JP2008091800A - Imaging device, manufacturing method thereof, and imaging system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that in an imaging device having a light waveguide, light reflection is generated owing to the refractive index difference between the light waveguide and a photoelectric conversion part, thereby decreasing the light utilization efficiency. <P>SOLUTION: The imaging device 1 has a photoelectric conversion means 11 to convert light to a signal charge to accumulate the charge, a microlens 53 to condensing light on the photoelectric conversion means 11, and the light waveguide 41 between the microlens 53 and the photoelectric conversion means 11. Between the light waveguide 41 and the photoelectric conversion means 11, a plurality of reflection preventing layers 20, 40, 23 having different structures are disposed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image sensor used for a digital still camera, a manufacturing method thereof, and an image pickup system.

  In recent years, image sensors used in digital still cameras and the like have been increased in resolution due to an increase in the number of pixels, but have been reduced in price by reducing the chip size. For this reason, the size of the pixels constituting the imaging element is decreasing year by year, and the area of the photoelectric conversion unit is also decreasing accordingly.

When an image sensor having a small area of the photoelectric conversion unit is used, it is difficult to obtain a high-quality image when a dark subject is imaged. Therefore, Patent Document 1 discloses an imaging device in which an antireflection layer is provided on the surface of the photoelectric conversion unit in order to improve the incident light efficiency to the photoelectric conversion unit of the imaging device. In Patent Document 1, an interface between a photoelectric conversion portion made of silicon (Si: refractive index of about 4.1) and an insulating film made of silicon oxide (SiO ₂ : refractive index of about 1.46) covering the photoelectric conversion portion. A configuration for preventing reflection on the screen is disclosed. That is, a silicon nitride (SiN: refractive index is about 2.0) layer having an intermediate refractive index is disposed between silicon (Si) and silicon oxide (SiO ₂ ).

Patent Document 2 further discloses an imaging device in which a light guide is provided between the light incident surface and the photoelectric conversion unit to improve the light collection characteristics in order to improve the light capturing efficiency with a large incident angle. In Patent Document 2, an optical waveguide made of silicon nitride (SiN), which is a high refractive index material, is provided on the light incident side of the photoelectric conversion unit, and the surrounding interlayer insulating film layer is made of BPSG (refractive index material). The rate is about 1.46). Condensing characteristics are improved by totally reflecting incident light at these boundary surfaces. A low reflection film made of silicon nitride that functions as an etching stopper film when the optical waveguide is formed is disposed between the light emitting side of the optical waveguide and the photoelectric conversion portion.
JP 63-14466 (2nd page, FIG. 5) JP 2000-150845 A (page 3, FIG. 1)

  However, in the imaging device disclosed in Patent Document 2, the low reflection film formed between the optical waveguide and the photoelectric conversion unit is made of silicon nitride, which is the same material as the optical waveguide. There is a drawback that the reflection at the interface with the part is not sufficiently prevented.

  The light incident side of the optical waveguide made of silicon nitride is a color filter layer having a relatively low refractive index (refractive index of about 1.5) through a passivation film usually formed of silicon nitride. Because of the difference in refractive index, reflection occurs.

  FIG. 8 is a diagram illustrating the spectral characteristics of light incident on the photoelectric conversion unit in a conventional imaging device that does not have an antireflection structure on the light incident surface and the light exit surface of the optical waveguide. As is apparent from FIG. 8, the intensity of light reaching the photoelectric conversion unit varies depending on the wavelength due to the interference effect of the reflected light on the light incident surface and the light exit surface of the optical waveguide. The wavelength characteristic varies due to variations in the thickness of the optical waveguide. As a result, when a subject illuminated with a light source having a bright line such as a fluorescent lamp is imaged, there is a drawback in that the generated image has uneven color due to variations in the thickness of the optical waveguide.

  The present invention has been made in view of the above problems, and is characterized by enhancing the antireflection effect of the antireflection layer.

  According to a first aspect of the present invention, there is provided a photoelectric conversion unit that converts light into a signal charge and stores it, a microlens that condenses the light on the photoelectric conversion unit, and the microlens and the photoelectric conversion unit. The present invention relates to an image pickup device having an optical waveguide, wherein a plurality of antireflection layers having different configurations are arranged between the optical waveguide and the photoelectric conversion means.

  According to a second aspect of the present invention, there is provided a photoelectric conversion unit that converts light into signal charges and stores it, a microlens that condenses light on the photoelectric conversion unit, and a gap between the microlens and the photoelectric conversion unit. The present invention relates to a method of manufacturing an image pickup device having an optical waveguide, a step of forming a first thin film on a substrate, a step of forming a second thin film on the first thin film, and an interlayer on the second thin film. Forming an insulating film; forming an opening for forming the optical waveguide in the interlayer insulating film; forming a third thin film on the opening of the interlayer insulating film; Filling the opening with an optical waveguide material.

  A third aspect of the present invention relates to an imaging system, and includes an optical system and the imaging device described above.

  According to the present invention, the antireflection effect of the antireflection layer can be enhanced.

(First embodiment)
FIG. 1 is a schematic cross-sectional view of a CMOS type image sensor according to a preferred embodiment of the present invention. In FIG. 1, the cross section of one pixel of the image sensor 1 is exemplarily shown, but the number of pixels of the image sensor 1 is not limited to this.

  The imaging device 1 includes a photoelectric conversion unit (photoelectric conversion means) 11 formed inside a silicon substrate 10. The surface of the silicon substrate 10 is covered with an insulating film 20 made of silicon oxide. In order to transfer the signal charges generated in the photoelectric conversion unit 11 to a floating diffusion unit (not shown), the first electrode 12 is disposed on the silicon substrate 10 so as to partially overlap the photoelectric conversion unit 11. Further, an etching stopper film 40 made of silicon nitride is formed so as to cover the photoelectric conversion portion 11 and a part of the electrode 12. Further, in order to selectively output the signal charge transferred to the floating diffusion portion (not shown) to the outside, the first interlayer insulating film 21 and the second interlayer insulating film 22 made of silicon oxide are sandwiched between the first and second interlayer insulating films 22. Two electrodes 30 and a third electrode 31 are provided.

  An optical waveguide 41 made of silicon nitride is formed in a region where the second electrode 30 and the third electrode 31 are opened. An insulating film 23 made of silicon oxide is formed around the optical waveguide 41. A passivation film 42 made of silicon nitride is formed on the light incident side of the optical waveguide 41, and an antireflection film for preventing reflection that occurs at the interface with the planarizing layer 50, which is a resin material. 43 is formed. On the light incident side of the flattening layer 50, a color filter 51, a flattening layer 52, and a microlens 53 are formed of a resin material.

  The light incident on the image sensor 1 is condensed on the optical waveguide 41 by the microlens 53. Since the optical waveguide 41 is made of silicon nitride, its refractive index is about 1.9. The periphery of the optical waveguide 41 is surrounded by the insulating film 23 and the interlayer insulating films 22 and 21 having a refractive index of about 1.46. Therefore, the light reaching the wall surface of the optical waveguide 41 is totally reflected at the interface between the insulating film 23 and the interlayer insulating films 22 and 21 and is guided to the photoelectric conversion unit 11. Here, a single-layer antireflection film 43 is formed on the light incident surface of the optical waveguide 41.

  The antireflection film 43 made of silicon oxynitride (SiON) has a light incident surface of the optical waveguide 41 through the passivation film 42 and a planarizing layer 50 formed of a resin having a refractive index of about 1.5. Prevent reflections. When the refractive index of the antireflection film 43 is 1.70 and the thickness is 750 mm, the transmittance at the light incident surface of the optical waveguide 41 is about 98%.

In addition, an antireflection layer composed of three thin films is formed on the light exit surface of the optical waveguide 41. Between the optical waveguide 41 and the photoelectric conversion unit 11, the insulating film 20 that is the first thin film, the etching stopper film 40 that is the second thin film, and the insulating film 23 that is the third thin film from the photoelectric conversion unit 11 side. Is formed. The insulating film 20, which is the first thin film that acts as an antireflection film, is made of silicon oxide, and has a refractive index n1 of 1.46 and a thickness d1 of, for example, 100 mm. Similarly, the etching stopper film 40, which is the second thin film, is made of silicon nitride, and has a refractive index n2 of 2.0 and a thickness d2 of 600 mm, for example. Further, the insulating film 23 which is the third thin film is made of silicon oxide, and has a refractive index n3 of 1.46 and a thickness d3 of 350 mm, for example. The third insulating film 23 may be made of silicon oxynitride (SiON) having a refractive index of 1.6 to 1.7.
Since the insulating film 23 is formed on the surface of the hole for forming the optical waveguide 41, if the thickness d3 is thick, the hole may be blocked. Therefore, the thickness d3 of the insulating film 23 must be reduced. However, in order to obtain the antireflection effect, a predetermined optical thickness (generally n · d = wavelength / 4) is required. Therefore, it is preferable to reduce the thickness d3 of the insulating film 23 while increasing the refractive index n3 and satisfy n3 ≧ n1. The refractive index n2 of the etching stopper film 40 is preferably higher than the refractive index of either the insulating film 20 or the insulating film 23 in order to increase the antireflection effect. Thus, the antireflection effect by each thin film can be realized by configuring the relationship between the refractive indexes of the respective thin films constituting the antireflection layer so as to satisfy the following Expression 1.

n2> n3 ≧ n1 (Formula 1)
By configuring so that the relationship between the refractive indexes of the respective thin films constituting the antireflection layer satisfies Expression 1, the transmittance of the light exit surface of the optical waveguide 41 is about 95%.
In addition, among the three thin films constituting the antireflection layer, the etching stopper film 40 made of silicon nitride is made the thickest so that the first formed between the etching stopper film 40 and the optical waveguide 41. The film thickness of the third thin film 23 can be further reduced. Thereby, manufacture of the optical waveguide 41 becomes easy.

  FIG. 2 is a diagram showing the spectral transmittance of the optical waveguide 41 of the imaging device 1 provided with the antireflection layers having different configurations on the light incident surface and the light emitting surface of the optical waveguide 41 as described above.

  The optical waveguide 41 having the antireflection layer is configured to obtain a transmittance of about 90% in the visible light region. In addition, since the variation in transmittance due to the difference in wavelength is small, even if an object illuminated with a light source having a bright line such as a fluorescent lamp is imaged, color unevenness due to the variation in the thickness of the optical waveguide 41 is almost generated. do not do. As a result, a high-quality image can be obtained.

  3 and 4 are diagrams for explaining a method of manufacturing the CMOS type image pickup device 1 according to the preferred embodiment of the present invention. 3 and 4 exemplify the cross-sectional structure of one pixel near the center of the image sensor 1, other pixels can be manufactured in the same manner.

  First, in the step shown in FIG. 3A, ions are implanted into the photoelectric conversion region of the silicon substrate 10 to form the photoelectric conversion unit 11. Then, the silicon substrate 10 is thermally oxidized to form an insulating film 23 made of silicon oxide on the silicon substrate surface. The thickness of the insulating film 23, which is the first thin film of the antireflection layer formed between the light exit surface of the optical waveguide 41 and the photoelectric conversion unit 11, is, for example, 100 mm. Further, a polysilicon film is formed on the insulating film 23.

  In the step shown in FIG. 3B, after forming a polysilicon film, a photoresist 100 is applied, and an exposure process and a development process are performed to form a polysilicon electrode pattern using the photoresist.

  In the step shown in FIG. 3C, the first electrode 12 is formed by etching polysilicon. When the first electrode 12 is formed, a silicon nitride film is formed and an etching stopper film 40 is formed. The etching stopper film 40 has a function of stopping the etching of the interlayer insulating films 21 and 22 when the optical waveguide 41 is formed, and also functions as a second thin film of the antireflection layer. The anti-reflection layer is formed so that the anti-reflection effect can be obtained even when the third thin film 23 formed between the etching stopper film 40 and the optical waveguide 41 is thin. Of the three thin films, the thickest film thickness is preferable. The actual thickness of the etching stopper film 40 is set according to the etching amount of the interlayer insulating films 21 and 22. For example, when the etching amount of the interlayer insulating films 21 and 22 is 400 mm, the film thickness of the etching stopper film 40 to be formed is 1000 mm, for example.

  In the step shown in FIG. 3D, after the etching stopper film 40 is formed, a photoresist 101 is formed, and an exposure process and a development process are performed to form a pattern of the etching stopper film using the photoresist. .

  In the step shown in FIG. 3E, the etching stopper film 40 is etched to form the etching stopper film 40 in the region where the optical waveguide 41 is formed.

  In the step shown in FIG. 3F, when the etching stopper film 40 is formed, the first interlayer insulating film 21 for forming the second electrode is formed, and planarization is performed. The first interlayer insulating film 21 is made of silicon oxide having a refractive index of about 1.46. A second electrode 30 made of aluminum is formed on the planarized first interlayer insulating film 21. Further, a second interlayer insulating film 22 for forming the third electrode is formed, and planarization is performed. The second interlayer insulating film 22 is also formed of silicon oxide having a refractive index of about 1.46. A third electrode 31 made of aluminum is formed on the planarized second interlayer insulating film 22.

  In the step shown in FIG. 3G, a planarized second interlayer is formed to form an opening for forming the optical waveguide 41 in the first interlayer insulating film 21 and the second interlayer insulating film 22. A photoresist 102 is applied on the insulating film 22. Then, exposure processing and development processing are performed using a photomask (not shown).

  In the step shown in FIG. 3H, an opening for forming the optical waveguide 41 in the second interlayer insulating film 22 and the first interlayer insulating film 21 by performing a dry etching process using the photoresist 102 as a mask. Form. At this time, an etching stopper film 40 is formed between the second interlayer insulating film 22 and the photoelectric conversion unit 11. Therefore, the etching stopper film 40 stops etching while leaving a predetermined film thickness (for example, 600 mm).

  In the step shown in FIG. 4I, when an opening for forming the optical waveguide 41 is formed in the interlayer insulating films 21 and 22, the optical waveguide 41 is formed inside the opening for forming the optical waveguide 41. A third thin film (silicon oxide film) 23 that functions as an antireflection layer on the light emission surface is formed. Here, when the thickness of the silicon oxide film formed on the inside of the opening is thick, silicon oxide is stacked on the opening and the opening is narrowed. Therefore, it becomes impossible to form the optical waveguide in the subsequent process of forming the optical waveguide.

  Therefore, in the imaging device 1 according to the present embodiment, the thickness of the insulating film 23 that is the third thin film is increased by increasing the thickness of the etching stopper film 40 that is the second thin film constituting the antireflection layer. The antireflection effect is obtained by making it relatively thin. In this embodiment, the film thickness of the insulating film 23 formed of silicon oxide is, for example, 350 mm, and can be formed without narrowing the opening.

  In the step shown in FIG. 4J, silicon nitride is formed in the opening covered with the insulating film 23 made of silicon oxide, and the optical waveguide 41 is formed. Silicon nitride is formed by, for example, a high density plasma CVD method, and its refractive index is about 1.9. After the optical waveguide 41 is formed, a planarization process is performed to form a passivation film 42. The passivation film 42 is a silicon nitride film usually formed by a plasma CVD method and has a refractive index of about 2.0.

  In the step shown in FIG. 4K, an antireflection layer for the light incident surface of the optical waveguide 41 is formed on the passivation film 42. The antireflection layer for the light incident surface of the optical waveguide 41 is composed of a single antireflection film 43 and prevents reflection caused by a difference in refractive index from the planarization layer 50 for forming the color filter 51. The antireflection film 43 is silicon oxynitride having a refractive index of about 1.7, and is formed to a thickness of, for example, 750 mm. When the antireflection film 43 is formed, the planarization layer 50 for forming the color filter 51 is formed, and then the color filter 51 is formed. Furthermore, after the planarization layer 52 for forming the microlens 53 is formed, the microlens 53 is formed. The microlens 53 is formed by, for example, a known registry flow method.

In the present embodiment, the example in which the passivation film 42 is formed after the optical waveguide 41 is formed is shown. However, the light incident side layer of the optical waveguide 41 is configured so as to also serve as the passivation film 42. It doesn't matter.
(Second Embodiment)
FIG. 5 is a schematic cross-sectional view of a CMOS image sensor according to a preferred embodiment of the present invention. Constituent elements similar to those in FIG. In FIG. 5, the cross section of one pixel of the image sensor 51 is exemplarily shown, but the number of pixels of the image sensor 51 is not limited to this.

  The image sensor 51 includes a photoelectric conversion unit 11 formed inside the silicon substrate 10. The surface of the silicon substrate 10 is covered with an insulating film 20 made of silicon oxide. In order to transfer the signal charges generated in the photoelectric conversion unit 11 to a floating diffusion unit (not shown), the first electrode 12 is disposed on the silicon substrate 10 so as to partially overlap the photoelectric conversion unit 11. Further, an etching stopper film 40 made of silicon nitride is formed so as to cover the photoelectric conversion portion 11 and a part of the electrode 12. Further, in order to selectively output the signal charge transferred to the floating diffusion portion (not shown) to the outside, the first interlayer insulating film 21 and the second interlayer insulating film 22 made of silicon oxide are sandwiched between the first and second interlayer insulating films 22. Two electrodes 30 and a third electrode 31 are provided.

  An optical waveguide 41 made of silicon nitride is formed in a region where the second electrode 30 and the third electrode 31 are opened. An insulating film 23 made of silicon oxide is formed around the optical waveguide 41. A passivation film 42 made of silicon nitride is formed on the light incident side of the optical waveguide 41, and an antireflection film for preventing reflection that occurs at the interface with the planarizing layer 50, which is a resin material. 43 is formed. On the light incident side of the flattening layer 50, a color filter 51, a flattening layer 52, and a microlens 53 are formed of a resin material.

  The light incident on the image sensor 51 is condensed on the optical waveguide 41 by the microlens 53. Since the optical waveguide 41 is made of silicon nitride, its refractive index is about 1.9. The periphery of the optical waveguide 41 is surrounded by the insulating film 23 and the interlayer insulating films 22 and 21 having a refractive index of about 1.46. Therefore, the light reaching the wall surface of the optical waveguide 41 is totally reflected at the interface between the insulating film 23 and the interlayer insulating films 22 and 21 and is guided to the photoelectric conversion unit 11. Here, a single-layer antireflection film 43 is formed on the light incident surface of the optical waveguide 41.

  The antireflection film 43 made of silicon oxynitride (SiON) prevents reflection between the light incident surface of the optical waveguide 41 and the planarization layer 50 made of a resin having a refractive index of about 1.5. When the refractive index of the antireflection film 43 is 1.70 and the thickness is 750 mm, the transmittance at the light incident surface of the optical waveguide 41 is about 99%.

  In addition, an antireflection layer composed of three thin films is formed on the light exit surface of the optical waveguide 41. Between the optical waveguide 41 and the photoelectric conversion unit 11, the insulating film 20 that is the first thin film, the high refractive index absorption film 13 that is the second thin film, and the etching that is the third thin film from the photoelectric conversion unit 11 side. A stopper film 40 is formed. The insulating film 20, which is the first thin film that acts as an antireflection film, is made of silicon oxide, and has a refractive index n1 of 1.46 and a thickness d1 of, for example, 100 mm. Similarly, the high refractive index absorption film 13 as the second thin film is made of polysilicon, and the refractive index n2 is 4.0 and the thickness d2 is, for example, 50 mm. Further, the etching stopper film 40 as the third thin film is made of silicon nitride, and has a refractive index n3 of 2.0 and a thickness d3 of 450 mm, for example.

  Thus, the antireflection effect by each thin film can be realized by configuring the relationship between the refractive indexes of the respective thin films constituting the antireflection layer so as to satisfy the above-described Expression 1.

  By configuring so that the relationship between the refractive indexes of the respective thin films constituting the antireflection layer satisfies Expression 1, the transmittance of the light exit surface of the optical waveguide 41 is about 95%.

  Of the three thin films constituting the antireflection layer, the thickness of the etching stopper film 40 made of silicon nitride is maximized, whereby the first film formed between the etching stopper film 40 and the insulating film 20 is formed. The thickness of the high refractive index absorption film 13 can be reduced. Thereby, reflection and absorption of light between the light exit surface of the optical waveguide 41 and the photoelectric conversion unit 11 can be reduced.

  FIG. 6 is a diagram illustrating the spectral transmittance of the optical waveguide 41 in the imaging element 51 provided with the antireflection layers having different configurations on the light incident surface and the light emitting surface of the optical waveguide 41 as described above. As shown in FIG. 7, the optical waveguide 41 having the antireflection layer according to the preferred embodiment of the present invention has a transmittance of about 93% in the visible light region. Also, the difference in transmittance due to the difference in wavelength is small. Therefore, even when a subject illuminated with a light source having a bright line such as a fluorescent lamp is imaged, color unevenness due to variations in the thickness of the optical waveguide 41 hardly occurs, and a high-quality image can be obtained. .

  In the present embodiment, an example in which polysilicon is used for the second thin film of the antireflection layer formed on the light exit surface of the optical waveguide 41 is shown, but amorphous silicon may be used.

  FIG. 7 is a diagram showing an outline of an imaging system using a CMOS type imaging device according to a preferred embodiment of the present invention. Reference numeral 501 denotes a lens unit (noted as “lens” in FIG. 7), 502 a lens driving unit, 503 a mechanical shutter (denoted mechanical shutter), and 504 a mechanical shutter driving unit (“shutter driving unit” in FIG. 7). 505) denotes an A / D converter. Reference numeral 200 denotes an image pickup unit in which a plurality of CMOS image pickup devices according to a preferred embodiment of the present invention are arranged. Reference numeral 506 denotes an imaging signal processing circuit, 507 denotes a timing generation unit, 508 denotes a memory unit, 509 denotes a control unit, 510 denotes a recording medium control interface unit (indicated as “recording medium control I / F unit” in FIG. 7), 511. Indicates a display. Reference numeral 512 denotes a recording medium, 513 denotes an external interface unit (indicated as “external I / F unit” in FIG. 7), 514 denotes a photometric unit, and 515 denotes a distance measuring unit. The imaging signal processing circuit 506 includes a WB circuit 516 that performs white balance processing based on a signal from the A / D converter 505.

  The subject image that has passed through the lens unit 501 is formed in the vicinity of the imaging unit 200. A subject image formed in the vicinity of the imaging unit 200 is captured by the imaging unit 200 as an image signal. The imaging signal processing circuit 506 amplifies the image signal output from the imaging unit 200, converts the analog signal into a digital signal (A / D conversion), and converts the R, G, G, and B signals after A / D conversion. obtain. The imaging signal processing circuit 506 performs various corrections, compression of image data, and the like.

  The lens unit 501 is driven and controlled by a lens driving unit 502 such as zoom, focus, and diaphragm. The mechanical shutter 503 is a shutter mechanism having only a curtain corresponding to the rear curtain of a focal plane type shutter used in a single-lens reflex camera. The mechanical shutter 503 is driven and controlled by a shutter driving unit 504. The timing generation unit 507 outputs various timing signals to the imaging unit 200 and the imaging signal processing circuit 506. A control unit 509 performs control of the entire imaging system and various calculations. The memory unit 508 temporarily stores image data. The recording medium control interface unit 510 records image data on the recording medium 512 and reads or reads image data from the recording medium 512. The display unit 511 displays image data. The recording medium 512 is a detachable storage medium such as a semiconductor memory, and records image data. The external interface unit 513 is an interface for communicating with an external computer or the like. The photometry unit 514 detects the brightness information of the subject, and the distance measurement unit 515 detects the distance information to the subject. Reference numeral 516 denotes a white balance circuit (WB circuit). Note that the operation mode of the imaging system is set by the operation unit 517.

It is a schematic sectional drawing of the CMOS type image pick-up element based on suitable embodiment of this invention. It is a figure which shows the spectral transmittance of the optical waveguide of the image pick-up element provided with the reflection preventing layer of a different structure by the light-incidence surface and light-projection surface of an optical waveguide. It is a figure explaining the manufacturing method of the CMOS type image pick-up element which concerns on suitable embodiment of this invention. It is a figure explaining the manufacturing method of the CMOS type image pick-up element which concerns on suitable embodiment of this invention. It is a schematic sectional drawing of the CMOS type image pick-up element based on suitable 2nd Embodiment of this invention. It is a figure which shows the spectral transmittance of an optical waveguide in the image pick-up element provided with the reflection preventing layer of a different structure in the light-incidence surface and light-projection surface of an optical waveguide. 1 is a diagram showing an outline of an imaging system using a CMOS type imaging device according to a preferred embodiment of the present invention. It is a figure which shows the spectral characteristic of the light which injects into a photoelectric conversion part in the conventional image pick-up element which does not have an antireflection structure in the light-incidence surface and light-projection surface of an optical waveguide.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image pick-up element 11 Photoelectric conversion means 20, 23, 40 Antireflection layer 41 Optical waveguide 53 Micro lens

Claims (6)

A photoelectric conversion unit that converts light into signal charges and stores it; a microlens that collects light on the photoelectric conversion unit; and an imaging device that includes an optical waveguide between the microlens and the photoelectric conversion unit. ,
A plurality of antireflection layers having different configurations are disposed between the optical waveguide and the photoelectric conversion means.   The plurality of antireflection layers are constituted by three thin films of a first thin film, a second thin film, and a third thin film from the photoelectric conversion means side, and the second thin film includes a silicon nitride film. The imaging device according to claim 1.   The imaging device according to claim 2, wherein the silicon nitride film has the largest thickness among the three thin films. When the refractive index of the first thin film is n1, the refractive index of the second thin film is n2, and the refractive index of the third thin film is n3,
The refractive index of each thin film is
n2> n3 ≧ n1
The image pickup device according to claim 2 or 3, wherein: Optical system,
The imaging device according to any one of claims 1 to 4,
An imaging system comprising: Photoelectric conversion means for converting light into signal charges and storing; a microlens for condensing light on the photoelectric conversion means; and a method for manufacturing an imaging device having an optical waveguide between the microlens and the photoelectric conversion means Because
Forming a first thin film on the substrate;
Forming a second thin film on the first thin film;
Forming an interlayer insulating film on the second thin film;
Forming an opening for forming the optical waveguide in the interlayer insulating film;
Forming a third thin film on the opening of the interlayer insulating film;
Filling the opening with an optical waveguide material;
An image pickup device manufacturing method comprising:

Images