JP2014096476A - Solid-state imaging element, and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid generation of a void in a high refractive index material film in the opening part of a low refractive index material film, when forming a light pipe part by embedding the high refractive index material film in the opening part of the low refractive index material film, in a solid-state imaging element having a light pipe.SOLUTION: A solid-state imaging element 100 includes a light pipe part 100a provided in each of a plurality of light receiving parts for leading condensed light from a microlens to the light receiving parts. The light pipe part 100a has a light guide structure obtained by forming a plurality of light pipes Lp by embedding the high refractive index material film 28 in a plurality of opening parts 40b formed in a low refractive index material film 40, the opening width B of the individual opening part 40b of the low refractive index material film 40 is set to the opening width suitable for the film thickness of the high refractive index material film in accordance with the number of the opening parts on the individual light receiving part.

Description

  The present invention relates to a solid-state imaging device and a method for manufacturing the same, and in particular, a solid-state structure including an optical waveguide unit that guides image light from a subject to a light-receiving unit and dividing the optical waveguide unit into a plurality of optical waveguides (light pipes). Image sensor and manufacturing method thereof, and image input camera such as digital video camera and digital still camera such as digital video camera and digital still camera and surveillance camera using such solid-state image sensor as an image input device in an imaging unit, scanner device, and facsimile The present invention relates to electronic information equipment such as a device, a television telephone device, and a camera-equipped mobile phone device.

  Conventionally, CCD image sensors, CMOS image sensors, and the like are known as solid-state imaging devices that convert image light into electrical signals as image signals. For example, a CCD image sensor has a light receiving area for performing photoelectric conversion of image light and a transfer area for transferring signal charges obtained by photoelectric conversion, and these light receiving areas and transfer areas are provided on a common substrate. It has been. Here, in the light receiving region, a plurality of photodiodes as light receiving portions that generate charges by light irradiation are provided for each pixel, and in the transfer region, charges generated in each light receiving portion of the light receiving region are provided. The signal charges are read out from the pixel as a signal charge, and the horizontal transfer operation of the signal charge is performed after the vertical transfer operation of the read signal charge is performed. On the other hand, the CMOS type image sensor is configured to convert a signal charge generated in the light receiving portion of each pixel into a voltage signal in the pixel, and to read out the voltage signal for each pixel through a signal wiring.

  In such an image sensor, the area of the opening of the photodiode (that is, the opening of the light shielding film) is reduced with the recent reduction in pixels, and the amount of incident light to the opening is significantly reduced. Therefore, it is important to suppress degradation of image quality due to sensitivity reduction.

  Here, regarding the decrease in sensitivity, as a configuration for suppressing the decrease in sensitivity, there is an increasing number of optical waveguide portions (light pipe portions) provided on the opening of the photodiode. In general, the light pipe portion includes a high refractive index material film disposed on the photodiode portion (the portion where the photodiode on the substrate is disposed), and the high refractive index material film. A low refractive index material film provided around the refractive index material film, and the light is reflected in the high refractive index material film at the interface between the high refractive index material film and the low refractive index material film to the photodiode portion. It is configured to go forward.

  As described in Patent Document 1, as a method for manufacturing a light pipe portion, a hole is formed in a low refractive index material film formed on a photodiode portion, and a low refractive index material film is formed in the hole. A method of embedding a high refractive index material film having a high refractive index is also common.

  By the way, in a CCD type image sensor which requires a high number of pixels, a hole for embedding a high refractive index material film of a low refractive index material film located on the opening of the photodiode as the pixels become finer. However, in an image sensor that requires high sensitivity, it is necessary to increase the area of the photodiode, so the hole formed in the low refractive index material film that forms the light pipe The size of the can be rather large.

  When the high refractive index material film is embedded in the hole having a large size of the low refractive index material film constituting the light pipe portion as described above, in order to completely embed the hole portion, It is necessary to form a thick enough to be equivalent to the depth of, and when the high refractive index material film is formed thick so that the hole formed in the low refractive index material film is completely embedded, Voids (cavities) may be formed in the high refractive index material film depending on the difference between the film formation speed on the bottom surface side of the hole and the film formation speed on the surface side.

  FIG. 11 is a cross-sectional view showing a state in which a void is formed in the process of forming a light pipe portion that constitutes a pixel portion of a conventional solid-state imaging device, and FIG. 11A is a hole portion of a low refractive index material film. FIG. 11B shows a state in which a void is formed in the high refractive index material film embedded in FIG. 11B, and the shape of the hole of the low refractive index material film is formed on the low refractive index material film. The state which appeared as a recessed part (void) of the high-refractive-index material film | membrane which showed was shown.

  In the solid-state imaging device shown in FIG. 11A, a photodiode (PD) is formed as a light receiving portion 202 on the surface region of the semiconductor substrate 201, and light is received on the semiconductor substrate 201 via a gate insulating film 203. An element constituent member 204 such as a conductive layer as an electrode or wiring, a light-shielding film, and an insulating layer that insulates them is formed so as to surround the portion 202. The surface of the element constituent member 204 is covered with an insulating film 205 as a low refractive index material film, and a hole (opening) 205K of the insulating film 205 is located on the light receiving portion 202, The gate insulating film 203 is exposed on the bottom surface of the hole 205K. On the insulating film 205, a high refractive index material film 206 is formed thick so that the hole 205k is completely filled.

  In this solid-state imaging device, a cavity (void) 216a is formed in the high refractive index material film 206, and the film thickness of the high refractive index material film 206 is also thick, so that incident light is irregularly reflected by voids. Condensation efficiency decreases due to a large distance between the color filter or microlens on the high refractive index material film 216 and the light receiving portion.

  In addition, when a high refractive index material film is embedded in a hole having a large size of the low refractive index material film constituting the light pipe portion, the film thickness of the high refractive index material film is set to the depth of the hole of the low refractive index material film. If it is thinner than that, the step in the hole 205K of the low refractive index material film 205 is reflected in the high refractive index material film 206, and as shown in FIG. (Void) 216b is formed.

  For such a problem, the high refractive index material film 206 is thinly formed on the low refractive index material film 205 in which the hole 205K is formed so that the unevenness of the low refractive index material film 205 which is the base is reflected. A method of forming an optical waveguide by embedding and flattening a resin layer in the hole 216b of the high refractive index material film 206, which is equivalent to the hole 205K of the low refractive index material film 205, is formed after the formation. . In this method, it is not necessary to form the high refractive index material film 206 thick so as to completely fill the hole 205K of the low refractive index material film 205, and a cavity (void) 216a shown in FIG. 11A is formed. There is no fear, and since the resin is embedded in the recess 216b shown in FIG. 11B, the surface of the high refractive index material film becomes flat.

  However, in such a method of forming an optical waveguide portion, after forming a high refractive index material film on a low refractive index material film having a recess, the recess formed in the high refractive index material film is filled with a resin layer. A flattening step is required.

  Further, in this optical waveguide portion, a part of the light transmitted through the color filter formed thereon enters the high refractive index material film after passing through the resin layer. Light absorption occurs in the resin layer, and the light collection efficiency decreases.

  Therefore, Patent Document 2 discloses a technique in which a color filter is used as the resin layer to avoid the addition of a flattening step and a decrease in light collection efficiency.

  FIG. 12 is a cross-sectional view illustrating the structure and manufacturing process of the solid-state imaging device disclosed in Patent Document 2.

  A conventional solid-state imaging device 200 shown in FIG. 12 has a semiconductor substrate 201 such as a silicon substrate and image light from a subject on the semiconductor substrate 201, similarly to the structure of the pixel portion of the solid-state imaging device described in FIG. A light receiving portion (photoelectric conversion portion) 202 using a photodiode PD that performs photoelectric conversion, and a structure (element structure) formed on the semiconductor substrate 201 so as to be positioned around the light receiving portion 202 with a gate insulating film 203 interposed therebetween Member) 204.

  Here, an insulating film (low refractive index material film) 205 that functions as a clad layer and forms the optical waveguide 209 is formed on the structure 204 and the gate insulating film 203, and the surface of the insulating film 205 The hole 204 (opening) 205 </ b> K is formed by reflecting the level difference by the structure 204 positioned around the light receiving unit 202. Further, a high refractive index material film 206 is formed on the insulating film 205 so as to reflect the shape of the hole 205K, and the color filter 207 is formed on the high refractive index material film 206 with a high refractive index material. The film 206 is formed so as to fill the recess 206K. A micro lens 208 is formed on the color filter 207 so as to be positioned on the light receiving unit 202.

  In the solid-state imaging device 200 having such a structure, as shown in FIG. 12, the light collected by the microlens 208 is incident on the color filter 207, and the light transmitted therethrough is the color filter 207 and the high refractive index material. The light refracts at the interface with the film 206 and enters the high refractive index material film 206. The light that has entered the high refractive index material film 206 repeats total reflection at the interface between the insulating film 205 and the high refractive index material film 206 and at the interface between the high refractive index material film 206 and the color filter 207. The light propagates through the film 206 and enters the light receiving unit 202.

JP 2002-118245 A JP 2012-146797 A

  As described above, in a solid-state imaging device having an optical waveguide portion, when the high refractive index material film is embedded in a large-sized hole portion of the low refractive index material film constituting the optical waveguide portion, the hole portion is completely embedded. In order to achieve this, it is necessary to form a high refractive index material film thick enough to be equivalent to the depth of the hole, and to form a hole having a high refractive index material film formed in the low refractive index material film in this way. When it is formed thick so as to be completely embedded, voids (cavities) may be formed in the high refractive index material film due to the difference in film formation speed between the upper end side and the lower end side of the hole. In this case, the image quality is deteriorated because the light is irregularly reflected by the void (cavity) of the high refractive index material film and the distance from the color filter or microlens to the light receiving portion is increased. .

  In addition, when a high refractive index material film is embedded in a hole having a large size of the low refractive index material film constituting the optical waveguide portion, the film thickness of the high refractive index material film is set to the depth of the hole of the low refractive index material film. If the thickness is smaller, the shape of the hole (opening) 205K of the low refractive index material film is reflected in the high refractive index material film 206, and as shown in FIG. In addition, a recess 216b is formed, and a process of filling the recess 216b with a resin layer or the like is required.

  In order to reduce the embedding process using such a resin layer, the color filter 207 is formed on the high refractive index material film 206 constituting the optical waveguide section 209 as disclosed in Patent Document 2. If the film 206 is formed so as to fill the recess 206K (see FIG. 12), there arises a problem that the film thickness of the color filter 207 varies.

  That is, when the hole 205K of the insulating film 205 is formed on the light receiving portion 202 by patterning the insulating film 205 which is a clad layer (low refractive index material film) constituting the optical waveguide portion 209, the photolithography process is performed. The exposure amount and the etching amount in the etching process vary within the semiconductor chip constituting the solid-state imaging device, and due to such variation, the size of the hole 205K of the insulating film 205 varies between pixels.

  In this case, the width of the portion of the color filter 207 embedded in the hole 205K of the insulating film 205 via the high refractive index material film 206 varies among the pixels, whereby the color filter 207 has a light receiving portion on the light receiving portion. The height will vary between pixels.

  As described above, when variations occur in the width and height of the portion of the color filter embedded in the hole 205K of the insulating film 205 (that is, the hole 206K of the high refractive index material film), the sensitivity is a difference in sensitivity for each color. For example, the sensitivity output ratio of the blue pixel (BLUE pixel) to the green pixel (GREEN pixel) varies, and there is a problem that variation occurs in image adjustment by white balance.

  The present invention has been made to solve the above-described problems. When forming an optical waveguide by embedding a high refractive index material film in an opening of a low refractive index material film, the low refractive index material is provided. It is possible to avoid the generation of voids in the high refractive index material film in the opening of the film, thereby adding an additional flattening step for filling the voids in the high refractive index material film, It is not necessary to flatten the high refractive index material film with the constituent material of the color filter in the forming process, and in turn, it is a simple process without incurring variations in the sensitivity output ratio between pixels of different colors. A high-sensitivity solid-state imaging device with a wide light-receiving area capable of forming an optical waveguide portion, a method for manufacturing the same, and an electronic information device using such a high-sensitivity solid-state imaging device with a wide light-receiving area And

  A solid-state imaging device according to the present invention includes a semiconductor substrate, a plurality of light-receiving portions formed on the semiconductor substrate, and a microlens provided above the light-receiving portion and collecting incident light. A plurality of light guides provided in each of the plurality of light receiving parts, and provided with an optical waveguide part for guiding the condensed light from the microlens to the light receiving part. A light guide structure in which a plurality of optical waveguides are formed by embedding a high refractive index material film in the opening of each of the openings, and an opening width of each opening of the low refractive index material film is set on each light receiving portion. Depending on the number of the openings, the opening width is set to be suitable for the film thickness of the high refractive index material film, thereby achieving the above object.

  According to the present invention, in the solid-state imaging device, the high refractive index material film is a silicon nitride film formed by a low pressure CVD method, the low refractive index material film is a silicon oxide film, and the low refractive index material film The opening width of the opening is preferably not more than twice the film thickness of the high refractive index material film.

According to the present invention, in the solid-state imaging device, the high refractive index material film has a thickness in a range of 200 nm to 400 nm, and an opening of the low refractive index material film has an opening width in a range of 300 nm to 600 nm. The optical waveguides are arranged in a matrix on the light receiving section, and a separation distance between adjacent optical waveguides in the row direction or the column direction is C1, and the width of the light receiving section in the row direction or the column direction is A is the opening width in the row direction or the column direction of the opening, and B is the number of arrays in the row direction or the column direction of the optical waveguide from the optical waveguide positioned along the periphery of the light receiving portion. When the distance to the periphery of the light receiving unit is C2, the following formula (1)
A = n × B + (n−1) × C1 + 2 × C2 (1)
Is preferably established.

  According to the present invention, in the solid-state imaging device, the planar pattern of the light receiving portion is a rectangular shape, the opening pattern of the opening portion of the low refractive index material film is a square shape, and the long side of the light receiving portion is along the long side. The number of the optical waveguides arranged is such that the arrangement interval of the optical waveguides along the long side of the light receiving unit and the arrangement interval of the optical waveguides along the short side thereof are the same interval. It is preferable that the number is larger than the number of the optical waveguides arranged along the side.

  In the solid-state imaging device according to the present invention, the planar pattern of the light receiving unit is a rectangular shape, and the opening pattern of the opening of the low refractive index material film is similar to the planar pattern of the light receiving unit. The number of the optical waveguides arranged along the long side of the portion is equal to the arrangement interval of the optical waveguides along the long side of the light receiving unit and the arrangement interval of the optical waveguides along the short side thereof. Thus, it is preferable that the number of the optical waveguides arranged along the short side of the light receiving portion is the same.

  According to the present invention, in the solid-state imaging device, the distance between the optical waveguide located along the periphery on the light receiving unit and the periphery of the light receiving unit is smaller than the spacing between adjacent optical waveguides on the light receiving unit. preferable.

  In the solid-state imaging device according to the aspect of the invention, it is preferable that an interval between adjacent optical waveguides on the light receiving portion is wider than a minimum line width capable of exposing and developing the photoresist film by photolithography.

  In the solid-state imaging device according to the aspect of the invention, it is preferable that the three-dimensional shape of the optical waveguide has an inverted truncated cone shape or an inverted truncated cone shape whose upper surface is wider than the bottom surface.

  According to the present invention, in the solid-state imaging device, a surface of the high refractive index material film is covered with a passivation film, and an inner lens is formed on the passivation film so as to correspond to the light receiving portion. Is preferred.

  In the solid-state imaging device according to the aspect of the invention, it is preferable that a color filter is formed on the inner lens so as to face each of the plurality of light receiving portions via a planarizing film.

  A method for manufacturing a solid-state imaging device according to the present invention includes a semiconductor substrate, a plurality of light receiving portions formed on the semiconductor substrate, and a microlens provided above the light receiving portion and collecting incident light. A method of manufacturing a solid-state imaging device, comprising: forming an optical waveguide portion that guides condensed light from the microlens to the light receiving portion in each of the plurality of light receiving portions, and forming the optical waveguide portion Forming a low refractive index material film on the semiconductor substrate so as to cover the light receiving portion; and selectively etching the low refractive index material film to form a plurality of openings in the low refractive index material film. Forming a high-refractive-index material film on the low-refractive-index material film, and forming the high-refractive-index material film on the low-refractive-index material film. A step of forming the optical waveguide portion so as to be filled with a material film, and the optical waveguide portion includes the low refractive index material. A light guide structure in which a plurality of optical waveguides are formed by embedding the high-refractive-index material film in the openings, and the opening width of each opening of the low-refractive-index material film is set on each light-receiving part. The opening width suitable for the film thickness of the high-refractive index material film is set according to the number of the opening portions in FIG.

  In the method for manufacturing a solid-state imaging element according to the present invention, it is preferable that the opening width of the opening portion of the low refractive index material film is not more than twice the film thickness of the high refractive index material film.

  According to the present invention, in the solid-state imaging device manufacturing method, in the low refractive index material film forming step, a silicon oxide film doped with boron and phosphorus is formed as the low refractive index material film by a CVD method. In the step of etching the refractive index material film, the low refractive index material film is selectively etched by reactive ion etching using a photoresist film as a mask to have an opening width of 300 to 600 nm as the plurality of openings. An opening is positioned on the light receiving portion, and in the step of forming the high refractive index material film, a first silicon nitride film is formed as the high refractive index material film to a thickness of 200 nm to 400 nm by a low pressure CVD method, Preferably, the plurality of optical waveguides are formed by flattening the upper surface of the formed first silicon nitride film by etch back.

  According to the present invention, in the method for manufacturing a solid-state imaging device, after the first silicon nitride film is etched back, the second silicon nitride film is passivated on the first silicon nitride film by a plasma CVD method. A step of forming a film, a step of forming a third silicon nitride film on the second silicon nitride film by a plasma CVD method, and photolithography using a gray-tone mask on the third silicon nitride film It is preferable to include a step of forming a resist mask by processing, and etching back the resist mask and the third silicon nitride film to form an inner lens.

  An electronic information device according to the present invention is an electronic information device including an imaging unit that captures an image of a subject, and the imaging unit is the above-described solid-state imaging device according to the present invention, thereby achieving the above object. Is done.

  As described above, according to the present invention, when an optical waveguide is formed by embedding a high refractive index material film in the opening of the low refractive index material film, the high refractive index material film is formed in the opening of the low refractive index material film. It is possible to avoid the generation of voids in the interior, which makes it possible to add a separate flattening process for filling the voids in the high refractive index material film or to increase the color filter constituent material in the color filter forming process. It is not necessary to flatten the refractive index material film, and in turn, the light receiving portion can be formed in a simple process without causing variations in sensitivity output ratio between pixels of different colors. A high-sensitivity solid-state imaging device having a large area, a method for manufacturing the same, and an electronic information device using such a high-sensitivity solid-state imaging device having a large light receiving area can be realized.

FIG. 1 is a diagram for explaining a CCD image sensor as a solid-state imaging device according to Embodiment 1 of the present invention, and schematically shows the entire configuration thereof. FIG. 2 is a diagram for explaining in detail a part of the solid-state imaging device according to Embodiment 1 of the present invention, and FIG. 2A is a transfer electrode in a part (A part) of the CCD image sensor shown in FIG. 2B shows the positional relationship between the transfer wiring and the photodiode portion. FIG. 2B shows the cross-sectional structure of the B3-B3 line portion of FIG. Shown including light. FIG. 3 is a diagram for explaining the solid-state imaging device according to Embodiment 1 of the present invention. FIG. 3A shows the size of the main part in the cross-sectional structure equivalent to FIG. ) Shows an arrangement of a plurality of light pipes constituting the optical waveguide portion of the solid-state imaging device. 4 is a cross-sectional view illustrating the solid-state imaging device according to the first embodiment of the present invention. The cross-sectional structure taken along line B1-B1 in FIG. 2 (FIG. 4A) and the cross-sectional structure taken along line B2-B2 in FIG. (FIG. 4B) and a cross-sectional structure taken along line B3-B3 of FIG. 2 (FIG. 4C) are shown. FIG. 5 is a cross-sectional view for explaining a method of manufacturing a solid-state imaging device (CCD type image sensor) according to Embodiment 1 of the present invention. FIGS. 5 (a) to 5 (d) show formation of various diffusion regions. The steps from the step to the transfer electrode forming step are shown step by step. FIG. 6 is a cross-sectional view illustrating a method for manufacturing a solid-state imaging device (CCD type image sensor) according to Embodiment 1 of the present invention. FIG. 6 (a) shows a process for forming a light shielding film, and FIG. ) Shows the step of forming the surface high concentration layer of the light receiving portion. FIG. 7 is a cross-sectional view illustrating a method of manufacturing the solid-state imaging device (CCD type image sensor) according to Embodiment 1 of the present invention, and is an enlarged view showing the main part of FIG. 6B (FIG. 7A). )) And a state in which a low refractive index material film is formed on the light receiving portion (FIG. 7B). FIG. 8 is a cross-sectional view for explaining a method of manufacturing the solid-state imaging device (CCD type image sensor) according to Embodiment 1 of the present invention. FIG. 8A shows a low refractive index material film formed on the light receiving portion. FIG. 8B shows a state in which a high refractive index material film is formed. FIG. 9 is a cross-sectional view for explaining a manufacturing method of the solid-state imaging device (CCD type image sensor) according to the first embodiment of the present invention. FIG. 9A shows a passivation film and an inner lens on the high refractive index material film. FIG. 9B shows a state in which a color filter and a microlens are formed on the inner lens. FIG. 10 is a block diagram illustrating a schematic configuration example of an electronic information device using the solid-state imaging device of Embodiment 1 as an imaging unit as Embodiment 2 of the present invention. FIG. 11 is a diagram for explaining a problem in the conventional solid-state imaging device. FIG. 11A shows a state where voids are formed when the high refractive index material film is formed thick, and FIG. Shows a state in which voids are generated when the high refractive index material film is thinly formed. FIG. 12 is a cross-sectional view for explaining the structure and manufacturing process of the solid-state imaging device disclosed in Patent Document 2.

  First, the basic principle of the present invention will be described with reference to the drawings (FIGS. 1 to 3).

  The present invention provides a semiconductor substrate such as an n-type epitaxial substrate 2, a plurality of light receiving portions (photodiode PD) 101 formed on the semiconductor substrate, and collects incident light L provided above the light receiving portion. A solid-state imaging device having a microlens 52 that includes an optical waveguide unit 100a that is provided in each of the plurality of light receiving units and guides condensed light from the microlens to the light receiving unit. 100a has a light guide structure formed by embedding a high refractive index material film 28 in a plurality of openings 40b formed in the low refractive index material film 40 to form a plurality of optical waveguides (light pipes) Lp. The opening width B of each opening 40b of the low-refractive index material film 40 depends on the number of the openings on each light receiving portion (for example, the high-refractive-index material film having an opening width suitable for the film thickness of the high-refractive index material film) 2 times the film thickness T of the material film 28) It is essentially characterized in that it is.

  In the present invention having such a configuration, one optical waveguide unit 100 a provided on the light receiving unit 101 embeds the high refractive index material film 28 in a plurality of openings 40 b formed in the low refractive index material film 40. The opening width B of the opening 40b of the low refractive index material film 40 corresponding to one light pipe Lp is the short side direction of the light receiving portion 101. The width A1 or the width A2 in the long side direction is reduced by the number of openings. Accordingly, the opening width B of the opening 40b of the low refractive index material film 40 is adjusted so that the opening 40b of the low refractive index material film 40 is a constant film by adjusting the number of openings 40b corresponding to one light receiving portion. The optimum opening width filled with the high refractive index material film 28 having the thickness T can be obtained.

  In this way, by specifically setting the width and the number of the light pipes Lp in the optical waveguide unit 100a corresponding to one light receiving unit 101 (that is, the n-type charge storage region 4), specifically, a high refractive index material film The light pipe width (opening width of the opening portion of the low refractive index material film) corresponding to the film thickness of 28 is set, and the numerical aperture of the light pipe (opening of the low refractive index material film in one light receiving portion) corresponding to the photodiode area By setting the number of portions), the opening width B of the opening portion 40b of the low refractive index material film 40 is set to the area occupied by the light receiving portion 101 and the high refractive index material film formed on the low refractive index material film 40. Depending on the film thickness T, the opening 40 b can be set to an opening width that is completely filled with the high refractive index material film 28.

  As a result, when forming the optical waveguide by embedding the high refractive index material film in the opening of the low refractive index material film, voids are generated in the high refractive index material film in the opening of the low refractive index material film. It can be avoided.

  This eliminates the need for a separate flattening process for filling the voids of the high refractive index material film, or for flattening the high refractive index material film with the color filter constituent material in the color filter forming process. Therefore, it is possible to provide a high-sensitivity solid-state imaging device having a wide light receiving area that can form an optical waveguide portion with a simple process without causing variations in sensitivity output ratio among pixels of different colors. it can.

  As described above, the basic principle of the present invention is that the width of the light pipe is set according to the film thickness of the high refractive index material film in which the light pipe is embedded, and the numerical value of the light pipe is set according to the photodiode area. Forming a light pipe.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a diagram for explaining a CCD image sensor as a solid-state imaging device according to Embodiment 1 of the present invention, and schematically shows the overall configuration of the CCD image sensor. 2 is a diagram for explaining in detail a part of the solid-state imaging device according to the first embodiment of the present invention. FIG. 2A is a part (A part) of the CCD image sensor shown in FIG. The positional relationship between the transfer electrode and its transfer wiring and the photodiode portion is shown, and FIG. 2B shows the cross-sectional structure of the B3-B3 line portion of FIG. 3A shows a cross-sectional structure equivalent to that of FIG. 2B together with incident light, and FIG. 3B shows the arrangement of the light pipes on the light receiving portion of the solid-state imaging device. . 4 is a cross-sectional view illustrating the solid-state imaging device according to the first embodiment of the present invention. The cross-sectional structure taken along line B1-B1 in FIG. 2 (FIG. 4A) and the line B2-B2 in FIG. A cross-sectional structure (FIG. 4B) and a cross-sectional structure taken along line B3-B3 of FIG. 2 (FIG. 4C) are shown. In FIGS. 2A and 4, the components on the upper layer side of the light pipe are not shown, but in FIGS. 2B and 3A, the structure above the light receiving unit and the transfer electrode. Including.

  The solid-state imaging device 100 according to the first embodiment includes a plurality of sensor units (hereinafter referred to as light receiving units) 101 that are arranged in a matrix and generate signal charges by photoelectric conversion of image light (incident light) from a subject. A vertical charge transfer unit 110 that is provided for each column of the plurality of light receiving units 101 and reads the signal charges from the corresponding light receiving units 101 and transfers them in the vertical direction, and the signal charges transferred from the vertical charge transfer unit 110 A horizontal charge transfer unit (HCCD) 120 that transfers in the horizontal direction, and an output unit 130 that converts the signal charge transferred from the horizontal charge transfer unit 120 into a voltage signal, amplifies and outputs the voltage signal. Here, each light receiving unit 101 and a portion of the vertical charge transfer unit 110 facing the light receiving unit 101 constitute a pixel Px, and the light receiving unit 101 is configured by a photodiode PD.

In addition, a p ⁻ type well portion 3 is formed in an n type epitaxial substrate (semiconductor substrate) 2 made of, for example, silicon, which constitutes the solid-state imaging device 100. An n-type charge accumulation region 4 constituting the photodiode PD is formed in the p ⁻ type well portion 3, and a surface p ⁺ layer (surface high concentration region) is formed on the surface portion of the n-type charge conversion region 4. 4a is formed. Here, the n-type photoelectric conversion region 4 is a region for performing photoelectric conversion of incident light during light reception and accumulating signal charges generated by the photoelectric conversion. Further, the surface p ⁺ layer 4a increases the concentration of holes coupled with noise charges (electrons) that are thermally generated due to crystal defects or the like in the surface portion of the n-type charge accumulation region 4 constituting the light receiving portion 101. By reducing the life of the noise charge, the noise charge other than the signal charge is suppressed. Further, the photodiode PD constituting the light receiving portion 101 is formed so as to surround the periphery of the surface p ⁺ layer (surface high concentration region) 4a and has a surface p ⁻ layer (surface having a lower impurity concentration than the surface p ⁺ layer 4a). Low concentration region) 4b. A silicon oxide film (SiO ₂ film) 10 and a silicon nitride film (SiN film) 12 are sequentially stacked on the portion of the n-type epitaxial substrate 2 where the photodiode PD is formed. An antireflection film is configured.

The vertical charge transfer unit 110 includes an n-type transfer channel region 5 formed in the p ⁻ type well portion 3 of the n type epitaxial substrate 2 along the transfer direction, and a gate insulating film on the p ⁻ type well portion 3. A plurality of transfer electrodes 9 arranged along the n-type transfer channel region 5 with (thermal oxide film) 8 interposed therebetween. This transfer electrode 9 is a polysilicon electrode formed by depositing and patterning a polysilicon film, and its periphery is an insulating film formed simultaneously with the silicon oxide film 10 on the n-type charge storage region 4 constituting the light receiving portion. (Thermal oxide film) 8a is covered. Here, between the n-type transfer channel region 5 of the vertical charge transfer unit 110 and the n-type charge storage region 4 of the light receiving unit 101 on one side thereof, signal charges are transferred from the light receiving unit 101 on one side to the vertical charge. A p-type charge readout region 6 to be read out in the portion 110 is formed, and between the n-type transfer channel region 5 of the vertical charge transfer portion 110 and the n-type charge accumulation region 4 of the light receiving portion 101 on the other side, A p-type channel stop region 7 is formed to block the flow of signal charges between the vertical charge transfer unit and the other light receiving unit 101.

  Further, the plurality of transfer electrodes 9 arranged along the row direction orthogonal to the transfer direction are connected to one transfer wiring for each row. Specifically, in the solid-state imaging device 100, as shown in FIGS. 2 and 3A, the transfer wiring is a stacked layer including a first-layer transfer wiring 21 and a second-layer transfer wiring 22. The first-layer transfer wiring 21 and the second-layer transfer wiring 22 are insulating films on the plurality of transfer electrodes 9 arranged in a predetermined row (for example, odd rows). 31 is arranged so that the first-layer transfer wiring 21 is in contact with the transfer electrode 9 in a predetermined row, and is arranged along a row adjacent to the predetermined row (for example, an even row). The plurality of transfer electrodes 9 are connected to a wiring branch portion 22b extending from the wiring trunk portion 22a of the second-layer transfer wiring 22 in a predetermined row via a contact hole CH. Here, both the first-layer transfer wiring 21 and the second-layer transfer wiring 22 are tungsten wirings made of tungsten.

On the n-type epitaxial substrate 2, a light-shielding film 13 is formed so as to cover the region other than the light receiving portion so as to block light from entering the n-type epitaxial substrate 2. A light shielding film opening 13a is formed in a portion of the light receiving portion 101 facing the n-type charge accumulation region 4, and the surface p ⁺ layer 4a constituting the light receiving portion 101 has a light shielding film 13 having the light shielding film opening 13a. Is formed by ion implantation using a light shielding film, and is positioned in a self-aligned manner by a light shielding film opening 13a formed so as to correspond to each of the plurality of light receiving portions 101. Further, the light shielding film 13 and the second layer transfer wiring 22 are insulated by an insulating film 32, and the first layer transfer wiring 21 and a silicon nitride film (SiN on the surface of the n-type epitaxial substrate 2). An insulating film 30 is formed between the film 12.

  On the silicon nitride film 12 exposed in the light shielding film 13 and the light shielding film opening 13a, an optical waveguide section 100a that guides the light condensed by the microlens 52 (condensed light) to the light receiving section 101 is formed. The optical waveguide 100a has a light guide structure in which a plurality of openings 40a formed in the low refractive index material film 40 are embedded in the high refractive index material film 28. The opening width B of the opening portion 40b is set to an opening width corresponding to the film thickness T of the high refractive index material film 28 in which the opening portion 40b is filled with the high refractive index material film 28.

  Here, the high refractive index material film 28 is a silicon nitride film formed by a low pressure CVD method (LPCVD method), and the low refractive index material film 40 is a silicon oxide film formed by a CVD method. The width B of the opening 40b of the low refractive index material film 40 determined by the film thickness T of the material film 28 is, for example, twice the film thickness T of the high refractive index material film 28. However, the width B of the opening 40b of the low-refractive index material film 40 is not limited to twice the film thickness T of the high-refractive index material film 28; It may be less than double.

The high refractive index material film 28 has a film thickness in the range of 200 nm to 400 nm, the recess 40b of the low refractive index material film 40 has an opening width B in the range of 300 nm to 600 nm, and the light pipe portion Lp. Are arranged in a matrix on the n-type charge accumulation region 4 of the light receiving unit 101, and the separation distance C1 in the row direction or column direction of adjacent light pipe portions Lp is the row direction of the n-type charge accumulation region 4. Alternatively, when the width in the column direction is A, the opening width in the row direction or the column direction of the opening 40b is B, and the number of arrangement of the light pipe portions Lp in the row direction or the column direction is n, the following equation (1) and (2)
A = n × B + (n−1) × C1 + 2C2 (1)
C1> C2 (2)
It is set to satisfy.

  The planar pattern of the n-type charge accumulation region 4 of the light receiving unit 101 is rectangular, the opening pattern of the opening 40b of the low refractive index material film 40 is square, and the light along the long side of the light receiving unit 101 is light. The arrangement number of the pipe portions Lp is such that the arrangement interval of the light pipe portions Lp along the long side of the n-type charge storage region 4 of the light receiving portion is equal to the arrangement interval of the light pipe portions Lp along the short side. Thus, the number of the light pipe portions Lp along the short side of the n-type charge accumulation region 4 of the light receiving portion is larger.

  Further, the spacing C1 between the adjacent light pipes Lp on the n-type charge accumulation region 4 of the light receiving unit 101 is wider than the minimum line width at which the photoresist film can be exposed and developed by photolithography. The light pipe Lp has an inverted truncated pyramid shape whose upper surface is wider than the bottom surface. However, the three-dimensional shape of the light pipe portion Lp may be an inverted truncated cone shape.

  Further, as shown in FIG. 2B, a passivation film (SiN film) 50 is formed on the high refractive index material film 28, and an inner lens 51 is formed on the passivation film 50 with the n-type of each light receiving unit 101. It is arranged so as to face the charge storage region 4.

  On the inner lens 51, color filters 20a and 20b are arranged via a flattening film 41. On the color filters 20a and 20b, a microlens is formed on-chip as a microlens via a flattening film 42. A lens 52 is formed.

  Next, a method for manufacturing the solid-state image sensor of Embodiment 1 will be described.

  FIG. 5 is a longitudinal sectional view for explaining the manufacturing method of the CCD type image sensor as the manufacturing method of the solid-state imaging device according to the first embodiment of the present invention in the order of steps, and FIGS. 5A to 5D are various views. 3 schematically shows a main part structure (a cross-sectional structure taken along line B2-B2 in FIG. 2A) in a process from a diffusion region forming step to an antireflection film forming step.

First, the p ⁻ type well portion 3 is formed on the n type epitaxial substrate 2 by ion implantation of impurities. This ion implantation is performed, for example, using boron as an impurity and setting the impurity dose to 1 × 10 ¹¹ to 1 × 10 ¹² / cm ² . Further, an n-type charge storage region 4 constituting the light-receiving portion 101 is formed on the p ⁻ -type well portion 3 by ion implantation, and an n-type transfer channel region 5 constituting the vertical charge transfer portion 110, and this n-type transfer. A p-type channel stop region 7 located on one side of the channel region 5 and a p-type charge readout region 6 located on the other side of the n-type transfer channel region 5 are formed by ion implantation (FIG. 5A). These regions are formed by a general CCD type image sensor manufacturing process. Here, the ion implantation for forming the n-type charge accumulation region 4 uses, for example, arsenic as an impurity, and an ion dose amount of 1 × 10 ¹² to 1 × 10 ¹³ / cm ^{2 with} an ion implantation energy of 350 to 400 keV. Do as. The ion implantation for forming the n-type charge readout region 6 is performed, for example, using boron as an impurity and an ion dose of 1 × 10 ¹² to 1 × 10 ¹³ / cm ^{2 with} an ion implantation energy of 20 to 40 keV. Furthermore, the ion implantation for forming the p-type channel stop region 7 uses, for example, boron as an impurity and an ion dose amount of 1 × 10 ¹² to 1 × 10 ¹³ / cm ^{2 with} an ion implantation energy of 20 to 40 keV. Do. Furthermore, ion implantation for forming the n-type transfer channel region 5 uses, for example, arsenic as an impurity, and an ion dose amount of 1 × 10 ¹² to 1 × 10 ¹³ / cm ^{2 with} an ion implantation energy of 100 to 150 keV. Do.

  Next, after forming a gate insulating film 8 on the n-type epitaxial substrate 2 by thermal oxidation, a polysilicon layer is formed on the gate insulating film 8, and this polysilicon layer is patterned by a photolithography technique and an etching process. Thus, the transfer electrode 9 is formed on the n-type transfer channel region 5, the p-type charge readout region 6 and the p-type channel stop region 7. Subsequently, after removing the gate insulating film 8 on the n-type charge storage region 4, silicon oxide films 10 and 8a are formed by thermal oxidation so as to surround the n-type charge storage region 4 and the transfer electrode 9. The film thicknesses of the silicon oxide films 10 and 8a at this time can be set to, for example, 10 to 20 nm (FIG. 5B).

Next, a low concentration surface region (surface p ⁻ layer) 4 b is formed in a self-aligned manner with respect to the transfer electrode 9 by selective ion implantation immediately above the n-type charge accumulation region 4. In this ion implantation, the transfer electrode 9 is used as an ion implantation mask together with the patterned photoresist film. For example, boron is used as an impurity, ion implantation energy is set to 5 to 15 keV, and a dose amount is set to 1 × 10 ¹² to 1 × 10 ¹³ /. cm ² (FIG. 5C).

  Thereafter, a silicon nitride film 12 is selectively formed on the n-type charge storage region 4. At this time, LPCVD is used to grow the silicon nitride film, and the silicon nitride film 12 is substantially formed of an antireflection film by the silicon nitride film 12 and the silicon oxide film 10 therebelow. For example, it sets to 30-60 nm (FIG.5 (d)).

FIGS. 6A and 6B are diagrams for explaining the subsequent steps of the manufacturing method of the CCD type image sensor. FIGS. 6A and 6B are diagrams illustrating a process of forming a light shielding film and a high-concentration surface region (surface p ⁺ 3 schematically shows a main part structure (a cross-sectional structure taken along line B2-B2 of FIG. 2) in a step of forming a layer.

  Subsequently, a first-layer transfer wiring 21 extending over pixels in a predetermined row (for example, odd rows) in the plurality of pixels Px arranged in a matrix is formed so as to be in contact with the transfer electrodes 9 of these pixels. Further, an interlayer insulating film 31 is formed so as to cover the transfer wiring 21 (see FIGS. 2A and 4A). Next, a contact hole CH (FIG. 2A) is formed in a portion of the interlayer insulating film 31 located on the transfer electrode 9 of a pixel (an even row pixel) adjacent to a pixel in a predetermined row (for example, an odd row pixel). 4C), the second-layer transfer wiring 22 is formed on the first-layer transfer wiring 21 via the interlayer insulating film 31. Then, as shown in FIG. The second-layer transfer wiring 22 includes a wiring trunk portion 22a that extends in the horizontal direction and overlaps the first-layer transfer wiring 21, and a wiring branch portion 22b that extends in a vertical direction from the wiring trunk portion 22a. The wiring branch portion 22b is electrically connected to the transfer electrodes 9 of the pixels in even rows through the contact holes CH. Further, an interlayer insulating film 32 is formed so as to cover the second-layer tungsten wiring 22 (see FIGS. 2A and 4A).

  Thereafter, a tungsten light-shielding film 13 is formed on the entire surface so that the regions other than the portion corresponding to the n-type charge storage region 4 constituting the light-receiving portion 101 are shielded. That is, when the tungsten light shielding film 13 is formed, the light shielding film opening 13 a is provided in a portion corresponding to the n-type charge accumulation region 4. Since this tungsten light-shielding film 13 is used as an ion implantation mask in an ion implantation process in a later process, the film thickness of this tungsten light-shielding film 13 is, for example, 80 to The thickness is set to 120 nm (FIG. 6A).

Next, using the tungsten light-shielding film 13 as an ion implantation mask, ions are selectively implanted into the exposed portion of the tungsten light-shielding film 13 in the light-shielding film opening 13a in the n-type charge accumulation region 4 to form a high concentration surface region (surface). p ⁺ layer) 4a is formed. At this time, the ion implantation for forming the surface p ⁺ layer 4a is set so as to penetrate the silicon nitride film 12 and the silicon oxide film 10. Specifically, when boron is used as the implantation species, for example, the implantation energy can be set to ²⁰ to 40 keV, and the dose can be set to 1 × 10 ¹³ to 1 × 10 ¹⁴ / cm ² . Also, when BF ₂ is used as the implantation type, the implantation conditions can be set so as to obtain a desired profile as in the case of boron (FIG. 6B).

Here, illustrates a method of using as an ion implantation mask tungsten light shielding film 13 in order to form the high concentration surface region (p ⁺ surface layer) 4a, the high concentration surface region (p ⁺ surface layer) 4a, as shown in FIG. After the low concentration surface region (surface p ⁻ layer) 4b is formed in the step shown in FIG. 5C, the patterned photoresist film may be formed by ion implantation using an ion implantation mask.

  Subsequently, a process of forming an optical waveguide part (light pipe part) on the light receiving part will be described.

  7 and 8 are longitudinal sectional views for explaining the method of manufacturing the solid-state imaging device according to the first embodiment of the present invention. FIG. 7 (a), FIG. 7 (b), FIG. 8 (a), and FIG. (B) has shown typically the principal part structure in the process of forming a light pipe part (cross-sectional structure in the B2-B2 line | wire of Fig.2 (a)). FIG. 7A shows a state in which the ion implantation process of FIG. 6B is performed.

As shown in FIG. 6B, after the high concentration surface region (surface p ⁺ layer) 4a is formed using the light shielding film 13 as an ion implantation mask (FIG. 7A), the light shielding film 13 and the light shielding film opening 13a ( An insulating film, for example, BPSG (Boron Phosphorus Silicon Glass) is deposited by a CVD method so as to cover the light receiving portion), and further planarized by a thermal reflow process. As a result, a BPSG film 40c is formed as a low refractive index material film (FIG. 7B).

  Next, after forming an etching mask (not shown) on the BPSG film 40c by photolithography, the BPSG film 40c is subjected to an etching process by RIE (Reactive Ion Etching), so that the inside of the opening of the light shielding film of the BPSG film 40c. The BPSG film 40 having a plurality of openings (openings of the low refractive index material film) 40b is formed (FIG. 8A). At this time, a condition for stopping the etching on the silicon nitride film 12 exposed in the light shielding film opening is selected as a condition for the etching process.

  Further, the opening width B of the opening 40b of the BPSG film 40 is high so that no voids are generated in the high refractive index material film when the opening 40b of the BPSG film 40 is buried with the high refractive index material film. The width needs to be in accordance with the refractive index material film thickness T.

  For example, when a silicon nitride film is formed as the high refractive index material film 28 by the low pressure CVD method (LP-CVD method), the film thickness T is set to 200 to 400 nm, and the opening width B is set to about 300 to 600 nm. be able to. The number of openings (number of openings arranged) is determined by the ratio of setting the opening width B and the widths C1 and C2 of the portion 40a where the opening is not set with respect to the width A of the n-type charge storage region 4 of the light receiving portion 101. Therefore, for example, the photodiode portion width (width in the short side direction of the light receiving portion) A1 is set to 1600 nm, the opening width B is set to 300 nm, and the opening separation distance C1 is set to 200 nm. When the distance C2 to the side of the charge storage region 4 is 150, A1 = 3B + 2C1 + 2C2 (the above formula (1)) is established, and the number of openings (the number of light pipes in the short side direction of the light receiving unit) is 3. Can be set. In addition, when a remainder arises with the said calculation formula, it can set so that a remainder may become zero by adjusting the width | variety C2. However, it is desirable to satisfy the relationship of C1> C2. The above formula (1) is also established for the width A2 in the long side direction of the light receiving unit, and for example, the number of openings (the number of light pipes in the short side direction of the light receiving unit) can be set to 4. (See FIG. 3B).

  Next, a silicon nitride film (high refractive index material film) 28 is formed by LP-CVD so that the opening 40b is embedded on the BPSG film (low refractive index material film) 40, and the upper surface thereof is flattened. As described above, the silicon nitride film is etched back to form a plurality of light pipe portions Lp (FIG. 8B). In the LP-CVD method (low pressure CVD method), a silicon nitride film can be formed with a uniform thickness on the exposed surface of the base.

  At this time, the silicon nitride film 28 buried in the opening 40b of the BPSG film is a film having a higher refractive index than that of the BPSG film 40, that is, the refractive index of the silicon nitride film as the high refractive index material film 28 is n = 2. The refractive index of the BPSG film as the low refractive index material film 40 is n = 1.4 to 1.5.

  Accordingly, the plurality of openings 40 b of the BPSG film in which the silicon nitride film 28 is embedded functions as a light pipe Lp that guides the condensed light collected by the microlens 52 to the light receiving unit 101.

  FIG. 9 is a diagram for explaining a method of manufacturing a solid-state imaging device according to Embodiment 1 of the present invention. FIG. 9A shows a state in which a passivation film and an inner lens are formed on a high refractive index material film. FIG. 9B shows a state in which a color filter and a microlens are formed on the inner lens.

  Next, for example, a plasma silicon nitride film is formed to a thickness of 300 nm as the passivation film 50 so as to cover the plurality of light pipes Lp on the high refractive index material film 28, and a light shielding film opening (light receiving part) is formed on the passivation film 50. The inner lens 51 is formed so as to overlap.

  Specifically, after forming a resist film on the plasma silicon nitride film that is the material of the inner lens 51, the resist film is exposed and developed using a gray tone mask (not shown) to have a lens shape. After forming the resist mask, the plasma silicon nitride film is etched together with this resist mask by an etch back method to form the inner lens 51 (FIG. 9A).

  For the structure above the inner lens, a color filter and an on-chip lens are formed by a general manufacturing method.

  That is, after the planarization film 41 is formed on the inner lens 51, the color filters 20a and 20b are formed. Further, after the planarization film 42 is formed on the color filters 20a and 20b, an on-chip lens 52 as a microlens is formed so as to be positioned on the light shielding film opening. Thereby, a CCD type image sensor is completed (FIG. 9B).

  Hereinafter, the effect of this embodiment is demonstrated.

  In the solid-state imaging device 100 according to the first embodiment, for example, according to the film thickness T of the high refractive index material film embedded in the opening 40 b of the low refractive index material film 40, the opening 40 b of the low refractive index material film 40 is formed. Since the opening width B is set to an opening width where no void is formed (for example, 2T in the first embodiment), the number of light pipe openings (the number of light pipes) corresponding to the photodiode area (area occupied by the light receiving unit) is set. By doing so, a boyless light pipe can be formed, and as a result, the light collection efficiency of a solid-state imaging device having a large-area photodiode can be improved.

  Further, in the present embodiment, the distance C2 from the light pipe positioned along the periphery of the light receiving unit 101 to the periphery of the light receiving unit is made smaller than the separation distance C1 in the row direction or column direction of the adjacent light pipe Lp. The collected light from the inner lens 51 incident on the peripheral edge of the light receiving portion 101 can be efficiently taken into the light receiving portion 101 by the light pipe Lp arranged to the vicinity of the light receiving portion periphery.

  Furthermore, the following effects are obtained in the first embodiment.

In the present embodiment, the surface p ⁺ layer (surface high concentration region) 4a constituting the photodiode PD which is the light receiving portion 101 is used as a mask with the light shielding film 13 formed with the light shielding film openings 13a corresponding to the respective light receiving portions. Since the surface is formed in a self-aligned manner with respect to the light shielding film opening 13a by ion implantation, the surface p ⁺ layer 4a constituting the light receiving portion 101 is positioned inside the n-type charge accumulation region 4 constituting the light receiving portion. . In other words, the p ⁺ surface layer 4a is the p ⁺ surface layer 4a as compared with the case of arranging a self-aligned manner with respect to the transfer electrodes, a distance and a light shielding film 13 and the n-type charge accumulation region 4 overlaps the p-type charge It will be located away from the reading area 6.

As a result, for example, even if the position of the light-shielding film opening 13a is slightly deviated due to process variation (mask alignment error, etc.), the positional deviation of the surface p ⁺ layer 4a is a point away from the p-type charge readout region 6. Positional variations occur, and this positional shift has a small effect on the concentration variations in the region between the p-type charge readout region 6 and the surface p ⁺ layer 4a.

Further, in this embodiment, the surface p constituting the light receiving section ^- a layer (surface low concentration region) 4b, a self-alignment manner is formed by ion implantation using as a mask the transfer electrodes 9, the surface p ^- layer (surface low concentration Since the region 4b surrounds the surface p ⁺ layer (surface high concentration region) 4a, the surface of the opposite conductivity type to the n-type charge accumulation region 4 constituting the light receiving portion is located near the p-type charge readout region 6. The p-type impurity concentration in the region can be reduced, thereby reducing the dark current due to the surface state and suppressing the increase in the depletion voltage with respect to the p-type charge readout region 6, and from the light receiving unit to the n-type charge transfer channel It is possible to prevent the reading of the signal charge to the region 5 from being hindered.

Further, the position of the surface p ⁻ layer (surface low concentration region) 4b is fluctuated nearer to the p-type charge reading region 6 than the surface p ⁺ layer 4a when the transfer electrode 9 is displaced due to process variations. Since the surface p ⁻ layer 4b has a lower impurity concentration than the surface p ⁺ layer 4a, the influence of the positional shift of the surface p ⁻ layer 4b is caused between the p type charge readout region 6 and the surface p ⁺ type region 4a. The influence on the concentration fluctuation in the region is small. Therefore, even if the surface p ⁻ layer 4 b is displaced, the concentration in the p type charge reading region 6 is increased unlike the case where the surface p ⁺ layer 4 a is moved in the vicinity of the p type charge reading region 6. The increase in after-image components accompanying darkening or the increase in dark white scratches due to the surface level accompanying the decrease in density in the surface region of the n-type charge accumulation region 4 can be kept low.

  In the first embodiment, the planar pattern of the light receiving portion is rectangular, the opening pattern of the opening of the low refractive index material film is square, and the number of light pipes arranged along the long side of the light receiving portion. Are arranged along the short side of the light receiving unit so that the arrangement interval of the light pipes along the long side of the light receiving unit and the arrangement interval of the light pipes along the short side thereof are the same interval. Although the number of light pipes is larger than the number of light pipes, the planar pattern of the light receiving part is rectangular, the opening pattern of the opening of the low refractive index material film is similar to the planar pattern of the light receiving part, The number of light pipes arranged along the long side of the light receiving portion is such that the light pipe arranging interval along the long side of the light receiving unit is the same as the light pipe arranging interval along the short side. Along the short side of the light receiving part It may be disposed number and the same number of the light pipe.

  In the first embodiment, the CCD image sensor is described as the solid-state image sensor. However, the solid-state image sensor may be a CMOS image sensor.

  Furthermore, although not specifically described in the first embodiment, a digital camera such as a digital video camera or a digital still camera, an image input camera, a scanner, or the like using the solid-state imaging device of the first embodiment as an imaging unit. An electronic information device having an image input device such as a facsimile or a camera-equipped cellular phone will be briefly described below.

(Embodiment 2)
FIG. 10 is a block diagram illustrating a schematic configuration example of an electronic information device using the solid-state imaging device of Embodiment 1 as an imaging unit as Embodiment 2 of the present invention.

  The electronic information device 90 according to the second embodiment of the present invention shown in FIG. 10 includes the solid-state imaging device 100 according to the first embodiment of the present invention as the imaging unit 91 that captures an image of a subject. A memory unit 92 such as a recording medium for recording data after high-definition image data obtained by photographing by the unit is subjected to predetermined signal processing for recording, and a liquid crystal display screen after the predetermined signal processing for display of the image data A display unit 93 such as a liquid crystal display device that displays on a display screen such as, a communication unit 94 such as a transmission / reception device that performs communication processing after this image data is subjected to predetermined signal processing for communication, and prints this image data ( And an image output unit 95 that outputs (prints out).

  As mentioned above, although this invention has been illustrated using preferable embodiment of this invention, this invention should not be limited and limited to this embodiment. It is understood that the scope of the present invention should be construed only by the claims. It is understood that those skilled in the art can implement an equivalent range based on the description of the present invention and the common general technical knowledge from the description of specific preferred embodiments of the present invention. Patents, patent applications, and documents cited herein should be incorporated by reference in their entirety, as if the contents themselves were specifically described herein. Understood.

  In the field of a solid-state imaging device and a method for manufacturing the same, the present invention provides a high refractive index material film embedded in an opening of a low refractive index material film to form an optical waveguide. It is possible to avoid the generation of voids in the refractive index material film. This makes it possible to add a separate flattening process for filling the voids in the high refractive index material film, or in the color filter forming process. There is no need to flatten the high refractive index material film by the constituent material, and in turn, the optical waveguide section is formed by a simple process without incurring variations in the sensitivity output ratio between pixels of different colors. It is possible to realize a high-sensitivity solid-state imaging device having a wide light-receiving area and a manufacturing method thereof, and an electronic information device using such a high-sensitivity solid-state imaging device having a wide light-receiving area.

2 N-type epitaxial substrate (semiconductor substrate)
3 p ⁻ type well portion 4 n ⁻ type charge storage region 4 a surface p ⁺ layer (high concentration surface region)
4b surface p ^- layer (low concentration surface region)
5 n-type transfer channel region 6 p-type charge readout region 7 p-type channel stop region 8 gate insulating film 9 transfer electrode 8a, 10 silicon oxide film 12 silicon nitride film 13 tungsten light shielding film 13a light shielding film opening 20a, 20b color filter 21 first First layer transfer wiring 22 Second layer transfer wiring 22a Wiring trunk 22b Wiring branch 28 High refractive index material film (SiN film)
30 Insulating film 31, 32 Interlayer insulating film 40 Low refractive index material film (SiO film)
40a Light pipe separation wall 40b Opening of low refractive index material film 40c BPSG film 41, 42 Flattening film 51 Inner lens 52 On-chip lens (microlens)
DESCRIPTION OF SYMBOLS 90 Electronic information equipment 91 Imaging part 92 Memory part 93 Display part 94 Communication part 95 Image output part 100 Solid-state image sensor 100a Optical waveguide part 101 Light receiving part 110 Vertical charge transfer part 120 Horizontal charge transfer part (HCCD)
130 Output part CH Contact hole L Incident light Lp Light pipe (optical waveguide)
PD photodiode Px pixel

Claims (5)

A solid-state imaging device having a semiconductor substrate, a plurality of light receiving portions formed on the semiconductor substrate, and a microlens provided above the light receiving portion for collecting incident light,
An optical waveguide provided in each of the plurality of light receiving units, for guiding the condensed light from the microlens to the light receiving unit;
The optical waveguide section has a light guide structure in which a plurality of optical waveguides are formed by embedding a high refractive index material film in a plurality of openings formed in the low refractive index material film. A solid-state imaging device in which the opening width of each opening is set to an opening width suitable for the film thickness of the high refractive index material film, depending on the number of the openings on each light receiving portion. The high refractive index material film is a silicon nitride film formed by a low pressure CVD method,
The low refractive index material film is a silicon oxide film,
2. The solid-state imaging device according to claim 1, wherein the opening width of the opening of the low refractive index material film is not more than twice the film thickness of the high refractive index material film. The high refractive index material film has a thickness in the range of 200 nm to 400 nm,
The opening of the low refractive index material film has an opening width in the range of 300 nm to 600 nm,
The optical waveguides are arranged in a matrix on the light receiving unit,
The separation distance between adjacent optical waveguides in the row direction or the column direction is C1, the width of the light receiving portion in the row direction or the column direction is A, the opening width of the opening in the row direction or the column direction is B, and the optical waveguide When the number of waveguides arranged in the row or column direction is n, and the distance from the optical waveguide located along the periphery of the light receiving portion to the periphery of the light receiving portion is C2, the following equation (1)
A = n × B + (n−1) × C1 + 2 × C2 (1)
The solid-state imaging device according to claim 1, wherein:   4. The solid-state imaging device according to claim 1, wherein the three-dimensional shape of the optical waveguide has an inverted truncated pyramid shape or an inverted truncated cone shape whose upper surface is wider than the bottom surface. 5. A method of manufacturing a solid-state imaging device having a semiconductor substrate, a plurality of light-receiving portions formed on the semiconductor substrate, and a microlens provided above the light-receiving portion and collecting incident light,
Forming each of the plurality of light receiving portions with an optical waveguide portion that guides the condensed light from the microlens to the light receiving portion;
The optical waveguide forming step includes:
Forming a low refractive index material film on the semiconductor substrate so as to cover the light receiving portion;
Selectively etching the low refractive index material film to form a plurality of openings in the low refractive index material film so that two or more openings are positioned on one light receiving portion;
Forming a high refractive index material film on the low refractive index material film so that an opening of the low refractive index material film is filled with the high refractive index material film,
The optical waveguide section has a light guide structure formed by embedding the high refractive index material film in an opening of the low refractive index material film to form a plurality of optical waveguides, and each of the low refractive index material films A method for manufacturing a solid-state imaging device, wherein the opening width of the opening is set to an opening width suitable for the film thickness of the high refractive index material film, depending on the number of the openings on each light receiving portion.

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