JP2000150852A - Solid state imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress increase in a saturated signal amount at excessive light- amount incident. SOLUTION: A second conductive type well region 11 formed on a first conductive type semiconductor substrate 10, a light receiving part where a plurality of light receiving elements 1 comprising a first conductive type photoelectric conversion region IN formed on the well region 11 and a second conductive type positive-hole charge storage region 1P accumulated on the photoelectric conversion region IN are provided in matrix, a plurality of lines of vertical shift registers 3 which transfer the signal charge read out of the plurality of light receiving elements 1 in vertical direction, a horizontal shift register which transfers the signal charge from the plurality of lines of vertical shift registers 3 in horizontal direction, and a first channel top region 4 provided, in vertical direction, between the vertical shift register 3 and the light receiving element 1, are provided. Here, along the first channel stop region 4, a second channel stop region 4a is formed at a position deeper than the first channel stop region 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a solid-state imaging device suitable for use in a video camera or the like.

[0002]

2. Description of the Related Art Generally, a video camera uses an interline transfer type CCD solid-state imaging device as shown in FIG. Referring to FIG. 3, FIG. 3 is a plan view of an interline transfer type CCD solid-state imaging device.

In FIG. 3, reference numeral 1 denotes a light receiving element in which a plurality of, for example, 410,000 light receiving elements are arranged in a matrix, reference numeral 2 denotes a vertical separation region separating the light receiving elements 1 in a vertical direction, and reference numeral 3 denotes a light receiving element 1 A vertical shift register 4 composed of CCDs arranged in a plurality of columns along the column direction, that is, the vertical direction, and
The horizontal separation area, which is a channel stop area continuously arranged in the vertical direction between the vertical shift register 3 and the light receiving element 1, is shown.

In such an interline transfer type CCD solid-state image pickup device, signal charges read from each light receiving element 1 are transferred vertically by a vertical shift register 3 and further transferred horizontally by a horizontal shift register 6. At the end of the horizontal shift register 6, there is provided a signal charge detection circuit 7 which is an output circuit comprising a floating diffusion amplifier (FDA) and the like. And output it.

FIG. 4 is a partially enlarged view of the CCD solid-state imaging device of the interline transfer system shown in FIG. 3, FIG. 5 is a cross-sectional view taken along the line XX of FIG. 4, and FIG. 4 is a vertical sectional view taken along line YY of FIG. An example of a conventional solid-state imaging device will be further described with reference to FIGS.

In FIGS. 5 and 6, reference numeral 10 denotes an N-type semiconductor substrate made of silicon.
A P-type well 11 having a P impurity concentration is provided over the entire upper region. The light receiving element 1 shown in FIG. 3 has an impurity concentration of N for accumulating signal charges corresponding to the light intensity on the P-type well 11.
⁺ Laminated on the photoelectric conversion region on 1N with N-type region provided a photoelectric conversion region 1N consisting of, positive impurity concentration to accumulate holes corresponding to the intensity of the light consists of P-type region of the P ⁺⁺ The hole accumulation region 1P is formed.

In the light receiving element 1 shown in FIGS. 5 and 6, a vertical overflow drain is formed. The potential of the light receiving element 1 in the depth direction is, as shown by a curve 20 in FIG. The potential is relatively high and constant in the hole accumulation region 1P of the type region, and the potential is lowered from this to fall to a local minimum value at substantially the center of the photoelectric conversion region 1N of the N-type region which is the signal charge accumulation region. The potential rises, reaches a maximum in the P-type well 11, forms a barrier 20a in the depth direction, and then decreases, and the potential drops to a predetermined potential in the N-type semiconductor substrate 10 constituting the drain. Charge 21
When the current exceeds the barrier 20a in the depth direction, the excess charge flows out to the N-type semiconductor substrate 10 constituting the drain.

The vertical isolation region 2 arranged between the light receiving elements 1 in the vertical direction is formed by an extension region of the P-type well 11 as shown in FIG.

Further, as shown in FIG. 5, a vertical shift register 3 composed of a CCD arranged along the column direction, that is, the vertical direction of the light receiving element 1 and via the gate region 5 is provided with the P-type well 11 along the vertical direction. The impurity concentration of a predetermined width is P
A P-type region 3P for suppressing ⁺ smear is formed, and a signal charge transfer region 3N having an impurity concentration of N ⁺ is formed thereon.

Along this vertical shift register 3,
As shown in FIG. 5, the horizontal separation region 4 which is a channel stop region continuously arranged in the vertical direction between the vertical shift register 3 and the light receiving element 1 has an impurity concentration of P ⁺ on the P-type well 11. Are formed.
In FIGS. 4, 5, and 6, reference numerals 13 and 14 are transfer electrodes, respectively.

[0011] The solid-state imaging device of the conventional interline transfer system is constructed as described above, for example, when the incident excessive amount in the light receiving element 1, and the saturation signal amount Q _S or more signal charges of the light receiving element 1 Therefore, as shown in FIG. 7, the excess signal charge exceeding the saturation signal amount Q _S passes through the barrier 20 a in the depth direction of the P-type well 11 and is swept away to the N-type semiconductor substrate 10.

Further, holes generated by light incident on the light receiving element 1 pass through a horizontal separation area 4 which is a channel stop area shown in FIG. The current flows to the ground via the grounded portion 15 in the peripheral portion of the (area).

FIG. 8 and FIG. 9 schematically show the flow of the excess signal charge as route B.
Is shown as route A. FIG. 8 is a schematic plan view, and FIG. 9 is a schematic sectional view.

[0014]

In this conventional CCD solid-state imaging device, as shown in FIG. 3, the horizontal separation region 4 which is a channel stop region has a resistance value because the width of the P ⁺ impurity region which forms it is small and long. Therefore, when an excessive amount of light is incident on the light receiving element 1, a potential fluctuation occurs due to an excessive hole current in the horizontal separation region 4 which is a channel stop region, and the ground level rises.

[0015] Therefore, in the depth direction as shown in curve 22 the barrier becomes shallow increased saturation signal amount Q _S of FIG. 7 (knee component increases), N-type semiconductor substrate operating characteristics of the light receiving element 1 is changed The signal charge amount of the light receiving element 1 abnormally increases without being swept away to 10.

Therefore, when the signal charges stored in the light receiving element 1 are read out to the vertical shift register 3 and the signal charges are equal to or larger than the maximum handled charge amount in the vertical shift register 3, the signal charges overflow. There is a disadvantage that the phenomenon occurs.

A grounded portion 1 around the light receiving portion
The portion distant from the 5 flow hole current (leakage of holes) of the light receiving element 1 the resistance value of the channel stop region 4 increases is slow, the saturation signal amount Q _s is a disadvantage that variation out by the light receiving portion Was.

[0018] The present invention has been made in view of the points mow斯intended to be able to suppress an increase in the saturation signal amount Q _s in excessive quantity incident.

[0019]

According to the present invention, there is provided a solid-state imaging device comprising:
A second conductivity type well region formed on the first conductivity type semiconductor substrate; a first conductivity type photoelectric conversion region formed on the well region; and a second conductivity type stacked on the photoelectric conversion region. A light receiving section in which a plurality of light receiving elements each formed of a conductive type hole charge storage region are arranged in a matrix; and a plurality of columns of vertical shift registers for vertically transferring signal charges read from the plurality of light receiving elements. A horizontal shift register for transferring signal charges from the plurality of columns of vertical shift registers in the horizontal direction, and a first channel stop region provided vertically between the vertical shift registers and the light receiving elements. In the solid-state imaging device, a second channel stop region is formed along the first channel stop region and deeper than the first channel stop region. It is.

According to the present invention, since the second channel stop region is formed along the first channel stop region and deeper than the first channel stop region, the second channel stop region moves to the overflow barrier portion, that is, the well region. The holes flow through the second channel stop region and the first channel stop region to the ground through the grounded portion in the periphery of the light receiving unit, and thereby the saturation signal amount Q in the case of excessive light incident. The increase in _s can be suppressed.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a solid-state imaging device according to the present invention will be described below with reference to FIGS. 1, 2, 3 and 4. In FIG. 1, portions corresponding to FIG. 5 are denoted by the same reference numerals.

The plan view of the solid-state image pickup device of this embodiment is the same as that of FIG. 3, and a plurality of, for example, 410,000 light receiving elements 1 are provided in a matrix, and a vertical separation region 2 is provided between the light receiving elements 1 in the vertical direction. Distribute. A plurality of columns of vertical shift registers 3 composed of CCDs are arranged along the column direction, that is, the vertical direction of the light receiving element 1 and through a gate region 5. A channel stop area, that is, a horizontal separation area 4 is continuously arranged in the vertical direction between the element 1.

The partially enlarged view of this embodiment is also the same as FIG. 4, and the vertical sectional view taken along the line Y--Y of FIG. 4 according to this embodiment is substantially the same as that of FIG. The sectional view taken along the line XX is configured as shown in FIG. The solid-state imaging device according to the present embodiment will be described with reference to FIGS.

In this embodiment, as shown in FIGS. 1 and 6, a P-type well 11 having an impurity concentration of P is provided on an N-type semiconductor substrate 10 made of silicon over the entire region. The light receiving element 1 is provided with a photoelectric conversion region 1N composed of an N-type region having an impurity concentration of N ⁺ for accumulating signal charges corresponding to the intensity of light on the P-type well 11 and stacked on the photoelectric conversion region 1N. The concentration of the impurity that accumulates holes according to the light intensity is P ⁺⁺
A hole accumulation region 1P composed of a mold region is formed.

Each of the light receiving elements 1 of FIGS. 1 and 6 forms a vertical overflow drain, and the potential of the light receiving element 1 in the depth direction is represented by a curve 2 in FIG.
As shown in FIG. 0, the potential is relatively high and constant in the hole accumulation region 1P of the P-type region on the surface, and then drops sharply in the photoelectric conversion region 1N of the N-type region, which is the signal charge accumulation region. The potential becomes a minimum value in the middle portion of the region 1N, and then this potential rises and becomes a maximum value in the P-type well 11 to form a barrier 20a in the depth direction. The potential of the semiconductor substrate 10 is lowered to a predetermined potential.
When it exceeds a, the excess charge is swept away by the N-type semiconductor substrate 10 constituting the drain.

As shown in FIG. 1, the vertical shift register 3 composed of a CCD arranged along the column direction, that is, the vertical direction of the light receiving element 1 and via the gate region 5, has the P-type well 11 along the vertical direction. The impurity concentration of a predetermined width is P
A P-type region 3P for suppressing ⁺ smear is formed, and a signal charge transfer region 3N having an impurity concentration of N ⁺ is formed thereon.

Along this vertical shift register 3,
As shown in FIG. 1, the horizontal separation region 4 which is a channel stop region continuously arranged in the vertical direction between the vertical shift register 3 and the light receiving element 1 has an impurity concentration of P ⁺ on the P-type well 11. Of P-type regions.

In this embodiment, as shown in FIG. 1, along the channel stop region 4, a P-type well having an impurity concentration of P ⁺ is formed in a P-type well 11 below the channel stop region 4 in the depth direction. A channel stop region 4a similar to the channel stop region 4 is formed.

In FIG. 1, FIG. 3, FIG. 4, and FIG.
Reference numerals 3 and 14 denote transfer electrodes, for example, polysilicon 2
It is formed by a layer structure.

According to the present embodiment, the channel stop area 4a is formed at a position deeper than the channel stop area 4 along the channel stop area 4, so that the channel stop area 4a is located outside the route A and the route B shown in FIGS. As shown in FIG. 2 as a route C, an overflow barrier portion;
That is, the holes moved to the P-type well 11 pass through the channel stop region 4a → the grounded portion 15 around the light receiving portion through the channel stop region 4.
Via stream to the ground, thereby making it possible to suppress an increase of the saturation signal amount Q _s in excessive quantity incident.

[0031] Therefore, even if the incident excessive amount in the light receiving element 1, it is possible to suppress the fluctuation of the ground level, there is a benefit that can suppress variation in the saturation signal amount Q _s of the light-receiving element 1.

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

[0033]

According to the present invention, even if the incident excessive amount to the light receiving element, it is possible to suppress the fluctuation of the ground level, it is possible to suppress the increase of the saturation signal amount Q _S of the light receiving element in an excessive amount incident There are benefits that can be done.

[Brief description of the drawings]

FIG. 1 is a horizontal sectional view of a main part of an example of an embodiment of a solid-state imaging device according to the present invention.

FIG. 2 is a schematic sectional view for explaining the present invention.

FIG. 3 is a plan view of an example of a solid-state imaging device.

FIG. 4 is a partially enlarged view of FIG. 3;

FIG. 5 is a horizontal sectional view of a main part of an example of a conventional solid-state imaging device.

FIG. 6 is a vertical sectional view of a main part of an example of a conventional solid-state imaging device.

FIG. 7 is a diagram for describing the present invention.

FIG. 8 is a schematic plan view for explaining an example of a conventional solid-state imaging device.

FIG. 9 is a schematic cross-sectional view for explaining an example of a conventional solid-state imaging device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Light receiving element, 1P ... Hole accumulation area, 1N ... Photoelectric conversion area, 3 ... Vertical shift register, 4, 4a ... Channel stop area, 6 ... Horizontal shift register, 10 ... N-type semiconductor substrate, 11 ... P-type well , 15 ... ground part

Claims (1)

[Claims] A first conductive type well region formed on a first conductive type semiconductor substrate; a first conductive type photoelectric conversion region formed on the well region; and a second conductive type well region formed on the well region. A light-receiving section in which a plurality of light-receiving elements each including the second conductivity type hole charge accumulation regions are arranged in a matrix; and a plurality of light-receiving sections for vertically transferring signal charges read from the plurality of light-receiving elements. A vertical shift register of columns, a horizontal shift register for transferring signal charges from the vertical shift registers of the plurality of columns in a horizontal direction, and a first vertical shift register provided between the vertical shift register and the light receiving element. In the solid-state imaging device having a channel stop region, along the first channel stop region,
A solid-state imaging device, wherein a second channel stop region is formed at a position deeper than the first channel stop region.