Solid-state imaging device and method for manufacturing the same

Abstract

To provide a solid state image sensor and a manufacturing method thereof that can improve the opening accuracy of an opening and realize a high-precision solid state image sensor without depending on the resolution of a pigment resist of a light-shielding layer.SOLUTION: There are provided a solid state image sensor and a manufacturing method thereof. The solid state image sensor includes: a semiconductor substrate having a plurality of photoelectric conversion elements which are two-dimensionally arranged; a first optical path layer provided on the first surface side of the semiconductor substrate; a second optical path layer provided on the surface of the first optical path layer opposite to the semiconductor substrate; a light-shielding layer provided between the first optical path layer and the second optical path layer; and a plurality of microlenses two-dimensionally arranged on the surface opposite to the light-shielding layer of the second optical path layer. In the light-shielding layer, an opening for securing an optical path for light incident on the photoelectric conversion element is formed along the thickness direction, and a pillar structure through which light can be transmitted is formed in the opening in the same shape as that of the opening.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a solid-state imaging device and a method for manufacturing a solid-state imaging device. [Background technology]

[0002] In an authentication device such as an optical fingerprint detection sensor, a fingerprint image is captured using a solid-state imaging element for biometric authentication. The solid-state imaging element includes a plurality of microlenses that collect external light and then allow it to enter the solid-state imaging element, a semiconductor substrate on which a plurality of photoelectric conversion elements are formed corresponding to the plurality of microlenses, an optical path layer that transfers the light emitted from the microlenses to the photoelectric conversion elements, and a light-shielding portion in which an opening is formed to ensure an optical path for the light incident on the photoelectric conversion elements. In the solid-state imaging element configured in this manner, an image of a subject such as a fingerprint or finger veins is formed, photoelectrically converted by the photoelectric conversion elements, and used for authentication.

[0003] For example, Patent Document 1 specifically discloses one form of the above-mentioned solid-state imaging element. In Patent Document 1, light in the optical path is collected by a microlens and then enters an opening formed in a light-shielding layer, and an optical image is formed at the opening of the image sensor. Meanwhile, the light in the optical path is blocked by the light-shielding layer. In this way, the light-shielding layer and the opening formed in the light-shielding layer block unnecessary light and allow necessary light to pass through. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-168118 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, high accuracy has been demanded for solid-state imaging devices, and therefore high accuracy is also required for openings that ensure an optical path for light necessary for photoelectric conversion. In solid-state imaging devices, openings are typically formed by patterning a light-shielding layer made of a pigment resist. When fabricating a light-shielding layer, various shapes of openings, such as minute openings, circles, or rectangles, are required depending on the actual situation. However, the resolution of the pigment resist used in the light-shielding layer can limit the opening pattern that can be formed. When attempting to form a minute opening pattern, for example, an opening pattern of 2 μm or less, the pigment resolution is insufficient, leaving residue in the opening that can obstruct the light path. It is difficult to achieve patterning that exceeds the resolution of the pigment by mask design or process adjustment alone. As a result, the resolution of the pigment in the light-shielding layer reduces the opening accuracy, resulting in a problem of reduced accuracy in the solid-state imaging device.

[0006] The present invention has been made to solve the above-mentioned problems, and aims to provide a solid-state imaging element and a method for manufacturing a solid-state imaging element that can improve the opening accuracy of the opening without relying on the resolution of the pigment resist of the light-shielding layer, thereby realizing a high-precision solid-state imaging element. [Means for solving the problem]

[0007] A solid-state imaging device according to a first embodiment of the present invention includes a semiconductor substrate having a plurality of photoelectric conversion elements arranged two-dimensionally, a first optical path layer provided on one first surface side of the semiconductor substrate, a second optical path layer provided on a surface of the first optical path layer opposite to the semiconductor substrate, a light-shielding layer provided between the first optical path layer and the second optical path layer, and a plurality of microlenses arranged two-dimensionally on a surface of the second optical path layer opposite to the light-shielding layer, wherein the light-shielding layer has an opening formed along a thickness direction to ensure an optical path of light incident on the photoelectric conversion elements, the light-shielding layer having a thickness of 1.0 μm or more, and in a cross section along the thickness direction and passing through the opening, a height dimension of the opening in the thickness direction is b, a minimum value of the opening dimension in a direction perpendicular to the thickness direction of the opening is a, and an aspect ratio α, which is the ratio of the height dimension to the opening dimension, b / a, is α, the opening dimension is 2 μm or less, and the aspect ratio α is 1 to 2.7, and the opening is formed of a photosensitive resist consists of, and A pillar structure that allows light to pass through is formed in the same shape as the opening.

[0008] In the solid-state imaging device described above, light-transmitting pillar structures are formed in the openings of the light-shielding layer in the same shape as the openings, and the pillar structures can function as openings that ensure an optical path for light from the microlenses to the photoelectric conversion elements. This makes it easier to form extremely minute pillar structures. As a result, minute openings can be realized. Furthermore, in the solid-state imaging device according to the present invention, pillar structures are formed in the openings, and the dimensions of the openings are determined by the pillar structures. This allows the openings to be formed without relying on the resolution of the pigment resist of the light-shielding layer.

[0009] The opening size may be constant throughout the thickness direction. With the above-described configuration, the opening can be easily formed.

[0010] The opening size may decrease with increasing distance from the semiconductor substrate in the thickness direction. With the above configuration, it is possible to suppress the incidence of scattered light on the light incident side.

[0011] The opening may be formed in a frustum shape. With the above configuration, the incident light can be amplified, and the light utilization efficiency can be improved.

[0012] The opening may be formed in a dome shape. With the above configuration, it is possible to collect light reflected below the light-shielding layer, thereby improving the light utilization efficiency.

[0013] The opening may have a structure in which a frustum shape and a cylindrical shape are stacked in this order from the semiconductor substrate side. With the above configuration, by making the opening cylindrical on the light incident side, the incidence of scattered light can be suppressed, and by making the opening frustum-shaped on the semiconductor substrate side, the incident light can be amplified.

[0014] Also, The aforementioned The photosensitive resist may be a positive resist. The pillar structure may have a thickness greater than that of the light-shielding layer when viewed in a cross section along the thickness direction. With the above configuration, the pillar structure protrudes slightly from the light-shielding layer, so that incident light can be collected more efficiently and light that becomes noise can be blocked.

[0015] In the method for manufacturing a solid-state imaging device for manufacturing the light-shielding layer according to the second aspect of the present invention, a photosensitive resist is formed so that an aspect ratio, which is a ratio of a height dimension to a width dimension of the pillar structure, is 1 to 2.7, or the width dimension is 2 μm. consists of, and a pillar structure forming step in which the pillar structure capable of transmitting light is formed; After the pillar structure forming step, the method includes a light-shielding layer forming step of forming the light-shielding layer to a thickness of 1.0 μm or more so as to include the pillar structure as a filler.

[0016] The light-shielding layer forming step may include a light-shielding material film forming step of forming a light-shielding material film so as to embed the pillar structure, and a light-shielding material film removing step of removing a predetermined thickness of the light-shielding material film so as to expose the pillar structure from an end face in a thickness direction of the light-shielding material film.

[0017] Furthermore, when the light-shielding material film is formed of a photosensitive material, the light-shielding material film removing step may include an exposure step of exposing the light-shielding material film with a mask having a predetermined pattern, and a development step of developing the light-shielding material film with a developer and removing a predetermined thickness of the light-shielding material film so as to expose the pillar structure from an end face of the light-shielding material film in a thickness direction.

[0018] Furthermore, when the light-shielding material film is made of a material that does not have photosensitivity, the light-shielding material film removing step may include a dry etching step of removing a predetermined thickness of the light-shielding material film by dry etching.

[0019] In addition, in the pillar structure forming step, a grayscale mask may be used to expose the photosensitive resist, and the pillar structure may be formed into a frustum shape whose width decreases with increasing distance from the semiconductor substrate in the height direction.

[0020] Furthermore, the pillar structure may have a layer configuration including at least a first layer and a second layer, and the pillar structure forming step may include a first pillar structure forming step of forming the first layer, and a second pillar structure forming step of forming the second layer so as to be stacked on the first layer after the first layer has hardened.

[0021] In the pillar structure forming step, the aspect ratio of the pillar structure may be controlled by increasing the temperature to a temperature near the glass transition temperature.

[0022] According to the above-described method for manufacturing a solid-state imaging device, the light-shielding layer is filled with pillar structures, which can function as openings that ensure an optical path for light from the microlens to the photoelectric conversion element. This makes it easier to form extremely small pillar structures, allowing for minute openings. Furthermore, because the openings are formed by the pillar structures rather than by patterning the light-shielding layer, the openings can be formed without relying on the resolution of the pigment resist of the light-shielding layer. Furthermore, the present invention allows for easier modification of the cross-sectional shape of the pillar structures compared to conventional techniques that directly form openings in the light-shielding layer. According to the above-described method for manufacturing a solid-state imaging device, the material for forming the light-shielding film does not necessarily have to be a photosensitive material, and a material having no photosensitivity may be used. When the light-shielding film is made of a material having no photosensitivity, the pillar structure can be exposed by removing a predetermined thickness of the light-shielding film by dry etching. [Effects of the Invention]

[0023] According to the solid-state imaging element and the method for manufacturing a solid-state imaging element of the above aspect of the present invention, the opening precision of the opening can be improved without depending on the resolution of the pigment resist of the light-shielding layer, and a high-precision solid-state imaging element can be realized. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a schematic diagram illustrating a configuration of a solid-state imaging device according to an embodiment of the present invention. [Figure 2] 3 is an enlarged view of an example of a cross-sectional shape of an opening of a light-shielding layer in a solid-state imaging device according to one embodiment of the present invention. FIG. [Figure 3] 10A and 10B are enlarged views of modified cross-sectional shapes of openings in a light-shielding layer in a solid-state imaging device according to one embodiment of the present invention. [Figure 4] 10A and 10B are enlarged views of modified cross-sectional shapes of openings in a light-shielding layer in a solid-state imaging device according to one embodiment of the present invention. [Figure 5]10A and 10B are enlarged views of modified cross-sectional shapes of openings in a light-shielding layer in a solid-state imaging device according to one embodiment of the present invention. [Figure 6] 1 is a flowchart showing a method for manufacturing a solid-state imaging device according to an embodiment of the present invention. [Figure 7A] 1A to 1C are schematic diagrams illustrating a manufacturing process of a solid-state imaging device according to an embodiment of the present invention. [Figure 7B] 1A to 1C are schematic diagrams illustrating a manufacturing process of a solid-state imaging device according to an embodiment of the present invention. [Figure 7C] 1A to 1C are schematic diagrams illustrating a manufacturing process of a solid-state imaging device according to an embodiment of the present invention. [Figure 7D] 1A to 1C are schematic diagrams illustrating a manufacturing process of a solid-state imaging device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinafter, a solid-state imaging device and a manufacturing method thereof according to the present invention will be described with reference to the drawings. The embodiments described here are the best modes for carrying out the invention, and the present invention is not limited to these embodiments. The drawings are schematic, and the relationship between the thickness of each layer and the planar dimensions, the thickness ratio of each layer, etc. may differ from the actual ones. Furthermore, the embodiments shown below exemplify configurations for embodying the technical idea of ​​the present invention, and the technical idea of ​​the present invention is not limited thereto.

[0026] <Configuration of solid-state imaging device> A solid-state imaging device according to one embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic diagram showing the configuration of a solid-state imaging device according to one embodiment of the present invention. First, a brief description will be given of each component of the solid-state imaging device 1 according to this embodiment. Fig. 1 also shows a subject S (for example, a fingerprint, finger veins, etc.). As shown in FIG. 1, the solid-state imaging element 1 of this embodiment includes, in this order from the opposite side of the subject S (the lower side in the figure), a semiconductor substrate 2, a first optical path layer 3, a light-shielding layer 4, a second optical path layer 5, and a microlens 6.

[0027] Specifically, in the solid-state imaging device 1 according to this embodiment, a first optical path layer 3 is provided on the first surface 2a side of the semiconductor substrate 2. A light-shielding layer 4 is provided on the first surface 3a (upper surface) of the first optical path layer 3 opposite to the semiconductor substrate 2. A second optical path layer 5 is provided on the first surface 4a (upper surface) of the light-shielding layer 4 opposite to the semiconductor substrate 2. A microlens 6 is provided on the first surface 5a (upper surface) of the second optical path layer 5 opposite to the semiconductor substrate 2.

[0028] Moreover, in the solid-state imaging device 1 according to this embodiment, a plurality of photoelectric conversion elements 21 are two-dimensionally arranged on the semiconductor substrate 2. Small openings 41 are formed in the light-shielding layer 4 so as to correspond to the plurality of photoelectric conversion elements 21, respectively. As shown in FIG. 2 , the plurality of openings 41 are formed so as to penetrate in the thickness direction of the light-shielding layer 4 from a first surface 4a to a second surface 4b opposite to the first surface 4a. A plurality of microlenses 6 are arranged two-dimensionally so as to correspond to the plurality of photoelectric conversion elements 21 and the plurality of openings 41. In the openings 41, pillar structures 42 having the same shape as the openings 41 are formed.

[0029] Each component of the solid-state imaging device 1 will now be described in detail. <Semiconductor substrate> 1, a plurality of photoelectric conversion elements 21 are two-dimensionally arranged on a semiconductor substrate 2 of a solid-state imaging device 1 according to this embodiment. The plurality of photoelectric conversion elements 21 have the function of converting incident light into an electrical signal. The semiconductor substrate 2 on which the photoelectric conversion elements 21 are formed is made of a material that transmits visible light and can withstand temperatures of at least about 300° C. Here, examples of materials that can be used for the semiconductor substrate 2 include Si, oxides such as SiO2, nitrides such as SiN, and materials containing Si, such as mixtures of these.

[0030] <First Optical Path Layer and Second Optical Path Layer> The first optical path layer 3 is formed on the first surface 2a of the semiconductor substrate 2. The second optical path layer 5 is formed above the semiconductor substrate 2. The first optical path layer 3 and the second optical path layer 5 can transmit light incident from the microlenses 6. The first optical path layer 3 and the second optical path layer 5 are formed so that the transmittance of the first optical path layer 3 and the second optical path layer 5 is preferably 90% or more, and more preferably 95% or more, for visible light having a wavelength of 400 nm or more and 700 nm or less.

[0031] <Microlens> The multiple microlenses 6 are two-dimensionally arranged above the semiconductor substrate 2 so as to correspond to the multiple photoelectric conversion elements 21, respectively. That is, the microlenses 6 are provided at positions corresponding to the respective photoelectric conversion elements 21. The microlenses 6 can compensate for a decrease in sensitivity of the photoelectric conversion elements 21 by focusing incident light that has entered the microlenses 6 onto each of the photoelectric conversion elements 21. The microlenses 6 are formed of a resin material containing one or more of, for example, acrylic resin, epoxy resin, polyimide resin, phenolic novolac resin, polyester resin, urethane resin, melamine resin, urea resin, styrene resin, and silicon resin. The microlenses 6 may also be formed of a substance other than an organic compound. Specifically, the microlenses 6 may be formed of a compound, oxide, or nitride containing at least one of silicon, carbon, oxygen, hydrogen, tin, zinc, indium, aluminum, gallium, titanium, molybdenum, tungsten, niobium, tantalum, hafnium, silver, and fluorine. Examples of compounds of these materials include ITO, ZnO, TiO2, and HfO2.

[0032] <Light blocking layer> The light-shielding layer 4 is made of a pigment resist. The light-shielding coloring material contained in the light-shielding layer 4 has absorptivity in the visible light wavelength region and the infrared region, and has a light-shielding function. In this embodiment, the resist is a coloring composition containing carbon or a pigment, and the light-shielding layer may be made of a material that has photosensitivity or a material that does not have photosensitivity.

[0033] For example, carbon black, titanium oxide, etc. can be used as the coloring material of the light-shielding layer 4. For example, azo dyes, anthraquinone dyes, phthalocyanine dyes, quinoneimine dyes, quinoline dyes, nitro dyes, carbonyl dyes, methine dyes, etc. can be used as the dye that can be contained in the light-shielding layer 4. One type of these light-shielding coloring materials may be used, or two or more types may be combined in an appropriate ratio.

[0034] 1, the light-shielding layer 4 is disposed between the first optical path layer 3 and the second optical path layer 5. Furthermore, the light-shielding layer 4 has minute openings 41 formed at positions corresponding to the plurality of microlenses 6 and the plurality of photoelectric conversion elements 21.

[0035] The light-shielding layer 4 has openings 41 formed therein, thereby ensuring an optical path for light incident on the photoelectric conversion element 21. Specifically, as shown in FIG. 1 , incident light L incident from the subject S side enters the microlens 6, is condensed by the microlens 6, passes through the second optical path layer 5, passes through the openings 41 formed in the light-shielding layer 4, and then enters the first optical path layer 3. Finally, the incident light L reaches the photoelectric conversion element 21 formed on the semiconductor substrate 2. As a result, the optical image of the subject S is photoelectrically converted into an electrical signal, which is used, for example, to authenticate personal information such as fingerprints. Meanwhile, a portion of the incident light incident from the subject S side is unnecessary light, which enters the microlens 6 and is condensed there, passes through the second optical path layer 5, and then reaches the area of ​​the light-shielding layer 4 other than the openings 41 (light-shielding area). Because the light-shielding layer 4 is made of a pigment resist having a light-shielding function, this portion of the incident light is blocked by the light-shielding layer 4 and does not enter the photoelectric conversion element 21.

[0036] In the solid-state imaging device 1 according to this embodiment, the thickness of the light-shielding layer 4 is 1.0 μm or more. In a cross section along the thickness direction (vertical direction in the figure) of the light-shielding layer 4 and passing through the opening 41, if the height dimension in the thickness direction of the opening 41 is b, the minimum opening dimension in the direction perpendicular to the thickness direction of the opening 41 (width direction, horizontal direction in the figure) is a, and the aspect ratio (opening aspect ratio) which is the ratio b / a of the height dimension to the opening dimension is α, then the opening dimension is 2 μm or less, or the aspect ratio α is 1 or more and 2.7 or less.

[0037] Furthermore, pillar structures 42 having the same shape as the openings 41 are formed in the openings 41. The pillar structures 42 are formed of a material separate from the light-shielding layer 4. The pillar structures 42 are made of a light-transmittable material and are composed of a photosensitive resist. Furthermore, in this embodiment, a positive resist is used as the photosensitive resist. In the solid-state imaging device 1 according to this embodiment, the cross-sectional shape of the pillar structure 42, which is the cross-sectional shape of the opening 41, can be set arbitrarily according to actual requirements.

[0038] 2 is an enlarged cross-sectional view of an example of the opening 41 of the light-shielding layer 4 in a solid-state imaging device according to one embodiment of the present invention. As shown in FIG. 2, the opening 41 is formed in a cylindrical shape with a constant opening dimension in the width direction throughout the thickness direction. The height dimension in the thickness direction of the light-shielding layer 4 is the same as the height dimension in the thickness direction of the pillar structure 42.

[0039] The solid-state imaging device 1 according to this embodiment has the above-described components, and thus can achieve the following effects. In the solid-state imaging device 1 according to the present invention, light-transmitting pillar structures 42 having the same shape as the openings 41 are formed in the openings 41 of the light-shielding layer 4. The pillar structures 42 can function as the openings 41 that ensure an optical path for light from the microlenses 6 to the photoelectric conversion elements 21, making it easy to form the pillar structures 42 extremely minute. This allows for the realization of minute openings 41.

[0040] Furthermore, pillar structures 42 are formed in the openings 41, and the dimensions of the openings 41 are defined by the pillar structures 42. This allows the openings 41 to be formed without depending on the resolution of the pigment resist of the light-shielding layer 4. Furthermore, when the thickness of the light-shielding layer 4 is 1.0 μm or more, and in a cross section along the thickness direction of the light-shielding layer 4 and passing through the opening 41, the height dimension of the opening 41 in the thickness direction is b, the minimum value of the opening dimension in the direction perpendicular to the thickness direction of the opening 41 is a, and the aspect ratio, which is the ratio b / a of the height dimension to the opening dimension, is α, the opening dimension is 2 μm or less, or the aspect ratio α is 1 to 2.7. By setting the dimensions in this manner, it is possible to form minute openings 41 with high precision. When the components have the dimensions described above, the effect of the pillar structure 42 of the present invention is remarkable.

[0041] By forming the opening dimension a to be constant across the thickness direction of the light-shielding layer 4, the opening 41 can be easily formed.

[0042] The shape of the opening 41 is not limited to the cylindrical shape shown in Fig. 2. For example, the opening 41a may be formed in a frustum shape as shown in Fig. 3. Specifically, the opening dimension in the width direction of the opening 41a is formed to decrease from the second surface 4b on the semiconductor substrate 2 side toward the first surface 4a in the thickness direction. 3, the size of the opening 41a is made smaller in the thickness direction with increasing distance from the semiconductor substrate 2, thereby suppressing the incidence of scattered light on the light incident side. Furthermore, by forming the opening 41a in a frustum shape, the incident light can be amplified, thereby improving the light utilization efficiency.

[0043] 4, the opening 41b may be formed in a dome shape. Specifically, the opening dimension of the opening 41b on the second surface 4b side, which is closer to the semiconductor substrate 2, is larger than the opening dimension on the first surface 4a side, which is closer to the semiconductor substrate 2. Furthermore, the opening 41b is curved from the first surface 4a toward the second surface 4b. As shown in FIG. 4, by forming the opening 41b in a dome shape, it is possible to collect light reflected by the first optical path layer 3 and the semiconductor substrate 2 arranged on the second surface 4b side of the light-shielding layer 4, thereby improving the light utilization efficiency.

[0044] 5, the opening 41c may have a structure in which a frustum-shaped opening 41c1 and a cylindrical opening 41c2 are stacked in this order from the second surface 4b toward the first surface 4a. The opening dimension in the width direction of the opening 41c1 is formed to decrease from the second surface 4b toward the first surface 4a of the semiconductor substrate 2 to approximately the center in the thickness direction. The opening dimension of the opening 41c2 is constant throughout the thickness direction from approximately the center of the light-shielding layer 4 toward the first surface 4a. 5, opening 41c has a structure in which a frustum-shaped opening 41c1 and a cylindrical opening 41c2 are stacked in this order from the semiconductor substrate 2 side, and by providing cylindrical opening 41c2 on the light incident side (subject S side), it is possible to suppress the incidence of scattered light. Furthermore, by providing frustum-shaped opening 41c2 on the semiconductor substrate 2 side, it is possible to amplify the incident light and improve the light utilization efficiency.

[0045] 2 to 5, the height dimension of the openings 41, 41a to 41c in the thickness direction of the light-shielding layer 4 is the same as the height dimension of the pillar structures 42 in the thickness direction, but this is not limited to this. For example, the pillar structures 42 may be configured so that the light-shielding layer 4 protrudes from at least one of the first surface 4a and the second surface 4b. In other words, the height dimension (film thickness) of the pillar structures 42 in the thickness direction may be greater than the height dimension of the light-shielding layer 4 in the thickness direction. In this way, the pillar structures 42 protrude from at least one of the first surface 4a and the second surface 4b of the light-shielding layer 4, thereby enabling the incident light L to be efficiently collected onto the photoelectric conversion element 21. Furthermore, light that becomes noise can be blocked.

[0046] <Method of manufacturing a solid-state imaging device> Next, a method for manufacturing a solid-state imaging device will be described with reference to FIGS. In the manufacturing method of the solid-state imaging element 1 according to the present invention, known methods can be used to manufacture the semiconductor substrate 2, the first optical path layer 3, the second optical path layer 5, and the microlenses 6. Therefore, detailed explanations thereof will be omitted below, and only the parts of the manufacturing method that have distinctive features compared to the prior art will be described.

[0047] FIG. 6 is a flowchart showing a method for manufacturing a solid-state imaging device according to one embodiment of the present invention. The method for manufacturing a solid-state imaging device 1 of the present invention forms pillar structures 42 so that the aspect ratio (pillar aspect ratio), which is the ratio of the height dimension to the width dimension of the pillar structures 42, is 1 or more and 2.7 or less, or the width dimension is 2 μm. Specifically, the method for manufacturing a solid-state imaging device of the present invention mainly includes a pillar structure forming step S1 in which the light-transmittable pillar structures 42 are formed using a photosensitive resist, and a light-shielding layer forming step S2 in which, after the pillar structure forming step S1, a light-shielding layer 4 is formed to a thickness of 1.0 μm or more so as to contain the pillar structures 42 as a filler.

[0048] 7A to 7D are schematic diagrams showing the pillar structure forming step S1 and the light-shielding layer forming step S2. First, the pillar structure forming step S1 will be described with reference to FIGS. 7A and 7B. The pillar structure formation step S1 mainly includes a step of forming a photosensitive resist film 46, as shown in FIG. 7A, and a step of removing predetermined portions of the photosensitive resist film 46 to leave only the pillar structure, as shown in FIG. 7B.

[0049] Next, an example of the pillar structure forming step S1 will be specifically described. In the method for manufacturing the solid-state imaging device 1 of the present invention, a positive resist is used as the photosensitive resist, but a negative resist may also be used. The pillar structure formation step S1 includes, for example, a coating step of coating a substrate 45 with photosensitive resist, a drying step of rotating the substrate 45 to dry the coated photosensitive resist and form a photosensitive resist film 46, a pre-bake process of pre-baking the photosensitive resist film 46, an exposure step of exposing the pre-baked photosensitive resist film 46 with a mask having a predetermined pattern, a development step of developing the photosensitive resist film 46 with a developer to leave only predetermined portions as pillar structures 42, a cleaning step of cleaning the substrate 45 on which the pillar structures 42 remain, a drying step of rotating the substrate 45 to dry it, and a hard bake step of post-baking the pillar structures 42 to hard bake them. In the method for manufacturing the solid-state imaging device 1 of the present invention, the photosensitive resist is exposed using a circular mask, and cylindrical photosensitive resist film 46a is left as pillar structures 42 as shown in FIG.

[0050] Also, a method for forming the pillar structure shown in FIGS. 3 to 5 will be described. First, a case where the opening 41a has a frustum shape as shown in FIG. 3 will be described. In the pillar structure formation step S1, the photosensitive resist is exposed using a grayscale mask. In this way, the pillar structure is formed into a frustum shape whose width decreases with increasing distance from the semiconductor substrate 2 in the height direction of the light-shielding layer 4. This allows the formation of a pillar structure 42 whose cross section is frustum-shaped, as shown in FIG.

[0051] Next, a case where the opening 41b is dome-shaped as shown in FIG. 4 will be described. In the pillar structure formation step S1, the aspect ratio of the pillar structure is controlled by increasing the temperature to a temperature near the glass transition temperature. Specifically, in the hard bake step, the aspect ratio of the pillar structure is controlled by increasing the temperature to a temperature near the glass transition temperature, for example, 140°C. By increasing the temperature in this manner, a pillar structure 42 having a dome-shaped cross section can be formed, as shown in FIG.

[0052] Next, the pillar structure 42 shown in FIG. 5 will be described. The pillar structure forming step S1 is configured to include a first pillar structure forming step of forming a first layer (first pillar structure) having the same shape as the frustum-shaped opening 41c1, and a second pillar structure forming step of forming, after hardening the first layer, a second layer (second pillar structure) having the same shape as the cylindrical opening 41c2 so as to be stacked on the first layer. The pillar structure 42 formed in this manner has a stacked configuration including at least the first layer and the second layer. As a result, as shown in FIG. 5, it is possible to form the pillar structure 42 in which the first pillar structure having the same cross-sectional shape as the frustum-shaped opening 41c1 and the second pillar structure having the same cross-sectional shape as the cylindrical opening 41c2 are stacked. The shapes of the first and second layers are not limited to these. Also, although the configuration in which two layers are stacked has been described, three or more layers may be used.

[0053] Next, an example of the light-shielding layer forming step S2 will be specifically described. The light-shielding layer forming step S2 mainly includes a light-shielding material film forming step of forming a light-shielding material film 47 so as to bury the pillar structures 42, as shown in FIG. 7C, and a light-shielding material film removing step of removing a predetermined thickness of the light-shielding material film 47 so as to expose the pillar structures 42 from the light-shielding material film 47, as shown in FIG. 7D. As an example, the light-shielding layer forming step S2 specifically includes: an application step of applying a light-shielding material so as to embed the pillar structures 42; a drying step of drying the applied light-shielding material to form a light-shielding material film 47; a pre-bake step of pre-baking the light-shielding material film 47; and a light-shielding material film removal step of removing a predetermined thickness of the light-shielding material film 47 so as to expose the pillar structures 42 from the light-shielding material film 47.

[0054] When the light-shielding material film 47 is made of a photosensitive material, the light-shielding material film removal step includes an exposure step of exposing the light-shielding material film 47 with a mask having a predetermined pattern, and a development step of developing the light-shielding material film 47 with a developer to remove a predetermined thickness of the light-shielding material film 47 so as to expose the pillar structures 42 from the light-shielding material film 47. When the light-shielding material film 47 is made of a material that does not have photosensitivity, the light-shielding material film removing step includes a dry etching step of removing a predetermined thickness of the light-shielding material film 47 by dry etching. The pillar structure forming step S1 and the light-shielding layer forming step S2 have been described above as examples, but these are presented as examples. First, the pillar structure 42 is formed, then the light-shielding layer 4 is formed so as to include the pillar structure 42, and finally, a predetermined thickness of the light-shielding layer 4 is removed so as to expose the pillar structure 42. Specific steps are not limited to these.

[0055] In the manufacturing method of the solid-state imaging element of the present invention, as shown in Figures 7A to 7D, pillar structures 42 are formed, and then a light-shielding layer 4 is formed so as to include the pillar structures 42 as a filler, and the following effects and advantages can be obtained. The light-shielding layer 4 is filled with pillar structures 42, which can function as openings 41 that ensure an optical path for light from the microlenses 6 to the photoelectric conversion elements 21. This makes it easy to form the pillar structures 42 extremely minute, and as a result, it is possible to realize minute openings. In contrast, in conventional techniques, a light-shielding layer is formed first, and then an opening is opened in the light-shielding layer. In this case, it is not possible to form a minute opening, and even if a minute opening is formed, there is a possibility that residue of the light-shielding layer remains around the opening, making it impossible to achieve a highly accurate opening. Therefore, the present invention can more reliably form a highly accurate minute opening compared to conventional techniques.

[0056] The opening 41 of the present invention is not formed by patterning the light-shielding layer 4 but is realized by the pillar structure 42, so that the opening 41 can be formed without depending on the resolution of the pigment resist of the light-shielding layer 4. Furthermore, compared to when openings are formed directly in the light-shielding layer 4, the cross-sectional shape of the pillar structure 42 can be easily changed. The material for forming the light-shielding material film 47 does not necessarily have to be a photosensitive material, and a non-photosensitive material may also be used. When the light-shielding material film is made of a non-photosensitive material, the pillar structures 42 can be exposed by removing a predetermined thickness of the light-shielding material film by dry etching. Furthermore, the pillar structure 42 is formed using a photosensitive resist so that the aspect ratio, which is the ratio of the height dimension to the width dimension of the pillar structure 42, is between 1 and 2.7, or so that the width dimension is 2 μm. By setting the dimensions of the pillar structure 42 in this manner, it is possible to form a highly accurate micro-aperture.

[0057] Although one embodiment of the solid-state imaging device and its manufacturing method of the present invention has been described above, the embodiment is presented by way of example and is not intended to limit the scope of the invention. The novel embodiment can be embodied in various other forms, and various omissions, substitutions, and modifications of components can be made without departing from the spirit of the invention. These embodiments and modifications thereof are intended to be included within the scope and spirit of the invention, and are similarly included within the scope of the invention and its equivalents as defined in the appended claims. [Explanation of symbols]

[0058] 1...Solid-state image sensor 2...Semiconductor substrate 3...First optical path layer 4...Light blocking layer 5...Second optical path layer 6...Microlens 21...Photoelectric conversion element 41...Opening 42...Pillar structure 47...Light-shielding material film

Claims

1. a semiconductor substrate having a plurality of photoelectric conversion elements arranged two-dimensionally; a first optical path layer provided on a first surface side of the semiconductor substrate; a second optical path layer provided on a surface of the first optical path layer opposite to the semiconductor substrate; a light-shielding layer provided between the first optical path layer and the second optical path layer; a plurality of microlenses arranged two-dimensionally on a surface of the second optical path layer opposite to the light-shielding layer, the light-shielding layer has an opening formed along a thickness direction thereof to ensure an optical path of light incident on the photoelectric conversion element; the thickness of the light-shielding layer is 1.0 μm or more, In a cross section along the thickness direction and passing through the opening, when a height dimension of the opening in the thickness direction is b, a minimum value of the opening dimension in a direction perpendicular to the thickness direction of the opening, and an aspect ratio b / a, which is the ratio of the height dimension to the opening dimension, is α, the opening dimension is 2 μm or less, and the aspect ratio α is 1 or more and 2.7 or less, In the opening, a pillar structure made of photosensitive resist and capable of transmitting light is formed in the same shape as the opening.

2. The opening size is constant throughout the thickness direction. The solid-state imaging device according to claim 1 .

3. the opening size decreases with increasing distance from the semiconductor substrate in the thickness direction; The solid-state imaging device according to claim 1 .

4. The opening is formed in a frustum shape. The solid-state imaging device according to claim 3 .

5. The opening is formed in a dome shape. The solid-state imaging device according to claim 3 .

6. The opening has a structure in which a frustum shape and a cylindrical shape are stacked in this order from the semiconductor substrate side. The solid-state imaging device according to claim 3 .

7. The photosensitive resist is a positive resist. The solid-state imaging device according to claim 1 .

8. the pillar structure has a thickness greater than that of the light-shielding layer in a cross-sectional view along the thickness direction; The solid-state imaging device according to claim 1 .

9. a pillar structure forming step in which the pillar structure is made of photosensitive resist and is light transmissive so that the aspect ratio, which is the ratio of the height dimension to the width dimension of the pillar structure, is 1 to 2.7, or the width dimension is 2 μm; and a light-shielding layer forming step of forming the light-shielding layer to a thickness of 1.0 μm or more so as to include the pillar structure as a filler after the pillar structure forming step. A method for manufacturing the solid-state imaging device according to claim 1 .

10. The light-shielding layer forming step includes: a light-shielding material film forming step of forming a light-shielding material film so as to embed the pillar structure; a light-shielding material film removing step of removing a predetermined thickness of the light-shielding material film so as to expose the pillar structure from an end surface of the light-shielding material film in a thickness direction thereof, The method for manufacturing a solid-state imaging device according to claim 9 .

11. When the light-shielding material film is formed of a photosensitive material, the light-shielding material film removing step teeth, an exposure step of exposing the light-shielding material film to light using a mask having a predetermined pattern; a developing step of developing the light-shielding material film with a developer to remove a predetermined thickness of the light-shielding material film so as to expose the pillar structure from an end surface of the light-shielding material film in a thickness direction. The method for manufacturing a solid-state imaging device according to claim 10.

12. When the light-shielding material film is made of a material that does not have photosensitivity, the light-shielding material film removing step includes: a dry etching step of removing a predetermined thickness of the light-shielding material film by dry etching; The method for manufacturing a solid-state imaging device according to claim 10.

13. In the pillar structure forming step, a photosensitive resist is exposed using a grayscale mask, and the pillar structure is formed into a frustum shape whose width dimension decreases with increasing distance from the semiconductor substrate in a height direction. The method for manufacturing a solid-state imaging device according to claim 9 .

14. the pillar structure has a layer configuration including at least a first layer and a second layer, The pillar structure forming step includes a first pillar structure forming step of forming the first layer, and a second pillar structure forming step of forming the second layer so as to be stacked on the first layer after the first layer is hardened. The method for manufacturing a solid-state imaging device according to claim 9 .

15. In the pillar structure forming step, the aspect ratio of the pillar structure is controlled by increasing the temperature to a temperature near the glass transition temperature. The method for manufacturing a solid-state imaging device according to claim 9 .

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