Method for manufacturing an infrared light cut filter, filter for a solid-state image sensor, and a solid-state image sensor

Abstract

The method includes forming an infrared light cutting layer containing an infrared light absorbing pigment, forming a protective layer against a stripping solution on the infrared light cutting layer, forming a resist pattern on the protective layer, patterning the protective layer and the infrared light cutting layer by dry etching using the resist pattern, and stripping the resist pattern from the protective layer using a stripping solution.

Description

Technology Field

[0001] The present invention relates to a method for manufacturing an infrared light cut filter, a filter for a solid-state imaging device, and a solid-state imaging device. Background Technology

[0002] Solid-state imaging devices, such as CMOS image sensors and CCD image sensors, are equipped with a photoelectric conversion element that converts the intensity of incident light into an electrical signal. One example of a solid-state imaging device is capable of detecting light corresponding to each of a plurality of colors. The solid-state imaging device is equipped with a color filter for each color and a photoelectric conversion element for each color, and detects light for each color by the photoelectric conversion element for each color (see, for example, Patent Document 1). Another example of a solid-state imaging device is equipped with an organic photoelectric conversion element and an inorganic photoelectric conversion element, and detects light of each color by the photoelectric conversion element without using a color filter (see, for example, Patent Document 2).

[0003] A solid-state imaging element is provided with an infrared light cut filter on a photoelectric conversion element. An infrared light-absorbing dye having the infrared light cut filter absorbs infrared light, thereby cutting off the infrared light that can be detected by each photoelectric conversion element with respect to the photoelectric conversion element. As a result, the detection precision of visible light at each photoelectric conversion element is increased. The infrared light cut filter includes, for example, a cyanine dye which is an infrared light-absorbing dye (for example, refer to Patent Document 3). Prior art literature

[0004] Japanese Patent Publication No. 2003-060176 Japanese Patent Publication No. 2018-060910 Japanese Patent Publication No. 2007-219114 The problem to be solved

[0005] However, along with the miniaturization of pixel sizes in solid-state imaging devices, miniaturization of infrared light cut filters is required. The miniaturization of infrared light cut filters is realized by dry etching using a resist pattern formed on the infrared light cut filter. In the patterning of an infrared light cut filter using dry etching, a resist pattern is first formed on the infrared light cut filter. Subsequently, the infrared light cut filter is etched using the resist pattern, and then the resist pattern is peeled off from the infrared light cut filter. When the stripping solution used to peel off the resist pattern from the infrared light cut filter comes into contact with the infrared light cut filter, some of the infrared light absorbing pigment contained in the infrared light cut filter is leached out of the infrared light cut filter. As a result, the spectral characteristics of the infrared light cut filter deteriorate.

[0006] The present invention aims to provide a method for manufacturing an infrared light cut filter capable of suppressing deterioration in the spectral characteristics of the infrared light cut filter, a filter for a solid-state imaging device, and a solid-state imaging device. means of solving the problem

[0007] A method for manufacturing an infrared light cut filter to solve the above problem comprises forming an infrared light cut layer containing an infrared light absorbing pigment, forming a protective layer against a stripping solution on the infrared light cut layer, forming a resist pattern on the protective layer, patterning the protective layer and the infrared light cut layer by dry etching using the resist pattern, and stripping the resist pattern from the protective layer using the stripping solution.

[0008] A filter for a solid-state imaging device for solving the above problem comprises a three-color filter, a red filter, a green filter, and a blue filter located on the incident side of light with respect to a first photoelectric conversion device, an infrared light pass filter located on the incident side of light with respect to a second photoelectric conversion device, and an infrared light cut filter located on the incident side of light with respect to the color filters. The infrared light cut filter comprises an infrared light cut layer and a protective layer laminated on the infrared light cut layer and located on the incident side of light with respect to the infrared light cut layer.

[0009] A solid-state imaging device for solving the above problem comprises a first photoelectric conversion device, a second photoelectric conversion device, and a filter for the solid-state imaging device described above.

[0010] According to each of the above configurations, since the contact of the infrared light cutting layer with the stripping solution is suppressed by the protective layer, the penetration of the stripping solution into the infrared light cutting layer is suppressed. As a result, the leaching of the infrared light absorbing pigment from the infrared light cutting layer is suppressed, and consequently, the deterioration of the spectral characteristics of the infrared light cutting filter is suppressed. Brief explanation of the drawing

[0011] FIG. 1 is an exploded perspective view showing the structure of a solid-state imaging element of one embodiment. Figure 2 is a process diagram for explaining a method for manufacturing an infrared light cut filter. Figure 3 is a process diagram for explaining a method of manufacturing an infrared light cut filter. Figure 4 is a process diagram for explaining a method of manufacturing an infrared light cut filter. Figure 5 is a process diagram for explaining a method for manufacturing an infrared light cut filter. Figure 6 is a process diagram for explaining a method for manufacturing an infrared light cut filter. Figure 7 is a process diagram for explaining a method for manufacturing an infrared light cut filter. Specific details for implementing the invention

[0012] With reference to FIGS. 1 to 7, a method for manufacturing an infrared light cut filter, a filter for a solid-state imaging device, and an embodiment of a solid-state imaging device will be described. Hereinafter, a solid-state imaging device, a method for manufacturing an infrared light cut filter, and an embodiment will be described in order. In addition, in the present embodiment, infrared light is light having a wavelength included in a range of 0.7 μm (700 nm) or more and 1 mm or less, and near-infrared light is light having a wavelength included in a range of particularly 700 nm or more and 1100 nm or less within infrared light.

[0013] [Solid State Imaging Element]

[0014] Referring to FIG. 1, a solid-state imaging element is described. FIG. 1 is a schematic diagram showing the separation of each layer in a part of the solid-state imaging element.

[0015] As shown in FIG. 1, the solid-state imaging element (10) comprises a filter (10F) for the solid-state imaging element and a plurality of photoelectric conversion elements (11).

[0016] A plurality of photoelectric conversion elements (11) comprises a photoelectric conversion element for red (11R), a photoelectric conversion element for green (11G), a photoelectric conversion element for blue (11B), and a photoelectric conversion element for infrared light (11P). The photoelectric conversion element for red (11R), the photoelectric conversion element for green (11G), and the photoelectric conversion element for blue (11B) are examples of a first photoelectric conversion element, and the photoelectric conversion element for infrared light (11P) is an example of a second photoelectric conversion element.

[0017] The solid-state imaging element (10) comprises a plurality of photoelectric conversion elements (11R) for red light, a plurality of photoelectric conversion elements (11G) for green light, a plurality of photoelectric conversion elements (11B) for blue light, and a plurality of photoelectric conversion elements (11P) for infrared light. Each photoelectric conversion element (11P) for infrared light measures the intensity of infrared light. Additionally, in FIG. 1, for convenience of illustration, a repeating unit of the photoelectric conversion element (11) in the solid-state imaging element (10) is shown.

[0018] The filter (10F) for the solid-state imaging element comprises a plurality of visible light filters, an infrared light pass filter (12P), an infrared light cut filter (13), a plurality of visible light micro-lenses, and an infrared light micro-lens (14P).

[0019] The visible light color filter consists of a red filter (12R), a green filter (12G), and a blue filter (12B). The red filter (12R) is located on the incident side of light with respect to the red photoelectric conversion element (11R). The green filter (12G) is located on the incident side of light with respect to the green photoelectric conversion element (11G). The blue filter (12B) is located on the incident side of light with respect to the blue photoelectric conversion element (11B).

[0020] The infrared light pass filter (12P) is located on the incident side of the light with respect to the infrared light photoelectric conversion element (11P). The infrared light pass filter (12P) cuts off visible light that can be detected by the infrared light photoelectric conversion element (11P) with respect to the infrared light photoelectric conversion element (11P). That is, the infrared light pass filter (12P) suppresses visible light incident on the filter (10F) for the solid-state imaging element from being transmitted to the infrared light photoelectric conversion element (11P). By doing so, the detection precision of infrared light by the infrared light photoelectric conversion element (11P) is increased. The infrared light that can be detected by the infrared light photoelectric conversion element (11P) is, for example, near-infrared light.

[0021] The infrared light cut filter (13) is located on the incident side of the light with respect to each color filter (12R, 12G, 12B). The infrared light cut filter (13) has an infrared light cut layer (13A) and a protective layer (13B). The protective layer (13B) is laminated on the infrared light cut layer (13A) and is also located on the incident side of the light with respect to the infrared light cut layer (13A).

[0022] The infrared light cutting layer (13A) is provided with a through hole (13AH). When viewed from a viewpoint facing the plane in which the infrared light cutting layer (13A) is unfolded, an infrared light pass filter (12P) is located within the area partitioned by the through hole (13AH). Meanwhile, when viewed from a viewpoint facing the plane in which the infrared light cutting layer (13A) is unfolded, the infrared light cutting layer (13A) is located on the red filter (12R), the green filter (12G), and the blue filter (12B).

[0023] The infrared light cutting layer (13A) includes an infrared light absorbing pigment. The infrared light absorbing pigment has a maximum value in the absorbance of infrared light at any wavelength included in near-infrared light. Therefore, according to the infrared light cutting layer (13A), it is possible to reliably absorb near-infrared light passing through the infrared light cutting layer (13A). As a result, near-infrared light that can be detected by the photoelectric conversion element (11) for each color is sufficiently cut by the infrared light cutting layer (13A).

[0024] The protective layer (13B) is provided with a through hole (13BH). When viewed from a direction opposite to the plane in which the protective layer (13B) is unfolded, the through hole (13BH) of the protective layer (13B) overlaps with the through hole (13AH) of the infrared light cutting layer (13A). The shape of the edge of the through hole (13BH) of the protective layer (13B) is equivalent to the shape of the edge of the through hole (13AH) of the infrared light cutting layer (13A). When viewed from a point opposite to the plane in which the protective layer (13B) is unfolded, an infrared light pass filter (12P) is located within the area partitioned by the through hole (13BH).

[0025] Meanwhile, when viewed from a point opposite to the plane where the protective layer (13B) is unfolded, the protective layer (13B) is located on the red filter (12R), the green filter (12G), and the blue filter (12B).

[0026] The protective layer (13B) is preferably formed of a transparent resin that does not affect the spectral characteristics of the visible light filter and the infrared light cut layer (13A). The protective layer (13B) is preferably formed of a transmittance of, for example, 90% or more for visible light and near-infrared light.

[0027] The thickness of the protective layer (13B) is preferably 1 nm or more and 200 nm or less. Since the protective layer (13B) is 1 nm or more, the certainty of preventing the stripping solution from penetrating from the surface of the protective layer (13B) to the infrared light cutting layer (13A) is improved when forming the infrared light cutting filter (13). Since the protective layer (13B) is 200 nm or less, the thickness of the protective layer (13B) is prevented from affecting the spectral characteristics of the infrared light cutting layer (13A).

[0028] The micro-lens consists of a red micro-lens (14R), a green micro-lens (14G), a blue micro-lens (14B), and an infrared micro-lens (14P). The red micro-lens (14R) is located on the incident side of light with respect to the red filter (12R). The green micro-lens (14G) is located on the incident side of light with respect to the green filter (12G). The blue micro-lens (14B) is located on the incident side of light with respect to the blue filter (12B). The infrared micro-lens (14P) is located on the incident side of light with respect to the infrared light pass filter (12P).

[0029] Each micro-lens (14R, 14G, 14B, 14P) is provided with an incident surface (14S) which is an outer surface. Each micro-lens (14R, 14G, 14B, 14P) has a difference in refractive index with the outside air to collect light entering the incident surface (14S) toward each photoelectric conversion element (11R, 11G, 11B, 11P). Each micro-lens (14R, 14G, 14B, 14P) includes a transparent resin.

[0030] [Method for manufacturing an infrared light cut filter]

[0031] Referring to FIGS. 2 to 7, a method for manufacturing an infrared light cut filter (13) is described.

[0032] A method for manufacturing an infrared light cut filter comprises forming an infrared light cut layer, forming a protective layer, forming a resist pattern, patterning the protective layer and the infrared light cut layer, and peeling the resist pattern from the protective layer. In forming the infrared light cut layer, an infrared light cut layer comprising an infrared light absorbing pigment is formed. In forming the protective layer, a protective layer against a stripping solution is formed on the infrared light cut layer. In forming the resist pattern, a resist pattern is formed on the protective layer. In patterning the protective layer and the infrared light cut layer, the protective layer and the infrared light cut layer are patterned by dry etching using the resist pattern. In peeling the resist pattern from the protective layer, the resist pattern is peeled from the protective layer using a stripping solution.

[0033] Hereinafter, with reference to the drawings, a method for manufacturing an infrared light cut filter will be described in more detail. Additionally, in FIGS. 2 to 7, for convenience of illustration, only the structure corresponding to the cross-section when the repeating unit of the solid imaging element (10) shown in FIG. 1 is cut along the line II-II is shown.

[0034] As shown in FIG. 2, when manufacturing an infrared light cut filter, a semiconductor substrate (21) having a plurality of photoelectric conversion elements formed thereon is prepared first. A plurality of photoelectric conversion elements are arranged two-dimensionally on the semiconductor substrate (21). The semiconductor substrate (21) includes a blue photoelectric conversion element (21B) corresponding to the blue filter (12B) described above, and an infrared photoelectric conversion element (21P) corresponding to the infrared light pass filter (12P). The material forming the semiconductor substrate (21) may be, for example, silicon oxide such as Si and SiO2, silicon nitride such as SiN, and a mixture thereof.

[0035] Next, a filter for each color and an infrared light pass filter corresponding to each photoelectric conversion element of the semiconductor substrate (21) are formed. By doing so, a blue filter (22B) is formed on a blue photoelectric conversion element (21B), and an infrared light pass filter (22P) is formed on an infrared photoelectric conversion element (21P).

[0036] Each color filter is formed by forming a coating film containing a pigment and a photosensitive resin, and by patterning the coating film using a photolithography method. For forming each color filter, organic pigments or inorganic pigments may be used alone or in a mixture of two or more types. It is preferable that the pigment be a pigment with high color development and high heat resistance, particularly a pigment with high heat decomposition resistance, and it is preferable that it be an organic pigment. The organic pigment may be, for example, a phthalocyanine-based pigment, an azo-based pigment, anthraquinone-based pigment, quinacridone-based pigment, dioxazine-based pigment, anthanethron-based pigment, indanthron-based pigment, perylene-based pigment, thioindigo-based pigment, isoindolin-based pigment, quinophthalone-based pigment, and diketopyrrolopyrrole-based pigment.

[0037] An infrared light-transmitting filter is formed by forming a film containing a black pigment or black dye and a photosensitive resin, and by patterning the film using a photographic method. The material forming the infrared light-transmitting filter (22P) comprises a black pigment or black dye and a photosensitive composition. The black pigment is a single pigment having black color, or a mixture having black color from two or more pigments. The black dye may be, for example, an azo dye, an anthraquinone dye, an azine dye, a quinoline dye, a perinone dye, a perylene dye, and a methine dye. The photosensitive composition includes, for example, a binder resin, a photopolymerization initiator, a polymerizable monomer, an organic solvent, and a leveling agent.

[0038] The material forming the infrared light pass filter (22P) may contain inorganic oxide particles for adjusting the refractive index. Inorganic oxides are, for example, aluminum oxide, silicon oxide, zirconium oxide, and titanium oxide. The infrared light pass filter (22P) may contain additives to provide other functions different from the function of cutting visible light, such as light stabilizers, antioxidants, heat stabilizers, and antistatic agents.

[0039] Then, an infrared light cutting layer (23A) containing an infrared light absorbing pigment is formed. When forming the infrared light cutting layer (23A), first, a coating solution containing an infrared light absorbing pigment, a transparent resin, and an organic solvent is applied to each color filter and an infrared light passing filter, and the coating film is dried. Subsequently, the dried coating film is cured by heating. By doing so, an infrared light cutting layer (23A) is formed on each color filter and an infrared light passing filter.

[0040] The material forming the infrared light cutting layer (23A) includes a transparent resin and an infrared light absorbing pigment. The transparent resin may be, for example, an acrylic resin, a polyamide resin, a polyimide resin, a polyurethane resin, a polyester resin, a polyether resin, a polyolefin resin, a polycarbonate resin, a polystyrene resin, and norbornene resin. Among these resins, the transparent resin is preferably an acrylic resin.

[0041] Infrared light-absorbing dyes may be, for example, anthraquinone-based dyes, cyanine-based dyes, phthalocyanine-based dyes, dithiol-based dyes, diimonium-based dyes, squaryllium-based dyes, and croconium-based dyes. Among these dyes, it is preferable that the infrared light-absorbing dye be a cyanine-based dye or a phthalocyanine-based dye.

[0042] As shown in FIG. 3, a protective layer (23B) is formed on an infrared light cutting layer (23A). When forming the protective layer (23B), first, a coating liquid containing a transparent resin is applied onto the infrared light cutting layer (23A), and the coating film is dried. Then, the dried coating film is cured by heating. By doing so, the protective layer (23B) is formed.

[0043] The material forming the protective layer (23B) includes a transparent resin. The transparent resin may be, for example, an acrylic resin, a polyamide resin, a polyimide resin, a polyurethane resin, a polyester resin, a polyether resin, a polyolefin resin, a polycarbonate resin, a polystyrene resin, and a norbornene resin.

[0044] The material forming the protective layer (23B) preferably comprises a resin having a cross-linked structure in which epoxy groups and functional groups reacting with epoxy groups are cross-linked. Since the resin forming the protective layer (23B) is a resin having a cross-linked structure, the resistance to the peeling solution in the protective layer (23B) is increased.

[0045] Functional groups that react with epoxy groups include, for example, hydroxyl groups, phenolic hydroxyl groups, organic acids, acid anhydrides, and amino groups. These groups react easily with epoxy groups during film formation and form a cross-linked structure, thereby increasing the resistance of the protective layer (23B) to the stripping solution. In particular, it is more preferable that the material forming the protective layer (23B) be a resin having a cross-linked structure in which phenolic hydroxyl groups (-C6H4OH) and epoxy groups are cross-linked. Since the resin has a cross-linked structure formed by phenolic hydroxyl groups and epoxy groups, the resistance of the protective layer (23B) to the stripping solution is further increased. Since phenolic hydroxyl groups exhibit weak acidity, they are difficult to cross-link with epoxy groups during the resin polymerization process, and are advantageous in terms of coating properties in that they cause a cross-linking reaction during the heating process when making the film.

[0046] Furthermore, it is preferable that the protective layer (23B) be formed of an acrylic resin. It is preferable to use 4-hydroxyphenyl methacrylate and glycidyl methacrylate as monomers constituting the acrylic resin. That is, it is preferable that the protective layer (23B) be formed by an acrylic resin formed from monomers containing at least 4-hydroxyphenyl methacrylate and glycidyl methacrylate.

[0047] In addition to 4-hydroxyphenyl methacrylate and glycidyl methacrylate, monomers copolymerizable with these may be used as monomers constituting the acrylic resin forming the protective layer (23B). Copolymerizable monomers may be, for example, styrene-based monomers, (meth)acrylic monomers, vinyl ester-based monomers, vinyl ether-based monomers, vinyl monomers containing halogen elements, diene-based monomers, and maleimide-based monomers. Styrene-based monomers may be, for example, styrene, α-methylstyrene, p-methylstyrene, m-methylstyrene, p-methoxystyrene, p-hydroxystyrene, p-acetoxystyrene, vinyltoluene, ethylstyrene, phenylstyrene, and benzylstyrene. (Meth)acrylic monomers may be, for example, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, and dicyclofentanyl methacrylate. Vinyl ester monomers may be, for example, vinyl acetate. Vinyl ether monomers may be, for example, vinyl methyl ether. Halogen element-containing vinyl monomers may be, for example, vinyl chloride. Diene monomers may be, for example, butadiene and isobutylene. Maleimide monomers may be, for example, cyclohexyl maleimide and phenyl maleimide. The acrylic resin may be formed from two or more of the monomers described above.

[0048] A monomer capable of copolymerizing with 4-hydroxyphenyl methacrylate and glycidyl methacrylate, that is, a monomer capable of copolymerizing with one or both of 4-hydroxyphenyl methacrylate and glycidyl methacrylate, is preferably an acrylic monomer containing an aromatic ring. Acrylic monomers containing an aromatic ring are, for example, benzyl (meth)acrylate, phenyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, nonylphenoxypolyethylene glycol (meth)acrylate, phenoxypolypropylene glycol (meth)acrylate, 2-(meth)acryloyloxyethyl-2-hydroxypropylphthalate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-(meth)acryloyloxyethylhydrogenphthalate, 2-(meth)acryloyloxypropylhydrogenphthalate, ethoxylated ortho-phenylphenol (meth)acrylate, o-phenylphenoxyethyl (meth)acrylate, 3-phenoxybenzyl (meth)acrylate, 4-hydroxyphenyl (meth)acrylate, It may be 2-naphthol (meth)acrylate, 4-biphenyl (meth)acrylate, 9-anthylmethyl (meth)acrylate, 2-[3-(2H-benzotriazole-2-yl)-4-hydroxyphenyl]ethyl (meth)acrylate, phenolethylene oxide (EO) modified acrylate, nonylphenol EO modified acrylate, 2-(meth)acryloyloxyethyl phthalate, and 2-(meth)acryloyloxyethyl hexahydrophthalate. The acrylic monomer containing an aromatic ring is particularly preferably phenyl methacrylate.

[0049] As shown in FIG. 4, a resist pattern (RP) is formed on the portion of the protective layer (23B) located on each color filter. When forming the resist pattern (RP), a photoresist layer is first formed to cover the entire protective layer (23B). For the material forming the photoresist layer, a positive type resist or a negative type resist may be used.

[0050] Then, a portion of the photoresist layer is exposed using a photomask. At this time, if the photoresist layer is formed as a positive type resist, only the portion of the photoresist layer covering the infrared light pass filter (22P) is exposed. In contrast, if the photoresist layer is formed as a negative type resist, only the portion of the photoresist layer covering each color filter is exposed.

[0051] Next, the photoresist layer is developed. By doing so, a resist pattern (RP) having an opening that overlaps the infrared light pass filter (22P) is formed when viewed from a point opposite to the plane where the protective layer (23B) is unfolded.

[0052] As shown in FIG. 5, the protective layer (23B) and the infrared light cutting layer (23A) are patterned by dry etching using a resist pattern (RP). By doing so, when viewed from a point opposite to the plane in which the protective layer (23B) is unfolded, the portion covering the infrared light pass filter (22P) among the laminates of the protective layer (23B) and the infrared light cutting layer (23A) is removed from each layer (23A, 23B).

[0053] Dry etching can be, for example, plasma etching. In dry etching, it is possible to use reactive gases and noble gases, that is, gases containing Group 18 elements, as etching gases. In dry etching of the infrared light cutting layer (23A) and the protective layer (23B), it is possible to apply a bias to the etching target containing these layers (23A, 23B). By doing so, anisotropic etching using a resist pattern (RP) is possible.

[0054] As shown in FIG. 6, a stripping solution (LM) is used to strip the resist pattern (RP) from the protective layer (23B). The stripping solution (LM) may be a liquid capable of dissolving the resist pattern (RP). The stripping solution (LM) may be, for example, N-methylpyrrolidone or dimethyl sulfoxide. When the stripping solution (LM) is N-methylpyrrolidone or dimethyl sulfoxide, the protective layer (23B) is an acrylic resin having the cross-linked structure described above, thereby making it possible to satisfy all requirements regarding resistance to the stripping solution (LM), heat resistance, and spectral characteristics in an infrared light cut filter.

[0055] In addition, in the manufacturing method of the present embodiment, when the infrared light cutting layer (23A) comes into contact with the peeling solution (LM), the infrared light cutting layer (23A) is covered by a protective layer (23B) that does not contain an infrared light absorbing pigment. Therefore, compared to the case where the infrared light cutting layer (23A) is not covered by the protective layer (23B), the contact area with the peeling solution (LM) in the infrared light cutting layer (23A) is reduced, thereby allowing the amount of peeling solution (LM) penetrating into the infrared light cutting layer (23A) to be reduced. As a result, it is possible to reduce the amount of infrared light absorbing pigment leached from the infrared light cutting layer (23A). Additionally, although the protective layer (23B) is in contact with the peeling solution (LM), since the protective layer (23B) does not contain an infrared light absorbing pigment, the spectral characteristics of the protective layer (23B) are suppressed from affecting the spectral characteristics of the infrared light cut filter.

[0056] In addition, in FIG. 6, the immersion method is illustrated as a method of contacting the protective layer (23B) and the stripping solution (LM), but the method of contacting the protective layer (23B) and the stripping solution (LM) may also be a spray type and a spin type.

[0057] As shown in FIG. 7, the resist pattern (RP) is removed on the protective layer (23B). By doing so, an infrared light cut filter having a protective layer (23B) and an infrared light cut layer (23A) can be formed. Among the infrared light cut layer (23A) and the protective layer (23B) formed by the manufacturing method described above, the portion corresponding to the repeating unit of the photoelectric conversion element (11) is an infrared light cut filter (13) having an infrared light cut layer (13A) and a protective layer (13B).

[0058] In addition, it is possible to manufacture a solid-state imaging element by forming a plurality of micro-lenses on an infrared light cut filter manufactured by the method described above. The plurality of micro-lenses are formed, for example, by forming a coating film containing a transparent resin, patterning the coating film using a photolithography method, and reflow by heat treatment.

[0059] [Example]

[0060] Referring to Table 1, examples and comparative examples of infrared light cut filters are described.

[0061] [Example 1]

[0062] An infrared light cutting layer comprising an infrared light absorbing pigment, cyanine pigment, and an acrylic resin was formed on a glass substrate, and a protective layer having a thickness of 50 nm was formed on the infrared light cutting layer.

[0063] For forming the protective layer, an acrylic resin copolymerized with phenyl methacrylate, 4-hydroxyphenyl methacrylate, and glycidyl methacrylate was used. Additionally, when copolymerizing the acrylic resin, when the total sum of the above-described monomers was 100 mass%, phenyl methacrylate was set to 50 mass%, 4-hydroxyphenyl methacrylate was set to 25 mass%, and glycidyl methacrylate was set to 25 mass%. By doing so, the infrared light cut filter of Example 1 was obtained.

[0064] [Example 2]

[0065] In Example 1, an infrared light cut filter of Example 2 was obtained by the same method as in Example 1, except that phenyl methacrylate was set to 65 mass%, 4-hydroxyphenyl methacrylate was set to 30 mass%, and glycidyl methacrylate was set to 5 mass%.

[0066] [Comparative Example 1]

[0067] In Example 1, an infrared light cut filter of Comparative Example 1 was obtained by the same method as in Example 1, except that a protective layer was not formed.

[0068] [Evaluation Method]

[0069] [Spectroscopic properties]

[0070] Using a spectrophotometer (U-4100, manufactured by Hitachi High Technologies Co., Ltd.), the transmittance of an infrared light cut filter for light having wavelengths ranging from 350 nm to 1150 nm was measured. By doing so, the transmittance spectrum was obtained for each infrared light cut filter. In addition, the transmittance spectrum was obtained for each infrared light cut filter before and after the peel resistance test and heat resistance test described below. From the transmittance spectrum, it was confirmed that the maximum absorption wavelength for each infrared light cut filter before and after each test was 950 nm.

[0071] [Resistant to peeling]

[0072] Each infrared light cut filter was immersed in a stripping solution for 1 minute. The transmittance of the infrared light cut filter after immersion was measured, and at 950 nm, the difference between the transmittance of the infrared light cut filter after immersion and the transmittance of the infrared light cut filter before immersion was calculated.

[0073] [Heat resistance]

[0074] After the anti-stripping test was performed, each infrared light cut filter was heated on a hot plate at 250°C for 10 minutes. The transmittance of the infrared light cut filter after heating was measured, and at 950 nm, the difference between the transmittance of the infrared light cut filter after heating and the transmittance of the infrared light cut filter before heating was calculated.

[0075] [Evaluation Results]

[0076] Difference in transmittance (%) Peel-resistant test Heat resistance test Example 1 0.6 13 Example 2 0.03 12 Comparative Example 1 10 13

[0077] As shown in Table 1, after the anti-peeling test, it was confirmed that the difference in transmittance of the infrared light cut filter of Example 1 was 0.6%, and the difference in transmittance of the infrared light cut filter of Example 2 was 0.03%. Thus, it was confirmed that for the infrared light cut filters of Example 1 and Example 2, the difference in transmittance after the anti-peeling test was 1% or less. In contrast, it was confirmed that the difference in transmittance of the infrared light cut filter of Comparative Example 1 after the anti-peeling test was 10%. Furthermore, it was confirmed that the difference in the infrared light cut filter of Comparative Example 1 was more than 10 times greater than the difference in the infrared light cut filters of Examples 1 and 2. In this way, it was confirmed that by providing a protective layer covering the infrared light cut filter, changes in the transmittance of the infrared light cut filter are suppressed after treatment with a stripping solution.

[0078] In addition, after the heat resistance test, it was confirmed that the difference in transmittance of the infrared light cut filter of Example 1 was 13%, and the difference in transmittance of the infrared light cut filter of Example 2 was 12%. In contrast, after the heat resistance test, it was confirmed that the difference in transmittance of the infrared light cut filter of Comparative Example 1 was 13%.

[0079] As such, the difference in transmittance before and after the heat resistance test of Example 1, Example 2, and Comparative Example 1 was all of the same degree. That is, it can be said that the infrared light cut filters of Example 1 and Example 2 and the infrared light cut filter of Comparative Example 1 have the same degree of heat resistance. From the above results, it was confirmed that the application of a protective film to the infrared light cut filter does not affect the heat resistance of the infrared light cut filter, and that the infrared light cut filters of Example 1 and Example 2 have both resistance to the stripping solution and resistance to heat.

[0080] As described above, according to the method for manufacturing an infrared light cut filter, a filter for a solid-state imaging device, and one embodiment of a solid-state imaging device, the effects described below can be obtained.

[0081] (1) Since the infrared light cutting layer (23A) is prevented from coming into contact with the stripping solution (LM) by the protective layer (23B), the stripping solution is prevented from penetrating the infrared light cutting layer (23A). As a result, the leaching of infrared light absorbing pigment from the infrared light cutting layer (23A) is prevented, and consequently, the deterioration of the spectral characteristics of the infrared light cutting filter (13) is prevented.

[0082] (2) Since the resin forming the protective layer (23B) includes a cross-linked structure, the leaching of infrared light-absorbing pigment from the infrared light-cutting layer (23A) can be further suppressed.

[0083] (3) Since the resin forming the protective layer (23B) is an acrylic resin containing a cross-linked structure, the leaching of infrared light-absorbing pigment from the infrared light-cutting layer (23A) can be further suppressed.

[0084] (4) By forming the protective layer (23B) using an acrylic resin composed of 4-hydroxyphenyl methacrylate and glycidyl methacrylate, the leaching of infrared light-absorbing pigment from the infrared light-cutting layer (23A) can be further suppressed.

[0085] (5) Since the ratio of each monomer to form the acrylic resin is within the range described above, the leaching of infrared light absorbing pigment from the infrared light cutting layer (23A) can be further suppressed, and the heat resistance of the infrared light cutting filter including the protective layer (23B) is maintained.

[0086] (6) Since the peeling solution (LM) is N-methylpyrrolidone or dimethyl sulfoxide, it is possible to suppress the release of infrared light-absorbing pigments into the peeling solution (LM) by the protective layer (23B).

[0087] [Change Example]

[0088] In addition, the above-described embodiment may be implemented by modifying it as follows.

[0089] [Protection Layer]

[0090] · In the protective layer (13B), the mass percentage of each monomer when forming the acrylic resin using phenyl methacrylate, 4-hydroxyphenyl methacrylate, and glycidyl methacrylate can be appropriately changed. Additionally, the protective layer (13B) does not have to be formed by an acrylic resin formed using phenyl methacrylate, 4-hydroxyphenyl methacrylate, and glycidyl methacrylate. Even in this case, it is possible to obtain an effect similar to (1) described above by providing the protective layer (13B) that covers the infrared light cut filter (13) and the infrared light cut layer (13A).

[0091] · The protective layer (13B) does not have to be formed by a resin having a cross-linked structure in which phenolic hydroxyl groups and epoxy groups are cross-linked, nor does it have to be formed by a resin having a cross-linked structure in which epoxy groups and functional groups that react with epoxy groups are cross-linked. Even in this case, it is possible to obtain an effect similar to (1) described above by having the infrared light cut filter (13) have a protective layer (13B) covering the infrared light cut layer (13A).

[0092] The material forming the protective layer (13B) may be the same as the material forming each micro lens, or may be different from each other.

[0093] [Skin peeling solution]

[0094] · The stripping solution (LM) may be a liquid other than N-methylpyrrolidone and dimethyl sulfoxide, provided that it is a liquid capable of dissolving the material forming the resist pattern (RP).

[0095] [Barrier layer]

[0096] · The filter (10F) for the solid-state imaging element may be provided with a barrier layer located between the infrared light cut filter (13) and each micro-lens. The barrier layer prevents an oxidation source from reaching the infrared light cut filter (13). The oxidation source is oxygen and water, etc. Additionally, the barrier layer may be placed on the outer surface of each micro-lens.

[0097] · When the filter (10F) for the solid-state imaging element is provided with a barrier layer, the solid-state imaging element (10) may be provided with an anchor layer between the barrier layer and the lower layer of the barrier layer. In this case, the adhesion between the barrier layer and the lower layer of the barrier layer is enhanced by the anchor layer. Additionally, the solid-state imaging element (10) may be provided with an anchor layer between the barrier layer and the upper layer of the barrier layer. In this case, the adhesion between the barrier layer and the upper layer of the barrier layer is enhanced by the anchor layer. The material forming the anchor layer is, for example, a polyfunctional acrylic resin or a silane coupling agent.

[0098] [Color Filter]

[0099] · The color filter may be a three-color filter consisting of a cyan filter, a yellow filter, and a magenta filter. Additionally, the color filter may be a four-color filter consisting of a cyan filter, a yellow filter, a magenta filter, and a black filter. Additionally, the color filter may be a four-color filter consisting of a transparent filter, a yellow filter, a red filter, and a black filter.

[0100] [etc]

[0101] Each color filter (12R, 12G, 12B) may have a thickness equal to that of the infrared light pass filter (12P) or different thicknesses. The thickness of each color filter (12R, 12G, 12B) may be, for example, 0.5㎛ or more and 5㎛ or less.

[0102] The material forming the infrared light cut filter (13) may include additives that have different functions from the function of cutting infrared light, such as light stabilizers, antioxidants, heat stabilizers, and antistatic agents.

[0103] · The solid-state imaging element (10) has an oxygen permeability of 5.0 cc / m² in a stacked structure located on the incident surface (14S) side with respect to the infrared light cut filter (13). 2 It may be a configuration with a permeability of / day / atm or less. For example, the laminated structure is another functional layer such as a planarization layer or an adhesion layer, and together with each microlens, its oxygen permeability is 5.0cc / m² 2 / day / atm or less is acceptable.

[0104] · The solid-state imaging element (10) may be equipped with a band-pass filter on the side of the incident plane of light for a plurality of micro-lenses. The band-pass filter is a filter that transmits only light having a specific wavelength of visible light and near-infrared light, and has a function similar to that of an infrared light cut filter (13). That is, the band-pass filter can cut off unnecessary infrared light that can be detected by each color photoelectric conversion element (11R, 11G, 11B). By doing so, the detection precision of visible light by each color photoelectric conversion element (11R, 11G, 11B) and the detection precision of near-infrared light having a wavelength of 850nm or 940nm band, which is the detection target of the infrared light photoelectric conversion element (11P), can be increased. Explanation of the symbols

[0105] 10: Solid-state imaging element 10F: Filter for solid-state image sensors 11: Photovoltaic conversion device 12R: Red filter 12G: Green filter 12B, 22B: Blue filters 12P, 22P: Infrared pass filter 13: Infrared light cut filter 13A, 23A: Infrared light cutting layer 13AH, 13BH: Through holes 13B, 23B: Protective layer 21B: Blue photoelectric conversion device 21P: Photoelectric conversion device for infrared light LM: Stripping solution RP: Resist Pattern

Claims

Claim 1 A method for manufacturing an infrared light cut filter comprising: forming an infrared light cut layer containing an infrared light absorbing pigment; forming a protective layer against a stripping solution on the infrared light cut layer; forming a resist pattern on the protective layer; patterning the protective layer and the infrared light cut layer by dry etching using the resist pattern; and stripping the resist pattern from the protective layer using the stripping solution. Claim 2 A method for manufacturing an infrared light cut filter according to claim 1, wherein the protective layer is formed by a resin having a cross-linked structure in which an epoxy group and a functional group reacting with the epoxy group are cross-linked. Claim 3 A method for manufacturing an infrared light cut filter, wherein the functional group is a phenolic hydroxyl group in paragraph 2. Claim 4 A method for manufacturing an infrared light cut filter according to claim 3, wherein forming the protective layer comprises forming the protective layer by an acrylic resin formed from a monomer comprising at least 4-hydroxyphenyl methacrylate and glycidyl methacrylate. Claim 5 A method for manufacturing an infrared light cut filter according to claim 4, wherein forming the protective layer comprises using 4-hydroxyphenyl methacrylate and glycidyl methacrylate to form the acrylic resin, wherein the total amount of acrylic monomers used to form the acrylic resin is 100 mass%, using 4-hydroxyphenyl methacrylate at least 20 mass% and glycidyl methacrylate at least 5 mass%. Claim 6 A method for manufacturing an infrared light cut filter according to claim 5, wherein forming the protective layer comprises forming the protective layer using an acrylic resin formed using a monomer capable of copolymerizing with one or both of 4-hydroxyphenyl methacrylate, glycidyl methacrylate, and 4-hydroxyphenyl methacrylate and glycidyl methacrylate. Claim 7 A method for manufacturing an infrared light cut filter according to claim 6, wherein the copolymerizable monomer is an acrylic monomer containing an aromatic ring. Claim 8 A method for manufacturing an infrared light cut filter according to claim 7, wherein peeling the resist pattern from the protective layer comprises using N-methylpyrrolidone or dimethyl sulfoxide as the peeling solution to peel the resist pattern from the protective layer. Claim 9 A filter for a solid-state imaging device comprising: a color filter including a red filter, a green filter, and a blue filter configured to be located on the incident side of light with respect to a first photoelectric conversion element; an infrared light pass filter configured to be located on the incident side of light with respect to a second photoelectric conversion element; and an infrared light cut filter located on the incident side of light with respect to the color filter, wherein the infrared light cut filter comprises an infrared light cut layer and a protective layer laminated on the infrared light cut layer and located on the incident side of light with respect to the infrared light cut layer. Claim 10 A solid-state imaging device comprising a first photoelectric conversion element, a second photoelectric conversion element, and a filter for a solid-state imaging device as described in claim 9.

Images