JP2019200279A - Solid state image sensor and method for manufacturing the same - Google Patents

Abstract

To provide a solid state image sensor capable of improving solvent resistance and suppressing color mixture, and having high definition and high sensitivity.SOLUTION: A solid state image sensor 1 comprises: a semiconductor substrate 10 having a plurality of photoelectric conversion elements 11 two-dimensionally arranged; a color filter layer 100 formed on the semiconductor substrate 10 and having color filters having a plurality of colors and two-dimensionally arranged by a preset irregular pattern corresponding to the plurality of photoelectric conversion elements 11; a flattened layer 12 formed between the colored filters having a plurality of colors and the semiconductor substrate 10; partitions 30 arranged between the colored filters having the plurality of colors; micro lenses 18 formed on the colored filter layer 100 and two-dimensionally arranged corresponding to the colored filters having the plurality of colors; and a transparent protective layer arranged only between a first color filter 14 selected from the plurality of colors and a micro lens 18.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a technology relating to a solid-state imaging device using a photoelectric conversion device such as a CCD or a CMOS.

In recent years, solid-state imaging devices such as CCD (Charge Coupled Device) and CMOS (Complementary Metal Oxide Semiconductor) mounted on digital cameras and the like have been increasing in size and miniaturized, and the pixels are particularly fine. The pixel size is less than 1.4 μm × 1.4 μm.
The solid-state image sensor has a photoelectric conversion element and a pair of color filter patterns to achieve colorization. Further, the region (opening) where the photoelectric conversion element of the solid-state image sensor contributes to photoelectric conversion depends on the size and the number of pixels of the solid-state image sensor. The opening is limited to about 20 to 50% with respect to the entire area of the solid-state imaging device. Since a small aperture leads to a decrease in sensitivity of the photoelectric conversion element as it is, in a solid-state imaging device, a condensing microlens is generally formed on the photoelectric conversion element in order to compensate for the decrease in sensitivity.

In recent years, an image sensor using a backside illumination technique has been developed, and the opening of the photoelectric conversion element can be made 50% or more of the total area of the solid-state imaging element. However, in this case, there is a possibility that leakage light from the color filter adjacent to the color filter may enter, so it is necessary to form a microlens having an appropriate size and shape.
As a method of forming such a color filter pattern on a solid-state imaging device, a method of forming a pattern by a photolithography process is usually used (for example, Patent Document 1).

As another method for forming the color filter pattern on the solid-state imaging device, a method of forming all the color filter patterns by dry etching is used (for example, Patent Document 2).
In recent years, the demand for high-definition CCD image sensors with more than 8 million pixels has increased, and the pixel size of the color filter pattern associated with these high-definition CCDs has to be lower than 1.4 μm × 1.4 μm. The demand is growing. However, by reducing the pixel size, there is a problem that the resolution of the color filter pattern formed by the photolithography process is insufficient, which adversely affects the characteristics of the solid-state imaging device. In a solid-state imaging device having a side of 1.4 μm or less, or near 1.1 μm or 0.9 μm, insufficient resolution appears as color unevenness due to a pattern shape defect.

  In addition, with the miniaturization of pixels, it is necessary to reduce the thickness of the color filter. This is because, even if the pixel size of the color filter is reduced, if the film thickness remains large, the resolution is lowered, and the distance to the light receiving element is relatively long, and the light collection efficiency is lowered. Tend. If the color filter is thinned, the device characteristics can be improved because the resolution is high, the productivity is excellent, and the distance between the light receiving element and the microlens provided for condensing is reduced. However, the spectral characteristics need to be maintained even when the film thickness is reduced. Therefore, attempts have been made to increase the colorant content in the total solid content of the colorant-containing photosensitive composition.

However, when a pixel pattern is created using a photosensitive composition with an increased colorant content, the amount of the photosensitive component is reduced by the amount of the increased colorant in the photosensitive composition, resulting in a photopolymerization reaction. As a result, the improvement of the alkali resistance due to the alkali becomes insufficient, the corners of the upper part of the rectangular pixel pattern after the development treatment with the alkali solution tend to be rounded, and the rectangularity of the cross-sectional shape is lowered. When the upper corner of the pixel is rounded, a gap is formed between adjacent pixels.
Also, if there is a gap between adjacent pixels, when light enters vertically from the upper surface of the pixel, the optical path is bent at the gap and enters the adjacent pixel. Will decline. Further, when light enters adjacent pixels, color mixing occurs, spectral sensitivity characteristics deteriorate, noise increases, and image quality deteriorates. In addition, the thickness of the adjacent portion is reduced and the color characteristics are deteriorated. Therefore, there is a demand for a cross-sectional shape with good rectangularity in which the shape of the upper part of the pattern is square.

  Due to the high definition of the color filter pattern, the film thickness of the color filter pattern affects not only a problem in the manufacturing process but also characteristics as a solid-state imaging device. When the film thickness of the color filter pattern is thick, light incident from an oblique direction may be split by a specific color filter and then incident on another adjacent color filter pattern portion and photoelectric conversion element. In this case, there arises a problem that color mixing occurs. This problem of color mixture becomes more prominent as the pixel size of the color filter pattern decreases and the aspect ratio between the pixel size and the film thickness increases. In addition, the problem of color mixing of incident light is conspicuous even when the distance to the photoelectric conversion element becomes long due to the film thickness of the material formed from the substrate on which the photoelectric conversion element is formed to the microlens. For this reason, it is important to reduce the thickness of the microlens, the color filter pattern, and the flattening layer formed below the microlens, the color filter pattern, and the like.

  In order to prevent color mixing due to incidence from an oblique direction or the like, a method is known in which light is reflected or refracted between color filters of each color and a partition that blocks light incident on other pixels is formed. In a color filter used for an optical display device such as a liquid crystal display, a partition having a black matrix (BM) structure made of a black material is generally known. However, in the case of a solid-state imaging device, the size of each color filter pattern is several μm or less. For this reason, when the partition is formed by using a general black matrix forming method, the pattern size is large, so that some pixels are filled with BM like a pixel defect and resolution is deteriorated. .

In the case of a solid-state image sensor that has been advanced in high definition, the required partition wall size is several hundred nm, more preferably about 200 nm or less, and the pixel size is increased until one pixel size is about 1 μm. Is progressing. For this reason, a film thickness of 100 nm or less is desirable if the light-shielding performance capable of suppressing color mixing can be satisfied. It is difficult to form barrier ribs of this size by photolithography using BM. Therefore, to form by cutting aluminum, tungsten, used by composite metal or SiO ₂ such as inorganic and these such as titanium, evaporation, CVD, deposition or by sputtering, on a lattice pattern using an etching technique The partition is formed by the method. However, such a method has a problem that the manufacturing cost becomes very high due to the complexity of the manufacturing apparatus and the manufacturing process.

From the above, in order to increase the number of pixels of the solid-state imaging device, it is necessary to increase the definition of the pattern of the color filter layer, and thinning of the color filter layer and a method for preventing color mixing are important.
As described above, the pattern formation of the color filter layer that is formed by photolithography with the conventional color filter material having photosensitivity is made thinner as the pixel dimensions are miniaturized. Is also required. In this case, since the content ratio of the pigment component in the color filter material is increased, the photosensitive component cannot be contained in a sufficient amount, the resolution cannot be obtained, the rectangularity is poor, and the spectral sensitivity characteristic is easily deteriorated. There was a problem, and there was a problem of deteriorating the characteristics of the solid-state imaging device.

  Therefore, the technique of Patent Document 2 has been proposed in order to make the color filter pattern finer and thinner. Patent Document 2 describes that a color filter pattern is formed by dry etching that can be patterned without containing a photosensitive component so that the pigment concentration in the color filter material can be improved. By using these dry etching techniques, the pigment concentration can be improved, and a color filter pattern capable of obtaining sufficient spectral characteristics even when the film thickness is reduced can be produced.

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

However, the inventors of the present invention have studied the method for producing the color filter pattern described in Patent Document 2, and when using green as the first color filter, other solvents are used in the etching mask cleaning process after dry etching. It has been found that needle-like crystals are generated when a needle-like crystal is generated by reacting with, or when blue and red color filters, which are second and subsequent color filters, are formed in adjacent regions.
The present invention has been made in view of the above points, and suppresses the generation of needle-like crystals at the time of forming each color filter, suppresses color mixing of each color filter material, and achieves high-definition and high-sensitivity solid-state imaging. An object is to provide an element.

  To achieve the above object, a solid-state imaging device according to one embodiment of the present invention includes a semiconductor substrate having a plurality of photoelectric conversion elements arranged two-dimensionally, and the plurality of photoelectric conversions formed on the semiconductor substrate. A color filter layer in which a plurality of color filters corresponding to the element are two-dimensionally arranged in a regular pattern set in advance; a planarization layer formed between the color filters of the plurality of colors and the semiconductor substrate; A partition disposed between the color filters of the plurality of colors, a microlens formed on the color filter layer and disposed two-dimensionally corresponding to each of the color filters of the plurality of colors, and the plurality of colors And a transparent protective layer disposed only between the color filter of the first color selected from the above and the microlens.

  The solid-state imaging device manufacturing method according to one aspect of the present invention is a coating method in which a planarization layer is formed on a semiconductor substrate in which a plurality of photoelectric conversion elements are two-dimensionally arranged, and then applied onto the planarization layer. The liquid is thermally cured to form a first color filter, then a transparent protective layer is formed on top of the first color filter, the transparent protective layer is formed, and then the color of the first color is formed. A first step of removing a part of the filter by dry etching and patterning the color filter of the first color on which the transparent protective layer is formed; and the first color in the first step. A second step of forming partition walls on the outer periphery of the color filter of the first color by a reaction product of the color filter of the first color and a dry etching gas generated when the color filter is dry etched; After the second step A third step of patterning a color filter of another color different from the color filter of the first color on the semiconductor substrate by photolithography, and after the third step, the color filter of the first color and the color filter And a fourth step of forming microlenses on top of the color filters of other colors.

  According to each aspect of the present invention, color mixing can be suppressed by reducing the thickness of each color filter and the partition between color filters, and the process resistance during dry etching and color mixing at the time of forming each color filter can be suppressed by the transparent protective layer. It is possible to provide a high-definition solid-state imaging device in which the generation of needle crystals is reduced and all color filters arranged in a pattern have high sensitivity.

It is a fragmentary sectional view of the solid-state image sensing device concerning a 1st embodiment of the present invention. It is a partial top view of the color filter arrangement | sequence of the solid-state image sensor which concerns on the 1st Embodiment of this invention. It is a manufacturing process sectional drawing of the solid-state image sensor concerning the 1st Embodiment of this invention, Comprising: It is a figure which shows from the planarization layer formation process to a transparent protective layer formation process. It is a manufacturing process sectional view of the solid-state image sensing device concerning a 1st embodiment of the present invention, and is a figure showing from a photosensitive resin material application process to an exposure development process. It is a manufacturing process sectional view of the solid-state image sensing device concerning a 1st embodiment of the present invention, and is a figure showing from a dry etching process to an etching mask removal process. It is a manufacturing process sectional view of the solid-state image sensing device concerning a 1st embodiment of the present invention, and is a figure showing from the 2nd color filter application process to the heat curing of the 2nd color filter. It is a manufacturing process sectional drawing of the solid-state image sensing device concerning a 1st embodiment of the present invention, and is a figure showing from the 3rd color filter application process to the heat hardening process of the 3rd color filter. FIG. 6 is a cross-sectional view of the manufacturing process of the solid-state imaging device according to the first embodiment of the present invention, and is a diagram illustrating a microlens formation process (part 1); FIG. 6 is a cross-sectional view of the manufacturing process of the solid-state imaging device according to the first embodiment of the present invention, and is a diagram illustrating a microlens formation process (part 2); FIG. 6 is a cross-sectional view of the manufacturing process of the solid-state imaging device according to the first embodiment of the present invention, and is a diagram illustrating a process of forming the microlens using a heat flow (No. 1). FIG. 6 is a cross-sectional view of the manufacturing process of the solid-state imaging device according to the first embodiment of the present invention, and is a diagram illustrating a process of forming the microlens using a heat flow (No. 2). FIG. 6 is a cross-sectional view of the manufacturing process of the solid-state imaging device according to the first embodiment of the present invention, and is a diagram illustrating a process of forming a microlens using a gray-tone mask (part 1). FIG. 6 is a cross-sectional view of the manufacturing process of the solid-state imaging device according to the first embodiment of the present invention, and is a diagram illustrating a process of forming a microlens using a gray-tone mask (part 2). It is a fragmentary sectional view of the solid-state image sensing device concerning a 2nd embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Here, the drawings are schematic, and the relationship between the thickness of each layer such as a color filter and a planar dimension, the ratio of the thickness of each layer, and the like are different from the actual ones. In addition, each embodiment shown below exemplifies a configuration for embodying the technical idea of the present invention, and the technical idea of the present invention is that the material, shape, structure, etc. of the components are as follows. It is not specified in the thing. The technical idea of the present invention can be variously modified within the technical scope defined by the claims described in the claims.

<First Embodiment>
(Configuration of solid-state image sensor)
A first embodiment of the present invention will be described with reference to FIGS.
As shown in FIG. 1, the solid-state imaging device 1 according to this embodiment includes a semiconductor substrate 10 having a plurality of photoelectric conversion elements 11 arranged two-dimensionally and a plurality of micro-devices arranged above the semiconductor substrate 10. The lens 18 includes a color filter layer 100 and a partition wall 30 provided between the semiconductor substrate 10 and the microlens 18. The color filter layer 100 is composed of a plurality of color filters. Specifically, the color filter layer 100 includes a first color filter 14, a second color filter 15, and a third color filter 16 arranged in a predetermined regular pattern. The partition wall 30 is formed between each of the first color filter 14, the second color filter 15, and the third color filter 16. In the solid-state imaging device 1, the transparent protective layer 13 is formed only on the upper surface of the first color filter 14 among the color filters of a plurality of colors constituting the color filter layer.

  FIG. 1 illustrates a solid-state imaging device 1 having a configuration in which the planarizing layer 12 exists only below the first color filter 14. Further, the planarization layer 12 may be formed below the second color filter 15 and the third color filter 16. In FIG. 1, the color filter layer 100 and the microlens group 180 including the plurality of microlenses 18 are continuously formed. However, the present invention is not limited to this, and the color filter layer 100, the microlens group 180, and the like. A planarizing layer 12 may be formed between the two. Further, the microlens 18 shown in FIG. 1 is formed by an etch-back method, which will be described later, so that the color filter layer 100 and the microlens group 180 are continuous.

  Hereinafter, in the description of the solid-state imaging device 1 according to the present embodiment, the color filter that is formed first in the manufacturing process and has the largest occupied area in the color filter layer 100 is defined as the first color filter 14. The color filter formed second in the manufacturing process is defined as the second color filter 15, and the color filter formed third in the manufacturing process is defined as the third color filter 16. The same applies to other embodiments. In the present embodiment, the color filter layer 100 is composed of three color filters of green, blue, and red as a plurality of colors and is arranged in a Bayer array arrangement pattern. You may comprise four or more color filters. In the following description, the case where the first color filter 14 is green is described. However, the first color filter 14 may be blue or red. Further, the first color filter 14 includes a thermosetting resin. Here, the first color filter 14 may not be a color filter having the widest area, and may not be a color filter formed first in the manufacturing process.

Hereinafter, each component of the solid-state imaging device 1 will be described in detail.
(Photoelectric conversion element and semiconductor substrate)
As shown in FIG. 1, a plurality of photoelectric conversion elements 11 are two-dimensionally arranged on the semiconductor substrate 10 in the solid-state imaging device 1 according to the present embodiment corresponding to the pixel positions. The plurality of photoelectric conversion elements 11 have a function of converting light into an electrical 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 flattening the surface (light incident surface). The semiconductor substrate 10 is formed of a material that transmits visible light and can withstand a temperature of at least about 300 ° C. Here, as a material used for the semiconductor substrate 10, for example, Si, oxides such as SiO ₂ and nitride such as SiN, and materials containing Si, such as mixtures thereof.

(Micro lens)
Each microlens 18 in the solid-state imaging device 1 is disposed above the semiconductor substrate 10 at a position corresponding to the pixel position. That is, the microlens 18 is provided at a position corresponding to each of the plurality of photoelectric conversion elements 11. The microlens 18 can compensate for a decrease in sensitivity of the photoelectric conversion element 11 by condensing incident light incident on the microlens 18 on each of the photoelectric conversion elements 11. The microlens 18 preferably has a height from the lens top to the lens bottom in the range of 300 nm to 800 nm.

The microlens 18 is, for example, one of acrylic resin, epoxy resin, polyimide resin, phenol novolac resin, polyester resin, urethane resin, melamine resin, urea resin, styrene resin, silicon resin, and the like. Or it forms with the resin material containing plural. The microlens 18 is formed by processing the resin material into a microlens shape by an etch back method described later. The microlens 18 may be formed of other than an organic compound. Specifically, the microlens 18 includes, for example, at least one of silicon, carbon, oxygen, hydrogen, tin, zinc, indium, aluminum, gallium, titanium, molybdenum, tungsten, niobium, tantalum, hafnium, silver, and fluorine. You may form with the compound, oxide, or nitride to contain. As compounds of these materials, for example, ITO, ZnO, TiO ₂ and HfO ₂ can be used.

  The microlens 18 preferably does not affect the spectral characteristics of the first color filter 14, the second color filter 15, and the third color filter 16. For this reason, for example, the microlens 18 is preferably formed so as to have a transmittance of 90% or more, more preferably a transmittance of 95% or more with respect to visible light having a wavelength of 400 nm to 700 nm. Accordingly, the microlens 18 is not limited to the oxides and compounds described above, and transmits visible light having a wavelength of 400 nm to 700 nm, and the first color filter 14, the second color filter 15, and the third color filter 16. As long as the material does not hinder the pattern formation or adhesion, it may be formed using either an organic compound or an inorganic compound. The microlens 18 is not limited to the oxides and compounds described above, and may be configured to transmit visible light having a wavelength of 380 nm to 780 nm.

(Flattening layer)
The planarization layer 12 in the solid-state imaging device 1 is a layer provided on the outermost surface of the semiconductor substrate 10 for surface protection and planarization of the semiconductor substrate 10. The planarization layer 12 reduces unevenness on the upper surface of the semiconductor substrate 10 caused by the fabrication of the photoelectric conversion element 11, and forms the first color filter 14, the second color filter 15, and the third color filter 16. The adhesion of the color filter material to the semiconductor substrate 10 can be improved.

The planarizing layer 12 is made of, for example, an acrylic resin, an epoxy resin, a polyimide resin, a phenol novolac resin, a polyester resin, a urethane resin, a melamine resin, a urea resin, a styrene resin, and a silicon resin. It is formed of a resin containing one or more. Further, the planarizing layer 12 is made of at least one of silicon, carbon, oxygen, hydrogen, tin, zinc, indium, aluminum, gallium, titanium, molybdenum, tungsten, niobium, tantalum, hafnium, silver, and fluorine other than organic compounds. You may form with the compound containing a kind, an oxidation compound, or a nitride compound. As compounds of these materials, for example, ITO, ZnO, TiO ₂ , HfO ₂ or the like can be used. Further, the planarization layer 12 may be formed of a single material of these materials. Thus, the planarization layer 12 may be formed of a compound containing at least one of these materials, or may be formed of a single material of these materials. Further, the planarizing layer 12 is formed of a single layer or a multilayer using these materials.

The planarizing layer 12 is not limited to the oxides and compounds described above, and transmits visible light having a wavelength of 400 nm to 700 nm, and the first color filter 14, the second color filter 15, and the third color filter. 16 pattern formation and the material which does not inhibit adhesion may be used. Further, the planarizing layer 12 may be configured to transmit visible light having a wavelength of 380 nm to 780 nm. For example, the planarizing layer 12 is formed by applying an oxide film such as SiO ₂ , a nitride film such as SiN, and a mixture thereof and heating and curing, or various film forming methods such as vapor deposition, sputtering, and CVD. You may form by.
In the solid-state imaging device 1 according to the present embodiment, the planarization layer 12 also functions as a supply source of the partition wall forming material used for forming the partition wall 30 depending on the material constituting the planarization layer 12. As will be described in detail later, the planarizing layer 12 supplies a partition wall forming material for forming a reaction product that becomes a partition wall 30 by reacting with a dry etching gas during dry etching of a first color filter described later. can do.

  The thickness of the planarizing layer 12 is, for example, more than 0 nm and 200 nm or less. From the viewpoint of preventing color mixing between the color filters of the plurality of colors constituting the color filter layer 100, the thickness of the planarizing layer 12 is preferably as thin as possible. FIG. 1 shows an example in which an organic resin is used for the planarizing layer 12. Further, as will be described in detail later, in the manufacturing process of the solid-state imaging device 1 according to the present embodiment, the first color filter 14 is subjected to shape processing using a dry etching method. At this time, the planarization layer 12 formed other than the lower portion of the first color filter 14 is etched without residue. Therefore, as shown in FIG. 1, the planarizing layer 12 is not formed below the second color filter 15 and the third color filter 16.

(Color filter layer)
Each color filter (first color filter 14, second color filter 15, and third color filter 16) constituting the color filter layer 100 by a predetermined pattern is used for each color (green, blue, and red) that separates incident light. ). As shown in FIG. 1, the first color filter 14, the second color filter 15, and the third color filter 16 are provided between the semiconductor substrate 10 and the microlens 18, and the plurality of photoelectric conversion elements 11. In order to correspond to each, they are arranged in a regular pattern set in advance according to the pixel position.

In FIG. 2, the first color filter 14, the second color filter 15, the third color filter 16, and the arrangement of the partition walls 30 formed between the color filters constituting the color filter layer 100 are planarly illustrated. FIG. The arrangement shown in FIG. 2 is a so-called Bayer arrangement, and the first color filter 14, the second color filter 15, and the third color filter 16 (first, second, and second) having a rectangular shape with rounded corners. 3 is an array in which three examples of color filters are spread. The color filter of the solid-state imaging device 1 is not necessarily limited to the Bayer arrangement, and the color filter color is not limited to 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.
Each color filter constituting the color filter layer 100 includes a predetermined color pigment (colorant) and a thermosetting component or a photocuring component. For example, the first color filter 14 includes a green pigment as a colorant, the second color filter 15 includes a blue pigment, and the third color filter 16 includes a red pigment.

In the solid-state imaging device 1 according to the present embodiment, the first color filter 14 includes a thermosetting resin. When the first color filter 14 includes a thermosetting resin, for example, the curing component in the solid content is 5% by mass or more and 40% by mass or less, and preferably the thermosetting resin is 5% by mass or more and 15% by mass or less. Range. Moreover, if the hardening component in solid content is the above-mentioned range, in the 1st color filter 14, you may mix and use a thermosetting resin and photocurable resin.
Further, in order to reduce the thickness of the color filter layer 100 in the solid-state imaging device 1, the concentration of the pigment (colorant) contained in the first color filter 14, the second color filter 15 and the third color filter 16 is 50. It is preferable that it is mass% or more.

(Transparent protective layer)
The transparent protective layer 13 protects the surface of the first color filter 14, flattenes, and reduces damage when processing the shape by a dry etching method (reducing plasma damage due to charging (charge-up) or the like, or reducing damage in the cleaning process). It is a layer provided for. The transparent protective layer 13 is also a layer provided as a protective layer for reducing the influence of color mixing when forming the second color filter 15 and the third color filter 16. That is, the transparent protective layer 13 damages each color filter material when the first color filter 14 is formed by a dry etching method and when the second color filter 15 and the third color filter 16 are formed. It becomes a protective layer for reducing. This transparent protective layer 13 improves the degree of freedom of the material used for the first color filter 14.

The transparent protective layer 13 is, for example, an acrylic resin, an epoxy resin, a polyimide resin, a phenol novolac resin, a polyester resin, a urethane resin, a melamine resin, a urea resin, a styrene resin, or a silicon resin. It is formed of a resin containing one or more.
Further, the transparent protective layer 13 is made of at least one of silicon, carbon, oxygen, hydrogen, tin, zinc, indium, aluminum, gallium, titanium, molybdenum, tungsten, niobium, tantalum, hafnium, silver, and fluorine other than organic compounds. You may form with the compound, oxide, or nitride containing a kind. The compounds of these materials can be used, for example ITO, ZnO, TiO ₂ and HfO ₂ or the like. Moreover, the transparent protective layer 13 may be formed of these materials alone. Thus, the transparent protective layer 13 may be formed of a compound containing at least one of these materials, or may be formed of these materials alone. Further, the transparent protective layer 13 is formed of a single layer or a multilayer by using these materials.

  The transparent protective layer 13 preferably does not affect the spectral characteristics of the first color filter 14, the second color filter 15, and the third color filter 16. For this reason, for example, the transparent protective layer 13 is preferably formed so as to have a transmittance of 90% or more, more preferably a transmittance of 95% or more with respect to visible light having a wavelength of 400 nm or more and 700 nm or less. Therefore, the transparent protective layer 13 is not limited to the oxides and compounds described above, and transmits visible light having a wavelength of 400 nm or more and 700 nm or less, and the first color filter 14, the second color filter 15, and the third color filter. Any organic compound or inorganic compound may be used as long as it is a material that does not hinder the pattern formation and adhesion of 16. The transparent protective layer 13 may be configured to transmit visible light having a wavelength of 380 nm to 780 nm.

  The transparent protective layer 13 preferably has a refractive index equivalent to that of the microlens 18. More preferably, the same material is used for the transparent protective layer 13 and the microlens 18. In this case, since there is no difference in refractive index between the microlens 18 and the transparent protective layer 13, there is an influence when light incident from the microlens 18 passes through the transparent protective layer 13 and enters the first color filter 14. The effect that there is little is acquired. Further, since there is no difference in refractive index between the transparent protective layer 13 and the microlens 18, there is an advantage that the film thickness design of the microlens 18 and the first color filter 14 becomes easy.

  In the solid-state imaging device 1 according to the present embodiment, the material of the transparent protective layer 13 and the material of the microlens 18 may be different. For example, the first color filter 14 and the transparent protective layer 13 are changed by changing the refractive index according to the difference between the material of the transparent protective layer 13 and the material of the microlens 18 in accordance with the desired spectral characteristics of the solid-state imaging device 1. And the reflectance at the interface between the microlens 18 and the transparent protective layer 13 can be reduced. Further, when the first color filter 14 is green and the third color filter 16 is red, the green color (first color filter) is determined based on the difference in refractive index due to the difference in the materials forming the transparent protective layer 13 and the microlens 18. Incident light is easily bent from the first color filter 14) to the red (third color filter 16), and when light enters the red, a color mixture that apparently increases the sensitivity of red may occur. As described above, by changing the refractive index of the transparent protective layer 13 in accordance with the desired sensitivity characteristic of the solid-state imaging device 1 according to the present embodiment, it is also possible to partially control the occurrence of color mixing.

However, if the refractive index difference between the transparent protective layer 13 and the microlens 18 becomes excessive, there is a possibility that reflection at the interface m between the transparent protective layer 13 and the first color filter 14 or the microlens 18 may occur. Therefore, when the refractive index of the transparent protective layer 13 is T and the refractive index of the microlens 18 is n, it is desirable that the range satisfies the condition of n−1 ≦ T ≦ n + 1.
As will be described in detail later, the transparent protective layer 13 is first etched by dry etching in the process of forming the first color filter 14 (pattern formation). One color filter 14 is etched by dry etching. Here, in the present embodiment, the gas used for dry etching when forming the pattern of the first color filter 14 is at least one of fluorine, oxygen, sulfur, carbon, bromine, chlorine, argon, helium, xenon, and krypton. A gas containing one kind is used.

  Further, when the size of the semiconductor substrate 10 is large, film thickness variation and etching process variation occur. Therefore, in the dry etching using the gas as described above, the etching rate (G) of the transparent protective layer 13 is not more than twice the etching rate (T) of the first color filter 14 (2 ≧ G / T). Further, it is preferable that the transparent protective layer 13 and the first color filter 14 are made of materials having the same etching rate. This facilitates the dry etching process. However, the material of the transparent protective layer 13 and the first color filter 14 may be a material that can be dry-etched and may be within a range where an etching mask pattern can be formed by increasing the film thickness of an etching mask described later. The etching rates of the transparent protective layer 13 and the first color filter 14 are not limited to the above-described etching rate range.

  In this embodiment, the film thickness B (nm) of the transparent protective layer 13 is formed in a range exceeding 0 nm and not more than 200 nm. The film thickness B of the transparent protective layer 13 is preferably as thin as possible from the viewpoint of transmittance and color mixing prevention, and more preferably 5 nm to 50 nm. In addition, when the first color filter 14 is processed by a dry etching method, the process design is easier when the film thickness B of the transparent protective layer 13 is thinner. For this reason, as long as the function as a protective layer is obtained, the thickness B of the transparent protective layer 13 is preferably thin, and more preferably 30 nm or less.

(Partition wall)
In the solid-state imaging device 1 according to the present embodiment, the partition wall 30 includes each of a plurality of color filters (the first color filter 14, the second color filter 15, and the third color filter 16) constituting the color filter layer 100. Configured between. In the present embodiment, the first color filter 14, the second color filter 15, and the third color filter 16 are each separated by the partition wall 30 provided on the side wall (outer periphery) of the first color filter 14. Can be separated. The partition wall 30 is a reaction product of the first color filter material included in the first color filter 14 and the material included in the planarization layer 12 and the dry etching gas used when forming the first color filter 14. Contains things.
That is, the material of the partition wall 30 includes the first color filter 14 material and the planarization layer 12 material. Specifically, the material of the partition wall 30 contains, for example, a compound containing at least one of zinc, copper, nickel, silicon, carbon, oxygen, hydrogen, nitrogen, bromine and chlorine. In addition, the organic compound contained in the planarization layer 12 may be contained in a minute amount in the partition wall 30.

(Film thickness of each color filter constituting the color filter layer)
In the present embodiment, 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 An is 400 nm or more and 600 nm or less. More preferably, the film thickness A is 500 nm or less.
Moreover, the film thickness B (nm) of the transparent protective layer 13 is formed in a range exceeding 0 nm, which is the value described above, and not more than 200 nm. Preferably, the film thickness B is 5 nm or more and 50 nm or less. More preferably, the film thickness B is 30 nm or less.

Further, the film thickness D (nm) of the planarizing layer 12 is formed in a range exceeding 0 nm, which is the value described above, and not more than 200 nm. Preferably, the film thickness D is 5 nm or more and 50 nm or less. More preferably, the film thickness D is 30 nm or less.
In the present embodiment, when the film thickness of the color filters other than the first color filter (the second color filter 15 and the third color filter 16) is C (nm), the film thickness C is expressed by the following formula. The film thickness is formed to satisfy (1).
A + B−300 (nm) ≦ C ≦ A + B + 300 (nm) (1)

Here, the film thickness difference between the film thickness C (A + B), which is the sum of the film thickness A of the first color filter 14 and the film thickness B of the transparent protective layer 13, and the film thickness C is 300 nm or less. If even a part of the filter layer 100 has a film thickness difference exceeding 300 nm, the light receiving sensitivity of the solid-state imaging device 1 is affected by the influence of obliquely incident light from another pixel, that is, from one color filter to another color filter. This is because there is a risk of lowering. Further, when a step exceeding 300 nm is formed in the color filter layer 100, when the microlens 18 is formed on the color filter layer 100, it may be difficult to form by a method other than the etch-back method. Therefore, the color filter layer 100 is configured such that the film thickness difference between the color filters is 300 nm or less. The film thickness of the second color filter 15 and the film thickness of the third color filter 16 may be different.
Further, when the width of the partition wall 30 (lateral thickness) formed between the color filters of the plurality of colors constituting the color filter layer 100 is larger than 200 nm, the light incident on the photoelectric conversion element 11 by the partition wall 30 is greatly increased. The light receiving sensitivity may be reduced. Therefore, the partition wall 30 is formed with a width of 200 nm or less.

<Method for Manufacturing Solid-State Imaging Device>
Next, the manufacturing method of the solid-state imaging device according to the present embodiment will be described using FIGS. 3 to 8 with reference to FIGS.
(Step of forming a planarization layer)
As shown in FIG. 3A, a semiconductor substrate 10 having a plurality of photoelectric conversion elements 11 is prepared, and a planarization layer 12 is formed on the entire surface of the color filter layer formation position on the surface. The planarizing layer 12 is, for example, the above-described acrylic resin, epoxy resin, polyimide resin, phenol novolac resin, polyester resin, urethane resin, melamine resin, urea resin, styrene resin, silicon resin, and the like. It is formed by applying and curing a resin containing one or more of these resins. In the present embodiment, by using an organic resin for the planarizing layer 12, the planarizing layer 12 is provided below the color filters (second color filter 15 and third color filter 16) other than the first color filter. It has almost no structure.
Here, the manufacturing method of the solid-state imaging device 1 according to the present embodiment is different from a conventional manufacturing method, for example, a manufacturing method in which each color filter constituting the color filter is directly patterned by photolithography using a photosensitive color filter material. .

  That is, in the method for manufacturing the solid-state imaging device 1 according to this embodiment, the first color filter material is applied to the entire surface, and the applied first color filter material is cured to form the first color filter 14. After that, the transparent protective layer 13 is formed on the first color filter (see FIG. 3-1 (d)). Further, the first color filter 14 and the transparent protective layer 13 are removed by dry etching from the first color filter 14 and the transparent protective layer 13 where the other color filters are to be formed (FIG. 3). 3 (h) to (j)). Thereby, the pattern of the 1st color filter 14 by which the upper part was covered by the transparent protective layer 13 is formed (refer FIG.3-3 (i)). When the first color filter 14 and a part of the planarization layer 12 are dry-etched, the reaction product of the first color filter 14 and the planarization layer 12 and the dry etching gas becomes the first color filter. 14 partition walls 30 are formed on the 14 side walls (ie, the outer periphery). Then, as shown in FIG. 2, color filters other than the first color filter (second color filter 15 and third color filter 16) are provided in the portion surrounded by the first color filter 14 and the partition wall 30. Form a pattern. At this time, in this embodiment, the pattern of the first color filter 14 and the partition 30 formed previously is used as a guide pattern, and the second color filter 15 material and the third color filter 16 are subjected to high-temperature heat treatment. Curing material. For this reason, the adhesiveness between the semiconductor substrate 10 and the second color filter 15 and the third color filter 16 can be improved.

Hereinafter, the formation process of each of the color filters of the plurality of colors of the color filter layer 100 in the present embodiment will be described.
(First color filter forming step)
First, with respect to the step of forming the first color filter 14 on the surface of the planarization layer 12 formed on the semiconductor substrate 10 (an example of the first step), FIGS. j). The first color filter 14 is preferably a color filter with the widest occupied area in the solid-state imaging device.

On the surface (see FIG. 3A) of the planarization layer 12 formed on the semiconductor substrate 10 on which the plurality of photoelectric conversion elements 11 are two-dimensionally arranged, a first pigment (mainly composed of a resin material) A first color filter material made of a first resin dispersion in which a colorant is dispersed is applied (see FIG. 3B) to form a first color filter 14. The solid-state imaging device 1 according to the present embodiment is assumed to use a Bayer color filter as shown in FIG. For this reason, the coloring of the first color filter 14 is preferably green (G).
As a resin material of the first color filter material, a thermosetting resin such as an epoxy resin is used. By using a large amount of thermosetting resin as a resin material, unlike the conventional method using a photocurable resin, the pigment content of the first color filter 14 can be increased, and the film thickness is thin and the solid-state imaging device is used. It becomes easy to form the first color filter 14 that can obtain one desired spectral characteristic. However, a mixed resin using a thermosetting resin and a photocurable resin may be used as the first color filter material as long as the film is cured with a film thickness capable of obtaining the desired spectral characteristics of the solid-state imaging device 1. Good.

  In the present embodiment, as shown in FIG. 1, the upper part of the first color filter 14 is covered with a transparent protective layer 13. For this reason, the first color filter 14 is less affected by solvent resistance and color mixing when the second color filter 15 and the third color filter 16 are formed. Therefore, the first color filter 14 can reduce the content of the thermosetting resin, increase the pigment content, and obtain desired spectral characteristics even when the film thickness is thin. For this reason, as long as the 1st color filter 14 can fully be hardened, you may reduce content of curable resin as much as possible.

  When the first color filter 14 is formed, the first color filter 14 is then thermally cured at 150 ° C. or higher and 300 ° C. or lower (see FIG. 3C). More specifically, the first color filter 14 is preferably heated and cured at a temperature of 170 ° C. or higher and 270 ° C. or lower. In manufacturing the solid-state imaging device 1 according to the present embodiment, a high-temperature heating process of 100 ° C. or more and 300 ° C. or less is often used when the microlens 18 described later is formed. For this reason, it is desirable that the first color filter material has high temperature resistance, and more specifically, as described above, it is more preferable to use a thermosetting resin having high temperature resistance as the resin material.

Next, the transparent protective layer 13 is formed on the first color filter layer 14a formed in the previous step (see FIGS. 3-1 (b) and 3-1 (c)) (FIG. 3-1 (d)). reference).
The material of the transparent protective layer 13 is an organic compound or an inorganic compound as described above. The material is prepared by a chemical production method such as a spray method, a coating method or a CVD method, a vacuum deposition method, an ion plating method, or a sputtering method. And a physical manufacturing method such as a method. Here, the chemical production method is a method of producing the transparent protective layer 13 by hydrolysis of chloride or thermal decomposition reaction of an organic compound. Further, the transparent protective layer 13 may be formed by application of a substance containing the above-described material, heat curing, or the like. The transparent protective layer 13 preferably does not affect the spectral characteristics of the first color filter 14, the second color filter 15, and the third color filter 16. For example, it is preferably formed so that the transmittance is 90% or more, more preferably 95% or more, with respect to visible light having a wavelength of 400 nm to 700 nm, or 380 nm to 780 nm.

As described above, the film thickness of the transparent protective layer 13 exceeds 0 nm and is formed in a range of 200 nm or less. The film thickness B of the transparent protective layer 13 is preferably as thin as possible from the viewpoint of transmittance and color mixing prevention, and more preferably from 5 nm to 50 nm. In addition, when the first color filter 14 is processed by the dry etching method, the thinner the film, the easier the process design is. Therefore, the thinner is preferable if the function of the protective layer can be obtained, and more preferably 30 nm or less. .
Next, as shown in FIGS. 3-2 (e) to 3-2 (g), the first color formed in the previous step (see FIGS. 3-1 (b) to 3-1 (d)). An etching mask pattern having an opening is formed on the filter 14 and the transparent protective layer 13.
In forming an etching mask pattern, first, a photosensitive resin material is applied to the surface of the first color filter 14 and dried to form an etching mask 20 (see FIG. 3-2 (e)).

Next, when a region corresponding to a position where the first color filter 14 is not formed is exposed to the etching mask 20 (photosensitive resin layer) using a photomask (not shown), a necessary pattern in the etching mask 20 is obtained. Unnecessary portions 20a corresponding to portions other than those cause a chemical reaction that becomes soluble in the developer (see FIG. 3-2 (f)).
Next, the unnecessary part (exposure part) 20a of the etching mask 20 is removed by development. Thereby, the etching mask 20 having the opening 20b is patterned (see FIG. 3-2 (g)). At the position of the opening 20b, the second color filter 15 or the third color filter 16 is formed in a step after the first color filter forming step.

Here, as the photosensitive resin material for forming the etching mask 20, for example, an acrylic resin, an epoxy resin, a polyimide resin, a phenol novolac resin, and other photosensitive resins may be used singly or in combination or copolymerized. Can be used.
As the photosensitive resin material, it is desirable to use a general photoresist in order to produce a high-resolution and high-precision pattern. By using a photoresist, unlike the case of forming a pattern with a color filter material having photosensitivity, it is possible to form a pattern with easy shape control and good dimensional accuracy.

  The photoresist used here preferably has high dry etching resistance. In the case of using a photoresist as an etching mask material during dry etching, a thermosetting process called post-baking is often used after development in order to improve the selectivity, which is the etching rate with the etching member. However, if a thermosetting process is included, it may be difficult to remove the residual resist used as an etching mask in the removing process after dry etching. For this reason, as a photoresist, what can obtain a selection ratio between etching members, without using a thermosetting process is preferable. Further, when a good selection ratio cannot be obtained, it is necessary to form a photoresist film with a large film thickness. However, when the film thickness is increased, it becomes difficult to form a fine pattern. Therefore, a material having high dry etching resistance is preferable as the photoresist.

Specifically, the etching rate ratio (selection ratio) between the photosensitive resin material that is an etching mask and the first color filter material that is the target of dry etching is preferably 0.5 or more, more preferably 0.8 or more. preferable. With this selection ratio, it is possible to etch the first color filter 14 without erasing all of the etching mask 20. When the film thickness of the first color filter material is about 0.2 μm or more and 0.7 μm or less, the film thickness of the photosensitive resin layer is desirably about 0.5 μm or more and 2.0 μm or less.
In addition, as the photoresist used here, there is no problem with either a positive resist or a negative resist. However, considering the removal of the photoresist after etching, a positive resist is more prone to a chemical reaction in the direction of chemical reaction that progresses and dissolves than a negative resist that changes in a direction of curing due to an external factor. Is preferable.

Examples of the exposure machine used in the photolithography process for patterning the photosensitive resin layer include a scanner, a stepper, an aligner, and a mirror projection aligner. Further, the unnecessary portion 20a of the etching mask 20 may be exposed by direct drawing with an electron beam, drawing with a laser, or the like. In particular, in order to form the first color filter 14 of the solid-state imaging device 1 that needs to be miniaturized, a stepper or a scanner is generally used.
As described above, the etching mask 20 is patterned.

Next, the transparent protective layer 13 exposed from the opening 20b and a part of the first color filter 14 below the opening 20b are removed by dry etching using the patterned etching mask 20 and dry etching gas (FIG. 3-3). (See (h)).
Examples of the dry etching method include ECR, parallel plate magnetron, DRM, ICP, or dual frequency type RIE (Reactive Ion Etching). The etching method is not particularly limited, but it is controlled so that the etching rate and the etching shape do not change even if the line width and area are different, such as a large area pattern with a width of several millimeters or more, or a minute pattern with a width of several hundred nm. An etching method that can be used is desirable. Further, it is desirable to use a dry etching method of a control mechanism that can uniformly dry-etch the entire surface of the wafer having a size of about 100 mm to 450 mm.

Also, the dry etching gas used in the dry etching shown in FIG. 3-3 (h) may be a gas having reactivity (oxidation / reducing properties), that is, an etching gas. Examples of the gas having reactivity include a gas containing fluorine, oxygen, bromine, sulfur and chlorine. Also, a rare gas containing an element that is less reactive, such as argon or helium, and that performs etching by physical impact with ions can be used alone or in combination. For this reason, the gas used for dry etching is a gas containing at least one of fluorine, oxygen, hydrogen, sulfur, carbon, bromine, chlorine, nitrogen, argon, helium, xenon, and krypton. Examples of the gas containing fluorine include CF ₄ , C ₂ F ₆ , C ₃ F ₈ , C ₃ F ₆ , C ₄ F ₁₀ , CHF ₃ , CClF ₃ , CCl ₃ F, NF ₃ , SF ₆ and HF. A gas obtained by mixing a plurality of these fluorine-based gases may be used as the dry etching gas.

In addition, the dry etching gas is not limited to the above-described dry etching gas as long as it causes a reaction for forming a desired pattern in a dry etching process using a gas. In this embodiment, at the initial stage of dry etching, 90% or more of the total gas flow rate is a gas that is mainly etched by a physical impact of ions such as a rare gas, and under such circumstances, a fluorine-based gas or an oxygen-based gas is used. By using a dry etching gas mixed with a gas, an etching rate is improved by utilizing a chemical reaction in addition to a physical impact.
By using a large amount of rare gas as the dry etching gas, anisotropic etching in which etching proceeds vertically is likely to proceed due to the effect of physical impact of rare gas ions. Therefore, in the initial stage of dry etching of the first color filter 14, the etching is performed under a condition where there are many rare gases.

  Further, the semiconductor substrate 10 of the solid-state imaging device 1 according to the present embodiment is made of a material mainly composed of silicon. For this reason, if dry etching is performed using a highly reactive gas such as a fluorine-containing gas, the semiconductor substrate 10 may be etched. For this reason, it is preferable to use a gas that does not etch the semiconductor substrate 10 when performing dry etching. In addition, when a gas that may etch the semiconductor substrate 10 is used, multistage etching may be performed in which the gas is first used and the semiconductor substrate 10 is changed to a gas that is difficult to etch during the etching. The semiconductor substrate 10 is not affected, and the first color filter material can be etched in a nearly vertical shape using the patterned etching mask 20, and a residue of the first color filter material is formed. If the condition of not being performed is satisfied, the type of dry etching gas is not limited.

When the resin that is the above-described organic compound is used for the planarizing layer 12, the etching rate of the planarizing layer 12 is generally faster than that of the first color filter 14. For this reason, when a dry etching gas that may etch the semiconductor substrate 10 is used, the dry etching gas is switched when the first color filter 14 remains (the semiconductor substrate 10 is changed to a gas that is difficult to etch). )There is a need.
Specifically, first, the transparent protective layer 13 and the first color filter 14 exposed in the opening 20b in a state where the rare gas alone or the mixed gas of the reactive gas and the rare gas is 90% or more of the total gas flow rate. Etch a part of. At this time, in order to reduce damage to the semiconductor substrate 10, the etching may be stopped halfway, and the etching may be resumed after reducing the ratio of the rare gas that physically performs the etching. Under such use conditions of the dry etching gas, the etching is stopped when 50% to 95% of the thickness of the first color filter 14 is etched (see FIG. 3-3 (h)).

  In the case of multi-stage etching, in the stage of reducing the ratio of the rare gas, the first color filter 14 exposed to the opening 20b using a gas that is difficult to etch the semiconductor substrate 10, that is, an oxygen-based gas, a nitrogen-based gas, or the like. Are all etched (see FIG. 3-3 (i)). The condition of the dry etching gas used at this time is that the first color filter 14 and the planarizing layer 12 are etched without residue and the semiconductor substrate 10 is not etched. As described above, the first color filter 14 is formed.

(Partition forming step (second step))
Further, as shown in FIG. 3-3 (i), the partition wall 30 is formed by the reaction product generated when the transparent protective layer 13, the first color filter 14, and the planarizing layer 12 are dry-etched. It is formed on the side wall of the color filter 14. The partition wall 30 is configured to separate each of a plurality of color filters (first color filter 14, second color filter 15, and third color filter 16) that finally form the color filter layer 100. The partition wall 30 is formed by a reaction product of the first color filter material and the planarizing layer material and the dry etching gas. Here, when anisotropic etching is performed during the dry etching of the first color filter 14, the side wall protection formed by the reaction product from the dry etching adhering to the side wall of the first color filter 14. Layer control is important. Further, the manner and amount of deposition of the reaction product on the side wall (outer periphery) of the first color filter 14 varies depending on the dry etching conditions.

  In the method for manufacturing the solid-state imaging device 1 of the present embodiment, the first color filter 14 is etched, and the opening 10b formed by this etching is filled with the second color filter and the third color filter material. Thus, the multi-color filter layer 100 is formed. Therefore, when the first color filter 14 is dry-etched, it is necessary to etch the first color filter 14 perpendicular to the surface of the semiconductor substrate 10 and to control the pattern size. For this reason, it is necessary to control how the reaction product adheres to the side wall and the amount of adhesion during dry etching.

As a control of the adhesion of the reaction product to the sidewall, the reaction product deposition amount (attachment amount) on the sidewall of the first color filter 14 is increased by a reaction using physical impact by ions in dry etching. Is possible. For example, the dry etching gas used may be a rare gas such as helium (He), neon (Ne), argon (Ar), krypton (Kr), or xenon (Xe), and Ar or He is particularly desirable.
In this embodiment, a rare gas containing an element with low reactivity such as Ar and He is set to 90% or more of the total gas flow rate, and one or more kinds of reactive gas species such as fluorine or oxygen are mixed. A dry etching gas is used. Thereby, in addition to a physical impact, an etching rate can be improved using a chemical reaction, and the amount of reaction products adhering to the side wall of the first color filter 14 can be controlled. In this way, the reaction product attached to the side wall of the first color filter 14 is formed as the partition wall 30.

  By the dry etching step (see FIGS. 3H to 3I), the residue of the first color filter material is not generated in the region other than the formation target position of the first color filter on the semiconductor substrate 10. The first color filter 14 has a partition wall 30 formed of a reaction product during dry etching, and the upper part is covered with the transparent protective layer 13, that is, the upper and side surfaces are all covered. obtain. By forming the partition wall 30 on the side wall of the first color filter 14, leakage light and migration from other color filters are suppressed, and the transparent protective layer 13 has a resist stripping process such as cleaning and other color colors. This is an effect of suppressing needle crystals due to color mixing with the filter.

(Etching mask removal process)
Next, the pattern of the remaining etching mask 20 is removed (see FIG. 3-3 (j)). For example, a chemical solution or a solvent is used to remove the etching mask 20. By using a chemical solution or a solvent, the etching mask 20 can be dissolved and peeled without affecting the first color filter 14. Examples of the solvent for removing the etching mask 20 include 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. Organic solvents such as propylene glycol monomethyl ether acetate, monoethanolamine and diethanolamine are used alone or as a mixed solvent in which a plurality of organic solvents are mixed. The solvent used for removing the etching mask 20 is preferably one that does not affect the color filter materials. If the color filter material is not affected, there is no problem even with a peeling method using an acid chemical.

For removing the etching mask 20, a removal method other than a wet process using a solvent or the like can also be used. For example, the etching mask 20 can be removed by an ashing technique that is a resist ashing technique using photoexcitation or oxygen plasma. Also, a wet process and ashing can be used in combination. For example, first, after removing the altered layer by dry etching generated on the surface of the etching mask 20 using ashing that is an ashing technique using photoexcitation or oxygen plasma, the remaining portion of the etching mask 20 is removed by wet etching using a solvent or the like. The method of removing these layers is mentioned. Further, the etching mask 20 may be removed only by ashing as long as the first color filter material is not damaged. Further, the etching mask 20 may be removed by using not only a dry process such as ashing or a wet process but also a polishing process by CMP.
Through the above steps, the patterning formation of the transparent protective layer 13 and the partition wall 30 formed on the first color filter 14 is completed.

(Formation process of second color filter and third color filter)
Next, referring to FIG. 1 to FIG. 3-3 for the pattern forming process (third process) of the second color filter 15 and the third color filter 16 including colors different from the first color filter 14. However, this will be described with reference to FIGS. In the third step, the pattern of the first color filter 14 and the partition wall 30 is used as a guide pattern, and the second color filter 15 and the third color filter 16 are photosensitive color filters containing a photocurable resin. In this method, a pattern is formed by using a conventional material and selectively exposing with a conventional method.

(Second color filter forming step)
First, as a second color filter material on the entire surface of the semiconductor substrate 10 on which the first color filter 14 and the transparent protective layer 13 and the partition wall 30 on the first color filter 14 are formed (see FIG. 3-3 (j)). A photosensitive color filter material is applied and dried to form the second color filter 15 (see FIG. 4A). The photosensitive color filter material used at this time contains a negative photosensitive component that is cured by light irradiation.

Next, among the second color filters 15 formed on the semiconductor substrate 10, a photomask (not shown) is applied to the second color filter 15 in the region (pattern region) where the second color filter 15 is formed. Is used for exposure (see FIG. 4B). As a result, the second color filter 15 in the pattern region is selectively photocured to form the second color filter 15. Further, the portion that is not selectively exposed (not photocured) in the developing process, that is, the second color filter 15 outside the pattern region is removed (see FIG. 4C). Here, the third color filter 16 is formed in the region where the second color filter 15 is removed.
Next, in order to improve the adhesion between the second color filter 15 and the semiconductor substrate 10 in the exposed / developed pattern region, and to improve the heat resistance when using an actual device, a curing process at high temperature heating is performed. Then, the second color filter 15 is cured. Thereby, the pattern formation of the second color filter 15 is completed. At this time, the temperature used for thermosetting the second color filter 15 is preferably 200 ° C. or higher.

Here, the film thickness of the second color filter 15 formed in the third step will be described.
The film thickness of the first color filter 14 is A (nm), the film thickness of the transparent protective layer 13 is B (nm), the film thickness of the second color filter 15 is C1 (nm), and the film thickness of the planarizing layer 12 Is set to D (nm), the film thickness C1 of the second color filter 15 is set so as to satisfy the following expressions (1) to (4a).
200 nm ≦ A ≦ 700 nm (1)
0 nm <B ≦ 200 nm (2)
0 nm <D ≦ 200 nm (3)
A + B−300 (nm) ≦ C1 ≦ A + B + 300 (nm) (4a)
The second color filter forming process shown in FIGS. 4A to 4C exemplifies the case of forming the second color filter having the film thickness C1 that satisfies the condition of A + B + D = C1. As shown in the equation (4a), the film thickness C1 only needs to be within the range of (A + B) ± 300 (nm).

If the film thickness C1 is in the range of the above-described formula (4a), the second color filter having a pigment concentration capable of obtaining desired spectral characteristics while containing a thermosetting resin and a photocurable resin sufficient for curing is used. The color filter 15 can be formed.
Here, when the upper part of the first color filter 14 is not covered with the transparent protective layer 13, when the second color filter 15 is cured, the first color filter 14, the second color filter 15, There was a possibility that the needles mixed and colored needles were generated. On the other hand, as shown in the present embodiment, the upper part of the first color filter is covered with the transparent protective layer 13, so that the color mixture of the first color filter 14 and the second color filter 15 or the needle-like crystal is achieved. Can be prevented. Thereby, in this embodiment, it is possible to form a color filter without considering the color mixture of the first color filter material and the second color filter material and the occurrence of needle crystals.

(Third color filter forming step)
When the pattern formation of the second color filter 15 is completed, the third color filter material is then applied on the semiconductor substrate 10 and dried (see FIG. 5A). More specifically, the entire surface of the semiconductor substrate 10 on which the first color filter 14 and the transparent protective layer 13, the partition wall 30, and the second color filter 15 are patterned (see FIG. 4C). A third color filter 16 is formed by applying a third color filter material.
Next, among the third color filters 16 formed on the semiconductor substrate 10, the third color filter 16 in the pattern area where the third color filter 16 is formed is selected using a photomask (not shown). The third color filter 16 is formed by selectively photocuring the exposed third color filter 16 (see FIG. 5B). Further, the third color filter 16 outside the pattern area that has not been exposed by development (not photocured) is removed (see FIG. 4C).

Next, in order to improve the adhesion between the part of the third color filter 16 in the exposed and developed pattern region 16 and the semiconductor substrate 10 and the heat resistance when using an actual device, a curing treatment by high-temperature heating is performed. By doing so, the third color filter 16 is cured. Thereby, the pattern formation of the third color filter 16 is completed. At this time, the temperature used for thermosetting the third color filter 16 is preferably 200 ° C. or higher.
Note that it is possible to form a color filter of a desired number of colors by repeating the pattern forming process after the second color filter 15.

Here, the film thickness of the second color filter 15 formed in the third step will be described.
In the present embodiment, when the film thickness of the third color filter 16 is C2 (nm), the film thickness C2 of the third color filter 16 is satisfied so that the following expressions (1) to (4b) are satisfied. Set.
200 (nm) ≦ A ≦ 700 (nm) (1)
0 (nm) <B ≦ 200 (nm) (2)
0 (nm) <D ≦ 200 (nm) (3)
A + B−300 (nm) ≦ C2 ≦ A + B + 300 (nm) (4b)

In the third color filter forming process shown in FIGS. 5A to 5C, the case where the third color filter having the film thickness C2 that satisfies the condition of A + B + D = C2 is formed is illustrated. As shown in the equation (4b), the film thickness C2 only needs to be within the range of (A + B) ± 300 (nm).
If the film thickness C2 is in the range of the above-described formula (4b), a pigment that can obtain desired spectral characteristics of the solid-state imaging device 1 according to the present embodiment while including a thermosetting resin and a photocurable resin sufficient for curing A third color filter 16 can be formed as a color filter having a density.

(When the color filter layer is composed of four or more color filters)
Although the formation process of the three color filters constituting the color filter layer 100 has been described with reference to FIGS. 3A to 5, the color filters constituting the color filter layer 100 are not limited to three colors. For example, the color filter layer 100 may be configured by four or more color filters. When manufacturing a color filter with four or more colors, an opening corresponding to the formation position of the four or more color filters is provided at the time of forming the pattern of the first color filter. As a process, the same process as the formation process of the second color filter 15 described above is repeated. Further, in the process of forming the last color filter constituting the color filter layer 100, the same process as the process of forming the third color filter 16 described above is performed. As a result, the color filter layer 100 can be configured by producing color filters of four or more colors.

(Microlens formation process)
Next, as a final step of the manufacturing process of the solid-state imaging device 1, a step of forming the microlens 18 (fourth step) will be described with reference to FIGS. The microlens 18 is formed by any one of a microlens transfer method using dry etching (etchback method), a manufacturing method using heat flow, a macrolens manufacturing method using a gray tone mask, and the like.
Here, an example in which the microlens 18 of the solid-state imaging device 1 according to the present embodiment is formed by using the patterning technique (microlens transfer method) by dry etching will be described with reference to FIG. In this example, the microlens 18 is formed by using an etch back method in which a dry etching mask is formed on the microlens forming material, and the microlens shape is transferred to the microlens forming material by dry etching.

  First, a microlens transfer layer 19 that finally becomes a microlens 18 is formed on a plurality of color filters (first color filter 14, second color filter 15, third color filter 16) and partition walls 30. (See Fig. 1 (a)). The material of the microlens transfer layer 19 is an acrylic resin, an epoxy resin, a polyimide resin, a phenol novolac resin, a polyester resin, a urethane resin, a melamine resin, urea as in the material of the microlens 18 described above. Resin, resin containing one or more of styrene resin and silicon resin, or silicon, carbon, oxygen, hydrogen, tin, zinc, indium, aluminum, gallium, titanium, molybdenum, tungsten, niobium, tantalum, hafnium Any compound or oxide containing at least one of silver and fluorine may be used.

  The film thickness of the microlens transfer layer 19 is preferably 0.3 μm or more and 10 μm or less. The film thickness of the microlens transfer layer 19 varies depending on the size of the photoelectric conversion element 11 disposed on the semiconductor substrate 10 and the size of each of the color filters of the plurality of colors constituting the color filter layer 100. For example, when the size of the first color filter 14 is 1.0 μm, the thickness of the microlens 18 is preferably about 0.8 μm or less, and the thickness of the microlens transfer layer 19 is preferably about 2 μm or less.

  In addition, when the same material as the material of the transparent protective layer 13 is used as the material of the microlens 18, the microlens 18 is removed without considering the change in optical characteristics such as the refractive index difference at the interface of the transparent protective layer 13. It becomes possible to form. Further, when a material different from that of the transparent protective layer 13 is used as the material of the microlens 18, each color filter (the first color filter 14, the second color filter 15, and the first color filter) constituting the color filter layer 100 due to a difference in refractive index. The incident light on the third color filter 16) is affected. For this reason, the desired condensing characteristics can be obtained by the microlens 18 in consideration of the refractive index of each color filter. However, when the refractive indexes of the transparent protective layer 13 and the microlens 18 are different, the procedure for obtaining a desired light collecting characteristic by the microlens 18 becomes complicated. For this reason, it is preferable that the transparent protective layer 13 is as thin as possible as long as it has a film thickness that can provide solvent resistance and can be formed in the process.

Next, a microlens matrix layer 19a is applied and formed on the microlens transfer layer 19 (see FIG. 6B). The microlens matrix layer 19 a is used to form a matrix of the microlens 18. As the material of the microlens matrix layer 19a, a photosensitive material and a resin material containing one or a plurality of acrylic resins are used. Thereby, the microlens matrix layer 19a can be processed into a desired shape using photolithography while making the microlens matrix layer 19a have photosensitivity.
Next, the microlens matrix layer 19a is exposed using a photomask (not shown), and the microlens matrix layer 19a is formed into a hemispherical lens shape by a heat flow method (see FIG. 6C). ).

  Next, using the microlens matrix layer 19a formed in a lens shape as a mask, the shape of the microlens matrix layer 19a is transferred to the microlens transfer layer 19 by a dry etching technique to form the microlens 18 ( (See FIG. 6-2 (d)). In this way, the appropriate lens shape is transferred to the microlens transfer layer 19 to form the microlens 18 by appropriately selecting the height and material of the microlens matrix layer 19a and adjusting the dry etching conditions. Can do. In the present embodiment, the microlens 18 can be formed with good controllability by using the above-described method. In the production of the microlens 18 using this technique, it is desirable that the height from the lens top to the lens bottom of the microlens 18 is 300 nm or more and 800 nm or less.

Next, an example in which the microlens 18 is formed by a manufacturing method using heat flow will be described with reference to FIGS.
In the case of using a manufacturing method using heat flow, first, a planarizing film 19b is formed so as to cover the upper side of the semiconductor substrate 10 on which each color filter of the color filter layer 100 is formed (see FIG. 7A). The planarizing film 19b formed at this time may be the same material as the material of the planarizing layer 12 formed below the first color filter 14 and the transparent protective layer 13 formed above the first color filter 14. Further, at least the material of the planarizing film 19b may be any material that does not cause a problem in the production of the microlens 18 formed on the upper portion.

Next, a microlens material layer 18a to be the microlens 18 is formed on the planarizing film 19b using a resin material having photosensitivity. The microlens material layer 18a is formed by applying a positive photoresist by spin coating and thermally curing on a hot plate. The film thickness of the microlens material layer 18a formed by thermosetting is, for example, in the range of 0.3 μm to 10.0 μm, and typically in the range of 0.4 μm to 2.0 μm. .
Here, as materials that can be used for forming the microlens material layer 18a in the present embodiment, far ultraviolet rays including ultraviolet rays (g rays, h rays and i rays), excimer lasers, etc., electron beams, ion beams, and X A positive resist resin suitable as a positive photoresist sensitive to radiation such as lines can be used. Examples of the positive resist resin include novolac type phenol resins and polyvinyl phenol resins.

Furthermore, the material that can be used for the microlens material layer 18a contains additives other than the positive resist resin of the upper surgery as necessary to the extent that the characteristics of the solid-state imaging device 1 according to the present embodiment are not impaired. Can be made. Here, as other additives, for example, an adhesion assistant used for improving the adhesion to the semiconductor substrate 10, a surfactant, a leveling agent, a dispersing agent, a curing agent and the like used for improving the coating property can be mentioned. .
Next, exposure and development are performed using the photomask 21 (see FIG. 7B). Further, by performing development processing subsequent to exposure and development, a microlens matrix shape is formed on the color filter layer 100 by the microlens material layer 18a (see FIG. 7-2 (c)).

  Next, the microlens 18 is formed by post-baking the microlens material layer 18a (see FIG. 7-2 (d)). About the temperature at the time of post-baking, it is possible to control the amount of heat flow by performing a baking process in steps. When the baking treatment is performed at a temperature equal to or higher than the glass transition temperature, the microlens material layer 18a is fluidized, and the matrix shape of the microlens 18 formed by the microlens material layer 18a in the development process (see FIG. 7-2 (c)). Can be formed into a spherical shape as shown in FIG.

Depending on the material of the microlens 18, bleaching exposure is performed before post-baking as necessary. The bleaching exposure step is a step of improving light transmittance by irradiating light to the entire microlens material layer 18a formed as a matrix in the development step. Since the microlens material layer 18a, which is a positive photoresist, contains a photosensitive agent (diazonaphthoquinones), it is colored light yellow or light brown. By irradiating the microlens material layer 18a with light, the remaining unreacted photosensitizer (diazonaphthoquinones) is photodegraded and converted into indenecarboxylic acid having no absorption in the visible light region, and thereby the light transmittance. Will improve. Indenecarboxylic acid reacts with (H ₂ O) in the atmosphere and changes to carboxylic acid. Since the carboxylic acid does not bind to the resin, the microlens material layer 18a is not cured as a result. Further, the wavelength of light emitted from the light source used in the bleaching exposure process may be visible light or ultraviolet light, and is not particularly limited, but the light source in the bleaching exposure process is for forming a matrix of the microlens material layer 18a. It is preferable to select the same light source as in the exposure step.

When the microlens 18 is formed by the heat flow method as described above, not all the microlenses 18 constituting the microlens group 180 (see FIG. 1) are formed at a time, but a plurality of microlenses. 18 may be divided into a plurality of times, that is, the same process may be repeated several times to finally form a plurality of microlenses 18. By forming the plurality of microlenses 18 constituting the microlens group 180 by being divided into a plurality of times, the gap between the microlenses 18 can be adjusted.
By performing the steps shown in FIGS. 7A to 7D as described above, the microlens 18 can be formed using the heat flow method.

Next, an example in which the microlens 18 is formed by a method using a gray tone mask will be described with reference to FIG.
In this method, the microlens 18 is formed using a special exposure mask (photomask) called a gray tone mask. The gray tone mask is obtained by forming a light-shielding film with a variable light transmittance on a quartz substrate so as to correspond to a lens element to be manufactured. It can be said that the light-shielding film has a light and shade gradation (gradation). The gradation of gradation in the gray tone mask is achieved by a partial difference in the number (rough density) of small-diameter dots that are not resolved by the light used for exposure per unit area. According to the exposure method using the gray tone mask, it becomes easy to control the shape of a desired microlens. Specifically, since the surface roughness can be suppressed by an exposure method using a gray tone mask, a smooth microlens with little light scattering on the lens surface can be obtained. The microlens shape formed using the gray tone mask includes a spherical shape, a parabolic shape, a Sin shape, a triangular pyramid, and the like, but a parabolic shape is preferable from the viewpoint of light collection efficiency. In the present embodiment, when exposing the microlens material layer using a gray tone mask, an exposure apparatus called a general stepper is used. Ultraviolet light is used for exposure in this exposure apparatus, and the wavelength is preferably 365 nm.

  In the microlens forming method using the gray tone mask, the planarizing film 19b is formed so as to cover the upper part of the semiconductor substrate 10 on which the color filters of the color filter layer 100 are formed, as in the above-described heat flow forming method (FIG. 8-1 (a)). The planarizing film 19b formed at this time may be the same material as the material of the planarizing layer 12 formed below the first color filter 14 and the transparent protective layer 13 formed above the first color filter 14. Further, at least the material of the planarizing film 19b may be a material that does not cause a problem in the formation of the microlens 18 formed on the upper portion.

Next, a microlens material layer 18a to be the microlens 18 is formed on the planarizing film 19b using a photosensitive resin material (see FIG. 8B). The microlens material layer 18a is formed by applying a positive photoresist by spin coating and thermally curing on a hot plate. At this time, the film thickness of the formed microlens material layer is, for example, in the range of 0.3 μm to 10.0 μm, and typically in the range of 0.4 μm to 2.0 μm.
Next, the microlens material layer 18a is exposed using the gray tone mask 22 (see FIG. 8-2 (c)). Furthermore, by performing development processing after exposure, a matrix shape of a microlens is formed on the color filter layer 100. By using the gray tone mask, the microlens material layer 18a is formed in a desired microlens shape at the stage of development processing.

  Next, the microlens material layer 18a is post-baked. Thereby, the micro lens 18 is formed (see FIG. 8D). About the temperature at the time of post-baking, it is possible to control the amount of heat flow by performing a baking process in steps. When the baking process is performed at a temperature equal to or higher than the glass transition temperature, the microlens material layer 18a is fluidized. For this reason, in microlens fabrication using a gray tone mask, the temperature at the time of post-baking is set to a temperature not higher than the glass transition temperature of the microlens material, for example, in the range of 110 to 160 ° C., and further divided into multiple times. Bake in stages. Accordingly, the microlens 18 can be formed by advancing film hardening without fluidizing the microlens material layer 18a. The minimum temperature that can be set in the stepwise baking process is about 5 ° C. based on the tolerance of the production process. In addition, when baking is performed at a temperature equal to or higher than the glass transition temperature, the microlens material layer 18a formed into a desired microlens shape flows after development, and the microlens shape obtained after development can be maintained. Absent.

Depending on the material of the microlens 18, bleaching exposure is performed before post-baking as necessary. The bleaching exposure step is a step of improving light transmittance by irradiating light to the entire microlens material layer 18a formed in the development step as described above.
As described above, microlenses can be formed using a gray-tone mask by performing the steps shown in FIGS. 8-1 (a) to 8-2 (d).
Through the above steps, the solid-state imaging device 1 of the present embodiment is completed.
In the present embodiment, as described above, it is preferable that the first color filter 14 is a color filter with the largest occupation area. The second color filter 15 and the third color filter 16 are formed by photolithography using a color resist having photosensitivity.

  The first color filter material is applied to the entire surface of the planarizing layer 12 and then heated at a high temperature. For this reason, the adhesiveness with the semiconductor substrate 10 and the planarization layer 12 can be improved. As a result, the four sides are surrounded by the partition walls 30 by using the first color filter 14 and the partition wall 30 pattern formed with good rectangularity as a guide pattern with good adhesion to the semiconductor substrate 10 and the planarization layer 12. The second color filter 15 and the third color filter 16 can be formed so as to fill the remaining place (see FIG. 2). Here, the technique used for forming the second color filter 15 and the third color filter 16 is a technique using a color resist having photosensitivity, and is a conventional technique for producing a color filter pattern. However, in the present embodiment, even when the second color filter 15 and the third color filter 16 are formed using a color resist that has photosensitivity, the color resist that emphasizes resolution as in the past is used. There is no need to do. For this reason, it becomes possible to reduce the photocuring component in the photocurable resin in the second color filter 15 and the third color filter 16, and increase the ratio of the pigment in the second and third color filter materials. In addition, the second color filter 15 and the third color filter 16 can be made thinner.

  In the present embodiment, a thermosetting resin is used as the material of the first color filter 14. Furthermore, the first color filter 14 is desirably formed of a color filter material having a high pigment content. In particular, the pigment content in the first color filter material is desirably set to 70% by mass or more. Thus, even when the first color filter material contains a pigment having a concentration that may cause insufficient curing in a photolithography process using a conventional photosensitive color resist, The color filter 14 can be formed with high accuracy and without residue or peeling.

  In this embodiment, a thermosetting resin material is used as the first color filter material in order to improve the curability and solvent resistance of the first color filter 14, but depending on the desired spectral characteristics, the pigment concentration In addition, importance may be placed on the aging characteristics and the like, and only the photocurable resin or a material using a combination of a thermosetting resin and a photocurable resin may be used as the first color filter material. When only the photocurable resin is used as the first color filter material, the solvent resistance tends to decrease, but there is an advantage that the degree of freedom in material design is improved in terms of temporal characteristics and the like.

In the present embodiment, the partition wall 30 is formed between the first color filter 14, the second color filter 15, and the third color filter 16. For this reason, the partition wall 30 can suppress light leakage and migration from the color filters of other colors, thereby suppressing color mixing in the color filter 100.
In the present embodiment, the transparent protective layer 13 is formed on the first color filter 14, so that the etching mask removal process when the first color filter 14 is formed, and the second color filter It is possible to reduce the risk of material color mixing when forming the 15 and third color filters 16, and to suppress the generation of needle crystals.

  As described above, the solid-state imaging device 1 manufactured by the manufacturing method according to the present embodiment is formed on the semiconductor substrate 10 having the plurality of photoelectric conversion elements 11 arranged two-dimensionally, and the plurality of photoelectric conversion elements 11. A color filter layer 100 in which a plurality of color filters corresponding to the photoelectric conversion element 11 are two-dimensionally arranged in a regular pattern set in advance, and a flat surface formed between the plurality of color filters and the semiconductor substrate 10. Microlenses 18 formed on the color filter layer 100, the partition walls 30 disposed between the color filters of the plurality of colors, and the color filter layer 100, and two-dimensionally disposed corresponding to the color filters of the plurality of colors. And a transparent protective layer 13 disposed only between the first color filter 14 selected from a plurality of color filters and the microlens 18.

  In the method for manufacturing the solid-state imaging device 1 according to the present embodiment, the planarization layer 12 is formed on the semiconductor substrate 10 on which the plurality of photoelectric conversion elements 11 are two-dimensionally arranged, and then applied onto the planarization layer 12. The first color filter material (an example of the coating liquid) is cured to form the first color filter 14 (an example of the one color filter), and then the transparent protective layer 13 is formed on the first color filter 14. After forming the transparent protective layer 13, a part of the first color filter on the semiconductor substrate 10 is removed by dry etching, and the first color filter 14 having the transparent protective layer 13 formed thereon is formed. And a reaction product of the first color filter 14 and the dry etching gas generated when the first color filter 14 is dry-etched in the first step. A second step of forming the partition wall 30 on the outer periphery (side wall) of the color filter 14, and a second color filter 15 and a third color filter other than the first color filter 14 after the second step. A third step of patterning the color filter 16 (an example of another color filter) by photolithography, and after the third step, the first color filter 14, the second color filter 15, and the third color filter And a fourth step of forming a microlens on 16.

  According to the method for manufacturing the solid-state imaging device 1 of the present embodiment, all the film thicknesses of the plurality of color filters constituting the color filter layer 100 are all thinned, the total distance from the microlens top to the device is shortened, By having the partition wall 30 between the color filters, the color mixture in the color filter layer 100 can be suppressed. Furthermore, in the present embodiment, when each color filter is formed in the color filter layer 100, desired spectral characteristics can be obtained in each color filter by suppressing the generation of needle crystals based on process damage and color mixing. Thus, by having all the color filters patterned on the semiconductor substrate 10, the solid-state imaging device 1 according to the present embodiment has high sensitivity. This makes it possible to provide a high-definition solid-state image sensor.

Second Embodiment
Next, a second embodiment of the present invention will be described with reference to FIG.
(Configuration of solid-state image sensor)
As shown in FIG. 9, the solid-state imaging device 2 according to the present embodiment includes a semiconductor substrate 10 having a plurality of photoelectric conversion elements 11 arranged two-dimensionally and a plurality of micro-devices arranged above the semiconductor substrate 10. And a lens 18. A color filter layer 100 and a partition wall 30 are provided between the semiconductor substrate 10 and the microlens 18. The color filter layer 100 is configured by patterning a plurality of color filters (a first color filter 14, a second color filter 15, and a third color filter 16) according to a predetermined rule. Further, the partition wall 30 is formed between the color filters of a plurality of colors. Further, the transparent protective layer 13 is formed only on the upper surface of the first color filter 14 among the color filters of a plurality of colors. A planarizing layer 12 is formed under each of the color filters of the plurality of colors. The planarization layer 12 is partially changed in film thickness. Specifically, the thickness of the planarizing layer 12 is changed only in the lower layer of the second color filter 15 and the third color filter 16 by a dry etching process described later.

Hereinafter, the manufacturing method of the solid-state imaging device 2 will be described as different from the manufacturing method of the solid-state imaging device 1 in the first embodiment.
In this embodiment, a semiconductor substrate 10 having a plurality of photoelectric conversion elements 11 is prepared, and a planarization layer 12 is formed on the entire surface of the semiconductor substrate 10, that is, the entire formation position of the color filter layer 100. The planarization layer 12 in this embodiment plays a role of an etching stopper in a dry etching process described later. As in the first embodiment, the planarizing layer 12 is made of a material such as silicon, carbon, oxygen, hydrogen, tin, zinc, indium, aluminum, gallium, titanium, molybdenum, tungsten, niobium, tantalum, hafnium, silver, and fluorine. You may form by the compound containing one or more of these, an oxide compound, a nitride compound, etc. The planarization layer 12 using these materials is formed by a chemical production method such as a spray method, a coating method, or a CVD method, and a physical production method such as a vacuum deposition method, an ion plating method, or a sputtering method. The chemical production method is a method of producing the planarization layer 12 by hydrolysis of chloride or thermal decomposition reaction of an organic compound. Further, the planarization layer 12 may be formed by application of a substance containing these materials, heat curing, or the like.

In the present embodiment, the thickness of the planarization layer 12 is, for example, more than 0 nm and 300 nm or less. From the viewpoint of preventing color mixing between the color filters of the plurality of colors constituting the color filter layer 100, the planarization layer 12 is preferably as thin as possible. Further, the planarization layer 12 preferably has a transmittance for visible light of 90% or more, and more specifically, it preferably has a transmittance of 95% or more. In the present embodiment, the shape of the first color filter 14 is processed using a dry etching method, but the etching rate is slower than that of the first color filter 14, and the second color filter 15 and the third color filter 16. The planarization layer 12 is formed in the lower part of the substrate.
In the present embodiment, the process of forming the first color filter 14, the transparent protective layer 13, and the etching mask on the planarizing layer 12 is the same as that in the first embodiment.

  On the other hand, in this embodiment, an inorganic compound is employed as the material for the planarization layer 12. Specifically, the material of the planarizing layer 12 is one of silicon, carbon, oxygen, hydrogen, tin, zinc, indium, aluminum, gallium, titanium, molybdenum, tungsten, niobium, tantalum, hafnium, silver, fluorine, and the like. A compound containing one or more, an oxide compound, a nitride compound, or the like is used. These inorganic compounds are resistant to dry etching with respect to a gas containing fluorine, and the etching rate of the planarization layer 12 is reduced. For this reason, the planarization layer 12 of the present embodiment using an inorganic compound as a material is not etched when the color filter at a desired position in the color filter layer 100 is removed by dry etching, and the planarization layer 12 below the planarization layer 12 is not etched. Etching of the semiconductor substrate 10 can be prevented.

Specifically, in the dry etching of the transparent protective layer 13 and the first color filter 14 when the rare gas alone or the mixed gas of the reactive gas and the rare gas is 90% or more of the total gas flow rate, The transparent protective layer 13, the first color filter 14, and a part of the planarizing layer 12 exposed in the portion 20b (see FIG. 3-2 (g)) are etched. At this time, in order to reduce damage to the semiconductor substrate 10, multi-stage etching may be performed in which the etching is stopped halfway and the ratio of the rare gas that is physically etched is reduced stepwise.
In the case of multi-stage etching, in the stage of reducing the ratio of the rare gas, the first gas exposed to the opening 20b using a gas that is difficult to etch the planarizing layer 12 and the semiconductor substrate 10, that is, an oxygen-based gas or a fluorine-based gas. All the color filters 14 are etched. In the dry etching at this stage, since the etching rate of the flattening layer 12 is low, the first color filter 14 is etched without residue, and the flattening layer 12 is etched for a time that does not disappear (remain). .

At this time, as long as the planarizing layer 12 is not completely removed, a dry etching gas may be mixed with a rare gas to perform etching with increased anisotropy. In the case of this condition, the material of the planarizing layer 12 is easily contained in the partition wall 30 due to the physical impact of the rare gas. When a material containing Si is used as the material of the planarizing layer 12, there is an advantage that the partition walls 30 can easily contain SiO ₂ or the like and the refractive index of the partition walls can be easily controlled.
In the second color filter forming process, the dry etching process is the same as in the first embodiment.

  As described above, in the manufacturing process of the solid-state imaging device 2 according to the present embodiment, the flattening layer 12 remains other than the lower part of the first color filter 14 by performing the dry etching process as described above. Therefore, unlike the solid-state imaging device 1 according to the first embodiment, the planarization layer 12 is also maintained below the second color filter 15 and the third color filter 16 as shown in FIG. In this embodiment, since the planarization layer 12 remains in the dry etching process, the complexity of the process of forming the planarization layer 12 is increased compared to the first embodiment, but the semiconductor substrate 10 by the dry etching process is increased. The effect that it is easy to suppress the plasma damage to is obtained.

Specifically, the use of an inorganic material for the planarizing layer 12 complicates the formation process of the planarizing layer 12, but the planarization layer 12 is used as an etching stopper layer, so that plasma to the semiconductor substrate 10 can be obtained. Damage can be reduced. Further, since the reaction product of the planarization layer 12 and the dry etching gas is included in the partition wall 30, the refractive index of the partition wall 30 can be adjusted. Moreover, the effect which suppresses the color mixture between the several color filters in the color filter layer 100 can be improved because the layer of the inorganic type reaction product is contained in the partition 30.
The second color filter 15 and third color filter forming step (third step) and the microlens forming step (fourth step) are the same as in the first embodiment.
Hereinafter, the solid-state imaging device of the present invention and the solid-state imaging device according to the conventional method will be described in detail with reference to Example 1. In this example, a solid-state imaging device was obtained by using the manufacturing method of the solid-state imaging device 1 (see FIG. 1) according to the first embodiment.

Example 1
(Formation of planarization layer)
A coating liquid containing an acrylic resin is spin-coated at a rotational speed of 3000 rpm on a semiconductor substrate 10 including two-dimensionally arranged photoelectric conversion elements 11, and subjected to a heat treatment at 230 ° C. for 6 minutes on a hot plate. The resin was cured to form the planarization layer 12. At this time, the thickness of the planarizing layer 12 was 50 nm, and the visible light transmittance was 98%.

(Formation of the first color filter)
Next, as a first color filter material containing a green pigment which is the first color of the color filters constituting the color filter layer 100, a green pigment dispersion containing a thermosetting resin is flattened. The layer 12 was spin-coated at 1000 rpm. The green pigment of the first color filter material has a color index of C.I. I. PG58 was used, and the pigment concentration was 70% by mass and the film thickness was 500 nm.
Next, in order to cure the first color filter material (green filter material), the first color filter 14 was thermally cured by baking on a hot plate at a temperature of 230 ° C. for 6 minutes.

(Formation of transparent protective layer)
Next, on the first color filter 14 (green filter), the viscosity of the coating solution containing acrylic resin is adjusted and spin-coated at a rotational speed of 3000 rpm. The resin was cured to form a transparent protective layer 13. The film thickness of the transparent protective layer 13 at this time was 20 nm, and the visible light transmittance of the transparent protective layer 13 was 99%. In addition, the coating liquid containing an acrylic resin used at this time is prepared by diluting a material for transferring a microlens 18 described later to adjust the viscosity.

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 a temperature of 90 ° C. for 1 minute. As a result, a sample in which a positive resist serving as an etching mask was applied with a film thickness of 1.5 μm was produced.
Next, this sample was subjected to photolithography for exposure through a photomask. For photolithography, an exposure apparatus having a light source capable of irradiating ultraviolet rays having an i-line wavelength was used. The positive type resist has undergone a chemical reaction upon irradiation with ultraviolet rays and has been dissolved in the developer.

Next, a development step is performed using 2.38% by mass of TMAH (tetramethylammonium hydride) as a developer, and the second color filter 15 and the third color filter 16 are formed on the semiconductor substrate 10. An etching mask having an opening was formed.
When using a positive resist, the positive resist is often cured by dehydration baking after development. However, in this example, the baking process was not performed to facilitate removal of the etching mask after dry etching. As a result, the resist is not cured and the improvement of the selection ratio cannot be expected. Therefore, the film thickness of the positive resist is more than twice the film thickness of the first color filter 14 that is a green filter. Formed with. The opening pattern of the etching mask at this time was formed to be 1.1 μm × 1.1 μm.
In this example, an etching mask pattern using a positive resist was formed in this way.

Next, dry etching of the transparent protective layer 13 and the first color filter 14 as a green filter was performed using the formed etching mask pattern. As a dry etching apparatus used at this time, an ICP dry etching apparatus was used. In addition, multistage dry etching was performed in which dry etching conditions were changed during the dry etching so as not to affect the semiconductor substrate 10 that is the base of the transparent protective layer 13 and the first color filter 14.
Etching was performed using a mixed gas of CF ₄ , O _2, and Ar gas as the first gas species in the multistage dry etching. The gas flow rates of CF ₄ and O ₂ were each 5 ml / min, and the Ar gas flow rate was 200 ml / min. That is, in the total gas flow rate, the Ar gas flow rate was 95.2%. In this case, the dry etching conditions were set such that the pressure in the chamber in the dry etching apparatus was 1 Pa, the RF power was 500 W, and the coil power was 1000 W.

In this example, as a result of evaluating the etching rate under the dry etching conditions described above, the etching rate of the transparent protective layer 13 was approximately one half of the etching rate of the green filter (corresponding to the first color filter 14). It was. Therefore, the etching time is adjusted assuming that the film thickness of the first color filter 14 is 540 nm in the film thickness configuration where the film thickness of the transparent protective layer 13 is 20 nm and the film thickness of the first color filter 14 is 500 nm. Carried out.
In this embodiment, assuming that the film thickness of the first color filter 14 is 540 nm using this dry etching condition, at the stage where 370 nm of the film thickness of the first color filter 14 is dry etched, The dry etching conditions were changed.

As the next gas type in the multistage dry etching in this example, a mixed gas in which CF ₄ gas and O ₂ gas were mixed was used. Also, dry etching conditions were a CF ₄ gas flow rate of 150 ml / min, an O ₂ gas flow rate of 150 ml / min, mixed at a ratio of 50:50, a chamber pressure of 2 Pa, RF power of 500 W, and coil power of 1000 W. Conditions. Using this dry etching condition, dry etching was performed on the first color filter 14 (green filter in this embodiment) having a residual content of 170 nm. The acrylic resin layer formed as the planarizing layer 12 is 50 nm below the first color filter 14, and the lower layer of the planarizing layer 12 is the semiconductor substrate 10. Since the semiconductor substrate 10 would be etched with a CF ₄ gas were changed to gas conditions without using CF ₄ gas at the stage where the film thickness of the planarizing layer 12 remains 50nm.
O ₂ gas was used as the next gas type in the multistage dry etching in this example. The dry etching conditions were such that the O ₂ gas flow rate was 150 ml / min, the pressure in the chamber was 2 Pa, the RF power was 100 W, and the coil power was 1000 W. Using this dry etching condition, dry etching of the remaining flattening layer 12 with a film thickness of 50 nm was performed.

Further, during the dry etching, the first color filter material (the green filter pattern) has a side wall of the first color filter material and the acrylic resin material that is the material of the planarizing layer 12, and a dry etching gas. A partition wall 30 containing the reaction product was formed. In this embodiment, the dimension (lateral width) of the partition wall 30 can be controlled by adjusting the time of dry etching conditions. Under the dry etching conditions in the present embodiment, the first color filter 14 is 500 nm and the planarization layer 12 is dry etched as described above. The size (width) of the partition wall due to these reaction products during dry etching. Was 25 nm. Further, the semiconductor substrate 10 below the planarizing layer 12 often has a protective layer containing Si formed on the surface. For this reason, the semiconductor substrate 10 may be etched as long as the photoelectric conversion element 11 is not damaged. In this case, since the Si component that is the surface protective layer of the semiconductor substrate 10 is included in the reaction product at the time of dry etching, the partition wall 30 includes the Si component.
Next, the positive resist used as an etching mask in the dry etching process was removed. The method for removing the positive resist is a method using a solvent. Specifically, the positive resist was removed by a spray cleaning apparatus using a stripping solution 104 (manufactured by Tokyo Ohka Kogyo Co., Ltd.).

(Production of second color filter)
Next, the formation process of the 2nd color filter 15 was performed. In order to provide the second color filter 15, a blue resist containing a blue pigment dispersion and having photosensitivity was applied to the entire surface of the semiconductor substrate 10. At this time, the pigments used for the blue resist are C.I. I. PB156, C.I. I. PV23 and the pigment concentration was 50% by mass. The film thickness of the second color filter 15 (blue filter in this example) was 570 nm. Further, as the resin that is the main component of the blue resist, an acrylic resin having photosensitivity was used. In addition, before applying the blue resist on the semiconductor substrate 10, HMDS treatment may be performed in order to improve adhesion to the semiconductor substrate 10.
Next, the blue resist was selectively exposed by photolithography and developed to form a pattern of the second color filter 15.

Next, in order to harden the second color filter 15, baking was performed on a hot plate at a temperature of 230 ° C. for 6 minutes. The second color filter 15 after the heating process was not peeled off or collapsed in the pattern even though the third color filter 16 was formed. The second color filter 15 is covered with the first color filter 14 (green filter) having good rectangularity and the partition wall 30 and is formed with good rectangularity. For this reason, it was confirmed that the second color filter 15 is cured with good adhesion between the bottom surface (for example, the surface of the semiconductor substrate 10) and the periphery (for example, the partition wall 30).
In this embodiment, a transparent protective layer 13 is formed on the first color filter 14 (green filter), and the first color filter 14 and the second color filter 15 (blue filter) are It has a configuration that does not come into physical contact. For this reason, in this embodiment, even after the heating process of the second color filter 15, needle-like crystals due to color mixing and reaction between the first color filter 14 and the second color filter 15 are not confirmed. It was.

(Production of third color filter)
Next, the formation process of the 3rd color filter 16 was performed. In order to provide the third color filter 16, a red resist containing a red pigment dispersion and having photosensitivity was applied to the entire surface of the semiconductor substrate 10. At this time, the pigments used for the red resist are C.I. I. PR254, C.I. I. PY139, and the pigment concentration was 60% by mass. The film thickness of the third color filter 16 (red filter in this example) was 570 nm.

Next, the red resist was selectively exposed by photolithography and developed to form a pattern of the third color filter 16.
Next, in order to harden the third color filter 16, baking was performed on a hot plate at a temperature of 230 ° C. for 6 minutes. Further, the third color filter 16 is covered with the first color filter 14 (green filter) having good rectangularity and the partition wall 30, and is formed with good rectangularity. For this reason, it was confirmed that it hardened | cured with sufficient adhesiveness between a bottom face (for example, the surface of the semiconductor substrate 10) and circumference | surroundings (for example, the partition 30).

In this embodiment, a transparent protective layer 13 is formed on the first color filter 14 (green filter), and the first color filter 14 and the third color filter 16 (red filter) are It has a configuration that does not come into physical contact. For this reason, in this example, even after the heating process of the third color filter 16, needle-like crystals due to the color mixture and reaction of the first color filter 14 and the third color filter 16 were not confirmed.
In this embodiment, the film thickness A (500 nm) of the first color filter 14 containing the green pigment, the film thickness (50 nm) of the planarizing layer 12 below the first color filter 14, The film thickness B (20 nm) of the upper transparent protective layer 13 of one color filter 14 and the film thickness C (570 nm) of the second color filter 15 and the third color filter are the solid-state imaging device according to the first embodiment. The film thickness is based on 1. In this embodiment, the lower layer of the second color filter 15 and the third color filter is the semiconductor substrate 10 and the planarization layer 12 does not exist.

Next, an acrylic resin that is the same material as the material used for the transparent protective layer 13 and whose viscosity is adjusted on the color filter layer 100 constituted by the color filters of a plurality of colors formed in the above-described steps in the present embodiment. The coating solution containing was spin-coated at a rotation speed of 1000 rpm, and heat treatment was performed at a temperature of 200 ° C. for 10 minutes on a hot plate to cure the resin, thereby forming the microlens transfer layer 19 with a thickness of 2 μm.
Next, on the microlens transfer layer 19, a resin having alkali solubility, photosensitivity, and thermal reflow property was applied to form a photosensitive sacrificial layer. Thereafter, the photosensitive sacrificial layer was patterned by a photolithography process using a photomask, and then heat-treated at a temperature of 250 ° C. to form the microlens matrix layer 19a. The microlens matrix layer 19a had a smooth hemispherical shape with a thickness of about 0.5 μm.

Next, dry etching is performed using a mixed gas of CF ₄ and C ₃ F ₈ which is a fluorocarbon gas, the pattern of the microlens matrix layer 19a is transferred to the microlens transfer layer 19, and the microlens 18 is attached. Formed. Here, the dry etching time during the pattern transfer of the microlens matrix layer 19a was 8 minutes. In this embodiment, the microlens 18 having a height from the hemispherical lens top to the lens bottom of 500 nm is formed. Thereby, the solid-state imaging device of Example 1 was completed. (See FIGS. 1 and 6-2 (d))

  In the solid-state imaging device according to the present embodiment obtained as described above, the flattening layer 12 is formed 50 nm below the first color filter 14, and the lower portions of the second color filter 15 and the third color filter 16 are A semiconductor substrate 10 is formed. Moreover, since the 1st color filter (green filter) which is the 1st color among several color filters uses the thermosetting resin, it is possible to raise the density | concentration of the pigment in solid content. For this reason, the first color filter 14 of the solid-state imaging device according to the present embodiment was able to obtain desired spectral characteristics while being a thinner film than when patterned using a conventional photosensitive resist. In the present embodiment, the second color filter 15 (blue filter) and the third color filter (red filter) use photosensitive resin as a material. However, in the solid-state imaging device according to this embodiment, unlike the conventional process, the pattern of the first color filter 14 and the partition wall 30 formed with good rectangularity is a guide pattern, so the second color filter 15 and When the third color filter 16 is formed, it is only necessary to form a pattern so as to fill a portion surrounded by the four sides by the partition wall 30. For this reason, in the second color filter 15 and the third color filter 16 in the present embodiment, the ratio of the photosensitive resin can be reduced as compared with the conventional case. Therefore, the pigment concentration of the second color filter 15 and the third color filter 16 can be increased to easily form desired spectral characteristics even if the film thickness is thin. In addition, since there is no flattening layer 12 below the blue filter and red filter formation locations, the amount of the flattening layer 12 is smaller than the combined thickness of the green filter and the upper transparent protective layer 13. Only the blue filter and the red filter can be formed thick.

  Due to these effects, in the solid-state imaging device according to the present embodiment, the color filters of the first color filter 14 (green filter), the second color filter 15 (blue filter), and the third color filter 16 (red filter) are used. Since the film thickness can be reduced as compared with the conventional case, the distance from the microlens 18 to the semiconductor substrate 10 is shorter than that of the conventional solid-state imaging device, and the sensitivity is improved.

Conventionally, when a material for a green filter having a high pigment content is used, the spectral characteristics may change due to a reaction with a solvent used in the dry etching process or another color filter material. However, in the present embodiment, the upper portion of the first color filter 14 is covered with the transparent protective layer 13, and other color filters (second color filter 15 (blue filter) and third color filter 16 (red filter) are covered. )) Is not in contact with the forming step, and no color mixing occurs between the first color filter 14, the second color filter 15, and the third color filter. Thereby, in this embodiment, the spectral characteristics are not changed, and there is no influence of color mixing between the color filters, so that needle crystals are suppressed, and desired spectral characteristics are obtained.
In this embodiment, a thermosetting resin material is used as the first color filter material in order to improve the curability and solvent resistance of the green filter which is the first color filter 14, but depending on the desired spectral characteristics. Alternatively, the first color filter may be formed using only a photocurable resin or a material using a combination of a thermosetting resin and a photocurable resin, with emphasis on pigment concentration, time-dependent characteristics, and the like.

(Example 2)
Hereinafter, the solid-state imaging device of the present invention and the solid-state imaging device according to the conventional method will be described in detail by Example 2. In Example 2, a solid-state imaging device was obtained using the method for manufacturing the solid-state imaging device 2 (see FIG. 9) according to the second embodiment.
First, an ITO film was formed as the planarization layer 12 on the semiconductor substrate 10 including the photoelectric conversion elements 11 arranged two-dimensionally. The ITO film as the planarizing layer 12 was formed with a film thickness of 30 nm using a magnetron sputtering method. The ITO film was formed at a temperature near room temperature, and was formed to be an amorphous film that could be easily processed.

Next, in order to open the electrode portion of the semiconductor substrate 10, wet etching of the semiconductor substrate 10 was performed using an etching solution containing about 5% oxalic acid. At the time of wet etching of the semiconductor substrate 10, a positive resist (OFPR-800: manufactured by Tokyo Ohka Kogyo Co., Ltd.) was spin-coated at a rotation speed of 750 rpm, and then prebaked at 90 ° C. for 1 minute. Thus, a sample in which a positive resist serving as an etching mask was applied at a film thickness of 2.0 μm was produced.
Next, this sample was subjected to photolithography for exposure through a photomask. For photolithography, an exposure apparatus having a light source capable of irradiating ultraviolet rays having an i-line wavelength was used. The positive resist is dissolved in the developer by causing a chemical reaction when irradiated with ultraviolet rays.

Next, a development process using 2.38% by mass of TMAH (tetramethylammonium hydride) as a developer was performed to form an etching mask having an opening in the electrode portion of the semiconductor substrate 10. Next, it was immersed in an etching solution for 3 minutes, wet etching was performed, and the substrate was washed with pure water to open the electrode portion of the semiconductor substrate 10.
Next, the positive resist used as an etching mask in the wet etching of the semiconductor substrate 10 was removed. The positive resist removal method was a method using a solvent, and the positive resist was removed by a spray cleaning apparatus using a stripping solution 104 (manufactured by Tokyo Ohka Kogyo Co., Ltd.).

Next, heat treatment was performed at 250 degrees for 30 minutes on a hot plate to crystallize the ITO film as the planarizing layer 12. At this time, the sheet resistance was 50Ω / sq. Or less, and the visible light transmittance was 94%.
Next, as a first color filter material containing a green pigment which is the first color of the color filters constituting the color filter layer 100, a green pigment dispersion containing a thermosetting resin is flattened. The layer 12 was spin-coated at 1000 rpm. The green pigment of the first color filter material has a color index of C.I. I. PG58 was used, and the pigment concentration was 70% by mass and the film thickness was 500 nm.
Next, in order to cure the first color filter material, it was baked on a hot plate at a temperature of 230 ° C. for 6 minutes to thermally cure the first color filter 14.

(Formation of transparent protective layer)
Next, the viscosity of the coating solution containing acrylic resin is adjusted on the first color filter 14 (in this example, a green filter) and spin-coated at a rotation speed of 3000 rpm. The resin was cured by performing a heat treatment for minutes, and the transparent protective layer 13 was formed. The film thickness of the transparent protective layer 13 at this time was 20 nm, and the visible light transmittance of the transparent protective layer 13 was 99%. In addition, the coating liquid containing an acrylic resin used at this time is prepared by diluting a material for transferring a microlens 18 described later to adjust the viscosity.

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 a temperature of 90 ° C. for 1 minute. As a result, a sample in which a positive resist serving as an etching mask was applied with a film thickness of 1.5 μm was produced.
Next, this sample was subjected to photolithography for exposure through a photomask. For photolithography, an exposure apparatus having a light source capable of irradiating ultraviolet rays having an i-line wavelength was used. The positive resist is dissolved in the developer by causing a chemical reaction when irradiated with ultraviolet rays.

Next, a development step is performed using 2.38% by mass of TMAH (tetramethylammonium hydride) as a developer, and the second color filter 15 and the third color filter 16 are formed on the semiconductor substrate 10. An etching mask having an opening was formed. When using a positive resist, the positive resist is often cured by dehydration baking after development. However, in Example 2, the baking process was not performed to facilitate the removal of the etching mask after dry etching. As a result, the resist is not cured and the improvement of the selection ratio cannot be expected. Therefore, the film thickness of the positive resist is more than twice the film thickness of the first color filter 14 that is a green filter. Formed with. The opening pattern at this time was formed to be 1.1 μm × 1.1 μm.
In this example, an etching mask pattern using a positive resist was formed in this way.

Next, dry etching of the transparent protective layer 13 and the first color filter 14 was performed using the formed etching mask pattern. At this time, an ICP dry etching apparatus was used as the dry etching apparatus used. Also, dry etching conditions were changed halfway so that the underlying semiconductor substrate 10 was not affected, and dry etching was performed in multiple stages.
As the first gas species in the multistage dry etching, etching was performed using a gas in which three kinds of CF ₄ , O ₂ , and Ar gas were mixed. The gas flow rates of CF ₄ and O 2 were each 5 ml / min, and the Ar gas flow rate was 200 ml / min. That is, in the total gas flow rate, the Ar gas flow rate was 95.2%. The dry etching conditions at this time were set such that the pressure in the chamber in the dry etching apparatus was 1 Pa, the RF power was 500 W, and the coil power was 1000 W.

In this example, as a result of evaluating the etching rate under the above-described dry etching conditions, the etching rate of the transparent protective layer 13 is approximately half of the etching rate of the first color filter 14 (green filter in this example). Met. Therefore, the etching time is adjusted on the assumption that the film thickness of the first color filter 14 is 540 nm in the film thickness configuration where the film thickness of the transparent protective layer 13 is 20 nm and the film thickness of the first color filter 14 is 500 nm. Carried out.
In this example, using the dry etching conditions, it was assumed that the film thickness of the first color filter 14 (green filter) was 540 nm, so that 370 nm of the film thickness of the first color filter 14 was dry etched. At the stage, the following dry etching conditions were changed.

As the next gas type in the multistage dry etching in this example, a mixed gas in which CF ₄ gas and O ₂ gas were mixed was used. The dry etching conditions were: CF ₄ gas flow rate of 150 ml / min, O 2 gas flow rate of 150 ml / min, 50:50 ratio, chamber pressure of 2 Pa, RF power of 500 W, and coil power of 1000 W. Condition. Using this dry etching condition, dry etching of the remaining portion of the first color filter 14 (green filter in this embodiment) was performed. The ITO film formed as the planarizing layer 12 has a structure in which the etching rate of CF ₄ gas and O ₂ gas is 20 times or more slower than the etching rate of the first color filter 14 and is hardly etched. At this time, overetching is performed at a time setting for etching 510 nm, which is three times the film thickness 170 nm of the remaining first color filter 14, so that no green residue of the first color filter 14 remains after dry etching. Carried out. By this step, no residue remains in the first color filter 14, and the ITO film is etched by 5 nm within a thickness of 30 nm.

Further, during the dry etching described above, the transparent protective layer 13 and the green filter pattern (corresponding to the first color filter 14) on the side walls of the green filter material, the transparent protective layer 13 and the planarizing layer 12 ITO. A partition wall 30 containing a reaction product of the material and the dry etching gas was formed. The partition wall 30 can control the dimension (width) of the partition wall 30 by adjusting the time of dry etching conditions.
Under the dry etching conditions described above, the green filter (corresponding to the first color filter 14) was dry etched by 500 nm, the transparent protective layer 13 by 20 nm, and the planarizing layer 12 by 5 nm. The dimension of the partition wall 30 formed of the object was 30 nm.
Next, the positive resist used as an etching mask in the dry etching process was removed. The method for removing the positive resist is a method using a solvent. Specifically, the positive resist was removed by a spray cleaning apparatus using a stripping solution 104 (manufactured by Tokyo Ohka Kogyo Co., Ltd.).

(Production of second color filter)
Next, the formation process of the 2nd color filter 15 was performed. In order to provide the second color filter 15, a blue resist containing a blue pigment dispersion and having photosensitivity was applied to the entire surface of the semiconductor substrate 10. At this time, the pigments used for the blue resist are C.I. I. PB156, C.I. I. PV23 and the pigment concentration was 50% by mass. The film thickness of the second color filter 15 (blue filter in this example) was 570 nm. Further, as the resin that is the main component of the blue resist, an acrylic resin having photosensitivity was used. In addition, before applying the blue resist on the semiconductor substrate 10, HMDS treatment may be performed in order to improve adhesion to the semiconductor substrate 10.
Next, the blue resist was selectively exposed by photolithography and developed to form a pattern of the second color filter 15.

Next, in order to harden the second color filter 15, baking was performed on a hot plate at a temperature of 230 ° C. for 6 minutes. The second color filter 15 after the heating process was not peeled off or collapsed in the pattern even though the third color filter 16 was formed. The second color filter 15 is covered with the first color filter 14 (green filter) with good rectangularity and the partition wall 30 and is formed with good rectangularity. Therefore, the second color filter 15 is It was confirmed that the resin cured with good adhesion between the bottom surface (for example, the surface of the semiconductor substrate 10) and the periphery (for example, the partition wall 30).
In this embodiment, a transparent protective layer 13 is formed on the first color filter 14 (green filter), and the first color filter 14 and the second color filter 15 (blue filter) are It has a configuration that does not come into physical contact. For this reason, in this embodiment, even after the heating process of the second color filter 15, needle-like crystals due to color mixing and reaction between the first color filter 14 and the second color filter 15 are not confirmed. It was.

(Production of third color filter)
Next, the formation process of the 3rd color filter 16 was performed. A red resist containing a red pigment dispersion and having photosensitivity was applied on the entire surface of the semiconductor substrate 10 to provide the third color filter 16. At this time, the pigments used for the red resist are C.I. I. PR254, C.I. I. PY139, and the pigment concentration was 60% by mass. The film thickness of the third color filter 16 (red filter in this example) was 570 nm.
Next, the red resist was selectively exposed by photolithography and developed to form a pattern of the third color filter 16.

Next, in order to harden the third color filter 16, baking was performed on a hot plate at a temperature of 230 ° C. for 6 minutes. The third color filter 16 is covered with the first color filter 14 (green filter) having good rectangularity and the partition wall 30 and is formed with good rectangularity. For this reason, it was confirmed that it hardened | cured with sufficient adhesiveness between a bottom face (for example, the surface of the semiconductor substrate 10) and circumference | surroundings (for example, the partition 30).
In this embodiment, a transparent protective layer 13 is formed on the first color filter 14 (green filter), and the first color filter 14 and the third color filter 16 (red filter) are It has a configuration that does not come into physical contact. For this reason, in this example, even after the heating process of the third color filter 16, needle-like crystals due to the color mixture and reaction of the first color filter 14 and the third color filter 16 were not confirmed.

In the present embodiment, the film thickness A (500 nm) of the first color filter 14 containing the green pigment, the film thickness (20 nm) of the transparent protective layer 13 above the first color filter 14, The film thickness B (30 nm) of the planarizing layer 12 below the one color filter 14 and the film thickness C (570 nm) of the second color filter 15 and the third color filter are the solid-state imaging device according to the first embodiment. The film thickness is based on 1. In this embodiment, the planarizing layer 12 is formed with a film thickness of 25 nm below the second color filter 15 and the third color filter.
In this example, finally, a microlens 18 having a height from the lens top to the lens bottom of 500 nm was formed by the same method as in Example 1 above. Thereby, the solid-state imaging device of Example 2 was completed.

  In the solid-state imaging device according to the present embodiment obtained as described above, the planarizing layer 12 is formed to have a thickness of 30 nm below the first color filter 14, and below the second color filter 15 and the third color filter 16. The planarizing layer 12 is formed to 25 nm. Moreover, since the 1st color filter (green filter) which is the 1st color among several color filters uses the thermosetting resin, it is possible to raise the density | concentration of the pigment in solid content. For this reason, the first color filter 14 of the solid-state imaging device according to the present embodiment was able to obtain desired spectral characteristics while being a thinner film than when patterned using a conventional photosensitive resist. In the present embodiment, the second color filter 15 (blue filter) and the third color filter 16 (red filter) use photosensitive resin as materials. However, in the solid-state imaging device according to the present embodiment, the first color filter 14 formed with good rectangularity is a guide pattern unlike the conventional process, and therefore the second color filter 15 and the third color filter 16. When forming the pattern, it is only necessary to form a pattern so as to fill a portion surrounded by the partition wall 30 with four sides. For this reason, in the second color filter 15 and the third color filter 16 in the present embodiment, the ratio of the photosensitive resin can be reduced as compared with the conventional case. Therefore, the pigment concentration of the second color filter 15 and the third color filter 16 can be increased to easily form desired spectral characteristics even if the film thickness is thin.

Due to these effects, in the solid-state imaging device according to the present embodiment, each color filter of the first color filter 14 (green filter), the second color filter 15 (blue filter), and the third color filter 16 (red filter). Therefore, the distance from the microlens to the semiconductor substrate is shorter than that of the conventional solid-state imaging device, and the sensitivity is improved.
Further, in the solid-state imaging device according to the present embodiment, since there is the planarization layer 12 formed of an ITO film on the semiconductor substrate 10, it functions as an etching stopper layer during etching. Further, since the ITO film is conductive, it has an effect of evading plasma damage during dry etching of the first color filter 14 (green filter). For this reason, the influence of dry etching was not observed on the plurality of photoelectric conversion elements 11 formed on the semiconductor substrate 10.

  Furthermore, the material of the first color filter 14 made of a green filter was hardened by thermosetting, and the solvent resistance was improved. Conventionally, when a green filter material having a high pigment content is used to form a green filter, the spectral characteristics may change due to reaction with a solvent or other color filter material. On the other hand, in the solid-state imaging device according to the present embodiment, it is possible to improve the solvent resistance by performing the above-described thermosetting on the first color filter 14, and it is possible to suppress changes in spectral characteristics.

  In this embodiment, a thermosetting resin is used to improve the curability and solvent resistance of the first color filter 14 (green filter). However, depending on the desired spectral characteristics, the pigment concentration, the temporal characteristics, etc. The first color filter 14 may be formed using only a photocurable resin or a material using a thermosetting resin and a photocurable resin in combination. In this embodiment, in order to obtain desired spectral characteristics with the second color filter 15 (blue filter) and the third color filter 16 (red filter), the film thickness is made thicker than that of the first color filter 14. ing. Therefore, the height of each of the color filters of the plurality of colors is not the same, and the second color filter 15 and the third color filter 16 are connected to the first color filter 14 as illustrated in FIG. In comparison, the structure protrudes toward the planarization layer 12 side. In the present embodiment, the second color filter 15 and the third color filter 16 have a structure that protrudes to the flattening layer 12 side by about 45 nm as compared with the first color filter 14.

<Conventional example 1>
Based on the conventional method described in Patent Document 1, a color filter pattern of a plurality of colors was formed by a photolithography process.
However, the film thickness of the three colors of the green filter, the blue filter, and the red filter was set to a thin film of 700 nm, and a flattening layer (100 nm) was provided in the lower layer of all the color filters of a plurality of colors. Further, since a photolithography process is used, there is no transparent protective layer on the green filter.
Other than that, a solid-state imaging device was manufactured as Conventional Example 1 by a conventional method in the same manner as in Example 1 above.

<Conventional example 2>
In order to use for comparison with Example 1 and Example 2 described above, a sample in which a transparent protective layer was not formed on the first color filter was produced. In the manufacturing method, after forming a green filter, an etching mask is formed using a positive resist as it is without forming a transparent protective layer on the green filter. In the etching, the green filter is assumed to have a thickness of 500 nm and the etching time is adjusted. Other than that, the solid-state imaging device of Conventional Example 2 was manufactured by the conventional dry etching method under the same conditions as in Example 1 above.

(Evaluation)
The intensities of the red, green, and blue signals of the solid-state imaging devices of Example 1 and Example 2 above were adjusted to the spectral characteristics of the three-color film thicknesses of green, blue, and red by conventional photolithography at 700 nm. A comparative evaluation was performed with the intensity of the red signal, the green signal, and the blue signal of the solid-state imaging device of Conventional Example 1 manufactured with the structure and the solid-state imaging device of Conventional Example 2 having the conventional structure without a transparent protective layer.
Table 1 below corresponds to the solid-state image sensor according to Example 1 corresponding to the solid-state image sensor according to the first embodiment shown in FIG. 1 and the solid-state image sensor 2 according to the second embodiment shown in FIG. The evaluation results of the signal intensity of each color in the solid-state imaging device according to Example 2 are shown. The numerical values shown in Table 1 are values obtained by standardizing the signal intensity of each color in the solid-state imaging device according to the conventional example 2, the example 1, and the example 2 with the signal intensity of each color in the solid-state imaging device according to the conventional example 1. . That is, the numerical values shown in Table 1 indicate the ratio between the signal intensity of each color in the solid-state imaging device according to Conventional Example 1 and the signal intensity of each color in each of the solid-state imaging devices according to Conventional Example 2, Example 1, and Example 2. Show.

As shown in Table 1, the first color filter 14 (green filter) was thinned and formed with good rectangularity using a dry etching method, and the reaction product generated by the dry etching was formed as a partition wall 30. The solid-state image sensor of Example 1 and the solid-state image sensor of Example 2 and the solid-state image sensor of Conventional Example 2 formed by conventional dry etching are compared with the solid-state image sensor of Conventional Method Example 1 formed by conventional photolithography. As a result, the signal intensity of each color increased.
This is because the solid-state imaging device according to the first embodiment and the second embodiment has the partition wall 30, so that when incident light from an oblique direction of the pixel passes through one color filter and travels to another color filter, the partition wall This is because the incident is blocked by 30 or the optical path is changed. Thereby, in the solid-state imaging device according to the first embodiment and the second embodiment, light traveling from one color filter to the other color filter is suppressed from entering the photoelectric conversion element 11 corresponding to the other color filter, and color mixing is performed. Is suppressed.

In the solid-state imaging device according to the first embodiment and the second embodiment, the partition wall 30 also blocks the transfer from other colors between the plurality of color filters by the partition wall 30, thereby suppressing color mixing.
As a result of evaluating the spectral characteristics of Example 1 and Example 2 and Conventional Example 2 without the formation of the transparent protective layer produced by the conventional dry etching method, Examples 1 and 2 are compared with Conventional Example 2 An increase in green signal strength was observed. This is because the conventional dry etching method does not have a transparent protective layer on the green filter, so that a slight amount of needle-like crystals due to color mixture is formed on the surface of the green filter when forming a blue filter and a red filter. . In Conventional Example 2, since the pigment concentration is improved in order to make the color filter thin, the material for the green filter is unstable, and color mixing occurs in the high temperature process when forming the color filters of other colors. This is because.

  When Example 1 and Example 2 were compared, Example 1 was higher in signal strength than Example 2. This is because the transmittance of the ITO film used as the planarizing layer 12 in Example 2 is slightly lower than the transmittance of the transparent resin used as the planarizing layer 12 in Example 1. In the first embodiment, etching conditions are set such that plasma damage does not occur on the semiconductor substrate during dry etching. Therefore, in Example 1, the semiconductor substrate 10 was not damaged. However, dry etching conditions that do not cause plasma damage to the semiconductor substrate 10 have a low degree of process freedom, and it can be assumed that the influence of plasma damage varies depending on the sample structure of the semiconductor substrate 10. For this reason, Example 1 and Example 2 in which the light receiving sensitivity is improved as compared with Conventional Method Example 1 may be used assuming signal strength, process difficulty, number of processes, process complexity, cost effects, and the like. I can do it.

  Although the present invention has been described above by the embodiments, the scope of the present invention is not limited to the illustrated and described exemplary embodiments, and brings about effects equivalent to those intended by the present invention. All embodiments are also included. Further, the scope of the invention is not limited to the combinations of features of the invention defined by the claims, but can be defined by any desired combination of specific features among all the disclosed features.

DESCRIPTION OF SYMBOLS 1, 2 Solid-state image sensor 10 Semiconductor substrate 11 Photoelectric conversion element 12 Flattening layer 13 Transparent protective layer 14 1st color filter 15 2nd color filter 16 3rd color filter 18 Micro lens 19 Micro lens transfer layer 19a Micro lens Matrix layer 20 Etching mask 30 Partition

Claims (16)

A semiconductor substrate having a plurality of photoelectric conversion elements arranged two-dimensionally;
A color filter layer formed on the semiconductor substrate and two-dimensionally arranged in a regular pattern with a plurality of color filters corresponding to the plurality of photoelectric conversion elements;
A planarization layer formed between the color filters of the plurality of colors and the semiconductor substrate;
A partition wall disposed between the color filters of the plurality of colors;
A microlens formed on the color filter layer and arranged two-dimensionally corresponding to each of the color filters of the plurality of colors;
A transparent protective layer disposed only between the color filter of the first color selected from the plurality of colors and the microlens;
A solid-state imaging device comprising: The solid-state imaging device according to claim 1, wherein the transparent protective layer is made of the same material as the microlens. The transparent protective layer is an organic compound containing at least one of silicon, carbon, oxygen, hydrogen, and nitrogen, and has a transmittance of 90% or more for visible light. Or the solid-state image sensor of Claim 2. The transparent protective layer is a single layer containing at least one of silicon, carbon, oxygen, hydrogen, nitrogen, fluorine, tin, zinc, indium, aluminum, gallium, titanium, molybdenum, tungsten, niobium, tantalum, hafnium, and silver. It is a layer or a multilayer, The solid-state image sensor of any one of Claims 1-3 characterized by the above-mentioned. The planarization layer is a single layer containing at least one of silicon, carbon, oxygen, hydrogen, nitrogen, fluorine, tin, zinc, indium, aluminum, gallium, titanium, molybdenum, tungsten, niobium, tantalum, hafnium, and silver. It is a layer or a multilayer, The solid-state image sensor of any one of Claims 1-4 characterized by the above-mentioned. 6. The solid-state imaging device according to claim 1, wherein the planarizing layer is formed only between the color filter of the first color and the semiconductor substrate. 7. . The flattening layer is an organic compound containing at least one of silicon, carbon, oxygen, hydrogen, and nitrogen, and has a transmittance of 90% or more with respect to visible light. The solid-state image sensor of any one of Claims 1-6. 8. The solid according to claim 1, wherein when the refractive index of the transparent protective layer is T and the refractive index of the microlens is n, the following formula (1) is satisfied. Image sensor.
n-1 ≦ T ≦ n + 1 (1) The said partition contains at least 1 sort (s) among zinc, copper, nickel, silicon, carbon, oxygen, hydrogen, nitrogen, bromine, and chlorine. Solid-state image sensor. The film thickness of the color filter of the first color is A (nm), the film thickness of the transparent protective layer is B (nm), and the film thickness of the color filter of the color other than the first color in the color filter layer is C ( nm), the thickness of the planarizing layer is D (nm), the visible light transmittance of the transparent protective layer is E (%), and the dimension of the partition wall is F (nm). The solid-state imaging device according to any one of claims 1 to 9, wherein: (7) to (7) are satisfied.
200 (nm) ≦ A ≦ 700 (nm) (2)
0 (nm) <B ≦ 200 (nm) (3)
0 (nm) <D ≦ 200 (nm) (4)
A + B−300 (nm) ≦ C ≦ A + B + 300 (nm) (5)
E ≧ 90 (%) (6)
F ≦ 200 (nm) (7) 11. The solid-state imaging device according to claim 1, wherein the color filter of the first color has a concentration of a pigment as a colorant of 50% by mass or more. The solid-state image sensor according to any one of claims 1 to 11, wherein the color filter of the first color contains a thermosetting resin. 13. The solid-state imaging device according to claim 1, wherein the area occupied by the color filter of the first color is the largest among the color filters of the plurality of colors. Forming a planarization layer on a semiconductor substrate in which a plurality of photoelectric conversion elements are two-dimensionally arranged, and then thermally curing the coating liquid applied on the planarization layer to form a first color filter; Next, a transparent protective layer is formed on the color filter of the first color, and after forming the transparent protective layer, a part of the color filter of the first color is removed by dry etching, and the transparent protective layer is formed. A first step of patterning the color filter of the first color formed on the top,
The outer periphery of the color filter of the first color is generated by a reaction product of the color filter of the first color and the dry etching gas generated when the color filter of the first color is dry-etched in the first step. A second step of forming partition walls in
After the second step, a third step of patterning a color filter of another color different from the color filter of the first color on the semiconductor substrate by photolithography,
And a fourth step of forming a microlens on top of the color filter of the first color and the color filter of the other color after the third step. The method for manufacturing a solid-state imaging device according to claim 14, wherein a heating temperature at the time of thermosetting the color filter of the first color in the first step is 170 ° C. or higher and 270 ° C. or lower. In the fourth step, the microlens is formed using an etch back method in which a dry etching mask is formed on the microlens forming material, and the microlens shape is transferred to the microlens forming material by dry etching. The manufacturing method of the solid-state image sensor of Claim 14 or Claim 15.

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