JP5396493B2 - Solid-state imaging device and manufacturing method thereof - Google Patents

Description

  The present invention relates to a solid-state imaging device and a manufacturing method thereof, and more particularly, to a solid-state imaging device including an optical waveguide and a manufacturing method thereof.

  In recent years, with the miniaturization of solid-state imaging devices, it has been required to increase the sensitivity while miniaturizing and increasing the density of pixels and reducing the light receiving area. In order to achieve both reduction of the light receiving area and high sensitivity, various structures for making light incident on the light receiving element more efficiently have been studied. For example, an on-chip lens is provided on the color filter to efficiently collect light on the light receiving element, or an optical waveguide is provided on the light receiving element to efficiently guide incident light to the light receiving element.

  An optical waveguide for guiding incident light to the light receiving element can be formed by providing a recess in an interlayer insulating film formed on the light receiving element and filling the recess with a material having a higher refractive index than the interlayer insulating film. . However, due to the reduction of the light receiving region, the aspect ratio of the recess for forming the optical waveguide is increased. If an attempt is made to form a film using a raw material in a gas phase state in a concave portion having a high aspect ratio, the raw material is not sufficiently supplied into the concave portion, and a void may be formed.

  As a method of forming an optical waveguide in a recess having a high aspect ratio, a method of embedding a resin that can be formed by coating into the recess is known (see, for example, Patent Document 1).

JP 2010-283145 A

  However, when the resin is embedded in the recess, there is a problem that the light collecting property of the optical waveguide cannot be sufficiently increased.

  The higher the refractive index of the material embedded in the recess, the better the light collecting property of the optical waveguide. However, in the case of a resin material that can be formed by coating, the refractive index cannot be made sufficiently high. For example, the refractive index of silicon nitride is about 1.9, whereas the refractive index of titanium-containing siloxane polymer is only about 1.7. For this reason, in the conventional method, it is difficult to form an optical waveguide having a high light collecting property.

  An object of the present invention is to solve the above-described problems and to easily realize a solid-state imaging device including an optical waveguide having a high light collecting property embedded with a material having a high refractive index.

  In order to achieve the above object, the present invention comprises an optical waveguide comprising a laminated film of a first film and a second film in which a solid-state imaging device is embedded in a recess, and the first film has a thickness of the recess. The upper part is thinner than the lower part.

  Specifically, a first solid-state imaging device according to the present invention includes a light receiving unit formed on a semiconductor substrate and a first insulating layer formed on the semiconductor substrate, including an interlayer insulating film, at a position corresponding to the light receiving unit. And an optical waveguide formed in the first recess and guiding light to the light receiving portion. The optical waveguide includes a first film and a second film sequentially formed from the insulating film stack side. The refractive index of each of the first film and the second film is higher than the refractive index of the interlayer insulating film. The first film covers the side surface and the bottom surface of the first recess, and the first film A portion having a second recess at a position corresponding to the recess, the second film being formed so as to be embedded in the second recess, and a portion formed on the side surface of the first recess in the first film Is thinner at the top of the first recess than at the bottom.

  In the solid-state imaging device of the present invention, the optical waveguide has the first film and the second film, and the film thickness of the portion formed on the side surface of the first recess in the first film is the first recess. It is thinner at the top than the bottom. Therefore, the second film can be easily embedded in the second recess by a vapor deposition method such as a CVD method. Therefore, the second film can be a film made of a material having a high refractive index, and an optical waveguide having excellent light collecting properties can be formed.

  In the solid-state imaging device of the present invention, it is preferable that a plurality of layers including an interlayer insulating film are exposed on a side surface of the first recess, and the first film is in contact with the plurality of layers on a side surface of the first recess. .

  In the solid-state imaging device of the present invention, the second film may be formed in contact with the first film, and the second film may be embedded in the second recess to the upper end of the second recess. .

  In the solid-state imaging device of the present invention, the first film and the second film may be single layer films.

  In the solid-state imaging device of the present invention, the first film may be a silicon nitride film or a silicon nitride oxide film.

  In the solid-state imaging device of the present invention, the second film may be a silicon nitride film or a silicon oxynitride film.

  In the solid-state imaging device of the present invention, the straight line connecting the central portion and the lower end portion in the depth direction of the portion covering the side surface of the first recess in the first film is an angle formed with the direction parallel to the main surface of the semiconductor substrate. May be 75 ° or less.

  In the solid-state imaging device of the present invention, even if the film thickness of the portion formed on the side surface of the first recess in the first film is a ratio of 3: 7 or less between the upper part and the lower part of the first recess. Good.

  In the solid-state imaging device of the present invention, the bottom surface of the first recess may be a plane parallel to the main surface of the semiconductor substrate.

  In the solid-state imaging device of the present invention, the refractive index of the second film may be larger than the refractive index of the first film.

  In the solid-state imaging device of the present invention, it is preferable that the second film is not formed in a region outside the first recess.

  In the solid-state imaging device of the present invention, the upper surface of the first film may be formed in the same plane as the upper surface of the insulating film stack.

  In the solid-state imaging device of the present invention, the film thickness of the portion formed on the side surface of the first recess in the first film may increase linearly from the upper part to the lower part of the first recess. .

  In the solid-state imaging device of the present invention, the upper surface of the portion formed in the first recess in the second film may be formed in a convex lens shape.

  The method for manufacturing a solid-state imaging device according to the present invention includes a step of forming an insulating film stack having a first recess at a position corresponding to a light receiving element on a semiconductor substrate on which the light receiving element is formed, and the first recess. Forming an optical waveguide embedded in the insulating film stack, and the step of forming the optical waveguide includes insulating film lamination so that the second recess remains on the insulating film stack at a position corresponding to the first recess. A first film forming step of forming a first film having a refractive index higher than that of the body, and a film thickness of a portion formed on a side surface of the first recess in the first film And a second film having a refractive index higher than that of the insulating film stack on the first film so as to fill the second recess after the etching process. Film forming step.

  In the method for manufacturing a solid-state imaging device according to the present invention, the step of forming the optical waveguide is formed on the side of the first film forming step of forming the first film and the first recess of the first film. It includes an etching process in which the film thickness of the portion is made thinner in the upper part of the first recess than in the lower part, and a second film forming process in which the second film is formed so as to fill the second recess. For this reason, the thickness of the first film can be made thinner at the upper part of the first recess than at the lower part, and the second film can be formed without causing voids even when the aspect ratio is large. It becomes possible. Therefore, it becomes possible to easily form an optical waveguide having excellent light collecting properties.

  In the method for manufacturing a solid-state imaging device according to the present invention, the second film may be formed so as to be in contact with the first film, and may be formed so as to be embedded in the second recess up to the upper end of the second recess.

  In the method for manufacturing a solid-state imaging device of the present invention, the first film and the second film may be single-layer films.

  In the method for manufacturing a solid-state imaging device according to the present invention, the first film and the second film are preferably formed by chemical vapor deposition.

  In the method for manufacturing a solid-state imaging device according to the present invention, in the etching process, the straight line connecting the central portion in the depth direction and the lower end of the portion covering the side surface of the first recess in the first film is the main surface of the semiconductor substrate. It is preferable that the angle formed with the parallel direction is 75 ° or less.

  In the method for manufacturing a solid-state imaging device according to the present invention, in the etching step, the film thickness of the portion formed on the side surface of the first recess in the first film has a ratio of 3 between the upper portion and the lower portion of the first recess. : 7 or less.

  In the method for manufacturing a solid-state imaging device of the present invention, the etching step is preferably performed using nitrogen, hydrogen, or a fluorocarbon gas.

  In the method of manufacturing a solid-state imaging device according to the present invention, the step of forming the optical waveguide includes processing the upper surface of the portion formed in the first concave portion of the second film into a convex lens shape after the second film forming step. It is preferable to include a lens forming step.

  In the method for manufacturing a solid-state imaging device according to the present invention, the lens forming step may be a step of polishing the second film at a lower polishing rate than the first film.

  In the method for manufacturing a solid-state imaging device of the present invention, the lens forming step includes a step of forming a sacrificial film on the second film, and a step of etching back the sacrificial film and the second film. The etching may be performed under the condition that the etching rate of the second film is larger than the etching rate of the sacrificial film.

  In the method for manufacturing a solid-state imaging device of the present invention, the lens forming step includes a step of forming a sacrificial film on the second film, and a step of etching back the sacrificial film and the second film. The etching may be performed under the condition that the etching rate of the first film is larger than the etching rate of the second film.

  According to the solid-state imaging device and the manufacturing method thereof according to the present invention, it is possible to easily realize a solid-state imaging device including a highly condensing optical waveguide embedded with a material having a high refractive index.

It is sectional drawing which shows the solid-state imaging device which concerns on one Embodiment. It is sectional drawing which shows the manufacturing method of the solid-state imaging device which concerns on one Embodiment to process order. It is sectional drawing which shows the manufacturing method of the solid-state imaging device which concerns on one Embodiment to process order. It is sectional drawing which shows the manufacturing method of the solid-state imaging device which concerns on one Embodiment to process order. It is sectional drawing which shows the modification of the solid-state imaging device which concerns on one Embodiment. It is a plot which shows the relationship between the aspect-ratio of a recessed part, and the void which arises in an optical waveguide. It is a plot which shows the relationship between the inclination angle of the part formed on the side surface of the recessed part in a 1st film | membrane, and the void which arises in an optical waveguide. It is sectional drawing which shows the modification of the solid-state imaging device which concerns on one Embodiment. It is sectional drawing which shows the modification of the solid-state imaging device which concerns on one Embodiment. It is sectional drawing which shows the modification of the solid-state imaging device which concerns on one Embodiment. It is sectional drawing which shows the modification of the solid-state imaging device which concerns on one Embodiment. It is sectional drawing which shows the modification of the solid-state imaging device which concerns on one Embodiment. It is sectional drawing which shows the modification of the solid-state imaging device which concerns on one Embodiment. It is sectional drawing which shows the modification of the solid-state imaging device which concerns on one Embodiment.

  FIG. 1 shows one pixel of a solid-state imaging device according to an embodiment. As shown in FIG. 1, the solid-state imaging device of this embodiment is a complementary moss (CMOS) type sensor. A pixel including a light receiving element 111 is formed on a light receiving surface of a substrate 101 such as a silicon substrate, and an insulating film stack 102 and an optical waveguide 103 embedded in the insulating film stack 102 are formed on the substrate 101. Yes.

The light receiving element 111 may be a photodiode in which a pn junction is formed by the n-type charge storage layer 111A and the p ⁺ -type surface layer 111B. An element isolation region 112 is formed on the substrate 101 at the side of the light receiving element 111. The element isolation region 112 may be formed by injecting an impurity such as boron into a predetermined region of the substrate 101 by ion implantation or the like. A gate insulating film 113 made of silicon oxide (SiO ₂ ) or the like is formed on the substrate 101. A gate electrode 115 is formed on the gate insulating film 113 adjacent to the light receiving element 111. The gate electrode 115 may be a polysilicon film or a laminated film of a polysilicon film and a silicon compound film. The gate electrode 115 constitutes a transfer transistor that transfers signal charges generated and accumulated in the light receiving element 111 to a floating diffusion (not shown). In addition to the transfer transistor, a plurality of transistors that form pixels are formed on the substrate 101. An antireflection film 114 for preventing light incident on the light receiving element 111 from being reflected on the surface of the substrate 101 is formed on the gate insulating film 113 above the light receiving element 111. The antireflection film 114 may be a silicon nitride (SiN) film, a silicon oxynitride (SiON) film, or the like.

The insulating film laminate 102 has a plurality of wirings 104 embedded therein and has a recess in a region corresponding to the light receiving element 111. The first interlayer insulating film 121 covering the gate electrode 115 and the like may be a SiO ₂ film or a silicon oxide carbide (SiOC) film having a thickness of about 400 nm. A second interlayer insulating film 122 and a third interlayer insulating film 123 are sequentially formed on the first interlayer insulating film 121. The second interlayer insulating film 122 and the third interlayer insulating film 123 may be SiO ₂ films or SiOC films having a thickness of about 300 nm. A wiring 104 formed by a damascene process or the like is embedded in the second interlayer insulating film 122 and the third interlayer insulating film 123. The wiring 104 includes a copper film 143 with a thickness of about 200 nm embedded in a groove formed in the second interlayer insulating film 122 or the third interlayer insulating film 123, and a barrier metal film 142 that prevents diffusion of copper atoms. And have. The barrier metal film 142 may be tantalum or tantalum nitride having a thickness of about 20 nm. A diffusion prevention film 144 for preventing the diffusion of copper atoms is formed on the wiring 104. The diffusion prevention film 144 is a silicon carbide (SiC) film or a silicon oxide carbide (SiOC) film having a thickness of about 50 nm. A SiON film or a SiN film may be used. A flattened insulating film 124 made of a tetraethoxysilane (TEOS) film or the like is formed on the top of the insulating film stack 102 for flattening.

The optical waveguide 103 includes a first film 131 and a second film 132 embedded in a recess formed on the insulating film stack 102 above the light receiving element 111. The first film 131 is preferably an insulating film having a high refractive index, but may be a film having a refractive index smaller than that of the interlayer insulating film included in the insulating film stack 102. The second film 132 is preferably an insulating film having a refractive index as high as possible. The second film 132 is a film having a refractive index higher than that of at least the interlayer insulating film constituting the insulating film stack 102 and is refracted more than the first film 131. A film having a rate may be used. As the interlayer insulating film, a SiO ₂ film having a refractive index of about 1.4 to 1.5 or a SiOC film having a refractive index of about 1.5 to 1.6 is usually used. Therefore, the first film 131 and the second film 132 are a SiN film having a refractive index of about 1.9 to 2.0 or a silicon oxynitride (SiON) film having a refractive index of about 1.6 to 1.8. Etc. are preferable. The first film 131 and the second film 132 may be formed using different materials. For example, the second film may be a SiN film and the first film may be a SiON film. Further, the first film 131 can be a SiOC film, a SiO ₂ film, or the like.

  In the portion of the first film 131 formed on the side surface of the recess, the film thickness W1 at the top of the recess is smaller than the film thickness W2 at the bottom of the recess. Therefore, the second film 132 can be easily embedded by a vapor deposition method or the like. In the present embodiment, the light receiving element 111 has a width of about 700 nm, and the concave portion has a width of about 1000 nm and a depth of about 600 nm. In this case, the thickness W1 in the upper part of the recess of the first film 131 may be about 200 nm, and the thickness W2 in the lower part of the recess may be about 400 nm.

  On the second film 132, a planarizing resin layer 151, a color filter 152, a planarizing film 153, and a microlens 154 are sequentially formed. The planarizing resin layer 151 is provided to improve the flatness of the upper surface of the second film 132 and the adhesiveness of the color filter 152. Note that the second film 132 is not necessarily provided as long as the flatness of the second film 132 is sufficient. Although only one color filter 152 is shown in FIG. 1, red (R), green (G), and blue (B) filters are arranged in a Bayer array. The color filter array may be an array other than the Bayer array. Also, a complementary color filter may be used. The planarization film 153 is provided to reduce a step generated between the color filters 152 having different colors. The microlens 154 is provided in order to improve the light collecting property to the light receiving element 111.

  Below, the formation method of the optical waveguide 103 is demonstrated. After the insulating film stack 102 in which the wiring 104 is embedded is formed on the substrate 101 on which the light receiving element 111 and the like are formed by a known method, as shown in FIG. A recess 102 a is formed on the upper side of the light receiving element 111. In FIG. 2A, the recess 102 a does not reach the first interlayer insulating film 121, but the recess 102 a may reach the first interlayer insulating film 121. The bottom surface of the recess 102 a is preferably a surface parallel to the main surface of the substrate 101. The width and depth of the recess 102a may be determined in consideration of the planar dimensions of the light receiving element 111 and the light condensing property when the microlens 154 and the optical waveguide 103 are combined. In the present embodiment, description will be made assuming that the width of the recess 102a is 1000 nm and the depth is 600 nm (aspect ratio is 0.6).

  Next, as shown in FIG. 2B, a first film 131 made of SiN or the like is formed using a chemical vapor deposition method (CVD method) or the like. When a SiN film or the like is deposited by the CVD method, the thickness of the upper portion of the recess 102a is larger than that of the lower portion, and an overhang portion is formed. When the concave portion 102a is blocked by the overhang portion, it becomes difficult to fill the concave portion 102a with the second film 132. Therefore, the upper portion of the concave portion 102a is not blocked in the first film 131, and the concave portion 102b remains at a position corresponding to the concave portion 102a. To be formed. In order to prevent the upper portion of the concave portion 102a from being blocked, it is preferable that the film thickness of the region (flat portion) excluding the concave portion 102a in the insulating film stacked body 102 is set to about 60% or less of the width of the concave portion 102a. In the present embodiment, an example in which the thickness of the flat portion in the insulating film stack 102 is 500 nm will be described.

  Next, as shown in FIG. 3A, etch-back using a dry etching method is performed to remove the overhang portion. As a result, the film thickness of the first film 131 at the upper part of the recess 102a is smaller than that at the lower part. Accordingly, the concave portion 102c having a wider width at the upper end portion than the bottom surface is formed. In the present embodiment, if the amount of etch back in the flat portion is about 300 nm, the overhang portion is removed, and the thickness of the upper portion of the recess 102a can be made thinner than that of the lower portion. As a result, the film thickness W1 of the first film 131 in the upper part of the recess 102a is about 150 nm, and the film thickness W2 in the lower part is about 350 nm. If the film thickness W1 is about 7/3 or less of the film thickness W2, the occurrence of voids can be avoided even when the aspect ratio is about 0.6.

  Next, as shown in FIG. 3B, a second film 132 made of SiN or the like is deposited by using a CVD method or the like, and the recess 102c is embedded. On the upper surface of the second film 132, a recess 132a is formed at a position corresponding to the recess 102c.

  Next, as shown in FIG. 4A, the upper surface of the second film 132 is polished and planarized using a chemical mechanical polishing method (CMP method) or the like.

  Next, as shown in FIG. 4B, a planarizing resin layer 151, a color filter 152, a planarizing film 153, a microlens 154, and the like are sequentially formed. In the present embodiment, the configuration in which the color filter 152 is formed without breaks is shown. However, an isolation insulating film 156 may be formed between the color filters 152 as shown in FIG. By surrounding the color filter with a material having a refractive index lower than that of the color filter 152, the light condensing property of the color filter 152 can be improved. Since the refractive index of a general color filter is about 1.5 to 1.7, the insulating film 156 may be a TEOS film (refractive index 1.45) having a lower refractive index.

  In the present embodiment, the first film 131 and the second film 132 are sequentially formed to fill the recess 102a. In addition, after the first film 131 is formed, etch back is performed so that the film thickness W1 in the upper part of the recess 102a is smaller than the film thickness W2 in the lower part. For this reason, when the second film 132 is formed, the gas source is sufficiently supplied into the recess 102a. Therefore, even when a film made of a material having a high refractive index is formed using a CVD method or the like, voids are less likely to be generated in the second film 132 inside the recess 102a. As a result, it is possible to efficiently form an optical waveguide having a high refractive index and excellent light collecting properties.

  FIG. 6 shows the relationship between the aspect ratio of the recess and the width of the void generated in the optical waveguide. The width of the void is the maximum value in the direction parallel to the main surface of the substrate. The sensitivity reduction rate on the second vertical axis is theoretically calculated from the width of the void. The optical waveguide used for the evaluation has a SiN film formed by the CVD method. In addition, the ratio of the thickness of the upper portion of the concave portion to the thickness of the lower portion of the first film is 3/7.

  In a conventional optical waveguide formed by embedding an insulating film in a recess at a time, a large void is generated even when the aspect ratio is small, and a decrease in sensitivity due to the void is inevitable. On the other hand, the optical waveguide of the present embodiment, which is formed by embedding the second film after forming the first film whose thickness at the upper part of the recess is smaller than the film thickness at the lower part, has an aspect ratio of about 0.6. Has no voids. As described above, in the present embodiment, even when the aspect ratio is large, it is possible to form an optical waveguide with high light condensing property using a material having a high refractive index, and solid imaging having excellent light condensing property. A device can be realized.

FIG. 7 shows the relationship between the inclination angle α of the portion of the first film 131 formed on the side surface of the recess 102a and the void width. The tilt angle α in FIG. 7 is a direction parallel to the main surface of the substrate 101 and a straight line connecting the lower end portion indicated by the symbol A in FIG. 1 and the central portion in the depth direction indicated by the symbol B (see FIG. It means the angle α formed by (horizontal direction). The aspect ratio of the recess 102a used for the evaluation is 0.6. As shown in FIG. 7, the occurrence of voids in the optical waveguide 103 can be suppressed by setting the inclination angle α of the first film 131 to 75 ° or less. For example, in the case of etchback using monofluoromethane (CH ₃ F) and oxygen (O ₂ ), the inclination angle α is adjusted by changing the ratio of CH ₃ F and O _2. Can do.

  An optical waveguide embedded with a second film 132 made of SiN having a refractive index of about 1.93 by a CVD method and an optical waveguide embedded with a titanium-containing siloxane polymer having a refractive index of about 1.75 by a coating method. Actually created and compared. When the SiN film was used, the amount of light incident on the light receiving element 111 was improved by at least 10% or more compared to the case where the titanium-containing siloxane polymer was used. As described above, the solid-state imaging device according to the present embodiment can be embedded with a material having a high refractive index such as SiN without generating voids, and is useful for improving the light collecting property.

  In the present embodiment, the method for polishing and planarizing the second film 132 by a CMP method or the like has been described. However, as shown in FIG. 8, after the sacrificial film 161 for planarization made of a coating film is formed on the second film 132, the sacrificial film 161 and the second film 132 are etched to form the second film 132. The film 132 may be planarized. The sacrificial film 161 may be a resist film, a spin-on-glass (SOG) film, or the like.

  The light condensing property of the optical waveguide 103 is affected by the length (depth) of the optical waveguide 103 in the direction perpendicular to the main surface of the substrate 101. Therefore, the amount of polishing when the second film 132 is planarized may be adjusted so as to ensure a depth at which the light condensing performance is maximized by the combination with the microlens 154. If necessary, as shown in FIG. 9, a portion of the second film 132 formed on the flat portion may be removed. In addition, as shown in FIG. 10, the portion formed on the flat portion of the first film 131 may be removed. FIG. 10 shows an example in which the portion formed on the flat portion of the first film 131 is completely removed. However, the first film having a predetermined thickness is formed on the flat portion of the insulating film stack 102. The film 131 may be left. By removing a portion of the second film 132 and the first film 131 formed in a region excluding the concave portion 102a, light is leaked to the outside of the concave portion 102a by the second film 132 and the first film 131. The effect that it can prevent is also acquired.

  In the present embodiment, an example in which the concave portion 102c remaining after the first film 131 is formed has a flat bottom surface is shown. However, it is only necessary that the thickness of the portion formed in the upper portion of the recess 102a in the first film 131 is larger than the thickness of the portion formed in the lower portion, and it is not necessary to form a flat bottom surface. For example, as shown in FIG. 11, the first film 131 may leave a concave portion having a V-shaped cross section. By making the remaining concave portion have a V-shaped cross section, the inclination angle α of the portion formed on the side surface of the concave portion of the first film 131 can be further increased, and the second film 132 can be embedded more easily. The advantage of becoming is obtained.

In order to increase the inclination angle α, the first film 131 is thickly formed using a highly depositable gas such as nitrogen (N ₂ ), hydrogen (H ₂ ), or a fluorocarbon-based gas, and etching is performed. do it. As the fluorocarbon-based gas, a gas represented by a general formula CH _x F _y can be used. It is possible to use carbon tetrafluoride that does not contain H (x = 0) as the fluorocarbon gas. However, the larger the x, the stronger the depositability, and CH ₃ F, CHF _3, etc. may be used. preferable. When a gas having a high deposition property is used for etching, an etching stop may occur, but the addition of oxygen (O ₂ ) or the like can suppress the generation of the etching stop. For example, when a fluorocarbon gas represented by CH _x F _y is used, H and F are dissociated to generate CH _x2 F _y2 having a surplus bond, and CH _x2 F _y2 Polymerization occurs. The dissociation of H and F promotes gas decomposition as the power applied to decompose the etching gas is increased. For this reason, if the electric power applied in the range where an etching stop does not occur is increased, the polymer film is formed thicker, and the width can be reduced at the lower part of the recess. In addition, the higher the gas pressure, the weaker the directivity of ions in the plasma, and the slower the rate of disappearance between the formation and disappearance of the polymerized film. For this reason, when the gas pressure is increased within a range where no etching stop occurs, the thickness of the polymerized film increases, and the inclination angle α can be further increased.

  Further, the side surface of the recess 102a formed in the insulating film laminate 102 does not need to be perpendicular to the main surface of the substrate 101, and the width of the upper end is wider than the width of the lower end as shown in FIG. It may be a different shape. If the inclination of the side surface of the recess 102a is increased, the optical waveguide 103 can be embedded more easily. On the other hand, if it is attempted to increase the inclination of the side surface of the recess 102a, the flatness of the bottom surface is impaired, and light may not easily enter the light receiving element 111. The insulating film laminate 102 is a laminate of a plurality of films made of different materials, and it is difficult to increase the inclination of the side surface of the recess. However, if the inclination of the side surface of the recess formed in the insulating film laminate 102 is increased within a range where the flatness of the bottom surface is not impaired, there is an advantage that the optical waveguide 103 can be embedded more easily.

  In the present embodiment, an example in which the upper surface of the second film 132 is planarized has been described. However, as shown in FIG. 13, the upper surface of the portion formed in the concave portion of the second film 132 may be processed into a convex lens shape. By making the upper surface of the second film 132 into a convex lens shape, the light condensing property to the light receiving element 111 can be further improved.

  When the upper surface of the second film 132 is processed into a convex lens shape, a sacrificial film 161 is formed on the second film 132 as shown in FIG. 8, and then the sacrificial film 161 and the second film 132 are formed. It may be formed by etching. When the upper surface of the second film 132 is processed into a convex lens shape, the sacrificial film 161 and the second film 132 are etched on the entire surface under the condition that the etching rate of the second film 132 is larger than the etching rate of the sacrificial film 161. The sacrificial film 161 may be removed by processing. The sacrificial film 161 is a resist film or an SOG film, and the film thickness may be about 800 nm. Further, the upper surface of the second film 132 can be processed into a convex lens shape even if the etching process is performed under the condition that the etching rate of the first film 131 is larger than that of the second film 132. Further, the sacrificial film 161 is not formed, and the second film 132 is deposited as shown in FIG. 3B, and the etching rate of the first film 131 is higher than that of the second film 132 after the recess 102c is filled. Even if the etching process is performed under a large condition, the upper surface of the second film 132 can be processed into a convex lens shape.

  Further, as shown in FIG. 14, etching may be performed until a structure in which the portion of the second film 132 formed on the flat portion of the insulating film stack 102 is removed is obtained. Note that FIG. 14 shows an example in which the first film 131 remains on the flat portion of the insulating film stack 102, but the first film 131 on the flat portion of the insulating film stack 102 is shown. The portion formed in the step may be completely removed.

  Even when the upper surface of the second film has a convex lens shape, the taper angle of the concave portion remaining after the first film is deposited may be reduced. Alternatively, the side surface of the recess formed in the insulating film stack may be inclined. Further, the color filters may be separated from each other by an insulating film.

  In the present embodiment, an example in which the insulating film laminate includes two layers of wirings is shown. However, three or more layers of wirings may be formed.

  In the present embodiment, an example in which the optical waveguide is formed by embedding the first film and the second film in the recess has been described. However, the deposition and etching of the film in the recess are repeated twice or more, and The above film may be embedded. Although an example in which the CVD method is used for depositing the first film and the second film has been described, a physical vapor deposition (PVD) method or the like can also be used.

  In the present embodiment, the MOS type solid-state imaging device has been described. However, the present invention can also be applied to a CCD (Charge Coupled Device) type solid-state imaging device.

  The solid-state imaging device and the manufacturing method thereof according to the present invention can easily realize a solid-state imaging device including a highly condensing optical waveguide embedded with a material having a high refractive index, and are small and highly sensitive. It is useful as a manufacturing method thereof.

DESCRIPTION OF SYMBOLS 101 Substrate 102 Insulating film laminated body 102a Concave part 102b Concave part 102c Concave part 103 Optical waveguide 104 Wiring 111 Light receiving element 111A Charge storage layer 111B Surface layer 112 Element isolation region 113 Gate insulating film 114 Antireflection film 115 Gate electrode 121 First interlayer insulating film 122 Second interlayer insulating film 123 Third interlayer insulating film 124 Planarizing insulating film 131 First film 132 Second film 132a Recess 141 Wiring 142 Copper film 143 Barrier metal film 144 Diffusion prevention film 151 Flattening resin layer 152 Color filter 153 Flattening film 154 Micro lens 156 Insulating film 161 Sacrificial film

Claims (24)

A light receiving portion formed on a semiconductor substrate;
An insulating film stack formed on the semiconductor substrate, including an interlayer insulating film, and having a first recess at a position corresponding to the light receiving portion;
An optical waveguide formed in the first recess and guiding light to the light receiving unit;
The optical waveguide has a first film and a second film sequentially formed from the insulating film laminate side,
The refractive index of the first film and the second film is higher than the refractive index of the interlayer insulating film,
The first film has a second recess covering a side surface and a bottom surface of the first recess and corresponding to the first recess,
The second film is formed so as to be embedded in the second recess;
The first side thickness of the portion formed on the concave portion of the first film, rather thin than the lower in the upper portion of the first recess,
A plurality of layers including the interlayer insulating film are exposed on a side surface of the first recess,
The solid-state imaging device , wherein the first film is in contact with the plurality of layers on a side surface of the first recess . The second film is formed in contact with the first film;
2. The solid-state imaging device according to claim 1, wherein the second film is embedded in the second concave portion up to an upper end of the second concave portion. The solid-state imaging device according to claim 1 or 2, wherein the first film and the second film is characterized in that it is a single-layer film. The first film is a solid-state imaging device according to any one of claims 1 to 3, characterized in that a silicon film or a silicon oxynitride film nitride. Said second film is a solid-state imaging device according to any one of claims 1 to 4, characterized in that a silicon film or a silicon oxynitride film nitride. The straight line connecting the central portion in the depth direction and the lower end portion of the portion covering the side surface of the first recess in the first film has an angle of 75 ° or less with the direction parallel to the main surface of the semiconductor substrate. the solid-state imaging device according to any one of claims 1 to 5, characterized in that. The film thickness of a portion formed on the side surface of the first recess in the first film is such that a ratio of the upper portion and the lower portion of the first recess is 3: 7 or less. The solid-state imaging device according to any one of 1 to 6 . The bottom surface of the first recess, the solid-state imaging device according to any one of claims 1 to 7, characterized in that a main surface parallel planes of the semiconductor substrate. The refractive index of the second film, a solid-state imaging device according to any one of claims 1 to 8, wherein greater than the refractive index of the first film. It said second film is a solid-state imaging device according to any one of claims 1 to 9, characterized in that it is not formed in the outer region of the first recess. The top surface of the first film, a solid-state imaging device according to any one of claims 1 to 10, characterized in that formed on the upper surface flush with the insulating film laminate. 2. The film thickness of a portion of the first film formed on the side surface of the first recess increases linearly from the upper part to the lower part of the first recess. The solid-state imaging device according to any one of 1 to 11 . Wherein said first recess portion formed in the second film, a solid-state imaging device according to any one of claims 1 to 1 2, characterized in that the upper surface is formed in a convex lens shape. Forming an insulating film laminate having a first recess at a position corresponding to the light receiving element on the semiconductor substrate on which the light receiving element is formed;
Forming an optical waveguide embedded in the first recess,
The step of forming the optical waveguide includes:
A first film forming a first film having a higher refractive index than that of the insulating film stack so that a second recess remains on the insulating film stack at a position corresponding to the first recess. Process,
An etching step of making the film thickness of the portion formed on the side surface of the first recess in the first film thinner than the lower part at the upper part of the first recess;
And a second film forming step of forming a second film having a higher refractive index on the first film than the insulating film stack so as to fill the second recess after the etching step. ,
A plurality of layers including the interlayer insulating film are exposed on a side surface of the first recess,
The method of manufacturing a solid-state imaging device , wherein the first film is in contact with the plurality of layers on a side surface of the first recess . The solid-state imaging device according to claim 14 , wherein the second film is formed so as to be in contact with the first film and to be embedded in the second concave portion up to an upper end of the second concave portion. Manufacturing method. 16. The method of manufacturing a solid-state imaging device according to claim 14, wherein the first film and the second film are single layer films. The method of manufacturing a solid-state imaging device according to claim 14 , wherein the first film and the second film are formed by a chemical vapor deposition method. In the etching step, an angle formed by a straight line connecting a central portion and a lower end portion in the depth direction of a portion covering the side surface of the first recess in the first film is parallel to the main surface of the semiconductor substrate. The manufacturing method of the solid-state imaging device according to claim 14 , wherein the angle is set to 75 ° or less. In the etching step, the thickness of the portion of the first film formed on the side surface of the first recess is such that the ratio between the upper and lower portions of the first recess is 3: 7 or less. The method for manufacturing a solid-state imaging device according to claim 14 , wherein the solid-state imaging device is manufactured. The method of manufacturing a solid-state imaging device according to claim 14 , wherein the etching step is performed using nitrogen, hydrogen, or a fluorocarbon-based gas. The step of forming the optical waveguide includes a lens forming step of processing an upper surface of a portion formed in the first concave portion of the second film into a convex lens shape after the second film forming step. The method for manufacturing a solid-state imaging device according to claim 14 , wherein: The method of manufacturing a solid-state imaging device according to claim 21 , wherein the lens forming step is a step of polishing the second film at a polishing rate lower than that of the first film. The lens forming step includes a step of forming a sacrificial film on the second film, and a step of etching back the sacrificial film and the second film,
The method of manufacturing a solid-state imaging device according to claim 21 , wherein the etch back is performed under a condition that an etch rate of the second film is larger than an etch rate of the sacrificial film. The lens forming step includes a step of forming a sacrificial film on the second film, and a step of etching back the sacrificial film and the second film,
The method of manufacturing a solid-state imaging device according to claim 21 , wherein the etch back is performed under a condition that an etch rate of the first film is larger than an etch rate of the second film.

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