drain region 2 constitutes an overflow drain.

Further, in this case, since the curve 12 does not change even if charges are accumulated in the N-type region 1N of the photoelectric conversion region 1, the potential at the intersection 13 does not change.

The column direction of the photoelectric conversion regions 1, that is, the vertical direction
Consisting of CCDs arranged along and along the gate region 5.
The vertical transfer area 3 shown in FIG.
On the P-type well 7a, a P-type region 3P having a P concentration of a predetermined width is formed.
And form N on it ⁺Concentration N-type region 3N shape
It was made.

Further, the gate region 5 is the P-type well 7a.
An N-type region 5N having the same concentration as that of the N-type semiconductor substrate 6 is formed thereon, and a P-type P-type region 5P having a P ⁻ concentration is formed on the N-type region 5N.
By supplying a predetermined voltage to the electrode provided on the gate region 5, the signal charges accumulated in the N-type region 1N of the photoelectric conversion region 1 are vertically transferred through the gate region 5. It is designed to be sent to the N-type region 3N of the region 3.

Along the vertical transfer region 3, the horizontal separation region 4 continuously arranged in the vertical direction between the vertical transfer region 3 and the photoelectric conversion region 1 has a predetermined width on the P-type well 7a. The N-type region 4N having the same concentration as that of the N-type semiconductor substrate 6 and the P-type P-type region 4P having the P concentration are formed on the N-type region 4N to electrically charge the photoelectric conversion region 1 in the horizontal direction. Make it separate.

In the above-described solid-state image pickup device of the present example, the vertical transfer region 3 formed by the CCD at a predetermined timing is used for photoelectrically converting signal charges accumulated by photoelectric conversion by the plurality of photoelectric conversion regions 1.
To the horizontal transfer area composed of a CCD (not shown), and the video signal is taken out from the output end of this horizontal transfer area.

The photoelectric conversion area 1 of the solid-state image sensor of this example.
In, the photoelectrically accumulated charges 9 are accumulated up to the barrier determined by the intersection 13. Here, the charge amount accumulated up to the potential at the intersection 13 is referred to as a saturation signal amount Qs, and the saturation signal amount Qs is controlled by the potential at the intersection 13.

The potential at the intersection 13 according to this example does not change even if signal charges are accumulated in the N-type region 1N of the photoelectric conversion region 1, and the output signal amount (Qknee) is large even when the light amount is large. Vertical transfer area 3
The saturation signal amount Qv can be reduced, and the occupied area of the vertical transfer region 3 can be reduced.

Therefore, in the solid-state image pickup device having the same area, the area of the photoelectric conversion region 1 can be increased by the reduction of the occupied area of the vertical transfer region 3 made of CCD, and the sensitivity can be improved.

FIGS. 4 and 5 are vertical sectional views taken along the line BB in FIG. 7 of another embodiment in which the overflow drain according to the present invention is applied to the vertical isolation region 2. Also in the examples of FIGS. 4 and 5, the plan view and the sectional view taken along the line AA of the main part are the same as those in FIGS. 7 and 2, respectively. In order to eliminate the possibility that the electrons overflowing from the photoelectric conversion region 1 of the portion in FIG. 4 and FIG. 5 in the above-described example of FIG. The measures have been taken.

To explain each of FIGS. 4 and 5, parts corresponding to those of FIG. 1 are designated by the same reference numerals. Fig In 4 cases on the N-type semiconductor substrate 6 in example FIG P ^- concentration of the P-type well 7a formed is not part of the vertical isolation region 2
And the overflow drain is formed in the portion of the vertical isolation region 2 where the P-type well 7a is not formed as described above. Others are the same as the above-mentioned example.

In the solid-state image pickup device according to the example of FIG. 4, on the side where the P-type well 7a of the vertical isolation region 2 is not formed, the intersection 13 of the curves 11 and 12 of FIG.
The electric charges that have exceeded the barrier due to the potential of 6 overflow and have the same effect as in the example of FIG. 1 and the side of the vertical isolation region 2 where the P-type well 7a is formed has the function of element isolation as in the conventional case. The above-mentioned inconvenience can be improved.

Further P on N-type semiconductor substrate 6 in an example figure 5 example ^- a portion that does not form a P-type well 7a concentration and every other vertical isolation region 2, the formation of the P-type well 7a The vertical separation region 2 which is not formed constitutes the overflow drain as described above, and the vertical separation region 2 in which the P-type well 7a is formed is the same as the conventional one. Others are the same as the above-mentioned example.

In the solid-state image pickup device according to the example of FIG. 5 in which the P-type well 7a of the vertical separation region 2 is not formed, the intersection 13 of the curves 11 and 12 shown in FIG.
The charges that have exceeded the barrier due to the potential of 6 overflow and have the same effect as in the example of FIG. 1 and the P-type well 7a of the vertical isolation region 2 has the function of element isolation as in the conventional case. The above-mentioned inconvenience can be improved.

FIG. 6 shows an example in which an overflow drain is formed under the horizontal separation region 4. This FIG. 6 is a sectional view taken along the line AA in the horizontal direction of the plan view of the main part of the solid-state image pickup device as shown in FIG. Show. The top view of the principal part of this example and B of the perpendicular direction
The sectional view taken along line B is as shown in FIGS. 7 and 9. In FIG. 6, parts corresponding to those in FIG. 8 are designated by the same reference numerals.

In the example of FIG. 6, the P-type well 7 of P ⁻ concentration on the N-type semiconductor substrate 6 in FIG. 8 is formed in all parts except the half on the photoelectric conversion region 1 side corresponding to the horizontal isolation region 4. To do. In this case, the overflow drain is formed in the portion of the horizontal separation region 4 where the P-type well 7 is not formed as described above. Others are configured similarly to the conventional example.

In the solid-state image pickup device according to the example of FIG. 6, as in the case where the overflow drain is formed in the vertical separation region 2 on the side where the P-type well 7 of the horizontal separation region 4 is not formed, the N of the photoelectric conversion region 1 is formed. Charges that exceed the barrier due to the potential at the intersection 13 of the curves 11 and 12 of the mold region 1N shown in FIG. 3 overflow, and the same effect as the example of FIG. 1 is obtained. Further, in this example, it is also effective in reducing smear between the photoelectric conversion regions 1 (between pixels).

The present invention is not limited to the above-described embodiments, and it goes without saying that various other configurations can be adopted without departing from the gist of the present invention.

[0042]

According to the present invention, the overflow drain is formed in the horizontal or vertical separation region around the photoelectric conversion region. Therefore, even if charges are accumulated in this photoelectric conversion region, the saturation signal amount Qs is There is an advantage that the output signal amount (Qknee) can be reduced even when the light amount is large without changing, the saturation signal amount Qv of the vertical transfer region can be reduced, and the occupied area of the vertical transfer region can be reduced.

Therefore, according to the present invention, in the solid-state image pickup device having the same area, the area of this photoelectric conversion region can be increased by the reduction of the occupied area of the vertical transfer region formed of CCD, and the sensitivity can be improved accordingly. You can

Further, according to the present invention, there is an advantage that smear between pixels can be reduced.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a main part of an embodiment of a solid-state imaging device of the present invention.

FIG. 2 is a horizontal cross-sectional view of a main part of an embodiment of the solid-state imaging device of the present invention.

FIG. 3 is a diagram for explaining the present invention.

FIG. 4 is a vertical sectional view of a main part of another embodiment of the present invention.

FIG. 5 is a vertical cross-sectional view of a main part of another embodiment of the present invention.

FIG. 6 is a horizontal sectional view of a main part of another embodiment of the present invention.

FIG. 7 is a plan view of a main part of a solid-state image sensor.

FIG. 8 is a horizontal cross-sectional view of a main part of a solid-state image sensor.

FIG. 9 is a vertical cross-sectional view of a main part of a solid-state image sensor.

FIG. 10 is a diagram used for explaining a conventional solid-state imaging device.

FIG. 11 is a diagram for explaining a solid-state image sensor.

[Explanation of symbols]

 1 photoelectric conversion region 1N N-type region 2 vertical separation region 2P P-type region 3 vertical transfer region 4 horizontal separation region 5 gate region 6 N-type semiconductor substrate 7, 7a P-type well 9 accumulated charge 11 in the depth direction of the photoelectric conversion region Potential curve 12 Potential curve in the depth direction of vertical separation area 13 Intersection point

Claims (1)

[Claims] 1. A plurality of photoelectric conversion regions, horizontal and vertical separation regions provided around the plurality of photoelectric conversion regions, and a vertical transfer region for vertically transferring signal charges from the photoelectric conversion regions. A solid-state image sensor having the above, wherein an overflow drain is formed in the horizontal or vertical separation region.