JP2002198507A - Solid-state image pickup element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid-state image pickup element which can prevent color mixture between the horizontal picture elements of an image pickup signal. SOLUTION: P-type well areas 205 underlying vertical transfer register sections 80 are formed at deep positions in an N-type semiconductor substrate 60 in the thickness direction of the substrate 60. The deep P-type well areas 205 are formed to inhibit the horizontal movement of charges stored in a sensor section 70 through N-areas underlying the register sections 80. The well areas 205 are formed by implanting boron ions into the substrate 60 with high energy. The well areas 205 reach the vicinities of P-type well layers 201 and inhibit the horizontal movement of charges in the underlying layers of the register sections 80. Consequently, the color mixture between the horizontal picture elements of the image pickup signal can be prevented.

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 which transfers signal charges of a pixel sensor section arranged in a matrix by a vertical transfer register section and a horizontal transfer register section and outputs the signal charge as an image pickup signal. The present invention relates to a technique for preventing color mixture occurring between pixels in the horizontal direction.

[0002]

2. Description of the Related Art FIG. 3 is a schematic plan view for explaining the arrangement of a sensor section and a transfer register of a solid-state image sensor. In the CCD solid-state imaging device, a plurality of sensor units 20 each constituting an imaging pixel are arranged in a matrix on a semiconductor substrate 10 and a plurality of vertical (V) lines are arranged along the vertical arrangement of the sensor units 20. A transfer register section 30 is provided, and a horizontal (H) transfer register section 40 is provided outside one end of each vertical register section 30.
Each sensor unit 20 has, for example, a configuration of a photodiode, and converts light incident from the light receiving surface into a signal charge corresponding to the light amount. The vertical transfer register section 30 takes in the signal charges accumulated in the sensor section 20 through a read gate section described later and transfers the signal charges in the vertical direction. The horizontal transfer register section 40 transfers the signal charges from the vertical transfer register section 30 horizontally. To the output unit 50 as an image signal.
Output more.

FIG. 4 is a partial sectional view showing the internal structure of the solid-state imaging device shown in FIG. In FIG. 4, a P-type well layer 101 is formed on the entire surface of a deep portion of the N-type semiconductor substrate 10, and leakage of signal charges into the deep portion of the semiconductor substrate 10 is caused by the P-type well layer 101. An overflow barrier (OFB) is formed by a potential barrier for preventing the above. A certain amount of signal charge is accumulated in each sensor unit 20 by the overflow barrier, and when the accumulated amount of the signal charge exceeds a certain value, the signal charge is discharged to the substrate 10 through the overflow barrier.

[0004] The sensor section 20 comprises a light-receiving section composed of a high-concentration P + type region 102 provided on the surface of the substrate 10 and a charge storage section composed of an N-type region 103 provided thereunder. It is what constituted.
The vertical transfer register section 30 includes an N-type region 104 provided on the surface of the substrate 10 and a P-type region provided thereunder.
And a mold well region 105. Further, between the sensor unit 20 and the vertical transfer register unit 30, a read gate unit including a P-type region 106 is provided.
Outside the vertical transfer register unit 30 and the sensor unit 20,
A channel stop region including a P-type region 107 is provided.

FIG. 5 is an explanatory diagram showing an energy potential structure in such a conventional solid-state imaging device.
5, the horizontal axis represents the depth of the semiconductor substrate 10, and the vertical axis represents the potential. Also, curve A2
Indicates a potential curve of the sensor unit 20, and a curve B2 indicates a potential curve of the vertical transfer register unit 30. As shown in the figure, the potential curves A2 and B2 of the sensor unit 20 and the vertical transfer register unit 30 are both increased at the position of the overflow barrier (OFB), so that signal charges are prevented from leaking.

[0006]

However, in the above-mentioned conventional solid-state imaging device, when a large amount of light is received, an overflow barrier (OFB) is required as shown in FIG.
In the vicinity of the upper layer (the area indicated by b in the figure), the potential curve A of the sensor unit 20 and the vertical transfer register unit 30
Since B2 and B2 are substantially the same, a phenomenon occurs in which the charges in the sensor unit 20 pass through the lower layer of the vertical transfer register unit 30 and move to the adjacent sensor unit in the horizontal transfer direction. That is, this results in the movement of charges in the horizontal transfer direction, which causes a problem that color mixing occurs between pixels in the horizontal direction of the imaging signal.

SUMMARY OF THE INVENTION An object of the present invention is to provide a solid-state image sensor capable of preventing color mixture occurring between pixels of an image signal in a horizontal direction.

[0008]

According to the present invention, in order to achieve the above object, signal charges of a pixel sensor section arranged in a matrix are transferred by a vertical transfer register section and a horizontal transfer register section and output as an image pickup signal. In the solid-state imaging device, a second-type semiconductor well layer provided in the first-type semiconductor substrate and constituting an overflow barrier for signal charges accumulated in the pixel sensor unit; and an upper layer of the first-type semiconductor substrate A second type semiconductor light receiving region and a first type semiconductor charge accumulation region constituting the pixel sensor unit, and a first type semiconductor charge accumulation region, the pixel type sensor substrate being provided on the first type semiconductor substrate in a vertical transfer direction to the pixel sensor unit; A first type semiconductor transfer region and a second type semiconductor well region constituting a vertical transfer register portion; and a pixel sensor portion and a vertical transfer register portion of the first type semiconductor substrate. Provided between, and a second type semiconductor region constituting the read gate signal charge, the second
Since the type semiconductor well region is formed deep in the thickness direction of the first type semiconductor substrate, the energy potential of the vertical transfer register section becomes larger than the energy potential of the pixel sensor section in the vicinity of the upper layer side of the overflow barrier. It is characterized by doing so.

In the solid-state imaging device according to the present invention, the energy potential of the vertical transfer register section is made larger than the energy potential of the pixel sensor section in the vicinity of the upper layer side of the overflow barrier. Even when the size of the accumulated charge increases, it is possible to prevent the accumulated charge from moving to the pixel sensor unit adjacent to the horizontal direction below the vertical transfer register unit. Therefore, it is possible to prevent such movement of the charges in the horizontal direction, and it is possible to prevent color mixing that occurs between pixels in the horizontal direction of the imaging signal.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the solid-state imaging device according to the present invention will be described below. FIG. 1 is a partial sectional view showing the internal structure of the solid-state imaging device according to the embodiment of the present invention. The overall configuration of the solid-state imaging device according to this embodiment is, for example, the same as that shown in FIG. In FIG. 1, a P-type well layer 201 is formed on the entire surface of a deep portion of an N- type semiconductor substrate 60,
The P− type well layer 201 forms an overflow barrier (OFB) in a deep portion of the semiconductor substrate 60 by a potential barrier for preventing leakage of signal charges.
A certain amount of signal charge is accumulated in each sensor unit 70 by the overflow barrier, and when the accumulated amount of the signal charge exceeds a certain value, the signal charge is discharged to the substrate 60 side through the overflow barrier.

The sensor section 70 includes a light-receiving section composed of a high-concentration P + type area 202 provided on the surface of the substrate 60 and a charge storage section composed of an N-type area 203 provided thereunder. It is what constituted.
The vertical transfer register section 80 includes an N-type region 204 provided on the surface of the substrate 60 and a P-type region provided thereunder.
And a mold well region 205. Further, between the sensor unit 70 and the vertical transfer register unit 80, a read gate unit including a P-type region 206 is provided.
Outside the vertical transfer register section 80 and the sensor section 70,
A channel stop region including a P-type region 207 is provided.

In the solid-state image pickup device of this embodiment, the P-type well region 2 in the lower layer of the vertical transfer
Reference numeral 05 is formed to a position deeper in the thickness direction of the semiconductor substrate 60 than the P-type well region 105 of the conventional example shown in FIG. That is, in this example, the accumulated charge of the sensor unit 70 moves in the horizontal direction (the direction of the arrow H in the drawing) through the N region below the vertical transfer register unit 80 due to such a deep P − type well region 205. It has a structure to prevent this. Such a P-type well region 205
Is formed by implanting, for example, boron ions into the N − type semiconductor substrate 60 and performing thermal diffusion. Then, in this example, after forming a similar shallow portion 205A of the N-type region 204 and the P − -type well region 205 by the same ion implantation as in the related art, boron ions are implanted at a high energy, thereby -A deep portion 205B of the mold well region 205 is formed. Deep portion 205B of this P-type well region 205
Reaches a position near the P-type well layer 201,
This is to prevent the electric charge in the lower layer of the vertical transfer register section 80 from moving in the horizontal direction (the direction of the arrow H in the figure).

FIG. 2 is an explanatory diagram showing an energy potential structure in the solid-state imaging device of this embodiment. 2, the horizontal axis indicates the depth of the semiconductor substrate 60, and the vertical axis indicates the potential. Further, the curve A1 corresponds to the sensor unit 7
0 indicates a potential curve, and curve B1 indicates a potential curve of the vertical transfer register unit 80. As shown in the figure, the potential curves A1 and B1 of the sensor unit 70 and the vertical transfer register unit 80 are both increased at the position of the overflow barrier (OFB), thereby preventing leakage of signal charges. In addition, the potential curve B1 of the vertical transfer register section 80 is obtained by forming the P − -type well region 205 to a deep position as described above, so that the position near the upper layer side of the overflow barrier (OFB) (region indicated by a in the drawing) , The potential curve A1 of the sensor unit 70
Is located higher.

Accordingly, even when the amount of light received by the sensor unit 70 increases, the phenomenon that the charges in the sensor unit 70 move through the lower layer of the vertical transfer register unit 80 to the adjacent sensor unit in the horizontal transfer direction is prevented. it can. Therefore, by preventing such charge transfer in the horizontal transfer direction, it is possible to prevent a problem that color mixing occurs between pixels in the horizontal direction of the imaging signal.

In the above example, the P− type well region 2
Although 05 is formed by boron ion implantation, the present invention can be similarly applied to a case where a P-type well region is formed by another impurity doping method.

[0016]

As described above, in the solid-state imaging device according to the present invention, the second-type semiconductor well layer provided in the first-type semiconductor substrate and forming an overflow barrier for signal charges accumulated in the pixel sensor portion is provided. A second type semiconductor light receiving region and a first type semiconductor charge storage region which are provided in an upper layer of the first type semiconductor substrate and constitute a pixel sensor portion; And a first type semiconductor transfer region and a second type semiconductor well region constituting the vertical transfer register portion, and provided between the pixel sensor portion and the vertical transfer register portion of the first type semiconductor substrate. And a second type semiconductor region constituting a signal charge readout gate, wherein the second type semiconductor well region is formed deep in the plate thickness direction of the first type semiconductor substrate, so that an upper layer side of the overflow barrier is formed. Energy potential of the vertical transfer register portion in the near portion is set to be greater than the energy potential of the pixel sensor portions.

Therefore, according to the solid-state imaging device of the present invention, the energy potential of the vertical transfer register section is made larger than the energy potential of the pixel sensor section near the upper layer side of the overflow barrier. Even if the accumulated charge increases,
It is possible to prevent the accumulated charges from moving to a horizontally adjacent pixel sensor section below the vertical transfer register section, and thus it is possible to prevent color mixing that occurs between pixels in the horizontal direction of the image pickup signal.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view illustrating an internal structure of a solid-state imaging device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an energy potential structure in the solid-state imaging device shown in FIG.

FIG. 3 is a schematic plan view for explaining an arrangement of a sensor unit and a transfer register of the solid-state imaging device.

FIG. 4 is a partial sectional view showing an internal structure of the solid-state imaging device shown in FIG.

FIG. 5 is an explanatory diagram showing an energy potential structure in the solid-state imaging device shown in FIG.

[Explanation of symbols]

60 N-type semiconductor substrate 70 Sensor part 80
... vertical transfer register section, 201-P-type well layer, 2
02 ... P + type region, 203, 204 ... N type region, 2
05: P-type well region, 206, 207: P-type region.

Claims (6)

[Claims] 1. A solid-state imaging device that transfers signal charges of a pixel sensor unit arranged in a matrix by a vertical transfer register unit and a horizontal transfer register unit and outputs the signal charges as an image signal. A second barrier constituting an overflow barrier for signal charges stored in the pixel sensor unit.
A type semiconductor well layer, a second type semiconductor light receiving region and a first type semiconductor charge storage region provided on the first type semiconductor substrate and constituting the pixel sensor unit, and an upper layer of the first type semiconductor substrate A first-type semiconductor transfer region and a second-type semiconductor well region provided in the pixel sensor unit along a vertical transfer direction and constituting the vertical transfer register unit; and a pixel sensor unit of the first-type semiconductor substrate. And a second-type semiconductor region provided between the first and second vertical transfer register portions and forming a signal charge readout gate. The second-type semiconductor well region is formed deep in the thickness direction of the first-type semiconductor substrate. By doing so, the energy potential of the vertical transfer register section becomes higher than the energy potential of the pixel sensor section in the vicinity of the upper layer side of the overflow barrier. A solid-state imaging device, wherein the, the. 2. The first type semiconductor is an N type semiconductor,
The solid-state imaging device according to claim 1, wherein the second type semiconductor is a P-type semiconductor. 3. The second type semiconductor well region is formed by adding an impurity for the second type semiconductor well region to a position deep in a thickness direction of the first type semiconductor substrate. The solid-state imaging device according to claim 2. 4. The solid-state imaging device according to claim 3, wherein said impurity is added by ion implantation. 5. The solid-state imaging device according to claim 4, wherein said impurity is boron, and a P-type semiconductor well region is formed deep by implanting high-energy boron ions. 6. The semiconductor device according to claim 1, wherein said second type semiconductor well region is formed of said second type semiconductor well region.
2. The solid-state imaging device according to claim 1, wherein the solid-state imaging device reaches a portion near the semiconductor well layer.