JP2005203676A - Solid-state imaging device and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid-state imaging device which improves light condensing efficiency for the light of oblique incidence. <P>SOLUTION: The solid-state imaging device 200 comprises a light condensing part 6 for condensing incident light; a photonic crystal 7 which is formed on the light outgoing face of the light condensing part 6, receives the condensed light, and changes the traveling direction of the light of a predetermined wavelength region; and a light receiving part 2 which is formed on the light outgoing face of the photonic crystal 7, receives the guided wave in the photonic crystal 7, and converts the light into an electric charge. Since the photonic crystal 7 has a flat dispersion plane for the light of the predetermined wavelength region, the guided wave is shaped in parallel flux. The photonic crystal 7 guides the guided wave to the direction normal to the light receiving plane of the light receiving part 2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a solid-state imaging device mounted on a CCD, a MOS image sensor or the like.

  The CCD, invented by Boyle and Smith at Bell Labs in 1970, was installed in home video cameras around 1985, and in most cameras in the 1990s. In particular, since the mid-1990s, digital still cameras have emerged, and coupled with the spread of personal computers, the market for solid-state image sensors (CCD, MOS image sensors) has expanded significantly. In the 2000s, cameras began to be built in mobile phones, and the market for solid-state image sensors has grown dramatically.

  The demand for solid-state imaging devices has changed to higher sensitivity / higher pixels, but in recent years, with the reduction in thickness of digital still cameras / cell phones, etc., it has been demanded that the camera portion be made thinner. In other words, the lens used for the camera part has a short focal point, and the light incident on the solid-state image sensor has a wide angle (a large angle measured from the vertical axis of the incident surface of the solid-state image sensor). means.

  FIG. 16 shows a cross-sectional structure of a unit pixel of a conventional solid-state image sensor. In the solid-state imaging device 230, a light receiving unit 102 formed of a p / n junction that converts incident light into electric charges is formed on a silicon substrate 101 (in addition, an element that transfers a signal of the light receiving element (charge coupled device). Etc.) and multi-layer wiring, but they are omitted for simplicity in this figure). An acrylic flat layer 111 is present on the light receiving unit 102. The role of the flat layer 111 is to flatten the uneven surface due to the charge coupled device or the multilayer wiring. An aluminum light-shielding layer 103 is formed so that incident light does not irradiate silicon outside the light receiving unit 102 to form unnecessary electron-hole pairs (unnecessary electron-hole pairs generate smears and deteriorate image quality) To make it happen). The size of the opening of the light shielding layer 103 is substantially equal to the size of the light receiving unit 102. An acrylic layer 104 exists on the light shielding layer 103. The role of the acrylic layer 104 will be described later. On top of this, there is a color filter layer 105. A pigment or dye is generally used for the color filter layer 105, and the color (wavelength) of transmitted light is determined by absorbing light. On the color filter layer 105, a micro lens 106 is present. When there is no microlens 106, light is incident on the light shielding layer 103 and is wasted. Light is collected by the microlens 106 at the opening of the light-shielding portion 103 and is incident on the light-receiving portion 102, so that unnecessary light is eliminated and sensitivity is improved. The role of the acrylic layer 104 is necessary as an optical path for collecting this light.

  FIG. 17 shows a manufacturing flow of a conventional solid-state imaging device with a microlens. First, a substrate 101 is prepared as shown in FIG. 17A, and then a light receiving portion 102 is formed in the substrate 101 as shown in FIG. In addition, charge coupled devices and wirings are also formed, but are not shown here. Next, as shown in FIG. 17C, an acrylic layer 111 is formed thereon, and the surface is flattened by CMP to form a flat layer. Further, as shown in FIG. 17D, a light shielding layer 103 is formed thereon by photolithography. Further, as shown in FIG. 17E, an acrylic layer 104 is formed thereon. Further, as shown in FIG. 17 (f), a color filter layer 105 is formed thereon, and finally, as shown in FIG. 17 (g), a microlens 106 is formed thereon.

Various techniques have been disclosed as solid-state imaging devices using photonic crystals (see, for example, Patent Document 1). In the technique disclosed in Patent Document 1, a window is formed on the light receiving section, and a photonic crystal having a taper shape that does not allow invasion of light in a predetermined wavelength region is provided in a region surrounding the window. That is, the photonic crystal is used as a reflection mirror that does not transmit light.
JP 2003-133536 A

However, the conventional solid-state imaging device has the following problems.
FIG. 18 is a diagram illustrating a state when light is incident on a conventional solid-state imaging device. 18A shows a case where light enters the solid-state image sensor 230 vertically, and FIG. 18B shows a case where light enters with an inclination. Light is collected at the light receiving unit 102 by the condensing action of the microlens 106 with respect to the normal incident light 107. However, when the incident angle of the oblique incident light 108 (an angle measured from the vertical axis of the incident surface of the solid-state imaging device) is very large, the light condensing position deviates from the light receiving unit 102, and no light enters the light receiving unit 102 at all. Not. When the focal length of the micro lens 106 is f and the side of the light receiving unit 102 is D, oblique light having an incident angle greater than θ = arctan (D / 2f) is not collected. For this reason, for an optical system with a short focal length (an optical system having a large incident angle θ) for a thin camera, the conventional microlens cannot capture light sufficiently, and the sensitivity decreases. For this reason, there is a problem that a photographed screen becomes dark or an image is blurred when the exposure time is long.

  Therefore, an object of the present invention is to provide a solid-state imaging device that realizes an improvement in sensitivity to obliquely incident light and a method for manufacturing the same.

  In order to achieve the above object, a solid-state imaging device according to the present invention is formed on a condensing part that condenses incident light, and an exit surface side of the condensing part, and enters the condensed light, A photonic crystal that changes a traveling direction of light in a predetermined wavelength region; and a light receiving unit that is formed on an emission surface side of the photonic crystal and receives guided light in the photonic crystal and converts the light into a charge. It is characterized by.

Further, the photonic crystal has a flat dispersion surface with respect to the light in the predetermined wavelength region, thereby making the guided light into a parallel bundle.
By using such a photonic crystal, the traveling direction of light can be freely controlled. Therefore, it is possible to control the path of the light collected by the light collecting unit, to control light that is incident obliquely on the solid-state imaging device and goes in a direction that does not enter the light receiving unit without a photonic crystal, Since the light can be efficiently incident on the light receiving portion, a highly sensitive solid-state imaging device can be realized.

Further, the photonic crystal guides the guided light in a normal direction of a light receiving surface of the light receiving unit.
As a result, when there is no photonic crystal, the oblique light deviating from the light receiving portion is bent and reaches the light receiving portion, so that the sensitivity of the solid-state imaging device is increased.

In addition, a color filter layer is provided between the light condensing unit and the photonic crystal and allows only light in a predetermined wavelength region out of the condensed light to pass therethrough.
Thereby, it is possible to select a necessary color from the incident light, and at the same time, it is possible to secure a space in which the light is focused by the light collecting unit. Therefore, the light having a small diameter after the spot size is reduced is incident on the photonic crystal, and the incident light can be efficiently incident on the light receiving unit, thereby improving the sensitivity of the solid-state imaging device.
The exit surface of the photonic crystal is in contact with the light receiving surface of the light receiving unit.

As a result, it is possible to control the traveling direction of the emitted light of the photonic crystal up to the limit of the light receiving surface of the light receiving unit, thereby realizing a highly sensitive solid-state imaging device. If this structure is not used, the traveling direction of the light emitted from the photonic crystal is not controlled, so that the emitted light does not sufficiently enter the light receiving portion.
The incident surface of the photonic crystal is flat.

As a result, it is not necessary to create a flat layer for flattening the surface irregularities due to the formation of wiring and electronic elements with acrylic or the like, and the manufacturing process is reduced, so that the price of the solid-state imaging device can be reduced.
The predetermined wavelength region is set to a different wavelength region by changing at least one of the type, size, and arrangement interval of the constituent material of the photonic crystal.

The performance of the photonic crystal varies depending on the wavelength. This makes it possible to achieve an optimal photonic structure for each pixel corresponding to each color (wavelength), and to control the light traveling direction for each pixel. Can be optimized.
The focal position of the condensing part is on the incident surface of the photonic crystal.
Thereby, the light blocked by the light shielding layer can be reduced, and the sensitivity of the solid-state imaging device can be improved.

Furthermore, the central axis of the condensing part and the central axis of the opening of the light receiving part are parallel and separated from each other.
As described above, when the structure in which the center position of the light collecting portion and the center position of the opening portion of the light shielding layer do not coincide with each other is effective, it is mainly a case where oblique light is the main component, On the other hand, the light collection efficiency is reduced, but the light collection is improved for oblique light. That is, the sensitivity can be improved by using such a structure in the peripheral pixels of the image sensor.

Further, the photonic crystal is provided with a light shielding layer which is formed with an opening in the upper part of the light receiving part and which prevents light from entering the periphery of the light receiving part.
Such a formation structure of the photonic crystal and the light shielding layer enables the photonic crystal to control the light reaching the opening of the light shielding layer or the light before reaching the light shielding layer, thereby improving the sensitivity of the solid-state imaging device.

Further, when the focal length of the light collecting unit is f, the maximum value of the incident angle of the incident light is θ, and the opening width of the light shielding layer is W, the relationship f <W / (2 tan (θ)) is established. It is characterized by being satisfied.
As a result, almost 100% of the incident light can be taken into the light receiving section, and an extremely sensitive solid-state imaging device can be realized.

  Further, the photonic crystal is formed on the light receiving unit, and receives the collected light, and has a flat dispersion surface to guide the light in a direction perpendicular to the emission surface. And a light band gap in the wavelength region of light having a flat dispersion surface of the first photonic crystal and formed under the light shielding layer so as to surround the first photonic crystal. And a second photonic crystal that prevents the light from entering the periphery of the light receiving portion.

According to this structure, light that slightly leaks from the first photonic crystal (light existing between the light shielding layer and the light receiving portion) can be prevented from reaching the portion other than the light receiving portion and generating smear. High quality image can be obtained.
In addition, the photonic crystal is formed on the light receiving unit, and receives the collected light, and has a flat dispersion surface to guide the light in a direction perpendicular to the emission surface. The photonic crystal and the first photonic crystal are formed so as to cover the upper part of the photonic crystal and surround the upper part of the light receiving unit, and correspond to a flat dispersion surface of the first photonic crystal. And a second photonic crystal that has an optical bandgap in a wavelength region to prevent the light from entering the periphery of the light receiving unit.

A photonic crystal having an optical band gap has the same function as a light shielding layer because it does not allow light to enter. Therefore, this configuration eliminates the need for a light-shielding layer and can reduce the price of the solid-state imaging device.
Furthermore, the condensing part is any one of a micro lens, a Fresnel lens, a Fresnel zone plate, and a distributed refractive index type lens.

  The integration of the microlens in the solid-state imaging device is a technology that has already been established in mass production, and can reduce the price of the solid-state imaging device. Further, by using a Fresnel lens, a Fresnel zone plate, or a distributed refractive index type lens, the entire solid-state imaging device can be made thin, and a more advanced thin film structure can be realized.

Also, a solid-state imaging device manufacturing process, the step of forming the light receiving portion on a semiconductor substrate, the step of forming the photonic crystal on the light receiving portion, and the surface of the photonic crystal are flattened. And a step of forming the light shielding layer on the photonic crystal.
As a result, the space between the light shielding layer and the light receiving portion can be completely filled with the photonic crystal, and the surface of the photonic crystal is flattened, thereby eliminating the conventional flattening layer. can do.
Also, a solid-state imaging device manufacturing process, the step of forming the light receiving portion on a semiconductor substrate, the first photonic crystal step of forming the first photonic crystal on the light receiving portion, the first Forming the second photonic crystal around one photonic crystal.

Further, in the first photonic crystal process, after the first photonic crystal is formed on the entire surface, the portions other than the first photonic crystal above the light receiving portion are removed.
Alternatively, in the first photonic crystal process, the pattern for the first photonic crystal is used in an exposure process for designating a photonic crystal structure.
Thus, by setting the optical band gap of the second photonic crystal to the wavelength of the color handled by the pixel, a structure without a light-shielding layer can be formed, and the price of the solid-state imaging device can be reduced.

A method of manufacturing a solid-state imaging device, the step of forming the light receiving portion on a semiconductor substrate, the step of forming a flat layer and the light shielding layer on the light receiving portion, and a mask for the opening of the light shielding layer And forming a recess by cutting the flat layer to the light receiving surface of the light receiving section, and a photonic crystal process for forming the photonic crystal in the recess.
Thereby, the opening position and the position of the light receiving surface can be manufactured in the same process as the conventional solid-state imaging device, and the price of the solid-state imaging device can be reduced.

Furthermore, the photonic crystal process is characterized in that self-organization using polymer fine particles is used.
As a result, a photonic crystal can be manufactured in a place recessed by about 1 μm, and a solid-state imaging device can be manufactured stably.

  According to the solid-state imaging device according to the present invention, it is possible to improve sensitivity to obliquely incident light. By using this solid-state imaging device, it is possible to realize a short-focus imaging optical device, in other words, an ultra-thin imaging optical device, such as a mobile phone with an ultra-thin camera or an ultra-thin digital still camera. In addition, these portability increases. This is important in a ubiquitous network that handles many images.

Hereinafter, embodiments of the present invention will be described more specifically with reference to the drawings.
(Embodiment 1)
FIG. 1 is a diagram showing a cross-sectional view of a unit pixel of a solid-state imaging device according to Embodiment 1 of the present invention. An image sensor using this solid-state imaging device actually has 1280 × 1024 pixels as the number of pixels (about 1.3 million pixels, so-called SXGA compatible). FIG. 1 is a diagram showing a cross section of a unit pixel therein.

  Incident light enters from above the solid-state imaging device 200 shown in FIG. In the solid-state imaging device 200, a light receiving element 2 (silicon p-i-n structure) is formed on a silicon substrate 1. In addition to the opening above the light receiving element 2, an Al light shielding layer 3 is provided to prevent smear. There are a large number of wirings (usually 3 to 4 layers, made of Al, polycrystalline silicon, or the like) between the Al light shielding layer 3 and the silicon substrate 1, but the illustration is omitted here. Further, although a charge-coupled device (Charge-Coupled Device) for carrying charges generated in the light receiving element 2 is actually formed, the illustration is omitted. The photonic crystal 7 is formed on the silicon substrate 1 and the light receiving element 2 so as to embed the light shielding layer 3. On the photonic crystal 7, an acrylic layer 4 for securing a condensing distance, a color filter layer 5 for color separation, and a microlens 6 for condensing are formed. The focal position of the microlens 6 is adjusted to be the light receiving surface of the light receiving element 2. Even if the position of the incident surface of the photonic crystal 7 is substantially the same as that of the light shielding layer 3, the same effects as described below can be obtained.

FIG. 2 shows a specific structure of the blue photonic crystal 7. In this figure, light is incident at various angles from the left, and the right side is the emission side (light receiving surface side). A light shielding layer 3, an aluminum wiring layer, and the like are formed in a part of such a structure, but the illustration is omitted for simplicity. The photonic crystal 7 is a two-dimensional photonic crystal having a refractive index periodic structure in the X direction and the Z direction, and the refractive index is uniform in the Y direction. In SiO _{2 with} a refractive index of 1.45, spherical Si ₃ N ₄ (refractive index of 2.0) having a radius of 0.113 μm is three-dimensionally arranged in a square lattice shape, and 9 ₃ of Si ₃ N ₄ are arranged in the light traveling direction. Layers are formed. The interval between the spherical Si ₃ N ₄ is 0.25 μm.

  The dispersion surface of the blue photonic crystal 7 having such a structure is as shown in FIG. 3 (for the dispersion surface, for example, “Current State and Future Prospects of Photonic Crystal Research”, Optoelectronic Technology Promotion Association, Mar. See 2002.). That is, the light having a wavelength of 500 nm that is substantially blue has a substantially square dispersion surface. For light with a wavelength of 550 nm, which is almost green, it has a slightly concave dispersion surface, and for light with a wavelength of 600 nm, which is almost red, it has a further concave dispersion surface. When blue light is incident on the photonic crystal 7 having such a dispersion surface, the light travels in a direction perpendicular to the dispersion surface regardless of the incident angle. In the solid-state imaging device 200, since the light receiving element 2 is formed in a direction perpendicular to the blue dispersion surface, the blue light incident on the photonic crystal 7 becomes parallel guided light in the photonic crystal 7, and all It goes toward the light receiving element 2.

In the example of this photonic crystal, an example in which the dispersion surface is square with respect to the blue wavelength of 500 nm is shown, but by adjusting the size and arrangement interval of the spherical Si ₃ N ₄ or the type of material, the green wavelength and It is also possible to form photonic crystals each having a square dispersion plane with respect to the red wavelength. Therefore, RGB pixels can be configured by using these RGB photonic crystals, and therefore, an image sensor can be configured by combining these pixels.

  4 (a) and 4 (b) are diagrams schematically showing the state of light collection. 4A shows a case where normal incident light 9 enters the solid-state imaging device 200, and FIG. 4B shows a case where oblique incident light 10 enters. In FIG. 4A, the incident light 9 is collected by the microlens 6 and the spot diameter becomes smaller as it passes through the color filter layer 5 and the acrylic layer 4. However, when the light enters the photonic crystal 7, all light travels in a direction perpendicular to the light receiving surface of the light receiving element 2, so that all incident light passes through the opening of the light shielding layer 3 and reaches the light receiving element 2. . Compared with the conventional structure, the light collection is incomplete (the spot size is large), but the same function is achieved in that all the light reaches the light receiving element 2. On the other hand, in FIG. 4B, the oblique incident light 10 is condensed by the microlens 6 as described above, and the spot diameter decreases as it passes through the color filter layer 5 and the acrylic layer 4. When reaching the interface between the acrylic layer 4 and the photonic crystal 7, the light traveling direction is directed to the direction perpendicular to the light receiving surface of the light receiving element 2. For this reason, in the conventional structure, as shown in FIG. 17B, the light does not reach the light receiving element at all (due to the condensing effect of the microlens), as shown in FIG. Most of the light that is blocked by the light blocking layer reaches the light receiving element 2. That is, the sensitivity of the solid-state imaging device 200 to oblique light is improved.

  5A to 5D are diagrams showing measurement results of the light collection rate of the solid-state imaging device. In each case, the horizontal axis represents the incident angle, and the vertical axis represents the light collection rate (the case where all incident light enters the light receiving element 2 is 100%). The incident angle was measured in the range of 0 ° to 20 °. In the figure, “ML only” indicates a structure without a photonic crystal (the portion without a photonic crystal is embedded with acrylic), and “ML + PhC” indicates In the case of a structure with a photonic crystal.

  The length of one side of the pixel (approximately equal to the diameter of the microlens) is 4 μm, the space between the light receiving element 2 and the light shielding layer 3 is 1.5 μm, and the width of the window of the light shielding layer 3 (one side of the opening). Is 2 μm. The thickness of the color filter layer 5 is 0.3 μm. The thickness of the photonic crystal 7 is equal to the distance of 1.5 μm between the light receiving element 2 and the light shielding layer 3.

The four graphs shown in FIG. 5 correspond to those obtained by changing the focal length of the microlens 6 to 2 to 4 μm. In order to make the focal point of the microlens 6 coincide with the position on the light receiving surface of the light receiving element 2, the change in the focal length is the change in the thickness of the acrylic layer 4, thereby forming the structure of the solid-state imaging element. That is, the thickness of the acrylic layer 4 is 0.2 μm, 0.7 μm, 1.2 μm, and 2.2 μm with respect to the focal lengths of 2 μm, 2.5 μm, 3 μm, and 4 μm, respectively. As can be seen from FIG. 5, at any microlens focal length, the condensing rate is improved in the structure with the photonic crystal compared to the structure without the photonic crystal. In particular, on the wide-angle side, it is always improved by about 20%, and it can be seen that excellent condensing characteristics are obtained.
As described above, the solid-state imaging device according to the present invention achieves improvement in light collection efficiency with respect to obliquely incident light.

(Embodiment 2)
FIG. 6 shows a cross section of the solid-state imaging device according to Embodiment 2 of the present invention. The structure of the solid-state imaging device 201 is different from the first embodiment of the present invention in that the focal position of the microlens 12 is set not on the light receiving surface of the light receiving unit 2 but on the incident surface of the photonic crystal 7. .

  As shown in FIG. 6A, when the normal incident light 9 is incident on the solid-state imaging device 201, the incident light 9 is collected by the microlens 12, and when passing through the color filter layer 5 and the acrylic layer 4, the spot size Becomes smaller and focuses on the surface of the photonic crystal layer 7. In the photonic crystal 7, light travels in the vertical direction of the pixel, so that the light on the focal point travels to the light receiving element 2 with almost no change in spot size.

On the other hand, with respect to the obliquely incident light 10 as shown in FIG. 6B, it becomes the minimum spot on the surface of the photonic crystal 7, and the progress is changed in the direction of the light receiving element 2 without being blocked by the light shielding layer 3. Therefore, almost all light is incident on the light receiving element 2.
For reference, FIG. 7 shows a case where the light receiving surface of the light receiving element 2 is focused at the same microlens focal length. Here, in order to focus on the light receiving element 2, the thickness of the acrylic layer 14 is made thinner than the thickness of the acrylic layer 4 of the solid-state imaging element 201 shown in FIG. In the solid-state imaging device 202 shown in FIG. 7, it can be seen that a part of the light is blocked by the light blocking layer 3 and the amount of received light is reduced.

In such a structure, incident light can be received 100% by setting the focal length f to a certain value or less. That is, when the incident angle is θ, the spot is focused at a position shifted by f · tan (θ) from the center of the opening of the light shielding layer 3. Therefore, 100% light can be received if this focal position f is inside the opening of the light shielding layer 3, so when the size of the opening is W,
W / 2> f · tan (θ)
Satisfy this relationship. That is, substantially all of the incident light reaches the light receiving element 2 if f <W / (2 · tan (θ)) is substantially satisfied.
As described above, the solid-state imaging device according to the present invention realizes improvement in light collection efficiency with respect to obliquely incident light.

(Embodiment 3)
FIG. 8 shows a cross section of the solid-state imaging device according to Embodiment 3 of the present invention. In the solid-state imaging device 203 illustrated in FIG. 8, the center of the microlens 16 is disposed so as to be shifted from the center of the opening of the light shielding layer 3 in the direction in which the oblique light 10 comes. Thereby, almost all the oblique light 10 enters the light receiving element 2. Such a structure is effective when the oblique light is the main component in the incident light, and is particularly effective for the peripheral pixels among the pixels constituting the image sensor, for example.

  In some cases, the microlens 16 may be manufactured with a deviation in the manufacturing process. In this case as well, the light is efficiently guided to the light receiving element 2 by the action of the photonic crystal 7, so that the solid-state imaging element is more than conventional. Yield is improved.

(Embodiment 4)
FIG. 9 shows a cross section of the solid-state imaging device according to Embodiment 4 of the present invention. In the solid-state imaging device 204, the photonic crystal 7 hardly exists under the light shielding layer 3, and the acrylic layer 17 is formed there, which is different from the above embodiment. By adopting such a structure, as will be described later, since the current manufacturing process of the solid-state image sensor can be used as it is, a solid-state image sensor can be manufactured at a low cost.

(Embodiment 5)
FIG. 10 shows a cross section of the solid-state imaging device according to the fifth embodiment of the present invention. The solid-state imaging device 205 is different from the above-described embodiment in that another photonic crystal 18 different from the photonic crystal 7 is formed under the light shielding layer 3. The photonic crystal 18 has an optical band gap with respect to the color (wavelength region) handled by the solid-state imaging device, and can prevent light from leaking in the direction of the photonic crystal 18. Light efficiency can be increased.

(Embodiment 6)
FIG. 11 shows a cross section of the solid-state imaging device according to the sixth embodiment of the present invention. The solid-state image sensor 206 has a structure without the light shielding layer 3 of the solid-state image sensor 205 shown in FIG. Since the photonic crystal 18 has an optical band gap, the photonic crystal 18 can be used as a substitute for the light shielding layer, so that it is not necessary to form the light shielding layer. Thereby, a solid-state image sensor can be manufactured at low cost.

(Embodiment 7)
FIG. 12 is a diagram for explaining the first manufacturing method of the solid-state imaging device according to the present invention.
First, as shown in FIG. 12A, the light receiving element 2 and various wirings (not shown in the figure) are formed on the silicon substrate 1.
Thereafter, as shown in FIG. 12B, a photonic crystal 7 is formed thereon by repeating electron beam exposure and CVD, as will be described later. In order to improve the degree of flatness of the surface of the photonic crystal 7, CMP (chemical mechanical polishing) is used, and the surface roughness (RMS) is flattened to 2 nm or less. By doing so, it is possible to substitute the flat layer with the photonic crystal 7, so that it is not necessary to form a flattening layer on the photonic crystal 7. For this reason, manufacturing man-hours can be reduced.

Thereafter, as shown in FIG. 12 (c), an aluminum light-shielding layer 3 is formed on the photonic crystal 7 in a portion other than the opening of the light-receiving portion 2, and an acrylic film is formed thereon as shown in FIG. 12 (d). Layer 4, color filter layer 5, and microlens layer 6 are sequentially formed to complete.
In order to increase the period of the structure of the photonic crystal 7, the photonic crystal 7 may be formed again after forming the light shielding layer 3. In such a case, the structure of the solid-state imaging device as shown in FIG. 1 is completed.

(Embodiment 8)
FIG. 13 is a diagram for explaining a second manufacturing method of the solid-state imaging device according to the present invention. As shown in FIGS. 13A and 13B, the steps up to the formation of the photonic crystal 7 are the same as those in FIGS. 12A and 12B. However, as shown in FIG. In the nick crystal 7, only the part above the light receiving part 2 is left and the other part is removed. Thereafter, as shown in FIG. 13D, a second photonic crystal 18 is formed around the photonic crystal 7. Accordingly, the photonic crystal 7 on the light receiving unit 2 and the second photonic crystal 18 around the photonic crystal 7 have different functions (that is, the second photonic crystal 18 has a function of substituting the light shielding layer). Can do.

  Note that when a photonic crystal pattern is produced by exposure such as photolithography, the same structure can be obtained by simply changing the exposure pattern without cutting the photonic crystal 7 as shown in FIG. 13C. Can be manufactured.

(Embodiment 9)
FIG. 14 is a diagram for explaining a third manufacturing method of the solid-state imaging device according to the present invention. First, as shown in FIG. 14A, the light receiving portion 2 and various wirings (not shown in the figure) are formed on the silicon substrate 1. Thereafter, as shown in FIG. 14 (b), an acrylic resin 17 is formed thereon, and then, as shown in FIG. 14 (c), the light shielding layer 3 is formed in a portion other than the opening of the light receiving portion 2 thereon. To do. Up to this point, the process is the same as that of a normal solid-state imaging device, and is a very stable process. Thereafter, as shown in FIG. 14D, only the acrylic layer 17 on the light receiving portion 2 is removed by dry etching. At this time, the light shielding film 3 can be used as a mask. Next, as shown in FIG. 14 (e), a photonic crystal 7 is formed thereon by self-assembly of polymer fine particles (for example, K. Fukuda, H. -B. Sun , S. Matsuno, and H. Misawa, “Self-organizing three-dimensional colloidal photonic structure with argumented dielectric contrast,” Jpn, J. Appl. Phys. 37, (1998) L508.). In order to produce the photonic crystal 7 in such a depression, self-organization of polymer fine particles is optimal. Finally, as shown in FIG. 14 (f), the acrylic layer 4, the color filter layer 5 and the microlens layer 6 are sequentially formed thereon to complete.

(Embodiment 10)
The following method is mainly used for manufacturing the photonic crystal according to the present invention.
FIG. 15 shows a method of manufacturing a photonic crystal structure by etching a multilayer film layer. As shown in FIG. 15A, first, a multilayer film structure in which 9 sets are deposited on a SiO ₂ substrate 906 by using a CVD method with a pair of Si ₃ N ₄ layer 904 and SiO ₂ layer 905 as one set. Form. Next, after forming a circular resist 903 using electron beam lithography, as shown in FIG. 15B, etching is performed using a normal etching process so that a cylindrical multilayer film remains. Next, as shown in FIG. 15C, after removing the resist using acetone, a SiO ₂ coating material is applied and heated by spin coating, and Si ₃ N ₄ fine particles 904 are placed in the SiO ₂ matrix 907. Form a photonic crystal regularly arranged.

In the above description, the acrylic layer 4 is provided for condensing the microlens 6. However, a method of substituting this with the color filter layer 5, that is, a method of increasing the thickness of the color filter layer 5 may of course be used. .
In this embodiment, a CCD is used, but a MOS sensor may of course be used. Of course, the solid-state imaging device may be manufactured using a manufacturing method other than that described.

  According to the solid-state imaging device according to the present invention, a solid-state imaging device having high sensitivity can be realized even for a wide-angle optical system. Applicable to cameras.

It is sectional drawing of the solid-state image sensor which concerns on Embodiment 1 of this invention. 1 is a structural diagram of a photonic crystal according to a first embodiment of the present invention. It is a figure which shows the optical function of the photonic crystal which concerns on Embodiment 1 of this invention. (A) And (b) is a figure which shows the mode of condensing in the solid-state image sensor which concerns on Embodiment 1 of this invention. (A)-(d) is the figure which compared the condensing rate of the solid-state image sensor which concerns on Embodiment 1 of this invention, and the solid-state image sensor of a conventional structure. (A) And (b) is sectional drawing of the solid-state image sensor which concerns on Embodiment 2 of this invention. It is sectional drawing of the solid-state image sensor concerning Embodiment 2 of this invention, and is a figure in case a microlens focal distance is short. It is sectional drawing of the solid-state image sensor which concerns on Embodiment 3 of this invention. It is sectional drawing of the solid-state image sensor which concerns on Embodiment 4 of this invention. It is sectional drawing of the solid-state image sensor which concerns on Embodiment 5 of this invention. It is sectional drawing of the solid-state image sensor which concerns on Embodiment 6 of this invention. (A)-(d) is a figure which shows the 1st manufacturing method of the solid-state image sensor which concerns on Embodiment 7 of this invention. (A)-(d) is a figure which shows the 2nd manufacturing method of the solid-state image sensor which concerns on Embodiment 8 of this invention. (A)-(f) is a figure which shows the 3rd manufacturing method of the solid-state image sensor which concerns on Embodiment 9 of this invention. (A)-(c) is a figure which shows the manufacturing method of the photonic crystal which concerns on Embodiment 10 of this invention. It is a figure which shows the cross section of the conventional solid-state image sensor. (A)-(g) is a figure which shows the manufacturing method of the conventional solid-state image sensor. (A) And (b) is a figure which shows the mode of condensing of the conventional solid-state image sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,101 Silicon substrate 2,102 Light receiving element 3,103 Light-shielding layer 4,14,104,111 Acrylic layer 5,105 Color filter layer 6,12,16,106 Micro lens 7,17,18 Photonic crystal 9,107 Light vertically incident on the pixel 10, 108 Light obliquely incident on the pixel 200 to 206, 230 Solid-state imaging device 903 Resist 904 Si ₃ N ₄ layer 905 SiO ₂ layer 906 SiO ₂ substrate 907 SiO ₂

Claims (21)

A condensing part for condensing incident light;
A photonic crystal that is formed on the exit surface side of the condensing unit, enters the condensed light, and changes the traveling direction of light in a predetermined wavelength region;
A solid-state imaging device, comprising: a light receiving portion that is formed on an emission surface side of the photonic crystal and that receives guided light in the photonic crystal and converts the light into a charge. 2. The solid-state imaging device according to claim 1, wherein the photonic crystal has a flat dispersion surface with respect to light in the predetermined wavelength region, thereby making the guided light a parallel bundle. 3. The solid-state imaging device according to claim 2, wherein the photonic crystal guides the guided light in a normal direction of a light receiving surface of the light receiving unit. Furthermore, the color filter layer which is formed between the said condensing part and the said photonic crystal, and allows only the light of a predetermined wavelength area among the condensed light is provided is provided. The solid-state imaging device according to any one of 3. 5. The solid-state imaging device according to claim 1, wherein an emission surface of the photonic crystal is in contact with a light receiving surface of the light receiving unit. The solid-state imaging device according to claim 1, wherein an incident surface of the photonic crystal is flat. The predetermined wavelength region is set to a different wavelength region by changing at least one of the type, size, and arrangement interval of the constituent material of the photonic crystal. The solid-state image sensor of any one of -6. The solid-state image sensor according to any one of claims 1 to 7, wherein a focal position of the condensing part is on an incident surface of the photonic crystal. 9. The solid-state imaging device according to claim 1, wherein a central axis of the light collecting unit and a central axis of the opening of the light receiving unit are parallel and separated. Furthermore, the photonic crystal is provided with a light shielding layer which is formed with an opening in the upper part of the light receiving part and prevents light from entering the periphery of the light receiving part. The solid-state image sensor of any one of -9. When the focal length of the condensing part is f, the maximum value of the incident angle of the incident light is θ, and the opening width of the light shielding layer is W,
f <W / (2tan (θ))
The solid-state imaging device according to claim 10, wherein the relationship is satisfied. The solid-state imaging device according to claim 10, further comprising an acrylic layer formed so as to surround the photonic crystal on the light receiving portion, below the light shielding layer. The photonic crystal is
A first photonic crystal formed on an upper portion of the light receiving unit, which receives the condensed light and has a flat dispersion surface, thereby guiding the light in a direction perpendicular to the emission surface;
A light band gap is formed below the light shielding layer so as to surround the first photonic crystal and has a light band gap in a light wavelength region having a flat dispersion surface of the first photonic crystal, thereby allowing the light receiving unit to The solid-state imaging device according to claim 10, further comprising: a second photonic crystal that prevents the light from entering the periphery of the solid-state image sensor. The photonic crystal is
A first photonic crystal formed on an upper portion of the light receiving unit, which receives the condensed light and has a flat dispersion surface, thereby guiding the light in a direction perpendicular to the emission surface;
An optical band gap in the wavelength region of light that is covered with the first photonic crystal and surrounds the upper portion of the light receiving portion and corresponds to a flat dispersion surface of the first photonic crystal. The solid-state imaging device according to claim 1, further comprising: a second photonic crystal that prevents the light from entering the periphery of the light receiving unit. The solid-state imaging device according to claim 1, wherein the condensing unit is any one of a micro lens, a Fresnel lens, a Fresnel zone plate, and a distributed refractive index type lens. It is a manufacturing process of the solid-state image sensing device according to claim 10,
Forming the light receiving portion on a semiconductor substrate;
Forming the photonic crystal on the light receiving portion;
Planarizing the surface of the photonic crystal;
And a step of forming the light shielding layer on the photonic crystal. It is a manufacturing process of the solid-state image sensing device according to claim 14,
Forming the light receiving portion on a semiconductor substrate;
A first photonic crystal step of forming the first photonic crystal on the light receiving portion;
Forming the second photonic crystal around the first photonic crystal. A method for manufacturing a solid-state imaging device. 18. In the first photonic crystal process, after the first photonic crystal is formed on the entire surface, parts other than the first photonic crystal above the light receiving portion are removed. Manufacturing method of solid-state image sensor. The method for manufacturing a solid-state imaging device according to claim 17, wherein, in the first photonic crystal process, the pattern for the first photonic crystal is used in an exposure process for designating a photonic crystal structure. It is a manufacturing method of the solid-state image sensing device according to claim 12,
Forming the light receiving portion on a semiconductor substrate;
Forming a flat layer and the light shielding layer on the light receiving portion;
Forming a recess by scraping the flat layer to the light receiving surface of the light receiving portion using the opening of the light shielding layer as a mask;
And a photonic crystal process for forming the photonic crystal in the recess. 21. The method of manufacturing a solid-state imaging device according to claim 20, wherein the photonic crystal process uses self-assembly by polymer fine particles.

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