JP2012186396A - Solid state image pickup device and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid state image pickup device having a light waveguide in a laminate structure formed of a plurality of interlayer films, which can improve light collection efficiency.SOLUTION: A solid state image pickup device comprises: a light receiving part 1 formed on a substrate for performing photoelectric conversion; a laminate structure formed on the light receiving part 1 and formed of a plurality of films including wiring layers (first Cu wiring 9, second Cu wiring 12); a sidewall film 16 covering a sidewall of a waveguide hole 14a formed in the laminate structure at a position corresponding to the light receiving part 1; and a light waveguide 14 formed by embedding a light permeable material in a space surrounded by the sidewall film 16. A planar shape of the light waveguide 14 is, when viewed from a light incident direction, a forward tapered shape in such a manner that the size becomes smaller from an incident side face toward the light receiving part 1 side.

Description

  The present invention relates to a solid-state imaging device in which an optical waveguide is formed above a light-receiving portion formed on a semiconductor substrate, and a method for manufacturing the same.

  In recent years, with the progress of downsizing, higher resolution, and higher sensitivity of photographing apparatuses such as digital still cameras and digital movies, there has been an increasing demand for smaller chip sizes and more pixels for solid-state imaging devices. If the chip size is reduced without reducing the pixel size, the number of effective pixels is reduced and the resolution is lowered. Therefore, the miniaturization of the pixel size is accelerating year by year.

  However, when the pixel size is reduced, the area of a light receiving portion (photoelectric conversion element) typified by an on-chip lens or a photodiode is reduced, which causes a problem that the photosensitivity is lowered. Therefore, a solid-state imaging device using an optical waveguide structure has been proposed as a means for increasing the light collection efficiency. In the optical waveguide structure, an optical waveguide made of a light transmissive material is provided on a light receiving portion that receives light and performs photoelectric conversion, and an on-chip lens is further provided on the optical waveguide. The emitted light is efficiently incident on the light receiving unit. However, when the wiring approaches the light receiving portion in a planar manner due to pixel miniaturization, the aperture diameter of the optical waveguide is limited, and the light collection efficiency is reduced.

  Therefore, conventionally, a technique for improving the light collection efficiency using this optical waveguide structure has been proposed (Patent Document 1, etc.). Patent Document 1 discloses a configuration in which a forward tapered optical waveguide is formed in an interlayer film with a large aperture diameter and a smaller aperture diameter as it reaches the bottom as an improvement measure for reducing light collection efficiency. A cross-sectional view of this solid-state imaging device is shown in FIG. As shown in the figure, a solid-state imaging device having an optical waveguide structure includes a light receiving unit 101 composed of a photodiode or the like on the surface layer side of a substrate, and includes a gate insulating film 102, an element isolation insulating film 103, and a stopper SiN. An insulating film 105 is formed via a film (etching stopper film) 104. In this insulating film 105, a transfer gate 106 necessary for reading and transferring signal charges from the light receiving unit 101, a multilayer wiring 107, and a conductive plug 108 associated with these wirings 107 are embedded. Further, an optical waveguide 109 made of a light transmissive material is formed at a location corresponding to the light receiving portion 101 in the insulating film 105. Here, in the structure of the optical waveguide 109, in order to improve the light collection efficiency, the size of the planar shape of the optical waveguide viewed from the incident direction of light becomes smaller from the light incident side surface toward the light receiving unit side. Such a forward tapered shape. An on-chip lens 113 is provided on the upper surface side of the insulating film 105 via a passivation 110, a planarizing film 111, and a color filter 112.

JP 2004-221532 A

In order to improve the light collection efficiency, in the optical waveguide structure having a forward tapered shape, the opening (that is, the hole) for forming the optical waveguide is only processed in the insulating film 105 on the light receiving portion 101. It is realized by. Specifically, the forward taper shape of the optical waveguide structure can be realized relatively easily by performing etching using a gas having a strong deposition property such as C ₄ F ₈ gas. However, in general, a liner film made of a SiN film or the like is formed on the metal wiring film as an etching stopper film for forming a via in the wiring interlayer insulating film in order to improve the reliability of the metal multilayer wiring such as Cu. In order to form, it is difficult to form a tapered opening over multiple layers. In other words, in optical waveguide processing (that is, processing of holes for forming an optical waveguide), it is important to perform etching in consideration of the selection ratio between the wiring interlayer insulating film and the liner film. If a strong gas is used, the possibility of etch stop on the liner film is very high, and it becomes impossible to etch the interlayer insulating film for wiring under the liner film. Become. Even if the etch stop can be avoided, a step portion is formed in the wiring interlayer insulating film and the liner film due to the selection ratio, and this may cause irregular reflection of light. .

  Therefore, the present invention is a solid-state imaging device having an optical waveguide in a laminated structure composed of a plurality of interlayer films (for example, a wiring interlayer insulating film and a wiring metal diffusion prevention film), and improves the light collection efficiency. An object of the present invention is to provide a solid-state imaging device that can be used and a method for manufacturing the same.

  In order to achieve the above object, a solid-state imaging device according to an embodiment of the present invention includes a light receiving portion that performs photoelectric conversion formed on a substrate, and a stacked layer that is formed on the light receiving portion and includes a plurality of wiring layers. A structure, a first film covering a sidewall of a hole formed at a position corresponding to the light receiving portion in the stacked structure, and a light-transmitting material embedded in a space surrounded by the first film And the space has a forward tapered shape in which the diameter of the space viewed from the incident direction of light decreases from the upper side of the hole toward the bottom side of the hole, and the refractive index of the first film Is lower than the refractive index of the light transmissive material.

  Thus, the first film is formed in the hole in the stacked structure so as to cover the side wall, and the light-transmitting material is embedded in the space surrounded by the first film. Even if the step portion is formed, it is covered with the first film, so that irregular reflection of light by the step portion is avoided, and the light collection efficiency is improved.

  Therefore, according to the solid-state imaging device of the present invention, in a solid-state imaging device having a laminated structure including a plurality of wiring layers, a forward tapered optical waveguide structure can be easily formed, and the optical waveguide opening (hole Even when the wiring is in contact with the wiring due to the occurrence of alignment misalignment or the like, the side wall of the hole is covered with the first film, so the effect of light vignetting (decrease in the amount of incident light due to reflection of light on the wiring) is affected. Can be eliminated, and a high yield can be secured.

  Here, the first film may be a sidewall film that covers a side wall of the hole, and the light transmissive material may be an optical waveguide. The laminated structure may include an interlayer insulating film in which wiring is formed, and a wiring metal diffusion prevention film that covers the wiring and the interlayer insulating film.

  In addition, a part of the optical waveguide may be positioned closer to the light incident side than the wiring that protrudes the largest on the light receiving portion among the plurality of wirings. At this time, the sidewall film is exposed in the hole and covers the wiring, so that the stepped portion in the hole is covered with the sidewall film, and the occurrence of optical vignetting is prevented.

  Further, a thin film having a higher refractive index than that of the interlayer insulating film may be formed on the sidewall of the hole, and the sidewall film may cover the sidewall of the hole through the thin film. At this time, the refractive index of the light transmissive material is preferably lower than the refractive index of the thin film. Thereby, the light leaking to the side wall of the hole is reflected and returns to the optical waveguide, so that incident light is confined in the optical waveguide, and the light collection efficiency is further improved.

  The sidewall film may have a refractive index lower than the refractive index of the light transmissive material, and the sidewall film has a refractive index substantially the same as the refractive index of the interlayer insulating film. In addition, a lens that is formed above the optical waveguide and collects light on the optical waveguide may be provided. This is because the light collection efficiency is further improved by these configurations.

  In order to achieve the above object, a method for manufacturing a solid-state imaging device according to an aspect of the present invention includes a step of forming a light receiving portion on a substrate, and a laminated structure including a plurality of wiring layers on the light receiving portion. Forming a hole at a position corresponding to the light receiving portion in the laminated structure, forming a first film on the substrate in which the hole is formed, and performing etch back, Forming a forward tapered space surrounded by the first film that covers the side wall of the hole and has an opening diameter that decreases from the top side of the hole toward the bottom side of the hole; Embedding a conductive material.

  As a result, the first film is formed in the hole in the laminated structure so as to cover the side wall, and the forward taper shape decreases from the upper side of the hole surrounded by the first film toward the bottom side of the hole. Since the light-transmitting material is embedded in the space, the first film covers even if a step portion is formed on the side wall of the hole, so that irregular reflection of light by the step portion is avoided and light is condensed. Efficiency is improved. That is, according to the method for manufacturing a solid-state imaging device of the present invention, a forward-tapered condensing means (optical waveguide structure) can be easily formed in a solid-state imaging device having a laminated structure including a plurality of wiring layers. High yield can be secured.

  According to the solid-state imaging device of the present invention described above, a solid-state imaging device having an optical waveguide in a laminated structure composed of a plurality of interlayer films, which can improve the light collection efficiency, and a method for manufacturing the same Is provided.

  Therefore, the present invention has a very high practical value in the present day when photographing apparatuses such as digital still cameras and digital movies are widely used.

Plan sectional drawing explaining the solid-state imaging device concerning the 1st Embodiment of this invention 1 is a schematic cross-sectional view illustrating a solid-state imaging device according to a first embodiment of the present invention. Schematic cross-sectional view for explaining a method of manufacturing a solid-state imaging device according to the first embodiment of the present invention (part 1). Schematic cross-sectional view for explaining a method of manufacturing a solid-state imaging device according to the first embodiment of the present invention (No. 2) Schematic cross-sectional view for explaining the method of manufacturing the solid-state imaging device according to the first embodiment of the present invention (No. 3) Schematic cross-sectional view for explaining a method of manufacturing a solid-state imaging device according to the first embodiment of the present invention (No. 4) Schematic cross-sectional view for explaining the method of manufacturing the solid-state imaging device according to the first embodiment of the present invention (No. 5). FIG. 6 is a schematic cross-sectional view for explaining a method of manufacturing the solid-state imaging device according to the first embodiment of the present invention (No. 6). Schematic cross-sectional view for explaining the method of manufacturing the solid-state imaging device according to the first embodiment of the present invention (No. 7). FIG. 8 is a schematic cross-sectional view for explaining a method of manufacturing a solid-state imaging device according to the first embodiment of the present invention (No. 8). FIG. 9 is a schematic cross-sectional view (No. 9) for explaining the method of manufacturing the solid-state imaging device according to the first embodiment of the present invention. Schematic cross-sectional view for explaining a solid-state imaging device in which a sidewall shape according to a modification of the first embodiment of the present invention is changed (part 1) Schematic cross-sectional view for explaining a solid-state imaging device in which the sidewall shape according to another modification of the first embodiment of the present invention is changed (part 2) Schematic sectional view for explaining a method of manufacturing a solid-state imaging device according to the second embodiment of the present invention (No. 1) Schematic sectional view for explaining a method of manufacturing a solid-state imaging device according to the second embodiment of the present invention (No. 2) Schematic sectional view for explaining a method of manufacturing a solid-state imaging device according to the second embodiment of the present invention (No. 3) Schematic sectional view for explaining a method of manufacturing a solid-state imaging device according to the second embodiment of the present invention (Part 4). Schematic cross-sectional view for explaining a method of manufacturing a solid-state imaging device according to the second embodiment of the present invention (No. 5). Plan sectional drawing explaining the solid-state imaging device concerning the 2nd Embodiment of this invention Schematic sectional view for explaining a method of manufacturing a solid-state imaging device according to the third embodiment of the present invention (No. 1) Schematic sectional view for explaining a method of manufacturing a solid-state imaging device according to the third embodiment of the present invention (No. 2) Schematic sectional view for explaining a method of manufacturing a solid-state imaging device according to the third embodiment of the present invention (No. 3) Schematic sectional view for explaining a method of manufacturing a solid-state imaging device according to the third embodiment of the present invention (Part 4). Schematic sectional view for explaining a method of manufacturing a solid-state imaging device according to the third embodiment of the present invention (No. 5). External view of a camera equipped with a solid-state imaging device according to the present invention The block diagram which shows the structure of a camera provided with the solid-state imaging device which concerns on this invention Schematic sectional view for explaining a solid-state imaging device in the prior art

  Hereinafter, embodiments of a solid-state imaging device of the present invention will be described with reference to the drawings.

  First, the solid-state imaging device according to the first embodiment of the present invention will be described.

  FIG. 1 is a plan sectional view for explaining an example of a solid-state imaging device according to the present embodiment, taking a size of 1, 4 um cell in a CMOS structure as an example, and FIG. 2 is a schematic sectional view. Here, a schematic cross-sectional view taken along line X-X ′ shown in FIG. 1 corresponds to FIG. 2, and a schematic cross-sectional view taken along line X-X ′ in FIG. 2 corresponds to FIG. 1.

As shown in FIG. 2, the solid-state imaging device described here includes a gate insulating film 2 made of a SiO ₂ film, an element isolation insulating film 3 on a substrate 30 having a light receiving unit 1 made of a photodiode or the like. A gate electrode 4 made of a polysilicon film and an antireflection film 5 made of a SiN film necessary for reading and transferring signal charges from the light receiving portion 1 are formed in an interlayer insulating film 6 made of SiO ₂ . A stopper film 7 for forming a first Cu wiring (hereinafter referred to as “first Cu wiring forming stopper film 7”) made of a SiN film is formed on the upper surface side of the interlayer insulating film 6, and a _first film made of a SiO ₂ film is formed on the upper surface portion thereof. An interlayer insulating film 8 for 1Cu wiring is formed, and a first Cu wiring 9 is formed in the interlayer insulating film 8 for first Cu wiring. A first Cu diffusion prevention film 10 made of a SiN film and serving as a Cu diffusion prevention film for the first Cu wiring 9 is formed on the upper surface portion of the first Cu wiring interlayer insulating film 8, and an SiO ₂ film is formed on the upper surface portion thereof. A second Cu wiring interlayer insulating film 11 is formed, and a second Cu wiring 12 is formed in the second Cu wiring interlayer insulating film 11. A second Cu diffusion preventing film 13, which is a Cu diffusion preventing film for the second Cu wiring 12 made of a SiN film, is formed on the upper surface portion of the second Cu wiring interlayer insulating film 11.

Further, the interlayer insulating film 6, the first Cu wiring forming stopper film 7, the first Cu wiring interlayer insulating film 8, the second Cu wiring interlayer insulating film 11, the first Cu diffusion preventing film 10, and the second Cu diffusion preventing film 13 are formed. An optical waveguide 14 made of a light-transmitting material having an opening diameter on the light incident end side of about 1 μm is formed at a position corresponding to the light receiving unit 1 in the laminated structure. A passivation film 15 of about 50 to 100 nm made of a SiN film is formed on the outer periphery of the optical waveguide 14, and a SiO ₂ film of about 100 to 300 nm (more strictly speaking, the film thickness at the thickest part). Sidewall films 16 are formed. An on-chip lens 19 is formed on the upper surface portion of the optical waveguide 14 via a planarizing film 17 and a color filter 18. Here, the light transmissive material embedded in the optical waveguide 14 is a material having a higher refractive index than the first Cu wiring interlayer insulating film 8 (or the second Cu wiring interlayer insulating film 11). The sidewall film 16 is an example of a first film that covers the side wall of the waveguide hole 14a. Here, the sidewall film 16 is the same film as the first Cu wiring interlayer insulating film 8 (or the second Cu wiring interlayer insulating film 11). It is made of a material that has a refractive index close to that of the seed or that is (that is, substantially the same). That is, the refractive index of the sidewall film 16 is substantially the same as the refractive index of the interlayer insulating film and is lower than the refractive index of the light transmissive material embedded in the optical waveguide 14.

  The optical waveguide 14 is for guiding the light incident on the inside to the light receiving unit 1. In the present embodiment, the optical waveguide 14 is surrounded by the sidewall film 16 that covers the side wall of the waveguide hole 14a even in the solid-state imaging device including the laminated structure including the wiring interlayer insulating film and the Cu diffusion preventing film. Since the forward tapered shape is such that the aperture on the light receiving portion side is smaller than the aperture of the light incident end of the optical waveguide 14, the light collection efficiency can be improved and color mixing can be prevented. It becomes possible.

  That is, the solid-state imaging device according to the present embodiment is formed on the light receiving unit 1 that performs photoelectric conversion formed on the substrate 30 and the wiring layer (the first Cu wiring 9 and the second Cu) as the main parts. Laminated structure (interlayer insulating film 6, first Cu wiring forming stopper film 7, first Cu wiring interlayer insulating film 8, second Cu wiring interlayer insulating film 11, first Cu diffusion preventing layer including a plurality of films including wiring 12) Film 10, at least two layers of second Cu diffusion prevention film 13), sidewall film 16 covering the sidewall of waveguide hole 14 a formed at a position corresponding to light receiving portion 1 in the laminated structure, and sidewall film 16. And a light guide 14 formed by embedding a light-transmitting material in a space surrounded by a plane, and the size of the planar shape of the light guide 14 viewed from the light incident direction is received from the light incident side surface. To the part 1 side And it has a smaller forward tapered shape Te.

With such a structure, the solid-state imaging device according to the present embodiment is different from the conventional solid-state imaging device in which the laminated structure is simply opened to form the optical waveguide, and the waveguide hole 14a obtained by opening the laminated structure is formed. Since the optical waveguide 14 is formed by forming the sidewall film 16 so as to cover the side wall, the forward tapered optical waveguide 14 can be easily formed without forming a step portion that causes irregular reflection of light. It is formed. That is, by depositing a SiO ₂ film to be a sidewall film on the laminated structure in which the waveguide hole 14a is formed, the step portion in the waveguide hole 14a is covered, and then the SiO ₂ film is etched back. By doing so, it is possible to reduce the opening on the light receiving part side and increase the opening on the light incident side (a forward tapered shape).

  1 and 2 exemplify the case where there are two wiring layers (the first Cu wiring 9 and the second Cu wiring 12). However, even if there are three or more wiring layers, a sidewall film is formed as in this embodiment. Is possible. Moreover, you may use metals other than Cu as a metal for wiring. Furthermore, a film other than the SiN film such as a SiON film may be used as the Cu diffusion preventing film.

  Next, the manufacturing method of the solid-state imaging device according to the present embodiment will be described along the schematic cross-sectional views of FIGS.

First, as shown in FIG. 3, an element isolation insulating film 3 made of a light receiving portion 1 and a SiO ₂ film is formed on a substrate 30, and a gate insulating film 2 made of a SiO ₂ film and polysilicon are formed on the light receiving portion 1. A gate electrode 4 made of the above, an antireflection film 5 made of a SiN film, and an interlayer insulating film 6 are formed. Here, the antireflection film 5 is formed using a SiN film or the like used for an LDD (Lightly Doped Drain) structure formed so as to cover the side wall portion of the gate electrode 4. It is desired to be a refractive index material. If necessary, the thickness of the antireflection film 5 is adjusted to about 20 to 60 nm by performing etching only on the upper surface of the light receiving unit 1 in order to increase the light intensity.

Next, as shown in FIG. 4, on the interlayer insulating film 6 made of SiO ₂ or the like, a first Cu wiring forming stopper film 7 made of SiN film, the first Cu wiring interlayer insulating film 8 made of SiO _2, etc. A first Cu diffusion prevention film 10 made of 1Cu wiring 9, SiN or the like is formed, and a second Cu diffusion prevention film made of SiO ₂ or the like, a second Cu wiring interlayer insulation film 11 made of SiO ₂ or the like, and a second Cu diffusion prevention film made of SiN or the like. 13 is formed.

  Then, as shown in FIG. 5, in order to form a portion to be an optical waveguide using a normal lithography process, a resist 21 to be a mask is formed on the second Cu diffusion preventing film 13 with an opening size of about 1 μm. Pattern it like this. Here, the interlayer insulating film 6 in this example is 350 nm, and regarding the film thickness of the Cu wiring interlayer insulating film and the diffusion prevention film, the first Cu wiring forming stopper film 7 is 50 nm, and the first Cu wiring interlayer insulating film 8 is 80 nm. The first Cu diffusion preventing film 10 is 60 nm, the second Cu wiring interlayer insulating film 11 is 265 nm, and the second Cu diffusion preventing film 13 is 60 nm.

After the patterning of the resist 21, as shown in FIG. 6, dry etching is performed using the resist 21 as a mask to form the waveguide hole 14a. Dry etching for the waveguide opening (formation of the waveguide hole 14a) uses anisotropic etching conditions such as RIE (Reactive Ion Etching). Here, control of the selection ratio between the interlayer insulating film for wiring and the Cu diffusion prevention film is important, and when a gas having a strong deposition property typified by a C ₄ F ₈ system is used, the etching is stopped by the Cu diffusion prevention film. Very likely. Therefore, it is desirable to perform etching using a gas system such as CF ₄ or CHF ₃ . As an example of etching conditions, the pressure is about 5 Pascal (Pa), the gas system and flow rate are about CF ₄ (CHF ₃ ) / Ar / O ₂ = 50/1500/30 sccm, and the lower bias value is 2000 watts (W). Use the degree. Here, in terms of the selection ratio, the wiring interlayer insulating film has a shape that is about 10 nm to 30 nm backward from the exposure to the waveguide hole 14 a than the Cu diffusion preventing film.

  After the formation of the waveguide hole 14a, as shown in FIG. 7, the passivation film 15 is formed by a high-density plasma CVD method or the like so as to cover the inner wall including the bottom of the waveguide hole 14a and the upper surface of the second Cu diffusion prevention film 13. A film thickness of about 50 to 100 nm is formed. Here, the passivation film 15 is preferably made of an insulating material such as SiN having a higher refractive index than the interlayer insulating film for wiring so that the extinction coefficient of light is extremely small and light can be confined in the waveguide. . Thus, the passivation film 15 which is a thin film having a refractive index higher than that of the wiring interlayer insulating film is formed on the side wall of the waveguide hole 14a.

Then, as shown in FIG. 8, a SiO ₂ film 16a having a thickness of about 400 to 600 nm is formed on the passivation film 15 by a high density plasma CVD method or the like. As shown in FIG. 9, this SiO ₂ film 16a is formed. The sidewall film 16 is formed by etching back using the antireflection film 5 and the passivation film 15 as a stopper film. In this way, the side wall of the waveguide hole 14a formed at a position corresponding to the light receiving portion 1 in the laminated structure is covered (strictly speaking, it is guided through the passivation film 15 formed on the side wall of the waveguide hole 14a. A sidewall film 16 is formed so as to cover the sidewall of the waveguide hole 14a. As a result, even if the interlayer structure between the wiring interlayer insulating film and the diffusion prevention film has a step structure, the waveguide hole 14b has a forward tapered shape that decreases from the light incident side surface toward the light receiving unit side. Can be formed. Here, the thickness of the sidewall film 16 (more precisely, the thickness at the thickest portion) is about 200 nm, and the height of the sidewall film 16 is about 800 nm. The thickness and height of the sidewall film 16 can be easily adjusted by the etch back conditions and the etch back processing time. The sidewall film 16 is made of the same film type as the first Cu wiring interlayer insulating film 8 and the second Cu wiring interlayer insulating film 11, or a material having a refractive index close to (that is, substantially the same). It is desirable.

Next, as shown in FIG. 10, a light-transmitting material such as TiO _x is embedded in the waveguide hole 14 b by high-density plasma CVD, and then etched back or CMP (Chemical Mechanical Polishing: Chemical). The optical waveguide 14 is formed by promoting a flattening process by a mechanical mechanical polishing method. Here, the light transmissive material has a refractive index higher than that of the first Cu wiring interlayer insulating film 8 (second Cu wiring interlayer insulating film 11), and is formed on the side wall of the waveguide hole 14a. It is desirable that the refractive index be lower than that of the passivation film 15 which is a thin film.

  When a high refractive index material having a refractive index of about 1.9, such as a SiN film, is embedded as the light transmissive material, the first Cu wiring interlayer insulating film 8 (second Cu wiring use) even without the passivation film 15. Since the difference in refractive index between the interlayer insulating film 11) and the light transmissive material is large, light can be confined in the waveguide. That is, the sidewall film 16 may be formed so as to directly cover the side wall of the waveguide hole 14a formed at a position corresponding to the light receiving portion 1 in the laminated structure. Further, the refractive index of the sidewall film 16 is not necessarily the same as that of the interlayer insulating film if the refractive index of the light transmitting material to be used is sufficiently high. The material used as the sidewall film 16 has a refractive index of A material that is higher than the interlayer insulating film and lower than the light-transmitting material may be used.

  Thereafter, as shown in FIG. 11, the planarization film 17, the color filter 18, and the on-chip lens 19 are sequentially formed on the upper surface of the optical waveguide 14 by the same procedure as the manufacturing procedure of the conventional solid-state imaging device. Complete the device.

  In the solid-state imaging device according to the first embodiment, even if it is necessary to process a laminated structure of a wiring interlayer insulating film and a wiring metal diffusion prevention film in order to form the optical waveguide 14, By forming a sidewall film 16 on the side wall of the waveguide hole 14a and embedding a light transmitting material in a space surrounded by the sidewall film 16, it is possible to easily form the forward tapered optical waveguide 14. Thus, incident light can be efficiently guided to the light receiving unit 1 to improve the light collection efficiency and prevent color mixing.

  Here, as a modification of the first embodiment, the shape of the sidewall film 16 is not limited to that described in the present embodiment, and the height and film thickness can be freely changed according to the etch back conditions. Also good. A solid-state imaging device according to this modification is shown in FIGS. When the etch back processing time is increased, the height a of the sidewall film 16 shown in FIG. 11 is 2/3 to 4 minutes as shown by a ′ shown in FIG. It can be made to recede to about 3 heights. Here, it is desirable that the height of the sidewall film is closer to the opening side of the waveguide hole 14a than the position of the first Cu diffusion preventing film 10 which is the liner film immediately below the uppermost wiring. In addition, when the etch-back process is performed under the anisotropic etching conditions, the thickness b of the sidewall film 16 shown in FIG. 11 is indicated by b ′ shown in FIG. The film thickness can be set back to about one third to two thirds. In this way, by changing the sidewall shape, it is possible to form a tapered shape that provides an optimum light converging structure for the structure even if the shape of the on-chip lens and the depth of the waveguide are changed.

  Next, a second embodiment of the solid-state imaging device according to the present invention will be described. In the first embodiment, the metal wiring has a structure located outside the waveguide hole 14a. However, in the second embodiment, even if the wiring layer is exposed inside the waveguide hole, The wiring layer is completely covered with the wall film. The manufacturing method of this 2nd Embodiment is demonstrated using FIGS. Here, an SiN film having a high refractive index is used as the light transmissive material, and the formation method up to the wiring layer is the same as that in the first embodiment, and thus the description thereof is omitted.

  In FIG. 14, after the wiring layer is formed by the same manufacturing method as that shown in FIGS. 3 and 4 according to the first embodiment, the resist 21 serving as a mask has an opening size of about 1.1 μm. The figure which patterned is shown.

  Here, the opening size is equal to or larger than the distance between the wirings (first Cu wiring 9 in the present embodiment) that protrudes most inside the waveguide hole (distance A in FIG. 14) or about 100 nm.

Next, as shown in FIG. 15, waveguide processing is performed by the same method as in the first embodiment to form the waveguide hole 14a. Here, the first Cu wiring 9 has a structure protruding about 50 nm toward the waveguide hole 14a. Then, the SiO ₂ film 16a formed film thickness of about 400~600nm as shown in FIG. 16, as shown in FIG. 17, the SiO ₂ film 16a, the anti-reflection film 5 a second 2Cu diffusion preventing film 13 Stopper Etchback is performed as a film to form a sidewall film 16. By this sidewall film 16, the first Cu wiring 9 is completely covered. Next, as shown in FIG. 18, after filling a space surrounded by the sidewall film 16 with a SiN film as a light transmissive material, planarization is performed to form the optical waveguide 14. The manufacturing method of the process after this is the same as that of 1st Embodiment.

  As described above, in the second embodiment, a part of the optical waveguide 14 (here, the upper layer part than the first Cu wiring 9) is the wiring (here, the largest extension) on the light receiving unit 1 among the plurality of wirings. Then, it is positioned closer to the light incident side than the first Cu wiring 9). That is, the sidewall film 16 covers a part (exposed portion) of the wiring (here, the first Cu wiring 9) exposed in the waveguide hole 14a after the waveguide hole 14a is formed.

  According to the second embodiment, it is possible to make the opening diameter of the light incident side in the optical waveguide larger than that in the first embodiment, so that more light is confined in the optical waveguide and guided to the light receiving unit. Is possible. Furthermore, according to this embodiment, as shown in FIG. 19 which is a plan sectional view of FIG. 18, in the case of the same opening diameter as that of the first embodiment, the distance between wirings sandwiching the light receiving portion is reduced. Thus, the number of pixels per unit area can be increased. Further, in the first embodiment, even when the opening of the waveguide hole and the wiring are in contact with each other due to the occurrence of alignment misalignment or the like when the waveguide hole is opened (planar position overlapped), Depending on the form, the wiring layer can be covered with the sidewall film, and the influence of optical vignetting on the wiring and the deterioration of the wiring reliability can be prevented. Note that the modification of the first embodiment is also applicable to the second embodiment.

  Next, a third embodiment of the solid-state imaging device according to the present invention will be described. In the first and second embodiments, the waveguide processing is performed only by anisotropic etching. In the third embodiment, in order to further enlarge the opening of the waveguide hole, the second wiring interlayer insulation is used. Only the film is processed by isotropic etching. This embodiment will be described with reference to FIGS. Here, an SiN film having a high refractive index is used as the light transmissive material, and the formation method up to the wiring layer is the same as that in the first embodiment, and thus the description thereof is omitted.

First, after forming the wiring layer by a manufacturing method similar to that shown in FIGS. 3 and 4 according to the first embodiment, the resist 21 serving as a mask is patterned so that the opening size is about 1 μm. As shown in FIG. 20, the second Cu diffusion prevention film 13 and the second wiring interlayer insulating film 11 are processed by isotropic etching, and the diameter of the upper part of the opening is enlarged compared to anisotropic etching. To do. Here, the diameter of the upper part of the opening is about 1.2 μm. Next, as shown in FIG. 21, the interlayer film in the region where the waveguide is to be formed is processed to form the waveguide hole 14a. As a result, the opening diameter of the uppermost layer portion (region corresponding to the second Cu wiring) of the waveguide hole 14a is about 1.2 μm, the opening diameter of the bottom portion of the opening portion is about 1.0 μm, and the upper portion of the opening is enlarged. A structure of a waveguide hole can be formed. Next, an SiO ₂ film 16a is deposited as shown in FIG. 22, and as shown in FIG. 23, the sidewall film 16 is formed by etching back the SiO ₂ film 16a using the antireflection film 5 as a stopper film. Form. Then, as shown in FIG. 24, the opening diameter of the uppermost layer portion was expanded by embedding a SiN film as a light transmissive material in the space surrounded by the sidewall film 16 and then performing a planarization process. The optical waveguide 14 is formed. The manufacturing method of the process after this is the same as that of 1st Embodiment.

  In addition, the opening of the resist is enlarged or the etching amount of isotropic etching is increased to enlarge the opening formed in the second Cu wiring interlayer insulating film 11. It is good also as a structure which exposes a part of 1st Cu wiring in the said waveguide hole 14a after formation of the waveguide hole 14a.

  According to the third embodiment, it is possible to make the opening diameter of the light incident side in the optical waveguide larger than that of the first embodiment, and the amount of collected light increases due to the effective increase of the aperture ratio. Compared with the embodiment, an effective opening area of about 44% can be enlarged, and as a result, the photosensitivity can be increased.

  Note that the solid-state imaging devices in the first to third embodiments and the modification examples are applied to a digital still camera shown in FIG. 25A and a photographing device (camera) such as a digital movie shown in FIG. Needless to say, you can. FIG. 26 is a functional block diagram illustrating a configuration of a camera 210 including the solid-state imaging device 201 according to the present invention described in the first to third embodiments and modifications. The camera 210 includes a lens 200, a solid-state imaging device 201, a driving circuit 202, a signal processing unit 203, and an external interface unit 204. The light that has passed through the lens 200 enters the solid-state imaging device 201. The signal processing unit 203 drives the solid-state imaging device 201 via the drive circuit 202 and takes in an output signal from the solid-state imaging device 201. The output signal is subjected to various signal processing by the signal processing unit 203 and output to the outside via the external interface unit 204. Since such a camera 210 includes the solid-state imaging device 201 according to the present invention having a waveguide structure with improved light collection efficiency, the camera 210 is realized as a camera that is smaller, has higher resolution, and is more sensitive than before. obtain.

  As mentioned above, although the solid-state imaging device and the manufacturing method thereof according to the present invention have been described using the first to third embodiments and the modified examples, the present invention is not limited to these embodiments and modified examples. Absent. The present invention can be realized by arbitrarily combining the embodiments obtained by subjecting those embodiments and modifications to various modifications conceived by those skilled in the art and the constituent elements of each embodiment and modifications without departing from the spirit of the present invention. Forms are also included in the present invention.

  For example, in the embodiment of the present invention described above, the case where the present invention is applied to a CMOS type solid-state imaging device has been described. However, the present invention is not limited to this, and other types such as a CCD type are used. The present invention can also be applied to other solid-state imaging devices or devices other than solid-state imaging devices.

  Further, in the embodiments of the present invention, the present invention has been described with its preferred specific examples, but the present invention is not limited to the above-described embodiments. In particular, the optical waveguide shape and the multilayer wiring structure are only specific examples.

  The present invention is a solid-state imaging device, particularly a solid-state imaging device having a laminated structure composed of a plurality of films, which prevents color mixing and improves sensitivity by improving the condensing state of incident light to the light receiving unit. As a solid-state imaging device that can be improved, for example, it can be used as an image sensor for a photographing device (camera) such as a digital still camera or a digital movie.

DESCRIPTION OF SYMBOLS 1 Light-receiving part 2 Gate insulating film 3 Element isolation insulating film 4 Gate electrode 5 Antireflection film 6 Interlayer insulating film 7 Stopper film for 1st Cu wiring formation 8 Interlayer insulating film for 1st Cu wiring 9 1st Cu wiring 10 1st Cu diffusion prevention film 11 Interlayer insulating film for second Cu wiring 12 Second Cu wiring 13 Second Cu diffusion prevention film 14 Waveguide hole 14b immediately after formation of optical waveguide 14a Waveguide hole 15 after formation of sidewall film in waveguide hole 15 Passivation film 16 Sidewall film 16a SiO ₂ film 17 for forming waveguide inner side wall 17 Planarizing film 18 Color filter 19 On-chip lens 21 Resist 30 Substrate 200 Lens 201 Solid-state imaging device 202 Drive circuit 203 Signal processing unit 204 External interface unit 210 Camera

Claims (15)

A light receiving portion that performs photoelectric conversion formed on the substrate;
A laminated structure formed on the light receiving portion and including a plurality of wiring layers;
A first film covering a side wall of a hole formed at a position corresponding to the light receiving portion in the laminated structure;
A light transmissive material embedded in a space surrounded by the first film,
The space has a forward tapered shape in which the diameter of the space viewed from the incident direction of light decreases from the upper side of the hole toward the bottom side of the hole,
The refractive index of the first film is lower than the refractive index of the light transmissive material. The first film is a sidewall film covering a sidewall of the hole;
The solid-state imaging device according to claim 1, wherein the light transmissive material is an optical waveguide. The solid-state imaging device according to claim 2, wherein the multilayer structure includes an interlayer insulating film in which wiring is formed, and a wiring metal diffusion prevention film that covers the wiring and the interlayer insulating film. 4. The solid-state imaging device according to claim 3, wherein a part of the optical waveguide is positioned closer to a light incident side than a wiring that protrudes most greatly on the light receiving portion among the plurality of wirings. The solid-state imaging device according to claim 4, wherein the sidewall film covers the wiring exposed in the hole. On the side wall of the hole, a thin film having a higher refractive index than the interlayer insulating film is formed,
The solid-state imaging device according to claim 3, wherein the sidewall film covers a sidewall of the hole through the thin film. The solid-state imaging device according to claim 6, wherein a refractive index of the light transmissive material is lower than a refractive index of the thin film. The solid-state imaging device according to claim 2, wherein the sidewall film has a refractive index lower than a refractive index of the light transmissive material. The solid-state imaging device according to claim 8, wherein the sidewall film has a refractive index substantially the same as a refractive index of the interlayer insulating film. The solid-state imaging device according to claim 2, further comprising a lens that is formed above the optical waveguide and collects light on the optical waveguide. Forming a light receiving portion on the substrate;
Forming a laminated structure including a plurality of wiring layers on the light receiving portion;
Forming a hole at a position corresponding to the light receiving portion in the laminated structure;
The first film is formed on the substrate in which the hole is formed and etched back to cover the side wall of the hole, and the opening diameter decreases from the upper side of the hole toward the bottom side of the hole. Forming a forward tapered space surrounded by the first film;
And a step of embedding a light transmissive material in the space. In the step of forming the space, as the first film, a sidewall film that covers the sidewall of the hole is formed,
The method of manufacturing a solid-state imaging device according to claim 11, wherein in the step of embedding the light transmissive material, an optical waveguide is formed by embedding the light transmissive material. The solid-state imaging according to claim 12, wherein the step of forming the laminated structure includes a step of forming an interlayer insulating film in which wiring is formed, and a wiring metal diffusion prevention film covering the wiring and the interlayer insulating film. Device manufacturing method. In the step of forming the hole, the hole is formed so that the wiring is exposed to the hole,
The method of manufacturing a solid-state imaging device according to claim 13, wherein in the step of forming the forward tapered space, the space is formed so that the sidewall film covers the wiring. The method further includes a step of forming a thin film having a higher refractive index than the interlayer insulating film on a sidewall of the hole between the step of forming the hole and the step of forming the forward tapered space. 12. A method for producing a solid-state imaging device according to 12.

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