JP6838394B2 - Solid-state image sensor and its manufacturing method - Google Patents

Description

The present invention is a technique relating to a solid-state image sensor using a photoelectric conversion element such as a CCD or CMOS.

In recent years, solid-state image sensors such as CCDs (charge-coupled devices) and CMOSs (complementary metal oxide semiconductors) mounted on digital cameras and the like have been increasing in pixel count and miniaturization. The pixel size is less than 4 μm × 1.4 μm.

The solid-state image sensor is colorized by a photoelectric conversion element arranged in each of the pixels and a color filter layer having a predetermined color pattern. Further, the region (opening) in which each photoelectric conversion element 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% of the total area of the solid-state image sensor. Since a small opening directly leads to a decrease in sensitivity of the photoelectric conversion element, it is common to form a light-collecting microlens on the photoelectric conversion element in order to compensate for the decrease in sensitivity in a solid-state image sensor.
Further, in recent years, an image sensor using a backside illumination technique has been developed, and the opening of the photoelectric conversion element can be 50% or more of the total area of the solid-state image sensor. However, in this case, since there is a possibility that the leaked light of another color filter adjacent to one color filter enters, it is necessary to form a microlens of an appropriate size and shape.

As a method of forming a color filter layer of a predetermined pattern, a method of forming a pattern of color filters of each color by a photolithography process is usually used as described in Patent Document 1.
Further, as another method for forming a pattern, Patent Document 2 describes that a color filter layer of the first color is patterned and formed on a solid-state image sensor by a dry etching process, and color filter layers of the second and subsequent colors are formed by a photolithography step. A method of patterning and forming is described.
Further, Patent Document 3 describes a method of patterning and forming color filters of all colors by dry etching.

In recent years, the demand for high-definition CCD image sensors exceeding 8 million pixels has increased, and the demand for image sensors with a pixel size of less than 1.4 μm × 1.4 μm as the pixel size of the color filter pattern associated with these high-definition CCDs has increased. It's getting bigger. However, by reducing the pixel size, there is a problem that the resolvability of the color filter layer pattern-formed by the photolithography process is insufficient, which adversely affects the characteristics of the solid-state image sensor. In a solid-state image sensor with a pixel size of 1.4 μm or less on one side, or around 1.1 μm or 0.9 μm, insufficient resolution appears as color unevenness due to poor pattern shape.

Further, as the pixel size becomes smaller, the aspect ratio of the pattern of the color filter layer becomes larger (the thickness becomes larger with respect to the width of the pattern of the color filter layer). When such a color filter layer is patterned by a photolithography process, the part that should be originally removed (the part outside the effective area of the pixel) is not completely removed, and it becomes a residue and adversely affects the pixels of other colors. It ends up. At this time, if a method such as extending the developing time is performed in order to remove the residue, there is also a problem that the necessary cured pixels are peeled off.

Further, in order to obtain satisfactory spectral characteristics, the film thickness of the color filter must be increased. However, as the film thickness of the color filter increases, the resolution tends to decrease as the pixel miniaturization progresses, such as rounding the corners of each pattern-formed color filter. In order to increase the film thickness of the color filter and obtain spectral characteristics, it is necessary to increase the pigment concentration (concentration of the colorant) contained in the material of the color filter. However, if the pigment concentration is increased, the light required for the photocuring reaction does not reach the bottom of the color filter layer, and the color filter layer may be insufficiently cured. Therefore, there is a problem that the color filter layer is peeled off in the developing process in photolithography and pixel defects occur.

Further, when the film thickness of the color filter is reduced and the concentration of the pigment contained in the material of the color filter is increased in order to obtain the spectral characteristics, the photocurable component is relatively reduced. For this reason, the photocuring of the color filter layer becomes insufficient, and deterioration of the shape, in-plane shape non-uniformity, shape collapse, and the like are likely to occur. Further, by increasing the exposure amount at the time of curing in order to sufficiently photo-cure, there arises a problem that the throughput is lowered.

Due to the high definition of the pattern of the color filter layer, the film thickness of the color filter layer affects not only the problem in the manufacturing process but also the characteristics as a solid-state image sensor. When the thickness of the color filter layer is thick, light incident from an oblique direction may be separated by a color filter of a specific color and then enter into the filter pattern portion of another adjacent color and the photoelectric conversion element below it. is there. In this case, there is a problem that color mixing occurs. This problem of color mixing becomes more remarkable as the pixel size becomes smaller and the aspect ratio between the pixel size defining the pattern size and the film thickness of the color filter becomes larger. Further, the problem of color mixing of incident light becomes remarkable even when the distance between the color filter pattern and the photoelectric conversion element becomes long by forming a material such as a flattening layer on the substrate on which the photoelectric conversion element is formed. Occurs. Therefore, it is important to reduce the film thickness of the color filter layer and the flattening layer formed below the color filter layer.

From the above, in order to increase the number of pixels of the solid-state image sensor, it is necessary to increase the definition of the pattern of the color filter layer, and it is important to reduce the thickness of the color filter layer.
As described above, in the conventional pattern formation of the color filter layer formed by photolithography by making the color filter material photosensitive, as the pixel size becomes finer, the film thickness of the color filter layer becomes thinner. It is also required to be converted. In this case, since the content ratio of the pigment component in the color filter material increases, there are problems that a sufficient amount of the photosensitive component cannot be contained, resolution cannot be obtained, residue is likely to remain, and pixel peeling is likely to occur. There is a problem of deteriorating the characteristics of the solid-state image sensor.

Therefore, in order to make the pattern of the color filter layer finer and thinner, the techniques of Patent Documents 2 and 3 have been proposed. In Patent Documents 2 and 3, color filters of a plurality of colors are patterned by dry etching, which enables patterning without containing a photosensitive component, so that the pigment concentration in the material for the color filter can be improved. By these techniques using dry etching, it is possible to improve the pigment concentration, and it is possible to produce a color filter pattern that can obtain sufficient spectral characteristics even if the film is thinned.

Japanese Unexamined Patent Publication No. 11-68076 Japanese Patent No. 4857569 Japanese Patent No. 4905760

However, the inventors have found that the relationship between the film thicknesses of each color filter is not shown in Patent Documents 2 and 3, and it may not be possible to increase the sensitivity of all color filters.
The present invention has been made in view of the above points, and an object of the present invention is to provide a high-definition and highly sensitive solid-state image sensor with reduced color mixing.

In order to solve the problem, the solid-state imaging device according to one aspect of the present invention is formed on a semiconductor substrate in which a plurality of photoelectric conversion elements are two-dimensionally arranged and the above-mentioned semiconductor substrate, and is made to correspond to each photoelectric conversion element. Only between the color filter layer in which the color filters of a plurality of colors are two-dimensionally arranged in a preset regular pattern, and the color filter of the first color selected from the plurality of colors and the semiconductor substrate, which is provided in some cases. The lower flattening layer provided with the arranged lower flattening layer, the thickness of the color filter of the first color is A [nm], the thickness of the lower flattening layer is B [nm], other than the first color. When the film thickness of the color filter of the color is C [nm], the following formula is satisfied.
200 [nm] ≤ A ≤ 700 [nm]
0 [nm] ≤ B ≤ 200 [nm]
A + B-200 [nm] ≤ C ≤ A + B + 200 [nm]

Further, in the method for manufacturing a solid-state imaging device according to an aspect of the present invention, a lower flattening layer is formed on a semiconductor substrate, and a coating liquid for a color filter of a first color is applied and cured on the lower flattening layer. After forming the lower flattening layer and the color filter layer in this order, the lower flattening layer portion located below the color filter layer portion other than the arrangement position of the first color color filter and the color filter layer portion to be removed is formed. A first step of removing by dry etching to form a color filter of the first color, and after the first step, a color filter of a color other than the first color is patterned by photolithography or dry etching. It has a second step of forming.
The formation of the lower flattening layer may be omitted.

According to the aspect of the present invention, since it is possible to reduce the film thickness of each color filter and shorten the total distance from the microlens top to the device, it is possible to reduce color mixing and all the color filters arranged in a pattern can be used. It is possible to provide a high-definition solid-state image sensor with high sensitivity.

It is sectional drawing of the solid-state image sensor which concerns on embodiment of this invention. It is a partial plan view of the color filter array which concerns on embodiment of this invention. It is sectional drawing which shows the step order which shows the coating process of the 1st color filter pattern which concerns on 1st Embodiment, and the process order of opening the part which forms the 2nd and subsequent color filters by using a photosensitive resin pattern material. It is sectional drawing which shows the process of manufacturing the color filter pattern of the 1st color which concerns on embodiment of this invention by the dry etching method in the order of steps. It is sectional drawing which shows the process of manufacturing the color filter pattern of the 2nd and 3rd color of 1st Embodiment of this invention by photolithography in process order. It is sectional drawing which shows the manufacturing process of the microlens of 1st Embodiment of this invention in step order. It is sectional drawing which shows the case where the microlens of 1st Embodiment of this invention is manufactured by the transfer method by etch back in the order of a process. It is sectional drawing which shows the process of manufacturing the color filter pattern of the 2nd color of 1st Embodiment of this invention by dry etching in the order of steps. It is sectional drawing which shows the process of manufacturing the color filter pattern of the 3rd color of 1st Embodiment of this invention by dry etching in the order of steps. It is sectional drawing which shows the process of manufacturing the color filter pattern of the 1st color of 2nd Embodiment of this invention in the order of steps. It is sectional drawing which shows the process of manufacturing the color filter pattern of the 1st color of 3rd Embodiment of this invention in the order of steps. It is sectional drawing which shows the case where the color filter pattern of the 1st color of 3rd Embodiment of this invention is applied | coating the photosensitive resin pattern material of the next step only by light curing, in the order of a process.

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 and the plane dimension, the ratio of the thickness of each layer, and the like are different from the actual ones. Further, each embodiment shown below exemplifies a configuration for embodying the technical idea of the present invention, and the technical idea of the present invention describes the material, shape, structure, etc. of the constituent parts as follows. It is not specified as a thing. The technical idea of the present invention may be modified in various ways within the technical scope specified by the claims stated in the claims.

"First embodiment"
<Structure of solid-state image sensor>
As shown in FIG. 1, the solid-state image sensor according to the present embodiment includes a semiconductor substrate 10 having a plurality of two-dimensionally arranged photoelectric conversion elements 11 and a plurality of microlenses arranged above the semiconductor substrate 10. It includes a microlens group composed of 18, and a color filter layer 30 provided between the semiconductor substrate 10 and the microlens 18. The color filter layer 30 is configured by arranging color filters 14, 15 and 16 of a plurality of colors in a predetermined regular pattern.
In the solid-state image sensor of the present embodiment, the lower flattening layer 12 formed on the surface of the semiconductor substrate 10 is formed only under the color filter 14 having the largest area. However, if the adhesion between the semiconductor substrate 10 and the color filter 14 can be separately ensured, the lower flattening layer 12 may not be formed.
Further, an upper flattening layer 13 is formed between the color filter layer 30 and the microlens group composed of the plurality of microlenses 18.

Hereinafter, in the description of the solid-state image sensor according to the present embodiment, the color filter having the widest area formed first in the manufacturing process is defined as the color filter 14 of the first color. Further, the color filter formed second in the manufacturing process is defined as the color filter 15 of the second color, and the color filter formed third in the manufacturing process is defined as the color filter 16 of the third color. The same applies to other embodiments.
In the solid-state image sensor according to the present embodiment, the color filter 14 of the first color contains a thermosetting resin and a photocurable resin. The content of the photocurable resin is less than the content of the thermosetting resin.

Here, the color filter 14 of the first color does not have to be the color filter having the widest area, and may not be the color filter formed first.
Further, in the present embodiment, the color filter layer 30 is illustrated in the case where a plurality of colors are composed of three colors of green, red, and blue and arranged in a Bayer array arrangement pattern, but the color filter layer 30 is composed of four or more colors. It may be.
In the following description, it is assumed that the first color is green, but the first color may be blue or red.
Hereinafter, each part of the solid-state image sensor will be described in detail.

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

(Micro lens)
Each microlens 18 is arranged above the semiconductor substrate 10 so as to correspond to the pixel position. That is, the microlens 18 is provided for each of the plurality of photoelectric conversion elements 11 two-dimensionally arranged on the semiconductor substrate 10. The microlens 18 compensates for the decrease in sensitivity of the photoelectric conversion element 11 by condensing the incident light incident on the microlens 18 on each of the photoelectric conversion elements 11.
The height of the microlens 18 from the lens top to the lens bottom is preferably in the range of 400 nm or more and 800 nm or less.

(Lower flattening layer)
The lower flattening layer 12 is a layer provided for surface protection and flattening of the semiconductor substrate 10. That is, the lower flattening layer 12 reduces the unevenness of the upper surface of the semiconductor substrate 10 due to the fabrication of the photoelectric conversion element 11, and improves the adhesion of the material for the color filter.
In the present embodiment, the lower flattening layer 12 does not exist because the parts other than the lower part of the color filter 14 of the first color are removed by the dry etching step or the like described later.

The lower flattening 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, or the like. It is formed of a resin containing a plurality of resins. Further, the lower flattening layer 12 is not limited to these resins, as long as it is a material that transmits visible light having a wavelength of 400 nm to 700 nm and does not hinder the pattern formation and adhesion of the color filters 14, 15 and 16. Can also be used.

The lower flattening layer 12 is preferably formed of a resin that does not affect the spectral characteristics of the color filters 14, 15 and 16. For example, the lower flattening layer 12 is preferably formed so that the transmittance is 90% or more with respect to visible light having a wavelength of 400 nm to 700 nm.
Here, the lower flattening layer 12 provided below the color filter 14 of the first color may be omitted.
In the present embodiment, the film thickness B [nm] of the lower flattening layer 12 is formed to be 0 [nm] or more and 200 [nm] or less. The film thickness B is preferably 100 [nm] or less, and more preferably 60 [nm] or less. The thinner the film thickness B of the lower flattening layer 12 is, the more preferable it is from the viewpoint of preventing color mixing.

(Upper flattening layer)
The upper flattening layer 13 is a layer provided for flattening the upper surfaces of the color filters 14, 15 and 16.
The upper flattening layer 13 is made of, for example, a resin such as 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, or a styrene resin. It is formed of a resin containing a plurality of resins. The upper flattening layer 13 may be integrated with the microlens 18 without any problem.
The film thickness of the upper flattening layer 13 is, for example, 1 [nm] or more and 300 [nm] or less. It is preferably 100 [nm] or less, more preferably 60 [nm] or less. From the viewpoint of preventing color mixing, the thinner the color, the more preferable.

(Color filter)
The color filters 14, 15 and 16 that form the color filter layer 30 with a predetermined pattern are filters corresponding to each color that color-separates the incident light. The color filters 14, 15 and 16 are provided between the semiconductor substrate 10 and the microlens 18, and are arranged in a predetermined regular pattern corresponding to each of the plurality of photoelectric conversion elements 11 according to the pixel positions. Has been done.
FIG. 2 shows the arrangement of the color filters 14, 15 and 16 of each color in a plane. The arrangement example shown in FIG. 2 is a so-called Bayer arrangement.
The color filters 14, 15 and 16 contain pigments (colorants) of a predetermined color, and a thermosetting component and a photocuring component. For example, the color filter 14 contains a green pigment as a colorant, the color filter 15 contains a blue pigment, and the color filter 16 contains a red pigment.

Although the present embodiment contains a thermosetting resin and a photocurable resin, it is preferable that the amount of the thermosetting resin blended is larger. In this case, for example, the curing component in the solid content is 5% by mass or more and 40% by mass or less, the thermosetting resin is 5% by mass or more and 20% by mass or less, and the photocurable resin is 1% by mass or more and 20% by mass or less. The thermosetting resin is preferably 5% by mass or more and 15% by mass or less, and the photocurable resin is in the range of 1% by mass or more and 10% by mass or less.
Here, when the curing component is only a thermosetting component, the curing component in the solid content is in the range of 5% by mass or more and 40% by mass or less, more preferably 5% by mass or more and 15% by mass or less. On the other hand, when the curing component is only a photocuring component, the curing component in the solid content is in the range of 10% by mass or more and 40% by mass or less, more preferably 10% by mass or more and 20% by mass or less.

In this embodiment, a solid-state image sensor having a Bayer array color filter shown in FIG. 2 will be described. However, the color filter of the solid-state image sensor is not necessarily limited to the Bayer arrangement, and the color of the color filter is not limited to the three colors of RGB. Further, a transparent layer having an adjusted refractive index may be arranged as a part of the array of color filters.
The film thickness A [nm] of the color filter 14 of the first color is formed to be 200 [nm] or more and 700 [nm] or less. Preferably, the film thickness A [nm] is 400 [nm] or more and 600 [nm] or less. More preferably, the film thickness A [nm] is 500 [nm] or less.

Further, when the film thickness of the color filters 15 and 16 of colors other than the first color is C [nm], the film thickness is formed to satisfy the following formula.
A + B-200 [nm] ≤ C ≤ A + B + 200 [nm]
However, the film thickness of the color filter 15 of the second color and the film thickness of the color filter 16 of the third color may be different.
Here, the reason why the film thickness difference between the film thickness of (A + B) and the film thickness of C is 200 [nm] or less is that if there is a part where the film thickness difference exceeds 200 [nm], the other This is because the light receiving sensitivity may decrease due to the influence of the obliquely incident light on the pixels. Further, when a step exceeding 200 [nm] is formed, it may be difficult to form the upper microlens 18.
Further, in order to thin the color filter layer 30, the concentration of the pigment (colorant) contained in each of the first to third color filters is preferably 50% by mass or more.

<Manufacturing method of solid-state image sensor>
Next, a method for manufacturing the solid-state image sensor according to the first embodiment will be described with reference to FIGS. 3 and 4.
(Forming process of lower flattening layer)
As shown in FIG. 3A, a semiconductor substrate 10 having a plurality of photoelectric conversion elements 11 is prepared, and a lower flattening layer 12 is formed on the entire surface of the filter layer forming position on the surface of the semiconductor substrate 10. The lower flattening layer 12 is formed of, for example, a resin containing one or more resin materials such as the above-mentioned acrylic resin, or a compound such as an oxidation compound or a nitride compound.
The lower flattening layer 12 is formed by a method in which a coating liquid containing the above-mentioned resin material is applied, heated and cured. Further, the lower flattening layer 12 may be formed by forming a film of the above-mentioned compound by various methods such as thin film deposition, sputtering, and CVD.

Here, the method for manufacturing a solid-state image sensor according to the present embodiment is manufactured by directly patterning the color filters 14, 15 and 16 constituting the color filter layer 30 by photolithography using a conventional material for a photosensitive color filter. It's different from the way you do it.
That is, in the method for manufacturing a solid-state image sensor according to the present embodiment, after the material for the color filter of the first color is applied to the entire surface and cured to form the color filter layer 14A of the first color (FIG. 3 (FIG. 3). d)), the portion of the first color color filter layer 14A that forms another color filter is removed by dry etching. As a result, the pattern of the color filter 14 of the first color (see FIG. 4B) is formed. Then, the second and subsequent color filters (patterns 15 and 16 of the second and third color filters) are formed in a portion surrounded by the pattern of the first color color filter 14. At this time, the pattern of the first color filter 14 formed earlier is used as a guide pattern, and the second and subsequent color filter materials are cured by high-temperature heat treatment. Therefore, even if the lower flattening layer 12 is not provided under the second and subsequent color filters, the adhesion between the semiconductor substrate 10 and the color filters 15 and 16 can be improved.
Hereinafter, the forming process will be described.

(First color color filter layer forming step (first step))
First, as shown in FIGS. 3 (b) to 3 (d), a step of forming the first color color filter 14 on the surface of the lower flattening layer 12 formed on the semiconductor substrate 10 will be described. As the guide pattern, the color filter 14 of the first color is preferably a color filter having the largest occupied area in the solid-state image sensor.
As shown in FIG. 3B, on the surface of the lower flattening layer 12 formed on the semiconductor substrate 10 in which a plurality of photoelectric conversion elements 11 are two-dimensionally arranged, a first pigment containing a resin material as a main component ( A first color color filter material 14a composed of a first resin dispersion liquid in which a colorant) is dispersed is applied. As shown in FIG. 2, it is assumed that the solid-state image sensor according to the present embodiment uses a Bayer array color filter. Therefore, the first color is preferably green (G).

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

Next, as shown in FIG. 3C, the entire surface of the color filter layer 14A of the first color is irradiated with ultraviolet rays to photocure the color filter layer 14A. In the present embodiment, unlike the case where a desired pattern is directly formed by exposing the color filter material with photosensitivity as in the conventional method, the entire surface of the color filter layer 14A is cured, so that a photosensitive component is obtained. Curing is possible even if the content of is reduced.

Next, as shown in FIG. 3D, the color filter layer 14A of the first color is thermoset at 200 ° C. or higher and 300 ° C. or lower. More specifically, it is preferable to heat at a temperature of 230 ° C. or higher and 270 ° C. or lower. In the manufacture of a solid-state image sensor, a high-temperature heating step of 200 ° C. or higher and 300 ° C. or lower is often used when forming the microlens 18, so it is desirable that the material for the color filter of the first color has high temperature resistance. .. Therefore, it is more preferable to use a thermosetting resin having high temperature resistance as the resin material.

(Etching mask pattern forming process)
Next, as shown in FIGS. 3 (e) to 3 (g), an etching mask pattern having an opening is formed on the color filter layer 14A of the first color formed in the previous step.
First, as shown in FIG. 3E, a photosensitive resin mask material is applied to the surface of the color filter layer 14A of the first color and dried to form the photosensitive resin layer 20.
Next, as shown in FIG. 3 (f), the photosensitive resin layer 20 is exposed to light using a photomask (not shown), and a chemical reaction occurs in which a pattern other than the required pattern becomes soluble in the developing solution. ..
Next, as shown in FIG. 3 (g), an unnecessary portion (exposed portion) of the photosensitive resin layer 20 is removed by development. As a result, the etching mask pattern 20a having the opening 20b is formed. A second color color filter or a third color color filter is formed at the position of the opening 20b in a later step.

As the photosensitive resin material, for example, an acrylic resin, an epoxy resin, a polyimide resin, a phenol novolac resin, or another photosensitive resin can be used alone, in combination of a plurality, or in copolymerization. Examples of the exposure machine used in the photolithography process for patterning the photosensitive resin layer 20 include a scanner, a stepper, an aligner, and a mirror projection aligner. Further, the exposure may be performed by drawing directly with an electron beam, drawing with a laser, or the like. Among them, a stepper or a scanner is generally used to form the color filter 14 of the first color of the solid-state image sensor that needs to be miniaturized.

As the photosensitive resin mask material, it is desirable to use a general photoresist in order to produce a high-resolution and high-precision pattern. By using a photoresist, it is possible to form a pattern with easy shape control and good dimensional accuracy, unlike the case of forming a pattern with a material for a color filter having photosensitivity.

The photoresist used at this time is preferably one having high dry etching resistance. When used as an etching mask material during dry etching, a thermosetting step 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 step is included, it may be difficult to remove the residual resist used as an etching mask in the removing step after dry etching. Therefore, as the photoresist, it is preferable that a selectivity can be obtained with the etching member without using a thermosetting step. Further, when a good selection ratio cannot be obtained, it is necessary to form a thick photoresist material, but if the film thickness is increased, it becomes difficult to form a fine pattern. Therefore, as the photoresist, a material having high dry etching resistance is preferable.

Specifically, the etching rate ratio (selection ratio) of the photosensitive resin mask material which is an etching mask and the material for a color filter of the first color which is the target of dry etching is preferably 0.5 or more, preferably 0.8. The above is more preferable. With this selection ratio, it is possible to etch the color filter 14 without completely eliminating the etching mask pattern 20a. When the film thickness of the material for the color filter of the first color is about 0.3 μm or more and 0.8 μm or less, the film thickness of the photosensitive resin mask layer 20a is preferably about 0.6 μm or more and 2.0 μm or less. ..

The photoresist used at this time may be either a positive resist or a negative resist. However, considering the removal of the photoresist after etching, it is preferable to use a positive resist in which the chemical reaction proceeds and the chemical reaction easily occurs in the melting direction, rather than a negative resist in which the chemical reaction proceeds and changes in the curing direction due to external factors. ..
As described above, the etching mask pattern is formed.

(First color filter forming step)
As shown in FIG. 4A, a part of the first color color filter layer 14A exposed from the opening 20b is removed by dry etching using an etching mask pattern and a dry etching gas.
Examples of the dry etching method include ECR, parallel plate magnetron, DRM, ICP, and dual frequency type RIE (Reactive Ion Etching). The etching method is not particularly limited, but it is a method that can control the etching rate and etching shape so that they do not change even if the line width and area are different, such as a large area pattern with a width of several mm or more and a minute pattern with a width of several hundred nm. Is desirable. Further, it is desirable to use a dry etching method of a control mechanism capable of uniformly dry etching in the entire surface of a wafer having a size of about 100 mm to 450 mm.

The dry etching gas may be a gas having reactivity (oxidizing / reducing), that is, etching. Examples of the reactive gas include gases containing fluorine, oxygen, bromine, sulfur, chlorine and the like. Further, a rare gas containing an element such as argon or helium, which has low reactivity and is etched by a physical impact with ions, can be used alone or in combination. Further, any gas that causes a reaction to form a desired pattern in the dry etching step in a plasma environment using a gas is not limited to these. In the present embodiment, 90% or more of the total gas flow rate is a gas that is mainly etched by the physical impact of ions such as a rare gas in the initial stage, and an etching gas mixed with a fluorine-based gas or an oxygen-based gas is used. As a result, the etching rate is improved by utilizing the chemical reaction.

In the present embodiment, the semiconductor substrate 10 is made of a material mainly composed of silicon. Therefore, as the dry etching gas, it is desirable to use a gas that etches the material for the color filter and does not etch the underlying semiconductor substrate 10. Further, when a gas for etching the semiconductor substrate 10 is used, a gas for etching the semiconductor substrate 10 may be used first, and the semiconductor substrate 10 may be changed to a gas not etched in the middle to perform multi-step etching. The type of etching gas is not limited as long as the semiconductor substrate 10 is not affected, the color filter material can be etched in a shape close to vertical using the etching mask pattern 20a, and a residue of the color filter material is not formed. ..

In the present embodiment, a rare gas containing a less reactive element such as argon or helium is set to 90% or more of the total gas flow rate, and one or more kinds of reactive gas species such as fluorine-based and oxygen-based are mixed. Use dry etching gas. As a result, the etching rate can be improved by using a chemical reaction.
Further, when etching is performed under these etching conditions, the amount of reaction products adhering to the side wall of the etching mask pattern increases, and it becomes difficult to remove the etching mask 20. Therefore, it is desirable to facilitate the removal of the etching mask 20 by changing the dry etching conditions in multiple stages according to the situation.

Specifically, at the initial stage of etching, etching is performed using an etching gas containing a gas having reactivity and having 90% or more of the total gas flow rate of a rare gas having low reactivity. At this time, it is preferable to perform etching of 30% or more and 90% or less, and 50% or more and 80% or less of the initial film thickness of the color filter layer 14A of the first color.
In the next step, a rare gas with low reactivity is set to 80% or less of the total gas flow rate, and a reactive gas such as a fluorine-based gas or an oxygen-based gas or a dry etching gas obtained by mixing a plurality of these is used. Etching is performed.

Next, the first color color filter layer 14A is etched at these gas flow rates within a range in which the semiconductor substrate 10 is not etched. After that, a gas that does not chemically etch Si by removing the fluorine-based gas, for example, a single gas of oxygen or a rare gas, or a gas in which a plurality of these is mixed is used to form the color filter layer 14A of the first color. Etching is performed above the film thickness. Over-etching is performed. By performing over-etching, the influence of in-plane variation in etching of the semiconductor substrate 10 is reduced, the color filter layer 14A of the first color at a desired position is removed on the entire surface of the semiconductor substrate 10, and the first color is removed. It is possible to form the pattern of the color filter 14 of.

Under the above-mentioned conditions, as shown in FIG. 4B, dry etching of the color filter layer 14A of the first color is performed until the surface of the semiconductor substrate 10 is reached, and then the etching mask pattern 20a is removed to obtain the first color. The pattern of the color filter 14 of one color can be formed. In the present embodiment, when a part of the color filter layer 14A of the first color exposed from the opening 20b is removed, the portion of the lower flattening layer 12 located in the opening 20b is etched. Therefore, the lower flattening layer 12 remains only in the lower part of the pattern position of the color filter 14 of the first color.

Depending on the material of the lower flattening layer 12, the etching rate may be slow in the dry etching step described above, and the lower flattening layer 12 at the second and subsequent color filter forming portions may not be completely removed. In that case, the distance from the top of the microlens to the device becomes long, and the effect of thinning the second and subsequent color filters is reduced. Therefore, a further step of removing the lower flattening layer 12 is carried out. Specifically, the removal by long-term etching by increasing the film thickness of the etching mask pattern 20 by using physical etching such as argon, or the wet etching step using a solvent for etching the lower flattening layer 12. It is an implementation. In this case, the upper part of the color filter of the first color is covered with the etching mask pattern 20, but the side surface is exposed because the color filter of the first color is exposed except for the reaction product of the dry etching. An etching solution that does not affect the filter material or has a slight effect is desirable.

Next, the remaining etching mask pattern 20a is removed (see FIG. 4B). Examples of the removal of the etching mask pattern 20a include a removing method of dissolving and peeling the etching mask pattern 20a without affecting the color filter 14 of the first color by using a chemical solution or a solvent. Examples of the solvent for removing the etching mask pattern 20a 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, and propylene glycol monoethyl. A mixed solvent obtained by using an organic solvent such as ether or propylene glycol monomethyl ether acetate alone or a mixture of a plurality of organic solvents is used. Further, it is desirable that the solvent used at this time does not affect the material for the color filter. As long as it does not affect the material for the color filter, there is no problem with the peeling method using an acid-based chemical.

Further, a method for removing the solvent or the like other than the wet process can also be used. The etching mask pattern 20a can be removed by a method using an ashing technique, which is a resist ashing technique using photoexcitation or oxygen plasma. Moreover, these methods can also be used in combination. For example, first, an ashing technique, which is an incineration technique using photoexcitation or oxygen plasma, is used to remove the altered layer by dry etching on the surface layer of the etching mask pattern 20a, and then the remaining layer is removed by wet etching using a solvent or the like. There is a method of removing it. Further, the etching mask 20 may be removed only by ashing as long as the material for the color filter of the first color is not damaged. Further, not only a dry process such as ashing but also a polishing process by CMP or the like may be used.

By the above steps, the patterning formation of the color filter 14 of the first color is completed.
When the first color filter 14 is applied to the entire surface of the semiconductor substrate 10, it is photocured and thermoset on the entire surface as shown in FIGS. 3 (b) and 3 (c). A further curing step may be used to perform the cleaning step. For example, a high-temperature heating step at 200 ° C. or higher and 300 ° C. or lower, or photocuring by exposure.

(About the second and subsequent color filter pattern forming steps (second step))
Next, as shown in FIG. 5, the second and third color filters 15 and 16 containing pigments having a color different from that of the first color filter 14 are formed. The methods for producing the patterns of the second and third color filters 15 and 16 can be roughly divided into two methods.
In the first method, the pattern of the color filter 14 of the first color is used as a guide pattern, and the materials for the photosensitive color filter containing the photocurable resin in the color filters 15 and 16 of the second and third colors. It is a method of forming a pattern by selectively exposing it by a conventional method.

In the second method, the material for the second color filter is applied to the entire surface of the opening 20b formed by the patterned first color color filter 14. Subsequently, dry etching is performed using the patterned photosensitive resin mask material layer as an etching mask, and an opening is provided at a position where the color filter 16 of the third color is formed. Finally, a material for a third color filter is applied to the location of the opening, and the excess color filter is removed by polishing or the like to form the third color filter 16 in the opening. It is a method.

(First method for forming the pattern of the second and subsequent color filters)
First, the first method of forming the pattern of the second and subsequent color filters will be described with reference to FIG. The first method is characterized in that a color filter material (color resist) having a photosensitive component is used for the color filter 15 of the second color.
First, as shown in FIG. 5A, a photosensitive color filter material is applied as a second color filter material to the entire surface of the semiconductor substrate 10 on which the first color color filter 14 is patterned. That is, it is applied to the entire surface of the opening 20b and dried to form a second color color filter layer 15A. The material for the photosensitive color filter used at this time contains a negative type photosensitive component that is cured by being exposed to light.

At this time, the film thickness of the first color filter 14 is A [nm], the film thickness of the lower flattening layer 12 is B [nm], and the film thickness of the second color filter 15 is C1 [nm]. In this case, the film thickness C1 of the color filter 15 of the second color is set so as to satisfy the following equations (1) to (3a).
200 [nm] ≤ A ≤ 700 [nm] ... (1)
0 [nm] <B ≦ 200 [nm] ・ ・ ・ (2)
A + B-200 [nm] ≤ C1 ≤ A + B + 200 ... (3a)
Although the case of A + B = C1 is illustrated in FIG. 5, the film thickness C1 may be within the range of (A + B) ± 200 [nm] as in the equation (3a).
As the color filter 15 of the second color, if it is in the range of this film thickness C1, it is dispersed as a pigment concentration that can obtain desired spectral characteristics while containing a thermosetting resin and a photocurable resin sufficient for curing. be able to.

Next, as shown in FIG. 5B, the portion forming the second color color filter 15 is exposed using a photomask, and a part of the second color color filter layer 15A is exposed. Is photocured.
Next, as shown in FIG. 5C, a part 15Aa (position of forming the color filter of the third color) of the color filter layer 15 of the second color that has not been selectively exposed in the developing process is removed. The opening 31 is formed. Next, in order to improve the adhesion between a part of the exposed second color color filter layer 15A and the semiconductor substrate 10 as shown in FIG. 5D, and to improve the heat resistance in actual device use. The remaining second color filter 15 is cured by performing the curing treatment by heating at a high temperature. As a result, the pattern of the color filter 15 of the second color is formed. At this time, the temperature used for curing is preferably 200 ° C. or higher.

Next, as shown in FIG. 5E, the material for the color filter of the third color is applied to the entire surface of the semiconductor substrate 10, that is, the entire surface of the opening formed in the color filter 15 of the second color is applied. Therefore, the color filter layer 16A of the third color is formed.
Next, as shown in FIG. 5 (f), the portion of the third color color filter layer 16A that forms the third color color filter 16 is selectively exposed and is located at the opening 30. The color filter layer 16A of the third color is photocured.
Next, as shown in FIG. 5 (g), the photosensitive third color color filter layer 16A is developed, and a part of the unexposed third color color filter layer 16A is removed. Next, as shown in FIG. 5 (h), in order to improve the adhesion between a part of the exposed third color color filter layer 16A and the semiconductor substrate 10 and the heat resistance in actual device use. The remaining third color color filter layer 16A is cured by performing the curing treatment by heating at a high temperature. As a result, the color filter 16 of the third color is formed.
By repeating the pattern forming steps of the second color filter 15 and subsequent steps, a color filter having a desired number of colors can be formed.

At this time, when the film thickness of the color filter 16 of the third color is C2 [nm], the film of the color filter 16 of the second color is satisfied so as to satisfy the following equations (1) to (3b). Set the thickness C2.
200 [nm] ≤ A ≤ 700 [nm] ... (1)
0 [nm] <B ≦ 200 [nm] ・ ・ ・ (2)
A + B-200 [nm] ≤ C2 ≤ A + B + 200 ... (3b)
Although the case of A + B = C2 is illustrated in FIG. 5, the film thickness C2 may be within the range of (A + B) ± 200 [nm] as in the equation (3b).
As the color filter 16 of the third color, if it is within the range of this film thickness C2, it is dispersed as a pigment concentration that can obtain the desired spectral characteristics while containing a thermosetting resin and a photocurable resin sufficient for curing. Can be done.
By the above steps, the heights of the second color filter 15 and the third color filter 16 are equivalent to the sum of the thicknesses of the first color filter 14 and the lower flattening layer 12. At height, a color filter is formed.

Next, as shown in FIG. 6A, the upper flattening layer 13 is formed on the formed color filters 14, 15 and 16. The upper flattening layer 13 can be formed by using a resin containing one or more resin materials such as the above-mentioned acrylic resin. In this case, the upper flattening layer 13 can be formed by applying a resin material to the surface of the semiconductor substrate 10 and heating to cure the upper layer flattening layer 13. Further, the upper flattening layer 13 can be formed by using, for example, a compound such as the above-mentioned oxide or nitride. In this case, the upper flattening layer 13 can be formed by various film forming methods such as vapor deposition, sputtering, and CVD.

Finally, as shown in FIG. 6B, the microlens 18 is formed on the upper flattening layer 13. The microlens 18 is formed by a known technique such as a fabrication method using heat flow, a macrolens fabrication method using a gray tone mask, and a microlens transfer method to the upper flattening layer 13 using dry etching.
The film thickness of the upper flattening layer 13 is, for example, 1 [nm] or more and 300 [nm] or less. It is preferably 100 [nm] or less, more preferably 60 [nm] or less.

As a method of forming a microlens by using a patterning technique by dry etching having excellent shape controllability, as shown in FIG. 7A, first, a transparent resin layer 32 (upper layer flattening layer 13) finally to be a microlens is formed. (It may also serve as) is formed on the color filter.
Next, as shown in FIG. 7B, a master mold 33 (lens master mold) of the microlens is formed on the transparent resin layer 32 by a heat flow method. Next, as shown in FIG. 7C, the lens matrix 33 is used as a mask, and the lens matrix shape is transferred to the transparent resin layer 32 by a dry etching method. By selecting the height and material of the lens base 33 and adjusting the etching conditions, an appropriate lens shape can be transferred to the transparent resin layer 32.
By using the above method, it is possible to form a microlens with good controllability. It is desirable to use this technique to prepare a microlens so that the height from the lens top to the lens bottom of the microlens is 400 to 800 nm.
Through the above steps, the solid-state image sensor of the present embodiment is completed.

In the present embodiment, it is preferable that the color filter 14 of the first color is a color filter having the largest occupied area. Then, the second color color filter 15 and the third color color filter 16 are each formed by photolithography using a color resist having photosensitivity.
The technique of using a photosensitive color resist is a conventional technique for manufacturing a color filter pattern. Since the material for the color filter of the first color is applied to the entire surface of the lower flattening layer 12 and then heated at a high temperature, the adhesion to the semiconductor substrate 10 and the lower flattening layer 12 can be made very strong. Therefore, using the pattern of the color filter 14 of the first color, which has good adhesion and is formed with good rectangularity, as a guide pattern, the colors of the second and third colors so as to fill the place surrounded by the four sides. Filters 15 and 16 can be formed. Therefore, even when a color resist having photosensitivity is used for the second and subsequent color filters, it is not necessary to use a color resist that emphasizes resolution as in the conventional case. Therefore, since the photocurable component in the photocurable resin can be reduced, the proportion of the pigment in the color filter material can be increased, and the color filters 15 and 16 can be thinned.

At the locations where the second and subsequent color filters are formed, the lower flattening layer 12 is removed in the etching process during etching of the first color filter 14, and the semiconductor substrate 10 is exposed to the surface. There is. In this case, it is considered that the surface of the semiconductor substrate 10 is oxidized and becomes hydrophilic. When the second and subsequent color filters are formed on the surface of the semiconductor substrate 10 by a photolithography step, the developing solution wraps around the portion where the hydrophilic semiconductor substrate 10 and the second and subsequent color filters are in contact with each other. .. Therefore, it is assumed that the second and subsequent color filters (color filters 15 and 16 of the second and third colors) are peeled off. Therefore, depending on the surface condition of the semiconductor substrate 10, the surface of the semiconductor substrate 10 exposed by an existing method such as HDMS (hexamethyldisilazane) treatment may be made hydrophobic so that the second and subsequent colors can be obtained. The possibility of the filter peeling off can be reduced.

Further, in the present embodiment, it is desirable that the color filter 14 of the first color is formed of a material for a color filter having a low content of resin components and the like involved in photocuring and a high pigment content. In particular, it is desirable that the content of the pigment in the material for the first color filter is 70% by mass or more. As a result, even if the material for the color filter of the first color contains a pigment having a density that is insufficiently cured by the photolithography process using the conventional photosensitive color resist, the color of the first color The filter 14 can be formed with high accuracy and without residue or peeling. Specifically, when a green filter is used as the color filter 14 of the first color, the photocuring component of the red filter or the blue filter can be reduced. Therefore, even if the pigment content is high, each color filter pattern can be easily formed by photolithography.

For any reason, the first color filter 14 of the first color is mainly cured with a thermosetting component while focusing on photocuring rather than pattern formation to reduce the photosensitive component. It is formed by using a material for a color filter of a color. By doing so, the color filter 14 of the first color adheres to the semiconductor substrate 10 and the lower flattening layer 12, and there is no residue or peeling that occurs when the other color filters are formed, and high resolution can be obtained. The second and third color filters 15 and 16 are formed by a photolithography forming method that requires less steps and is efficient, using photosensitive materials for the second and third color filters. To. By doing so, the pattern of the first color filter 14 formed first becomes an accurate pattern guide, and the patterns of the second and third color color filters 15 and 16 are formed in good shape by photolithography. be able to.

(Second method for forming the pattern of the second and subsequent color filters)
Next, a second method for forming the second and subsequent color filter patterns will be described with reference to FIGS. 8 and 9. The second method is a case where the color filters 15 and 16 of the second and third colors are formed from a material for a color filter that does not have photosensitivity.
The method will be described below.
As shown in FIG. 8 (b), for the color filter of the second color, as shown in FIG. 8 (b), the entire surface of the substrate 10 on which the color filter 14 of the first color is formed is formed by the above-described forming method shown in FIG. 8 (a). Apply the material. As the material for the color filter of the second color used at this time, a thermosetting resin material that does not have photosensitivity and is cured by heating is used. Since the material for the color filter of the second color does not have photosensitivity, as described above, it is not necessary to add a photosensitive component, and the pigment concentration can be increased. Therefore, the film thickness of the second color filter 15 can be reduced. After that, in order to cure the material for the second color color filter to form the second color color filter layer 15A, heating is performed at a high temperature. The heating temperature is preferably heating within a range that does not affect the device, specifically 300 ° C. or lower, and more preferably 240 ° C. or lower.

At this time, as shown in FIG. 8B, in order to make the film thickness of the second color color filter layer 15A uniform, it is necessary to apply a large amount of the second color color filter material. Therefore, the material for the color filter of the second color is extra formed on the color filter 14 of the first color. In order to remove the excess color filter of the second color, a polishing step such as CMP or an etching back step is performed using a dry etching technique. The material for the color filter of the second color can be removed by a process using a known technique such as flattening or removing a desired film thickness. Further, if the step of removing the excess second color color filter layer 15A does not pose a problem in the etching step of opening the forming portion of the third color color filter 16 described later, the plurality of color color filters 14 , 15 and 16 may be formed at the end.

Next, as shown in FIG. 8C, a photosensitive resin mask material is applied to the upper portion of the color filter layer 15A of the second color to form the photosensitive resin mask layer 35.
Subsequently, as shown in FIGS. 8 (d) and 8 (e), the etching mask 20 is exposed and developed so that the place where the color filter 16 of the third color is arranged is opened, and the etching mask 20 is provided with the opening 20c. Form.
Subsequently, as shown in FIG. 8 (f), a third color is used in the region of the color filter layer 15A of the second color by using a dry etching technique using an etching mask 20 provided with an opening. The portion unnecessary for arranging the color filter 16 of the above is removed to form the opening 20d. At this time, the etching mask 20 may be subjected to a curing treatment such as heating or irradiation with ultraviolet rays.
Next, as shown in FIG. 8 (g), the etching mask 20 is removed by a known removing method such as peeling with a solvent, cleaning, photoexcitation, or ashing, which is an ashing treatment with oxygen plasma. As a result, an opening is provided at a position where the third color color filter 16 is formed, and a first color color filter 14 and a second color color filter 15 are formed at other positions. It is in a state of being.

Next, as shown in FIG. 9A, a third so as to fill the opening 20d with respect to the entire surface of the substrate 10 on which the first color color filter 14 and the second color color filter 15 are formed. The material for the color filter of the above color is applied and heat-cured to form the color filter layer 16A of the third color. After that, as shown in FIG. 9B, the extra third color color filter layer 16 on the first and second color color filters 14 and 15 is polished to a predetermined film thickness by CMP or the like. A third color filter 16 is obtained by performing an etch back step using a step or a dry etching technique and removing the result by a step using a known technique such as flattening or removing a desired film thickness. At this time, if the second color color filter 15 that is excessively formed on the first color color filter remains, there is no problem even if it is removed at the same time.

Here, when the color of the color filter is set to four or more colors and the fourth and subsequent color filters are formed, the material for the color filter is applied and cured in the same manner as the color filters 15 and 16 of the second and third colors. Just do. After that, it is possible to form a color filter of a plurality of colors by performing dry etching using the photosensitive resin material having the openings provided by patterning as an etching mask and removing the excess photosensitive resin mask layer 20a. it can.
The solid-state image sensor of the present embodiment is completed by performing the upper flattening layer 13 and the microlens forming method on the formed color filter material of a plurality of colors by the above-mentioned treatment.

The first method described above is a method of forming the color filters of the second color after the color filter 15 by photolithography. In the first method, the material for the color filter after the second color color filter 15 is given photocurability, and is selectively exposed and developed to form the second color color filter 15 and later. There is.
Further, the second method described above is a forming method in which dry etching is repeated a plurality of times. In the second method, the color filter material of the second color after the color filter 15 has a thermosetting component without having a photosensitive component, and is applied to the entire surface to perform thermosetting. Then, the photosensitive mask material is formed as an etching mask on the first and second color filters 14 and 15 to be retained, and the second color filter 15 and subsequent colors are also produced by dry etching. In these two methods, the color filters of the second and third colors are formed by repeating the same steps, but if the desired spectral characteristics can be obtained, these steps can be used in combination. good.

In this embodiment, both a thermosetting resin and a photocurable resin are used for the color filter 14 of the first color. Further, in the curing step of the color filter 14 of the first color, photocuring by exposure and heat curing by heat are used. In order to make the color filter layer 30 thin, it is necessary to increase the pigment concentration, but if the pigment content is high, the solvent resistance tends to decrease. Therefore, when it comes into contact with a solvent in the developing process, the etching mask removing process, the application of the second and subsequent color filters, the developing process, etc., the components of the color filter 14 of the first color dissolve out, which affects the spectral characteristics. It is possible to give. By mixing and exposing a photosensitive photocurable component resin, the surface of the color filter is cured, and by mixing a thermosetting resin and heat-curing at a high temperature, the inside and surface of the color filter are cured. It has the effect of improving solvent resistance.
As described above, according to the present embodiment, it is possible to reduce the total film thickness of each color filter and shorten the total distance from the microlens top to the device, so that color mixing can be reduced and all patterns are arranged. It is possible to provide a high-definition solid-state image sensor with high sensitivity by the color filter of.

"Second embodiment"
Hereinafter, a method for manufacturing the solid-state image sensor and the solid-state image sensor according to the second embodiment of the present invention will be described with reference to FIG. The solid-state image sensor according to the second embodiment of the present invention has the same structure as the first embodiment.
In the second embodiment, since the steps at the time of curing the first color filter are different, the curing step of the first color filter is shown.

<Structure of solid-state image sensor>
The solid-state image sensor according to the present embodiment is characterized in that the color filter material of the first color does not contain a photosensitive resin material and is formed only of a thermosetting resin. Since only the thermosetting resin is used, the pigment concentration can be improved, and there is an advantage that the color filter of the first color can be easily thinned.
As shown in FIG. 1, the solid-state image pickup device according to the present embodiment includes a semiconductor substrate 10 having a plurality of two-dimensionally arranged photoelectric conversion elements 11 and a microlens 18. Further, the solid-state image sensor according to the present embodiment is provided on the color filter layer 30 including the color filters 14, 15 and 16 of a plurality of colors provided between the semiconductor substrate 10 and the microlens 18, and on the semiconductor substrate 10. It includes a partially provided lower flattening layer 12 and an upper flattening layer 13 provided on the surface of the color filter layer 30.

Here, when the solid-state image sensor according to the second embodiment has the same configuration as each part of the solid-state image sensor according to the first embodiment, the same reference as the reference code used in the first embodiment is used. It shall be signed. That is, each of the semiconductor substrate 10 having the photoelectric conversion element 11, the lower flattening layer 12, the color filters 14, 15, 16 and the upper flattening layer 13 and the microlens 18 is the solid-state image sensor according to the first embodiment. It has the same structure as each part. Therefore, detailed description of the parts common to each part of the solid-state image sensor according to the first embodiment will be omitted. The same applies to other embodiments.

<Manufacturing method of solid-state image sensor>
Next, a method of manufacturing the solid-state image sensor of the present embodiment will be described with reference to FIG.
As shown in FIG. 10A, a lower flattening layer 12 is formed on a semiconductor substrate 10 having a plurality of photoelectric conversion elements 11 arranged two-dimensionally. The lower flattening layer 12 has the effect of improving the adhesion of the color filter.
Next, as shown in FIGS. 10 (b) to 10 (d), the color filter layer 14A of the first color is formed, and the photosensitive resin mask layer 20 is formed on the color filter layer 14A. The color filter layer 14A of the first color shown in the present embodiment contains a thermosetting resin and does not contain a photocurable resin. Further, when the pigment content is improved, the solvent resistance of the color filter may decrease as described above. Therefore, a solvent-resistant thermosetting resin is used for high-temperature heating to carry out heat curing with a high crosslink density. Specifically, it is a high-temperature curing step of 230 ° C. or higher, and a high-temperature curing step of 250 ° C. or higher, which is applied in a subsequent step of the device, is more desirable. The photosensitive resin mask layer 20 is formed on the color filter layer 14A of the first color formed in this high-temperature heating step.

Next, using a photomask, the etching mask 20 having openings is formed by exposing and developing so that the color filter forming portions of the second and third colors are opened. The subsequent steps are the same as the steps of the first embodiment described above.
According to this embodiment, since the color filter 14 of the first color does not contain a photosensitive component and only a thermosetting component, there is an advantage that the pigment concentration can be easily increased. Further, by raising the thermosetting temperature, the solvent resistance of the color filter 14 of the first color can be improved.
The invention according to the second embodiment has the following effects in addition to the effects described in the first embodiment. By forming the color filter 14 of the first color with a thermosetting resin which is a thermosetting component, it becomes easy to increase the concentration of the pigment component, and it becomes possible to form a desired spectral characteristic with a thin film.

"Third embodiment"
Hereinafter, a method for manufacturing the solid-state image sensor and the solid-state image sensor according to the third embodiment of the present invention will be described with reference to FIG.
<Structure of solid-state image sensor>
The solid-state image sensor according to the present embodiment is characterized in that the color filter material of the first color is composed of only a photosensitive resin as a curing component. The configuration including the photosensitive resin material is the same as the step of forming a color filter by photolithography using a color resist imparted with photosensitivity in the conventional method. However, in the present embodiment, although a photosensitive resin is used, patterning as in the conventional case is not performed, and photocuring is performed by exposing the entire surface, and then the water content of the color filter is evaporated by high temperature heating to perform heat curing. Therefore, as compared with the conventional method, the amount of the photosensitive curing component can be reduced and the pigment concentration can be improved, so that there is an advantage that the color filter 14 of the first color can be easily thinned.
The structure of the solid-state image sensor according to the present embodiment is the same as that of the first and second images. However, the process at the time of curing of the color filter 14 of the first color is different. Therefore, the curing step and the patterning step of the color filter 14 of the first color are shown.

<Manufacturing method of solid-state image sensor>
Next, a method of manufacturing the solid-state image sensor of the present embodiment will be described with reference to FIG.
The lower flattening layer 12 is formed on the surface of the semiconductor substrate 10 shown in FIG. 11A.
Next, as shown in FIG. 11B, a color filter layer 14A of the first color is formed on the lower flattening layer 12 by coating.
Next, as shown in FIG. 11C, the entire surface is exposed and the color filter layer 14A of the first color is cured by photocuring.
At this time, when the photosensitive component in an amount sufficient for curing the color filter layer 14A of the first color is contained and the solvent resistance is sufficient, the photosensitive resin mask material 40 shown in FIG. 12 is formed. To do. After patterning the photosensitive resin mask material 40, the second and subsequent color filter forming portions are formed by dry etching, and then high-temperature heating is performed, whereby the first color color filter 14 can be heat-cured. ..

On the other hand, when the color filter layer 14A of the first color contains a photosensitive component having an insufficient solvent resistance, a high-temperature heating step of 200 ° C. or higher is performed as shown in FIG. 11 (d). It is desirable that the color filter layer 14A of the first color is sufficiently cured. When the former high-temperature heating step is not carried out, the structure of the color filter layer 14A of the first color is softer than that when the high-temperature heating step is carried out, so that etching can be easily performed in the dry etching step, and residues and the like can be generated. It has the effect of reducing the possibility of remaining.

Subsequent steps are the same as the steps described in the first embodiment described above.
According to the present embodiment, the color filter 14 of the first color is formed by containing only a sufficient amount of photosensitive components for photocuring, instead of forming a pattern. Therefore, the photosensitive components of the color filter material according to the conventional method are formed. Since it is only reduced, it has an advantage that it can be easily produced, and it has an advantage that the pigment content can be easily increased. Further, by raising the thermosetting temperature, the solvent resistance of the color filter 14 of the first color can be improved.

Hereinafter, the solid-state image sensor and the solid-state image sensor of the present invention will be specifically described with reference to Examples.
<Example 1>
A coating liquid containing an acrylic resin is spin-coated on a semiconductor substrate having a two-dimensionally arranged photoelectric conversion element at a rotation speed of 2000 rpm, and heat-treated at 200 ° C. for 20 minutes on a hot plate to cure the resin. did. As a result, a lower flattening layer was formed on the semiconductor substrate. At this time, the layer thickness of the lower flattening layer was 60 nm.
Next, as a material for a color filter of a first color containing a green pigment, which is the first color, a green pigment dispersion liquid containing a photosensitive curable resin and a thermosetting resin was spin-coated at a rotation speed of 1000 rpm. For the green pigment of the material for the first color filter, C.I. I. PG58 was used, the pigment concentration was 70% by mass, and the layer thickness was 500 nm.

Next, in order to cure the color filter material of the first color, the entire surface was exposed using a stepper which is an i-line exposure device, and the photosensitive component was cured. By curing this photosensitive component, the surface of the color filter was cured. Subsequently, the green filter layer was heat-cured by baking at 230 ° C. for 6 minutes.
Next, a positive resist (OFPR-800: manufactured by Tokyo Ohka Kogyo Co., Ltd.) was spin-coated using a spin coater at a rotation speed of 1000 rpm, and then prebaked at 90 ° C. for 1 minute. As a result, a sample was prepared by applying a photoresist having a photosensitive resin mask material layer with a film thickness of 1.5 μm.
The positive resist, which is the photosensitive resin mask material layer, undergoes a chemical reaction when irradiated with ultraviolet rays and dissolves in the developing solution.
This sample was subjected to photolithography in which it was exposed through a photomask. As the exposure device, an exposure device using an i-line wavelength as a light source was used.

Next, a developing step was carried out using 2.38% by mass of TMAH (tetramethylammonium hydride) as a developing solution to form an etching mask having an opening at a place where the second and third color filters were formed. When a positive resist is used, dehydration baking is often performed after development to cure the photoresist, which is a photosensitive resin mask material layer. However, this time, the baking step was not performed in order to facilitate the removal of the etching mask after dry etching. Therefore, the resist cannot be cured and the selection ratio cannot be expected to be improved. Therefore, the film thickness of the resist is 1.5 μm, which is more than twice the film thickness of the first color filter which is the green filter. Formed with. The opening pattern at this time was 1.1 μm × 1.1 μm.

Next, dry etching was performed using the formed etching mask. At this time, the dry etching apparatus used was a parallel plate type dry etching apparatus. In addition, the etching conditions were changed on the way so as not to affect the underlying semiconductor substrate, and dry etching was performed in multiple stages.
First, as the gas type, CF ₄ , O ₂ , and Ar gas were mixed and etched. The gas flow rates of CF ₄ and O ₂ were set to 5 ml / min, respectively, and the gas flow rate of Ar was set to 200 ml / min. That is, the gas flow rate of Ar was 95.2% of the total gas flow rate. Further, the pressure in the chamber at this time was set to 1 Pa, and the RF power was set to 500 W. Using this condition, the etching condition was changed to the next etching condition at the stage of etching to about 350 nm, which is 70% of the total film thickness of the green filter layer of 500 nm.

Next, CF ₄ , O ₂ , and Ar gas were mixed and etched. The gas flow rates of CF ₄ and O ₂ were set to 25 ml / min, respectively, and the gas flow rate of Ar was set to 50 ml / min. That is, the gas flow rate of Ar was 50% of the total gas flow rate. Further, the pressure in the chamber at this time was set to a pressure of 5 Pa, and the RF power was set to 300 W. Under this condition, etching was performed so that the reaction products adhering to the side surface of the photoresist, which is an etching mask, could be removed. Under these conditions, etching was performed up to about 450 nm, which is 90% of the total film thickness of 500 nm of the color filter layer of the first green color. The etching amount in the second step is about 100 nm. Since _{the gas flow rates of CF 4} and O ₂ were increased, the etching rate was about 5 nm / sec, and the process proceeded very quickly.

Next, using a single Ar gas, etching was performed under the conditions that the gas flow rate of Ar was 200 ml / min, the pressure in the chamber was 1.5 Pa, and the RF power was 400 W. By etching under these conditions, the remaining portion of the green filter layer is etched, and at the same time, the lower flattening layer is etched. In the etching under the condition of Ar single gas, the physical impact by ions is the main reaction, so that the residue remaining without being etched can be effectively removed by the chemical reaction of the green filter. Further, this etching condition also has the purpose of adjusting the difference in the etching rate in the plane of the etching sample, and the etching is performed so that the over-etching amount is 10%. In other words, the film thickness of 550 nm, which is 110% of the total film thickness of 500 nm of the green color filter material, is etched under three stages.

Next, etching was performed using a single O2 gas under the conditions of an O2 gas flow rate of 100 ml / min, a chamber pressure of 15 Pa, and an RF power of 150 W. Under this condition, the top surface of the etching mask, which was damaged and deteriorated, was removed, and the residue of the green color filter material that could not be removed by the Ar single gas remaining on the bottom surface was etched.
Next, the photosensitive resin mask material used as the etching mask was removed. The method used at this time was a method using a solvent, and the resist was removed by a spray cleaning device using a stripping solution 104 (manufactured by Tokyo Ohka Kogyo Co., Ltd.).

(Making a color filter for the second color)
Next, a second color filter forming step was performed. At the locations where the second and third color filters are formed, the semiconductor substrate 10 is exposed because the lower flattening layer 12 is removed in the first color filter forming step. Since the surface of the semiconductor substrate 10 is _{formed with a surface protective layer such as SiO 2} , the surface is hydrophilic, and there is a possibility that the color filter of the second color may be peeled off due to the wraparound of the developing solution in the developing process. Can be considered. Therefore, in order to make the exposed semiconductor substrate 10 hydrophobic, HMDS treatment was performed.

Next, a photosensitive second color color filter material containing pigment-dispersed blue was applied to the entire surface of the semiconductor substrate so as to provide a second color color filter.
Next, photolithography was used to selectively expose the photosensitive material for the second color color filter.
Next, a photosensitive color filter material was developed to form a blue filter. At this time, the pigments used as the materials for the photosensitive color filter of the blue resist were described in C.I. I. PB156, C.I. I. It was PV23, and the pigment concentration was 50% by mass. The layer thickness of the blue color filter was 0.56 μm. Further, as the resin which is the main component of the blue resist, an acrylic resin having photosensitivity was used.

Next, in order to firmly cure the photosensitive material for the second color color filter, which is the second color color filter (blue filter), the material was placed in an oven at 230 degrees for 30 minutes for curing. After this heating step, no peeling or pattern collapse was confirmed even after passing through steps such as a third color filter forming step. The color filter of the second color is covered with a color filter of the first color having a good rectangular shape, and is formed with a good rectangular shape, so that it can be cured with good adhesion between the bottom surface and the surroundings. confirmed.

(Making a color filter for the third color)
Next, a photosensitive third color color filter material containing pigment-dispersed red was applied to the entire surface of the semiconductor substrate.
Next, the photomask pattern was selectively exposed to the photosensitive material for the color filter of the third color by photolithography.
Next, a photosensitive third color color filter material was developed to form a red third color color filter.
At this time, the pigments used for the red resist were each according to the color index of C.I. I. PR254, C.I. I. It was PY139, and the pigment concentration was 60% by mass. The layer thickness of the color filter of the third color was 0.56 μm.

Next, in order to firmly cure the photosensitive material for the third color of red, which is the color filter of the third color, the material was placed in an oven at 230 ° C. for 20 minutes to cure. At this time, the color filter of the third color is covered with the color filter of the first color having good rectangularity, and is formed with good rectangularness, so that the adhesion between the bottom surface and the surroundings is good. It was confirmed that it hardened.
By the above steps, the film thickness A (500 nm) of the color filter of the first color composed of green, the film thickness B (60 nm) of the flattening layer below it, and the second and third colors composed of blue and red. The film thickness C (560 nm) of the color filter of No. 1 is based on the present invention.

Next, a coating liquid containing an acrylic resin was spin-coated on the color filter formed by the above flow at a rotation speed of 1000 rpm, and heat-treated at 200 ° C. for 30 minutes on a hot plate to cure the resin. An upper flattening layer was formed.
Finally, a microlens having a height from the lens top to the lens bottom of 500 nm is formed on the upper flattening layer by using the transfer method by etchback, which is a known technique described above, and solid-state imaging of Example 1 is performed. The element was completed.

In the solid-state image sensor obtained as described above, a thin lower flattening layer is formed under the first color filter, and the second and third color filters are formed on the semiconductor substrate. .. Further, since the green filter, which is the first color, uses a thermosetting resin and a small amount of a photosensitive curable resin, the concentration of the pigment in the solid content can be increased, and the color filter can be formed thin. Further, blue and red, which are the color filters of the second and third colors, use photosensitive resins. Therefore, the solid-state image sensor has a small distance to the semiconductor substrate under the microlens and has good sensitivity.

Further, the color filter material of the first color filter composed of the green filter hardens the inside by thermosetting, and further hardens the surface by exposure using a small amount of photosensitive resin, so that the solvent resistance is improved. ing. When a green filter material having a high pigment content is used, the spectral characteristics may change by reacting with a solvent or another color filter material. Therefore, by using the above-mentioned thermosetting and photo-curing together, the hardness can be improved and there is an effect of suppressing the change in the spectral characteristics.

<Example 2>
The second embodiment is an embodiment corresponding to the solid-state image sensor having the configuration described in the second embodiment.
The solid-state image sensor of Example 2 has a configuration in which only a thermosetting resin is used as the color filter material of the first color without using a photocurable resin. Since it is only a thermosetting resin, the pigment concentration can be increased and it can be formed into a thin film.

(Formation of lower flattening layer)
A coating liquid containing an acrylic resin was spin-coated on the semiconductor substrate at a rotation speed of 2000 rpm, and heat-treated at 200 ° C. for 20 minutes on a hot plate to cure the resin and form a lower flattening layer. At this time, the layer thickness of the lower flattening layer was 60 nm.

(Formation of color filter for the first color)
As a material for the color filter of the first color color filter (green filter), a green pigment dispersion liquid containing a thermosetting resin and not containing a photosensitive resin was prepared. This green pigment dispersion was spin-coated on the surface of the lower flattening layer at a rotation speed of 1000 rpm. A thermosetting acrylic resin was used as the main component of the green pigment dispersion. Further, for the green pigment contained in the green pigment dispersion liquid, C.I. I. PG58 was used, and the green pigment concentration in the green pigment dispersion was 70% by mass. The coating thickness of the green color filter material was 500 nm.
Next, the green color filter was baked at 250 ° C. for 6 minutes to cure the green color filter material to form a green filter layer. By performing high temperature baking at 250 ° C., the crosslink density of the thermosetting resin was improved, and the green pigment was cured more firmly.

(Formation of color filter for the first color)
The photosensitive resin mask material was patterned by the method shown in Example 1 to form an etching mask.
First, as the gas type, CF ₄ , O ₂ , and Ar gas were mixed and etched. The gas flow rates of CF ₄ and O ₂ were set to 5 ml / min, and the gas flow rate of Ar was set to 200 ml / min. Further, the etching was performed with the pressure in the chamber at the time of etching set to 1 Pa and the RF power set to 500 W. Using this condition, the etching condition was changed to the next etching condition at the stage of etching to about 350 nm, which is 70% of the total film thickness of 500 nm of the green color filter material.

Next, etching was performed using an etching gas in which three types of _{CF 4} , O _{2, and Ar gas were mixed.} At this time, _{the gas flow rates of CF 4} and O ₂ were set to 25 ml / min, respectively, and the gas flow rate of Ar was set to 50 ml / min. At this time, etching was performed with the pressure in the chamber set to 5 Pa and the RF power set to 300 W. Under this condition, etching was performed so that the reaction products adhering to the side surface of the photoresist, which is an etching mask, could be removed. Under these conditions, etching was performed to about 450 nm, which is 90% of the total film thickness of 500 nm of the color filter layer (green filter) of the first color. The etching amount in the second step was about 100 nm. Since _{the gas flow rates of CF 4} and O ₂ were increased, the etching rate was about 5 nm / sec, and the process proceeded very quickly.

Next, using a single Ar gas, etching was performed under the conditions that the gas flow rate of Ar was 200 ml / min, the pressure in the chamber was 1.5 Pa, and the RF power was 400 W. By etching under these conditions, the residual portion of the green color filter material was etched, and at the same time, the lower flattening layer was etched. In the etching under the condition of Ar single gas, the physical impact by ions is the main reaction, so that the residue remaining without being etched can be effectively removed by the chemical reaction of the green filter.

Further, this etching condition also has the purpose of adjusting the difference in the etching rate in the plane of the etching sample, and the etching is performed so that the over-etching amount is 10%. In other words, the film thickness of 550 nm, which is 110% of the total film thickness of 500 nm of the green filter material, is etched under three-step conditions.
Next, using an _{O 2} single gas, _{O 2} gas flow rate of 100 ml / min, 15 Pa the chamber pressure, the RF power was etched under the conditions of 150 W. Under this condition, the top surface of the etching mask, which was damaged and deteriorated, was removed, and the residue of the green filter layer, which could not be removed by the Ar single gas remaining on the bottom surface, was etched.
Next, the photosensitive resin mask material used as the etching mask was removed. The method used at this time was a method using a solvent, and the resist was removed by a spray cleaning device using a stripping solution 104 (manufactured by Tokyo Ohka Kogyo Co., Ltd.).

(Manufacturing of color filters for the second and third colors, etc.)
In Example 2, after that, the color filters of the second and third colors, the flattening layer of the upper layer, and the microlens were formed by the same method as in Example 1, and the solid-state image sensor of Example 2 was formed.
By the above steps, in Example 2 as in Example 1, the film thickness A (500 nm) of green and the film thickness B (60 nm) of the flattening layer below it, the second and third, with the color filter of the first color. The film thickness C (560 nm) of blue and red, which are the color filters of the above colors, satisfies the film thickness specified in the present invention.

<Example 3>
The third embodiment is an embodiment corresponding to the solid-state image sensor having the configuration described in the third embodiment.
The solid-state image sensor shown in Example 3 has a configuration in which only a photocurable resin is used as the material of the color filter of the first color without using a thermosetting resin. However, unlike the process described later, which is a process of patterning a color resist having a tourist property, it is sufficient that the color resist is cured by full exposure, so that the pigment content can be increased and the thin film can be thinned. Can be formed into.

(Formation of lower flattening layer)
A coating liquid containing an acrylic resin was spin-coated on the semiconductor substrate at a rotation speed of 2000 rpm, and heat-treated at 200 ° C. for 20 minutes on a hot plate to cure the resin and form a lower flattening layer. At this time, the layer thickness of the lower flattening layer was 60 nm.

(Formation of color filter for the first color)
As a material for the color filter of the first color color filter (green filter), a green pigment dispersion liquid containing a photosensitive resin and not containing a thermosetting resin was prepared. This green pigment dispersion was spin-coated on the surface of the lower flattening layer at a rotation speed of 1000 rpm. A photocurable acrylic resin was used as the main component of the green pigment dispersion. Further, for the green pigment contained in the green pigment dispersion liquid, C.I. I. PG58 was used, and the green pigment concentration in the green pigment dispersion was 70% by mass. The coating thickness of the green color filter material was 500 nm.

Next, the material for the green filter was exposed to the entire surface of the wafer using an i-line stepper type exposure device, and photocured.
Next, the photocured green filter was baked at 230 ° C. for 6 minutes to cure the green filter material to form a green filter layer.
Next, a positive resist (OFPR-800: manufactured by Tokyo Ohka Kogyo Co., Ltd.) was spin-coated on the surface of the green filter layer at a rotation speed of 1000 rpm using a spin coater, and then prebaked at 90 ° C. for 1 minute. It was. As a result, a sample coated with photoresist, which is a photosensitive resin mask material, with a film thickness of 1.5 μm was prepared.
The positive resist, which is a photosensitive resin mask material, undergoes a chemical reaction when irradiated with ultraviolet rays and dissolves in a developing solution.
Next, this sample was subjected to photolithography in which it was exposed through a photomask. As the exposure device, an exposure device using an i-line wavelength as a light source was used.

Next, a developing step is performed using 2.38% by mass of TMAH (tetramethylammonium hydride) as a developing solution to form a photoresist having openings at positions where the second and third color filters are formed. did. When using a positive resist, dehydration baking is often performed after development to cure the photoresist, which is a photosensitive resin mask material. However, this time, the baking step was not performed in order to facilitate the removal of the etching mask after dry etching. Therefore, the resist cannot be cured and the selection ratio cannot be expected to be improved. Therefore, the film thickness of the photoresist is 1.5 μm, which is more than twice the film thickness of the first color filter which is the green filter. Formed with. The size of the opening at this time was 1.1 μm × 1.1 μm.

Next, dry etching was performed using the formed photosensitive resin mask material layer as an etching mask. At this time, a parallel plate type dry etching apparatus was used as the dry etching apparatus. In addition, dry etching was performed in multiple stages so as not to affect the underlying semiconductor substrate.
First, as the gas type, CF ₄ , O ₂ , and Ar gas were mixed and etched. The gas flow rates of CF ₄ and O ₂ were set to 5 ml / min, respectively, and the gas flow rate of Ar was set to 200 ml / min. Further, the etching was performed with the pressure in the chamber at the time of etching set to 1 Pa and the RF power set to 500 W. Using this condition, the etching condition was changed to the next etching condition at the stage of etching to about 350 nm, which is 70% of the total film thickness of 500 nm of the green color filter material.

Next, etching was performed using an etching gas in which three types of _{CF 4} , O _{2, and Ar gas were mixed.} At this time, _{the gas flow rates of CF 4} and O ₂ were set to 25 ml / min, respectively, and the gas flow rate of Ar was set to 50 ml / min. At this time, etching was performed with the pressure in the chamber set to 5 Pa and the RF power set to 300 W. Under this condition, etching was performed so that the reaction products adhering to the side surface of the photoresist, which is an etching mask, could be removed. Under these conditions, etching was performed up to about 450 nm, which is 90% of the total film thickness of 500 nm of the color filter layer of the first green color. The etching amount in the second step is about 100 nm. Since _{the gas flow rates of CF 4} and O ₂ were increased, the etching rate was about 5 nm / sec, and the process proceeded very quickly.

Next, using a single Ar gas, etching was performed under the conditions that the gas flow rate of Ar was 200 ml / min, the pressure in the chamber was 1.5 Pa, and the RF power was 400 W. By etching under these conditions, the remaining portion of the green filter layer was etched, and at the same time, the lower flattening layer was etched. In the etching under the condition of Ar single gas, the physical impact by ions is the main reaction, so that the residue remaining without being etched can be effectively removed by the chemical reaction of the green filter. Further, this etching condition also has the purpose of adjusting the difference in the etching rate in the plane of the etching sample, and the etching is performed so that the over-etching amount is 10%. In other words, the film thickness of 550 nm, which is 110% of the total film thickness of 500 nm of the green color filter material, is etched under three stages.

Next, using an _{O 2} single gas, _{O 2} gas flow rate of 100 ml / min, 15 Pa the chamber pressure, the RF power was etched under the conditions of 150 W. Under this condition, the top surface of the etching mask, which was damaged and deteriorated, was removed, and the residue of the green color filter film that could not be removed by the Ar single gas remaining on the bottom surface was etched.
Next, the photosensitive resin mask material used as the etching mask was removed. The method used at this time was a method using a solvent, and the resist was removed by a spray cleaning device using a stripping solution 104 (manufactured by Tokyo Ohka Kogyo Co., Ltd.).

(Manufacturing of color filters for the second and third colors, etc.)
In Example 3, after that, the color filters of the second and third colors, the flattening layer of the upper layer, and the microlens were formed by the same method as in Example 1, and the solid-state image sensor of Example 3 was formed.
By the above steps, in Example 3 as in Example 1, the film thickness A (500 nm) of green and the film thickness B (60 nm) of the flattening layer below the green, the second and third, with the color filter of the first color. The film thickness C (560 nm) of blue and red, which are the color filters of the above colors, satisfies the film thickness specified in the present invention.
In Example 3, the green filter, which is the color filter of the first color, is cured by ultraviolet irradiation, and then heat-cured by high-temperature heating. When the pigment content is increased, the green filter can be used in the development step of patterning the photosensitive resin mask material used as the etching mask and the cleaning step of removing the photosensitive resin mask material after dry etching even if it is hardened by photocuring. This is because there is a possibility that it will come off.
Due to the effect of this example, the surface of the green pattern can be cured with a photosensitive component at a high density, and there is an effect of improving solvent resistance even when the pigment concentration is high.

<Conventional method>
Based on the conventional method described in Patent Document 1, a color filter of each color was patterned by a photolithography process.
However, the film thickness of the three colors of green, blue, and red was set to a thin film of 700 nm, and a lower flattening layer (60 nm) was provided under the entire color filter of each color.
Other than that, a solid-state image sensor was manufactured by a conventional method in the same manner as in the first embodiment.

(Evaluation)
In each of the above examples, the curing method of the first color filter is different, but the green film thickness A (500 nm) and the underlying flattening layer film thickness B (60 nm), the second and third. The film thickness C (560 nm) of blue and red, which are color filters, satisfies the film thickness specified in the present invention.
Regarding the intensity of the red signal, green signal, and blue signal of the solid-state image sensor of each of these examples, a structure in which the film thicknesses of the three colors of green, blue, and red are combined with the spectral characteristics at 700 nm by the photolithography of the conventional method. The intensities of the red signal, green signal, and blue signal of the produced solid-state image sensor were evaluated.
Table 1 below shows the evaluation results of the signal strength of each color.

As shown in Table 1, the solid-state image sensors of Examples 1 to 3 in which the green filter was thinned and formed with good rectangularity by the dry etching method were compared with the case where the green filter was formed by the conventional photolithography. Therefore, the signal strength of each color increased.
According to the production method of this example, the green filter film thickness is 500 nm, the film thickness of the lower flattening layer (60 nm) is 560 nm, and the red and blue filter film thickness is 560 nm, and all colors are formed. By reducing the filter film thickness by 20% as compared with the case where the filter film thickness was formed by photolithography, the distance from the microlens top to the device could be shortened.

As a result of evaluating the spectral characteristics after OCF formation by the production method of this example, no change in the spectral characteristics was observed. This indicates that the hardness of the thinned green filter is sufficient by the thermosetting and photocuring of this example. In order to perform color spectroscopy equivalent to the photolithography-formed green filter film thickness (700 nm) with a thin-film green filter, a green filter material with a high pigment content was used, but the spectral characteristics did not change and the film was thin-filmed. The effect of this is that the distance from the microlens top to the device is shortened and the green signal strength is increased.

In addition, the thin film reduces the probability that incoming oblique light from an oblique direction passes through the color filter and heads for another color filter pattern, and prevents light heading for another color filter pattern from entering other photoelectric conversion elements. The signal strength was increased because the color mixing was reduced.
In addition, the flattening layer of the pattern in which blue and red are colored, which is formed with good rectangularity by etching, is removed, and the distance from the microlens top to the device is shorter than that of the color filter formed by photolithography, and the signal strength is increased. Increased.

Further, using the methods of Examples 1 to 3, the heights of the second color filter 15 and the third color filter 16 are the first color color filter 14 and the lower flattening layer 12. Even when the color filter is formed at a height lower than the sum of the thicknesses of the above, the pigment content is increased by the amount of the thinner film, as compared with the case of forming by the conventional photolithography. , Signal strength increased.

Although the present invention has been described above with reference to each embodiment, the scope of the present invention is not limited to the illustrated and described exemplary embodiments, and the effect is equal to that of the object of the present invention. Also includes all embodiments. Furthermore, the scope of the present invention is not limited to the combination of the features of the invention defined by the claims, but may be defined by any desired combination of the specific features of all the disclosed features.

10 ... Semiconductor substrate 11 ... Photoelectric conversion element 12 ... Lower flattening layer 13 ... Upper flattening layer 14 ... First color color filter 15 ... Second color color Filter 16 ... Third color color filter 18 ... Microlens 20 ... Etching mask 20a ... Photosensitive resin mask layer 20b ... Opening 30 ... Color filter layer

Claims (8)

A semiconductor substrate in which multiple photoelectric conversion elements are arranged two-dimensionally,
A color filter layer formed on the semiconductor substrate and two-dimensionally arranged with a plurality of color filters corresponding to each photoelectric conversion element in a preset regular pattern.
A lower flattening layer arranged only between the color filter of the first color selected from the plurality of colors and the semiconductor substrate is provided.
The film thickness of the first color color filter is A [nm], the film thickness of the lower flattening layer is B [nm], and the film thickness of the color filter of a color other than the first color is C [nm]. A solid-state image sensor, which satisfies the following equations (1) to (3).
200 [nm] ≤ A ≤ 700 [nm] ... (1)
0 [nm] <B ≦ 200 [nm] ・ ・ ・ (2)
A + B-200 [nm] ≤ C ≤ A + B + 200 [nm] ... (3) The first color filter contains a thermosetting resin and a photocurable resin, and the content of the thermosetting resin is larger than the content of the photocurable resin. Item 1. The solid-state imaging device according to Item 1. The solid-state image sensor according to claim 1 or 2, wherein the color filter of the first color has a concentration of a pigment as a colorant of 50% by mass or more. Further, the color filter layer is provided with microlenses two-dimensionally arranged corresponding to each of the photoelectric conversion elements, and the height from the lens top to the lens bottom of the microlens is 400 nm or more and 800 nm or less. The solid-state image sensor according to any one of claims 1 to 3 , wherein the solid-state image sensor is in the range of 1. The solid-state image sensor according to any one of claims 1 to 4 , wherein the color filter of the first color has the largest occupied area among the color filters of the plurality of colors. The method for manufacturing a solid-state image sensor according to claim 1.
After forming the lower flattening layer on the semiconductor substrate, applying the coating liquid for the color filter of the first color on the coating liquid and curing the lower layer flattening layer and the color filter layer in this order, the lower layer flattening layer and the color filter layer are formed in this order. The color of the first color is obtained by removing the formed color filter layer portion other than the arrangement position of the color filter of the first color and the lower flattening layer portion located below the color filter layer portion to be removed by dry etching. The first step of patterning the filter and
A method for manufacturing a solid-state image sensor, which comprises, after the first step, a second step of patterning and forming a color filter of a color other than the first color by photolithography. The method for manufacturing a solid-state image sensor according to claim 1.
After forming the lower flattening layer on the semiconductor substrate, applying the coating liquid for the color filter of the first color on the lower layer flattening layer and curing the lower layer flattening layer and the color filter layer in this order. , The lower flattening layer portion located below the formed color filter layer portion and the color filter layer portion to be removed other than the arrangement position of the color filter of the first color is removed by dry etching to remove the first color. The first step of patterning the color filter and
A method for manufacturing a solid-state image sensor, which comprises, after the first step, a second step of patterning and forming a color filter of a color other than the first color by dry etching. The method for manufacturing a solid-state image sensor according to claim 6 or 7 , wherein the heating temperature of the first color filter at the time of curing is 230 ° C. or higher and 270 ° C. or lower.

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