JP2002231929A - Solid-state image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and surely separate each photoelectric transducer element to prevent decline in resolution or mixing of colors even if small-size photoelectric transducer elements are arranged in high concentration. SOLUTION: A solid-state image pickup device 2 comprises a plurality of photoelectric transducer elements 106 which are arranged in proximity to each other on a silicon semiconductor substrate 104, with each photoelectric transducer element 106 comprising a p-type region 115 and an n-type region 116 which are locally deposited in layers on the surface of the semiconductor substrate 104. On the surface of the semiconductor substrate around each photoelectric transducer element 106, a trench 8 which reaches a deeper position than a bottom 6 of the n-type region 116 is formed. Each trench 8 is so formed as to surround the photoelectric transducer element 106 except on the corresponding vertical electric charge transfer register 108 side. A silicon oxide film 10 is deposited on the inner surface of each trench 8, and each trench 8 is filled with a metal material for reflecting light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a solid-state imaging device.

[0002]

2. Description of the Related Art FIG. 2 is a plan view showing an example of a conventional solid-state imaging device. FIG. −
FIG. 4B is a partial cross-sectional side view taken along the line BB ′ in FIG. 3.

The solid-state image sensor 102 shown in FIG. 2 is, for example, an interline solid-state image sensor, and a large number of photoelectric conversion elements 10 are mounted on a semiconductor substrate 104 made of silicon.
6 are arranged in a matrix at intervals. Then, a vertical charge transfer register 108 is provided for each column of the photoelectric conversion elements 106 in the column direction of the photoelectric conversion elements 106 (arrow V).
A horizontal charge transfer register 110 is provided at one end of 8 in the row direction of the photoelectric conversion element 106 (arrow H). An amplifier 112 is formed at one end of the horizontal charge transfer register 110.

In such a configuration, the electric charge generated by each photoelectric conversion element 106 in each column receiving light passes through a read area (not shown) interposed between the photoelectric conversion element 106 and the vertical charge transfer register 108. Are output to the corresponding vertical charge transfer register 108, and the vertical charge transfer register 108 sequentially transfers the charges to the horizontal charge transfer register 1.
Transfer to 10. Horizontal charge transfer register 110
Receives the charge from each vertical charge transfer register 108 and transfers it to the amplifier unit 112, and the amplifier unit 112 outputs a video signal through the output terminal 114 based on the transferred charge.

The periphery of the photoelectric conversion element 106 will be described in detail with reference to a cross-sectional view. As shown in FIG. 4B, the photoelectric conversion element 106 is locally laminated on the surface of a p-type semiconductor substrate 104. P-type region 115 and n-type region 11
In FIG. 4B, a corresponding vertical charge transfer register 108 is formed on the left surface of the semiconductor substrate in FIG. The second on the vertical charge transfer register 108
The transfer electrode 118 of the layer is formed with the insulating film 120 interposed therebetween, and the light shielding film 122 is formed thereon with the insulating film 120 interposed therebetween.

In FIG. 4B, on the right side of the photoelectric conversion element 106, a p-type region 124 in which a high concentration p-type impurity is introduced by, for example, an ion implantation method is formed as a channel stop region. This p-type region 124
As shown in FIG. 3, each photoelectric conversion element 106 is viewed in plan.
Is formed in a shape surrounding the vertical charge transfer register 108 except for the vertical charge transfer register 108 side.

Accordingly, in the cross section in the column direction of the photoelectric conversion elements 106, as shown in FIG. 4A, a p-type region 124 as a channel stop region is arranged between the adjacent photoelectric conversion elements 106. I have. In addition, FIG.
In the cross-sectional position shown in FIG. 7, a first-layer transfer electrode 126 and a second-layer transfer electrode 118 are stacked on a p-type region 124 with an insulating film 120 interposed therebetween.
Is covering.

[0008]

As described above, a high potential barrier is generated between the pixels by forming the p-type region 124 around each of the photoelectric conversion elements 106, that is, around the pixels by the high concentration impurity. Each pixel is separated. As a result, the signal charge generated by receiving light by each photoelectric conversion element 106 is supplied to the vertical charge transfer register 108 independently for each photoelectric conversion element 106.

However, the potential barrier due to the p-type region 124 is gradually made uniform from the surface of the substrate toward a deep position. Therefore, in the case of a structure in which the n-type region 116 of the photoelectric conversion element 106 is formed deep, the p-type region 124 does not sufficiently act, and the result is that signal charges are mixed between the adjacent photoelectric conversion elements 106. Become. When such mixing of the signal charges occurs, the resolution of the solid-state imaging device 102 is reduced. In the case of a solid-state imaging device that captures a color image, the adjacent photoelectric conversion device 10 is used.
Since 6 corresponds to different colors, color mixture between pixels occurs.

This problem can be avoided by introducing a p-type impurity with high energy and forming the p-type region 124 deep. However, high-energy ion implantation has poor controllability and wide spread in the lateral direction. Therefore, when the photoelectric conversion elements 106 are arranged at high density and the size of each photoelectric conversion element 106 is small, this method is used. It is difficult to use. Furthermore, a resist layer for masking at the time of ion implantation must be formed thick enough to withstand high-energy ion implantation. In this respect, fine processing is difficult, and when the size of the photoelectric conversion element 106 is small, In such a case, it is difficult to form the p-type region 124 deep.

The present invention has been made to solve such a problem, and an object of the present invention is to separate each photoelectric conversion element easily and reliably even when small-sized photoelectric conversion elements are arranged at high density. It is another object of the present invention to provide a solid-state imaging device capable of preventing a reduction in resolution and color mixing due to mixing of signal charges.

[0012]

In order to achieve the above object, the present invention comprises a plurality of photoelectric conversion elements arranged on a semiconductor substrate in close proximity to each other, and the photoelectric conversion elements are arranged on a surface of the semiconductor substrate. A region of the first conductivity type and a region of the second conductivity type which are locally laminated on the semiconductor substrate, wherein the region of the second conductivity type is a solid-state imaging device formed on the surface side of the semiconductor substrate, A trench is formed in a surface portion of the semiconductor substrate around the element, the trench reaching a position deeper than a bottom of the first conductivity type region.

As described above, in the solid-state imaging device of the present invention, the trench is formed in the surface of the semiconductor substrate around each photoelectric conversion element so as to reach a position deeper than the bottom of the first conductivity type region. The signal charge generated by the photoelectric conversion element is blocked by the trench and does not mix with the signal charge generated by another adjacent photoelectric conversion element. As a result, problems such as a decrease in resolution and color mixing between pixels do not occur.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. (A) and (B) of FIG.
FIG. 1 is a partial cross-sectional side view showing an example of a solid-state imaging device according to the present invention. In the drawings, the same elements as those in FIGS. 2 to 4 are denoted by the same reference numerals. The solid-state imaging device according to the embodiment described here is an interline solid-state imaging device as an example, and has a basic configuration similar to that of the solid-state imaging device 102 illustrated in FIG. That is,
A large number of photoelectric conversion elements are arranged in a matrix at intervals on a semiconductor substrate made of silicon. A vertical charge transfer register extends in the column direction of the photoelectric conversion elements for each column of the photoelectric conversion elements. A horizontal charge transfer register is disposed at one end of the vertical charge transfer register. An amplifier is formed at one end of the horizontal charge transfer register. It is assumed here that the photoelectric conversion element is a photodiode.

FIG. 1A shows a detailed cross section around the photoelectric conversion element in the column direction of the photoelectric conversion element, similarly to FIG. 4A, and FIG. 2) shows a detailed cross section around the photoelectric conversion element in the row direction of the photoelectric conversion element. This embodiment is different from the conventional solid-state imaging device in that a trench is formed as a channel stop region. That is, (A) of FIG.
As shown in (B), the solid-state imaging device 2 of the embodiment is illustrated.
Here, the semiconductor substrate surface around each of the photoelectric conversion elements 106 including the n-type region 116 (the region of the first conductivity type according to the present invention) and the p-type region 115 (the region of the second conductivity type according to the present invention) A trench 8 reaching a position deeper than the bottom 6 of the n-type region 116 is formed.

The trench 8 is formed at the same position as the p-type region 124 in the conventional solid-state image pickup device. Therefore, the same as the p-type region 124 of the conventional solid-state image pickup device 102 shown in FIG. , Except for a portion between the vertical charge transfer register 108 and the photoelectric conversion element 106 corresponding to the vertical charge transfer register 108.

As shown in FIGS. 1A and 1B, the insulating film 1 is formed on the inner surface of the trench 8 in this embodiment.
0 is deposited and the metal material 12 is filled inside. The insulating film 10 deposited on the inner surface of the trench 8
Can be formed, for example, as a silicon oxide film by thermal oxidation of semiconductor substrate 104, and metal material 12 filling trench 8 can be formed, for example, by depositing aluminum.

A p-type region 14 (a region of the second conductivity type according to the present invention) containing a high concentration of impurity is relatively formed in the surface of the semiconductor substrate between the photoelectric conversion element 106 and the adjacent trench 8. It is formed shallow. This p-type region 1
4 is a photoelectric conversion element 1 except for a portion between the photoelectric conversion element 106 and the corresponding vertical charge transfer register 108.
06 is formed.

The electrodes and the light-shielding film are the same as those of the conventional solid-state imaging device, and as shown in FIG. 1B, the second-layer transfer electrode 11 is placed on the vertical charge transfer register 108.
8 is formed via the insulating film 120, and the insulating film 1 is formed thereon.
The light-shielding film 122 is formed with the intermediary of the light-shielding film 20. Further, at the cross-sectional position shown in FIG.
The transfer electrodes 126 and 118 are formed on the
0, and a light-shielding film 122 covers the layers.

As described above, in the solid-state imaging device 2 of the present embodiment, the position deeper than the bottom 6 of the n-type region 116 constituting the photoelectric conversion element 106 is provided on the surface of the semiconductor substrate around each of the photoelectric conversion elements 106. Is formed, the signal charge generated by each photoelectric conversion element 106 is blocked by the trench 8 and does not mix with the signal charge generated by another adjacent photoelectric conversion element 106. Therefore, problems such as a decrease in resolution and color mixing between pixels do not occur.

In this embodiment, since the metal material 12 is filled in the trench 8, the light obliquely incident on the light receiving section 16 or the light scattered in the photoelectric conversion element 106, etc. After being emitted from the side of the conversion element 106, it is reflected on the side surface of the metal material 12 and reenters the photoelectric conversion element 106, and as a result, the sensitivity of the photoelectric conversion element 106 is improved.

Such a trench 8 can be easily formed by a widely used technique such as etching. Specifically, for example, the transfer electrode 12
6, 118 and before forming the oblique light film 122, the p-type region 14 is formed by a conventional method, for example, by ion implantation.
To form Thereafter, a silicon nitride film, for example, is formed on the surface of the semiconductor substrate and patterned to open only the location where the trench 8 is to be formed. Then, selective etching (for example, dry etching) is performed using the patterned silicon nitride film as a mask. To the required depth.

In the solid-state imaging device 2 of the present embodiment, since the formation of the trench 8 is so easy, even when the photoelectric conversion elements 106 having a small size are arranged at a high density, each photoelectric conversion element can be formed. The elements 106 can be surely separated to prevent a decrease in resolution and color mixing.

In this embodiment, the metal material 12 is filled in the trench 8. However, the metal material 12 may not be filled, but an insulating material may be filled or a hollow structure may be used. . Also in this case, since the trench 8 functions as a channel stop region, the signal charge generated by each photoelectric conversion element 106
, And do not mix with signal charges from other adjacent photoelectric conversion elements 106. Therefore, problems such as a decrease in resolution and color mixing between pixels do not occur. However, light emitted from the side of the photoelectric conversion element 106 is reflected at the trench portion and is again reflected on the photoelectric conversion element 10.
In this respect, it is desirable to adopt a structure in which the metal material 12 is filled in the trench 8 in order to obtain a high light reflectivity, since the effect of entering into the inside 6 is not obtained or is weakened.

In this embodiment, the p-type region 14 is formed together with the trench 8.
The purpose of forming is not to separate the pixels but to quickly discharge holes collected below the n-type region 116 constituting the photoelectric conversion element 106. Therefore, it is not particularly necessary to make it deep, and the formation is easy. Although a mask made of a silicon nitride film is used when forming the trench 8, a material of the mask is not necessarily a silicon nitride film as long as the material has a lower etching rate than the semiconductor substrate 104 at the time of etching. .

In the present embodiment, the photoelectric conversion elements 106 are arranged in a matrix. However, even in the case where the photoelectric conversion elements are linearly arranged as in a linear image sensor or the like. The present invention is effective, and a similar effect can be obtained by forming a trench around each photoelectric conversion element 106. In the present embodiment, the solid-state imaging device 2 is of the interline type. However, as will be apparent from the above description, the present invention is applied to each photoelectric conversion device 1.
The present invention is applicable to a structure other than the interline type since the charge transfer method is related to the structure around the address line 06.

[0027]

As described above, in the solid-state imaging device of the present invention, the surface of the semiconductor substrate around each photoelectric conversion element is
Since the trench is formed to a position deeper than the bottom of the first conductivity type region constituting the photoelectric conversion element, the signal charge generated by each photoelectric conversion element is blocked by this trench, and the other adjacent charge is blocked. There is no mixing with the signal charge by the photoelectric conversion element. As a result, problems such as a decrease in resolution and color mixing between pixels do not occur. And since the above-mentioned trench can be easily formed by a conventionally widely used technique such as etching, even when small-sized photoelectric conversion elements are arranged at a high density, a reduction in resolution and color mixing are reliably prevented. can do.

[Brief description of the drawings]

FIGS. 1A and 1B are partial cross-sectional side views showing an example of a solid-state imaging device according to the present invention.

FIG. 2 is a plan view illustrating an example of a conventional solid-state imaging device.

FIG. 3 is a partially enlarged plan view showing a part of the solid-state imaging device of FIG. 2 in detail;

4A is a partial sectional side view taken along line AA ′ in FIG. 3, and FIG. 4B is a partial sectional side view taken along line BB ′ in FIG.

[Explanation of symbols]

2 ... solid-state image sensor, 6 ... bottom, 8 ... trench, 1
0 ... insulating film, 12 ... metal material, 14 ... p-type region,
16 light receiving section, 102 solid-state imaging device, 104
Semiconductor substrate, 106 photoelectric conversion element, 108 vertical charge transfer register, 110 horizontal charge transfer register, 112 amplifier section, 114 output terminal, 115
... p-type region, 116 ... n-type region, 118 ... transfer electrode, 120 ... insulating film, 122 ... light shielding film, 124 ...
p-type region, 126... transfer electrode.

Claims (8)

[Claims] 1. A semiconductor device comprising: a plurality of photoelectric conversion elements arranged in close proximity to each other on a semiconductor substrate, wherein the photoelectric conversion elements are of a first conductivity type and a second conductivity type locally laminated on a surface portion of the semiconductor substrate. A solid-state imaging device formed on the surface side of the semiconductor substrate, wherein the second conductivity type region includes a first conductive type region,
A solid-state imaging device, wherein a trench reaching a position deeper than a bottom of a conductive type region is formed. 2. The solid-state imaging device according to claim 1, wherein an insulating film is provided on an inner surface of said trench. 3. The solid-state imaging device according to claim 2, wherein a metal material is filled inside the trench. 4. The solid-state imaging device according to claim 1, wherein an insulating material is filled inside said trench. 5. The solid-state imaging device according to claim 2, wherein the semiconductor substrate is made of silicon, and the insulating film is made of silicon oxide. 6. The solid-state imaging device according to claim 3, wherein said metal material is aluminum. 7. A semiconductor substrate surface portion between the photoelectric conversion element and the trench adjacent to the photoelectric conversion element, wherein a region containing a high-concentration second conductivity type impurity is formed. The solid-state imaging device according to claim 1. 8. The photoelectric conversion elements are arranged in a matrix on the semiconductor substrate, and a vertical charge transfer register is provided for each column of the photoelectric conversion elements so as to extend in a column direction of the photoelectric conversion elements. The transfer register takes in and transfers charges from the photoelectric conversion elements in a corresponding column, and the trench excludes a portion between the vertical charge transfer register and the photoelectric conversion element corresponding to the vertical charge transfer register. 2. The solid-state imaging device according to claim 1, wherein the solid-state imaging device is formed around the photoelectric conversion element.