JP2001237404A - Amplifying solid-state image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an amplifying solid-state image pickup device in which shading due to reduction of the condensing ratio is suppressed at the periphery of the image sensing area. SOLUTION: In the amplifying solid-state image pickup device comprising a semiconductor substrate 1, a plurality of photodetecting parts 2 formed in the semiconductor substrate 1, a plurality of mutually stached shading layers 4 formed above the semiconductor substrate 1, and interlayer insulation films 3 formed between the shading layers 4 having a plurality of openings, corresponding to the photodetecting parts 2 one to one, the openings are formed so that the deviation of the center of the opening from the center of corresponding photodetecting part 2 increases away from the center of the image sensing area to its periphery in the topmost shading layer which is most distant from the semiconductor substrate 1 among the plurality of shading layers 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an amplifying solid-state imaging device, and more particularly, to an amplifying solid-state imaging device that suppresses a drop (shading) of a signal level generated at a peripheral portion of an output image. is there.

[0002]

2. Description of the Related Art As a solid-state imaging device, a CCD solid-state imaging device, an amplification-type solid-state imaging device, and the like are known. In particular, an amplification type solid-state imaging device has an advantage that it can be formed into one chip with a peripheral circuit, and thus has attracted attention as an image input element of a portable device.

[0003] In these solid-state imaging devices, there is a problem of suppressing shading occurring at a peripheral portion of an output image. In the solid-state imaging device, since the optical center of the imaging optical system is arranged on the center extension line of the imaging region (the region where the pixels are arranged), when the exit pupil distance is finite, light is vertical at the center of the imaging region. At the periphery of the imaging area, light enters obliquely. Therefore, in the peripheral part of the imaging area, the center of light collection by the microlens is shifted from the center of the light receiving unit, and the light collection rate to the light receiving unit is reduced.
It is known that such a decrease in the light collection rate in the peripheral portion of the imaging region is a cause of shading.

FIG. 6 is a sectional view showing the structure of a CCD type solid-state imaging device. In the semiconductor substrate 21, a plurality of light receiving sections 22 are arranged in a matrix. Further, although not shown, a charge transfer portion is formed in the semiconductor substrate 21 adjacent to each column of the light receiving portion 22, and a transfer electrode is formed on the charge transfer portion via an insulating film. . A light-shielding layer 24 is formed on the semiconductor substrate 21, and a plurality of openings are formed in the light-shielding layer 24 so as to correspond to each of the light-receiving units 22. An interlayer insulating film 23 is formed on the light shielding layer 24, and a plurality of microlenses 25 are formed on the interlayer insulating film 23 so as to correspond to each of the light receiving units 22.

In such a CCD type solid-state imaging device, as shown in FIG. 6, shading can be suppressed by shifting a microlens 25 disposed around an imaging region with respect to a light receiving unit 22. It has been proposed (for example, JP-A-6-140609). The displacement (Lm) between the microlens 25 and the corresponding light receiving unit 22 is adjusted so as to gradually increase from the center of the imaging area toward the periphery. According to such a CCD solid-state imaging device, shading in the peripheral portion of the output image can be sufficiently suppressed.

[0006]

In the amplification type solid-state image pickup device, as in the CCD type solid-state image pickup device, as means for suppressing shading in the peripheral portion of the output image,
It has been proposed to shift a microlens disposed in a peripheral portion of an imaging region with respect to a light receiving unit.

FIG. 7 is a sectional view showing the structure of such an amplification type solid-state imaging device. A plurality of light receiving sections 32 are arranged in a matrix in a semiconductor substrate 31. Further, although not shown, MOS transistors forming an amplifier circuit in the pixel are formed on the semiconductor substrate 31 so as to correspond to each of the light receiving sections 32. On the semiconductor substrate 31, a plurality of light-shielding layers 34 are stacked on each other with an interlayer insulating film 33 interposed therebetween. Each light shielding layer 34 has an opening formed corresponding to each of the light receiving sections 32. Further, a plurality of micro lenses 35 are formed above the light receiving section 32 so as to correspond to the respective light receiving sections 32.
And the corresponding positional deviation (Lm) with respect to the light receiving unit 32
Is adjusted so as to gradually increase from the center to the periphery of the imaging region.

However, in such an amplification type solid-state imaging device, shading in a peripheral portion of an output image cannot be sufficiently suppressed.

An object of the present invention is to provide an amplification type solid-state imaging device in which shading in a peripheral portion of an output image is suppressed.

[0010]

In order to achieve the above object, an amplification type solid-state imaging device according to the present invention comprises a semiconductor substrate, a plurality of light receiving portions formed in the semiconductor substrate, and a light receiving portion provided above the semiconductor substrate. A plurality of light-shielding layers formed and stacked on each other, and an interlayer insulating film formed between the light-shielding layers, wherein the light-shielding layer has a plurality of openings formed corresponding to each of the light receiving portions. In the amplification type solid-state imaging device having a portion, at least in the uppermost light-shielding layer farthest from the semiconductor substrate among the plurality of light-shielding layers, the center of the opening and the center of the corresponding light-receiving portion. The opening is formed such that the deviation increases from the center to the periphery of the imaging region.

In the CCD type solid-state image pickup device, only one light-shielding layer is formed, and the distance from the light receiving portion to the microlens is relatively short. Can be suppressed. On the other hand, in the amplification type solid-state imaging device, since the wiring constituting the amplification circuit is used as a light shielding layer, a plurality of light shielding layers are formed, and as a result, the distance from the light receiving section to the microlens becomes long. Therefore, as shown in FIG. 7, in the peripheral portion of the imaging region, even if the micro lens is shifted, it is inevitable that the incident light is blocked by the light shielding layer, and the light collection rate is reduced.

However, according to the amplification type solid-state imaging device of the present invention, at least the opening formed in the uppermost light-shielding layer is shifted from the light-receiving portion in the peripheral portion of the imaging region, so that the light-shielding is achieved. The incident light blocked by the layer can be reduced, and a decrease in the light collection rate can be suppressed. As a result, shading in the peripheral portion of the output image can be suppressed. In the center of the imaging area,
It is preferable that the center of the opening formed in the light-shielding layer and the center of the light-receiving section are not misaligned.

In the amplifying solid-state imaging device, in the plurality of light-shielding layers, it is preferable that a shift between the center of the opening and the center of the corresponding light-receiving portion increases from a lower layer toward an upper layer. This is because shading can be reliably suppressed even when the number of light shielding layers is large.

In the amplification type solid-state imaging device, when the light incident on the amplification type solid-state imaging device diverges or converges, the center of the opening is positioned forward of the center of the corresponding light receiving portion. It is preferable that the light is shifted in a direction corresponding to the optical path of the incident light. This is because shading can be more reliably suppressed.

For example, when light incident on the amplification type solid-state imaging device diverges, the center of the opening is shifted from the center of the corresponding light receiving portion toward the center of the imaging region. Is preferred. Further, when the incident light to the amplification type solid-state imaging device converges, the center of the opening,
It is preferable that the light receiving unit is shifted from the center of the corresponding light receiving unit in a direction toward the peripheral portion of the imaging region.

The amplification type solid-state imaging device further includes a plurality of microlenses formed above the light shielding layer so as to correspond to each of the light receiving portions, and the center of the microlenses and the corresponding microlenses are provided. The deviation from the center of the light receiving portion increases from the center of the imaging region toward the peripheral portion, and the deviation between the center of the opening in the uppermost light shielding layer and the corresponding center of the light receiving portion. Preferably, the microlenses are formed so as to be larger than the above. According to this preferred example, shading can be surely suppressed.

In this preferred example, when the light incident on the amplification type solid-state imaging device diverges or converges, the center of the microlens is positioned on the optical path of the incident light with respect to the center of the corresponding light receiving section. It is preferable that they are shifted in a corresponding direction. This is because shading can be more reliably suppressed.

For example, when the light incident on the amplification type solid-state imaging device diverges, the center of the microlens is shifted from the center of the corresponding light receiving portion in the direction toward the center of the imaging region. Is preferred. Further, when the incident light to the amplification type solid-state imaging device converges, the center of the microlens may be shifted from the center of the corresponding light receiving unit toward the peripheral part of the imaging region. preferable.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an example of an amplification type solid-state imaging device according to the present invention will be described.

The amplifying solid-state imaging device has an imaging area in which a plurality of pixels are arranged, and a non-imaging area in which peripheral circuits for driving the pixels are arranged. Hereinafter, the structure of the imaging region will be described.

In the image pickup area, a plurality of pixels are arranged as described above. Each of the pixels includes a light receiving unit for performing photoelectric conversion and an amplifier circuit for amplifying a signal generated by the photoelectric conversion of the light receiving unit. Further, the amplification circuit usually includes a plurality of MOS transistors.

FIG. 1 is a sectional view showing an example of an amplification type solid-state imaging device according to the present invention, and shows the structure of an imaging region.

A plurality of light receiving sections 2 corresponding to the number of pixels are formed in a semiconductor substrate 1. The light receiving section 2 includes a semiconductor substrate 1
On the surface, they are arranged in a matrix with a constant arrangement pitch.

Although not shown, a plurality of MOS transistors are formed on the semiconductor substrate 1 around each light receiving section 2. These MOS transistors are electrically connected to each other via a plurality of light-shielding films 4 described later.
It constitutes an amplifier circuit. Note that the configuration of the MOS transistors is not particularly limited, and can be determined as appropriate according to the circuit structure of the amplifier circuit formed in the pixel.

A plurality of light-shielding layers 4 are formed above the semiconductor substrate 1 (hereinafter, for each light-shielding layer, a “first light-shielding layer” and a “second light-shielding layer” in this order from the semiconductor substrate side). The light-shielding layer farthest from the semiconductor substrate is referred to as "the uppermost light-shielding layer."
The number of light-shielding layers 4 can be appropriately determined according to the circuit structure of the amplifier circuit formed in the pixel.
Layers, preferably three layers. The thickness of each light shielding layer 4 is, for example, 100 to 1000 nm, preferably 400 to 1000 nm.
800 nm. The layer thickness of all the light shielding layers 4
It may be the same or different.

A plurality of openings are formed in each light shielding layer 4 so as to correspond to each of the light receiving sections 2. The configuration of the openings will be described later in detail.

On each light shielding layer 4, an interlayer insulating film 3 is formed. The thickness of each interlayer insulating film 3 is, for example, 300 to 12
00 nm, preferably 600-1000 nm. The layer thickness may be the same or different for all the interlayer insulating films 3.

Further, a plurality of microlenses 5 are formed on the uppermost interlayer insulating film so as to correspond to each of the light receiving sections 2. The distance (Hm) from the light receiving unit 2 (the surface of the semiconductor substrate 1) to the microlens 5 is, for example, 2 to 10 μm.
m, preferably 3 to 7 μm. The arrangement of the microlenses 5 will be described later in detail.

Next, the configuration of the openings formed in the light shielding layer 4 and the arrangement of the microlenses 5 will be described with reference to FIGS. FIG. 2 is a plan view schematically showing the arrangement of openings and microlenses formed in the uppermost light-shielding layer. 1 and 2, the same parts are denoted by the same reference numerals.

At least the opening in the uppermost light-shielding layer and the microlens 5 are arranged so as to be displaced from the light-receiving section 2 in the periphery of the imaging area. The direction of the displacement can be determined according to the optical path of the light incident on the solid-state imaging device. For example, as shown in FIG. 3, when the exit pupil is located above the solid-state imaging device 10 (on the side of the microlens), the light incident on the solid-state imaging device 10 is divergent light. Hereinafter, such a case will be described as an example.

The opening formed in the uppermost light shielding layer is such that the center of the opening and the center of the light receiving section 2 are located on the same straight line perpendicular to the surface of the semiconductor substrate 1 in the center of the imaging region. In the peripheral portion of the imaging region, the center of the opening is located closer to the center of the imaging region than the center of the light receiving unit 2. The positional displacement between the opening and the light receiving unit 2 is set so as to gradually increase from the center of the imaging area toward the periphery.

Preferably, not only the uppermost light shielding layer,
Similarly, the other light-shielding layers are set so that the positional deviation between the opening and the light-receiving portion gradually increases from the center to the periphery of the imaging region. However, as for the first light-shielding layer, it is preferable that the center of the opening and the center of the light-receiving section 2 are located on the same straight line perpendicular to the surface of the semiconductor substrate even in the peripheral portion of the imaging region.

At this time, the position shift of the opening corresponding to the same light receiving portion (excluding the light receiving portion at the center of the imaging area) is as follows.
From the lower light shielding layer to the upper light shielding layer,
It is set to become gradually larger.

That is, the following relationship is established for the positional shift of the opening of each light shielding layer 4 corresponding to the same light receiving portion.

0 ≦ L1 <L2 <... <Ln Here, L1, L2 and Ln are the magnitudes of the positional deviations of the openings in the first light-shielding layer, the second light-shielding layer, and the n-th light-shielding layer, respectively. That's it. Note that the magnitude of the positional deviation is an amount representing the deviation between the center of the light receiving unit and the center of the opening in a direction horizontal to the surface of the semiconductor substrate.

Further, it is preferable that the following relationship be established for the positional deviation of the opening of each light shielding layer 4 corresponding to the same light receiving portion.

L2: H2 = L3: H3 =... = Ln: Hn Here, H2, H3, and Hn are the second light-shielding layer, the third light-shielding layer, and the third light-shielding layer, respectively, from the light receiving portion (the surface of the semiconductor substrate). This is the distance to the n light-shielding layers.

The openings can be arranged in a matrix with a constant arrangement pitch, for example. In this case, as shown in FIG. 2, the arrangement pitch of the openings of the light shielding layer 4 is set to be equal to the center of the arrangement of the openings of the light shielding layer 4 and the center of the arrangement of the light receiving units 2. The above-described positional deviation can be achieved by setting the arrangement pitch of the openings of the light-shielding layer 4 to be smaller than that of the upper light-shielding layer.

The microlenses 5 are arranged so that the positional deviation from the corresponding light receiving section 2 gradually increases from the center to the peripheral portion of the imaging region, similarly to the opening of the light shielding layer 4. The displacement (Lm) of the microlens 5 is larger than the displacement of the opening corresponding to the same light receiving portion (excluding the light receiving portion at the center of the imaging area) formed on the uppermost light shielding layer. Is set to

The micro lenses 5 can be arranged in a matrix with a constant arrangement pitch, for example. In this case, as shown in FIG. 2, the arrangement pitch of the microlenses 5 is made larger than the arrangement pitch of the light receiving units 2 in a state where the center of the arrangement of the microlenses 5 and the center of the arrangement of the light receiving units 2 are matched. By setting the distance smaller than the arrangement pitch of the openings in the uppermost light-shielding layer, the above-described positional deviation can be achieved.

Opening of light shielding layer 4 and micro lens 5
The magnitude of the positional shift is the exit pupil distance (the distance from the exit pupil position to the light receiving unit), the imaging area size (the distance from the light receiving unit located at the center of the imaging area to the light receiving unit located at the extreme end) ) Can be determined as appropriate. It is preferable that the smaller the exit pupil distance and the larger the imaging area size, the larger the positional deviation between the opening and the microlens.

Next, an example of a method for manufacturing the above-described amplification type solid-state imaging device will be described.

First, a silicon substrate such as boron
A p-type well is formed by implanting a type impurity. Next, an n-type impurity such as phosphorus is implanted into the p-type well to form a light receiving section. At this time, an implantation mask in which mask patterns are arranged at a constant arrangement pitch is used.

Further, a plurality of MOS transistors are formed around the light receiving section. The MOS transistor is, for example, p
After an n-type impurity is implanted into the mold well to form a source and a drain, a silicon oxide film is formed by thermal oxidation on a silicon substrate, and further a chemical vapor deposition method (hereinafter referred to as “CV”).
D method ". ) To form a polysilicon film and patterning it to form a gate electrode. Further, a silicon oxide film is formed by a CVD method,
An insulating film is formed so as to cover the gate electrode.

A first light shielding layer is formed on the insulating film. As the first light-shielding layer, for example, a metal such as aluminum or tungsten can be used, and as a film forming method, for example, a sputtering method can be used.
Next, after an opening is formed in the first light shielding layer by etching, an interlayer insulating film is formed over the first light shielding layer. As the interlayer insulating film, for example, a silicon oxide film or the like can be used, and as a film forming method, for example, a CVD method can be used.

The same operation is repeated for a desired number of layers to form a plurality of light shielding layers and interlayer insulating films. At this time, in forming the openings of each light shielding layer, an etching mask having a mask pattern formed at an arrangement pitch smaller than that of the light receiving portion is used. However, as for the first light-shielding layer, it is also possible to use an etching mask in which a mask pattern is formed at the same arrangement pitch as that of the light receiving section.

In the formation of the opening of each light shielding layer,
An etching mask in which mask patterns are arranged at a pitch smaller than the arrangement pitch of the openings in the lower light-shielding layer is used.

Next, a resin layer to be a constituent material of the microlens is formed on the interlayer insulating film. As the resin, for example, an acrylic resin or the like can be used. The thickness of the resin layer is, for example, 0.5 to 3 μm, and preferably 0.5 to 2 μm.

The resin layer is etched and divided according to the number of pixels. At this time, an etching mask in which mask patterns are arranged at an arrangement pitch smaller than the arrangement pitch of the openings in the uppermost light shielding layer is used. Thereafter, the divided resin layer is formed into a lens shape by performing a reflow treatment by heating.

In the above description, the case where the exit pupil is located above the solid-state imaging device has been exemplified. However, the present invention is applied to a case where the exit pupil is located below the solid-state imaging device (semiconductor substrate side). It is also possible.

FIG. 4 is a sectional view showing an example of the structure of an amplification type solid-state imaging device applicable to such a case. 1 and 4, the same parts are denoted by the same reference numerals.

As described above, the direction of the displacement of the opening of the light-shielding layer and the position of the microlens are determined according to the optical path of the light incident on the solid-state imaging device 10. As shown in FIG. 5, when the exit pupil is located below the solid-state imaging device 10,
Light incident on the solid-state imaging device 10 is convergent light, as opposed to the case where the exit pupil is located above the solid-state imaging device.

In this amplification type solid-state imaging device, the opening of each light-shielding layer 4 and the microlens 5 are arranged in the opposite direction to the corresponding light-receiving portion in the direction opposite to the case where the exit pupil is located above the solid-state imaging device. That is, they are arranged so as to be displaced toward the periphery of the imaging region.

The amplification type solid-state imaging device shown in FIG.
It has the same structure as that of FIG. 1 except that the direction of displacement of the opening of the light shielding layer 4 and the position of the microlens 5 are different.

As described above, the light incident on the amplification type solid-state imaging device is incident vertically from the center of the imaging region, but obliquely from the periphery of the imaging region. In addition, since light is incident in an oblique direction, the distance between the light incident point and the center of the light receiving unit increases as the distance from the light receiving unit increases.

In the amplification type solid-state imaging device of the present invention,
In at least the uppermost light-shielding layer of the plurality of light-shielding layers, that is, in the light-shielding layer in which the shift between the incident point and the center of the light-receiving unit is the largest, the position shift between the opening and the light-receiving unit is small, and the center of the incident light is small It is set so as to become smaller as the inclination of the incident light becomes larger, and to become larger as the periphery becomes larger. As a result, for example, as shown in FIGS. 1 and 4, the incident light can be condensed not only at the center but also at the periphery of the imaging region to the light receiving portion without being blocked by the light shielding layer. Therefore, it is possible to suppress the occurrence of shading in the peripheral portion of the output image.

[0057]

As described above, according to the amplification type solid-state imaging device of the present invention, a semiconductor substrate, a plurality of light receiving portions formed in the semiconductor substrate, and a light receiving portion formed above the semiconductor substrate, A plurality of light-shielding layers having a plurality of openings corresponding to each of the light-receiving portions, wherein at least the uppermost light-shielding layer farthest from the semiconductor substrate among the plurality of light-shielding layers, the center of the opening and Since the opening is formed so that the corresponding deviation from the center of the light receiving unit increases from the center of the imaging region toward the periphery, shading in the periphery of the imaging region is suppressed. be able to.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of the structure of an amplification type solid-state imaging device according to the present invention.

FIG. 2 is a plan view schematically showing an example of an arrangement of an opening of a light shielding layer and a microlens.

FIG. 3 is a diagram illustrating a positional relationship between a solid-state imaging device and an exit pupil.

FIG. 4 is a cross-sectional view showing another example of the structure of the amplification type solid-state imaging device according to the present invention.

FIG. 5 is a diagram illustrating a positional relationship between a solid-state imaging device and an exit pupil.

FIG. 6 is a cross-sectional view illustrating a structure of a CCD solid-state imaging device.

FIG. 7 is a cross-sectional view illustrating a structure of a conventional amplification type solid-state imaging device.

[Explanation of symbols]

 1, 21, 31 Semiconductor substrate 2, 22, 32 Light receiving unit 3, 23, 33 Interlayer insulating film 4, 24, 34 Light shielding layer 5, 25, 35 Microlens 10 Amplification type solid-state imaging device

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshikazu Sano 1-1, Sachimachi, Takatsuki-shi, Osaka Matsushita Electronics Co., Ltd. F-term (reference) 4M118 AA06 AB01 BA14 BA30 CA01 CA03 CA17 FA06 GB07 GB11 GB15 GB17 GB20 GD04 GD07 5C024 CX35 EX43 GY01 GY41 GZ34

Claims (5)

[Claims] 1. A semiconductor substrate, a plurality of light receiving portions formed in the semiconductor substrate, a plurality of light shielding layers formed above the semiconductor substrate and stacked on each other, and formed between the light shielding layers. And a light-shielding layer,
An amplifying solid-state imaging device having a plurality of openings formed corresponding to each of the light receiving units, wherein at least an uppermost light-shielding layer farthest from the semiconductor substrate among the plurality of light-shielding layers, The amplification type is characterized in that the opening is formed such that the difference between the center of the opening and the center of the corresponding light receiving unit increases from the center of the imaging region toward the periphery. Solid-state imaging device. 2. The amplifying solid-state imaging device according to claim 1, wherein, in the plurality of light-shielding layers, a shift between a center of the opening and a corresponding center of the light receiving unit increases from a lower layer toward an upper layer. apparatus. 3. When the incident light to the amplification type solid-state imaging device diverges or converges, the center of the opening is oriented with respect to the center of the corresponding light receiving unit in a direction corresponding to the optical path of the incident light. The amplifying solid-state imaging device according to claim 1, which is shifted. And a plurality of microlenses formed above the light-shielding layer so as to correspond to each of the light receiving portions, wherein a difference between the center of the microlens and the center of the corresponding light receiving portion is provided. Is larger from the center of the imaging region toward the periphery, and is larger than the difference between the center of the opening in the uppermost light-shielding layer and the center of the corresponding light-receiving unit. The amplification type solid-state imaging device according to claim 1, wherein the microlens is formed. 5. When the incident light to the amplification type solid-state imaging device diverges or converges, the center of the microlens is positioned with respect to the center of the corresponding light receiving unit in a direction corresponding to the optical path of the incident light. The amplifying solid-state imaging device according to claim 4, which is shifted.