JP7508779B2 - Solid-state imaging device and its manufacturing method - Google Patents

Description

The present invention relates to technology relating to solid-state imaging elements that use photoelectric conversion elements such as CCDs and CMOSs.

In recent years, solid-state imaging elements such as CCDs (charge-coupled devices) and CMOSs (complementary metal-oxide semiconductors) used in digital cameras have become increasingly finer and more pixelated, with the pixel size of some of the finest elements now reaching a level of less than 1.4 μm x 1.4 μm.

A solid-state imaging element has a photoelectric conversion element and a pair of color filter patterns to achieve color imaging. The area (aperture) where the photoelectric conversion element of the solid-state imaging element contributes to photoelectric conversion depends on the size and number of pixels of the solid-state imaging element. The aperture is limited to about 20-50% of the total area of the solid-state imaging element. Since a small aperture directly leads to a decrease in the sensitivity of the photoelectric conversion element, it is common for solid-state imaging elements to have microlenses for focusing light formed on the photoelectric conversion element to compensate for the decrease in sensitivity.

In recent years, image sensors using back-illumination technology have been developed, allowing the aperture of the photoelectric conversion element to be 50% or more of the total area of the solid-state imaging element. However, in this case, there is a possibility that light from adjacent color filters may leak into the color filter, so it is necessary to form microlenses of an appropriate size and shape.

A method for forming such a color filter pattern on a solid-state imaging element typically involves forming the pattern using a photolithography process, as described in Patent Document 1.

As another method for forming a color filter pattern on a solid-state imaging element, Patent Document 2 describes a method in which all color filter patterns are formed by dry etching.

In recent years, there has been an increasing demand for high-definition CCD imaging devices with over 8 million pixels, and a growing demand for imaging devices with pixel sizes of less than 1.4 μm x 1.4 μm for the color filter patterns associated with these high-definition CCDs. However, by reducing the pixel size, the resolution of the color filter patterns formed by the photolithography process becomes insufficient, causing problems that adversely affect the characteristics of solid-state imaging devices. In solid-state imaging devices with sides of 1.4 μm or less, or around 1.1 μm or 0.9 μm, the lack of resolution manifests itself as color unevenness caused by defective pattern shapes.

As the pixel size of a color filter pattern becomes smaller, the aspect ratio of the color filter pattern (the height (thickness) relative to the width of the color filter pattern) becomes larger. When such a color filter pattern is formed by a photolithography process, the color filter in the area that should have been removed (the area outside the effective area of the pixel) is not completely removed, and remains as a residue that adversely affects pixels of other colors. When methods such as extending the development time are used to remove the residue, there is also the problem that even the necessary hardened pixels may peel off.

In addition, in order to obtain satisfactory spectral characteristics, the film thickness of the color filter must be increased. However, as the film thickness of the color filter increases, the resolution tends to decrease as the pixels become finer, for example, the corners of the color filter pattern become rounded. In order to increase the film thickness of the color filter pattern and obtain spectral characteristics, it is necessary to increase the pigment concentration contained in the color filter pattern material. However, if the pigment concentration contained in the color filter pattern material is increased, the light required for the photocuring reaction does not reach the bottom of the color filter pattern layer, and the color filter layer is not cured sufficiently. This causes a problem that the color filter layer peels off during the development process in photolithography, causing pixel defects.

Furthermore, if the pigment concentration in the color filter material is increased in order to reduce the film thickness of the color filter and obtain the desired spectral characteristics, the photocurable components will be relatively reduced. This results in insufficient photocuring of the color filter layer, which is likely to cause deterioration of the color filter shape, non-uniformity in the shape of the color filter within the surface, and deformation of the color filter. Furthermore, increasing the amount of exposure during curing in order to sufficiently photocuring the color filter layer creates the problem of reduced throughput.

Due to the high definition of the color filter pattern, the thickness of the color filter pattern not only affects the manufacturing process, but also the characteristics of the solid-state imaging element. When the color filter pattern is thick, the light incident from an oblique direction may be dispersed by a specific color filter and then enter other adjacent color filter pattern parts and photoelectric conversion elements. In this case, the problem of color mixing occurs. This color mixing problem becomes more prominent as the pixel size of the color filter pattern becomes smaller and the aspect ratio between the pixel size and the film thickness becomes larger. In addition, the problem of color mixing of incident light also occurs more prominently when the distance between the color filter pattern and the photoelectric conversion element becomes longer by forming a material such as a planarization layer on the substrate on which the photoelectric conversion element is formed. For this reason, it is important to reduce the thickness of the color filter pattern and the planarization layer formed below it.

To prevent color mixing caused by light incident from an oblique direction, a method is known in which a partition wall is formed between color filters of each color to reflect or refract light and block light from entering other pixels. For color filters used in optical display devices such as liquid crystal displays, partition walls with a black matrix (BM) structure made of black material are commonly known. However, in the case of solid-state imaging devices, the size of each color filter pattern is several μm or less. For this reason, if a partition wall is formed using a general black matrix formation method, the pattern size is large, so some pixels are filled with BM like pixel defects, resulting in reduced resolution.

In the case of a solid-state imaging device in which high definition is being developed, the size of the partition wall required is several hundred nm, more preferably a width of 200 nm or less, and pixel size is becoming high definition until one pixel size is about 1 μm. Therefore, if the light shielding performance capable of suppressing color mixing is satisfied, a width (dimension) of 100 nm or less is desirable. It is difficult to form partition walls of this size by photolithography using BM. For this reason, partition walls are formed by using metals such as aluminum, tungsten, titanium, inorganic substances such as SiO ₂ , or a combination of these, and forming a film by deposition, CVD, sputtering, etc., or by forming by cutting into a lattice pattern using etching technology. However, such a method has a problem that the manufacturing cost becomes very high due to the complexity of the manufacturing equipment and manufacturing process.

For these reasons, in order to increase the number of pixels in a solid-state imaging element, it is necessary to increase the resolution of the color filter layer pattern, and it is important to make the color filter layer thinner and to find a way to prevent color mixing.

As mentioned above, in the conventional pattern formation of color filter layers formed by photolithography after imparting photosensitivity to color filter materials, there is a demand for thinner color filter layers as pixel dimensions become finer. In this case, the content of pigment components in the color filter materials increases, making it impossible to contain sufficient amounts of photosensitive components, leading to problems such as insufficient resolution, residues being easily left behind, and pixels being easily peeled off, which reduces the characteristics of solid-state imaging devices.

Therefore, the technology of Patent Document 2 has been proposed to make the color filter pattern finer and thinner. Patent Document 2 describes forming a color filter pattern by dry etching, which allows patterning without containing a photosensitive component, so that the pigment concentration in the color filter material can be improved. These dry etching techniques make it possible to improve the pigment concentration, and to produce a color filter pattern that has sufficient spectral characteristics even when thinned.

Japanese Patent Application Laid-Open No. 11-68076 Japanese Patent No. 4905760

However, when the inventors studied the manufacturing method of the color filter pattern described in Patent Document 2, they found that the relationship between the film thicknesses of the color filters was not disclosed, and that it was not possible to achieve high sensitivity for all color filters. They also found that measures against color mixing were insufficient. They also found that when forming each color filter pattern by dry etching, since the color filter material is a material containing organic matter and metal, it is difficult to shape it by dry etching and residues are likely to remain, and further, they found that if dry etching is performed for a long time to avoid residues, plasma damage is likely to occur to the photoelectric conversion element.

The present invention has been made in consideration of the above-mentioned points, and aims to provide a solid-state imaging element that suppresses color mixing, reduces plasma damage, and has high resolution and good sensitivity.

A solid-state imaging element according to one embodiment of the present invention is characterized in that it comprises a semiconductor substrate having a plurality of photoelectric conversion elements arranged two-dimensionally, a color filter layer formed on the semiconductor substrate and having a plurality of color filters arranged two-dimensionally in a predetermined regular pattern corresponding to the plurality of photoelectric conversion elements, and a transparent conductive layer disposed between the semiconductor substrate and a color filter of a first color selected from the plurality of colors.

When the sheet resistance of the transparent conductive layer is F, the following formula (1) may be satisfied.
F < 100,000 Ω/□ ... (1)

The transparent conductive layer may be formed as a single layer or multiple layers of a compound containing at least one selected from silicon, carbon, oxygen, hydrogen, tin, zinc, indium, aluminum, gallium, titanium, molybdenum, tungsten, cadmium, niobium, tantalum, hafnium, silver, and fluorine.

The transparent conductive layer and the color filter of the first color may be made of materials that satisfy the following formula (2) when dry etching is performed using a gas containing at least one type selected from fluorine, oxygen, hydrogen, sulfur, carbon, bromine, chlorine, nitrogen, argon, helium, xenon, and krypton, where T is an etching rate of the transparent conductive layer and G is an etching rate of the color filter of the first color:
3≦G/T (2)

It may further include a partition disposed between the color filters of the above-mentioned multiple colors.

The partition wall may contain at least one element selected from zinc, copper, nickel, silicon, carbon, oxygen, hydrogen, nitrogen, bromine, chlorine, indium, and tin.

When the film thickness of the color filter of the first color is A [nm], the film thickness of the transparent conductive layer is B [nm], the film thickness of the color filter of a color other than the first color is C [nm], the visible light transmittance of the transparent conductive layer is D [%], and the dimension of the partition is E [nm], the following formulas (3) to (7) may be satisfied.
200 nm≦A≦700 nm (3)
0 [nm] < B ≦ 200 [nm] ... (4)
A+B-200 [nm]≦C≦A+B+200 [nm] ... (5)
D≧80% (6)
E≦200 [nm] (7)

A transparent resin layer may be further provided between the transparent conductive layer and the first color filter.

A transparent resin layer may further be provided between the transparent conductive layer and the semiconductor substrate.

The transparent resin layer may contain at least one element selected from silicon, carbon, oxygen, and hydrogen.

The color filter of the first color may contain a thermosetting resin.

The color filter of the first color may contain a thermosetting resin and a photocurable resin, and the content of the thermosetting resin may be greater than the content of the photocurable resin.

The color filter of the first color may contain a photocurable resin.

The color filter of the first color may have a concentration of pigment as a colorant of 50% by mass or more.

The color filter layer may have microlenses arranged two-dimensionally corresponding to each of the photoelectric conversion elements, and the height from the lens top to the lens bottom of the microlens may be in the range of 300 nm or more and 800 nm or less.

Among the multiple color filters, the color filter of the first color may have the largest occupied area.

A method for manufacturing a solid-state imaging device according to one aspect of the present invention includes a first step of forming a transparent conductive layer on a semiconductor substrate on which a plurality of photoelectric conversion elements are arranged two-dimensionally, applying a coating liquid for a color filter of a first color onto the transparent conductive layer and curing the coating liquid to form a transparent conductive layer and a color filter layer of the first color in this order, and then removing a portion of the color filter layer of the first color other than the position of the color filter of the first color by dry etching to form a pattern of the color filter of the first color; a second step of forming a by-product of the color filter layer and the dry etching gas generated when the color filter layer of the first color is dry-etched as a partition on the side wall of the color filter of the first color in the first step of patterning the color filter of the first color; and a third step of forming a color filter of a color other than the first color by patterning the color filter of the first color by photolithography after the second step.

A method for manufacturing a solid-state imaging device according to another aspect of the present invention includes a first step of forming a transparent conductive layer on a semiconductor substrate on which a plurality of photoelectric conversion elements are arranged two-dimensionally, forming a transparent resin layer on the transparent conductive layer, applying and curing a coating liquid for a color filter of a first color to form a transparent conductive layer, a transparent resin layer, and a color filter layer of a first color in this order, and then removing by dry etching the color filter layer portion of the first color other than the position of the color filter of the first color and the transparent resin layer located below the color filter layer portion of the first color to pattern the color filter of the first color; a second step of forming the color filter layer and the transparent resin layer and the by-product of the dry etching gas generated when dry etching the color filter layer of the first color and the transparent resin layer located below the color filter layer portion to be removed in the first step of patterning the color filter of the first color as a partition on the side wall of the color filter of the first color; and a third step of forming a color filter of a color other than the first color by patterning by photolithography after the second step.

The heating temperature during hardening of the first color filter may be 170°C or higher and 270°C or lower.

According to each aspect of the present invention, by making each color filter thin and by using partitions between the color filters, it is possible to suppress color mixing, and it is possible to provide a high-definition solid-state imaging element in which all color filters arranged in a pattern have high sensitivity without causing plasma damage due to dry etching.

1 is a partial cross-sectional view of a solid-state imaging element according to a first embodiment of the present invention. 1 is a partial plan view of a color filter array of a solid-state imaging device according to a first embodiment of the present invention. 3A to 3C are cross-sectional views showing the manufacturing process of the solid-state imaging device according to the first embodiment of the present invention, illustrating a transparent conductive layer forming process to a first color filter heat curing process. 3A to 3C are cross-sectional views illustrating the manufacturing process of the solid-state imaging device according to the first embodiment of the present invention, showing a process from a photosensitive resin material application process to a developing process of a color filter layer of a first color. 3A to 3C are cross-sectional views illustrating the manufacturing process of the solid-state imaging device according to the first embodiment of the present invention, showing a process from a process of dry etching a part of a color filter layer of a first color to a process of removing an etching mask. 4A to 4C are cross-sectional views showing the manufacturing process of the solid-state imaging device according to the first embodiment of the present invention, illustrating steps from a color filter application step of a second color to heat curing of the color filter of the second color. 4A to 4C are cross-sectional views illustrating the manufacturing process of the solid-state imaging device according to the first embodiment of the present invention, showing a process from a color filter application process of a third color to a color filter heat curing process of the third color. 3A to 3C are cross-sectional views illustrating the manufacturing process of the solid-state imaging element according to the first embodiment of the present invention, showing a planarizing layer forming step and a microlens forming step. 3A to 3C are cross-sectional views showing the manufacturing process of the solid-state imaging element according to the first embodiment of the present invention, illustrating a planarizing layer forming process to a microlens matrix layer forming process. 3A to 3C are cross-sectional views showing the manufacturing process of the solid-state imaging element according to the first embodiment of the present invention, illustrating a microlens master forming process through a lens transfer process. FIG. 4 is a partial cross-sectional view of a solid-state imaging element according to a second embodiment of the present invention. 10A to 10C are cross-sectional views illustrating the manufacturing process of a solid-state imaging device according to a second embodiment of the present invention, showing a transparent conductive layer forming process to a photosensitive resin material applying process. 11A to 11C are cross-sectional views showing the manufacturing process of a solid-state imaging device according to a second embodiment of the present invention, illustrating a process from a photosensitive resin material exposure process to a development process of a color filter layer of a first color. 11A to 11C are cross-sectional views illustrating the manufacturing process of a solid-state imaging device according to a second embodiment of the present invention, showing a process from a process of dry etching a part of a color filter layer of a first color to a process of removing an etching mask. FIG. 11 is a partial cross-sectional view of a solid-state imaging element according to a third embodiment of the present invention. 11A to 11C are cross-sectional views illustrating the manufacturing process of a solid-state imaging element according to a third embodiment of the present invention, showing a transparent resin layer forming process to a photosensitive resin material applying process. 11A to 11C are cross-sectional views showing the manufacturing process of a solid-state imaging device according to a third embodiment of the present invention, illustrating a process from a photosensitive resin material exposure process to a development process of a color filter layer of a first color. 11A to 11C are cross-sectional views illustrating the manufacturing process of a solid-state imaging device according to a third embodiment of the present invention, showing a process from a process of dry etching a part of a color filter layer of a first color to a process of removing an etching mask.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
Here, the drawings are schematic, and the relationship between the height (thickness) of the color filters and the planar dimensions, the height (thickness) ratio of each layer, etc. are different from the actual ones. Furthermore, each embodiment shown below is an example of a configuration for embodying the technical idea of the present invention, and the technical idea of the present invention is not limited to the materials, shapes, structures, etc. of the components described below. The technical idea of the present invention can be modified in various ways within the technical scope defined by the claims described in the claims.

First Embodiment
<Configuration of Solid-State Imaging Device>
1, the solid-state imaging element 1 according to this embodiment includes a semiconductor substrate 10 having a plurality of photoelectric conversion elements 11 arranged two-dimensionally, a microlens group 108 consisting of a plurality of microlenses 18 arranged above the semiconductor substrate 10, and a color filter layer 100 and partition walls 17 provided between the semiconductor substrate 10 and the microlenses 18. The color filter layer 100 is configured by arranging color filters 14, 15, and 16 of a plurality of colors in a predetermined regular pattern. The partition walls 17 are provided between each of the color filters 14, 15, and 16 of a plurality of colors.

Figure 1 shows a solid-state imaging element 1 having a transparent conductive layer 12 below a color filter layer 100. A planarization layer 13 is formed between the color filter layer 100 and a microlens group 180 consisting of a plurality of microlenses 18. The planarization layer 13 may not be necessary if it is integrated with the microlenses 18, such as in the etch-back method described below.

In the following description of the solid-state imaging device 1 according to this embodiment, the color filter with the largest area that is formed first in the manufacturing process is defined as the first color filter 14. The second color filter formed second in the manufacturing process is defined as the second color filter 15, and the third color filter formed third in the manufacturing process is defined as the third color filter 16. The same applies to other embodiments. That is, in this embodiment and other embodiments, of the first color filter 14, the second color filter 15, and the third color filter 16, which are examples of color filters of multiple colors, the first color filter 14 is configured to occupy the largest area.

In the solid-state imaging device 1 according to the present embodiment, the color filter 14 of the first color contains a thermosetting resin and a photosetting resin. The content of the photosetting resin is less than the content of the thermosetting resin. Here, the color filter 14 of the first color does not have to be the color filter with the largest area, nor the color filter formed first. In the present embodiment, the color filter layer 100 is illustrated as being composed of three colors, green, blue, and red, and arranged in a Bayer array arrangement pattern, but may be a color filter layer composed of four or more colors. In the following description, the first color is assumed to be green, but the first color may be blue or red.
Each part of the solid-state imaging device will be described in detail below.

(Photoelectric conversion element and semiconductor substrate)
A plurality of photoelectric conversion elements 11 corresponding to pixels are two-dimensionally arranged on the semiconductor substrate 10. The plurality of photoelectric conversion elements 11 have a function of converting light into an electric signal.
The semiconductor substrate 10 on which the photoelectric conversion element 11 is formed usually has a protective film formed on the outermost surface for the purpose of protecting and planarizing the surface (light incident surface). The semiconductor substrate 10 is formed of a material that transmits visible light and can withstand temperatures of at least about 300° C. Examples of such materials include materials containing Si, such as oxides such as Si and SiO ₂ , nitrides such as SiN, and mixtures thereof.

(Microlens)
Each microlens 18 is disposed above the semiconductor substrate 10 in correspondence with a pixel position. That is, a microlens 18 is provided for each of a plurality of photoelectric conversion elements 11 arranged two-dimensionally on a color filter layer 100 formed on the semiconductor substrate 10. The microlens 18 compensates for a decrease in sensitivity of the photoelectric conversion elements 11 by concentrating incident light incident on the microlens 18 onto each of the photoelectric conversion elements 11.
The height of the microlens 18 from the lens top to the lens bottom is preferably in the range of 300 nm to 800 nm.

(Transparent conductive layer)
The transparent conductive layer 12 is a layer provided for surface protection and flattening of the semiconductor substrate 10, and for reducing damage such as charging up caused by plasma etching. That is, the transparent conductive layer 12 reduces unevenness on the upper surface of the semiconductor substrate 10 caused by the fabrication of the photoelectric conversion elements 11, improves adhesion with the color filter material, and serves as a protective layer for plasma etching when patterning the color filters of the first color.

The transparent conductive layer 12 is formed of a single layer or multiple layers of compounds or oxides containing at least one selected from, for example, silicon, carbon, oxygen, hydrogen, tin, zinc, indium, aluminum, gallium, titanium, molybdenum, tungsten, cadmium, niobium, tantalum, hafnium, silver, and fluorine. As compounds of these materials, for example, transparent conductive layers such as ITO, ZnO, TiO ₂ , and HfO ₂ can be used. In addition, the transparent conductive layer 12 is not limited to these oxides and compounds, and can be formed using any material that transmits visible light with a wavelength of 400 nm to 700 nm and does not inhibit the pattern formation or adhesion of the color filters 14, 15, and 16. It is preferable that the transparent conductive layer 12 does not affect the spectral characteristics of the color filters 14, 15, and 16. For example, it is preferable that the transparent conductive layer 12 is formed so that the transmittance of visible light with a wavelength of 400 nm to 700 nm is 80% or more, and more preferably, the transmittance is 90% or more.

The sheet resistivity of the transparent conductive layer 12 is preferably less than 100,000 Ω/sq., i.e., a material that is so-called conductive. In particular, for commonly used transparent conductive layers, it is preferable that it is 5,000 Ω/sq. or less, more preferably 1,500 Ω/sq. or less, and even more preferably 800 Ω/sq. or less. The transparent conductive layer 12 that can obtain these sheet resistances is formed from the materials described above. For example, when ITO is used as the transparent conductive layer 12, it is possible to form a layer with a sheet resistance of 50 Ω/sq. or less. A similar sheet resistance can also be obtained with a transparent conductive film in which ZnO is doped with Al or Ga.

In addition, the transparent conductive layer 12 is preferably made of a compound with a slow etching rate in order to reduce plasma damage during dry etching. Therefore, it is desirable that the material composition is such that the etching rate of the transparent conductive layer 12 is slower than the etching rate of the color filter 14. In dry etching using a gas containing at least one type selected from fluorine, oxygen, sulfur, carbon, bromine, chlorine, argon, helium, xenon, and krypton as a gas used in dry etching, it is preferable that the etching rate (G) of the transparent conductive layer 12 is 3 times slower (3≦G/T) than the etching rate (T) of the color filter 14, and more preferably 10 times slower. Specifically, when an ITO film is used for the transparent conductive layer 12 and dry etching is performed using a gas containing fluorine, carbon, and oxygen as the dry etching gas, the etching of the ITO film hardly progresses, and the etching rate is 20 times slower than the color filter 14, satisfying the etching rate setting.

In addition, as long as the required transmittance can be met, the transparent conductive layer 12 may be made of transparent resins such as nano-ink using Ag, particle agglomerates such as nano-ITO using inorganic oxides, carbon nanotube ink, and conductive polymers.

In this embodiment, the film thickness B [nm] of the transparent conductive layer 12 is formed to be greater than 0 [nm] and less than or equal to 200 [nm]. From the viewpoints of transmittance and prevention of color mixing, the thinner the film thickness B of the transparent conductive layer 12, the more preferable, and the more preferable is 5 nm or more and 80 nm or less.

(Planarization Layer)
The planarization layer 13 is a layer provided to planarize the upper surfaces of the first to third color filters 14, 15, and 16 (hereinafter sometimes referred to as "each color filter 14, 15, and 16") and the partition wall 17. The planarization layer 13 is formed of a resin containing one or more resins such as acrylic resin, epoxy resin, polyimide resin, phenol novolac resin, polyester resin, urethane resin, melamine resin, urea resin, styrene resin, and silicon resin. The planarization layer 13 may be integrated with the microlens 18. The thickness of the planarization layer 13 is, for example, 1 nm or more and 300 nm or less. From the viewpoint of preventing color mixing, the thinner the layer, the better.

(Color filters)
The color filters 14, 15, and 16 constituting the color filter layer 100 in a predetermined pattern correspond to the colors that separate the incident light. The color filters 14, 15, and 16 are provided between the semiconductor substrate 10 and the microlens 18, and are arranged in a regular pattern that is set in advance so as to correspond to each of the photoelectric conversion elements 11 according to the pixel positions.

2 shows in plan view the arrangement of the color filters 14, 15, 16 and the partitions 17 formed between the color filters 14, 15, 16. The arrangement shown in FIG. 2 is a so-called Bayer arrangement, in which a pattern of the color filters 14, 15, 16 (color filters of the first, second, and third colors) each having a rectangular shape with rounded corners is laid out.

Each of the color filters 14, 15, and 16 contains a pigment (colorant) of a predetermined color, as well as a heat-curable component and a light-curable component. For example, the first color filter 14 contains a green pigment as a colorant, the second color filter 15 contains a blue pigment, and the third color filter 16 contains a red pigment.

In this embodiment, the color filter 14 of the first color contains a thermosetting resin and a photocurable resin, but it is preferable that the amount of the thermosetting resin is larger. In this case, for example, the amount of the curable component in the solid content is 5% by mass to 40% by mass, the amount of the thermosetting resin is 5% by mass to 20% by mass, and the amount of the photocurable resin is 1% by mass to 20% by mass, preferably the amount of the thermosetting resin is 5% by mass to 15% by mass, and the amount of the photocurable resin is 1% by mass to 10% by mass.
When the curing component is a thermosetting component alone, the content of the curing component in the solid content is preferably in the range of 5% by mass to 40% by mass, more preferably 5% by mass to 15% by mass.
On the other hand, when the curable component is only a photocurable component, the content of the curable component in the solid content is in the range of 10% by mass to 40% by mass, more preferably 10% by mass to 20% by mass.

(Partition wall)
The partition walls 17 are formed between each of the color filters 14, 15, and 16 of the multiple colors. In this embodiment, the partition walls 17 provided on the side wall portion of the color filter 14 of the first color can separate the color filter 14 of the first color from the color filters 15 and 16 of the second and third colors. The partition walls 17 contain a reaction product of the color filter material of the first color contained in the color filter 14 of the first color and the material contained in the transparent conductive layer 12, and the dry etching gas used in forming the color filter 14 of the first color.

The material of the partition 17 contains the material contained in the color filter 14 of the first color and the material of the transparent conductive layer 12. The material of the partition 17 contains a compound containing at least one of zinc, copper, nickel, silicon, carbon, oxygen, hydrogen, nitrogen, bromine, and chlorine, and the material used for the transparent conductive layer 12 is formed from a compound containing at least one of silicon, carbon, oxygen, hydrogen, tin, zinc, indium, aluminum, gallium, titanium, molybdenum, tungsten, cadmium, niobium, tantalum, hafnium, silver, and fluorine. When ITO is used for the transparent conductive layer 12, a material containing indium, tin, oxygen, etc. may be contained in the partition 17 in a small amount. When ITO or the like is used for the transparent conductive layer 12, the etching amount is small depending on the etching conditions, so the material of the partition 17 is mostly made up of the color filter material of the first color.

In this embodiment, a solid-state imaging device 1 having color filters 14, 15, and 16 in a Bayer array as shown in Figure 2 will be described. However, the color filters of the solid-state imaging device 1 are not necessarily limited to the Bayer array, and the colors of the color filters are not limited to the three colors of red (R), green (G), and blue (B). In addition, a transparent layer with an adjusted refractive index may be disposed in part of the color filter array.

The film thickness A [nm] of the first color filter 14 is formed to be 200 [nm] or more and 700 [nm] or less. Preferably, the film thickness A [nm] is 400 [nm] or more and 600 [nm] or less. More preferably, the film thickness A [nm] is 500 [nm] or less.

The thickness B [nm] of the transparent conductive layer 12 is greater than 0 [nm] and less than 200 [nm]. Preferably, the thickness B [nm] is greater than 5 [nm] and less than 80 [nm]. More preferably, the thickness B [nm] is less than 50 [nm].

Furthermore, when the thickness of the color filters 15 and 16 of the colors other than the first color is C [nm], the color filters 15 and 16 are formed to have a thickness that satisfies the following formula.
A+B-200 [nm]≦C≦A+B+200 [nm]
However, the thickness of the color filter 15 of the second color and the thickness of the color filter 16 of the third color may be different. Here, the difference in thickness between the (A+B) film thickness and the C film thickness is set to 200 [nm] or less because if there is a part where the difference in thickness exceeds 200 [nm], the light receiving sensitivity may decrease due to the influence of obliquely incident light on other pixels. Also, if a step exceeding 200 [nm] is formed in the color filter layer 100, it may be difficult to form the upper microlens 18.

In addition, in order to make the color filter layer 100 thinner, it is preferable that the concentration of the pigment (colorant) contained in the first to third color filters 14, 15, and 16 is 50 mass% or more.

In addition, partitions 17 are formed between each of the color filters 14, 15, and 16 of multiple colors. The partitions are formed to have a width (dimension) of 200 nm or less. Here, the height of the partitions is set to 200 nm or less because if the width (dimension) of the partitions is greater than 200 nm, the partitions may significantly reduce the light incident on the photoelectric conversion element 11, resulting in a reduction in light receiving sensitivity.

<Method of Manufacturing Solid-State Imaging Device>
Next, a method for manufacturing the solid-state imaging device of the first embodiment will be described with reference to FIGS.

(Transparent conductive layer forming process)
3A, a semiconductor substrate 10 having a plurality of photoelectric conversion elements 11 is prepared, and a transparent conductive layer 12 is formed on the entire surface of the substrate where a color filter layer is to be formed. The transparent conductive layer 12 is formed from a compound containing one or more of the above-mentioned materials such as silicon, carbon, oxygen, hydrogen, tin, zinc, indium, aluminum, gallium, titanium, molybdenum, tungsten, cadmium, niobium, tantalum, hafnium, silver, fluorine, an oxide compound, a nitride compound, or the like.

The transparent conductive layer 12 is formed by a film of the above-mentioned compound using chemical methods such as spraying, coating, and CVD, and physical methods such as vacuum deposition, ion plating, and sputtering. Chemical methods involve hydrolysis of chlorides or thermal decomposition of organic compounds. The transparent conductive layer 12 may also be formed by coating a substance containing these materials, or by heat curing.

In this case, if the transparent conductive layer 12 is formed on the entire surface of the semiconductor substrate 10, it also covers the electrode portion of the semiconductor substrate 10, so it is necessary to remove the transparent conductive layer 12 from the electrode portion. As a method for partially removing the transparent conductive layer 12, a known method can be used, such as opening only the portion to be removed with a mask material and using a removal method such as dry etching or wet etching, or filling the portion with a removable material in advance, such as a lift-off method. When ITO is used for the transparent conductive layer 12, amorphous ITO can be formed by non-heating, a mask structure can be formed using photoresist, wet etching can be performed with oxalic acid, etc., opening the electrode portion, and then heating the semiconductor substrate to crystallize the ITO.

Here, the manufacturing method of the solid-state imaging device according to this embodiment is different from the conventional method of directly patterning the color filters 14, 15, and 16 that constitute the color filter layer 100 by photolithography using a photosensitive color filter material. That is, in the manufacturing method of the solid-state imaging device 1 according to this embodiment, after the color filter material of the first color is applied to the entire surface and cured to form the color filter layer 14a of the first color (see FIG. 3(d)), the portion of the color filter layer 14a of the first color where other color filters are to be formed is removed by dry etching. As a result, the pattern of the color filter 14 of the first color (see FIG. 4(c)) is formed. In addition, the reaction product of the color filter layer 14a of the first color and the transparent conductive layer 12 with the dry etching gas, which is generated when the color filter layer 14a of the first color and a part of the transparent conductive layer 12 of the first color are dry-etched, and are formed as the partition wall 17 on the side wall (i.e., the outer periphery) of the color filter 14 of the first color. Then, the second and subsequent color filters (patterns 15, 16 of the color filters of the second and third colors) are patterned in the portion surrounded by the first color filter 14 and the partition wall 17. At this time, the previously formed patterns of the first color filter 14 and the partition wall 17 are used as guide patterns to harden the second and subsequent color filter materials by a high-temperature heat treatment. This makes it possible to improve the adhesion between the semiconductor substrate 10 and the color filters 15, 16.
The formation process will be described below.

(First Color Filter Layer Forming Step (First Step))
3 to 5, a process for forming a color filter 14 of a first color on the surface of a transparent conductive layer 12 formed on a semiconductor substrate 10 will be described. The color filter 14 of the first color is preferably a color filter of a color having the largest occupation area in the solid-state imaging device.

In the first color filter layer formation process, a transparent conductive layer 12 is formed on a semiconductor substrate 10 on which a plurality of photoelectric conversion elements 11 are arranged two-dimensionally, a coating liquid for the first color filter 14 is applied onto the transparent conductive layer 12 and cured to form the transparent conductive layer 12 and the first color filter layer 14a in this order, and then the first color filter layer 14a except for the position where the first color filter 14 is arranged is removed by dry etching to form a pattern of the first color filter 14. The first color filter layer formation process is described in detail below.

A transparent conductive layer 12 is formed on a semiconductor substrate 10 on which a plurality of photoelectric conversion elements 11 are arranged two-dimensionally. Next, on the transparent conductive layer 12 formed on the semiconductor substrate 10, i.e., on the surface of the transparent conductive layer 12 (see FIG. 3(a)), as shown in FIG. 3(b), a color filter material of the first color, which is made of a first resin dispersion liquid in which a resin material is the main component and a first pigment (colorant) is dispersed, is applied to form a color filter layer 14a of the first color. The solid-state imaging element 1 according to this embodiment is assumed to use a Bayer array color filter as shown in FIG. 2. For this reason, it is preferable that the first color is green (G). The color filter layer 14a of the first color has a thickness equal to or slightly thicker than the color filter 14 of the first color that is finally formed, but for convenience of explanation, in FIG. 3 and FIG. 4 described later, the color filter layer 14a of the first color is illustrated in a state in which the thickness is thinner than the color filter 14 of the first color (see FIG. 5).

As the resin material for the color filter material of the first color, a mixed resin containing a thermosetting resin such as an epoxy resin and a photocurable resin such as an ultraviolet curable resin is used. However, the amount of photocurable resin is less than the amount of thermosetting resin. By using a large amount of thermosetting resin as the resin material, it is possible to increase the pigment content of the color filter layer 14a of the first color, unlike the case where a large amount of photocurable resin is used as the curable resin, and it becomes easier to form a first color filter 14 that is a thin film and has the desired spectral characteristics. However, in this embodiment, a mixed resin containing both a thermosetting resin and a photocurable resin is described, but it is not necessarily limited to a mixed resin, and it may be a resin containing only one of the curable resins.

Next, as shown in FIG. 3(c), the entire surface of the first color filter layer 14a is irradiated with ultraviolet light to photo-cure the first color filter layer 14a. In this embodiment, unlike the conventional method of directly forming a desired pattern by making the color filter material photosensitive and exposing it to light, the entire surface of the first color filter layer 14a is cured, so that curing is possible even if the content of the photosensitive component is reduced. If the photocurable resin is not mixed into the first color filter material, this exposure step does not need to be performed. If the solvent resistance, which will be described later, is satisfactory without the inclusion of the photocurable resin, the photocurable resin can be removed to further improve the pigment concentration and make the film thinner.

Next, as shown in FIG. 3(d), the first color filter layer 14a is thermally cured at 150°C or more and 300°C or less. More specifically, the heating temperature during curing of the first color filter layer 14a is preferably 170°C or more and 270°C or less. In the manufacture of solid-state imaging devices, a high-temperature heating process of 100°C or more and 300°C or less is often used when forming the microlenses 18, so it is desirable for the material for the first color filter to be resistant to high temperatures. For this reason, it is more preferable to use a thermosetting resin that is resistant to high temperatures as the resin material.

Next, as shown in FIGS. 4(a) to 4(c), an etching mask pattern having openings is formed on the color filter layer 14a of the first color formed in the previous step.
First, as shown in FIG. 4A, a photosensitive resin material is applied to the surface of the color filter layer 14a of the first color and then dried to form an etching mask 20.
Next, as shown in FIG. 4(b), a photomask (not shown) is used to expose the photosensitive resin layer to areas of the first color filter layer 14a corresponding to positions where the first color filter 14 is not to be formed, causing a chemical reaction in which areas other than the required pattern become soluble in a developer.

Next, as shown in FIG. 4(c), unnecessary portions (exposed portions) of the etching mask 20 are removed by development. This forms an etching mask pattern 20a having openings 20b. In the positions of the openings 20b, a color filter of the second color or a color filter of the third color will be formed in a later process.

As the photosensitive resin material, for example, acrylic resin, epoxy resin, polyimide resin, phenol novolac resin, and other photosensitive resins can be used alone or in a mixture or copolymer. Examples of exposure machines used in the photolithography process for patterning the photosensitive resin layer include scanners, steppers, aligners, and mirror projection aligners. Exposure may also be performed by direct drawing with an electron beam, drawing with a laser, or the like. In particular, steppers and scanners are generally used to form the first color filter 14 of a solid-state imaging element that requires fine processing.

As a photosensitive resin material, it is desirable to use a general photoresist in order to create high-resolution, high-precision patterns. By using photoresist, it is possible to form patterns with easy shape control and good dimensional accuracy, unlike when patterns are formed using photosensitive color filter materials.

The photoresist used in this case is preferably one with high dry etching resistance. When used as an etching mask material during dry etching, a thermal curing process called post-baking is often used after development to improve the selectivity, which is the etching rate with the etching material. However, if a thermal curing process is included, it may be difficult to remove the remaining resist used as the etching mask in the removal process after dry etching. For this reason, it is preferable for the photoresist to be one that can obtain a selectivity with the etching material without using a thermal curing process. Also, if a good selectivity is not obtained, it is necessary to form the photoresist material to a thick film thickness, but if the film is made thick, it becomes difficult to form fine patterns. For this reason, it is preferable for the photoresist to be a material with high dry etching resistance.

Specifically, the etching speed ratio (selectivity) of the photosensitive resin material that is the etching mask and the material for the first color filter that is the target of dry etching is preferably 0.5 or more, more preferably 0.8 or more. With this selectivity, it is possible to etch the color filter 14 without completely erasing the etching mask pattern 20a. When the film thickness of the material for the first color filter is about 0.2 μm or more and 0.7 μm or less, it is desirable that the film thickness of the photosensitive resin layer is about 0.5 μm or more and 2.0 μm or less.

In addition, the photoresist used in this case may be either a positive resist or a negative resist. However, when considering the removal of the photoresist after etching, a positive resist, which is more likely to undergo a chemical reaction in the direction of dissolution due to an external factor, is more preferable than a negative resist, which is more likely to undergo a chemical reaction in the direction of hardening due to an external factor.
In this manner, an etching mask pattern is formed.

As shown in FIG. 5A, a portion of the color filter layer 14a of the first color exposed from the opening 20b is removed by dry etching using an etching mask pattern and a dry etching gas.
Examples of dry etching techniques include ECR, parallel plate magnetron, DRM, ICP, or dual frequency RIE (Reactive Ion Etching). There are no particular limitations on the etching method, but it is preferable to use a method that can control the etching rate and etching shape so that they do not change even if the line width and area of a large area pattern with a width of several mm or more or a micro pattern with a width of several hundred nm are different. It is also preferable to use a dry etching technique with a control mechanism that can perform uniform dry etching over the entire surface of a wafer with a size of about 100 mm to 450 mm.

The dry etching gas may be any gas that has reactivity (oxidizing and reducing properties), that is, has etching properties. Examples of reactive gases include gases containing fluorine, oxygen, bromine, sulfur, and chlorine. In addition, rare gases containing elements such as argon and helium that have low reactivity and perform etching by physical impact with ions can be used alone or in combination. Therefore, the gas used for dry etching is a gas containing at least one selected from fluorine, oxygen, hydrogen, sulfur, carbon, bromine, chlorine, nitrogen, argon, helium, xenon, and krypton. Examples of fluorine-containing gases include CF ₄ , C ₂ F ₆ , C 3 F 8 , C ₃ F ₆ , C ₄ F ₈ , C ₄ F ₁₀ , CHF ₃ , CClF ₃ , CCl _{3 F} , NF _{3 ,} SF ₆ , and HF, and a dry etching gas containing a mixture of these fluorine-based gases may be used.

In addition, the gas is not limited to these, and can be used as long as it causes a reaction that forms the desired pattern in a dry etching process in a plasma environment using gas. In this embodiment, at the initial stage, 90% or more of the total gas flow rate is made up of gas that mainly uses the physical impact of ions from rare gases, etc., and an etching gas mixed with a fluorine-based gas or oxygen-based gas is used, thereby improving the etching rate by also utilizing chemical reactions.

By using a large amount of rare gas in the dry etching gas, the physical impact of the rare gas ions creates conditions that make it easier for anisotropic etching, in which etching proceeds vertically, to proceed. Therefore, in the initial stage of etching the color filters, etching is carried out under conditions with a large amount of rare gas.

The semiconductor substrate 10 of the solid-state imaging element is made of a material mainly composed of silicon. Therefore, if dry etching is performed using a highly reactive gas such as a gas containing fluorine, the semiconductor substrate 10 may be etched. Therefore, when performing dry etching, it is preferable to use a gas that does not etch the semiconductor substrate 10. In addition, when using a gas that etches the semiconductor substrate 10, multi-stage etching may be performed by first using a gas that etches the semiconductor substrate 10 and then changing to a gas that does not easily etch the semiconductor substrate 10 midway. In addition, the type of etching gas is not limited as long as it does not affect the semiconductor substrate 10, the etching mask pattern 20a can be used to etch the material for the first color filter in a nearly vertical shape, and no residue of the material for the first color filter is formed.

However, in this embodiment, when a compound containing one or more of materials such as silicon, carbon, oxygen, hydrogen, tin, zinc, indium, aluminum, gallium, titanium, molybdenum, tungsten, cadmium, niobium, tantalum, hafnium, silver, fluorine, etc., or an oxide compound, nitride compound, etc. is used for the transparent conductive layer 12, it is resistant to dry etching against gases containing fluorine, and the etching rate of the transparent conductive layer 12 is slow, so that it is possible to remove the color filter at the desired position, stop the etching at the transparent conductive layer 12, and not etch the underlying semiconductor substrate 10.

Specifically, 90% or more of the total gas flow rate of the rare gas alone or the mixture of reactive gas and rare gas is rare gas, and the color filter layer 14a of the first color and the part of the transparent conductive layer 12 exposed in the opening 20b are etched. At this time, in order to reduce damage to the semiconductor substrate 10, the etching may be stopped midway and the proportion of rare gas that physically performs the etching may be reduced.

In the next step, oxygen and fluorine-based gases, which have a low etching rate for the transparent conductive layer 12, are used to etch away all of the first color filter layer 14a exposed in the opening 20b. The conditions used in this step are such that the etching rate for the transparent conductive layer 12 is slow, so the etching is performed for a time that leaves no residue on the color filter and does not remove the transparent conductive layer 12. Figure 5 shows a configuration in which the transparent conductive layer 12 is resistant to the dry etching gas and has barely progressed in etching.

In this case, as long as the transparent conductive layer 12 is not completely removed, a rare gas may be mixed into the dry etching gas to perform etching with increased anisotropy. Under these conditions, the physical impact of the rare gas makes it easier for the material of the transparent conductive layer to be contained in the partition 17. In this manner, a color filter 14 of the first color is formed, as shown in Figure 5(a).

(Partition Wall Forming Process (Second Process))
In addition, in the process of patterning the color filter 14 of the first color, as shown in FIG. 5A, a reaction product (one example of a by-product) generated when the color filter layer 14a of the first color and the transparent conductive layer 12 of the first color are dry-etched to form a partition wall 17 that is finally provided between each of the color filters 14, 15, and 16 on the side wall of the color filter 14 of the first color. The partition wall 17 is formed by a reaction product of the material for the color filter of the first color and the material for the transparent conductive layer with the dry etching gas. At this time, when performing anisotropic etching, it is important to control the side wall protection layer formed by the reaction product of the dry etching adhering to the side wall of the color filter 14 of the first color. In addition, the manner and amount of the reaction product adhering to the side wall of the color filter 14 of the first color changes depending on the dry etching conditions.

In the method for manufacturing a solid-state imaging device of this embodiment, the color filter layer 14a of the first color is etched, and the openings formed by the etching are filled with color filter materials of the second and third colors to form a multi-color filter. For this reason, during dry etching, it is necessary to etch the color filter layer 14a of the first color vertically and control the pattern size. For this reason, it is necessary to control the manner and amount of adhesion of the reaction product to the sidewall during dry etching.

In dry etching, the reaction using the physical impact of ions makes it possible to increase the amount of deposition (adhesion) of reaction products on the sidewall. For example, the dry etching gas used may be rare gases such as helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe), with Ar and He being particularly preferable.

In this embodiment, a dry etching gas is used in which a rare gas containing a less reactive element such as Ar or He is 90% or more of the total gas flow rate, and one or more reactive gas species such as a fluorine-based or oxygen-based gas are mixed. This makes it possible to improve the etching rate using a chemical reaction and control the amount of reaction products that adhere to the sidewall of the first color filter 14. As a result, the reaction products that adhere to the sidewall of the first color filter 14 are formed as the partition 17.

There are three well-known types of plasma damage that occur during the dry etching process: electrical damage caused by charge-up due to the plasma, physical damage caused by collisions of rare gas particles such as Ar ions, and light irradiation damage caused by high-energy photon irradiation from the plasma. According to this embodiment, the transparent conductive layer 12, which is conductive and has a slow etching rate, is provided on the surface of the semiconductor substrate 10, thereby preventing these types of damage from reaching the semiconductor substrate 10.

The dry etching process produces a color filter 14 of the first color having partition walls 17 formed by the reaction product produced by dry etching without generating any residue of the color filter material. The partition walls 17 suppress light leakage and migration from other colors, thereby suppressing color mixing.

(Etching mask pattern removal process)
Next, the remaining etching mask pattern 20a is removed (see FIG. 5B). The etching mask pattern 20a can be removed by, for example, using a chemical solution or a solvent to dissolve and peel off the etching mask pattern 20a without affecting the color filter 14 of the first color. As a solvent for removing the etching mask pattern 20a, for example, N-methyl-2-pyrrolidone, cyclohexanone, diethylene glycol monomethyl ether acetate, methyl lactate, butyl lactate, dimethyl sulfoxide, diethylene glycol diethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monomethyl ether acetate, or a mixed solvent in which a plurality of organic solvents are mixed is used. In addition, it is preferable that the solvent used in this case does not affect the material for the color filters. If the material for the color filters is not affected, a peeling method using an acid-based chemical may be used.

In addition, a removal method other than a wet process such as a solvent can also be used. The etching mask pattern 20a can be removed by a method using an ashing technique, which is an ashing technique for resist using photoexcitation or oxygen plasma. These methods can also be used in combination. For example, a method can be used in which a layer altered by dry etching of the surface layer of the etching mask pattern 20a is first removed using an ashing technique, which is an ashing technique using photoexcitation or oxygen plasma, and then the remaining layer is removed by wet etching using a solvent or the like. In addition, the etching mask pattern 20a may be removed only by ashing as long as the material for the first color filter is not damaged. In addition to a dry process such as ashing, a polishing process using CMP or the like may also be used.
Through the above steps, the patterning of the first color filter 14 and the partition walls 17 is completed.

(Regarding the process of forming the second and subsequent color filter patterns (third process))
Next, after the partition wall forming process, as shown in FIG. 6, color filters 15 and 16 of second and third colors including a color different from the color filter 14 of the first color are formed.
This method uses the pattern of the first color filter 14 and the partition 17 as a guide pattern, and forms the second and third color filters 15 and 16 using a photosensitive color filter material containing a photocurable resin, and then selectively exposes them using conventional methods to form a pattern.

First, as shown in Figure 6(a), a photosensitive color filter material is applied as a second color filter material to the entire surface of the semiconductor substrate 10 on which the first color filter 14 and the partition wall 17 are patterned, and then dried to form the second color filter layer 15a. The photosensitive color filter material used in this case contains a negative type photosensitive component that hardens when exposed to light.

In this case, assuming that the film thickness of the first color filter 14 is A [nm], the film thickness of the transparent conductive layer 12 is B [nm], and the film thickness of the second color filter 15 is C1 [nm], the film thickness C1 of the second color filter 15 is set so as to satisfy the following equations (1) to (3a).
200 nm≦A≦700 nm (1)
0 [nm] < B ≦ 200 [nm] ... (2)
A+B-200 [nm]≦C1≦A+B+200 ... (3a)
FIG. 6 illustrates the case where A=C1, but as shown in formula (3a), the film thickness C1 may be within the range of (A+B)±200 nm.
As the color filter 15 of the second color, if the thickness is within this range of film thickness C1, it is possible to provide a color filter that contains sufficient thermosetting resin and photocurable resin for curing, and has a pigment concentration that provides the desired spectral characteristics.

Next, as shown in FIG. 6(b), the portion where the second color filter 15 is to be formed is exposed using a photomask, the pattern region of the second color filter layer 15a is selectively photocured, and the outside of the pattern region of the second color filter layer 15a that is not selectively exposed in the development process (the position where the third color filter is formed) is removed. Next, as shown in FIG. 6(c), in order to improve the adhesion between the pattern region of the second color filter layer 15a that has been exposed and developed and the semiconductor substrate 10 and to improve the heat resistance in actual device use, the second color filter layer 15a is cured by performing a curing process at high temperature heating. This forms the pattern of the second color filter 15. At this time, the temperature used for curing is preferably 200° C. or higher.

Next, as shown in FIG. 7(a), a material for a color filter of a third color is applied to the entire surface of the semiconductor substrate 10 and dried. That is, the material for a color filter of a third color is applied to the entire surface outside the pattern region of the color filter layer 15a of the second color to form a color filter layer 16a of a third color. Next, as shown in FIG. 7(b), the pattern region of the color filter layer 16a of the third color in which the color filter 16 of the third color is formed is selectively exposed to light, the color filter layer 16a of the third color is photocured, and the outside of the pattern region of the color filter layer 16a of the third color that is not exposed by development is removed. Next, as shown in FIG. 7(c), in order to improve the adhesion between the part of the color filter layer 16a of the third color that has been exposed and developed and the semiconductor substrate 10 and to improve the heat resistance in actual device use, the color filter layer 16a of the third color is cured by performing a curing process at high temperature. This forms the color filter 16 of the third color.
It is possible to form color filters of a desired number of colors by repeating the pattern formation process for the second color filter 15 and subsequent color filters.

In this case, when the thickness of the color filter 16 of the third color is C2 [nm], the thickness C2 of the color filter 16 of the third color is set so as to satisfy the following formulas (1) to (3b).
200 nm≦A≦700 nm (1)
0 [nm] < B ≦ 200 [nm] ... (2)
A+B-200 [nm]≦C2≦A+B+200 ... (3b)
FIG. 7 illustrates the case where A=C2, but as shown in formula (3b), the film thickness C2 may be within the range of (A+B)±200 nm.
As the color filter 16 of the third color, if the thickness is within this range of film thickness C2, it is possible to provide a color filter that contains sufficient thermosetting resin and photocurable resin for curing, while having a pigment concentration that provides the desired spectral characteristics.

8(a), a planarization layer 13 is formed on the formed color filters 14, 15, 16 and partition walls 17. The planarization layer 13 can be formed using a resin containing one or more resin materials, such as an acrylic resin. The planarization layer 13 can be formed by applying a resin material onto each of the color filters 14, 15, 16 of multiple colors and the partition walls 17 and curing it by heating. The planarization layer 13 can also be formed using a compound such as an oxide or nitride. In this case, the planarization layer 13 can be formed by various film formation methods such as deposition, sputtering, and CVD.

8B, a microlens 18 is formed on the planarization layer 13. The microlens 18 is formed by a known technique such as a manufacturing method using a thermal flow, a macrolens manufacturing method using a gray-tone mask, or a microlens transfer method to the planarization layer 13 using dry etching.
The thickness of the planarization layer 13 is, for example, 1 nm or more and 300 nm or less, preferably 100 nm or less, and more preferably 60 nm or less.

The method of forming a microlens using dry etching patterning technology involves first forming a planarization layer 13, which will eventually become the microlens, on each of the multiple color filters 14, 15, and 16 and the partition wall, as shown in Figure 9 (a).

9(b), a microlens matrix layer 18a for forming a matrix for a microlens is applied onto the planarization layer 13. The material for the microlens matrix layer 18a is a resin containing one or more resin materials such as an acrylic resin.

Next, as shown in FIG. 10A, a photomask (not shown) is used for exposure, and a lens mother die 18b of a microlens is formed by a thermal flow method.
10B, the shape of the lens master die 18b is transferred to the planarization layer 13 by dry etching using the lens master die 18b as a mask. By selecting the height and material of the lens master die 18b and adjusting the dry etching conditions, it is possible to transfer microlenses 18 having an appropriate lens shape to the planarization layer 13. As a result, a plurality of microlenses 18 integrated with the planarization layer 13 are formed.
By using the above method, it is possible to form the microlens 18 with good controllability. It is preferable to use this method to fabricate the microlens 18 so that the height from the lens top to the lens bottom of the microlens 18 is a film thickness of 300 to 800 nm.

(For filters with four or more colors)
When manufacturing color filters of four or more colors, the positions for forming the color filters of four or more colors are opened when the color filter of the first color is formed, and the steps for the third color filter and after are repeated in the same manner as the step for forming the second color filter 15. Furthermore, the step for forming the color filter of the last color is performed in the same manner as the step for forming the third color filter 16. In this way, color filters of four or more colors can be manufactured.

Through the above steps, the solid-state imaging element 1 of this embodiment is completed.

In this embodiment, it is preferable that the first color filter 14 is the color filter with the largest occupied area. The second color filter 15 and the third color filter 16 are each formed by photolithography using a photosensitive color resist.

The technology using photosensitive color resist is a conventional manufacturing technology for color filter patterns. The material for the first color filter is applied to the entire surface of the transparent conductive layer 12 and then heated at high temperature, so that it can improve adhesion to the semiconductor substrate 10 and the transparent conductive layer 12. Therefore, the pattern of the first color filter 14 and the partition wall 17, which have good adhesion and are formed with good rectangularity, can be used as a guide pattern to form the second and third color filters 15 and 16 so as to fill the area surrounded by the partition wall 17. Therefore, even if a color resist with photosensitivity is used for the second and subsequent color filters, it is not necessary to use a color resist that emphasizes resolution as in the past. Therefore, the photocurable component in the photocurable resin can be reduced, so that the ratio of pigment in the material for the color filter can be increased, and the color filters 15 and 16 can be made thinner.

In this embodiment, both thermosetting resin and photocurable resin are used for the color filter 14 of the first color. It is desirable to form the color filter 14 of the first color from a color filter material that has a low content of resin components involved in photocuring and a high pigment content. In particular, it is desirable to configure the pigment content in the color filter material of the first color to be 70 mass% or more. As a result, even if the color filter material of the first color contains a pigment at a concentration that would result in insufficient curing in a photolithography process using a conventional photosensitive color resist, the color filter 14 of the first color can be formed with high precision and without residue or peeling.

In this embodiment, a material that combines thermosetting resin and photocurable resin is used for the first color filter 14 to improve its hardening and solvent resistance, but depending on the desired spectral characteristics, it is also possible to form the material using only thermosetting resin or only photocurable resin, with an emphasis on pigment concentration and aging characteristics. When only thermosetting resin is used, it is possible to increase the pigment concentration, making it possible to make the color filter thinner. On the other hand, when only photocurable resin is used, solvent resistance is likely to decrease, but there is the advantage that the freedom of material design is increased in terms of aging characteristics, etc.

In this embodiment, a partition 17 is provided between the first color filter 14 and the second and third color filters 15, 16, and the partition 17 suppresses light leakage and migration from other colors, thereby suppressing color mixing.

In this embodiment, the presence of the transparent conductive layer 12 beneath the first color filter 14 reduces plasma damage during the dry etching process to open the areas where the second and third color filters 15 and 16 are to be formed, and the transparent conductive layer, which has a slow etching rate, acts as an etching stopper, reducing the possibility of dry etching the semiconductor substrate 10.

As described above, according to this embodiment, the film thickness of each color filter is reduced, shortening the total distance from the top of the microlens to the device, and by providing partitions between multiple color filters, color mixing can be suppressed, making it possible to provide a high-definition solid-state imaging element in which all color filters arranged in a pattern have high sensitivity.

Second Embodiment
Hereinafter, a solid-state imaging element and a manufacturing method thereof according to the second embodiment of the present invention will be described with reference to Fig. 11 to Fig. 14. As shown in Fig. 11, the solid-state imaging element 2 according to the second embodiment of the present invention has the same structure as the first embodiment, and has a transparent resin layer 30 between the transparent conductive layer 12 and the color filter 14 of the first color. The planar arrangement of the color filters 14, 15, and 16 of the solid-state imaging element 2 is the Bayer arrangement shown in Fig. 2.
The second embodiment is different from the first color filter in the process, and will be described using the drawings.

<Configuration of Solid-State Imaging Device>
The solid-state imaging element 2 according to this embodiment is characterized in that a transparent resin layer 30 is formed before the formation of the first color filter 14. The introduction of the transparent resin layer 30 has the advantages of improving the adhesion of the color filter, the flatness of the semiconductor substrate 10, and the residue after etching of the color filter material, making it possible to change the material contained in the partition 17, and facilitating the formation of the first color filter 14.

11, the solid-state imaging element 2 according to this embodiment includes a semiconductor substrate 10 having a plurality of photoelectric conversion elements 11 arranged two-dimensionally, a microlens group 180 consisting of a plurality of microlenses 18 arranged above the semiconductor substrate 10, and a transparent conductive layer 12, a color filter layer 100, and a partition wall 17 provided between the semiconductor substrate 10 and the microlenses 18. The color filter layer 100 is configured by arranging color filters 14, 15, and 16 of a plurality of colors in a predetermined regular pattern. The partition wall 17 is disposed between each of the color filters 14, 15, and 16 of a plurality of colors. In addition, a planarization layer 13 is formed between the color filter layer 100 and the microlens group 180 consisting of a plurality of microlenses 18.

Here, in the solid-state imaging element 2 according to the second embodiment, when the components have the same configuration as those of the solid-state imaging element 1 according to the first embodiment, the same reference symbols as those used in the first embodiment are used. That is, the semiconductor substrate 10 having the photoelectric conversion element 11, the transparent conductive layer 12, the color filters 14, 15, 16, the partition wall 17, the planarization layer 13, and the microlenses 18 each have the same configuration as those of the solid-state imaging element 1 according to the first embodiment. For this reason, detailed descriptions of the components common to those of the solid-state imaging element 1 according to the first embodiment will be omitted. The same applies to the other embodiments.

<Method of Manufacturing Solid-State Imaging Device>
Next, a method for manufacturing the solid-state imaging device 2 of this embodiment will be described with reference to FIGS.

(First Color Filter Layer Forming Step (First Step))
In the first color filter layer forming process, a transparent conductive layer 12 is formed on a semiconductor substrate 10 on which a plurality of photoelectric conversion elements 11 are two-dimensionally arranged, a transparent resin layer 30 is formed on the transparent conductive layer 12, and a coating liquid for the first color color filter 14 is applied and cured to form the transparent conductive layer 12, the transparent resin layer 30, and the first color color filter layer 14a in this order, and then the first color color filter layer 14a portion other than the position where the first color color filter 14 is arranged and the transparent resin layer 30 located under the first color color filter layer 14a portion are removed by dry etching to form a pattern of the first color color filter 14. The first color color filter layer forming process will be described in detail below.

As shown in FIG. 12(a), a transparent conductive layer 12 is formed on a semiconductor substrate 10 having a plurality of photoelectric conversion elements 11 arranged two-dimensionally. The transparent conductive layer 12 is a layer provided for surface protection and flattening of the semiconductor substrate 10, and for reducing damage such as charging (charge-up) caused by plasma etching. That is, the transparent conductive layer 12 reduces the unevenness of the upper surface of the semiconductor substrate 10 caused by the fabrication of the photoelectric conversion elements 11, improves adhesion with the color filter material, and serves as a protective layer for plasma etching when patterning the first color filter layer 14a. The material and forming method of the transparent conductive layer 12 are the same as those described in the first embodiment. After this, the transparent conductive layer 12 on the electrode portion of the semiconductor substrate 10 is removed in the same manner as in the first embodiment described above.

Next, as shown in FIG. 12(b), a transparent resin layer 30 is formed on the transparent conductive layer 12. The transparent resin layer 30 is formed of a resin containing one or more of, for example, acrylic resin, epoxy resin, polyimide resin, phenol novolac resin, polyester resin, urethane resin, melamine resin, urea resin, styrene resin, and silicon resin. The film thickness of the transparent resin layer 30 is, for example, 1 nm or more and 300 nm or less. From the viewpoint of preventing color mixing, the thinner the better, and preferably 5 nm to 60 nm.

Next, as shown in FIG. 12(c), a color filter layer 14a of the first color is formed on the transparent resin layer 30, and as shown in FIG. 12(d), the formed color filter layer 14a of the first color is heated and hardened, and as shown in FIG. 12(e), a photosensitive resin material is applied on the cured color filter layer 14a of the first color and dried to form a photosensitive resin material layer and form an etching mask 20. The color filter layer 14a of the first color has a thickness equal to or slightly thicker than the color filter 14 of the first color that is finally formed, but in FIG. 12 and FIG. 13 described later, for convenience of explanation, it is illustrated in a state where the thickness is thinner than the color filter 14 of the first color (see FIG. 14).

Next, as shown in Fig. 13(a), a photomask (not shown) is used to expose the substrate so that the areas where the second and third color filters 15 and 16 are to be formed are opened, and the substrate is developed to form an etching mask pattern 20a having openings 20b as shown in Fig. 13(b). These steps are the same as those in the first embodiment described above.

Next, using the etching mask pattern 20a, a portion of the first color color filter layer 14a exposed from the opening 20b is removed by dry etching using the dry etching gas described in the first embodiment, as shown in Figure 14 (a).

In this embodiment, since the transparent resin layer 30 is present under the first color filter 14, it is desirable to perform etching with a dry etching gas capable of etching the transparent resin layer 30. It is also desirable to etch the first color filter layer 14a with good rectangularity using an etching mask pattern 20a. In this embodiment, at the initial stage, 90% or more of the total gas flow rate is a gas that mainly performs etching by physical impact of ions of a rare gas or the like, and by using an etching gas mixed with a fluorine-based gas or an oxygen-based gas, the etching rate is improved by utilizing chemical reactions as well.

By using a large amount of rare gas in the dry etching gas, the physical impact of the rare gas ions makes it easier for anisotropic etching, in which etching proceeds vertically, to proceed. Therefore, in the initial stage of etching the color filter, etching is performed under conditions with a large amount of rare gas. Specifically, 90% or more of the total gas flow rate of a single rare gas or a mixed gas of a reactive gas and a rare gas is rare gas to etch part or all of the first color color filter layer 14a. At this time, it is desirable to stop the etching midway when the first color color filter layer 14a still remains, and to reduce the proportion of rare gas that physically performs etching and perform etching. Specifically, it is desirable to switch the etching gas conditions when 50% to 95% of the film thickness of the first color color filter layer 14a has been etched, and more preferably when 70% to 90% has been etched.

In the next step, the remaining first color filter layer 14a and transparent resin layer 30 are etched, stopping at the underlying transparent conductive layer 12. The remaining first color filter layer 14a and transparent resin layer 30 are all etched using oxygen and fluorine-based gas as gases that slowly etch the transparent conductive layer 12. The conditions used in this step are that the etching speed of the transparent conductive layer 12 is slow, and the transparent resin layer 30 is easily removed by a chemical etching reaction, so that the etching is performed for a time period that etches the first color filter 14 without leaving any residue and does not remove the transparent conductive layer 12. Figure 14 shows a configuration in which the transparent conductive layer 12 is resistant to the dry etching gas and etching has progressed little except in a portion.
Specifically, it is desirable to adjust the etching time to a film thickness that is approximately two to three times the remaining film thickness of the first color filter layer 14a, so that the first color filter layer 14a and the transparent resin layer 30 are etched without leaving any residue.

During this etching, the transparent resin layer 30 is removed by etching from the areas where color filters other than the first color filter 14 are formed. Therefore, as shown in FIG. 11, when the heights of the tops of the color filters of multiple colors are aligned, it is possible to adjust the film thickness of the color filters of the second color and subsequent colors to be thicker than the first color filter 14 by the film thickness of the transparent resin layer 30. Therefore, even if a photocurable resin is used for the color filters of the second color and subsequent colors, there is an advantage in that the adjustment range of the pigment concentration by the film thickness is wider.

The steps subsequent to the above step, i.e., the partition wall forming step (second step), the etching mask pattern removing step, and the step of forming the second and subsequent color filter patterns (third step), are similar to those steps described in the first embodiment above.
Through the above steps, the solid-state imaging device 2 of the present embodiment is completed.

The invention according to the second embodiment has the following effects in addition to the effects described in the first embodiment. Since the transparent resin layer 30 is between the transparent conductive layer 12 and the color filter 14 of the first color, the transparent resin layer 30 is easily etched by the chemical reaction of dry etching under the color filter 14, which is likely to remain as a residue, and therefore etching is possible without leaving a dry etching residue of the color filter 14 of the first color.

Third Embodiment
Hereinafter, a solid-state imaging device and a method for manufacturing the solid-state imaging device according to the third embodiment of the present invention will be described with reference to FIGS.

<Configuration of Solid-State Imaging Device>
The solid-state imaging element 3 according to this embodiment is characterized in that a transparent resin layer 30 is formed between the semiconductor substrate 10 and the transparent conductive layer 12 shown in Fig. 15. Therefore, the transparent conductive layer 12 can be formed after planarizing the semiconductor substrate 10, and since the semiconductor substrate 10 and the transparent conductive layer 12 are not directly connected, plasma damage caused by dry etching is unlikely to be transmitted from the transparent conductive layer 12 to the semiconductor substrate 10, which is advantageous in that plasma damage can be effectively reduced.

The structure of the solid-state imaging element according to this embodiment is similar to that of the first embodiment in the process of forming the first color filter 14, and similar to that of the second embodiment in the transparent resin layer 30. However, it is different in that the process of forming the transparent resin layer 30 is between the semiconductor substrate 10 and the transparent conductive layer 12. For this reason, the process of forming the transparent resin layer will be described.

<Method of Manufacturing Solid-State Imaging Device>
Next, a method for manufacturing the solid-state imaging device 3 of this embodiment will be described with reference to FIGS.

16A, a transparent resin material is applied onto the semiconductor substrate 10 and heated to form a transparent resin layer 30. The material of the transparent resin layer 30 is the material described in the second embodiment.
Next, as shown in FIG. 16( b ), the transparent conductive layer 12 is formed on the transparent resin layer 30 .
16(c), a color filter layer 14a of a first color is formed by coating on the transparent conductive layer 12. The color filter layer 14a of the first color has a thickness equal to or slightly greater than the color filter 14 of the first color that is finally formed, but for the sake of convenience in FIG. 16 and FIG. 17 described later, the color filter layer 14a of the first color is shown to have a thickness smaller than that of the color filter 14 of the first color (see FIG. 18).
Next, as shown in FIG. 16(d), the entire surface of the color filter layer 14a of the first color is thermally cured by heating.

Next, as shown in FIG. 16(e), a photosensitive resin material is applied onto the first color color filter layer 14a and dried to form a photosensitive resin material layer and an etching mask 20.

Next, as shown in FIG. 17(a), the etching mask 20 is exposed to light using a photomask (not shown) so that the areas where the second and third color filters are to be formed are opened, and then developed to form an etching mask pattern 20a having openings 20b as shown in FIG. 17(b).

As shown in Fig. 18(a), the color filter layer 14a of the first color exposed in the opening 20b is etched by dry etching, and then, as shown in Fig. 18(b), the etching mask pattern 20a is removed. The process shown in Fig. 18 and the subsequent processes are similar to the processes described in the first embodiment.
Through the above steps, the solid-state imaging device 3 of this embodiment is completed.

The invention according to the third embodiment has the following effects in addition to the effects described in the first embodiment. Since the transparent resin layer 30 is between the transparent conductive layer 12 and the color filter 14 of the first color, the transparent resin layer 30 is easily etched by the chemical reaction of dry etching under the color filter, which is likely to remain as a residue, and therefore etching is possible without leaving a dry etching residue of the color filter.

Below, the solid-state imaging element of the present invention and the solid-state imaging element according to the conventional method are specifically explained using examples.

Example 1
On a semiconductor substrate equipped with two-dimensionally arranged photoelectric conversion elements, an ITO film was formed as a transparent conductive layer with a film thickness of 50 nm by magnetron sputtering. The film was formed at room temperature to make it an amorphous film in order to facilitate processing. Next, in order to open the electrode portion of the semiconductor substrate, wet etching was performed using an etching solution containing about 5% oxalic acid. During wet etching, a positive resist (OFPR-800: manufactured by Tokyo Ohka Kogyo Co., Ltd.) was spin-coated at a rotation speed of 750 rpm, and then pre-baked at 90°C for 1 minute. As a result, a sample was prepared in which a positive resist serving as an etching mask was applied with a film thickness of 2.0 μm.

This sample was subjected to photolithography by exposing it through a photomask. An exposure device using an i-line wavelength as a light source was used. The positive resist was chemically reacted with ultraviolet light and became soluble in the developer.
Next, a development process was performed using 2.38 mass% TMAH (tetramethylammonium hydride) as a developer, and an etching mask having an opening in the electrode portion of the semiconductor substrate was formed. Next, the substrate was immersed in the etching solution for 3 minutes to perform wet etching, and then washed with pure water to open the electrode portion. Next, the positive resist used as the etching mask was removed. The method used here was a method using a solvent, and the positive resist was removed with a spray cleaning device using a stripping solution 104 (manufactured by Tokyo Ohka Kogyo Co., Ltd.). Next, a heat treatment was performed on a hot plate at 250 degrees for 30 minutes to crystallize the ITO film. At this time, the sheet resistance was 50 Ω/sq. or less, and the transmittance of visible light was 89%.

Next, a green pigment dispersion containing a photosensitive curable resin and a thermosetting resin was spin-coated at a rotation speed of 1000 rpm to prepare a material for a first color filter containing a green pigment, which is the first color. The green pigment in the material for the first color filter was C.I. PG58 in terms of color index, and the pigment concentration was 70% by mass and the film thickness was 500 nm.

Next, to harden the green filter material, a stepper, an i-line exposure device, was used to expose the entire surface, hardening the photosensitive component. This hardening of the photosensitive component hardened the surface of the green filter. Next, the green filter was thermally hardened by baking on a hot plate at 230°C for 6 minutes.

Next, a positive resist (OFPR-800: manufactured by Tokyo Ohka Kogyo Co., Ltd.) was spin-coated at 1000 rpm using a spin coater, and then pre-baked at 90°C for 1 minute. This produced a sample coated with a positive resist to serve as an etching mask with a film thickness of 1.5 μm.

Photolithography was performed on this sample by exposing it to light through a photomask. The exposure equipment used was one that used an i-line wavelength as its light source. When exposed to ultraviolet light, the positive resist underwent a chemical reaction and became soluble in the developer.

Next, a development process was carried out using 2.38 mass% TMAH (tetramethylammonium hydride) as a developer, and an etching mask having openings at the locations where the second and third color filters were to be formed was formed. When using a positive resist, dehydration baking is often carried out after development to harden the positive resist. However, this time, in order to facilitate removal of the etching mask after dry etching, a baking process was not carried out. Therefore, the resist was not hardened and the selectivity could not be improved, so the film thickness of the resist was formed to be 1.5 μm, which is more than twice the film thickness of the first color filter, which is a green filter. The opening pattern at this time was formed to be 1.1 μm x 1.1 μm.
As a result, an etching mask pattern was formed using a positive resist.

Next, the green filter layer was dry etched using the formed etching mask pattern. The dry etching equipment used was an ICP type dry etching equipment. In order not to affect the underlying semiconductor substrate, the dry etching conditions were changed midway through the process, and the dry etching was performed in multiple stages.

The etching was performed by mixing three gases, CF ₄ , O ₂ and Ar gas, as the initial gas species. The gas flow rates of CF ₄ and O ₂ were each 5 ml/min, and the gas flow rate of Ar was 200 ml/min. That is, the gas flow rate of Ar was 95.2% of the total gas flow rate. The dry etching conditions at this time were set to a pressure of 1 Pa in the chamber, an RF power of 500 W, and a coil power of 1000 W. Using these conditions, the green filter layer was dry-etched to a thickness of 350 nm out of a film thickness of 500 nm, and then the dry etching conditions were changed to the next conditions.

The next gas species used was a mixed gas of _CF4 gas and _O2 gas, and the etching conditions were a 50:50 ratio of _CF4 gas flow rate of 150 ml/min and _O2 gas flow rate of 150 ml/min, a chamber pressure of 2 Pa, RF power of 500 W, and coil power of 1000 W. Using these conditions, dry etching of the remaining green filter layer was performed. The ITO film formed as the transparent conductive layer has an etching rate of _CF4 gas and _O2 gas that is 20 times slower than the etching rate of green, and is configured to be almost not etched. At this time, overetching was performed with a time setting that etches 450 nm, which is three times the film thickness of 150 nm of the remaining green filter, so that no green residue remains. With this process, no residue remains on the green filter, and 5 nm of the ITO film of 50 nm thickness is etched.

During the dry etching, a partition wall was formed on the side wall of the green filter pattern, which contained a reaction product of the green filter material, the ITO material of the transparent conductive layer, and the dry etching gas. The dimensions (width) of the partition wall can be controlled by adjusting the time of the dry etching conditions.
Under the above dry etching conditions, the green filter was dry etched to a thickness of 500 nm and the transparent conductive layer was dry etched to a thickness of about 5 nm, and the size of the partition wall formed by the reaction product was 25 nm.

Next, the positive resist used as an etching mask was removed. The method used here was a solvent-based method, and the positive resist was removed using a spray cleaning device with Stripper 104 (manufactured by Tokyo Ohka Kogyo Co., Ltd.).

(Preparation of a second color filter)
Next, a process for forming a color filter of a second color was carried out. A photosensitive blue resist containing a pigment dispersion blue was applied to the entire surface of the semiconductor substrate to provide a color filter of a second color. Before applying the blue resist, HMDS treatment may be performed to improve adhesion.
Next, the blue resist was selectively exposed by photolithography, and developed to form a blue filter pattern. At this time, the pigments used in the blue resist were C.I.PB156 and C.I.PV23 in the color index, respectively, and the pigment concentration was 50 mass%. The film thickness of the blue filter was 550 nm. The resin that is the main component of the blue resist was a photosensitive acrylic resin.

Next, in order to firmly harden the blue filter layer, it was baked on a hot plate at 230°C for 6 minutes to harden it. After this heating process, no peeling or pattern collapse was observed, even after processes such as the third color filter formation process. The blue filter is surrounded by a green filter and partition walls with good rectangularity, and is formed with good rectangularity, so it was confirmed that it hardens with good adhesion between the bottom surface and the surroundings.

(Preparation of a third color filter)
Next, a process for forming a color filter of a third color was carried out: a photosensitive red resist containing a dispersed red pigment was applied to the entire surface of the semiconductor substrate to provide a color filter of the third color.
Next, the red resist was selectively exposed by photolithography, and developed to form a red filter pattern.At this time, the pigments used in the red resist were C.I.PR254 and C.I.PY139 in color index, respectively, and the pigment concentration was 60 mass%.In addition, the film thickness of the red filter was 550 nm.

Next, in order to firmly harden the red filter layer, it was baked on a hot plate at 230°C for 6 minutes to harden it. At this time, since the third color filter was surrounded by the green filter and the partition wall, which had good rectangularity, and was formed with good rectangularity, it was confirmed that it hardened with good adhesion between the bottom surface and the surroundings.

Through the above process, the thickness A (500 nm) of the first color filter made of green, the transparent conductive layer B (50 nm) underneath, and the thickness C (550 nm) of the second and third color filters made of blue and red are based on the present invention. In this embodiment, the transparent conductive layer underneath the second and third color filter layers has a thickness of 45 nm.

Next, a coating liquid containing acrylic resin was spin-coated onto the color filter formed in the above process at a rotation speed of 1000 rpm, and then heat-treated on a hot plate at 200°C for 30 minutes to harden the resin and form a planarizing layer.

Finally, microlenses with a height of 500 nm from lens top to lens bottom were formed on the planarization layer using the etch-back transfer method, which is a well-known technique described above, thereby completing the solid-state imaging element of Example 1.

In the solid-state imaging device obtained as described above, a transparent conductive layer is formed at the bottom of the first color filter, with a thickness of 50 nm, and a transparent conductive layer is formed at the bottom of the second and third color filters, with a thickness of 45 nm. In addition, since the first color green filter uses a thermosetting resin and a small amount of photosensitive curing resin, it is possible to increase the concentration of the pigment in the solid content, and the color filter can be made thinner than when patterning using a conventional photosensitive resist, so that the film thickness at which the desired spectral characteristics are obtained can be obtained. In addition, the second and third color filters, blue and red, use photosensitive resin, but unlike the conventional process, the first color filter is simply filled in the portion where a pattern is formed with good rectangularity and serves as a guide pattern. Therefore, the proportion of photosensitive resin can be reduced for blue and red compared to the conventional process, so that the pigment concentration can be increased, and there is an advantage that the desired spectral characteristics can be easily formed even if the film thickness is thin. Due to these effects, the green, blue, and red colors can be made thinner than in the conventional process, the distance from the microlens to the semiconductor substrate is reduced, and the color filter has good sensitivity.
Moreover, the visible light transmittance of the transparent conductive layer was 89%, and the dimension of the formed partition wall was 25 nm, which satisfied the requirements of the present invention.

In addition, there is a transparent conductive layer on top of the semiconductor substrate, which acts as an etching stopper during etching and, because it is conductive, has the effect of preventing plasma damage during green dry etching, so no effects of dry etching were observed on the photoelectric conversion elements formed on the semiconductor substrate.

Furthermore, the color filter material of the first color filter consisting of a green filter is hardened internally by heat curing, and the surface is hardened by exposure to light using a small amount of photosensitive resin, improving solvent resistance. When a green filter material with a high pigment content is used, it may react with solvents or other color filter materials and change in spectral characteristics. Therefore, by combining the above-mentioned heat curing and light curing, it is possible to improve solvent resistance and has the effect of suppressing changes in spectral characteristics.

In this embodiment, a material that combines a thermosetting resin and a photocurable resin is used in order to improve the curing property and solvent resistance of the green filter, which is the color filter of the first color. However, depending on the desired spectral characteristics, it is also acceptable to form the material using only a thermosetting resin or only a photocurable resin, with emphasis on the pigment concentration and characteristics over time.
In this embodiment, in order to obtain the desired spectral characteristics for blue and red, the film thickness is made thicker than that of green. Therefore, instead of the structure in which the heights of green, blue, and red are uniform as shown in FIG. 1A, the structure in which blue and red protrude by about 50 nm is obtained.

Example 2
Example 2 corresponds to the solid-state imaging device having the configuration described in the second embodiment.
The solid-state imaging element of Example 2 has a configuration in which a transparent resin layer is formed on a transparent conductive layer. The presence of the transparent resin layer improves the adhesion of the color filters, and has the effect of reducing the occurrence of residues when etching the color filters of the first color.

On a semiconductor substrate equipped with two-dimensionally arranged photoelectric conversion elements, an ITO film was formed as a transparent conductive layer with a thickness of 30 nm using magnetron sputtering. The film was formed at room temperature to make it an amorphous film for ease of processing. Next, in order to open the electrode part of the semiconductor substrate, wet etching was performed using an etching solution containing about 5% oxalic acid. During wet etching, a positive resist (OFPR-800: manufactured by Tokyo Ohka Kogyo Co., Ltd.) was spin-coated at a rotation speed of 750 rpm, and then pre-baked at 90°C for 1 minute. As a result, a sample was produced in which a positive resist was applied to serve as an etching mask with a thickness of 2.0 μm.

This sample was subjected to photolithography by exposing it through a photomask. An exposure device using an i-line wavelength as a light source was used. The positive resist was chemically reacted with ultraviolet light and became soluble in the developer.
Next, a development process was performed using 2.38% by mass of TMAH (tetramethylammonium hydride) as a developer, and an etching mask having an opening in the electrode portion of the semiconductor substrate was formed. Next, the substrate was immersed in the etching solution for 3 minutes to perform wet etching, and then washed with pure water to open the electrode portion. Next, the positive resist used as the etching mask was removed. The method used here was a method using a solvent, and the positive resist was removed with a spray cleaning device using a stripping solution 104 (manufactured by Tokyo Ohka Kogyo Co., Ltd.). Next, a heat treatment was performed on a hot plate at 250 degrees for 30 minutes to crystallize the ITO film. At this time, the sheet resistance was 50 Ω/sq. or less, and the transmittance of visible light was 95%.

(Formation of transparent resin layer)
A coating liquid containing an acrylic resin was spin-coated at 3000 rpm onto the ITO, which was a transparent conductive layer formed on a semiconductor substrate, and the resin was cured by heat treatment at 230° C. for 6 minutes on a hot plate to form a transparent resin layer. The transparent resin layer had a film thickness of 30 nm and a visible light transmittance of 95%.

(Formation of the first color filter)
Next, a green pigment dispersion containing a photosensitive curable resin and a thermosetting resin was spin-coated at a rotation speed of 1000 rpm as a color filter material for the first color filter (green filter). The green pigment of the first color filter material was C.I. PG58 in terms of color index, and the pigment concentration was 70 mass % and the film thickness was 500 nm.

Next, to harden the green filter material, a stepper, an i-line exposure device, was used to expose the entire surface, hardening the photosensitive component. This hardening of the photosensitive component hardened the surface of the green filter. Next, the green filter was thermally hardened by baking on a hot plate at 230°C for 6 minutes.

(Formation of the first color filter)
After forming an etching mask by the method shown in Example 1, the green filter layer and the transparent resin layer were etched. The etching conditions were the same as those in Example 1, but since there was a transparent resin layer under the green filter, the residue of the green filter was less likely to remain. Therefore, in Example 1, overetching was performed by adjusting the time to etch 450 nm, which is three times the remaining 150 nm of the green filter, but this time, overetching was performed for a time to etch 300 nm of the green filter, which is twice the remaining 150 nm. As a result, in the areas where the second and third color filters were formed, the green filter and the transparent resin layer were all etched, and the transparent conductive layer was almost unchanged from the film thickness of 30 nm. Then, the positive resist used as the etching mask was removed by the method shown in Example 1.

During the dry etching, a partition wall was formed on the side wall of the green filter pattern, which contained a reaction product of the green filter material, the acrylic resin material of the transparent resin layer, and the ITO material of the transparent conductive layer with the dry etching gas. The dimensions (width) of the partition wall can be controlled by adjusting the time of the dry etching conditions.
Under the above dry etching conditions, the green filter was dry etched to a depth of 500 nm and the transparent resin layer was dry etched to a depth of about 30 nm, and the size of the partition wall formed by the reaction product was 30 nm.

(Preparation of second and third color filters, etc.)
In Example 2, thereafter, second and third color filters, an upper planarizing layer, and microlenses were formed in the same manner as in Example 1, thereby completing the solid-state imaging device of Example 2.

Through the above process, in Example 2, similarly to Example 1, the first color filter green has a thickness of 500 nm, the transparent resin layer thereunder has a thickness of 30 nm, and the transparent conductive layer thereunder has a thickness of 30 nm, the second and third color filters blue and red have a thickness of 550 nm, the visible light transmittance (95%) of the transparent resin layer and the transparent conductive layer, and the partition dimension E (30 nm) all satisfy the provisions of the present invention. Moreover, in this example, only the lower layers of the second and third color filter layers do not have a transparent resin layer, and only a transparent conductive layer is formed.
In this embodiment, in order to obtain the desired spectral characteristics for blue and red, the film thickness is made thicker than that of green. Therefore, instead of a structure in which the heights of green, blue, and red are uniform as shown in FIG. 1B, the structure is such that blue and red protrude by about 20 nm.

In this example, the film thickness of the transparent conductive layer is reduced from 50 nm to 30 nm compared to Example 1. This is because the thicker the transparent resin layer and the transparent conductive layer are, the longer the distance from the color filter to the photoelectric conversion element becomes, and the more likely it is that the light receiving sensitivity will decrease due to color mixing or the like.
In addition, the transparent resin layer and the transparent conductive layer have a visible light transmittance of not 100%, and therefore the transmittance is likely to decrease as the layers become thicker. From the viewpoints of reducing plasma damage during dry etching and removing color filter residues, the thicker the transparent resin layer and the transparent conductive layer are, the wider the range of conditions in the manufacturing process becomes, and it becomes possible to form the layer thickness within a range in which the light receiving sensitivity does not deteriorate due to the occurrence of color mixing or the decrease in transmittance.

Example 3
Example 3 is an example corresponding to the solid-state imaging device having the configuration described in the third embodiment.
The solid-state imaging element shown in Example 3 has a configuration in which a transparent resin layer is provided between the semiconductor substrate and the transparent conductive layer of Example 1. The presence of the transparent resin layer makes it possible to further planarize the semiconductor substrate, which makes it easier to form a transparent conductive layer such as ITO with good performance. In addition, since the semiconductor substrate and the transparent conductive layer are not in direct contact with each other, the semiconductor substrate is less susceptible to plasma damage during dry etching of the color filters.

(Formation of transparent resin layer)
A coating solution containing an acrylic resin was spin-coated on a semiconductor substrate at a rotation speed of 2000 rpm, and the resin was cured by heat treatment on a hot plate at 200° C. for 20 minutes to form a transparent resin layer. The transparent resin layer had a film thickness of 60 nm and a visible light transmittance of 91%.

Next, an ITO film was formed as a transparent conductive layer on the transparent resin layer using magnetron sputtering to a thickness of 30 nm. The film was formed at room temperature to make it easier to process, so that the film would be amorphous. Next, to open up the electrode parts of the semiconductor substrate, wet etching was performed using an etching solution containing about 5% oxalic acid. During wet etching, a positive resist (OFPR-800: manufactured by Tokyo Ohka Kogyo Co., Ltd.) was spin-coated at a rotation speed of 750 rpm, and then pre-baked at 90°C for 1 minute. This produced a sample coated with a positive resist to serve as an etching mask with a thickness of 2.0 μm.

This sample was subjected to photolithography by exposing it through a photomask. An exposure device using an i-line wavelength as a light source was used. The positive resist was chemically reacted with ultraviolet light and became soluble in the developer.
Next, a development process was performed using 2.38% by mass of TMAH (tetramethylammonium hydride) as a developer, and an etching mask having an opening in the electrode portion of the semiconductor substrate was formed. Next, the substrate was immersed in the etching solution for 3 minutes to perform wet etching, and then washed with pure water to open the electrode portion. Next, the positive resist used as the etching mask was removed. The method used here was a method using a solvent, and the positive resist was removed with a spray cleaning device using a stripping solution 104 (manufactured by Tokyo Ohka Kogyo Co., Ltd.). Next, a heat treatment was performed on a hot plate at 250 degrees for 30 minutes to crystallize the ITO film. At this time, the sheet resistance was 50 Ω/sq. or less, and the transmittance of visible light was 95%.

(Formation of the first color filter)
Next, a green pigment dispersion containing a photosensitive curable resin and a thermosetting resin was spin-coated at a rotation speed of 1000 rpm as a color filter material for the first color filter (green filter). The green pigment of the first color filter material was C.I. PG58 in terms of color index, and the pigment concentration was 70 mass % and the film thickness was 500 nm.

Next, to harden the green filter material, a stepper, an i-line exposure device, was used to expose the entire surface, hardening the photosensitive component. This hardening of the photosensitive component hardened the surface of the green filter. Next, the green filter was thermally hardened by baking on a hot plate at 230°C for 6 minutes.

In Example 3, the first color filter was then patterned by dry etching using a method similar to that used in Example 1, and then the second and third color filters, an upper planarizing layer, and microlenses were formed to form the solid-state imaging element of Example 3.

Through the above process, in Example 3, like Example 1, the film thickness A (500 nm) of the first color green color filter and the film thickness B (30 nm) of the transparent conductive layer thereunder, the film thickness C (550 nm) of the second and third color blue and red color filters, the visible light transmittance D (95%), and the partition dimension E (30 nm) satisfy the provisions of the present invention.

The effect of this embodiment is that the transparent conductive layer can be formed with good quality even in a thin film by planarizing with a transparent resin layer, and the plasma damage caused by dry etching does not affect the semiconductor substrate. In addition, as a secondary effect, since there is a transparent resin layer below the transparent conductive layer, the transparent resin layer can be removed by a known method such as wet etching, which makes it easy to remove hard transparent conductive layers such as crystallized ITO. This has the advantage of expanding the process margin, such as for redoing a process.

In this embodiment, in order to obtain the desired spectral characteristics for blue and red, the film thickness is made thicker than that of green. Therefore, instead of a structure in which the heights of green, blue, and red are uniform as shown in Figure 15, the structure is such that blue and red protrude by about 50 nm.

<Conventional method>
Based on the conventional method described in Patent Document 1, a color filter pattern of each color was formed by a photolithography process.
However, the film thickness of the three colors, green, blue, and red, was set to a thin value of 700 nm, and a transparent resin layer (100 nm) was provided below all of the color filters of each color.
Other than that, similarly to the first embodiment, a solid-state imaging device was manufactured by the conventional method.

(evaluation)
In each of the above examples, there are differences in the presence or absence of a transparent resin layer, the position at which the transparent resin layer is formed, and the heights (thicknesses) of the transparent resin layer and the transparent conductive layer, but the film thickness of the green (500 nm), the film thickness of the transparent conductive layer thereunder (30 nm to 50 nm), the film thickness of the transparent resin layer (30 nm), and the film thickness of the blue and red color filters which are the second and third colors (550 nm) satisfy the film thicknesses specified in the present invention.

The intensities of the red, green and blue signals of the solid-state imaging elements of each of these embodiments were evaluated and compared with the intensities of the red, green and blue signals of a solid-state imaging element fabricated using conventional photolithography with a film thickness of 700 nm for the three colors green, blue and red, and a structure with matching spectral characteristics.

The following Table 1 shows the evaluation results of the signal strength of each color in the solid-state imaging devices according to Examples 1 to 3, which correspond to the solid-state imaging devices 1, 2, and 3 according to the first to third embodiments shown in Figures 1, 11, and 15. The values shown in Table 1 are the signal strength of each color in the solid-state imaging devices according to Examples 1 to 3 normalized by the signal strength of each color in a solid-state imaging device according to a conventional method.

As shown in Table 1, in the solid-state imaging devices of Examples 1 to 3 in which the green filter was formed thin and with good rectangularity using a dry etching method, and the reaction products generated by the dry etching were further formed as partitions, the signal strength of each color increased compared to when formed by conventional photolithography. This is because when oblique light incident from a pixel in an oblique direction passes through the color filter and heads toward another color filter pattern, the partition blocks the incidence or changes the light path. As a result, light headed toward other color filter patterns is prevented from entering other photoelectric conversion elements, and color mixing is suppressed. In addition, the partition also blocks migration from other colors, so color mixing is suppressed.

As a result of evaluating the spectral characteristics after forming the OCF by the manufacturing method of Examples 1 to 3, no change in the spectral characteristics was observed. This shows that the thinned green filter is sufficiently cured by the heat curing and photocuring of Examples 1 to 3, and meets the solvent resistance requirements. In order to perform color spectroscopy equivalent to that of a green filter film thickness (700 nm) formed by photolithography using the thinned green filter, a green filter material with a high pigment content was used, but no change in the spectral characteristics occurred, and the distance from the microlens top to the device was shortened due to the effect of thinning, and the green signal intensity increased.
In addition, the thinner film also reduces the probability that oblique incident light will pass through the color filter and head toward other color filter patterns, preventing light heading toward other color filter patterns from entering other photoelectric conversion elements. This suppresses color mixing and therefore increases signal strength.

In addition, slight changes in light receiving sensitivity were confirmed by changing the positions at which the transparent conductive layer and the transparent resin layer were formed, using the techniques of Examples 1 to 3. However, no effect of plasma damage caused by dry etching on light receiving sensitivity was confirmed in any of the examples.
Even when the height of the second color filter 15 and the third color filter 16 is formed to be lower than the sum of the film thicknesses of the first color filter 14, the transparent resin layer 30, and the transparent conductive layer 12, the signal strength was increased by increasing the pigment content by the reduced film thickness compared to when the color filters were formed by conventional photolithography.

Although the present invention has been described above with reference to each embodiment, the scope of the present invention is not limited to the exemplary embodiments shown and described, but includes all embodiments that have equivalent effects to those intended by the present invention. Furthermore, the scope of the present invention is not limited to the combination of the features of the invention defined by the claims, but can be defined by any desired combination of specific features among all the respective features disclosed.

REFERENCE SIGNS LIST 10: semiconductor substrate 11: photoelectric conversion element 12: transparent conductive layer 13: planarization layer 14: color filter of first color 15: color filter of second color 16: color filter of third color 17: partition wall 18: microlens 19: microlens matrix layer 20: etching mask 30: transparent resin layer

Claims (11)

A semiconductor substrate on which a plurality of photoelectric conversion elements are two-dimensionally arranged;
a color filter layer formed on the semiconductor substrate, the color filter layer having a plurality of color filters arranged two-dimensionally in a predetermined regular pattern corresponding to the plurality of photoelectric conversion elements;
a transparent conductive layer disposed between a color filter of a first color selected from the plurality of colors and a semiconductor substrate;
Equipped with
The solid-state imaging device is characterized in that the transparent conductive layer is formed of a single layer or multiple layers of aggregates of nano-sized indium tin oxide particles . 2. The solid-state imaging device according to claim 1, wherein the transparent conductive layer has a sheet resistance F, and satisfies the following formula (1):
F < 100,000 Ω/□ ... (1) 3. The solid-state imaging element of claim 1, wherein the transparent conductive layer and the color filter of the first color are made of materials that satisfy the following formula (2) when dry etching is performed using a gas containing at least one type selected from fluorine, oxygen, hydrogen, sulfur, carbon, bromine, chlorine, nitrogen, argon, helium, xenon, and krypton, where T is an etching rate of the transparent conductive layer and G is an etching rate of the color filter of the first color:
3≦G/T (2) The solid-state imaging device according to any one of claims 1 to 3, further comprising a partition disposed between the color filters of the plurality of colors. The solid-state imaging device according to any one of claims 1 to 4, further comprising a transparent resin layer between the transparent conductive layer and the color filter of the first color. The solid-state imaging device according to any one of claims 1 to 5, further comprising a transparent resin layer between the transparent conductive layer and the semiconductor substrate. the transparent resin layer contains silicon and at least one selected from carbon, oxygen, and hydrogen,
the transparent resin layer is formed of a silicon-based resin,
7. The solid-state imaging device according to claim 5, wherein the transparent resin layer has a thickness within a range of 5 nm to 60 nm. a height of a color filter other than the color filter of the first color is lower than a total value of heights of the color filter of the first color, the transparent resin layer, and the transparent conductive layer;
8. The solid-state imaging device according to claim 5, wherein the transparent conductive layer has a thickness in the range of 30 nm to 50 nm. a first step of forming a transparent conductive layer on a semiconductor substrate on which a plurality of photoelectric conversion elements are two-dimensionally arranged, applying a coating liquid for a color filter of a first color onto the transparent conductive layer and curing the coating liquid to form a transparent conductive layer and a color filter layer of the first color in this order, and then removing a portion of the color filter layer of the first color other than the position where the color filter of the first color is arranged by dry etching to form a pattern of the color filter of the first color;
a second step of forming a by-product of the color filter layer and dry etching gas generated when the color filter layer of the first color is dry-etched as a partition on a side wall of the color filter of the first color in the first step of patterning the color filter of the first color;
a third step of forming a color filter having a color other than the first color by patterning using photolithography after the second step;
Equipped with
A method for manufacturing a solid-state imaging device, comprising forming the transparent conductive layer from an aggregate of nano-sized indium tin oxide particles . a first process of forming a transparent conductive layer on a semiconductor substrate having a plurality of photoelectric conversion elements two-dimensionally arranged thereon, forming a transparent resin layer on the transparent conductive layer, applying and curing a coating liquid for a color filter of a first color to form a transparent conductive layer, a transparent resin layer, and a color filter layer of the first color in this order, and then removing by dry etching a portion of the color filter layer of the first color other than the position where the color filter of the first color is arranged and the transparent resin layer located below the color filter layer portion of the first color;
a second step of forming a by-product of the color filter layer, the transparent resin layer, and a dry etching gas, which is generated when the color filter layer of the first color and the transparent resin layer located under the color filter layer portion to be removed are dry-etched in the first step of patterning the color filter of the first color, on a side wall of the color filter of the first color;
a third step of forming a color filter having a color other than the first color by patterning using photolithography after the second step;
Equipped with
A method for manufacturing a solid-state imaging device, comprising forming the transparent conductive layer from an aggregate of nano-sized indium tin oxide particles . a height of a color filter other than the color filter of the first color is lower than a total value of heights of the color filter of the first color, the transparent resin layer, and the transparent conductive layer;
11. The method for manufacturing a solid-state imaging device according to claim 10, wherein the transparent conductive layer has a thickness within a range of 30 nm to 50 nm.