JP2017168757A - Solid-state image sensor and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid-state image sensor that has a color filter in which a finer and thinner color filer layer is achieved with less defects without problems such as color mixture and shape variation in order to meet a progress for making pixels finer.SOLUTION: In a solid-state image sensor in which a plurality of pixels are integrated in a grid pattern, comprises: a photoelectric conversion part sectioned for each of the pixels on at least a semiconductor substrate; and a color filter cell (14a) formed on the semiconductor substrate and formed in a grid pattern above the photoelectric conversion parts. On the underside of the color filter cell, omission parts are provided on peripheral parts or four corners of the grid pattern by level difference parts (21).SELECTED DRAWING: Figure 4

Description

  The present invention relates to a solid-state imaging device in which a color filter is formed and a method for manufacturing the same.

  In a solid-state imaging device, generally, an imaging region in which a plurality of pixels are arranged in a grid in the horizontal direction and the vertical direction is provided on the surface of a substrate. In this imaging region, photoelectric conversion units that receive light from the subject image and generate signal charges are formed so as to correspond to the respective pixels. For example, a photodiode is formed as the photoelectric conversion unit.

  A color filter layer composed of individual color filter cells is provided above the photoelectric conversion unit so as to correspond to each pixel, and the photoelectric conversion unit receives light colored by the color filter layer. It is configured.

  In many cases, a microlens is provided corresponding to each pixel above the color filter layer, and light condensed by the microlens enters the photoelectric conversion unit through the color filter layer. It is configured as follows.

  In recent years, along with the progress of miniaturization of electronic devices with cameras such as digital cameras and mobile phones, and the demand for increasing the number of pixels of a solid-state imaging device, the miniaturization of pixels in the solid-state imaging device has progressed.

  As the pixel miniaturization of the solid-state imaging device progresses, it is necessary to miniaturize the patterning dimension of the color filter layer as well. Further, with the miniaturization, there are problems such as a decrease in light receiving sensitivity characteristic per pixel of the solid-state imaging device and an increase in noise ratio. For this reason, the color filter layer is required to have improved spectral transmittance and a thinner film.

  In order to promote thinning while maintaining or improving the spectral characteristics of the color filter, it is necessary to increase the color material ratio and reduce the other solid content ratio in the solid contents forming the color filter layer. The component to be reduced is a component related to color material dispersion or a component related to photolithography. The reduction in the components related to the dispersion of the color material brings about deterioration of the temporal stability of the color filter material, and therefore cannot be reduced much. Therefore, it is necessary to reduce the amount of the photolithography component. However, the reduction in the amount of the photolithography component has a problem that the patterning property, which is increasing in difficulty due to miniaturization, becomes more difficult.

  As the pixel width dimension is 1.2 μm or less and 1.0 μm or less, the color filter layer maintains the spectral characteristics and the film thickness that is the height dimension is 0.8 μm or less. Thinning is progressing to 0.6 μm or less. Therefore, the color material ratio of the solid content forming the color filter layer is increased, while the total amount of alkali-soluble resin, polysynthetic monomer, photopolymerization initiator, and the like, which are photolithography components, is decreased. As a result, the following problems occur in forming the color filter layer.

  As the pattern becomes finer, the weight of the polysynthetic monomer is decreased, and the amount of the photopolymerization initiator is decreased, it is difficult to control the shape of the color filter layer. In particular, it is difficult to control the cross-sectional shape of the periphery of the color filter cell pattern formed in a lattice shape, and it is particularly difficult to control the cross-sectional shape at the four corners of the color filter cell.

  In general, the color filter repeatedly arranges two or more types of patterns having different transmission spectra to form a lattice-like arrangement. In the first color filter cell formed, if the cross-sectional shape cannot be controlled at the periphery and four corners of the pattern and the rectangularity is poor, the color filter cell formed subsequently or the color filter cell formed thereafter is There are cases where the color filter cell is initially formed on the periphery or four corners of the color filter cell. As a result, the solid-state imaging device has problems such as color mixing, an increase in noise, and sensitivity variations among pixels.

  In a general Bayer arrangement as a color arrangement of a solid-state imaging device, a shape of a non-isolated pattern is often taken by connecting GREEN color filter cells at a bridge portion as a color filter cell to be formed first. However, as described above, if the cross-sectional shape of the color filter cell cannot be sufficiently controlled, the height of the bridge portion varies. As a result, problems such as variation in characteristics of the solid-state imaging device and induction of color mixing by the color filter formed subsequently arise.

JP 2007-287871 A JP 2012-174792 A

  The present invention has been made in view of the above problems, and in accordance with the progress of pixel miniaturization, miniaturization and thinning of the color filter layer have been realized with reduced defects and reduced problems such as color mixing and shape variation. A solid-state imaging device having a color filter is provided.

  In order to solve the above problems, one of the representative solid-state imaging devices according to the present invention includes a photoelectric conversion unit arranged in a grid pattern on a substrate, a photoelectric conversion unit disposed above the photoelectric conversion unit, and a flat upper surface. And a solid-state imaging device including a color filter cell having a missing portion in a peripheral portion of a lower surface.

  In addition, one of the typical solid-state imaging device manufacturing methods for manufacturing such an imaging device includes a step of forming a planarization film on a semiconductor substrate in which photoelectric conversion units are arranged in a grid, A step of forming a stepped portion on the periphery of the photoelectric conversion portion, and a step of forming a color filter cell formed first with the stepped portion overlapping. It is a manufacturing method of an apparatus.

According to the present invention, it is possible to form a color filter cell for a pixel having a fine size with a good cross-sectional shape and less variation, and a good color filter layer can be obtained. As a result, a solid-state imaging device having fine pixels can be realized with little characteristic variation and low defects.
Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

It is explanatory drawing which shows an example of the pixel arrangement | positioning figure of a solid-state imaging device. FIG. 2 is a schematic cross-sectional view of the solid-state imaging device at A-A ′ illustrated in FIG. 1. It is a cross-sectional schematic diagram of the conventional solid-state imaging device in B-B 'described in FIG. It is a cross-sectional schematic diagram of the solid-state imaging device of the present invention at B-B ′ described in FIG. 1. It is a cross-sectional schematic diagram of the solid-state imaging device of the present invention at B-B ′ described in FIG. 1. It is a cross-sectional schematic diagram of the solid-state imaging device of the present invention at B-B ′ described in FIG. 1. It is a cross-sectional schematic diagram of the solid-state imaging device of the present invention at B-B ′ described in FIG. 1. It is a perspective view of the color filter cell in case the shape of a missing part is hemispherical. It is a perspective view of a color filter cell in case the shape of a missing part is a rectangle type. It is the perspective view which reversed the top and bottom of the color filter cell when the rectangular-shaped omission extends to the periphery of the color filter cell. It is explanatory drawing which shows an example of the pixel arrangement | positioning figure of a solid-state imaging device. FIG. 12 is a schematic cross-sectional view of a conventional solid-state imaging device at B-B ′ shown in FIG. 11. It is a cross-sectional schematic diagram of the solid-state imaging device of the present invention at B-B ′ shown in FIG. 11. It is a cross-sectional schematic diagram of the solid-state imaging device of the present invention at B-B ′ shown in FIG. 11. It is a cross-sectional schematic diagram of the solid-state imaging device of the present invention at B-B ′ shown in FIG. 11.

  Embodiments of the present invention will be described below with reference to the drawings. First, each direction related to the solid-state imaging device to be described below is defined as a width direction that is parallel to a plane in which pixels are arranged in a grid, and a normal direction to the plane in which the pixels are arranged It is defined as the height direction.

FIG. 1 shows an example of a pixel arrangement diagram of the solid-state imaging device.
In FIG. 1, color filter cells are arranged corresponding to the respective pixels 10 (A), 10 (B), 10 (C), and 10 (D) arranged in a grid pattern. Yes. In the description of the embodiment of the present invention, the case where the color filter cells are formed in the order corresponding to the pixels 10 (A), and subsequently 10 (B), 10 (C), and 10 (D) will be described. The order of formation is not limited to this. If color filter cells having two or more types of spectra are arranged, there is no limitation on the combination of colors and the order of formation. For example, 10 (A) and 10 (D) are the first color filter cells to be formed. It is possible to simultaneously form the pixels corresponding to these pixels.

First, a cross-sectional structure of a solid-state imaging device in a conventional example will be described with reference to FIG. 2 is a cross-sectional view taken along line AA ′ of the solid-state imaging device 100 shown in FIG.
A photodiode 12 made of CMOS or CCD is formed on the semiconductor substrate 11 as a light receiving element constituting the light receiving portion. A silicon oxide film or a silicon nitrogen oxide film (not shown) is formed on the surface of the semiconductor substrate 11. A light shielding film 17 made of a metal material and a planarizing layer 13 made of a transparent resin are formed on the semiconductor substrate 11. Corresponding to the photodiode, a color filter layer 14 made of a resin in which a color material such as a pigment or a dye is dispersed is formed on the planarizing layer 13. The color filter layer 14 includes individual color filters. The cell 14 (a), 14 (b), and 14 (c) are comprised. A smoothing layer 15 made of a transparent resin is formed above the color filter layer 14, and a microlens 16 is formed thereon corresponding to the photodiode. Here, the color filter cell formed first in the color filter layer 14 is 14 (a), and the color filter cell formed later is 14 (b).

Next, another cross-sectional structure of the solid-state imaging device in the conventional example will be described with reference to FIG. 3 is a cross-sectional view taken along line BB ′ of the solid-state imaging device 100 shown in FIG.
In the conventional solid-state imaging device 102 shown in FIG. 3, the first formed color filter cell 14 (a) is in contact with the adjacent color filter cell, in particular, the four corner portions of the color filter cell arranged in a grid pattern. However, the cross-sectional shape is not formed as an accurate rectangular shape. For this reason, the film thickness in the height direction is reduced at the four corners of the color filter cell 14 (a). In addition, the decrease in film thickness tends to be in a state in which there is a large variation for each color filter cell. For this reason, when the color filter cell 14 (b) is formed, a phenomenon such as the color filter cell 14 (b) riding on the four corners of the color filter cell 14 (a) occurs, and color mixing and variations in sensitivity between pixels occur. Such problems are likely to occur.
Such a phenomenon may occur in the cross-sectional portion of the peripheral portion of the color filter cell as shown in FIG. 2 along the line AA ′ in FIG. 1, but BB ′ in FIG. 1 shown in FIG. 3. This can occur more noticeably at the cross-section of the line, that is, at the four corners of the color filter cells arranged in a grid.

Example 1
Next, an example of the solid-state imaging device according to the first embodiment of the present invention will be described with reference to FIG. FIG. 4 is an example of a cross-sectional view of the solid-state imaging device of the present invention taken along line BB ′ shown in FIG. A photodiode 12 made of CMOS or CCD is formed on the semiconductor substrate 11 as a light receiving element constituting the light receiving portion. A silicon oxide film or a silicon nitrogen oxide film (not shown) is formed on the surface of the semiconductor substrate 11. A light shielding film 17 made of a metal material and a planarizing layer 13 made of a transparent resin are formed on the semiconductor substrate 11. On the flattening layer 13, step portions 21 are formed at contact points between color filter cells to be formed later, particularly at positions corresponding to the four corner portions of the color filter cells arranged in a lattice pattern.

Corresponding to the photodiode, a color filter layer 14 made of a resin in which a color material such as a pigment or a dye is dispersed is provided on the planarizing layer 13, and the individual color filter cells 14 (a), 14 ( b) and 14 (c).
A smoothing layer 15 made of a transparent resin is formed above the color filter layer 14, and a microlens 16 is formed thereon corresponding to the photodiode.

  As a result, in the solid-state imaging device 201 of the present invention shown in FIG. 4, the peripheral portion of the color filter cell arranged in a grid pattern, or the portion corresponding to the four corners of the peripheral portion, has the same shape as the stepped portion 21. Missing portion 23 is provided. Due to the presence of the missing portion 23, the film thickness above the missing portion of the color filter cell is thinner than other portions, specifically, the pixel central portion.

In the case of providing openings using photolithography, when the aspect ratio (vertical / horizontal opening ratio) increases, it becomes difficult to form an opening pattern accurately, and as the film thickness increases, it becomes difficult to form an accurate pattern. Further, when pattern formation is performed using a photolithography processing technique, if a baking process is performed after the development process, the film thickness is often reduced toward the peripheral portion, and a predetermined film thickness cannot be obtained in many cases.
For this reason, in the color filter cell of this embodiment, in order to ensure the accuracy of pattern formation, the thickness of the peripheral portion of the color filter cell, particularly the four corner portions, where the accuracy of the pattern is likely to deteriorate, is set to be smaller than that of other portions. Thinned.
Furthermore, when applying a resist by spin coating, there is a tendency that the resist material is applied thicker in the portion having the protrusion below, compared to other portions, and this also causes the subsequent baking treatment. In this case, the influence of film thickness degeneration can be alleviated, and the accuracy can be further improved.
For these reasons, an accurate and fine color filter cell can be obtained in this embodiment.

Even if the color filter cell 14 (a) formed first is a peripheral part or four corners thereof, the upper surface can be manufactured in a flat shape. The upper surface of the cell 14 (b) is flat and can be manufactured in a shape with excellent rectangularity.
This is an effect that the missing portion 23 is provided in the color filter cell by the step portion 21 formed above the semiconductor substrate 11. Since each color filter cell can be formed in a cross-sectional shape with excellent rectangularity, a good solid-state imaging device free from variations can be obtained.

  In FIG. 4, as an example of the solid-state imaging device, the shape of the stepped portion 21 (same shape as the missing portion 23) has been described as a hemispherical shape, but the shape of the stepped portion (the shape of the missing portion) is As long as the step (missing portion) is formed so that the effect of the present invention can be exerted, the shape such as a rectangular shape, a conical shape, or a cylindrical shape as shown in FIGS. Any shape is acceptable.

4 shows an example in which the stepped portion 21 is formed on the planarizing layer 13, but as shown in FIG. 7, the four corners of the light shielding film 17 formed as a lower layer than the planarizing layer 13 are shown. A form in which the step portion 21 is formed by forming the shape into a convex shape may be used.
When the step portion 21 is formed as a part of the light shielding film, a planarizing film is formed on the light shielding film. If the planarizing film is formed thinner than the stepped portion formed by the light shielding film, the shape of the stepped portion is generally maintained in the planarized film even after the planarized film is formed, and the step remains.

  Further, the stepped portion 21 is not limited to those formed at locations corresponding to the vicinity of the four corners of the color filter cell. FIG. 8 is a perspective view of the color filter cell when the shape of the missing portion 23 is hemispherical. FIG. 9 is a perspective view of the color filter cell when the shape of the missing portion 23 is rectangular.

FIG. 10 is a perspective view of the color filter cell when the rectangular missing portion extends to the periphery of the color filter cell. The step portion 21 may be formed such that the missing portion 23 of the color filter cell extends to the peripheral portion of the color filter cell. In this case, the step portion 21 having the same shape as the missing portion 23 is formed in a lattice shape. The Rukoto.
In FIG. 10, in order to show the shape of the color filter cell in an easy-to-understand manner, unlike FIG. 8 and FIG.

  As described above, the color filter cell according to the present embodiment has a rectangular shape that is liable to collapse, and the peripheral portion of the color filter cell, in particular, the missing portions at the four corners are provided, and the thickness of the color filter cell at that portion is reduced. Therefore, the pattern formation accuracy is improved and an accurate color filter cell as designed can be formed.

(Example 2)
Hereinafter, a case where the present invention is applied to the Bayer array will be described.
FIG. 11 shows an example of the Bayer array of the solid-state imaging device. In this example, color filter cells are arranged corresponding to the pixel 10 (A), the pixel 10 (B), and the pixel 10 (C), and the color filter cell is changed to the pixel 10 (A) and subsequently 10 (B ) The case of forming in the order corresponding to 10 (C) will be described, but the order of forming is not limited to this. As long as color filter cells having two or more types of spectral characteristics are arranged, any combination of colors and the order of formation can be applied.

First, a cross-sectional structure of a solid-state imaging device in a conventional example will be described with reference to FIG. 12 is a cross-sectional view taken along line BB ′ of the solid-state imaging device 300 shown in FIG. A photodiode 12 made of CMOS or CCD is formed on the semiconductor substrate 11 as a light receiving element constituting the light receiving portion. A silicon oxide film or a silicon nitrogen oxide film (not shown) is formed on the surface of the semiconductor substrate 11. A light shielding film 17 made of a metal material and a planarizing layer 13 made of a transparent resin are formed on the semiconductor substrate 11.
A color filter layer 14 made of a resin in which a color material such as a pigment or a dye is dispersed is formed on the planarizing layer 13 corresponding to the photodiode.

  In the cross-sectional portion taken along line B-B ′ in FIG. 11, the four corners of the color filter cells corresponding to the pixels 10 (A) arranged in a lattice shape are connected to each other by a bridge portion. In the case of the Bayer array, generally, the color filter cell is formed of three types of R (red), G (green), and B (blue), and G is arranged more than R and B. Yes. The number of color filter cells corresponding to G (green) to be formed first occupies about half of all the pixels, and the G (green) color filter cells are connected to each other at the bridge portions at the four corners. This is due to the fact that

  For this reason, in the cross-sectional structure shown in FIG. 12, the color filter cell 14 (a) continues in the color filter layer 14 via the bridge portion. A smoothing layer 15 made of a transparent resin is formed on these color filter layers, and a microlens 16 is formed thereon corresponding to the photodiode.

In such a conventional example, the first formed color filter cells 14 (a) are arranged in a checkered pattern, but at the periphery of the color filter cells and at the four corners of the color filter cells. In the corresponding bridge portion, it is difficult to form the cross-sectional shape into an accurate rectangular shape. In particular, the film thickness of the bridge portion at the four corners is smaller than the design value, and the film thickness and shape of the bridge portion are likely to vary.
In such a situation, when the color filter cell 14 (b) is formed as a subsequent process, the color filter cell 14 (b) is formed on the bridge portion of the color filter cell 14 (a) that has become smaller than the design value. Phenomenon such as getting on occurs. As a result, problems such as color mixing and pixel-to-pixel sensitivity variations tend to occur in the imaging apparatus.

  Next, an example of a solid-state imaging device according to the second embodiment will be described with reference to FIG. FIG. 13 is an example of a cross-sectional view of the solid-state imaging device of the present invention taken along line B-B ′ shown in FIG. 11. As in the conventional example, a photodiode 12 made of CMOS or CCD is formed on the semiconductor substrate 11 as a light receiving element, and a silicon oxide film or a silicon nitrogen oxide film (not shown) is formed on the surface of the semiconductor substrate 11. ing. Further, a light shielding film 17 made of a metal material and a planarizing layer 13 made of a transparent resin are formed on the semiconductor substrate 11. Further, a color filter layer 14 made of a resin in which a color material such as a pigment or a dye is dispersed is formed on the planarizing layer 13 corresponding to the photodiode.

  Here, in the embodiment disclosed in FIG. 13, stepped portions 21 are formed at locations corresponding to the four corners of the checkered pattern of the color filter cell 14 (a) on the planarizing layer 13.

  In FIG. 13, as an example of the solid-state imaging device, the structure in which the step portion 21 is formed on the planarizing layer 13 is illustrated. However, the step portion 21 may be formed on the lower surface of the color filter layer. May be formed. Moreover, you may produce as a part of light shielding film formed in the lower part from the color filter layer which is not shown in figure.

  Further, the shape of the stepped portion 21 is not limited to that shown in FIG. 13, and it is sufficient that the stepped portion is formed so that the effect of the present invention can be exhibited. It may be a columnar shape or an arbitrary shape.

  In the solid-state imaging device 401 of the present invention shown in FIGS. 13 to 15, as in the case of the first embodiment, the color filter cells arranged in a grid form correspond to the peripheral part or four corners of the peripheral part. A missing portion 23 caused by the stepped portion 21 is provided in the portion. Since the missing portion 23 exists, the film thickness above the missing portion of the color filter cell is thinner than other portions, specifically, the pixel central portion.

  For this reason, the color filter cell 14 (a) formed first can be formed in a cross-sectional shape excellent in rectangularity, and a flat cross-sectional shape can be obtained also in the bridge portion. In the subsequent color filter cell 14 (b), since the color filter cell 14 (a) is formed with high accuracy, the color filter cell 14 (b) corresponds to the color filter cell 14 (a). There is no riding on the bridge. As a result, a good solid-state imaging device without variations can be obtained.

Hereinafter, selection of the shape of the stepped portion 21 and the missing portion 23 of the color filter cell, other materials, and the manufacturing method in the present invention will be described.
The step portion 21 in the present invention only needs to form an appropriate structure for maintaining the rectangularity of the color filter cell when the color filter layer 14 is formed, and the material can be formed as a solid as a structure. There is no particular limitation. For example, a single-layer film such as silicon nitride (SiN), silicon oxide (SiO ₂ ), and silicon oxynitride (SiON) used as a planarizing layer, or a stacked film thereof may be used. Moreover, the material structure which has transparency and heat resistance of the material structure centering on resin components, such as an acrylic resin, a styrene resin, and an epoxy resin, is also applicable.

  The shape of the stepped portion 21 in the present invention can be made more effective by appropriately selecting according to the patterning performance of the color filter material, and does not need to have a specific structure. As the structure, for example, a structure in which the film thickness is maximized at the lattice pattern contact 24 (see FIG. 11) at the four corners of the pixel is effective. Further, it is possible to obtain an effect even in a hemispherical shape or a rectangular shape.

  The pixel size in the present invention is desirably 0.4 μm to 1.2 μm, and the film thickness of the color filter layer 14 is desirably 0.1 to 0.8 μm.

  In this case, the height of the step portion 21 is preferably 50 nm to 300 nm. Moreover, it is preferable that the dimension of the width | variety of the level | step-difference part 21 is 60 nm-300 nm.

Therefore, the height of the step portion 21 in the present invention is preferably 6% to 50% of the height of the color filter cell.
In addition, the width of the stepped portion is preferably 5% to 25% with respect to the width of the color filter cell.
That is, as the shape of the color filter cell, the maximum height is 6% to 50% of the height of the color filter cell in the peripheral portion of the color filter cell, and the width dimension from the peripheral portion of the color filter cell toward the central portion. In this case, it is desirable that a missing portion of 2.5% to 12.5% of the width dimension of the color filter cell is provided.

  Conventionally used photolithography, etching, and printing methods can be applied to the formation of the stepped portion 21, the color filter layer 14, and the microlens 16.

  As for the semiconductor substrate 11 and the photodiode 12 in the present invention, configurations and materials conventionally used as solid-state imaging devices can be appropriately selected. In addition, for the light shielding film in the present invention, materials conventionally used as solid-state imaging devices such as tungsten, titanium, and aluminum can be appropriately selected.

The planarizing layer 13 in the present invention is composed of, for example, a single layer film such as silicon nitride (SiN), silicon oxide (SiO ₂ ), and silicon oxynitride (SiON) or a laminated film thereof. In addition, materials with transparency and heat resistance that are mainly composed of resin components such as acrylic resins, styrene resins, and epoxy resins can be applied. These materials have been used as solid-state imaging devices. Can be suitably selected.

  Regarding the material of the color filter layer in the present invention, a composition containing an organic pigment or dye, a dispersant, an alkali-soluble resin, a polymerizable monomer, a photopolymerization initiator, and a solvent conventionally used for forming the color filter layer is used. It can select suitably, It can utilize also about the material which added the additive used conventionally as needed. When using an organic pigment, the average particle size of the pigment is desirably 20 nm to 120 nm.

  As the material of the light shielding film 17 in the present invention, a material such as a film of metals such as aluminum (Al), tungsten (W), and copper (Cu) is also applicable.

About the material of the smoothing layer 15 in this invention, it becomes a material structure centering on resin components, such as an acrylic resin, a styrene resin, an epoxy resin, and the material structure which has transparency and heat resistance after film formation Thus, materials that have been conventionally used as solid-state imaging devices can be suitably selected.
In addition, as for the material of the microlens, a conventionally used material adapted for forming a microlens can be applied.

(Example 3)
Below, the Example is described about the manufacturing method of the solid-state imaging device of this invention.
As the photoelectric conversion unit, a semiconductor substrate in which a plurality of photodiodes made of CMOS as a light receiving element are arranged in a lattice shape so as to form a Bayer array, and a silicon oxide film is formed on the surface of the semiconductor substrate is used. The period of the pixels of the light receiving element is 1.1 μm.

  A material composed of a styrene-based transparent resin is applied by spin coating, and after pre-baking, a baking process is performed at 200 ° C. for 10 minutes to form a planarization film. The thickness of the planarizing film was 40 nm.

  First, a process for forming a step portion on a semiconductor substrate will be described. First, a resist composed of an acrylic transparent resin, an acrylic polymerizable monomer, and an oxime ester initiator is applied by spin coating. After aligning with the pixels, exposure is performed through a photomask, and then development is performed with an alkaline developer, so that the peripheral portion of each photoelectric conversion unit arranged in the Bayer array or a lattice of the peripheral portions A pattern for providing a step portion at a portion corresponding to the four corners of the shape is formed. Then, a baking process is performed at 200 degreeC for 10 minutes, and a level | step difference part is formed. The shape of the stepped portion was a hemispherical shape with the highest thickness of the contact portions at the four corners (lattice pattern contact points 24), and the thickness of the highest portion was 185 nm and the width dimension was 150 nm.

  Next, a process in the case of forming a G (green) color filter cell as the first formed color filter cell will be described. It consists of Pigment Green 58, Pigment Yellow 150, a resin-type dispersant, an acrylic transparent resin, an acrylic polymerizable monomer, and an oxime ester initiator so as to cover the stepped portion formed in the previous step. Apply negative pigment dispersion resist with green spectrum. After aligning with the pixel, exposure is performed through a photomask, and then development is performed with an alkaline developer, so that it corresponds to the G (green) color filter cell with an overlap with the stepped portion. A pattern is formed. Thereafter, a baking treatment is performed at 200 ° C. for 10 minutes to complete a G (green) color filter cell. The film thickness was 0.59 μm and the line width was 1.101 μm. A negative pigment dispersion resist having a green spectrum uses a material having a pigment ratio of 62.1% in the solid content.

  Next, a process of forming an R (red) color filter cell as a color filter cell to be formed later will be described. A negative pigment dispersion resist having a red spectrum composed of Pigment Red 254, Pigment Yellow 139, a resin-type dispersant, an acrylic transparent resin, an acrylic polymerizable monomer, and an oxime ester-type initiator is applied by spin coating. . After alignment with the pixels, exposure is performed through a photomask, and then development processing is performed with an alkaline developer, whereby a predetermined pattern to be formed later is formed. Thereafter, a baking process is performed at 200 ° C. for 10 minutes to form a color filter layer. The film thickness was 0.62 μm and the line width was 1.099 μm. A negative pigment dispersion resist having a red spectrum uses a material having a pigment ratio of 66.4% in the solid content.

  Next, a process of forming a B (blue) color filter cell as a color filter cell to be formed later will be described. Application of negative pigment dispersion resist with blue spectrum consisting of Pigment Blue 15: 6, Pigment Violet 23, resin type dispersant, acrylic transparent resin, acrylic polymerizable monomer, oxime ester type initiator by spin coating method I do. A predetermined pattern is formed by aligning with pixels and performing exposure through a photomask, followed by development with an alkaline developer. Thereafter, a baking process is performed at 200 ° C. for 10 minutes to form a color filter layer. The film thickness was 0.61 μm, and the line width was 1.100 μm. Incidentally, a material having a pigment ratio of 52.5% in the solid content of the negative type pigment dispersion resist having a blue spectrum is used.

  A thermosetting acrylic resin having a flattening effect on these three color filter cells and containing an ultraviolet absorber is applied by a spin coating method, followed by baking at 200 ° C. for 10 minutes to form a film. The coating was formed with a thickness of about 100 nm.

  Subsequently, in order to form a microlens above the R (red), G (green), and B (blue) color filter layers, a negative pigment dispersion resist is applied by spin coating. A predetermined pattern is formed by aligning with pixels and performing exposure through a photomask, followed by development with an alkaline developer. Here, a gray-tone mask is used as the photomask, and the mask pattern is formed using concentric gradations so that the transmitted light at the center of the lens is the strongest and the transmitted light becomes weaker toward the end of the lens. went. Thereafter, a baking process is performed at 230 ° C. for 10 minutes to form a microlens. The film thickness of the top portion of the formed microlens was 0.42 μm.

  The formation result of the G (green) color filter cell formed first was confirmed by cross-sectional SEM observation and a contact-type film thickness meter. Twenty in-plane measurements were made on the depth of the depressions in the bridge when viewed from the height of the center of the pixel. As a result, in this embodiment, the average depth of the dent at the bridge portion is 45.0 nm and the standard deviation is 3.9 nm, and a satisfactory result can be obtained as the dent at the bridge portion of the color filter. Further, from the observation result after forming the third color filter cell, no color overlap was observed at the bridge portion.

  Note that if the depth of the recess in the bridge portion is large, it may cause color overlap in the bridge portion when the second color filter cell is formed. Therefore, the depth of the recess in the bridge portion is preferably 100 nm or less. Further, the lower the recess depth, the flatter the upper surface side of the color filter layer can be formed, and the adverse effect due to the recess depth of the bridge portion on the sensitivity characteristics of the image sensor can be reduced.

  The variation in the depth of the dent at the bridge portion is desirably 15 nm or less as a standard deviation. The smaller the variation, the more the adverse effect on the variation in sensor sensitivity characteristics can be reduced.

Example 4
Except for the shape of the stepped portion, it was formed in the same manner as in Example 3, and the shape of the stepped portion was a square cubic structure when viewed from above, with a film thickness of 150 nm and a dimension of 130 nm.

  The formation result of the color filter cell of G (green) was confirmed by cross-sectional SEM observation and a contact-type film thickness meter. Twenty in-plane measurements were made on the depth of the depressions in the bridge when viewed from the height of the center of the pixel. As a result, the average depth of the recess is 46.1 nm, and the standard deviation is 9.1 nm, and favorable results can be obtained as the recess of the bridge portion of the color filter. Further, from the observation result after forming the third color filter layer, no color overlap was observed at the bridge portion.

(Example 5)
Formed in the same manner as in Example 3 except for the shape of the stepped portion, the shape of the stepped portion 21 is a conical structure with the highest thickness of the contact portions at the four corners, the thickness of the highest portion is 165 nm, and the width dimension is 130 nm It was.

  The formation result of the color filter cell of G (green) was confirmed by cross-sectional SEM observation and a contact-type film thickness meter. Twenty in-plane measurements were made on the depth of the depressions in the bridge when viewed from the height of the center of the pixel. As a result, the average depth of the recess is 41.9 nm, and the standard deviation is 4.2 nm, and a satisfactory result can be obtained as the recess of the bridge portion of the color filter. Further, from the observation result after forming the third color filter layer, no color overlap was observed at the bridge portion.

(Example 6)
Except for the shape of the stepped portion, it was formed in the same manner as in Example 3. The stepped portion 21 had a cylindrical structure with a film thickness of 150 nm and a width dimension of 140 nm.

  The formation result of the color filter cell of G (green) was confirmed by cross-sectional SEM observation and a contact-type film thickness meter. Twenty in-plane measurements were made on the depth of the depressions in the bridge when viewed from the height of the center of the pixel. As a result, the average depth of the recesses is 58.9 nm, and the standard deviation is 7.6 nm, and favorable results can be obtained as the recesses in the bridge portion of the color filter. Further, from the observation result after forming the third color filter layer, no color overlap was observed at the bridge portion.

(Comparative Example 1)
In Example 3, the step of forming the step portion was omitted, and the other steps were performed in the same manner, and G (green), R (red), and B (blue) color filter cells were sequentially formed.

  The formation result of the color filter cell of G (green) was confirmed by cross-sectional SEM observation and a contact-type film thickness meter. Twenty in-plane measurements were made on the depth of the depressions in the bridge when viewed from the height of the center of the pixel. As a result, the average depth of the recesses is 214 nm, the standard deviation is 31.3 nm, the coefficient of variation is 14.6%, the film thickness of the bridge portions formed at the four corners is thin, and the film thickness varies. It was confirmed. Moreover, when the result after forming the 3rd color filter layer was observed, it was confirmed that the 3rd color filter has overlapped and formed in the bridge | bridging part.

Below, the comparison table | surface of the evaluation result of the color filter layer manufactured by Example 3 to Example 6 and the comparative example is shown.

  As is clear from the above results, by using the color filter cell in the present invention, the flatness of the color filter cell can be remarkably improved in the solid-state imaging device, and the region or bridge where the color filter cells are in contact with each other. In a region such as a portion, there is no color overlap and a good solid-state imaging device can be obtained.

In addition, this invention is not limited to an above-described Example, Various modifications are included. For example, the order of forming color filter cells corresponding to RGB can be arbitrarily changed. Further, for example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described.
It is also possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and to add the configuration of another embodiment. Furthermore, it is possible to add, delete, replace, change the size, shape, etc. of other configurations for a part of the configuration of each embodiment.

10: Pixel of solid-state imaging device 11: Semiconductor substrate 12: Photodiode 13: Flattening layer 14: Color filter layer 14 (a): Color filter cell 14 (b): Color filter cell 15: Smoothing layer 16: Microlens 17: light shielding film 21: stepped portion 22: peripheral portion 23: missing portion 24: lattice pattern contact

Claims (10)

Photoelectric conversion units arranged in a grid on the substrate;
A color filter cell that is disposed above the photoelectric conversion unit, has a flat upper surface, and has a missing portion in the periphery near the lower surface;
A solid-state imaging device. In claim 1,
The peripheral portion is a solid-state imaging device that is near the four corners of a color filter cell.   3. The solid-state imaging device according to claim 1, wherein a height of the missing portion is 6% to 50% of a height of the color filter cell.   4. The solid-state imaging device according to claim 1, wherein a width dimension of the missing portion is 2.5% to 12.5% of a width dimension of the color filter cell. 5.   5. The solid-state imaging device according to claim 1, wherein the height of the missing portion is maximized at lattice pattern contacts at four corners.   6. The solid-state imaging device according to claim 2, wherein the shape of the missing portion is a hemispherical shape.   6. The solid-state imaging device according to claim 2, wherein the shape of the missing portion is a rectangular shape. Forming a planarization film on a semiconductor substrate in which photoelectric conversion portions are arranged in a grid pattern;
Forming a stepped portion on the planarizing film and in the periphery of the photoelectric conversion portion;
A step of forming a color filter cell to be formed first, with the stepped portion overlapping.
A method for manufacturing a semiconductor imaging device comprising: 9. The method of manufacturing a semiconductor imaging device according to claim 8, wherein the peripheral portion of the photoelectric conversion portion is a portion corresponding to four corners of the color filter cells arranged in a lattice pattern. Forming a light-shielding film on the semiconductor substrate in which the photoelectric conversion units are arranged in a lattice shape so that a stepped portion is formed around the photoelectric conversion unit;
Forming a color filter cell formed first on the planarizing film having the stepped portion, with the stepped portion overlapping;
A method for manufacturing a semiconductor imaging device comprising:

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