Solid-state imaging device and method for manufacturing the same

Abstract

To provide a solid-state imaging element and a manufacturing method thereof that can reduce the light that becomes noise in the solid-state imaging pixel, and can realize a high-precision solid-state imaging element.SOLUTION: A solid-state imaging element includes a semiconductor substrate having a plurality of photoelectric conversion elements arranged two-dimensionally, a first optical path layer, a second optical path layer, 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. When the height dimension in the thickness direction of an opening is b, the minimum value of the opening dimension in the direction orthogonal to the thickness direction of the opening is a, and the aspect ratio which is the ratio b / a of the height dimension to the opening dimension, is α, α≥1 and a≥3 μm are satisfied, a pillar structure through which light can be transmitted is formed in the same shape as the opening, and a photosensitive resist constituting the pillar structure is a negative type resist.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 authentication. The solid-state imaging element includes a semiconductor substrate having a plurality of photoelectric conversion elements arranged two-dimensionally, a plurality of microlenses provided corresponding to the plurality of photoelectric conversion elements and condensing external light to make it incident on the photoelectric conversion elements, an optical path layer that transfers the light emitted from the microlenses to the photoelectric conversion elements, and a light-shielding layer in which openings are formed to allow the light incident on the photoelectric conversion elements to pass (see, for example, Patent Document 1).

[0003] Alignment marks are formed in suitable locations on such solid-state imaging devices, and these alignment marks are used, for example, to align a photomask used when forming openings in a light-shielding layer. When irradiated with light from a light source, there is a difference between the light transmitted through or reflected from the locations where the alignment marks are formed and the light transmitted through or reflected from the locations where the alignment marks are not formed, and this difference is detected by an optical sensor to identify the position of the alignment mark. [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] Fingerprint detection sensors need to be enlarged to increase the amount of light received by the photoelectric conversion element. However, at the same time, light from other than the desired optical path (the optical path of light useful for fingerprint detection) also increases as noise, resulting in reduced detection accuracy. To reduce the light that becomes noise, it is necessary to increase the thickness of the light-shielding layer and improve alignment accuracy. However, the material used for the light-shielding layer must have light-shielding properties, and may block light from the light source used for alignment, potentially reducing alignment accuracy. Furthermore, the same problem occurs when the light-shielding layer is made thicker to improve light-shielding properties.

[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 reduce light that becomes noise in solid-state imaging pixels and realize a high-precision solid-state imaging element. [Means for solving the problem]

[0007] A solid-state imaging device according to a first aspect of the present invention comprises 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 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 the light-shielding layer. The light-shielding layer has an opening that ensures an optical path for light incident on the photoelectric conversion element, formed at a position corresponding to the photoelectric conversion element; in a cross section along the thickness direction of the light-shielding layer and passing through the opening, when b is the height dimension of the opening in the thickness direction and a is the minimum value of the opening dimension in a direction perpendicular to the thickness direction of the opening and α is an aspect ratio, which is the ratio b / a of the height dimension to the opening dimension, α≧1 and a≧3 μm; in the opening, a light-transmittable pillar structure is formed in the same shape as the opening; and the photosensitive resist that constitutes the pillar structure is a negative resist.

[0008] According to the above-described solid-state imaging device, the openings in the light-shielding layer are configured to have an opening dimension a≧3 μm in a direction perpendicular to the thickness direction of the light-shielding layer, i.e., a minimum dimension of 3 μm, and an aspect ratio α of 1 or more, thereby making the light-shielding plate thicker for openings having predetermined opening dimensions. By making the light-shielding layer thicker, it is possible to reliably block light, thereby suppressing light transmission through non-opening portions of the light-shielding layer and reducing light that becomes noise in the solid-state imaging device.

[0009] Furthermore, in the above-described solid-state imaging device, 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 function as openings that ensure an optical path for light from the microlenses to the photoelectric conversion elements. Because the pillar structures can be easily formed to be extremely small or elongated, the openings can be easily formed even if the thickness of the light-shielding layer is increased to make the openings elongated. 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, so that the openings can be formed without relying on the resolution of the pigment resist of the light-shielding layer.

[0010] The pillar structure may have a height equal to the total thickness of the first optical path layer, the second optical path layer, and the light-shielding layer. After forming the plurality of pillar structures configured in this manner, the first optical path layer, the light-shielding layer, and the second optical path layer can be laminated in this order on the substrate on which the pillar structures are formed by spray coating, printing, etc., and each layer can be easily formed. Furthermore, when forming each layer, the pillar structures can be used as a positioning reference.

[0011] The pillar structure may have the same height as the film thickness of the light-shielding layer.

[0012] The solid-state imaging element may include an effective pixel area in which a plurality of pixels for photosensitive imaging are arranged, and an alignment mark may be provided on the periphery of the effective pixel area, and the height of the alignment mark may be formed so as not to be lower than the upper surface of the light-shielding layer. By providing alignment marks in solid-state imaging elements, accurate alignment can be achieved when forming each layer. In particular, by aligning the photomask used when forming the openings, the precision with which the openings are formed can be improved, allowing only the effective light useful for imaging to pass through the openings, thereby reducing the light that becomes noise.

[0013] The alignment mark may be made of the same material as the pillar structure. With this configuration, the alignment marks can be formed in a single process in which the pillar structures are formed, thereby simplifying the process.

[0014] A method for manufacturing a solid-state imaging device according to a second aspect of the present invention is a method for manufacturing the above-mentioned solid-state imaging device, and includes a pillar structure forming step in which the pillar structure, which is light-transmitting, is formed using a negative photosensitive resist so that the aspect ratio, which is the ratio of the height dimension to the width dimension of the pillar structure, is 1 or more and the width dimension is 3 μm or more, and a light-shielding layer forming step in which the light-shielding layer is formed after the pillar structure forming step so as to contain the pillar structure as a filler.

[0015] The method for manufacturing a solid-state imaging device according to the second aspect of the present invention may include, after forming the light-shielding layer, removing a predetermined thickness of the light-shielding layer so as to expose the pillar structure from the light-shielding layer, and forming the pillar structure to the same height as the film thickness of the light-shielding layer.

[0016] A method for manufacturing a solid-state imaging device according to another embodiment of the present invention may further include a step of forming a first optical path layer and a second optical path layer by sequentially stacking the first optical path layer, the light-shielding layer, and the second optical path layer so as to contain at least a portion of the pillar structure as a filler, and after forming the first optical path layer, the light-shielding layer, and the second optical path layer by sequentially stacking them, a predetermined thickness of the second optical path layer may be removed so as to expose the pillar structure from the second optical path layer, and the pillar structure may be formed to a height equal to the total film thickness of the first optical path layer, the second optical path layer, and the light-shielding layer.

[0017] When the first optical path layer, the light-shielding layer, and the second optical path layer are stacked in order to form the first optical path layer, the light-shielding layer, and the second optical path layer, the pillar structure may be used as a positioning reference for the first optical path layer, the light-shielding layer, and the second optical path layer.

[0018] The method may further include an alignment mark forming step of providing an alignment mark on the periphery of an effective pixel area of ​​the solid-state imaging device, and the height of the alignment mark may be formed so as not to be lower than the upper surface of the light-shielding layer. [Effects of the Invention]

[0019] According to the solid-state imaging device and the method for manufacturing the solid-state imaging device of the present invention, it is possible to reduce light that becomes noise in the solid-state imaging device, and to realize a high-precision solid-state imaging device. [Brief explanation of the drawings]

[0020] [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 2A] 3A and 3B are diagrams illustrating an example of a cross-sectional shape of an opening in a light-shielding layer in a solid-state imaging device according to one embodiment of the present invention. [Figure 2B] 3A and 3B are diagrams illustrating an example of a cross-sectional shape of an opening in a light-shielding layer in a solid-state imaging device according to one embodiment of the present invention. [Figure 2C] 3A and 3B are diagrams illustrating an example of a cross-sectional shape of an opening in a light-shielding layer in a solid-state imaging device according to one embodiment of the present invention. [Figure 2D] 3A and 3B are diagrams illustrating an example of a cross-sectional shape of an opening in a light-shielding layer in a solid-state imaging device according to one embodiment of the present invention. [Figure 3] FIG. 2 is a plan view showing the positions at which alignment marks are formed in the solid-state imaging device according to the embodiment of the present invention. [Figure 4] FIG. 4 is a schematic diagram showing the configuration of a solid-state imaging device according to a second embodiment of the present invention. [Figure 5] 3 is a flowchart showing a method for manufacturing the solid-state imaging device according to the first embodiment of the present invention. [Figure 6A] 1A to 1C are schematic views showing a process for manufacturing a solid-state imaging device according to a first embodiment of the present invention. [Figure 6B] 1A to 1C are schematic views showing a process for manufacturing a solid-state imaging device according to a first embodiment of the present invention. [Figure 6C] 1A to 1C are schematic views showing a process for manufacturing a solid-state imaging device according to a first embodiment of the present invention. [Figure 6D] 1A to 1C are schematic views showing a process for manufacturing a solid-state imaging device according to a first embodiment of the present invention. [Figure 7] 10 is a flowchart showing a method for manufacturing a solid-state imaging device according to a second embodiment of the present invention. [Figure 8A] 5A to 5C are schematic diagrams illustrating a process for manufacturing a solid-state imaging device according to a second embodiment of the present invention. [Figure 8B] 5A to 5C are schematic diagrams illustrating a process for manufacturing a solid-state imaging device according to a second embodiment of the present invention. [Figure 8C] 5A to 5C are schematic diagrams illustrating a process for manufacturing a solid-state imaging device according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] A solid-state imaging device and a manufacturing method thereof according to the present invention will be described below 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.

[0022] <Overall configuration of solid-state imaging device> The solid-state imaging device of the present invention includes a semiconductor substrate having a plurality of photoelectric conversion elements arranged two-dimensionally, a first optical path layer formed on one side of the semiconductor substrate, a second optical path layer formed on the surface of the first optical path layer opposite the semiconductor substrate, a light-shielding layer formed between the first optical path layer and the second optical path layer, and a plurality of microlenses arranged two-dimensionally on the surface of the second optical path layer opposite the light-shielding layer. The light-shielding layer has openings formed at positions corresponding to the photoelectric conversion elements to ensure an optical path for light incident on the photoelectric conversion elements. In a cross section along the thickness direction of the light-shielding layer and passing through the openings, the height dimension of the openings in the thickness direction is b, the minimum opening dimension in a direction perpendicular to the thickness direction of the openings is a, and the aspect ratio, b / a, of the height dimension to the opening dimension is α, where α≧1 and a≧3 μm. Furthermore, light-transmitting pillar structures are formed in the openings in the same shape as the openings, and the photosensitive resist constituting the pillar structures is a negative resist.

[0023] The solid-state imaging element of the present invention includes an effective pixel area in which a plurality of pixels for photosensitive imaging are arranged, and an alignment mark is provided on the periphery of the effective pixel area, and the height of the alignment mark is formed so as not to be lower than the upper surface of the light-shielding layer.

[0024] Hereinafter, specific embodiments of the solid-state imaging device according to the present invention will be described in detail with reference to the drawings. <Solid-state imaging device of the first embodiment> A solid-state imaging device according to a first embodiment of the present invention will be described with reference to Fig. 1 to Fig. 3. Fig. 1 is a schematic diagram showing the configuration of a solid-state imaging device according to the first embodiment of the present invention. First, each component of a solid-state imaging device 1 according to this embodiment will be described in brief. As shown in FIG. 1, the solid-state imaging element 1 according to this embodiment includes, in this order from the side farthest from 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.

[0025] 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 (upper surface) 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.

[0026] 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, and minute openings 41 are formed in the light-shielding layer 4 so as to correspond to each of the plurality of photoelectric conversion elements 21. 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 the first surface 4a to the 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. A pillar structure made of a negative photosensitive resist that is light transmissive is formed in the openings 41.

[0027] 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.

[0028] <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.

[0029] <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.

[0030] <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.

[0031] 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.

[0032] 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.

[0033] 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 light is blocked by the light-shielding layer 4 and does not enter the photoelectric conversion element 21.

[0034] 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 of the light-shielding layer 4 (the vertical direction in the drawing) and passing through the opening 41, the height dimension of the opening 41 in the thickness direction is b, the minimum opening dimension in the direction perpendicular to the thickness direction of the opening 41 (the width direction, the horizontal direction in the drawing) is a, and the aspect ratio b / a, which is the ratio of the height dimension to the opening dimension, is α. In this case, a≧3 μm and α≧1 are satisfied.

[0035] 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. Several specific examples of the cross-sectional shape of the opening 41 will be shown below.

[0036] 2A to 2D show examples of the cross-sectional shape of an opening in a light-shielding layer of a solid-state imaging device. As shown in Fig. 2A, opening 41 is formed in a cylindrical shape with a constant width across the thickness. The height of light-shielding layer 4 in the thickness direction is the same as the height of pillar structure 42 in the thickness direction.

[0037] The shape of the opening 41 is not limited to the cylindrical shape shown in Fig. 2A. For example, as shown in Fig. 2B, the opening 41a may be formed in a frustum shape. Specifically, the opening dimension (opening area) in the width direction of the opening 41a increases from the second surface 4b on the semiconductor substrate 2 side toward the first surface 4a in the thickness direction. 2B, opening 41a may be formed so that the opening dimension of opening 41a increases in the thickness direction as it moves away from semiconductor substrate 2. That is, as shown in FIG. 2B, opening 41a can be formed in an inverted frustum shape.

[0038] 2C, the opening 41c may have a structure in which an inverted 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 (opening area) of the opening 41c1 in the width direction increases 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. As shown in FIG. 2C, opening 41c has a structure in which an inverted truncated pyramid-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), the incidence of scattered light can be suppressed.

[0039] 2D, the opening 41d may have a structure in which a frustum-shaped opening 41d1 and a cylindrical opening 41d2 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 41d1 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 41d2 is constant throughout the thickness direction from approximately the center of the light-shielding layer 4 toward the first surface 4a. As shown in Fig. 2D, the opening 41d has a structure in which a frustum-shaped opening 41d1 and a cylindrical opening 41d2 are stacked in this order from the semiconductor substrate 2 side, and the cylindrical opening 41d2 is provided on the light incident side (subject S side), thereby suppressing the incidence of scattered light. Furthermore, by providing the frustum-shaped opening 41d1 on the semiconductor substrate 2 side, the incident light is amplified and the utilization of light is improved. efficiency can be increased.

[0040] <Pillar structure> In the opening 41, a pillar structure 42 is formed as a separate member having the same shape as the opening 41. The pillar structure 42 is made of a light-transmitting material, and is made of a negative photosensitive resist. For example, linear phenolic resin or polymethyl methacrylate can be used for the pillar structure 42. As shown in FIG. 1 , the pillar structure 42 in this embodiment has the same height as the film thickness of the light-shielding layer 4.

[0041] <Alignment mark> 3 is a plan view showing the positions of alignment marks in a solid-state imaging device according to this embodiment. When manufacturing a solid-state imaging device, a large number of solid-state imaging devices are formed and aligned on a single substrate, and then each solid-state imaging device is separated from the others. FIG. 3 shows the solid-state imaging device 1 in an unseparated state after it has been manufactured, with a total of four solid-state imaging devices 1 arranged in a 2x2 matrix in the figure.

[0042] In this embodiment, as shown in FIG. 3, the solid-state imaging element has an effective pixel area 11 in which a plurality of pixels that perform photosensitive imaging are arranged, and a frame area 12 that surrounds this effective pixel area, and an alignment mark 7 is provided in this frame area 12. The alignment mark 7 may also be provided in a region between the solid-state imaging elements. In either case, the alignment mark 7 is provided on the periphery of the effective pixel region 11, and it is sufficient if it can fulfill the role of alignment.

[0043] FIG. 3 shows that the alignment mark 7 is provided in the frame region 12. FIG. 1 shows that the height of the alignment mark 7 is approximately flush with the upper surface of the light-shielding layer. The height of the alignment mark 7 does not have to be lower than the upper surface 4a of the light-shielding layer 4, and it may be higher than the upper surface 4a of the light-shielding layer 4. This ensures that the alignment mark 7 is exposed from the light-shielding layer 4 even if a light-shielding layer is formed during the manufacturing process, so that the alignment mark is not masked by the light-shielding layer and can be reliably identified to fulfill its alignment role.

[0044] The alignment mark 7 may be formed using the same material as the pillar structure 42, or may be formed using a material different from that of the pillar structure 42. formed If the same material as the pillar structure 42 is used, it can be formed in a single process in which the pillar structure is formed, which is preferable as it simplifies the process.

[0045] <Solid-state imaging device according to the second embodiment> 4 is a schematic diagram showing the configuration of a solid-state imaging device 1A according to a second embodiment of the present invention. This embodiment differs from the first embodiment in that the height of the pillar structures is different from that of the first embodiment described above and that a second optical path layer 5 is provided on an alignment mark 7A. Since the other configurations are the same, a redundant description will be omitted. 4, the pillar structure 42 has a height equal to the total thickness of the first optical path layer 3, the light-shielding layer 4, and the second optical path layer 5. In other words, the pillar structure 42 is configured to be formed from the upper surface 2 a of the semiconductor substrate 2 to the upper surface 5 a of the second optical path layer 5. The alignment mark 7A has a height equal to the total height of the first optical path layer 3 and the light blocking layer 4. The configurations of the solid-state imaging devices 1 and 1A of the present invention have been described above using the first and second embodiments as examples. Next, the effects obtained based on the solid-state imaging devices 1 and 1A configured in this manner will be described.

[0046] <Effects> The solid-state imaging device 1 according to the first 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, the openings in the light-shielding layer are configured so that the opening dimension a in the direction perpendicular to the thickness direction of the light-shielding layer is 3 μm or more, i.e., the minimum dimension is 3 μm, and the aspect ratio α is 1 or more, thereby making the thickness of the light-shielding layer thicker than openings having predetermined opening dimensions. By making the thickness of the light-shielding layer thicker, it is possible to reliably block light, thereby suppressing light transmission through non-opening portions of the light-shielding layer and reducing light that becomes noise in the solid-state imaging device.

[0047] In the solid-state imaging device 1 according to the present invention, pillar structures that are the same shape as the openings 41 and that are light-transmittable are formed in the openings 41 of the light-shielding layer 4, and the pillar structures 42 function as the openings 41 that ensure an optical path for light from the microlenses 6 to the photoelectric conversion elements 21. The pillar structures 42 can be easily formed to be extremely small or elongated, so that the openings 41 can be easily formed even if the thickness of the light-shielding layer 4 is increased to make the openings 41 elongated. In the solid-state imaging device 1 according to the present invention, the pillar structures 42 are formed in the openings 41, and the dimensions of the openings 41 are defined by the pillar structures 42, so that the openings 41 can be formed without depending on the resolution of the pigment resist of the light-shielding layer 4.

[0048] In the solid-state imaging device 1 according to the present invention, the pillar structure is formed of a negative photosensitive resist, which has the advantages of strong adhesion, high sensitivity, and no strict requirements for development conditions. In the solid-state imaging device 1 according to the present invention, the provision of the alignment marks 7 allows accurate alignment when forming each layer. In particular, by aligning the photomask used when forming the openings, the accuracy of forming the openings can be improved, and only effective light useful for imaging can pass through the openings, thereby reducing light that becomes noise.

[0049] In the solid-state imaging element 1 of the present invention, the alignment mark 7 is formed using the same material as the pillar structure 42, so that the alignment mark 7 can be formed in the process of forming the pillar structure 42, thereby simplifying the process. In the solid-state imaging device 1 according to the present invention, if the opening dimensions of the opening 41 are set to be constant throughout the thickness direction, the opening 41 can be easily formed. In the solid-state imaging device 1 according to the present invention, if the opening dimensions of the openings 41a are set to increase with increasing distance from the semiconductor substrate in the thickness direction, it is possible to suppress the incidence of scattered light on the light incident side. In the solid-state imaging device 1 according to the present invention, when the opening 41a is formed in a frustum shape, the incident light is amplified and the utilization of the light is improved. efficiency can be increased. In the solid-state imaging device 1 according to the present invention, when the opening 41c is formed in a structure in which an inverted frustum shape and a cylindrical shape are stacked in this order from the semiconductor substrate 2 side, if the opening is formed in a cylindrical shape on the light incident side, it is possible to suppress the incidence of scattered light, and if the opening is formed in a frustum shape on the semiconductor layer side, it is possible to amplify the incident light and improve the utilization of light. efficiency can be increased.

[0050] In addition to the above-mentioned effects, the solid-state imaging device 1A according to the second embodiment can also achieve the following effects. After forming multiple pillar structures 42A, when the first optical path layer 3, the light-shielding layer 4, and the second optical path layer 5 are sequentially stacked on the substrate on which the pillar structures 42A are formed by spray coating, printing, etc., the pillar structures can be used as a positioning reference.

[0051] <Method of manufacturing a solid-state imaging device> FIG. 5 is a flowchart showing a method for manufacturing the solid-state imaging device 1 according to the first embodiment of the present invention, and FIG. 6 is a schematic diagram showing the process for manufacturing the solid-state imaging device 1 according to the first embodiment of the present invention. A method for manufacturing the solid-state imaging device 1 according to the first embodiment will be described below with reference to FIGS.

[0052] In the manufacturing method of the solid-state imaging element 1 according to the first embodiment, 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 conventional techniques will be described.

[0053] 5, the method for manufacturing a solid-state imaging device according to the first embodiment mainly includes a pillar structure forming step of forming light-transmitting pillar structures using a negative photosensitive resist, such as linear phenolic resin or polymethyl methacrylate, so that the aspect ratio α, which is the ratio of height to width, is 1 or more and the opening dimension a is 3 μm or more, and a light-shielding layer forming step S2 of forming a light-shielding layer so that the pillar structures are contained as fillers. Furthermore, an alignment mark forming step S3 is performed simultaneously with the pillar structure forming step S1, and the alignment mark is formed using the same material and method as the pillar structure.

[0054] Next, the pillar structure forming step S1 will be specifically described. FIG. 6 is a schematic diagram showing the pillar structure forming step S1 and the light-shielding layer forming step S2. The pillar structure forming step S1 mainly includes a step S11 (FIG. 6A) of forming a negative photosensitive resist layer, and a step S12 (FIG. 6B) of removing predetermined portions of the photosensitive resist layer to leave only the pillar structure.

[0055] 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 negative photosensitive resist is used. Resist is used. The pillar structure formation process S1 includes, for example, in step S11, a coating process of coating a substrate 45 with a negative photosensitive resist, a drying process of rotating the substrate 45 to dry the coated photosensitive resist and form a photosensitive resist film 46, and a pre-bake process of pre-baking the photosensitive resist film 46.In step S12, the pillar structure formation process includes an exposure process of exposing the pre-baked photosensitive resist film 46 with a mask having a predetermined pattern, a development process of developing the photosensitive resist film 46 with a developer to leave only predetermined areas as pillar structures (here, since the coated photosensitive resist is negative, the areas irradiated with light through the mask remain as pillar structures), a cleaning process of cleaning the substrate 45 on which the pillar structures remain, a drying process of rotating the substrate 45 to dry it, and a hard bake process of post-baking to hard-bake the pillar structures. In the manufacturing method of the solid-state imaging element 1 of the present invention, the photosensitive resist film 46 is exposed using a mask, and cylindrical photosensitive resist film 46a is left as a pillar structure, and cylindrical photosensitive resist film 46b is left as an alignment mark 7.

[0056] In the exposure step in step S12, light is also irradiated to predetermined positions on the periphery of the photosensitive resist film through a mask, and after the above-mentioned development step, the irradiated photosensitive resist film 46b remains as an alignment mark, thereby forming an alignment mark (photosensitive resist film 46b) outside the pillar structure 42 using the same material as the pillar structure 42 in a step similar to the pillar structure formation step S1 (alignment mark formation step S3). Here, the formation position of the alignment mark is set according to the specifications of the solid-state imaging element to be formed, and is set to be located on the periphery of the effective pixel area of ​​the solid-state imaging element.

[0057] In the pillar structure forming step S1, the photosensitive resist is exposed using a grayscale mask. In this way, the pillar structure is formed into an inverted frustum shape whose width increases in the height direction of the light-shielding layer 4 as it moves away from the semiconductor substrate 2. This allows the formation of a pillar structure 42 whose cross section is frustum-shaped, as shown in FIG. 2B.

[0058] The pillar structure forming step S1 may be configured to include a first pillar structure forming step of forming a first layer and a second pillar structure forming step of forming a second layer overlying the first layer after the first layer has been cured. The pillar structure thus formed has a laminated structure including at least a first layer and a second layer. In this case, for example, a pillar structure having the cross-sectional shape shown in FIG. 2C can be formed in which the first layer has the structure shown in FIG. 2B formed using a grayscale mask, the second layer has the structure shown in FIG. 2A, and the first layer has the cross-sectional shape shown in FIG. 2C. Alternatively, a pillar structure having the cross-sectional shape shown in FIG. 2D can be formed in which the first layer has the inverted frustum shape shown in FIG. 2B (i.e., a frustum shape in which the opening dimensions (opening area) decrease from the second surface 4b to the first surface 4a), and the second layer has the structure shown in FIG. 2B.

[0059] 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 S21 (FIG. 6C) of forming a light-shielding material film 47 so as to bury the pillar structures 42, and a light-shielding material film removing step S22 (FIG. 6D) of removing a predetermined thickness of the light-shielding material film 47 so as to expose the pillar structures 42 and the alignment marks 7 from the light-shielding material film 47. Specifically, the light-shielding layer forming process S2 includes a coating process of coating a light-shielding material so as to bury the pillar structures 42, a drying process of drying the coated light-shielding material to form a light-shielding material film 47, a pre-baking process of pre-baking the light-shielding material film 47, and a light-shielding material film removing process of removing a predetermined thickness of the light-shielding material film 47 so as to expose the pillar structures 42 and the alignment marks 7 from the light-shielding material film 47, thereby forming the light-shielding layer 4. In addition, the pillar structures are formed to the same height as the film thickness of the light-shielding layer, and the alignment marks 7 are formed so as not to be lower than the height of the upper surface 4a of the light-shielding layer 4.

[0060] 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 using a mask having a predetermined pattern, and a development step of developing the light-shielding material film 47 using a developer and 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. 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. After step S22, in order to form the solid-state imaging element 1, it is necessary to further arrange the first optical path layer 3, the second optical path layer 5, the microlens 6, etc., and at this time, alignment can be performed using the alignment mark 7.

[0061] The pillar structure forming step S1 and the light-shielding layer forming step S2 have been described above as examples of the manufacturing method for the solid-state imaging element 1. These steps are merely examples, and it is sufficient to form the pillar structures 42 so that the aspect ratio, which is the ratio of the height dimension to the width dimension, is 1 or more and the width dimension is 3 μm or more, and to form the alignment marks 7 on the periphery of the effective pixel region of the solid-state imaging element 1, and the specific steps are not limited to these.

[0062] Hereinafter, a method for manufacturing a solid-state imaging device according to the second embodiment will be described with reference to FIG. 7 and FIGS. 8A to 8C. FIG. 7 is a flowchart showing a method for manufacturing a solid-state imaging device according to the second embodiment of the present invention, and FIG. 8 is a schematic view showing a process for manufacturing a solid-state imaging device according to the second embodiment of the present invention.

[0063] The pillar structure forming step S1A and the alignment mark forming step S3A in the method for manufacturing a solid-state imaging device according to the second embodiment are the same as the pillar structure forming step S1 and the alignment mark forming step S3 in the first embodiment, respectively, and therefore redundant explanations will be omitted. Furthermore, the pillar structures are formed higher than in the first embodiment. As shown in FIG. 7, in the lamination step S2A, the first optical path layer 3, the light-shielding layer 4, and the second optical path layer 5 are laminated so as to include at least a part of the pillar structure as a filler. of Layers are stacked in order to form (Process S21A) At this time, the light-shielding layer 4 is formed so that the height of the alignment mark 7A is not lower than the upper surface 4a of the light-shielding layer 4, i.e., so that the alignment mark is exposed and identifiable from the light-shielding layer. Thereafter, a predetermined thickness of the second optical path layer is removed, and a pillar structure is formed to a thickness equal to the total thickness of the first optical path layer, the light-shielding layer, and the second optical path layer (S22A).

[0064] As shown in Figures 8A to 8C, in step S21A, pillar structures 51a (42A) and alignment marks 51b (7A) are formed. Then, in Figure 8C, a mask is positioned based on the alignment marks 7, and a first optical path layer 3 and a light-shielding layer 4 are applied in this order through the mask to the substrate 50 on which the pillar structures have been formed. At this time, the light-shielding layer 4 is preferably applied to a thickness that allows the alignment marks 7 to be exposed. Next, using the alignment marks 7 and pillar structures 42A as alignment references, a second optical path layer 5 is further applied, and finally, a stacked structure of three layers, the first optical path layer 3, the light-shielding layer 4, and the second optical path layer 5, is formed.

[0065] Next, in step S22A, although not shown, a predetermined thickness of the second optical path layer 5 is removed, and pillar structures 42A are formed to a thickness equal to the total thickness of the first optical path layer 3, the light-shielding layer 4, and the second optical path layer 5. Here, the pillar structures 42A are formed so as to be exposed from the upper surface 5a of the second optical path layer 5. Alternatively, the pillar structures 42A and the second optical path layer 5 are formed of different materials that are visually distinguishable from each other.

[0066] After step S22A, it is necessary to further arrange a microlens 6 on the second optical path layer 5 and to perform electrode openings by etching in order to form the solid-state imaging device 1. At this time, in addition to being able to perform alignment using the alignment mark 7, the pillar structure 42A can also be used as a reference for aligning the microlens 6 with the light-shielding layer 4, and the pillar structure 42A can also be used as a reference for aligning when performing electrode openings. Furthermore, in the manufacturing methods of the solid-state imaging elements 1, 1A according to the first and second embodiments described above, it has been explained that the alignment marks are formed in the same process as the pillar structure formation process using the same material as the pillar structure, but the alignment marks may be formed in a different process using a different material than the pillar structure.

[0067] In the method for manufacturing a solid-state imaging device according to the second embodiment described above, the pillar structure can fulfill the role of alignment, so that the formation of alignment marks can be omitted.

[0068] The manufacturing methods of the solid-state imaging devices 1 and 1A according to the first and second embodiments described above can also provide the following effects in addition to the effects of the solid-state imaging devices 1 and 1A described above. The alignment marks 7, 7A are formed from the same material as the pillar structures 42, 42A in the same process as the pillar structure formation process, thereby simplifying the process. By forming the pillar structure 42A so that it is exposed from the upper surface 5a of the second optical path layer 5, or by forming the pillar structure 42A and the second optical path layer 5 so that they are made of different materials that are visually distinguishable, the pillar structure 42A can serve as an alignment, and in this case, the formation of the alignment mark 7 can be omitted.

[0069] Although specific embodiments of the solid-state imaging device and the manufacturing method thereof according to the present invention have been described above, these embodiments are presented by way of example only and are not intended to limit the scope of the invention. The novel embodiments may be embodied in various other forms, and various omissions, substitutions, and modifications of components may be made without departing from the spirit of the invention. These embodiments and modifications 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 set forth in the claims. [Explanation of symbols]

[0070] 1,1A...Solid-state image sensor 2...Semiconductor substrate 3...First optical path layer 4...Light blocking layer 5...Second optical path layer 6...Microlens 7,7A...Alignment marks 11...effective pixel area 21...Photoelectric conversion element 41...Opening 42, 42A... Pillar structure

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 for securing an optical path of light incident on the photoelectric conversion element, the opening being formed at a position corresponding to the photoelectric conversion element; In a cross section along the thickness direction of the light-shielding layer 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 is a, and an aspect ratio, which is a ratio b / a of the height dimension to the opening dimension, is α, α≧1 and a≧3 μm; a pillar structure that can transmit light is formed in the opening in the same shape as the opening, the photosensitive resist constituting the pillar structure is a negative resist, an effective pixel area in which a plurality of pixels for performing photosensitive imaging are arranged; an alignment mark is provided on the periphery of the effective pixel area; The height of the alignment mark is formed so as not to be lower than the upper surface of the light-shielding layer. Solid-state imaging element.

2. the pillar structure has a height equal to the total thickness of the first optical path layer, the second optical path layer, and the light-shielding layer; The solid-state imaging device according to claim 1 .

3. the pillar structure has the same height as the film thickness of the light-shielding layer; The solid-state imaging device according to claim 1 .

4. the alignment mark is formed of the same material as the pillar structure; The solid-state imaging device according to claim 1 .

5. a pillar structure forming step of forming the light-transmittable pillar structure using a negative photosensitive resist so that the pillar structure has an aspect ratio, which is a ratio of a height dimension to a width dimension, of 1 or more and the width dimension is 3 μm or more; a light-shielding layer forming step of forming the light-shielding layer so as to include the pillar structure as a filler after the pillar structure forming step; an alignment mark forming step of providing the alignment mark on the periphery of an effective pixel area, The alignment mark is formed so that its height is not lower than the upper surface of the light-shielding layer. The method for manufacturing the solid-state imaging device according to claim 1 .

6. 6. The method for manufacturing a solid-state imaging device according to claim 5, wherein after forming the light-shielding layer, a predetermined thickness of the light-shielding layer is removed so as to expose the pillar structure from the light-shielding layer, and the pillar structure is formed to the same height as a film thickness of the light-shielding layer.

7. 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 for securing an optical path of light incident on the photoelectric conversion element, the opening being formed at a position corresponding to the photoelectric conversion element; In a cross section along the thickness direction of the light-shielding layer 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 is a, and an aspect ratio, which is a ratio b / a of the height dimension to the opening dimension, is α, α≧1 and a≧3 μm; a pillar structure that can transmit light is formed in the opening in the same shape as the opening, the photosensitive resist constituting the pillar structure is a negative resist, a pillar structure forming step of forming the light-transmittable pillar structure using a negative photosensitive resist so that the pillar structure has an aspect ratio, which is a ratio of a height dimension to a width dimension, of 1 or more and the width dimension is 3 μm or more; a first optical path layer, a light-shielding layer, and a second optical path layer forming step of laminating the first optical path layer, the light-shielding layer, and the second optical path layer in this order so as to contain the pillar structure as a filler, after the pillar structure forming step; after forming the first optical path layer, the light-shielding layer, and the second optical path layer by sequentially stacking them, removing a predetermined thickness of the second optical path layer so as to expose the pillar structure from the second optical path layer, and forming the pillar structure to a height equal to the total thickness of the first optical path layer, the second optical path layer, and the light-shielding layer; A method for manufacturing a solid-state imaging device.

8. when the first optical path layer, the light-shielding layer, and the second optical path layer are sequentially stacked to form the first optical path layer, the light-shielding layer, and the second optical path layer, the pillar structure is used as a positioning reference for the first optical path layer, the light-shielding layer, and the second optical path layer. The method for manufacturing a solid-state imaging device according to claim 7 .

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