Image pickup element and method for manufacturing the same

Abstract

The present invention reduces reflection of incident light in an imaging element, wherein a transparent resin is arranged on the surface of a microlens. The imaging element according to the present invention is provided with pixels, microlenses, a transparent resin layer and sealing glass. The pixels are formed on a semiconductor substrate and generate image signals corresponding to the light irradiated on the pixels. The microlens is arranged adjacent to the pixel and focuses the incident light on the pixel while flattening the surface of the pixel. The transparent resin layer is arranged adjacent to the microlens and is constructed to have a refractive index that differs by a predetermined value from the refractive index of the microlens. The sealing glass is arranged adjacent to the transparent resin and seals the semiconductor substrate.

Description

Technical Field

[0001] The present invention relates to an image pickup element and a method for manufacturing the image pickup element. Specifically, the present invention relates to an image pickup element including a microlens and a method for manufacturing the image pickup element. Background Art

[0002] Generally, people have used an imaging element as follows: it has a semiconductor chip for performing imaging and is housed in a hollow package with a glass window. In order to improve reliability, the hollow package is formed using ceramics or the like. Pixels for converting irradiated light into electrical signals are arranged in the imaging element in a two-dimensional lattice. A microlens is arranged in each of a plurality of pixels, and the microlens collects incident light. In the above-mentioned hollow package, the air in the package and the microlens are in contact with each other. Since the refractive index of air is relatively small, the refractive index difference between the air and the microlens can be increased, and the incident light can be refracted to a large extent on the surface of the microlens. Therefore, the efficiency of the microlens in collecting incident light can be improved.

[0003] In contrast, an imaging element with a simplified structure has been proposed, in which a sealing glass is bonded to the light-receiving surface of a semiconductor chip via a transparent resin. In the case of this imaging element, the microlens is in contact with the transparent resin. Since the transparent resin has a higher refractive index than air, by adopting silicon nitride (SiN) having a larger refractive index as the microlens material, the refractive index difference on the surface of the microlens can be ensured, and the reduction in light collection efficiency can be reduced. For example, the following solid-state imaging element has been proposed: it has a light-transmitting insulating layer, a first planarization layer, a color filter, a second planarization layer, a stress relief layer, a microlens containing SiN, and a transparent resin stacked in sequence on a semiconductor substrate including a photoelectric conversion unit (for example, see patent document 1). In this solid-state imaging element, the second planarization layer is formed using an organic material, and therefore the stress relief layer is arranged between the second planarization layer and the microlens formed using an inorganic material. The stress relief layer has an intermediate film stress between the second planarization film and the microlens, and relieves the stress difference between the second planarization film and the microlens.

[0004] Reference List

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2014-168098 Summary of the invention

[0007] Problems to be solved by the present invention

[0008] In the above conventional technology, since a plurality of layers having different refractive indexes are arranged between the microlens and the color filter, there is a problem that incident light is reflected at the interface between these layers. Since the reflected incident light is reflected again at the interface between the sealing glass and the air (external air) and enters the pixel, there is a problem that image quality is deteriorated.

[0009] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to reduce reflection of incident light in an image pickup element having a transparent resin arranged on a surface of a microlens.

[0010] Technical solutions to the problem

[0011] The present invention aims to solve the above-mentioned problems, and a first aspect of the present invention is an imaging element, which includes: a pixel, which is formed on a semiconductor substrate and is configured to generate an image signal based on irradiated light; a microlens, which is arranged adjacent to the pixel and is configured to collect incident light, irradiate the pixel with the incident light, and flatten the surface of the pixel; a transparent resin layer, which is arranged adjacent to the microlens, and at least a portion of the transparent resin layer has a refractive index that is different from the refractive index of the microlens by a predetermined difference; and a sealing glass, which is arranged adjacent to the transparent resin layer and seals the semiconductor substrate.

[0012] Furthermore, in the first aspect, the transparent resin layer may have the refractive index such that the predetermined difference is 0.4 to 0.6.

[0013] In addition, in the first aspect, the transparent resin layer may include a first transparent resin layer and a second transparent resin layer, wherein the first transparent resin layer is arranged adjacent to the microlens and has a refractive index that differs from the refractive index of the microlens by a predetermined difference, and the second transparent resin layer has a refractive index different from that of the first transparent resin layer.

[0014] Furthermore, in the first aspect, the transparent resin layer may include an anti-reflection layer between the first transparent resin layer and the second transparent resin layer.

[0015] Furthermore, in the first aspect, the microlens may be formed using an organic material.

[0016] Furthermore, in the first aspect, the microlens may include a lens portion formed using an inorganic material and a planarization portion having substantially the same refractive index as the lens portion and arranged adjacent to the pixel.

[0017] Furthermore, in the first aspect, the microlens may include an anti-reflection film.

[0018] Furthermore, in the first aspect, the microlens includes a region as a concavoconvex surface of the microlens, the region serving as the antireflection film.

[0019] Furthermore, in the first aspect, an imaging lens disposed adjacent to a surface of the sealing glass different from a surface of the sealing glass on which the transparent resin layer is disposed may be further included.

[0020] In addition, a second aspect of the present technology is a method for manufacturing an imaging element, the method comprising: a pixel forming step of forming pixels on a semiconductor substrate, the pixels being configured to generate image signals based on irradiated light; a microlens arranging step of arranging a microlens adjacent to the formed pixels, the microlens collecting incident light to illuminate the pixels using the incident light, and flattening the surface of the pixels; a transparent resin layer arranging step of arranging a transparent resin layer adjacent to the arranged microlens, the refractive index of the transparent resin layer differing by a predetermined difference from the refractive index of the microlens; and a sealing step of arranging sealing glass adjacent to the arranged transparent resin layer, the sealing glass sealing the semiconductor substrate.

[0021] This aspect brings about the following effect: while using a microlens having a refractive index different by a predetermined difference from that of the transparent resin layer, the surface of the pixel is flattened by the microlens. A film for flattening the surface of the pixel can be omitted, and in an image pickup element having a transparent resin layer and a sealing glass arranged adjacent to the microlens arranged in the pixel, it is assumed that reflection of incident light at the pixel surface is reduced.

[0022] Effects of the Invention

[0023] According to the present invention, an excellent effect of reducing reflection of incident light in an image pickup element having a transparent resin arranged on the surface of a microlens is exhibited. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a diagram illustrating a configuration example of an image pickup element according to an embodiment of the present invention.

[0025] Figure 2 is a diagram illustrating a configuration example of a pixel according to an embodiment of the present invention.

[0026] Figure 3 is a cross-sectional view illustrating a configuration example of an image pickup element according to an embodiment of the present invention.

[0027] Figure 4 is a cross-sectional diagram illustrating a configuration example of a pixel according to the first embodiment of the present invention.

[0028] Figure 51 is a diagram illustrating an example of a method of manufacturing an image pickup element according to the first embodiment of the present invention.

[0029] Figure 6 1 is a diagram illustrating an example of a method of manufacturing an image pickup element according to the first embodiment of the present invention.

[0030] Figure 7 1 is a diagram illustrating an example of a method of manufacturing an image pickup element according to the first embodiment of the present invention.

[0031] Figure 8 is a cross-sectional diagram illustrating a configuration example of a pixel according to a second embodiment of the present invention.

[0032] Fig. 9 is a cross-sectional diagram illustrating a configuration example of a pixel according to a third embodiment of the present invention.

[0033] Fig.10 is a cross-sectional diagram illustrating a configuration example of a pixel according to a fourth embodiment of the present invention.

[0034] Fig.11 is a diagram illustrating a configuration example of an antireflection film according to a fourth embodiment of the present invention.

[0035] Fig.12 is a cross-sectional diagram illustrating a configuration example of a pixel according to a fifth embodiment of the present invention.

[0036] Fig.13 is a block diagram illustrating a schematic configuration example of a camera as an example of an image pickup device to which the present technology is applied. DETAILED DESCRIPTION

[0037] Next, an embodiment (hereinafter referred to as an embodiment) for implementing the present invention will be described with reference to the accompanying drawings. In the following drawings, the same or similar parts are represented by the same or similar reference numerals. It should be noted that the drawings are schematic, and the dimensional ratios of the various parts, etc. do not always correspond to the actual dimensional ratios. In addition, it goes without saying that the dimensional relationships and ratios are different between the drawings. In addition, the embodiments will be described in the following order.

[0038] 1. First Embodiment

[0039] 2. Second Embodiment

[0040] 3. Third embodiment

[0041] 4. Fourth embodiment

[0042] 5. Fifth embodiment

[0043] 6. Camera application examples

[0044] <1. First Embodiment>

[0045] [Structure of the imaging element]

[0046] Figure 1 is a diagram illustrating a configuration example of an image pickup element according to an embodiment of the present invention. Figure 1 The image pickup element 1 in the embodiment includes a pixel array unit 10 , a vertical driving unit 201 , a column signal processing unit 202 , and a control unit 203 .

[0047] The pixel array unit 10 has pixels 100 arranged in a two-dimensional grid. Here, the pixel 100 generates an image signal corresponding to the irradiated light. The pixel 100 includes a photoelectric conversion unit that generates a charge according to the irradiated light. In addition, the pixel 100 also includes a pixel circuit. The pixel circuit generates an image signal based on the charge generated by the photoelectric conversion unit. The generation of the image signal is controlled by a control signal generated by the vertical drive unit 201 described below. In the pixel array unit 10, signal lines 109 and 108 are arranged in an XY matrix. The signal line 109 is a signal line for transmitting a control signal of the pixel circuit in the pixel 100, arranged for each row of the pixel array unit 10, and connected in common to the pixel 100 arranged in each row. The signal line 108 is a signal line for transmitting an image signal generated by the pixel circuit of the pixel 100, arranged for each column of the pixel array unit 10, and connected in common to the pixel 100 arranged in each column. The photoelectric conversion unit and the pixel circuit are formed on a semiconductor substrate.

[0048] The vertical drive unit 201 generates a control signal for the pixel circuit of the pixel 100. The vertical drive unit 201 generates a control signal for the pixel circuit of the pixel 100. Figure 1 The signal line 109 in the column transmits the generated control signal to the pixel 100. The column signal processing unit 202 processes the image signal generated by the pixel 100. The column signal processing unit 202 processes the image signal generated by the pixel 100. Figure 1 The column signal processing unit 202 receives an image signal transmitted from the pixel 100 via the signal line 108 in the vertical drive unit 201. The processing in the column signal processing unit 202 corresponds to, for example, analog-to-digital conversion for converting an analog image signal generated in the pixel 100 into a digital image signal. The image signal processed by the column signal processing unit 202 is output as an image signal of the image pickup element 1. The control unit 203 controls the entire image pickup element 1. The control unit 203 controls the image pickup element 1 by generating and outputting a control signal for controlling the vertical drive unit 201 and the column signal processing unit 202. The control signal generated by the control unit 203 is transmitted to each of the vertical drive unit 201 and the column signal processing unit 202 via the signal lines 209 and 208.

[0049] The vertical driving unit 201, the column signal processing unit 202, and the control unit 203 described above are formed on a semiconductor chip different from the pixel array unit 10. Specifically, the vertical driving unit 201, the column signal processing unit 202, and the control unit 203 are formed on the signal processing chip 20. As described below, the signal processing chip 20 is bonded and stacked on the semiconductor chip constituting the pixel array unit 10 to form a semiconductor package.

[0050] [Pixel Circuit Structure]

[0051] Figure 2 is a diagram illustrating a configuration example of a pixel according to an embodiment of the present invention. Figure 2 is a circuit diagram illustrating a configuration example of the pixel 100 . Figure 2 The pixel 100 in FIG. 1 includes a photoelectric conversion unit 101 , a charge holding unit 102 , and MOS transistors 103 to 106 .

[0052] The anode of the photoelectric conversion unit 101 is grounded, and the cathode of the photoelectric conversion unit 101 is connected to the source of the MOS transistor 103. The drain of the MOS transistor 103 is connected to the source of the MOS transistor 104, the gate of the MOS transistor 105, and one end of the charge holding unit 102. The other end of the charge holding unit 102 is grounded. The drains of the MOS transistors 104 and 105 are commonly connected to the power supply line Vdd, and the source of the MOS transistor 105 is connected to the drain of the MOS transistor 106. The source of the MOS transistor 106 is connected to the signal line 108. The gates of the MOS transistors 103, 104, and 106 are respectively connected to the transmission signal line TR, the reset signal line RST, and the selection signal line SEL. It should be noted that the transmission signal line TR, the reset signal line RST, and the selection signal line SEL constitute the signal line 109.

[0053] As described above, the photoelectric conversion unit 101 generates charges according to irradiated light. A photodiode can be used for the photoelectric conversion unit 101. In addition, the charge holding unit 102 and the MOS transistors 103 to 106 constitute a pixel circuit.

[0054] The MOS transistor 103 is a transistor that transfers the charge generated by the photoelectric conversion of the photoelectric conversion unit 101 to the charge holding unit 102. The charge transfer in the MOS transistor 103 is controlled by a signal transmitted through the transmission signal line TR. The charge holding unit 102 is a capacitor that holds the charge transferred by the MOS transistor 103. The MOS transistor 105 is a transistor that generates a signal based on the charge held in the charge holding unit 102. The MOS transistor 106 is a transistor that outputs the signal generated by the MOS transistor 105 to the signal line 108 as an image signal. The MOS transistor 106 is controlled by a signal transmitted by the selection signal line SEL.

[0055] The MOS transistor 104 is a transistor that resets the charge holding unit 102 by discharging the charge held in the charge holding unit 102 to the power supply line Vdd. The reset by the MOS transistor 104 is controlled by a signal transmitted through the reset signal line RST, and is performed before the charge transfer by the MOS transistor 103. It is to be noted that at the time of this reset, the photoelectric conversion unit 101 can be further reset by making the MOS transistor 103 conductive. In this way, the pixel circuit converts the charge generated by the photoelectric conversion unit 101 into an image signal.

[0056] [Cross-sectional structure of imaging element]

[0057] Figure 3 is a cross-sectional view illustrating a configuration example of an image pickup element according to an embodiment of the present invention. Figure 3 2 is a cross-sectional view illustrating the configuration of the image pickup element 1 . Figure 3 The imaging element 1 in the embodiment includes a pixel array unit 10 , a signal processing chip 20 and an imaging lens 181 .

[0058] Figure 3 The pixel array unit 10 in the embodiment includes a semiconductor substrate 12 , a wiring region 13 , a transparent resin layer 161 , and a sealing glass 171 .

[0059] The semiconductor substrate 12 is a semiconductor substrate in which a semiconductor region portion among elements of the pixels 100 arranged in the pixel array unit 10 is formed. The semiconductor substrate 12 can be formed using silicon.

[0060] The wiring area 13 is an area where wiring for connecting elements of the pixel 100 and wiring constituting the signal line 109 and the like are formed. An inter-chip connection pad 134 is arranged in the wiring area 13. The inter-chip connection pad 134 is an electrode that is connected to an inter-chip connection pad 234 arranged in the signal processing chip 20 described below and exchanges signals, etc. The inter-chip connection pad 134 can be formed using a metal (e.g., copper (Cu)).

[0061] A microlens 151 is formed on the rear surface of the semiconductor substrate 12, which is a surface different from the front surface on which the wiring area 13 is arranged. The microlens 151 is a lens that collects incident light and irradiates the incident light onto the pixels 100 arranged in the pixel array unit 10. An imaging element of a type that captures an image of the incident light irradiated on the rear surface of the semiconductor substrate 12 is called a back-illuminated imaging element.

[0062] The sealing glass 171 is a glass that seals the image pickup element 1 and protects the image pickup element 1. As the sealing glass 171, for example, glass having a refractive index of 1.5 can be used.

[0063] The transparent resin layer 161 is a transparent resin arranged between the semiconductor substrate 12 and the sealing glass 171. The transparent resin layer 161 is a resin that is arranged adjacent to the microlens 151 on the rear surface of the semiconductor substrate 12 and bonds the sealing glass 171 to the semiconductor substrate 12. In addition, the refractive index of the transparent resin layer 161 is different from the refractive index of the microlens 151 by a predetermined difference. In addition, by setting the refractive index of the transparent resin layer 161 to 1.5, which is the same as that of the sealing glass 171, the reflection of the incident light at the interface between the sealing glass 171 and the transparent resin layer 161 can be reduced. The details of the configuration of the transparent resin layer 161 and the microlens 151 will be described below.

[0064] The signal processing chip 20 includes a semiconductor substrate 22 , a wiring region 23 , through-electrodes 243 , rear surface side pads 242 , a resin layer 241 , and solder balls 244 .

[0065] The semiconductor substrate 22 is a semiconductor substrate formed using silicon or the like, and a semiconductor region portion among elements constituting the vertical driving unit 201 , the column signal processing unit 202 , and the control unit 203 included in the signal processing chip 20 is formed in the semiconductor substrate 22 .

[0066] The wiring area 23 is an area where wiring and the like for connecting elements included in the signal processing chip 20 are formed. Inter-chip connection pads 234 connected to the inter-chip connection pads 134 of the pixel array unit 10 are arranged in the wiring area 23. In addition, front surface side pads 235 are arranged in the wiring area 23. The front surface side pads 235 are electrodes connected to the rear surface side pads 242 via the through electrodes 243 described below.

[0067] The rear surface side pad 242 is arranged on the rear surface of the semiconductor substrate 22. The rear surface side pad 242 is an electrode for connecting to an external circuit such as an image processing device connected to the imaging element 1. The through electrode 243 is arranged between the front surface side pad 235 and the rear surface side pad 242, and electrically connects the front surface side pad 235 and the rear surface side pad 242. The rear surface side pad 242 and the through electrode 243 can be formed using a metal (e.g., Cu).

[0068] The solder ball 244 is a hemispherical solder arranged adjacent to the rear surface side pad 242. The solder ball 244 is a solder for mounting the imaging element 1 on a substrate of an external circuit. The resin layer 241 is a resin for protecting the signal processing chip 20 and the rear surface side pad 242. For the resin layer 241, for example, a solder resist can be used.

[0069] The wiring area 13 of the pixel array unit 10 and the wiring area 23 of the signal processing chip 20 are joined, so that the pixel array unit 10 and the signal processing chip 20 are stacked. At this time, the chip-to-chip connection pads 134 and 234 are adjacently joined. Specifically, the pixel array unit 10 and the signal processing chip 20 are brought into contact with each other by aligning the chip-to-chip connection pads 134 and 234 in a manner adjacent to each other, and the pixel array unit 10 and the signal processing chip 20 are heated and pressure-welded. As a result, the wiring areas 13 and 23 are connected, and the chip-to-chip connection pads 134 and 234 are mechanically and electrically connected. As a result, signal transmission between the pixel array unit 10 and the signal processing chip 20 becomes possible. This connection between semiconductor chips is called Cu-Cu connection. Figure 1 The signal lines 108 and 109 shown in FIG. 1 include the Cu-Cu connection.

[0070] The imaging lens 181 is what is called a wafer-level lens, and is an imaging lens formed integrally with the imaging element 1 .

[0071] Note that the configuration of the image pickup element 1 is not limited to this example. For example, instead of the solder balls 244, a configuration may be adopted in which pads for solder connection are arranged in an island shape with respect to the resin layer 241. Furthermore, the image pickup element 1 without the image pickup lens 181 may be adopted.

[0072] [Pixel structure]

[0073] Figure 4 is a cross-sectional diagram illustrating a configuration example of a pixel according to the first embodiment of the present invention. Figure 4 is a cross-sectional view illustrating a region of the pixel array unit 10 where the pixels 100 are formed.

[0074] Figure 4 The pixel 100 in FIG. 1 includes a semiconductor substrate 12 , a wiring region 13 , an insulating film 123 , a light shielding film 142 , a color filter 141 , and a microlens 151 .

[0075] In the semiconductor substrate 12, for example, a p-type well region 121 is formed, and a semiconductor region constituting an element of the pixel 100 is formed in the well region 121. For convenience, it is assumed that the well region 121 is formed Figure 4 The semiconductor substrate 12 in the Figure 4 In Figure 2 The photoelectric conversion unit 101 shown in FIG. 1 is illustrated as an example of an element constituting the pixel 100 . Figure 4 The semiconductor region 122 in is an n-type semiconductor region. The photoelectric conversion unit 101 is formed using the semiconductor region 122 and a well region surrounding the semiconductor region 122. A photodiode is formed by a pn junction at the interface between the n-type semiconductor region 122 and the p-type well region.

[0076] An insulating layer 131, a wiring layer 132, and a via plug 133 are arranged in the wiring region 13. The wiring layer 132 is a wiring for transmitting a signal. Elements constituting the pixel 100 are connected through the wiring layer 132. The wiring layer 132 can be formed using a metal such as Cu.

[0077] The insulating layer insulates the wiring layer 132. For example, the insulating layer 131 may be formed using an insulating material such as silicon oxide (SiO2) or the like. The wiring layer 132 and the insulating layer 131 may be formed in multiple layers. Figure 4 An example of forming the wiring layer 132 and the insulating layer 131 in three layers is illustrated. The via plug 133 connects the wiring layers 132 formed in different layers. The via plug 133 can be formed using, for example, Cu or tungsten (W).

[0078] The wiring layer 132 is connected to the inter-chip connection pads 134 arranged on the surface of the wiring area 13 via the via plugs 133. As described above, the wiring layer 132, the via plugs 133 and the inter-chip connection pads 134 constitute the signal lines 109 and the like in the pixel array unit 10.

[0079] The insulating film 123 is a film that insulates the semiconductor substrate 12. The insulating film 123 can be formed using, for example, SiO2.

[0080] The color filter 141 is a filter that transmits light having a predetermined wavelength among the light entering the pixel 100. As the color filter 141, a color filter that transmits any one of red light, green light, and blue light may be arranged. The color filter 141 may be formed using an organic material, such as a resin in which a pigment or dye is dispersed. At this time, the color filter 141 has different thicknesses and different refractive indices according to the wavelength of the transmitted light. The refractive index of the color filter 141 is, for example, 1.6 to 1.8.

[0081] The light shielding film 142 is disposed between the pixels 100 and shields incident light. The light shielding film 142 shields light obliquely incident from the adjacent pixel 100. With the light shielding film 142, the incidence of light transmitted through the color filter 141 corresponding to different colors of the adjacent pixel 100 can be prevented, and the occurrence of color mixing can be prevented.

[0082] The microlens 151 is a hemispherical lens that collects incident light on the photoelectric conversion unit 101 of the pixel 100. The microlens 151 is arranged for each pixel 100 and is arranged adjacent to the pixel 100. Figure 4 In FIG. 1 , the microlens 151 is arranged adjacent to the color filter 141 in the pixel 100. In addition, the microlens 151 flattens the surface of the pixel 100. Figure 4In the embodiment, the microlens 151 planarizes the surface of the color filter 141. As described above, the color filter 141 is formed to have different thicknesses according to corresponding colors. Figure 4 The microlens 151 in the color filter 141 is formed into a hemispherical shape while flattening the surface of the color filter 141. As a result, the height of the microlens 151 can be made uniform between adjacent pixels 100. In addition, Figure 4 The microlens 151 in FIG. 1 may be formed using an organic material and may be a lens having a refractive index of 2.0. Specifically, the microlens 151 may be formed using an acrylic resin in which titanium oxide (TiO 2 ) is dispersed as a filler.

[0083] The transparent resin layer 161 is arranged adjacent to the microlens 151 and has a refractive index different from that of the microlens 151. Thus, incident light can be refracted at the interface between the transparent resin layer 161 and the microlens 151. The transparent resin layer 161 can be formed using, for example, acrylic resin or epoxy resin. For example, the refractive index can be set to 1.5 using these resins.

[0084] The greater the refractive index difference between the transparent resin layer 161 and the microlens 151, the greater the incident light transmitted through the microlens 151 can be refracted, and the focal length can be further shortened. For example, 0.4 to 0.6 can be used as the refractive index difference, and the pixel 100 can be formed according to the focal length based on the refractive index difference. In the above example of the microlens 151 and the transparent resin layer 161, the refractive index difference is 0.5. By adopting the simplified package as described above, the incident light can be collected in the imaging element 1 having a construction in which an air layer is not arranged on the surface of the microlens 151. A transparent resin layer 161 with a larger refractive index can be arranged instead of air with a refractive index of 1.0.

[0085] In addition, the microlens 151 formed using an organic material is formed while flattening the surface of the color filter 141. Therefore, a flattening film between the color filter 141 and the microlens 151 can be omitted. In addition, since the color filter 141 and the microlens 151 are formed using a resin, the thermal expansion coefficients of the color filter 141 and the microlens 151 are relatively close to each other. Therefore, the occurrence of stress due to the difference in thermal expansion coefficients is reduced, and the arrangement of a film for relieving stress can be omitted.

[0086] In the case where a flattening film or the like is disposed between the color filter 141 and the microlens 151, a phenomenon occurs in which incident light reflected by the flattening film or the like is reflected again at the surface of the sealing glass 171 in contact with the air and enters the pixel 100. This causes, for example, a ring-shaped light spot in which so-called concentric light is reflected around the imaging light source, resulting in deterioration of image quality. Figure 4Since the image pickup element 1 in the embodiment does not require a planarization film or the like, the film structure of the pixel 100 can be simplified and reflection of incident light can be reduced. Deterioration of image quality can be prevented.

[0087] [Method for manufacturing imaging element]

[0088] Figures 5 to 7 1 is a diagram illustrating an example of a method of manufacturing an image pickup element according to the first embodiment of the present invention. Figures 5 to 7 1 is a diagram illustrating an example of the manufacturing steps of the image pickup element 1. First, the well region 121 and the semiconductor region 122 are formed on the semiconductor wafer 301 constituting the semiconductor substrate 12. Next, the wiring region 13 is formed on the surface of the semiconductor substrate 12 ( Figure 5 a) in the figure.

[0089] Next, the semiconductor wafer 301 constituting the semiconductor substrate 12 is inverted and bonded to the semiconductor wafer 302 constituting the semiconductor substrate 22 formed with the wiring region 23. At this time, Cu-Cu connection is formed between the inter-chip connection pads 134 and 234. Next, the surface of the semiconductor wafer 301 constituting the semiconductor substrate 12 is ground to reduce the thickness ( Figure 5 b) in the above.

[0090] Next, the insulating film 123, the light shielding film 142, and the color filter 141 are sequentially stacked on the surface of the semiconductor substrate 12 ( Figure 5 c). Pixel 100 can be Figure 5 It is formed on the semiconductor substrate 12 through steps a to c in FIG.

[0091] Next, a resin layer 401 serving as a material of the microlens 151 is applied on the surface of the color filter 141, and a resist 402 is arranged on the surface of the resin layer 401. The resist 402 is formed into a hemispherical shape similar to the microlens 151. For example, the resist material is applied, exposed, and developed to form an island-shaped resist. Thereafter, the resist is heated to a temperature equal to or higher than the softening temperature of the resist using a reflow furnace or the like, and is formed into a hemispherical shape ( Figure 6 d) in.

[0092] Next, the resin layer 401 is etched using the resist 402 as a mask. Dry etching can be used for this etching. Thus, the shape of the resist 402 is transferred to the resin layer 401, and the microlens 151 can be formed. This method of manufacturing the microlens 151 is called an etch-back method ( Figure 6 e) Through this process, the microlens 151 can be arranged adjacent to the color filter 141 of the pixel 100.

[0093] Next, a transparent resin layer 161 is applied onto the surface of the microlens 151 ( Figure 7 f). Thus, the transparent resin layer 161 can be arranged adjacent to the microlens 151. Next, the sealing glass 171 is arranged on the surface of the applied transparent resin layer 161, and the transparent resin layer 161 is cured ( Figure 7 g). Thus, the sealing glass 171 can be arranged adjacent to the transparent resin layer 161, and the semiconductor substrate 12 can be sealed with the sealing glass 171.

[0094] Next, the through electrode 243 and the rear surface side pad 242 are formed in the semiconductor substrate 22, and the resin layer 241 is applied. The applied resin layer 241 is etched to form an opening adjacent to the rear surface side pad 242, and a solder ball 244 is formed in the opening. Next, the imaging lens 181 is placed on the surface of the sealing glass 171 and cut into individual pieces. The imaging element 1 can be manufactured through the above steps.

[0095] Note that the manufacturing method of the image pickup element 1 is not limited to this example. For example, when forming the microlens 151, the material resin of the microlens 151 may be applied to the surface of the color filter 141 by spin coating or the like to flatten the surface of the color filter 141. Thereafter, the material resin of the microlens 151 may be applied thickly to form the resin layer 401.

[0096] As described above, with the image pickup element 1 according to the first embodiment of the present invention, the microlens 151 is formed of an organic material and has a refractive index that differs by a predetermined difference from the refractive index of the transparent resin layer 161. As a result, reflection of incident light in the image pickup element having the transparent resin disposed on the surface of the microlens can be reduced.

[0097] <2. Second Embodiment>

[0098] The image pickup element 1 of the first embodiment described above uses the microlens 151 formed of an organic material. In contrast, the image pickup element 1 according to the second embodiment of the present invention is different from the first embodiment described above in that a microlens formed of an inorganic material is used.

[0099] [Pixel structure]

[0100] Figure 8 is a cross-sectional diagram illustrating a configuration example of a pixel according to a second embodiment of the present invention. Figure 8 The image sensor 1 in the reference Figure 4 The described image pickup element 1 is different in that a microlens 156 is included instead of the microlens 151 .

[0101] The microlens 156 includes a lens portion 152 and a flattened portion 153. The lens portion 152 is a lens formed using an inorganic material. As a material constituting the lens portion 152, for example, an oxide having a refractive index of 2.0 or more can be used. By using the lens portion 152, the refractive index difference with the transparent resin layer 161 can be set to 0.5 or more.

[0102] The planarizing portion 153 is disposed adjacent to the surface of the pixel 100 to planarize the surface of the pixel 100. Figure 8 , the planarization portion 153 planarizes the surface of the color filter 141. A transparent resin may be used for the planarization portion 153. In addition, by setting the refractive index of the planarization portion 153 to be substantially the same as the refractive index of the lens portion 152, reflection of incident light at the interface between the lens portion 152 and the planarization portion 153 may be reduced.

[0103] Furthermore, in the case where the film stress of the planarization portion 153 is set to a value between the respective film stresses of the lens portion 152 and the color filter 141 , the film stresses of the lens portion 152 and the color filter 141 can be relaxed.

[0104] Description of configurations of the image pickup element 1 other than the above-described configuration is omitted because these configurations are similar to those of the image pickup element 1 described in the first embodiment of the present invention.

[0105] As described above, the image pickup element 1 according to the second embodiment of the present invention has the planarizing portion 153 disposed between the lens portion 152 and the color filter 141 , thereby reducing reflection of incident light when the lens portion 152 formed of an inorganic material is used.

[0106] <3. Third embodiment>

[0107] The image pickup element 1 of the above-described embodiment uses a single transparent resin layer 161. In contrast, the image pickup element 1 according to the third embodiment of the present invention is different from the above-described first embodiment in that a transparent resin layer including a plurality of layers is used.

[0108] [Pixel structure]

[0109] Fig. 9 is a cross-sectional diagram illustrating a configuration example of a pixel according to a third embodiment of the present invention. Fig. 9 The image sensor 1 in the reference Figure 4 The described image pickup element 1 is different in that a microlens 154 is included instead of the microlens 151 , and a transparent resin layer 162 and an antireflection layer 163 are further included.

[0110] The microlens 154 is a lens having a refractive index value smaller than that of the microlens 151, and for example, the refractive index value of the microlens 154 is 1.9. For example, the microlens 154 may be formed using an organic material such as a resin, etc. Since a resin having a high refractive index is not used, the microlens can be formed relatively easily similar to the microlens 151.

[0111] The transparent resin layer 162 is a transparent resin layer arranged adjacent to the microlens 154 and having a refractive index different by a predetermined difference from the refractive index of the microlens 154. In addition, the transparent resin layer 161 is a transparent resin layer having a refractive index different from that of the transparent resin layer 162. The refractive index of the transparent resin layer 161 may be set to, for example, 1.5, which is the same as the refractive index of the sealing glass 171.

[0112] In the case of using a microlens 154 having a refractive index of 1.9 and adopting a value of 0.5 as the refractive index difference with the transparent resin layer, it is necessary to use a transparent resin layer having a refractive index of 1.4 or less. However, in the case of arranging a transparent resin layer having a refractive index of 1.4 or less, the refractive index is different from the refractive index of the sealing glass 171. Therefore, reflection of the incident light occurs at the interface between the transparent resin layer and the sealing glass 171. Therefore, a transparent resin layer 161 having the same refractive index as the sealing glass 171 is used as a transparent resin layer adjacent to the sealing glass 171, and a transparent resin layer 162 having a refractive index of 1.4 or less is further arranged. Thus, the above-mentioned predetermined difference as the refractive index difference between the transparent resin layer and the microlens 154 can be ensured while preventing reflection of the incident light between the transparent resin layer and the sealing glass 171. It should be noted that the transparent resin layer 162 is an example of the first transparent resin layer described in the claims. The transparent resin layer 161 is an example of the second transparent resin layer described in the claims.

[0113] The anti-reflection layer 163 is arranged between the transparent resin layers 161 and 162, and reduces the reflection of incident light at the interface between the anti-reflection layer 163 and each of the transparent resin layers 161 and 162. The anti-reflection layer 163 is formed to have a thickness of 1 / 4 of the wavelength of the incident light, so that the phase of the reflected light from the interface between the anti-reflection layer 163 and the transparent resin layer 162 is reversed relative to the reflected light from the interface between the anti-reflection layer 163 and the transparent resin layer 161. Thus, the reflected light from the interface between each of the transparent resin layers 161 and 162 and the anti-reflection layer 163 is offset, and the reflection is reduced. Such an anti-reflection layer 163 can be formed using, for example, SiO2, SiN, and SiON. By further including the anti-reflection layer 163, the reflection of the incident light at the interface between the anti-reflection layer 163 and each of the transparent resin layers 161 and 162 can be reduced. It should be noted that the anti-reflection layer 163 can be omitted.

[0114] Description of configurations of the image pickup element 1 other than the above-described configuration is omitted because these configurations are similar to those of the image pickup element 1 described in the first embodiment of the present invention.

[0115] As described above, the image pickup element 1 according to the third embodiment of the present invention has the transparent resin layers 161 and 162 having different refractive indices. Thus, a transparent resin layer having a refractive index different by a predetermined difference from that of the microlens 154 can be arranged while preventing reflection between the transparent resin layer and the sealing glass 171, and even in the case of using the microlens 154 having a relatively small refractive index, reflection of incident light can be reduced.

[0116] <4. Fourth embodiment>

[0117] The image pickup element 1 of the third embodiment described above uses the antireflection layer 163. In contrast, the image pickup element 1 according to the fourth embodiment of the present invention is different from the third embodiment described above in that a microlens including an antireflection film is used.

[0118] [Pixel structure]

[0119] Fig.10 is a cross-sectional diagram illustrating a configuration example of a pixel according to a fourth embodiment of the present invention. Fig.10 The image sensor 1 in the reference Fig. 9 The described image pickup element 1 is different in that an antireflection film 155 is further included on the surface of the microlens 154 .

[0120] The antireflection film 155 is a film formed on the surface of the microlens 154, and reduces reflection of incident light at the interface between the microlens 154 and the transparent resin layer 162. By arranging the antireflection film 155, reflection of incident light in the image pickup element 1 can be further reduced.

[0121] [Structure of anti-reflection film]

[0122] Fig.11 is a diagram illustrating a configuration example of an antireflection film according to a fourth embodiment of the present invention. Fig.11 The anti-reflection film 155 has concavo-convex portions formed on the surface of the microlens 154. Such concavo-convex portions scatter the reflected light and inhibit the light from being incident on the pixel 100 again. Such an anti-reflection film 155 can be formed by, for example, selectively etching the metal contained in the microlens 154. It should be noted that the size of the concavo-convex portions of the anti-reflection film 155 is advantageously less than 150 nm. This is because the effect of diffraction on the adjacent pixels 100 can be reduced. It should be noted that the construction of the anti-reflection film 155 is not limited to this example. For example, an anti-reflection film 155 having a construction similar to that of the anti-reflection layer 163 can be used.

[0123] Description of configurations of the image pickup element 1 other than the above-described configuration is omitted because these configurations are similar to those of the image pickup element 1 described in the third embodiment of the present invention.

[0124] As described above, the image pickup element 1 according to the fourth embodiment of the present invention uses the microlens 154 including the antireflection film 155 , thereby further suppressing reflection of incident light.

[0125] <5. Fifth embodiment>

[0126] The imaging device 1 of the second embodiment uses a lens portion 152 formed of an inorganic material having a refractive index of 2.0 or more. In contrast, the imaging device 1 according to the fifth embodiment of the present invention differs from the second embodiment in that a lens portion formed of an inorganic material having a relatively small refractive index is used.

[0127] [Pixel structure]

[0128] Fig.12 is a cross-sectional diagram illustrating a configuration example of a pixel according to a fifth embodiment of the present invention. Fig.12 The image sensor 1 in the reference Figure 8 The imaging element 1 described is different in that a microlens 159 is used instead of the microlens 156 and also includes a reference Fig. 9 The transparent resin layer 162 and the anti-reflection layer 163 are described.

[0129] Fig.12 The microlens 159 in FIG. 1 includes a lens portion 157 and a flattened portion 158. The lens portion 157 is formed using an inorganic material, and the refractive index is set to, for example, 1.9. Fig.12 The planarization portion 158 in the embodiment has substantially the same refractive index as the lens portion 157. Description of other configurations of the lens portion 157 and the planarization portion 158 is omitted because these configurations are similar to those of the reference Figure 8 The configurations of the lens portion 152 and the flattening portion 153 are described to be similar.

[0130] exist Fig.12 In the imaging element 1 of FIG. 1 , even in the case of using the lens portion 157 formed of an inorganic material having a refractive index of 1.9, the surface of the color filter 141 can be flattened by the flattening portion 158, and the refractive index difference between the lens portion 157 and the transparent resin layer 162 can be set to 0.5. That is, the same as the reference can be obtained. Figure 4 The described case of using the microlens 151 formed of an organic material having a refractive index of 2.0 has a similar effect. In addition, by arranging the anti-reflection layer 163, reflection of incident light at the interface between the anti-reflection layer 163 and each of the transparent resin layers 161 and 162 can be reduced.

[0131] Description of configurations of the image pickup element 1 other than the above-described configuration is omitted because these configurations are similar to those of the image pickup element 1 described in the second embodiment of the present invention.

[0132] As described above, in the image pickup element 1 according to the fifth embodiment of the present invention, the transparent resin layer 162 and the anti-reflection layer 163 are arranged. Thus, in the case of using the lens portion 157 formed of an inorganic material, while ensuring that the refractive index difference between the transparent resin layer 162 and the lens portion 157 is a value of 0.5, the reflection at the interface between the anti-reflection layer 163 and each of the transparent resin layers 161 and 162 can be reduced.

[0133] <6. Camera Application>

[0134] The present technology can be applied to various products. For example, the present technology can be implemented as an imaging element mounted on an imaging device such as a camera.

[0135] Fig.13 is a block diagram illustrating a schematic configuration example of a camera as an example of an image pickup device to which the present technology is applied. Fig.13 The camera 1000 in the embodiment includes a lens 1001, an imaging element 1002, an imaging control unit 1003, a lens driving unit 1004, an image processing unit 1005, an operation input unit 1006, a frame memory 1007, a display unit 1008, and a recording unit 1009.

[0136] The lens 1001 is an imaging lens of the camera 1000. The lens 1001 collects light from a subject and causes the collected light to enter an imaging element 1002 described below to form an image of the subject.

[0137] The imaging element 1002 is a semiconductor element that captures light from a subject collected by the lens 1001. The imaging element 1002 generates an analog image signal from the irradiated light, converts the analog image signal into a digital image signal, and outputs the digital image signal.

[0138] The imaging control unit 1003 controls imaging performed by the imaging element 1002. The imaging control unit 1003 controls the imaging element 1002 by generating a control signal and outputting the control signal to the imaging element 1002. In addition, the imaging control unit 1003 can perform autofocus in the camera 1000 based on the image signal output from the imaging element 1002. Here, autofocus is a system that detects the focal position of the lens 1001 and automatically adjusts the focal position. As autofocus, the following method can be used: by using phase difference pixels arranged in the imaging element 1002 to detect the image plane phase difference, and detecting the focal position, thereby detecting the image plane phase difference (image plane phase difference autofocus). In addition, a method of detecting the position where the contrast of the image is the highest as the focal position can also be applied (contrast autofocus). The imaging control unit 1003 adjusts the position of the lens 1001 via the lens driving unit 1004 based on the detected focal position, and performs autofocus. Note that the imaging control unit 1003 can be formed using, for example, a digital signal processor (DSP: Digital Signal Processor) equipped with firmware.

[0139] The lens driving unit 1004 drives the lens 1001 based on the control of the imaging control unit 1003. The lens driving unit 1004 can drive the lens 1001 by changing the position of the lens 1001 using a built-in motor.

[0140] The image processing unit 1005 processes the image signal generated by the image pickup element 1002. This processing corresponds to, for example, demosaicing for generating an image signal of a missing color in the image signal corresponding to red, green, and blue of each pixel, noise reduction for removing noise of the image signal, encoding of the image signal, etc. The image processing unit 1005 can be formed using, for example, a microcomputer equipped with firmware.

[0141] The operation input unit 1006 receives an operation input from a user of the camera 1000. As the operation input unit 1006, for example, a button or a touch panel can be used. The operation input received by the operation input unit 1006 is transmitted to the imaging control unit 1003 and the image processing unit 1005. Thereafter, a process corresponding to the operation input, for example, a process such as imaging a subject, is started.

[0142] The frame memory 1007 is a memory for storing frames, where a frame is an image signal of one screen. The frame memory 1007 is controlled by the image processing unit 1005 and stores frames during image processing.

[0143] The display unit 1008 displays the image processed by the image processing unit 1005. For the display unit 1008, for example, a liquid crystal panel can be used.

[0144] The recording unit 1009 records the image processed by the image processing unit 1005. For the recording unit 1009, for example, a memory card or a hard disk can be used.

[0145] The camera to which the present invention is applicable has been described. The present technology can be applied to the imaging element 1002 in the above-mentioned configuration. Specifically, the camera 1002 can be applied to the imaging element 1002 in the above-mentioned configuration. Figure 1 The described imaging element 1 is applied to the imaging element 1002. By applying the imaging element 1 to the imaging element 1002, reflection of incident light can be reduced in an imaging element adopting a package having a simple configuration. Deterioration in image quality of an image generated by the camera 1000 can be prevented.

[0146] It should be noted that although a camera is described as an example here, the technology according to the present invention can be applied to, for example, a surveillance device or the like.

[0147] Finally, the description of the above embodiments is an example of the present invention, and the present invention is not limited to the above embodiments. Therefore, it goes without saying that various modifications other than the above embodiments can be made according to the design, etc., as long as these modifications do not deviate from the technical idea according to the present invention.

[0148] It should be noted that the present invention may also have the following configurations.

[0149] (1) An imaging device comprising:

[0150] pixels formed on a semiconductor substrate and configured to generate image signals according to irradiated light;

[0151] a microlens disposed adjacent to the pixel and configured to collect incident light, illuminate the pixel with the incident light, and flatten a surface of the pixel;

[0152] a transparent resin layer disposed adjacent to the microlens, and at least a portion of the transparent resin layer has a refractive index different by a predetermined difference from a refractive index of the microlens; and

[0153] A sealing glass is arranged adjacent to the transparent resin layer and seals the semiconductor substrate.

[0154] (2) The image pickup element according to (1), wherein the transparent resin layer has the refractive index such that the predetermined difference is 0.4 to 0.6.

[0155] (3) An imaging element according to (1) or (2), wherein the transparent resin layer includes a first transparent resin layer and a second transparent resin layer, the first transparent resin layer being arranged adjacent to the microlens and having a refractive index that differs from the refractive index of the microlens by the predetermined difference, and the second transparent resin layer having a refractive index different from that of the first transparent resin layer.

[0156] (4) The image pickup element according to (3), wherein the transparent resin layer includes an antireflection layer between the first transparent resin layer and the second transparent resin layer.

[0157] (5) The image sensor according to any one of (1) to (4), wherein the microlens is formed using an organic material.

[0158] (6) The imaging element according to any one of (1) to (4), wherein the microlens includes a lens portion and a flattening portion, the lens portion being formed using an inorganic material, the flattening portion having substantially the same refractive index as the lens portion and being arranged adjacent to the pixel.

[0159] (7) The image pickup element according to any one of (1) to (6), wherein the microlens includes an antireflection film.

[0160] (8) The image pickup element according to (7), wherein the microlens includes a region as a concavoconvex surface of the microlens, the region serving as the antireflection film.

[0161] (9) The imaging device according to any one of (1) to (8), further comprising:

[0162] An imaging lens is arranged adjacent to a surface of the sealing glass that is different from a surface of the sealing glass on which the transparent resin layer is arranged.

[0163] (10) A method for manufacturing an imaging element, the method comprising:

[0164] a pixel forming step of forming pixels on a semiconductor substrate, the pixels being configured to generate image signals based on irradiated light;

[0165] a microlens arranging step of arranging a microlens adjacent to the formed pixel, the microlens collecting incident light to illuminate the pixel with the incident light and flattening the surface of the pixel;

[0166] a transparent resin layer arranging step of arranging a transparent resin layer adjacent to the arranged microlenses, the refractive index of the transparent resin layer being different from the refractive index of the microlenses by a predetermined difference; and

[0167] A sealing step of arranging a sealing glass adjacent to the arranged transparent resin layer, the sealing glass sealing the semiconductor substrate.

[0168] Reference numerals list

[0169] 1. Camera element

[0170] 10 pixel array unit

[0171] 12, 22 Semiconductor substrate

[0172] 13, 23 Wiring area

[0173] 20 Signal processing chip

[0174] 100 pixels

[0175] 123 Insulation film

[0176] 141 Color Filter

[0177] 142 shading film

[0178] 151, 154, 156, 159 Microlens

[0179] 152, 157 Lens unit

[0180] 153, 158 Flattening section

[0181] 155 Anti-reflective film

[0182] 161, 162 transparent resin layer

[0183] 163 Anti-reflection layer

[0184] 171 Sealed Glass

[0185] 181 Camera lens

[0186] 1002 Camera Components

Claims

1. An imaging element, comprising: pixels formed on a semiconductor substrate and configured to generate image signals according to irradiated light; a microlens disposed adjacent to the pixel and configured to collect incident light, illuminate the pixel with the incident light, and flatten a surface of the pixel; a first transparent resin layer disposed adjacent to the microlens, and at least a portion of the first transparent resin layer having a refractive index different by a predetermined difference from a refractive index of the microlens; a first anti-reflection film; a second anti-reflection film, the second anti-reflection film being disposed on a surface of the microlens, wherein the first transparent resin layer is located between the first anti-reflection film and the second anti-reflection film; as well as A sealing glass is arranged adjacent to the first transparent resin layer and seals the semiconductor substrate.

2. The imaging element according to claim 1, wherein: The first transparent resin layer has the refractive index such that the predetermined difference is 0.4 to 0.

6.

3. The imaging element according to claim 1, wherein: The image pickup element further includes a second transparent resin layer located between the sealing glass and the first anti-reflection film, the second transparent resin layer having a refractive index different from that of the first transparent resin layer.

4. The imaging element according to claim 3, wherein: The first anti-reflection film is located between the first transparent resin layer and the second transparent resin layer.

5. The imaging element according to claim 1, wherein: The microlens is formed using an organic material.

6. The imaging element according to claim 1, wherein: The microlens includes a lens portion formed using an inorganic material and a planarization portion having substantially the same refractive index as the lens portion and disposed adjacent to the pixel.

7. The imaging element according to claim 1, wherein: The microlens includes a region as a concavoconvex surface of the microlens, the region serving as the second anti-reflection film.

8. The imaging element according to claim 3 or 4, further comprising: An imaging lens is arranged adjacent to a surface of the sealing glass that is different from a surface of the sealing glass on which the second transparent resin layer is arranged.

9. A method for manufacturing an imaging element, the method comprising: a pixel forming step of forming pixels on a semiconductor substrate, the pixels being configured to generate image signals based on irradiated light; a microlens arranging step of arranging a microlens adjacent to the formed pixel, the microlens collecting incident light to illuminate the pixel with the incident light and flattening the surface of the pixel; a transparent resin layer arranging step of arranging a transparent resin layer adjacent to the arranged microlenses, the refractive index of the transparent resin layer being different from the refractive index of the microlenses by a predetermined difference; disposing a first anti-reflection film adjacent to the transparent resin layer; Disposing a second anti-reflection film on the surface of the microlens, wherein the transparent resin layer is located between the first anti-reflection film and the second anti-reflection film; as well as A sealing step of arranging a sealing glass adjacent to the arranged transparent resin layer, the sealing glass sealing the semiconductor substrate.

Images