JP3067562B2 - Solid-state imaging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state imaging device,
In particular, it relates to a charge-coupled device (hereinafter, referred to as “CCD”).

[0002]

2. Description of the Related Art FIG. 7 is a schematic view of a charge transfer device, wherein (1)
20) is a photosensitive section, (121) is a vertical CCD section, (12)
2) shows a horizontal CCD unit, and (123) shows a charge detection unit, which is a plan view of a solid-state imaging device. The conventional one will be described with reference to FIGS. 4, 5 and 6. FIG. FIG. 4 is a plan view showing a connection portion between a conventional vertical CCD and a horizontal CCD, FIG. 5 is a vertical sectional view of a Y2-Y2 'portion of FIG. 4, and FIG. 6 is a Y2-Y2' portion of FIG. FIG.

Conventionally, a connection between a vertical CCD section and a horizontal CCD section is as shown in FIG. (102) is N
Well vertical CCD, (103) horizontal CCD
(104) is a channel stopper made of a high-concentration P-type semiconductor, (105) is a vertical CCD final gate electrode made of a first gate polysilicon, (106) is a horizontal CCD electrode A made of a second gate polysilicon, and (107) is This is the horizontal CCD electrode B made of the first gate polysilicon.

FIG. 5 is a vertical sectional view taken along line Y2-Y2 'of FIG. 4. As shown in FIG.
(109) has a dose of 2.0E12 [cm ⁻² ] and a dose of 1
The first P-well formed by pressing at 300 [° C.] for 5.0 hours, which is the impurity diffusion region. (110) indicates a dose of 3.0E11 [cm ⁻² ].
And a second P-well formed by pressing at 1100 [° C.] for 7.0 hours, which is an impurity diffusion region. (101 ′) has a dose of 2.5E12 [cm ⁻² ].
The third P-well formed by pressing at 1100 [° C.] for 1.0 hour, which is the impurity diffusion region.

[0005] (111) is formed by an N-well (NWELL) with a dose of about 4.0E12 [cm ^-2 ]. Also, (113) is an N- region, and (11)
3) 8E12 [cm ⁻² ] using the first gate polysilicon electrode formed via the oxide film (112) as a mask.
Of boron is implanted into the N-region.

FIG. 6 is a potential diagram of the Y2-Y2 'portion of FIG. 4 at the time of charge transfer from the vertical CCD to the horizontal CCD. A voltage of about -10 [V] is applied to the vertical final electrode, and a voltage of about 5 [V] is applied to both the horizontal CCD electrodes A and B. At this time, the potentials of the b and c regions of the vertical CCD portion become shallower than those of the horizontal CCD portion d due to the narrow channel effect, and since the b region is N-, the potential is further shallower than the c region. .

Therefore, since the potential of the Y2-Y2 'portion becomes a step-like potential, the electric charge is transferred from the vertical CCD to the horizontal CCD due to this potential difference. However, in the structure of the vertical CCD connected to the conventional horizontal CCD, there is a portion where the potential in the charge transfer direction has no gradient in the regions b and c in FIG. 6 below the horizontal transfer electrode regions A and B. In this portion, the transfer speed of the charges is reduced and the charges are clogged, that is, transfer deterioration occurs.

For the purpose of improving such transfer deterioration, Japanese Patent Application Laid-Open No. 63-318156 and Japanese Patent Application Laid-Open No.
There are 73. In the former, the vertical CCD is composed of a single gate and the impurity concentration is changed so as to have a potential gradient in the transfer direction. In the latter, the channel width is set in the transfer direction to improve the transfer efficiency between a plurality of horizontal registers. It is widened.

[0009]

However, in the connection between the vertical CCD and the horizontal CCD at issue, a potential gradient cannot be provided within the same electrode because of the presence of the transfer electrode of the horizontal CCD. As for the method of expanding the CCD width in the horizontal CCD direction, FIG.
There is a limit because the potential difference due to the narrow channel effect in the c region is reduced, which limits the degree of freedom in design. Therefore, transfer deterioration cannot be prevented efficiently, which causes a failure mode such as a black vertical line being seen on a screen at low illuminance.

[0010]

According to the present invention, there is provided a vertical CCD and a horizontal CCD having a first conductivity type region in which a second conductivity type well is formed in a first conductivity type substrate.
In the solid-state imaging device but that will be formed, the second conductivity type well under the vertical CCD, the third P-well diffusion
Region and is constituted by the said third P-well diffusion region shallower than and the third P-well of the high-concentration impurity diffused region second P-well diffusion region, said horizontal CC
Said second conductivity type wells under D, the third P-well non
A pure diffusion region, and a first P-well impurity diffusion region formed at a lower concentration than the second P-well impurity diffusion region and deeper in the substrate direction than the second P-well impurity diffusion region . in the configuration, it is a solid state imaging device, characterized in that said second P-well impurity diffusion region under the vertical CCD tether portion between the horizontal CCD is with a continuous potential gradient in the charge transfer direction . According to the present invention, there is provided a solid-state imaging device in which a continuous potential gradient is provided in a charge transfer direction, but the second P-well impurity diffusion region is not provided radially in a horizontal CCD direction.

[0011]

According to the present invention, a vertical CCD capacity is secured under a vertical CCD connected to a horizontal CCD, and a signal charge during transfer of the vertical CCD flows to the substrate side by a voltage applied to the substrate during a shutter operation. Since the P-well for preventing is formed by radiating in the charge transfer direction, a potential gradient is provided in the charge transfer direction, the charge transfer speed can be increased, and a black vertical line can be seen on the screen at low illuminance. Such a failure mode does not occur.

[0012]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a plan view of a vertical CCD section connected to a horizontal CCD according to an embodiment of the present invention. FIG.
It is a vertical sectional view of 1 'part. As shown in FIG.
The vertical CCD section connected to the CD is, in its plan view,
A second P-well impurity diffusion region in the first conductivity type substrate;
(10) Vertical CCD (2), horizontal CCD (3), channel stopper (4), vertical CCD final transfer electrode (5), horizontal CCD transfer electrode A (6), horizontal CCD transfer electrode B (7) formed Is what is being done.

FIG. 2 is a sectional view taken along the line Y1-Y1 'of FIG.
As shown in (1), an N-type semiconductor substrate (8) as a first conductivity type substrate has an impurity diffusion region (9) of a first P well as a second conductivity type well and a third P type well as a second conductivity type well. P
There is a well impurity diffusion region (1 '). A vertical CCD and a horizontal CCD comprising the first conductivity type region are formed in the impurity diffusion region (1 ') of the third P well which is the second conductivity type well. A second P-well impurity diffusion region (10) is formed in the direction of the substrate in the third P-well impurity diffusion region (1 ') below the vertical CCD. Then, the N well (11) and the oxide film (1
2) A vertical CCD final transfer electrode (5), a horizontal CCD transfer electrode A (6) and a horizontal CCD transfer electrode B (7) are provided.

This will be specifically described. Horizontal C
Below the CD, a dose of 2.0E-12 [cm ^-2 ] and 1
A first P well formed by pressing at 300 [° C.] for 5.0 hours, and a dose of 3.0E11 [c]
m ^-2 ], a third P-well formed by pressing at 1100 [° C] for 7.0 hours is created, and a vertical CC
Below D, a third P well and a dose of 2.5E12 [c
m ⁻² ], and a second P-well formed by pressing for 1 hour at 1100 [° C.] is formed.

The second P-well of the vertical CCD section connected to the horizontal CCD is not ion-implanted from a portion under the horizontal CCD electrode A to a portion under the horizontal CCD electrode B, and the second P-well impurity diffusion is performed. A portion where no region is formed is provided radially. In this manner, the impurity diffusion amount in the horizontal direction of the second P well is different from the point e to the point f, so that there is a concentration difference such that the impurity concentration of the N well becomes higher from the point e to the point f. 5 for CCD electrodes A and B
Even if [V] is applied, a potential gradient can be applied to this portion, so that the potential of the Y1-Y1 ' portion is as shown in FIG. Since the potential increases as the area where the second P-well does not enter increases, there is no place where the potential becomes constant in the areas b and c, and a potential gradient can be provided.
Therefore, the charge transfer speed can be increased.

[0016]

As described above, according to the present invention,
Vertical CCD below the vertical CCD connected to the horizontal CCD
An area in which a P-well created for the purpose of securing capacity and preventing signal charges during transfer of the vertical CCD from flowing to the substrate side by a voltage applied to the substrate during shutter operation is not radially ion-implanted in the charge transfer direction. Therefore, the impurity concentration of the N well is increased in the charge transfer direction, a potential gradient is provided, and the charge transfer speed can be increased.

[Brief description of the drawings]

FIG. 1 is a plan view of a vertical CCD unit connected to a horizontal CCD according to an embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view taken along a line Y1-Y1 ′ of FIG. 1;

FIG. 3 is a potential diagram of a Y1-Y1 ′ part in FIG. 1;

FIG. 4 is a plan view showing a connection portion between a conventional vertical CCD and a horizontal CCD.

FIG. 5 is a vertical cross-sectional view taken along a line Y2-Y2 ′ in FIG. 4;

FIG. 6 is a potential diagram of a Y2-Y2 ′ portion of FIG.

FIG. 7 is a schematic diagram of a charge transfer device.

[Explanation of symbols]

 2.102 Vertical CCD 3.103 Horizontal CCD 4.104 Channel stopper 5.105 Vertical CCD final transfer electrode 6.106 Horizontal CCD transfer electrode A 7.107 Horizontal CCD transfer electrode B 8.108 N-type semiconductor substrate 9.109 One P-well impurity diffusion region 10.110 Second P-well impurity diffusion region 11.111 N well 12.112 Oxide film 13.113 N-region 1 ′. 101 'Third P-well impurity diffusion region 120 Photosensitive section 121 Vertical CCD section 122 Horizontal CCD section 123 Charge detection section

Claims (2)

(57) [Claims] 1. A second conductive type well is formed in the first conductivity type substrate, the solid-state imaging device where the vertical CCD and the horizontal CCD is Ru is formed consisting of a first conductivity type region to said second conductivity type in the well
Oite, said second conductivity type wells under the vertical CCD, the third P
The well impurity diffusion region, said third P-well impurities expansion
It is composed of a shallower than diffusing region and the third P-well diffusion region <br/> higher concentrations of the second P-well diffusion region, the second conductivity type well below the horizontal CCD, the first three
And the P-well diffusion region of said second P-well impure
The second P-well impurity diffusion at a lower concentration than the material diffusion region.
First P well impurity formed deeper in the substrate direction than the region
Things diffusion region and is constituted by the under vertical CCD said second P-well diffusion tether portion between the horizontal CCD
A solid-state imaging device, wherein a region has a continuous potential gradient in a charge transfer direction. 2. A place where with a continuous potential gradient in the charge transfer direction, the second P radially in the horizontal CCD direction
2. The structure according to claim 1, wherein there is no well impurity diffusion region.
3. The solid-state imaging device according to item 1.