Solid-state imaging device and method for manufacturing the same

Abstract

To improve a quantum efficiency in a solid-state image pickup device while suppressing deterioration of an image quality.SOLUTION: A solid-state image pickup device 50 comprises a plurality of image pixels 30 arranged in a two-dimensional matrix shape over a substrate 1. Each of the image pixels 30 includes: a light reception part 2 that performs photoelectric conversion; a microlens 10 that collects light in the light reception part 2; and at least one light scattering structure 6 that is provided between the light reception part 2 and the microlens 10.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a solid-state imaging device and a method for manufacturing the same.

Background Art

[0002] In recent years, there has been a demand for image sensors that are highly sensitive to near-infrared light (around wavelengths of 700 to 1100 nm) because they are suitable for applications such as surveillance, ranging, authentication, in-vehicle use, and sensing. In particular, there is a great demand for image sensors that are highly sensitive around a wavelength of 940 nm. This is because the component around a wavelength of 940 nm is less in the wavelength spectrum of sunlight reaching the earth's surface, so it is less affected by sunlight in daytime imaging.

[0003] Conventionally, in a solid-state imaging device, a photodiode (PD) is formed for each pixel formed by being arranged in a two-dimensional matrix on a substrate. Also, a microlens is formed for each pixel for light collection. When using a Si substrate, the light collected by the microlens is incident on the substrate almost perpendicularly because the refractive index is as high as about 4. In each PD, signal charges are generated according to the amount of received light of the incident light.

[0004] Here, near-infrared light is difficult to be absorbed when a Si substrate is used in an image sensor. In particular, around a wavelength of 940 nm, the quantum efficiency in a general image sensor is about 20%. As a means to increase this quantum efficiency, it is common to increase the depth of the photodiode. However, a depth of 10 μm or more is required to sufficiently absorb light. Also, when the depth of the PD is increased, there is a drawback that color mixing with adjacent pixels increases.

[0005] In contrast to the above, Patent Document 1 discloses a technique of forming periodic irregularities (for example, inverted pyramid-shaped irregularities) on the surface of a Si substrate. By this, light is refracted on the substrate surface and the optical path length in the substrate is lengthened. According to this technique, the absorption of incident light increases in the Si substrate and the quantum efficiency is improved.

Prior Art Documents

[0006] [Patent Document 1] Japanese Patent Publication No. 2016-001633 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] In the structure described in Patent Document 1, the Si substrate surface is processed directly, which destabilizes the interface states. This increases dark current and white scratches (white spots), leading to a decrease in image quality, making it necessary to repair the interface states on the Si substrate surface. Furthermore, because the shape of the irregularities is inverted pyramidal, the incident angle characteristics become irregular, making shading, moiré patterns, etc., more likely to occur in the output image, resulting in a decrease in image quality.

[0008] This disclosure describes a solid-state imaging device and a method for manufacturing the same that can improve quantum efficiency while suppressing a decrease in image quality. [Means for solving the problem]

[0009] The solid-state imaging device of this disclosure comprises a plurality of pixels arranged in a two-dimensional matrix on a substrate. Each pixel has a light-receiving unit that performs photoelectric conversion, a microlens that focuses light onto the light-receiving unit, and at least one light-scattering structure provided between the light-receiving unit and the microlens.

[0010] The method for manufacturing a solid-state imaging device according to the present disclosure comprises the steps of forming a plurality of light-receiving units arranged in a two-dimensional matrix on a substrate, and forming a light-scattering structure on each of the light-receiving units. [Effects of the Invention]

[0011] According to this disclosure, it is possible to improve quantum efficiency in a solid-state imaging device while suppressing a decrease in image quality. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a schematic diagram showing a cross-section of a solid-state imaging device according to the first embodiment of the present disclosure. [Figure 2] Figure 2 shows a cross-section of a comparative solid-state imaging device. [Figure 3] Figure 3 shows the spectral characteristics of a typical image sensor. [Figure 4] Figure 4 shows the incident angle characteristics of the solid-state imaging device of this disclosure. [Figure 5] Figure 5 shows the incident angle characteristics of a conventional solid-state imaging device. [Figure 6] Figure 6 shows the wavelength dependence of the refractive index of a color filter. [Figure 7] Figure 7 is a schematic diagram showing a cross-section of a solid-state imaging device of a modified example of the first embodiment of the present disclosure. [Figure 8] Figure 8 is a schematic plan view of a solid-state imaging device according to an embodiment of the present disclosure. [Figure 9] Figure 9 is a schematic plan view of a solid-state imaging device according to an embodiment of the present disclosure. [Figure 10] Figure 10 is a schematic plan view of a solid-state imaging device according to an embodiment of the present disclosure. [Figure 11] Figure 11 is a schematic diagram showing a cross-section of a solid-state imaging device according to a second embodiment of the present disclosure. [Figure 12] Figure 12 shows the quantum efficiency of a solid-state imaging device according to an embodiment of the present disclosure. [Figure 13] Figure 13 is a diagram showing the quantum efficiency of a solid-state imaging device according to an embodiment of the present disclosure. [Figure 14] Figure 14 shows a diagram illustrating the method for manufacturing the solid-state imaging device according to the present disclosure. [Figure 15] Figure 15 shows the manufacturing method of the solid-state imaging device, following Figure 14. [Figure 16] Figure 16 shows the method for manufacturing a solid-state imaging device, following Figure 15. [Figure 17] Figure 17 shows the method for manufacturing a solid-state imaging device, following Figure 15. [Figure 18] FIG. 18 is a diagram showing another manufacturing method of the solid-state imaging device of the present disclosure. [Figure 19] FIG. 19 is a diagram showing a manufacturing method of the solid-state imaging device following FIG. 18. [Figure 20] FIG. 20 is a diagram showing a manufacturing method of the solid-state imaging device following FIG. 19. [Figure 21] FIG. 21 is a diagram showing another manufacturing method of yet another solid-state imaging device of the present disclosure. [Figure 22] FIG. 22 is a diagram showing a manufacturing method of the solid-state imaging device following FIG. 21. [Figure 23] FIG. 23 is a diagram showing a manufacturing method of the solid-state imaging device following FIG. 22.

Mode for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the technology of the present disclosure is not limited to the following embodiments and can be appropriately modified within the scope where effects are achieved.

[0014] <First Embodiment> FIG. 1 is a diagram schematically showing a cross section of an exemplary solid-state imaging device 50 according to the first embodiment. The solid-state imaging device 50 includes a plurality of pixels 30 arranged in a two-dimensional matrix on a substrate 1, which is, for example, a silicon substrate. In FIG. 1, cross sections of two pixels 30 are shown.

[0015] Each pixel 30 is provided near the surface of the substrate 1 and includes a light-receiving portion 2 that generates charges by photoelectric conversion in response to incident light 31. The light-receiving portion 2 is, for example, a photodiode. A DTI (Deep Trench Isolation) region 3 is formed in the substrate 1 so as to surround the light-receiving portion 2. The DTI region 3 serves as a region that separates the pixels 30 from each other.

[0016] An insulating film 4 is formed on the substrate 1. The insulating film 4 consists of an insulating film lower layer 4a and an insulating film upper layer 4b above it. The insulating film lower layer 4a is formed of HfO, SiO2, etc., and stabilizes the interface state on the surface of the substrate 1, suppressing the occurrence of dark current and white scratches (white spots). The insulating film upper layer 4b is formed of a SiN film, etc., which has a high refractive index and is transparent up to the ultraviolet wavelength range, and is responsible for the anti-reflective effect. A protective film 5 made of SiO2, etc. is formed on the insulating film 4.

[0017] A light-shielding layer 7 is formed above the DTI region 3, surrounding the light-receiving section 2. The light-shielding layer 7 creates a recess above the light-receiving section 2. The protective film 5 also covers the sides and top of the light-shielding layer 7.

[0018] A color filter 8 is formed to fill the aforementioned recess located above the light-receiving section 2. The color filter 8 has a predetermined color for each pixel 30, and its upper surface may have irregularities overall. In contrast, a planarization film 9 is provided to cover the color filter 8. A microlens 10 is formed on the flat upper surface of the planarization film 9. The solid-state imaging device 50 can acquire images from both near-infrared light and visible light, and the color filter 8 is used for images taken with visible light.

[0019] Furthermore, a light scattering structure 6 is provided between the light-receiving section 2 and the microlens 10. More specifically, the light scattering structure 6 is provided within the color filter 8. In this example, the light scattering structure 6 is located close to the light-receiving section 2 in the height direction (direction perpendicular to the surface of the substrate 1), and is located near the center of the light-receiving section 2 when viewed from a direction perpendicular to the surface of the substrate 1 (i.e., in a plan view). The refractive index of the light scattering structure 6 is set lower than that of its surroundings (the color filter 8 in this example).

[0020] As shown in the left pixel 30 of Figure 1, the incident light 31 for the solid-state imaging device 50 is focused by the microlens 10. The incident light 31 passes through the planarization film 9, color filter 8, etc., and enters the light scattering structure 6. In the light scattering structure 6, reflection, diffraction, and scattering occur due to the difference in refractive index, and the light enters the light receiving unit 2 at various angles. As a result, the effective optical path length of the incident light traveling through the light receiving unit 2 becomes longer, the amount of near-infrared absorption increases, and the quantum efficiency improves.

[0021] This effect is greatly enhanced by the inclusion of the light-shielding layer 7 and the DTI region 3. Firstly, the DTI region 3 has a structure in which an insulating film is filled into grooves formed in the substrate 1 by etching or the like, resulting in a difference in refractive index between the DTI region 3 and the substrate 1. Due to this difference in refractive index, the incident light, which is obliquely scattered by the light-scattering structure 6, is reflected back to the light-receiving section 2. As a result, the optical path length within the light-receiving section 2 is further increased, improving quantum efficiency. This is illustrated by the arrows in Figure 1 illustrating the scattering and reflection of the incident light 31.

[0022] Figure 2 shows a comparative example solid-state imaging device 51. This is the same as the solid-state imaging device 50 of this embodiment (Figure 1), except that it does not have the light scattering structure 6. Because it does not have the light scattering structure 6, the incident light focused by the microlens 10 enters the light-receiving unit 2 at an angle nearly perpendicular to the surface of the substrate 1 and continues to travel in that direction. As a result, the optical path length within the light-receiving unit 2 is shorter than that of the solid-state imaging device 50, resulting in lower quantum efficiency. In contrast, the solid-state imaging device 50 of this embodiment has improved quantum efficiency by including the light scattering structure 6 as described above.

[0023] Figure 3 shows the spectral characteristics of a typical solid-state imaging device (which may be the comparative example solid-state imaging device 51). The R, G, and B lines represent the spectral characteristics of pixels corresponding to red, green, and blue light, respectively. As shown in Figure 3, in the near-infrared region, which has wavelengths longer than red light, the absorption coefficient of the silicon substrate decreases as the wavelength increases, and the quantum efficiency decreases. At a wavelength of around 940 nm, the quantum efficiency is about 20%. Therefore, increasing the optical path length is effective in improving the quantum efficiency.

[0024] Furthermore, in order to increase the reflection of light by the light scattering structure 6, it is preferable to increase the difference in refractive index between the light scattering structure 6 and its surroundings (color filter 8). Specifically, from the viewpoint of making the reflection, diffraction, and scattering of light in the light scattering structure 6 more pronounced, it is preferable to make the difference in refractive index 0.3 or more, and more preferably 0.5 or more.

[0025] The refractive index of the color filter 8 depends on the wavelength of light, but is generally around 1.6 to 2.0. Therefore, if the refractive index of the light scattering structure 6 is set to 1.3 or less, the effect of scattering the incident light 31 is more reliably achieved.

[0026] A simple way to achieve the refractive index difference described above is to select appropriate materials. In other words, the refractive index of the material constituting the light scattering structure 6 should be lower than that of the surrounding material.

[0027] For example, the color filter 8 may be formed from an organic acrylic film, while the light scattering structure 6 may be formed from a low refractive index organic film containing a silicon filler.

[0028] Furthermore, the light scattering structure 6 may be formed as a void (air gap, hollow structure) within the color filter 8 or the like. In this case, since the refractive index of air is approximately 1, the refractive index difference between the light scattering structure 6 and its surroundings becomes larger, resulting in a more pronounced effect.

[0029] Furthermore, the effect of improving quantum efficiency is enhanced when the light scattering structure 6 is located near the focal point of the microlens 10 and close to the surface of the substrate 1 (near the center of the light-receiving section 2). Figure 1 shows the light scattering structure 6 located in such a desirable position. The reason for this is as follows. Note that although the light scattering structure 6 is shown as an ellipse in Figure 1, its shape is not particularly limited.

[0030] Suppose the light scattering structure 6 is located near the planarization film 9 on the color filter 8. In this case, the incident light 31 is scattered at a position far from the light-receiving section 2, which may reduce the amount of light incident on the light-receiving section 2. Also, since the light scattering structure 6 is outside the focal point of the microlens 10, it can only scatter a portion of the incident light 31. Therefore, it is preferable to place the light scattering structure 6 in a position close to the light-receiving section 2 (substrate 1). In particular, it is preferable to place it in the position closest to the light-receiving section 2 on the color filter 8.

[0031] Furthermore, if the light scattering structure 6 is located at the periphery of the light-receiving section 2 (pixel 30) (near the light-shielding layer 7), it will also miss the light-collecting point of the microlens 10. As a result, the light-scattering effect will decrease. Therefore, it is preferable that the light scattering structure 6 be located near the center of the light-receiving section 2.

[0032] Figure 4 shows the incident angle characteristics of the solid-state imaging device 50. Specifically, when light is incident perpendicularly to the solid-state imaging device 50, it is represented as 0, when it is tilted to one side from perpendicular, it is represented as positive (+), and when it is tilted to the opposite side, it is represented as negative (-). When the incident angle of light of the same intensity differs, the efficiency is highest when the incident angle is 0, so the charge generated in the light-receiving unit 2 is maximum. As the incident angle increases, the charge decreases, but in the case of the solid-state imaging device 50, the change in the magnitude of the charge with respect to the incident angle is smooth. This is because the scattering of light by the light scattering structure 6 does not have any specificity with respect to the incident angle.

[0033] In contrast, Figure 5 shows the incident angle characteristics that may occur in the solid-state imaging device of Patent Document 1. In this case, since a periodic inverted pyramidal shape is formed on the surface of the Si substrate, specific refraction occurs with respect to the incident angle. As a result, as shown in Figure 5, the magnitude of the charge becomes irregular with respect to the incident angle, making it easy for shading, moiré patterns, etc., to occur in the output image, causing a decrease in image quality. This can be avoided in the structure of the present disclosure.

[0034] (Examples of color filters) Next, a modified example of the color filter of the first embodiment will be described.

[0035] The above describes an example of a solid-state imaging device that captures color images, in which a color filter 8 is provided on the pixel 30. However, it is possible to obtain similar effects in a solid-state imaging device that captures monochrome images. In this case, a transparent film is formed instead of the color filter 8 in Figure 1. By incorporating a light scattering structure 6 in the transparent film, the quantum efficiency can be improved in the same way as described above.

[0036] Furthermore, the color filter 8 may be a blue filter containing a blue pigment. As shown in Figure 6, the refractive index of the color filter depends on the wavelength of light. The R, G, and B curves show the refractive index for visible light and near-infrared light for color filters containing red, green, and blue pigments. As shown in Figure 6, the refractive index of the blue filter is high with respect to near-infrared light. Therefore, by making the color filter 8 around the light scattering structure 6 a blue filter, the difference in refractive index between these filters becomes large. As a result, the effect of improving quantum efficiency becomes significant. This configuration is useful when acquiring images using only near-infrared light.

[0037] (Variable example relating to light scattering structure 6) Next, a modified example of the light scattering structure 6 of the first embodiment will be described.

[0038] Figure 7 shows the modified solid-state imaging device 52. Compared to the solid-state imaging device 50 in Figure 1, the solid-state imaging device 52 identifies the shape of the light scattering structure. Since the other configurations are the same as the solid-state imaging device 50, the differences will be explained below.

[0039] Hereinafter, in the solid-state imaging device 52, the direction perpendicular to the surface of the substrate 1 will be referred to as the vertical direction, and the dimension in this direction will be referred to as the height. The direction horizontal to the surface of the substrate 1 will be referred to as the horizontal direction, and the dimension in this direction will be referred to as the width. In this case, the light scattering structure 12 of the solid-state imaging device 52 has a vertically elongated shape, that is, a shape in which the height is greater than the width.

[0040] In this way, even when light is incident on the pixel 30 at an oblique angle, the effect of the light scattering structure 12 in scattering light is easily maintained, as shown below.

[0041] Figure 1 shows the case where incident light is perpendicular to the pixel 30. In this case, the described effect is fully realized. However, in the solid-state imaging device 50 of Figure 1, if the incident light 31 is obliquely incident on the pixel 30 as shown in Figure 7, a misalignment occurs between the light-gathering point of the microlens 10 and the light-scattering structure 6, which may reduce the light-scattering effect.

[0042] In contrast, with the solid-state imaging device 52 shown in Figure 7, even if the incident light 31 is incident at an oblique angle, it easily enters the vertically elongated light scattering structure 12. Therefore, the reduction in the effect of the light scattering structure 12 in scattering light is suppressed. As a result, quantum efficiency is more reliably improved even when the incident light 31 is incident at an oblique angle. In the imaging region where the pixels 30 are arranged, the angle of the incident light 31 differs between the central and peripheral sides, so suppressing the effect of this difference is useful for improving image quality. Furthermore, the effect of differences in the lens (F-number, etc.) of the camera using the solid-state imaging device 52 can also be mitigated.

[0043] The light scattering structure 12 preferably has a height of 20% or more of the thickness of the color filter 8, and more preferably has a height of 50% or more. This makes it easier for light to enter the light diffusion structure 12 even when the incident light 31 is at an angle.

[0044] (Shape in a plan view of the light scattering structure) Next, the shape of the light scattering structure will be further explained. Figure 8 is a plan view of the solid-state imaging device 50, viewed from a direction perpendicular to the surface of the substrate 1. However, for the four pixels 30 arranged in 2 rows and 2 columns, only the light-shielding layer 7, the microlens 10, and the light scattering structure 6a are shown. The light scattering structure 6a may or may not have a vertically elongated shape, as shown in the light scattering structure 12 in Figure 7. Also, in Figure 8, the light scattering structure 6a is located near the center of the pixel 30 (light-receiving part 2). As mentioned above, this is a desirable position.

[0045] In the plan view, the light scattering structure 6a is preferably a shape with corners, particularly a shape that includes acute angles. For example, it may be a star shape including acute-angled protrusions, as shown in Figure 8. Such a shape allows for more effective scattering of incident light. As a result, the quantum efficiency is improved.

[0046] Furthermore, a shape with irregularities is preferred for the plan view of the light scattering structure, and a cross shape is also acceptable. Figures 9 and 10 show cross-shaped light scattering structures 6b and 6c. Although they have the same shape in the plan view, their orientations are different. With such configurations, the effect of scattering incident light 31, and as a result the effect of improving quantum efficiency, can be more reliably achieved.

[0047] <Second Embodiment> Figure 11 is a schematic cross-sectional view showing an exemplary solid-state imaging device 53 of a second embodiment. The solid-state imaging device 53 is similar to the solid-state imaging device 50 in Figure 1, except for the light scattering structure, and the differences will be mainly explained below.

[0048] In the solid-state imaging device 50 shown in Figure 1, one light scattering structure 6 is provided for each pixel 30. In contrast, in the solid-state imaging device 53 of this embodiment, multiple light scattering structures 11 are provided for each pixel 30.

[0049] The light scattering structure 11 is made of, for example, hollow silica. In other words, the color filter 8 contains hollow silica particles. When incident light 31 that has passed through the microlens 10 enters the color filter 8, it is refracted and reflected by a large number of silica particles (light scattering structure 11) and enters the light receiving unit 2 at various angles. Therefore, the optical path in the light receiving unit 2 becomes longer compared to the case without the light scattering structure 11 as shown in Figure 2. As a result, the amount of light absorbed in the light receiving unit 2 increases, and the quantum efficiency is improved.

[0050] The same principles apply as in the first embodiment, such as increasing the refractive index difference between the color filter 8 and the light scattering structure 11 (for example, to 0.3 or more), forming a transparent film instead of the color filter 8 for a monochrome imaging device, and using a blue filter instead of the color filter 8.

[0051] Alternatively, the light scattering structure 11 may consist of pigment aggregates. In this case, the refractive index difference with the color filter 8 tends to be smaller. However, because the pigment aggregates have a distorted and irregular shape, they have a high light scattering effect. Furthermore, the light scattering effect can be controlled by adjusting the size of the aggregates by setting a dispersant.

[0052] (Effect of light scattering structure) Optical simulations of the quantum efficiency were performed for the solid-state imaging device 53 of the second embodiment. Figure 12 shows the simulation results when hollow silica is used as the light scattering structure 11. Note that a transparent film is formed instead of the color filter 8. The horizontal axis is the radius of the hollow silica, and the vertical axis is the quantum efficiency at a wavelength of 940 nm. A radius of 0 corresponds to the case where the light scattering structure 11 is not provided.

[0053] As shown in Figure 12, the quantum efficiency tends to improve as the radius of the hollow silica as the light scattering structure 11 increases. The quantum efficiency is 22.9% when there is no light scattering structure 11, while the quantum efficiency is 23.6% when the radius of the light scattering structure 11 is 0.15 μm. This is an improvement of (23.6-22.9) / 22.9×100 ≈ 3.1%.

[0054] Furthermore, Figure 13 shows the simulation results when the light scattering structure 11 is formed inside the blue filter. The dashed line represents the simulation results shown in Figure 12, and the solid line represents the simulation results when the blue filter is used.

[0055] As shown in Figure 13, the quantum efficiency is further improved by using a blue filter. When the radius of the light scattering structure 11 is set to 0.15 μm and a blue filter is used, the quantum efficiency is 24.5%. This is an improvement of approximately 7.0% (24.5-22.9) / 22.9×100 ≈ 7.0% compared to the quantum efficiency of 22.9% when no blue filter is used and no light scattering structure 11 is present.

[0056] As described above, the light scattering structure formed in this disclosure can improve quantum efficiency without causing an increase in dark current and white spots. Furthermore, it does not produce refraction specific to the incident angle characteristics. As a result, a solid-state imaging device with excellent sensitivity and image quality is obtained.

[0057] <Manufacturing method for solid-state imaging devices> Next, a method for manufacturing the solid-state imaging device of this disclosure (in particular, a method for forming a light scattering structure) will be described.

[0058] (First manufacturing method) Figures 14 to 17 illustrate a first method for manufacturing the solid-state imaging device of this disclosure.

[0059] In Figure 14, a light-receiving portion 2, a DTI region 3, an insulating film 4, a protective film 5, and a light-shielding layer 7 are formed on the substrate 1. These can be formed, for example, by the following methods. The light-receiving portion 2 is formed by introducing impurities into the substrate 1 by ion implantation or the like. The DTI region 3 is formed by creating grooves in the substrate 1 by etching or the like and embedding an insulating film (such as a silicon oxide film) in these grooves. The insulating film 4 and the protective film 5 are formed as silicon oxide films, silicon nitride films, etc., by CVD (chemical vapor deposition) or the like. The light-shielding layer 7 is formed by forming a tungsten film to cover the substrate 1, then forming a resist pattern and removing the parts other than the necessary portion. Note that other methods may also be used for each of these.

[0060] When the light-shielding layer 7 (and the protective film 5 on the part above it) is formed so as to surround the pixel 30, a recess is formed on the light-receiving section 2 for each pixel 30.

[0061] Subsequently, a low refractive index material film 21 is formed to fill the recess. Figure 14 shows the state after the process up to this point has been completed.

[0062] Next, as shown in Figure 15, a resist pattern 22 is formed on the low refractive index material film 21. This is formed, for example, by forming a resist over the entire surface of the low refractive index material film 21 and then patterning it using lithography techniques.

[0063] Next, as shown in Figure 16, etching is performed using the resist pattern 22 as a mask to form a low refractive index material pattern 21a using the low refractive index material film 21.

[0064] Next, as shown in Figure 17, a high refractive index material film 23 with a higher refractive index than the low refractive index material film 21 is formed, and the low refractive index material pattern 21a is embedded. As a result, the low refractive index material pattern 21a becomes a light scattering structure, and a structure is formed in which the color filter 8 is formed as the high refractive index material film 23 around it. Subsequently, by forming the planarization film 9 and the microlens 10, the solid-state imaging device shown in Figure 1 or Figure 7 is manufactured.

[0065] Furthermore, the low refractive index material film 21 is, for example, a transparent film containing polysiloxane, and the high refractive index material film 23 is, for example, a transparent film containing nanoparticles such as titania nanoparticles.

[0066] According to this method, the position and shape of the light scattering structure 6 or 11 in the plan view can be determined by setting the position and shape of the resist pattern 22. This makes it possible to set the light scattering structure in the center of the light receiving section 2 and to set the shape of the light scattering structure as exemplified in Figures 8 to 10. Furthermore, by setting the thickness of the low refractive index material film 21, etc., a vertically elongated shape of the light scattering structure 11 can be realized.

[0067] (Second manufacturing method) Figures 18-19 illustrate a second method for manufacturing the solid-state imaging device of this disclosure.

[0068] In Figure 18, the substrate 1 has a light-receiving area 2, a DTI region 3, an insulating film 4, a protective film 5, and a light-shielding layer 7 formed on it. These can be formed in the same manner as in the first manufacturing method.

[0069] With a recess formed on the light-receiving portion 2 by the light-shielding layer 7, a material film 24 is formed by CVD. During this process, the film grows isotropically on the upper and side surfaces of the light-shielding layer 7. As a result, as shown in Figure 18, a void (air gap) 25 can be left near the center of the light-receiving portion 2 in the plan view. In other words, the film is formed in such a way that the recess is not completely filled.

[0070] Subsequently, as shown in Figure 19, another material film 26 is formed on the material film 24 until the entire film reaches a sufficient thickness.

[0071] Next, as shown in Figure 20, the entire surface is etched back to a predetermined thickness to flatten the upper surfaces of the material films 24 and 26. This creates voids 25 within the material films 24 and 36. After this, the solid-state imaging device of this disclosure is manufactured by forming the planarized film 9 and the microlens 10.

[0072] According to this manufacturing method, the material films 24 and 26 function as color filters 8, and the voids 25 function as light scattering structures in a solid-state imaging device.

[0073] (Third manufacturing method) Figures 21 to 23 illustrate a third method for manufacturing the solid-state imaging device of the present disclosure, which is a method for manufacturing the exemplary solid-state imaging device 53 of the second embodiment.

[0074] In Figure 21, the substrate 1 has a light-receiving area 2, a DTI region 3, an insulating film 4, a protective film 5, and a light-shielding layer 7 formed on it. These can be formed in the same manner as in the first manufacturing method.

[0075] A color resist 27 containing hollow silica or pigment aggregates as a light scattering structure 11 is applied to fill the recesses formed on the light-receiving section 2 by the light-shielding layer 7. The color resist 27 is exposed to light and developed to form a pattern of the color resist 27 containing the light scattering structure 11 in the desired locations.

[0076] Figure 22 shows that a pattern of color resist 27 is formed on some of the pixels 30.

[0077] Subsequently, the same coating, exposure, and development processes are performed to form patterns of color resists 28 corresponding to other colors for the other pixels 30. The color resists 28 also contain the light scattering structure 11. This state is shown in Figure 23.

[0078] Although only two pixels 30 are shown in the figure, if the solid-state imaging device has, for example, three RGB color filters, the same process would be performed one more time. After that, the planarization film 9 and microlenses 10 are formed to manufacture the solid-state imaging device 53 shown in Figure 11.

[0079] This manufacturing method is similar to conventional methods, except that a light-scattering structure 11 (such as hollow silica or pigment aggregates) is mixed into the color resist. In other words, no special process is required to provide the light-scattering structure 11.

[0080] In the case of a monochrome imaging device, a transparent film containing the light scattering structure 11 can be formed instead of the color resist. [Industrial applicability]

[0081] This disclosure can improve quantum efficiency while suppressing a decrease in image quality, making it useful as a solid-state imaging device. [Explanation of Symbols]

[0082] 1 circuit board 2 Light receiving section 3 DTI area 4. Insulating film 5 Protective film 6 Light scattering structure 6a~6c Light scattering structure (shape in plan view) 7 Light blocking layer 8 Color Filters 9 Planarization film 10 Microlenses 11, 12 Light scattering structure 21 Low refractive index material film 21a Low refractive index material pattern 22 Resist Patterns 23 High refractive index material films 24 Material film 25 Void 26 Material film 27, 28 Color Resist 30 pixels 31 Incident light 50, 52, 53 Solid-state imaging devices

Claims

1. The substrate has multiple pixels arranged in a two-dimensional matrix, Each of the aforementioned pixels has a light-receiving section that performs photoelectric conversion, a microlens that focuses light onto the light-receiving section, and at least one light-scattering structure provided between the light-receiving section and the microlens. The solid-state imaging device is characterized in that the light scattering structure has a star shape with multiple acute angles when viewed from a direction perpendicular to the substrate surface.

2. In claim 1, A solid-state imaging device characterized in that the refractive index of the light scattering structure is lower than the refractive index of the surrounding area of ​​the light scattering structure.

3. In claim 1, A solid-state imaging device characterized in that the refractive index of the material constituting the light scattering structure is 0.3 or more lower than the refractive index of the material surrounding the light scattering structure.

4. The substrate has multiple pixels arranged in a two-dimensional matrix, Each of the aforementioned pixels has a light-receiving section that performs photoelectric conversion, a microlens that focuses light onto the light-receiving section, and at least one light-scattering structure provided between the light-receiving section and the microlens. A transparent film or color filter is provided between the light-receiving section and the microlens. The solid-state imaging device is characterized in that the light scattering structure consists of multiple hollow silica particles contained in the transparent film or color filter.

5. The substrate has multiple pixels arranged in a two-dimensional matrix, Each of the aforementioned pixels has a light-receiving section that performs photoelectric conversion, a microlens that focuses light onto the light-receiving section, and at least one light-scattering structure provided between the light-receiving section and the microlens. The aforementioned light scattering structure is characterized by being composed of pigment aggregates, and is a solid-state imaging device.

6. In claim 1, The solid-state imaging device is characterized in that one of the light scattering structures is provided for each pixel.

7. In claim 1, The solid-state imaging device is characterized in that the light scattering structure is provided near the light receiving section.

8. In claim 1, The solid-state imaging device is characterized in that the light scattering structure is provided near the center of the light-receiving portion when viewed from a direction perpendicular to the substrate surface.

9. In claim 1, The solid-state imaging device is characterized in that the light scattering structure has a shape in which the dimension in the direction perpendicular to the substrate surface is larger than the dimension in the direction horizontal to the substrate surface.

10. In claim 5, The solid-state imaging device is characterized in that the light scattering structure is cross-shaped when viewed from a direction perpendicular to the substrate surface.

11. A process of forming multiple light-receiving units arranged in a two-dimensional matrix on a substrate, The process includes the step of forming a light scattering structure on each of the aforementioned light-receiving parts, The step of forming the aforementioned light scattering structure is: The process of forming a recess on the light-receiving portion by forming a light-shielding layer on the substrate surrounding each of the light-receiving portions, A method for manufacturing a solid-state imaging device, comprising the step of filling the recesses on the light-receiving portion while leaving voids, by forming a material film on the side surface and top surface of the light-shielding layer using an isotropic chemical vapor deposition method.

12. A process of forming multiple light-receiving units arranged in a two-dimensional matrix on a substrate, The process includes the step of forming a light scattering structure on each of the aforementioned light-receiving parts, The step of forming the aforementioned light scattering structure is: A step of forming a resist film containing hollow silica or pigment aggregates on the substrate, A method for manufacturing a solid-state imaging device, characterized by including a step of patterning the resist film.

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