JP2007173717A - Solid imaging element, and method for manufacturing same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively improve light condensation efficiency of a solid imaging element by microfabricating the element and solving accompanying elicited problem points about an in-layer lens. <P>SOLUTION: The solid imaging element has a photoelectric conversion unit 30, a charge transfer unit 80 which transfers electric charges generated by the photoelectric conversion unit 30, and an optical waveguide which guides incident light to the photoelectric conversion unit 30, and the optical waveguide comprises a coating layer 7 which covers the charge transfer unit 80 and has an opening part having an internal wall surface nearly vertically above the photoelectric conversion unit 30 and a light-transmissive material part formed in the opening part, the internal wall surface and top surface of the coating layer 7 having light shielding property. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a solid-state imaging device and a method for manufacturing the solid-state imaging device.

  Examples of the solid-state imaging device include a charge coupled device (CCD) image sensor (hereinafter simply referred to as a CCD) and a complementary metal oxide semiconductor (CMOS) image sensor. This is used in various applications such as a digital camera, a video camera, a mobile phone device with a camera, a scanner device, a digital copying machine, and a facsimile machine. In addition, as devices using such solid-state image sensors become widespread, in addition to higher functions and higher performance such as an increase in the number of pixels and an improvement in light receiving sensitivity, solid-state image sensors can be reduced in size and size. The demand for pricing is increasing.

  As described above, when the solid-state imaging device is miniaturized and the pixels are increased, and at the same time, the price is required to be reduced, the pixel size is further reduced. As the pixel size is reduced, the light receiving sensitivity, which is one of the basic performances of the solid-state imaging device, is lowered. Therefore, it is difficult to capture a clear image at low illuminance. Therefore, how to improve the light receiving sensitivity per unit pixel is an important problem.

As a method for improving the light receiving sensitivity by increasing the light collection efficiency of the solid-state imaging device, there is a method of forming a microlens with an organic polymer material above the color filter and further forming an in-layer lens below the microlens. It is known (see, for example, Patent Document 1).
FIG. 17 is a cross-sectional view showing the structure of the CCD solid-state imaging device. In the CCD solid-state imaging device, a photoelectric conversion unit (light receiving unit) 212, a readout gate unit 214, and a CCD transfer channel 216 are formed in a semiconductor substrate 210, and a transfer electrode 220 is formed through an insulating film 218. ing. A light shielding film 224 is formed on the transfer electrode 220 via an interlayer insulating film 222, and the light shielding film 224 prevents light from entering the transfer electrode 220. Further, the light shielding film 224 is provided with an opening on the light receiving unit 212 so that light can enter the light receiving unit 212. Then, an interlayer insulating layer 226 made of a reflow film such as a BPSG (boron phosphorus silicate glass) film or an HDP (high density plasma) CVD film is formed so as to cover the light shielding film 224. The interlayer insulating layer 226 is formed so as to have a recess on the photoelectric conversion unit 212, for example, by setting the composition of BPSG to a predetermined composition.

  Then, on the interlayer insulating layer 226, an in-layer lens 228 (consisting of an upwardly convex lens surface 228a and a downwardly convex lens surface 228b) is formed. A planarizing layer 230 made of, for example, an acrylic resin film (refractive index n = 1.3 to 1.4) or the like is formed on the in-layer lens 228, and a color filter 232 is further formed thereon. Further, a micro lens (so-called on-chip lens) 234 is formed on the color filter 232.

As described above, by providing the inner lens 228 under the microlens 234, incident light can be condensed in two stages, and more light can be incident on the photoelectric conversion unit 212. Therefore, the sensitivity of the CCD solid-state imaging device can be improved as compared with the case where only the on-chip lens is formed.
JP 2000-164837 A

  However, in the conventional CCD solid-state imaging device having a structure in which the lens in the layer described above is provided, the lens shape is determined by the concave shape of the interlayer insulating layer 226 on the light shielding film 224. In some cases, the shape may vary, and a desired light collection efficiency may not be obtained. Furthermore, with the miniaturization of elements, voids are generated in the inner lens 228 due to the coverage of the CVD film, and this may hinder the improvement of the light collection efficiency. Further, in the solid-state imaging device of FIG. 17, a stepped portion (step) due to the light shielding film 224 is generated below the intralayer lens 228, and incident light may be scattered by this stepped portion and become stray light. is there. In FIG. 17, an example of the path of incident light is indicated by an arrow.

  The present invention has been made on the basis of such considerations, and its object is to eliminate the problem of the intralayer lens that becomes apparent as the element is miniaturized, and to improve the light collection efficiency of the solid-state imaging device. It is in.

The above object of the present invention is achieved by the following configuration.
(1) A solid-state imaging device having a photoelectric conversion unit, a charge transfer unit that transfers charges generated by the photoelectric conversion unit, and an optical waveguide that guides incident light to the photoelectric conversion unit. A coating layer having an opening in which a waveguide covers the charge transfer portion and an inner wall surface is formed substantially vertically above the photoelectric conversion portion; and a translucent material portion formed in the opening. A solid-state imaging device comprising: an inner wall surface and an upper surface of the covering layer having light shielding properties.

  According to this solid-state imaging device, since the optical waveguide is provided and the incident light is guided to the photoelectric conversion unit by the optical waveguide, the light collection efficiency can be reliably improved. The optical waveguide is formed by a coating layer provided so as to cover the charge transfer unit and having an opening for enabling light to be guided onto the photoelectric conversion unit. The opening is an opening that linearly penetrates the coating layer, and the inner wall surface and the upper surface of the coating layer have a light-shielding property. It can be reliably reflected to the photoelectric conversion part by reflecting on the inner wall surface. If anisotropic etching is used, it is easy to form a substantially vertical inner wall surface. Therefore, a columnar opening suitable for guiding light downward can be easily formed. The formation of an in-layer lens requires processes that are considerably difficult in manufacturing, such as forming the curvature of the lens by reflow processing, but the optical waveguide uses a coating layer deposition technique and an anisotropic etching technique such as RIE. Therefore, it can be formed relatively easily and its processing accuracy is high, so that stable light collecting performance can be realized with certainty.

(2) The solid-state imaging device according to (1), wherein the coating layer is a light-shielding film made of a metal material.

  According to this solid-state imaging device, an optical waveguide can be easily formed by providing an opening in a light shielding film made of a metal such as tungsten (W).

(3) The solid-state imaging device according to (1), wherein the optical waveguide is provided with a coating layer made of a light-shielding material on the photoelectric conversion unit and the charge transfer unit, and then the planarization process is performed on the coating layer. The upper surface of the coating layer is flattened, the portion of the coating layer located above the photoelectric conversion portion is removed, and an opening penetrating the coating layer is provided. Solid-state image sensor.

  According to this solid-state imaging device, the coating layer made of a light-shielding material is provided, planarized, and the planarized coating layer is selectively removed by anisotropic etching or the like, so that an opening penetrating the coating layer is formed. By forming the optical waveguide, it is possible to form the optical waveguide with high accuracy without difficulty.

(4) The solid-state imaging device according to (1), wherein the coating layer constituting the optical waveguide includes an opening that penetrates the coating layer, and a light-shielding material film provided on an inner wall surface and an upper surface of the opening And a solid-state imaging device.

  According to this solid-state imaging device, the optical waveguide can be formed by the opening and the light-shielding material film provided on the inner wall surface and the upper surface of the opening. A light-shielding material film is selectively formed on the surface of an interlayer film that can be easily processed to reflect incident light.

(5) The solid-state imaging device according to (1), wherein the optical waveguide is provided with a coating layer on the photoelectric conversion unit and the charge transfer unit, and then a planarization process is performed on the coating layer to form an upper surface thereof. Flattening, forming a first light-shielding layer made of a light-shielding material on the surface of the coating layer, and further removing the portion of the coating layer located above the photoelectric conversion unit to form the first light-shielding layer Through a step of forming a penetrating opening and providing a second light-shielding layer made of a light-shielding material and connected to the first light-shielding layer on the inner wall surface of the coating layer generated along with the formation of the opening. A solid-state image pickup device formed.

  According to this solid-state imaging device, a coating layer is provided, and after the coating layer is planarized, the first light shielding layer is selectively formed on the surface of the coating layer, and the coating layer is selectively formed by anisotropic etching or the like. An optical waveguide using a composite film is formed by forming an opening that penetrates the coating layer and forming a second light shielding layer connected to the first light shielding layer on the inner wall surface of the coating layer. It can be formed with high accuracy without difficulty.

(6) The solid-state imaging device according to any one of (1) to (5), wherein a light shielding material made of a light shielding material that covers the charge transfer unit is provided below the film constituting the optical waveguide. A solid-state imaging device, wherein a film is formed.

  According to this solid-state imaging device, since the light-shielding film that covers the charge transfer portion including the transfer electrode is further formed under the film that becomes the optical waveguide, it is possible to reliably prevent the occurrence of smear due to the wraparound of incident light. be able to. That is, when the thickness of the light-transmitting insulating film provided on the photoelectric conversion portion of the semiconductor substrate increases, the light propagating in the optical waveguide passes obliquely through the insulating film and wraps around the charge transfer portion side. In some cases, such light that wraps around can be reliably blocked by the light shielding film.

(7) The solid-state imaging device according to any one of (1) to (6), wherein a microlens for condensing light toward the optical waveguide is provided above the optical waveguide. A solid-state imaging device.

  According to this solid-state imaging device, the light collected by the microlens (on-chip lens) can be guided to the photoelectric conversion unit by the optical waveguide, so that the light collection efficiency can be improved.

(8) The solid-state imaging device according to (7), wherein an in-layer lens is provided between the microlens and the optical waveguide.

  According to this solid-state imaging device, incident light can be efficiently guided to the photoelectric conversion unit by a synergistic effect of the microlens (on-chip lens), the in-layer lens, and the optical waveguide.

(9) A method for manufacturing a solid-state imaging device, comprising: a photoelectric conversion unit; a charge transfer unit that transfers charges generated by the photoelectric conversion unit; and an optical waveguide that guides incident light to the photoelectric conversion unit. A first step of forming the photoelectric conversion unit in the semiconductor substrate, a second step of forming a charge transfer unit including a charge transfer electrode in the semiconductor substrate and on the semiconductor substrate, the photoelectric conversion unit and the charge After providing a coating layer made of a light-shielding material on the transfer unit, the coating layer is subjected to a planarization process to planarize the upper surface, and a portion of the coating layer located above the photoelectric conversion unit is removed. And a third step of forming the optical waveguide by providing an opening that penetrates the coating layer.

  According to this method for manufacturing a solid-state imaging device, after forming a photoelectric transfer portion and a charge transfer portion including a transfer electrode, a coating layer made of a light-shielding material is provided and planarized, and the coating layer after the planarization treatment is anisotropic It is possible to form the optical waveguide with high accuracy without difficulty by selectively removing it by reactive etching or the like and forming an opening that penetrates the coating layer.

(10) A method for manufacturing a solid-state imaging device, comprising: a photoelectric conversion unit; a charge transfer unit that transfers charges generated by the photoelectric conversion unit; and an optical waveguide that guides incident light to the photoelectric conversion unit. A first step of forming the photoelectric conversion unit in the semiconductor substrate, a second step of forming a charge transfer unit including a charge transfer electrode in the semiconductor substrate and on the semiconductor substrate, the photoelectric conversion unit and the charge After providing a coating layer on the transfer portion, the coating layer is subjected to a planarization process to planarize the upper surface, and a first light-shielding layer made of a light-shielding material is formed on the surface of the coating layer. A portion of the coating layer located above the photoelectric conversion portion is removed to form an opening that penetrates the first light shielding layer, and on the inner wall surface of the coating layer that is generated along with the formation of the opening, Consisting of the light shielding material and connected to the first light shielding layer Method for manufacturing a solid-state imaging device characterized by comprising a third step of forming the optical waveguide by the second providing the light-shielding layer that.

  According to this method of manufacturing a solid-state imaging device, after forming the charge transfer unit including the photoelectric conversion unit and the transfer electrode, the coating layer is provided, the coating layer is planarized, and then selectively applied to the surface of the coating layer. 1 light shielding layer is formed, the coating layer is selectively removed by anisotropic etching or the like, an opening penetrating the coating layer is formed, and an inner wall surface of the coating layer is connected to the first light shielding layer. By forming the second light shielding layer, an optical waveguide using the composite film can be formed with high accuracy without difficulty.

  According to the present invention, by providing the optical waveguide, the light collected by the microlens can be reliably guided to the photoelectric conversion unit by the optical waveguide, and thus the light collection efficiency can be reliably improved. . In addition, the optical waveguide can be formed relatively easily using a coating layer deposition technique and an anisotropic etching technique such as RIE, and its processing accuracy is high, so that stable light collection performance can be realized with certainty. it can. Furthermore, after the coating layer is flattened, the film is selectively removed by anisotropic etching or the like to form an opening that linearly penetrates the coating layer, thereby forming a substantially vertical inner wall surface. Therefore, a columnar opening suitable for guiding light downward can be easily formed.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a solid-state imaging device and a manufacturing method thereof according to the present invention will be described in detail with reference to the drawings.
(First embodiment)
First, the structure of the solid-state imaging device of the present invention will be described. 1 is a schematic plan view of a solid-state imaging device according to the present invention, FIG. 2 is an enlarged plan view of a pixel portion of the solid-state imaging device shown in FIG. 1, and FIG. 3 is a schematic cross-sectional view taken along line AA in FIG.
A large number of photoelectric conversion units (photodiodes) 30 are formed in the light receiving region 43 in the image sensor formation region 47 of the solid-state image sensor 100 shown in FIGS. 1 to 3, and signal charges generated by the photodiodes 30 are arranged in the column direction. A vertical transfer path 15 for transferring in the (Y direction in FIG. 1) is formed by meandering between a plurality of photodiode rows composed of a plurality of photodiodes 30 arranged in the column direction. The vertical transfer path 15 is connected to a horizontal transfer CCD (HCCD) 40, and an output amplifier 41 is provided on the end side of the horizontal transfer CCD (HCCD) 40.

  The charge transfer unit includes a plurality of charge transfer channels 15 formed in the column direction of the surface portion of the silicon substrate 10 corresponding to each of the plurality of photodiode columns, and two layers formed above the charge transfer channel 15. It includes a charge transfer electrode 17 (first electrode 17a, second electrode 17b) having an electrode structure, and a charge read region 14 (see FIG. 1) for reading charges generated in the photodiode 30 to the charge transfer channel 15. . The charge transfer electrode 17 has a meandering shape extending in the row direction (X direction in FIG. 1) as a whole between a plurality of photodiode rows composed of a plurality of photodiodes 30 arranged in the row direction. (See FIG. 2). The charge transfer electrode 17 may have a single layer electrode structure.

  As shown in FIG. 3, the solid-state image sensor 100 is formed on an n-type semiconductor substrate 10. An interelectrode insulating film 4 in which a first layer electrode 3a and a second layer electrode 3b are formed of a silicon oxide film 4a and an HTO film 4b via a gate oxide film 2 (2a, 2b, 2c) on the charge transfer portion 80. To form a charge transfer electrode. Reference numeral 111 is an n-type impurity layer, and reference numeral 113 is a p-type impurity layer. Further, a first oxide film 5a, a silicon nitride film (SiN) 6, and a second oxide film 5b are formed on the charge transfer electrode.

  The photodiode 30 includes an n-type impurity region 31 that forms a pn junction with the p-well 12 and a high-concentration p-type impurity region 32 as a surface potential adjustment layer formed on the surface of the n-type impurity region 31. Is formed. Reference numeral 11 is a channel stop region. The gate oxide film 2 is a laminated structure (ONO) film including a bottom oxide film 2a made of a silicon oxide (SiO) film, a silicon nitride (SiN) film 2b, and a top oxide film 2c made of a silicon oxide (SiO) film. Consists of. An overdrain buffer layer 13 made of a p-type semiconductor layer is formed below the p-well 12 so that charges can be drawn out by applying a voltage.

  Silicon oxide films 5a and 5b are formed on the first layer electrode 3a and the second layer electrode 3b. A light-shielding film (covering layer) 7 made of tungsten (W) having a sufficient thickness capable of embedding the transfer electrodes 3a and 3b is formed on the silicon oxide films 5a and 5b. The tungsten (W) The light shielding film 7 made of has an opening on the photoelectric conversion unit 30. Thus, an optical waveguide is configured. The opening is formed by planarizing the light shielding film 7 and then selectively removing it by anisotropic etching. The opening is formed by penetrating the light shielding film 7 and surrounded by an inner wall surface K substantially perpendicular to the substrate surface of the semiconductor substrate 10. The thickness of the light shielding film 7 at the position of the raised silicon oxide film 5b above the transfer electrodes 3a and 3b is preferably not less than ½ of the opening width of the opening of the light shielding film. Thereby, the condensing function of an optical waveguide is exhibited reliably.

  As indicated by an arrow in FIG. 3, the incident light L is reflected by the inner wall surface K in the opening provided in the light shielding film 7, guided downward, and reaches the photoelectric conversion unit 30. Since there is no stepped portion on the side surface of the optical waveguide, incident light is guided downward without irregular reflection. As a result, incident light that would otherwise be stray light becomes effective light, and light collection efficiency is improved. Therefore, even if the inner lens is not provided, the light collection efficiency can be improved as in the case where the inner lens is provided. In addition, compared with the case of forming an intralayer lens, the optical waveguide can be easily formed by combining a CVD technique and an anisotropic etching technique such as RIE. Facilitated. In addition, when forming an in-layer lens, there is a concern about the generation of voids due to lens shape defects and embedding defects along with the miniaturization of the device. Does not occur.

In FIG. 3, an oxide film (CVDSiO ₂ film) 8 as an interlayer insulating film is formed on the light shielding film 7 constituting the optical waveguide, and a silicon nitride film (SiN film) 9 as a passivation film is formed thereon. Has been.

  Further, a planarizing layer 24 made of an organic film or the like is formed thereon, and a color filter 50 is formed thereon. A microlens (on-chip lens) 60 is formed on the color filter via a planarizing film (organic film) 70.

Next, a method for manufacturing the solid-state imaging device of FIG. 3 will be described with reference to FIGS.
FIG. 4 is a cross-sectional view in the first manufacturing process of the solid-state imaging device of FIG.
First, as shown in FIG. 4, an impurity (B) for forming an overdrain buffer layer 13 made of a p-type semiconductor layer is ion-implanted in an n-type semiconductor substrate 10, and a p-well 12 is formed. Impurity (B) for ion implantation. Subsequently, the p-type layer 32 and the n-type layer 31 are formed in the photoelectric conversion unit 30, the n-type layer 111 and the p-type layer 113 are formed in the charge transfer unit 80, and the p-type channel stop region 11 is formed. Form.

  Subsequently, a laminated structure (ONO) film including a bottom oxide film 2a made of a silicon oxide (SiO) film, a silicon nitride (SiN) film 2b, and a top oxide film 2c made of a silicon oxide (SiO) film is formed. . This laminated structure film becomes a gate insulating film.

  Further, in the charge transfer section 80, a first layer electrode 3a and a second layer electrode 3b made of doped polysilicon are formed on the gate oxide film 2 (2a, 2b, 2c). Between the first layer electrode 3a and the second layer electrode 3b, an interelectrode insulating film 4 composed of a silicon oxide film 4a and an HTO film 4b is formed. Thereby, a charge transfer electrode is formed.

  Subsequently, a first oxide film 5a is formed on the charge transfer electrode. Then, a silicon nitride film (SiN film) 6 is formed on the gate oxide film 2 on the photoelectric conversion unit 30, and then a second oxide film 5b is formed. In this way, the device structure shown in FIG. 4 is formed.

FIG. 5 is a cross-sectional view of the solid-state imaging device of FIG. 3 in the second step.
As shown in FIG. 5, the second oxide film 5b has a thickness sufficient to embed the first layer and the second layer electrodes (3a, 3b) constituting the transfer electrode (in other words, Tungsten (W) having a film thickness that can be flattened later is deposited to form a light shielding film 7. Subsequently, the light shielding film 7 is planarized by a planarization technique such as CMP (Chemical Mechanical Etching) or etch back.

6 is a cross-sectional view of the solid-state imaging device of FIG. 3 in a third step.
Subsequently, a part of the light shielding film 7 made of tungsten (W) is selectively removed by a photolithography technique, and an opening is formed on the photoelectric conversion unit 30. For selective removal of the light shielding film 7, anisotropic etching such as RIE (reactive ion etching) is used. Thereby, the inner wall surface K of the light shielding film 7 made of tungsten (W) becomes substantially vertical, and this inner wall surface K serves as a reflector for guiding incident light coming from above the device to the lower photoelectric conversion unit 30. Function. Thereby, an optical waveguide is formed. Since this waveguide exists, incident light that would otherwise be stray light becomes effective light, and light collection efficiency is improved. Therefore, even if the inner lens is not provided, the light collection efficiency can be improved as in the case where the inner lens is provided. In addition, compared with the case of forming an intralayer lens, the optical waveguide can be easily formed by combining a CVD technique and an anisotropic etching technique such as RIE. Facilitated.

FIG. 7 is a cross-sectional view of the solid-state imaging device of FIG. 3 in a fourth step.
Subsequently, an oxide film (CVD SiO ₂ film) 8 as an interlayer insulating film is formed on the light shielding film 7 constituting the optical waveguide, and a silicon nitride film (SiN film) 9 as a passivation film is further formed thereon. Form.

FIG. 8 is a cross-sectional view of the solid-state imaging device of FIG. 3 in the fifth step.
Subsequently, a planarizing layer 24 made of an organic film or the like is formed on the silicon nitride film (SiN film) 9 as a passivation film.

  Then, as shown in FIG. 3, the color filter 50 is formed on the planarization layer 24, and the microlens (on-chip lens) 60 is formed on the color filter via the planarization film 70. . In this way, the solid-state imaging device of FIG. 3 is completed.

  As described above, according to the solid-state imaging device 100 of the present embodiment, the incident light L is reflected by the inner wall surface K in the opening provided in the light shielding film 7 and guided downward to the photoelectric conversion unit 30. Therefore, incident light is efficiently guided to the lower photoelectric conversion unit 30 without being irregularly reflected. Thereby, the improvement of the condensing efficiency similar to when an intralayer lens is provided is achieved. Compared with the process of forming the inner lens, the optical waveguide can be easily formed by combining the CVD technique and the anisotropic etching technique such as RIE. It is simplified and the cost is reduced. In addition, voids are not generated in the layer, and a solid-state imaging device having a high-quality layer structure can be obtained.

In the above example, the light shielding film 7 is formed and then the opening is formed at the position of the photoelectric conversion unit 30 and the oxide film 8 is formed in the opening. However, the present invention is not limited to this method. The optical waveguide may be formed as follows.
That is, as shown in a cross-sectional view of a first modification of the optical waveguide manufacturing method in FIG. 9, a tungsten light shielding film 140 covering the charge transfer portion 80 is formed before the light shielding film 7 is formed, and an oxide film is formed thereon. 8 may be formed and planarized, and then an opening may be formed on the region of the charge transfer portion 80 and a tungsten plug serving as the light shielding film 7 may be embedded in the opening. According to this method, it is only necessary to make a minor change to the normal process without adding a special step to the formation of the optical waveguide.
As another method, as shown in a cross-sectional view of a second modification of the optical waveguide manufacturing method in FIG. 10, the oxide film 8 is formed and planarized before the light shielding film 7 is formed, and then the openings are formed. It is also possible to form and bury a tungsten plug serving as the light shielding film 7 in the opening.

(Second Embodiment)
Next, a second embodiment of the solid-state imaging device according to the present invention will be described.
FIG. 11 is a cross-sectional view showing an example in which an optical waveguide is constituted by a composite film in which a light-transmitting film and a light-shielding material film provided on the surface thereof are combined.
The basic structure of the solid-state imaging device in FIG. 11 is the same as that of the solid-state imaging device in FIG. 3, but the configuration of the optical waveguide is different. That is, in the solid-state imaging device of FIG. 3, a single film made of tungsten (W) is processed to form an optical waveguide. However, in the solid-state imaging device of FIG. An optical waveguide is constituted by a composite film in combination with the provided light shielding material film.

  In the solid-state imaging device of this embodiment, an oxide film (for example, a plasma TEOS oxide film) 110 having a thickness capable of embedding the transfer electrode is formed on the second oxide film 5b provided on the transfer electrode. Then, an opening is formed by selective etching, and a light-shielding material film (reflective material film) 120 made of a metal (for example, tungsten or aluminum) is formed on the upper surface and inner wall surface of the oxide film 110. An optical waveguide is formed by a composite film composed of the light shielding material film 120. As a result, the same effect as in the above-described embodiment can be obtained.

Hereinafter, a method for manufacturing an optical waveguide using a composite film in the solid-state imaging device of FIG. 11 will be described with reference to FIGS.
As shown in FIG. 12A, a metal film (reflective material film) 120a made of aluminum (Al) is formed on the oxide film 110, a resist 19 is formed thereon, and then the resist 19 is formed. Pattern.

  Next, as shown in FIG. 12B, the oxide film 110 is etched. Subsequently, as shown in FIG. 12C, after removing the resist 19, a metal film 120 b made of Al is formed on the metal film 120 a and the inner wall surface of the oxide film 110.

  Next, as shown in FIG. 12D, the entire upper metal film 120b is etched by RIE. As a result, the upper metal film 120b remains only on the inner wall surface of the oxide film 110, and the others are removed. The metal film 120 b formed on the inner wall surface of the oxide film 110 is connected (connected) to the metal film 120 a provided on the upper surface of the oxide film 110. In this way, a reflective material film made of the metal film 120 is formed on the surface of the oxide film 110.

  The metal film 120a functions as a light shielding material, and the metal film 120b functions as a reflective material for guiding incident light downward. In this way, an optical waveguide as shown in the solid-state imaging device of FIG. 11 is formed. An advantage of forming the optical waveguide using the composite film is that the thick oxide film 110 can be easily formed and processed.

(Third embodiment)
Next, a third embodiment of the solid-state imaging device according to the present invention will be described.
FIG. 13 is a cross-sectional view showing a structure in which a light-shielding film for preventing smear is further formed under an optical waveguide made of a light-shielding film.
The basic structure of the solid-state imaging device of FIG. 13 is the same as that described in the above embodiment. That is, silicon oxide films 5a and 5b are formed on the first layer electrode 3a and the second layer electrode 3b. A light-shielding film (covering layer) 7 made of tungsten (W) having a sufficient thickness capable of embedding the transfer electrodes 3a and 3b is formed on the silicon oxide films 5a and 5b. The tungsten (W) The light shielding film 7 made of has an opening on the photoelectric conversion unit 30.
However, in the solid-state imaging device shown in FIG. 13, a light-shielding film 150 for preventing smear is formed under an optical waveguide made of the light-shielding film (tungsten film) 7, and a thin oxide film is formed on the light-shielding film (tungsten film) 150. 160 is formed, and a CVD oxide film 8 is formed on the oxide film 160. In this respect, the configuration is different from the solid-state imaging device shown in FIG.

  According to the solid-state imaging device of FIG. 13, a light shielding film (tungsten film) 150 is formed below the light shielding film (tungsten film) 7 serving as an optical waveguide so as to cover the charge transfer portion including the transfer electrode. Therefore, it is possible to reliably prevent the occurrence of smear due to the wraparound of incident light. That is, when the thickness of the translucent gate insulating film 2 or the oxide film 5b provided on the photoelectric conversion unit 30 of the semiconductor substrate 10 is increased, the light propagating through the optical waveguide passes through the insulating film obliquely. As a result, the charge transfer unit 80 may go around. Therefore, the light that passes around is surely blocked by the lower light shielding film 150. This reliably prevents the occurrence of smear.

  14 and 15 are cross-sectional views of the device showing a part of the manufacturing process of the solid-state imaging device shown in FIG. 13 (step of forming a light shielding film under the optical waveguide). In FIG. 14 and FIG. 15, the same reference numerals are assigned to the same parts as those in the above-mentioned drawings.

  After the process of FIG. 4 described above, as shown in FIG. 14, a light shielding film 150 made of tungsten (W) is formed on the oxide film 5b. Subsequently, as shown in FIG. 15, an oxide film 160 is formed on the light shielding film 150. Thereafter, the solid-state imaging device of FIG. 13 is formed through the same manufacturing process as in the above-described embodiment.

(Fourth embodiment)
Next, a fourth embodiment of the solid-state imaging device according to the present invention will be described.
In this embodiment, an in-layer lens is further formed between the microlens (on-chip lens) and the optical waveguide. The present invention can replace the inner lens with an optical waveguide, but does not exclude the use of the inner lens. In other words, even if the light collection characteristics of the inner lens of the optical waveguide are slightly lowered, by providing the optical waveguide below the inner lens, light that would otherwise be stray light is also guided to the photoelectric conversion unit, Condensation efficiency is improved.

  FIG. 16 is a cross-sectional view showing a structure in which an intralayer lens is formed between a microlens (on-chip lens) and an optical waveguide.

As shown in the drawing, in the solid-state imaging device of the present embodiment, an in-layer lens 22 is formed between a microlens (on-chip lens) 60 and an optical waveguide (light shielding film 7 made of tungsten).
The in-layer lens is configured by an upwardly convex lens 22 (made of SiN) on the upper side of the BPSG film 20 that covers the opening of the light shielding film 7.

  As described above, according to the solid-state imaging device of FIG. 16, incident light can be more efficiently guided to the photoelectric conversion unit 30 by the synergistic effect of the microlens (on-chip lens) 60, the in-layer lens 22, and the optical waveguide. it can.

  In the above description of the embodiment, a CCD solid-state image sensor has been described as an example. However, the present invention can be similarly applied to a MOS solid-state image sensor. Further, the arrangement of the photosensors 30 is not limited to that shown in FIG. 2, but may be a square lattice arrangement, for example.

  As described above, according to the present invention, by providing the optical waveguide, the light condensed by the microlens can be reliably guided to the photoelectric conversion unit by the optical waveguide, and thus the light collection efficiency is ensured. Further, according to the present invention, it is possible to eliminate the problem of the in-layer lens that becomes apparent with the miniaturization of the element, and to effectively improve the light collection efficiency of the solid-state imaging element.

It is a plane schematic diagram of the solid-state image sensor concerning the present invention. FIG. 2 is an enlarged plan view of a pixel portion of the solid-state imaging device shown in FIG. It is sectional drawing which follows the AA line in an example of the solid-state image sensor of this invention of FIG. It is sectional drawing in the 1st manufacturing process for demonstrating the manufacturing method of the solid-state image sensor of FIG. It is sectional drawing in the 2nd manufacturing process for demonstrating the manufacturing method of the solid-state image sensor of FIG. It is sectional drawing in the 3rd manufacturing process for demonstrating the manufacturing method of the solid-state image sensor of FIG. It is sectional drawing in the 4th manufacturing process for demonstrating the manufacturing method of the solid-state image sensor of FIG. It is sectional drawing in the 5th process of the solid-state image sensor of FIG. It is sectional drawing showing the 1st modification of the manufacturing method of an optical waveguide. It is sectional drawing showing the 2nd modification of the manufacturing method of an optical waveguide. It is sectional drawing which shows the structure of the other example (Example which comprises an optical waveguide with the composite film which combined the translucent film | membrane and the light-shielding material film | membrane provided in the surface) of the solid-state image sensor of this invention. (A)-(e) is sectional drawing for every process for demonstrating the manufacturing method of the optical waveguide which uses the composite film in the solid-state image sensor of FIG. It is sectional drawing which shows the structure of the other example (example which further formed the light shielding film for smear prevention under the optical waveguide consisting of a light shielding film) of the solid-state image sensor of this invention. It is sectional drawing of the device which extracts and shows a part (process of forming a light shielding film under an optical waveguide) of the manufacturing process of the solid-state image sensor of FIG. It is sectional drawing of the device which extracts and shows a part (process of forming a light shielding film under an optical waveguide) of the manufacturing process of the solid-state image sensor of FIG. It is sectional drawing which shows the structure of the other example (example which formed the inner lens between the micro lens (on-chip lens) and the optical waveguide) of the solid-state image sensor of this invention. It is sectional drawing which shows the structure of the conventional CCD solid-state image sensor.

Explanation of symbols

2 (2a to 2c) Gate oxide film 3a, 3b Transfer electrode 4 Interelectrode insulating film 5a, 5b Oxide film (silicon oxide film)
7 Light-shielding film 8 Oxide film 10 Semiconductor substrate 11 Channel stop region 12 Light-shielding material film 13 Overdrain buffer layer 15 Vertical transfer path 30 Photodiode (photoelectric conversion unit)
41 Output Amplifier 43 Light-Receiving Area 47 Image Sensor Forming Area 50 Color Filter 70 Passivation Film 80 Charge Transfer Unit 100 Solid-State Image Sensor

Claims (10)

A solid-state imaging device having a photoelectric conversion unit, a charge transfer unit that transfers charges generated by the photoelectric conversion unit, and an optical waveguide that guides incident light to the photoelectric conversion unit,
The optical waveguide covers the charge transfer portion and has a cover layer having an opening formed on the inner wall surface of the photoelectric conversion portion substantially vertically, and a translucent material portion formed inside the opening. A solid-state imaging device, wherein an inner wall surface and an upper surface of the coating layer have a light shielding property. The solid-state imaging device according to claim 1,
The solid-state imaging device, wherein the coating layer is a light shielding film made of a metal material. The solid-state imaging device according to claim 1,
The optical waveguide is provided with a coating layer made of a light-shielding material on the photoelectric conversion unit and the charge transfer unit, and then planarized on the coating layer to planarize the upper surface, and the photoelectric conversion of the coating layer A solid-state imaging device, wherein the solid-state imaging device is formed through a step of removing a portion located above the portion and providing an opening penetrating the coating layer. The solid-state imaging device according to claim 1,
The solid-state imaging device, wherein the coating layer constituting the optical waveguide includes an opening penetrating the coating layer, and a light-shielding material film provided on the inner wall surface and the upper surface of the opening. The solid-state imaging device according to claim 1,
The optical waveguide is provided with a coating layer on the photoelectric conversion unit and the charge transfer unit, and then planarizes the coating layer to planarize the top surface, and the surface of the coating layer is made of a light-shielding material. And forming an opening penetrating the first light-shielding layer by removing a portion of the coating layer located above the photoelectric conversion portion, and accompanying the formation of the opening portion, the first light-shielding layer is formed. A solid-state imaging device, which is formed through a step of providing a second light-shielding layer made of a light-shielding material and connected to the first light-shielding layer on an inner wall surface of the covering layer. It is a solid-state image sensing device according to any one of claims 1 to 5,
A solid-state imaging device, wherein a light-shielding film made of a light-shielding material is formed below the film constituting the optical waveguide to cover the charge transfer portion. The solid-state image sensor according to any one of claims 1 to 6,
A solid-state imaging device, wherein a microlens for condensing light toward the optical waveguide is provided above the optical waveguide. The solid-state imaging device according to claim 7,
A solid-state imaging device, wherein an intralayer lens is provided between the microlens and the optical waveguide. A method of manufacturing a solid-state imaging device, comprising: a photoelectric conversion unit; a charge transfer unit that transfers charges generated by the photoelectric conversion unit; and an optical waveguide that guides incident light to the photoelectric conversion unit,
A first step of forming the photoelectric conversion part in a semiconductor substrate;
A second step of forming a charge transfer portion including a charge transfer electrode in and on the semiconductor substrate;
After providing a coating layer made of a light-shielding material on the photoelectric conversion unit and the charge transfer unit, the coating layer is subjected to a planarization process to planarize the upper surface, and the coating layer is positioned above the photoelectric conversion unit. A third step of forming the optical waveguide by removing an area to be removed and providing an opening penetrating the coating layer;
The manufacturing method of the solid-state image sensor characterized by including. A method of manufacturing a solid-state imaging device, comprising: a photoelectric conversion unit; a charge transfer unit that transfers charges generated by the photoelectric conversion unit; and an optical waveguide that guides incident light to the photoelectric conversion unit,
A first step of forming the photoelectric conversion part in a semiconductor substrate;
A second step of forming a charge transfer portion including a charge transfer electrode in and on the semiconductor substrate;
After providing a coating layer on the photoelectric conversion unit and the charge transfer unit, the coating layer is planarized to flatten the top surface, and a first light shielding layer made of a light shielding material is formed on the surface of the coating layer. And forming an opening penetrating the first light-shielding layer by removing a portion of the covering layer located above the photoelectric conversion portion, and the covering layer generated along with the formation of the opening portion A third step of forming the optical waveguide by providing a second light-shielding layer made of a light-shielding material and connected to the first light-shielding layer on the inner wall surface;
The manufacturing method of the solid-state image sensor characterized by including.

Images