JP2008147397A - Solid-state imaging device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid-state imaging device and its manufacturing method capable of preventing the occurrence of an etching residue without an etching time increased when a level difference adjustment film is formed. <P>SOLUTION: The solid-state imaging device related to this invention includes a semiconductor substrate 101; a photoelectric converting unit 102 formed on the semiconductor substrate 101 and converting a light to a signal charge; an electrode 111 for reading the signal charge converted by the photoelectric converting unit 102; a first insulating film 114 formed over the photoelectric converting unit 102 and the electrode 111, and having a convex curve shape facing downward on the upper surface; a level difference adjustment film 115 formed over an electrode 111 through the first insulating film 114; a second insulating film 116 formed over the level difference adjustment film 115 and the first insulating film 114; and a third insulating film 117 formed on the second insulating film 116, composed of a material having a refractive index different from that of the material for comprising the second insulating film 116, and having a microlens shape contacting with the second insulating film 116 convex downward. <P>COPYRIGHT: (C)2008,JPO&INPIT

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 in-layer lens and a manufacturing method thereof.

  A so-called solid-state imaging device having a charge transfer unit for transferring charges photoelectrically converted by a light receiving unit is used in various image input devices such as a video camera, a digital still camera, and a facsimile.

  In recent years, in particular, video cameras and digital still cameras are strongly required to have high resolution and compactness. In order to meet this demand, a solid-state imaging device having a large number of pixels (increasing the number of pixels) is required. However, when the number of pixels is simply increased, the optical size of the solid-state imaging device becomes large and cannot be made compact. Therefore, it is required to increase the number of pixels while maintaining the optical size. That is, it is necessary to reduce the pixel size.

  However, when the pixel size is reduced, the amount of light incident on the unit pixel decreases. Thereby, the subject that the sensitivity of the light-receiving part of each pixel falls arises. In order to prevent this problem, a method of improving the light collection efficiency in each pixel is known in order to prevent a decrease in sensitivity characteristics due to the miniaturization of the pixel size (see, for example, Patent Document 1).

  FIG. 11 is a diagram showing a cross-sectional structure of a conventional solid-state imaging device described in Patent Document 1. FIG. 11A is a diagram showing a horizontal sectional structure of a conventional solid-state imaging device. FIG. 11B is a diagram illustrating a vertical sectional structure of a conventional solid-state imaging device.

  A conventional solid-state imaging device 500 shown in FIG. 11 includes a semiconductor substrate 501, a light receiving unit 502, a vertical transfer unit 503, insulating films 504, 509 and 510, a vertical transfer electrode 505, a metal film 506, and an etching stopper. 507, a step adjustment film 508, a protective film 511, a color filter 512, and a microlens 513.

  The light receiving unit 502 converts the received incident light into a signal charge corresponding to the amount of light and accumulates it. The vertical transfer unit 503 transfers the signal charge photoelectrically converted by the light receiving unit 502 in the vertical direction. The light receiving unit 502 and the vertical transfer unit 503 are formed on the semiconductor substrate 101.

  The vertical transfer electrode 505 is an electrode for reading the signal charge converted by the light receiving unit 502. The vertical transfer electrode 505 is formed on the vertical transfer unit 503 via the insulating film 504. The metal film 506 is formed above the vertical transfer electrode 505 via an insulating film 504. The step adjustment film 508 is formed above the metal film 506 with an etching stopper 507 interposed therebetween.

The insulating film 509 and the insulating film 510 are formed using materials having different refractive indexes. The interface between the insulating film 509 and the insulating film 510 is convex downward. Thus, an in-layer lens is formed by the insulating film 509 and the insulating film 510. Further, the conventional solid-state imaging device 500 includes a step adjustment film 508. By controlling the width and height of the step adjustment film 508, the shape of the recess of the insulating film 509 formed by heat flow is optimized. Thereby, the shape of the in-layer lens can be optimized, and the light collection efficiency of the incident light with respect to the light receiving unit 502 can be improved.
JP 2002-353428 A

  However, in the conventional solid-state imaging device 500, the vertical transfer electrode 505 and the metal film 506 are formed around the light receiving unit 502. As a result, there is a steep step between the region where the metal film 506 is formed and the region above the light receiving portion 502 (the region where the vertical transfer electrode 505 and the metal film 506 are not formed).

  On the other hand, a method for forming the step adjustment film 508 is, for example, forming a film on the entire surface of the etching stopper 507 by sputtering or CVD (Chemical Vapor Deposition) and then performing etching to form a step. A method of forming a pattern of the adjustment film 508 is used.

  However, there is a problem that the vicinity of the bottom of the metal film 506 on the light receiving portion 502 has a steep step, and the film that has entered into a narrow depression cannot be completely removed during etching, resulting in a residue 520. This residue 520 causes image deterioration of the solid-state imaging device.

On the other hand, a method of performing etching for a long time to remove the residue 520 is also conceivable.
However, when etching is performed for a long time, the influence of plasma irradiation on the semiconductor substrate is increased, which causes a new problem that a dark current that causes image deterioration of the solid-state imaging device increases. That is, a method of performing etching for a long time is not preferable.

  Therefore, an object of the present invention is to provide a solid-state imaging device and a method for manufacturing the same that prevent generation of etching residues when forming a step adjustment film without increasing the etching time.

  In order to achieve the above object, a solid-state imaging device according to the present invention includes a semiconductor substrate, a photoelectric conversion unit that is formed on the semiconductor substrate and converts light into signal charge, and a signal charge converted by the photoelectric conversion unit. A first insulating film formed above the photoelectric conversion unit and the electrode and having a downward convex curved surface shape on the upper surface, and the first insulating film above the electrode. A step-adjusting film formed on the second insulating film, a second insulating film formed above the step-adjusting film and the first insulating film, and the second insulating film formed on the second insulating film. A third insulating film having a microlens shape which is made of a material having a refractive index different from that of the material forming the film and is in contact with the second insulating film convex downward.

  According to this configuration, by using the step adjustment film, the in-layer lens constituted by the second insulating film and the third insulating film can be formed into an appropriate in-layer lens shape. Furthermore, the first insulating film has a downward convex curve shape. As a result, when the step adjustment film is formed by etching, the underlying shape of the film to be etched (upper surface of the first insulating film) is a smooth curved surface. Can prevent it.

  That is, the solid-state imaging device according to the present invention can prevent the generation of etching residues when forming the step adjustment film without increasing the etching time. Furthermore, since the generation of residues during etching can be prevented, it is possible to prevent problems such as damage to the device due to excessive over-etching, that is, dark current. Therefore, a high quality solid-state imaging device can be realized.

  The solid-state imaging device may further include a light shielding film formed above the electrode, and the first insulating film may be formed above the photoelectric conversion unit and the light shielding film.

  According to this configuration, the light shielding film can reduce the invasion of stray light into regions other than the photoelectric conversion unit, such as regions where electrodes are formed. Thereby, a smear characteristic can be improved.

Further, the step adjustment film may be made of metal.
According to this configuration, the step adjustment film prevents light from entering a region other than the photoelectric conversion unit, such as a region where an electrode is formed. That is, since the step adjustment film has an antireflection function, it is possible to reduce the invasion of stray light to a region other than the photoelectric conversion unit. Thereby, a smear characteristic can be improved. In addition, since it is not necessary to form another antireflection film in a region where the electrode is formed, the structure of the solid-state imaging device can be simplified.

The metal may be a refractory metal.
The solid-state imaging device further reads a plurality of photoelectric conversion units arranged in a matrix including the photoelectric conversion units, and signal charges converted by the plurality of photoelectric conversion units arranged in each column. A plurality of electrodes including the electrode for, the light shielding film is arranged in a stripe shape in a column direction with respect to the plurality of photoelectric conversion units arranged in a matrix, and above the plurality of electrodes It may be arranged.

  According to this configuration, the step adjustment film is formed on the light shielding film in the cross section in the row direction of the photoelectric conversion unit, and the step adjustment film is formed without the light shielding film in the cross section in the column direction of the photoelectric conversion unit. Is done. Thereby, the step from the surface of the semiconductor substrate to the upper surface of the step adjustment film is different in the cross section in the row direction (horizontal direction) and the column direction (vertical direction). Specifically, the vertical step is lower than the horizontal step. Therefore, when the vertical width of the photoelectric conversion portion is larger than the horizontal width (when the aspect ratio of the photoelectric conversion portion deviates from 1), the curvature of the upper surface of the second insulating film is appropriate in the vertical cross section. It is possible to prevent the shape from having a steep slope. Thereby, it can prevent that the condensing property of the inner lens comprised by the 2nd insulating film and the 3rd insulating film falls.

  That is, the solid-state imaging device according to the present invention has appropriate curvatures independently in the horizontal and vertical cross sections due to the difference in level difference in addition to the thickness of the step adjustment film and the line width of the lattice. It can be made into a shape. In other words, the solid-state imaging device according to the present invention can form an in-layer lens having a higher degree of design freedom than a conventional solid-state imaging device.

  Further, the curvature of the convex microlens shape of the third insulating film may be larger than the curvature of the convex curved surface shape of the first insulating film.

  According to this configuration, the shape controllability of the microlens shape of the second insulating film can be improved. Specifically, after forming a downward convex shape with a predetermined curvature on the first insulating film, a downward convex microlens shape is formed on the downward convex shape of the first insulating film. By forming the second insulating film, the curvature of the microlens shape of the second insulating film can be easily controlled.

  Therefore, the solid-state imaging device according to the present invention can form an in-layer lens excellent in shape uniformity and shape controllability as compared with a conventional solid-state imaging device. In other words, the solid-state imaging device according to the present invention can uniformly form an intra-layer lens having a higher degree of design freedom than a conventional solid-state imaging device.

  The first insulating film and the second insulating film may be formed of materials having different refractive indexes.

  According to this configuration, the lens function can be imparted to the downward convex curved surface shape of the first insulating film. Thereby, the condensing efficiency of incident light to the photoelectric conversion unit can be improved.

  The manufacturing method according to the present invention is a method for manufacturing a solid-state imaging device, wherein a first step of forming a photoelectric conversion unit for converting light into signal charges on a semiconductor substrate is converted by the photoelectric conversion unit. A second step of forming an electrode for reading the signal charge, and a third step of forming a first insulating film having a downward convex curved surface on the upper surface of the photoelectric conversion portion and the electrode. And a fourth step of forming a step adjusting film on the first insulating film by etching, and a microlens shape convex downward on the upper surface on the step adjusting film and the first insulating film. And a fifth step of forming a second insulating film having a third refractive index and a material having a refractive index different from that of the second insulating film so as to embed a microlens shape of the second insulating film. Sixth step of forming an insulating film Including the.

  According to this, by using the step adjustment film, the intra-layer lens constituted by the second insulating film and the third insulating film can be formed into an appropriate intra-layer lens shape. Furthermore, the first insulating film is formed on the photoelectric conversion portion and the electrode using a material having flow properties. Thereby, the first insulating film can have a smooth surface shape. Therefore, when the step adjustment film is formed by etching in the fourth step, since the base shape of the film to be etched is a smooth curved surface, it is possible to prevent a fragment of the film to be etched from becoming a residue and causing a pixel defect. .

  That is, the manufacturing method of the solid-state imaging device according to the present invention can prevent the generation of etching residue when forming the step adjustment film without increasing the etching time.

  Furthermore, since the generation of residues during etching can be prevented, it is possible to prevent problems such as damage to the device due to excessive over-etching, that is, dark current.

  Therefore, the solid-state imaging device manufacturing method according to the present invention can manufacture a high-quality solid-state imaging device.

  The present invention can provide a solid-state imaging device and a method for manufacturing the same that prevent the generation of etching residues when forming the step adjustment film without increasing the etching time.

  Embodiments of a solid-state imaging device according to the present invention will be described below in detail with reference to the drawings.

  The solid-state imaging device according to the present invention includes a downwardly convex in-layer lens composed of two insulating films made of materials having different refractive indexes. In addition, an insulating film having a convex curved surface shape is provided below the two insulating films constituting the in-layer lens. As a result, when the step adjustment film is formed by etching, the base shape of the film to be etched is a smooth curved surface, so that it is possible to prevent generation of residues when the step adjustment film is etched.

First, the configuration of the solid-state imaging device according to the embodiment of the present invention will be described.
FIG. 1 is a plan view showing a configuration of a solid-state imaging device according to an embodiment of the present invention.

  As shown in FIG. 1, a solid-state imaging device 100 according to an embodiment of the present invention is a CCD solid-state imaging device. The solid-state imaging device 100 includes a semiconductor substrate 101, a plurality of light receiving units 102, a plurality of vertical transfer units 103, a horizontal transfer unit 104, and an amplifier unit 105.

The semiconductor substrate 101 is, for example, a Si substrate.
The plurality of light receiving units 102 are arranged in a matrix on the semiconductor substrate 101. The plurality of light receiving units 102 convert the received incident light into signal charges corresponding to the amount of light, and accumulate them.

  The plurality of vertical transfer units 103 are arranged for the plurality of light receiving units 102 in each column. Each vertical transfer unit 103 transfers the signal charge photoelectrically converted by the light receiving units 102 in each column in the vertical direction. For example, the vertical transfer unit 103 has a buried channel configuration. Each vertical transfer unit 103 includes a plurality of vertical transfer electrodes 111 (not shown in FIG. 1) that drive vertical transfer of signal charges.

The horizontal transfer unit 104 transfers the signal charges transferred by the plurality of vertical transfer units 103 in the horizontal direction. For example, the horizontal transfer unit 104 has a buried channel configuration. The horizontal transfer unit 104 includes a plurality of horizontal transfer electrodes (not shown in FIG. 1) that drive the transfer of signal charges in the horizontal direction.

  The amplifier unit 105 converts the signal charge horizontally transferred by the horizontal transfer unit 104 into a voltage and outputs the voltage.

  FIG. 2 is a diagram showing a cross-sectional structure of the solid-state imaging device 100 shown in FIG. 2A is a diagram illustrating a horizontal sectional structure of the solid-state imaging device 100, and is a diagram illustrating a sectional structure taken along line A0-A1 in FIG. 2B is a diagram illustrating a cross section in the vertical direction of the solid-state imaging device 100, and is a diagram illustrating a cross-sectional structure taken along B0-B1 in FIG.

  As shown in FIG. 2, the light receiving unit 102 and the vertical transfer unit 103 are formed on the semiconductor substrate 101. The solid-state imaging device 100 further includes insulating films 110, 112, 114, 116, and 117, a vertical transfer electrode 111, metal films 113 and 115, a protective film 118, a color filter 119, and a microlens 120. .

The insulating film 110 is formed on the surface of the semiconductor substrate 101 on which the light receiving unit 102 and the vertical transfer unit 103 are formed. For example, the insulating film 110 is an oxide film (SiO ₂ or the like).

  The vertical transfer electrode 111 is an electrode for reading the signal charge converted by the light receiving unit 102. The vertical transfer electrode 111 is formed on the vertical transfer unit 103 via the insulating film 110. That is, the vertical transfer electrode 111 is formed around the light receiving portion 102 on the insulating film 110. For example, the vertical transfer electrode 111 is made of polysilicon.

The insulating film 112 is formed on the vertical transfer electrode 111. For example, the insulating film 112 is an oxide film (SiO ₂ or the like).

  The metal film 113 is formed above the vertical transfer electrode 111 via the insulating film 112. The metal film 113 functions as a light shielding film for the vertical transfer electrode 111. For example, the metal film 113 is arranged in a stripe shape at a position facing the vertical transfer unit 103.

  FIG. 3A is a plan view showing an arrangement example of the metal film 113. As shown in FIG. 3A, the plurality of metal films 113 are arranged in stripes in the column direction (vertical direction in FIG. 4) with respect to the plurality of light receiving units 102 arranged in a matrix, and a plurality of metal films 113 are arranged. It is disposed above the vertical transfer electrode 111 formed on the vertical transfer unit 103. For example, the metal film 113 is made of tungsten, which is a refractory metal. In FIG. 3A, the metal film 113 is formed on the vertical transfer unit 103, but may be further formed on the horizontal transfer unit 104.

  Further, as shown in FIG. 2, the insulating film 114 is formed on the insulating film 112 and the metal film 113. The insulating film 114 has a convex curved surface in the downward direction (in the direction of the semiconductor substrate 101) on the upper surface. The insulating film 114 is made of a flowable material, and the upper and lower surfaces have a smooth curved surface. For example, the insulating film 114 is made of BPSG (Phosphorus silicate glass) or the like.

  Note that the insulating film 114 also has a function as an etching stopper film with respect to an etching process when forming the metal film 115 described later.

  The metal film 115 is formed on the insulating film 114. The metal film 115 is formed above the metal film 113 with an insulating film 114 interposed therebetween. The metal film 115 has a function of shielding light between the light receiving portions 102 adjacent in the vertical direction so as to have an opening above the light receiving portion 102. In addition, the metal film 115 functions as a step adjustment film when forming an intralayer lens composed of the insulating film 116 and the insulating film 117. For example, the metal film 115 is made of tungsten, which is a refractory metal.

  FIG. 3B is a plan view showing an arrangement example of the metal film 115. As shown in FIG. 3B, the metal film 115 is arranged in a lattice shape at a position facing the vertical transfer electrode 111. That is, the metal film 115 is formed other than above the metal film 113. In FIG. 3B, the metal film 115 is formed on the vertical transfer unit 103, but may be further formed on the horizontal transfer unit 104.

  Further, as shown in FIG. 2, the insulating film 116 is formed on the insulating film 114 and the metal film 115. The insulating film 116 has a microlens shape having a convex curved shape in the downward direction (in the direction of the semiconductor substrate 101) on the upper surface. Further, the curvature of the convex microlens shape included in the insulating film 116 is larger than the curvature of the convex curved surface shape included in the insulating film 114. The insulating film 116 is made of a flowable material, and the top surface has a smooth curved surface. For example, the insulating film 116 is made of BPSG or the like, and is formed by a CVD (Chemical Vapor Deposition) method.

  The insulating film 117 is formed on the insulating film 116. The insulating film 117 is formed so as to embed the microlens shape on the upper surface of the insulating film 116. The insulating film 117 is made of a material having a refractive index larger than that of the insulating film 116. For example, the insulating film 117 is a nitride film (SiN or the like). The shape of the lower surface of the insulating film 117 is a downwardly convex microlens shape, and the microlens shape is in contact with the insulating film 116.

  That is, the insulating film 116 and the insulating film 117 form an inner lens. The shape of the intralayer lens is convex downward (in the direction of the semiconductor substrate 101).

  Note that the insulating film 117 may be formed of a material having a refractive index smaller than that of the insulating film 116 depending on the optical characteristics of the solid-state imaging device. Even when the insulating film 117 is made of a material having a refractive index smaller than the refractive index of the insulating film 116, the shape of the lower surface of the insulating film 117 is a downwardly convex microlens shape. Function can be obtained.

  The protective film 118 is formed on the insulating film 117. For example, the protective film 118 is made of an acrylic resin or the like.

  The color filter 119 is formed on the protective film 118. For example, the color filter 119 is formed of a so-called primary color Bayer array composed of red, Green, and blue color filters.

  The microlens 120 is formed on the color filter 119. The microlens 120 is a lens (top lens) that efficiently collects incident light on the light receiving unit 102.

Next, a method for manufacturing the solid-state imaging device 100 according to the embodiment of the present invention will be described.
4-10 is a figure which shows the cross-sectional structure in the manufacture process of the solid-state imaging device 100 which concerns on embodiment of this invention. 4A to 10A are diagrams illustrating a cross-sectional structure in the horizontal direction (A0-A1 in FIG. 1) in the manufacturing process of the solid-state imaging device 100. FIG. 4B to 10B are diagrams illustrating a cross-sectional structure in the vertical direction (B0-B1 in FIG. 1) in the manufacturing process of the solid-state imaging device 100. FIG.

  First, a light receiving unit 102 that photoelectrically converts incident light and a vertical transfer unit 103 with a buried channel configuration that transfers charges photoelectrically converted by the light receiving unit 102 in the vertical direction are formed on the semiconductor substrate 101 by existing technology. . Next, the insulating film 110 is formed on the semiconductor substrate 101 by thermal oxidation. Next, a vertical transfer electrode 111 made of polysilicon for driving the vertical transfer unit 103 is formed on the insulating film 110 so as to face the vertical transfer unit 103. Next, an insulating film 112 is formed on the light receiving portion 102 and the vertical transfer electrode 111 by thermal oxidation or CVD. Next, a tungsten layer is formed on the entire surface of the insulating film 112 by a CVD method or a sputtering method. Next, etching is performed in a vertical stripe shape so that the light receiving portion 102 is opened. Thereby, the metal film 113 is formed. Through the above steps, the structure shown in FIG. 4 is formed.

  Next, BPSG or the like having flow properties is formed over the insulating film 112 and the metal film 113. As a result, the insulating film 114 is formed so that the surface irregularities have a smooth curved surface and the surface is recessed on the light receiving portion 102. Further, heat treatment is performed to solidify the insulating film 114. Through the above steps, the structure shown in FIG. 5 is formed.

  Next, a tungsten layer is formed on the entire surface of the insulating film 114 by a CVD method or a sputtering method. Through the above steps, the structure shown in FIG. 6 is formed.

Next, as shown in FIG. 7, a resist 130 is formed in a lattice shape so that the light receiving portion 102 is opened. Next, the metal film 115 is etched with a gas species 131 containing CF ₆ or SF ₆ . Next, the resist 130 remaining after the etching and the residue generated during the etching are removed to form a grid-like metal film 115 so that the light receiving portion 102 is opened. Note that the insulating film 114 functions as an etching stopper during this etching. Through the above steps, the structure shown in FIG. 8 is formed.

  Next, BPSG or the like having flow properties is formed over the insulating film 114 and the metal film 115. Thereby, an insulating film 116 having a shape along the insulating film 114 and the metal film 115 and having a surface recessed on the light receiving portion 102 is formed. Further, heat treatment is performed to solidify the insulating film 116. Through the above steps, the structure shown in FIG. 9 is formed.

  Next, an insulating film 117 is formed on the insulating film 116 by a CVD method. Note that the surface of the insulating film 117 may be planarized by CMP (Chemical Mechanical Polishing). Further, there may be irregularities having a size that does not have a great optical effect on the accuracy of planarization, specifically, about 1/10 or less of the pixel size. Through the above steps, the structure shown in FIG. 10 is formed.

  Next, the protective film 118 is formed on the insulating film 117 by spin coating acrylic resin. Next, a color filter 119 is formed on the protective film 118. Next, the microlens 120 is formed on the color filter 119. Note that the color filter 119 and the microlens 120 can be formed by an existing technique. Thus, the solid-state imaging device 100 shown in FIG. 2 is formed.

  As described above, the solid-state imaging device 100 and the manufacturing method thereof according to the embodiment of the present invention can obtain an appropriate intralayer lens shape in the horizontal direction and the vertical direction by using the metal film 115 that is the step adjustment film. it can.

  Furthermore, in the solid-state imaging device 100 according to the embodiment of the present invention, the insulating film 114 is formed above the light receiving unit 102 and on the metal film 113 using a material having flow properties. Thereby, the insulating film 114 can have a smooth surface shape. Therefore, since the base shape of the film to be etched is a smooth curved surface, when the metal film 115 is formed by etching, a fragment of the film to be etched can be prevented from becoming a residue 520 and causing a pixel defect.

  Further, since the generation of the residue 520 at the time of etching can be prevented, it is possible to prevent problems such as damage to the device due to excessive over-etching, that is, dark current. Therefore, a high quality solid-state imaging device can be realized.

  Further, in the solid-state imaging device 100 according to the embodiment of the present invention, the angled device shape generated by the vertical transfer electrode 111 and the metal film 113 is in an angleless (smooth) state by the insulating film 114. A convex microlens shape is formed in the downward direction by the metal film 115 and the insulating film 116.

  For example, after forming a downward convex shape with a predetermined curvature on the insulating film 114, an insulating film 116 having a downward convex microlens shape is formed on the downward convex shape of the insulating film 114. Thus, the curvature of the microlens shape of the insulating film 116 can be easily controlled.

  That is, by making the curvature of the microlens shape of the insulating film 116 larger than the curvature of the downward convexity of the insulating film 114, the shape controllability of the microlens shape of the insulating film 116 can be improved. .

  That is, the solid-state imaging device 100 according to the embodiment of the present invention can form an in-layer lens excellent in shape uniformity and shape controllability as compared with a conventional solid-state imaging device. In other words, the solid-state imaging device 100 according to the embodiment of the present invention can uniformly form an intra-layer lens having a higher degree of design freedom than a conventional solid-state imaging device.

  Further, in the solid-state imaging device 100 according to the embodiment of the present invention, the metal film 115 that is the step adjustment film is made of a refractory metal having excellent light shielding properties such as tungsten.

  Thereby, the invasion of stray light to the vertical transfer unit 103 can be reduced, and smear characteristics can be improved.

  Note that the metal film 115 is not necessarily made of a refractory metal having excellent light shielding properties such as tungsten. This is because the solid-state imaging device 100 according to the embodiment of the present invention includes the metal film 113 as a structure that shields light from the vertical transfer unit 103.

  In the conventional solid-state imaging device 500 shown in FIG. 11, the metal film 506 and the step adjustment film 508 are formed in a lattice shape so as to have openings on the light receiving portion 502. As a result, the steps from the surface of the semiconductor substrate 501 (etching stopper 507 on the light receiving portion 502) to the upper surface of the step adjustment film 508 are the same in the horizontal and vertical cross sections.

  Therefore, in the conventional solid-state imaging device 500, when the aspect ratio of the light receiving unit 502 deviates from 1, the ratio of the horizontal dimension on the surface of the semiconductor substrate 501 of the light receiving unit 502 to the vertical dimension is from 1. In the case of deviation, the curvature of the upper surface of the insulating film 509 at a cross section having a larger opening (for example, a cross section in the vertical direction in FIG. 11) is not appropriate and has a steep slope. Thereby, the condensing property with respect to the incident light 521 of the inner lens comprised of the insulating film 509 and the insulating film 510 is lowered.

  On the other hand, the solid-state imaging device 100 according to the embodiment of the present invention includes a metal film 113 arranged in a stripe shape in the vertical direction and a metal film 115 arranged in a grid pattern above the metal film 113.

  As a result, the steps from the surface of the semiconductor substrate 101 to the upper surface of the metal film 115 as the step adjustment film are different in the horizontal and vertical sections of the light receiving unit 102. Specifically, as shown in FIG. 2, a metal film 115 is formed above the metal film 113 in the row direction (horizontal direction) cross section (FIG. 2A) of the light receiving unit 102, and the light receiving unit 102. In the column direction (vertical direction) cross section (FIG. 2B), the metal film 115 is formed without the metal film 113 interposed therebetween. That is, the vertical step is lower than the horizontal step.

  Therefore, when the vertical width of the light receiving portion 102 is larger than the horizontal width (when the aspect ratio of the light receiving portion 102 deviates from 1), the curvature of the upper surface of the insulating film 116 in the vertical cross section is not appropriate. It can be prevented that the shape has a steep inclination. Thereby, it is possible to prevent the light condensing performance of the in-layer lens composed of the insulating film 116 and the insulating film 117 from being deteriorated with respect to the incident light 140.

  That is, in the solid-state imaging device 100 according to the embodiment of the present invention, in addition to the film thickness of the metal film 115 and the line width of the lattice, the horizontal and vertical cross sections can be independently obtained due to the difference in level difference. It can be formed into a shape having an appropriate curvature.

  In other words, the solid-state imaging device 100 according to the embodiment of the present invention can form an in-layer lens having a higher degree of design freedom than a conventional solid-state imaging device.

  The solid-state imaging device 100 according to the embodiment of the present invention has been described above, but the present invention is not limited to this embodiment.

  For example, in the above description, the metal film 113 is arranged in a stripe shape at a position facing the vertical transfer unit 103, but may be arranged in a lattice shape so as to cover other than the light receiving unit 102.

  In the above description, the insulating film 114 and the insulating film 116 are made of the same material, but may be made of different materials.

  Further, by selecting materials for the insulating film 114 and the insulating film 116 (specifically, materials having different refractive indexes), the downward convex curved surface generated by the insulating film 114 can have a lens function. it can.

  As a result, the solid-state imaging device according to the present invention includes an intra-layer lens composed of the insulating film 116 and the insulating film 117 and an intra-layer lens composed of the insulating film 114 and the insulating film 116. Therefore, the condensing efficiency of incident light onto the light receiving unit 102 can be improved by the two inner lenses.

  In the above description, the curved surfaces of the insulating films 114 and 116 are formed by heat flow treatment using BPSG. However, the curved surfaces of the insulating films 114 and 116 may be formed using other film materials and curved surface forming methods. Good. For example, the curved surfaces of the insulating films 114 and 116 may be formed by a spin coating (application) method such as SOG (Spin on Glass). Further, the curved surfaces of the insulating films 114 and 116 may be formed by a method of forming a film by ozone TEOS (ethyl silicate) -CVD.

  In the above description, the CCD solid-state imaging device has been described as an example. However, the present invention can also be applied to a MOS solid-state imaging device.

  In the MOS type solid-state imaging device, the wiring layer is generally composed of multiple layers, but the present invention can be applied to any wiring layer farthest from the wiring layer closest to the light receiving portion.

  That is, the insulating film 114, the dummy pattern (metal film) 115, and the insulating film 116 are formed on the wiring layer as shown in FIG. The effect shown in the form can be obtained.

  The present invention can be applied to a solid-state imaging device, and in particular, to an image input device such as a video camera, a digital still camera, and a facsimile.

It is a top view which shows the structure of the solid-state imaging device which concerns on embodiment of this invention. It is sectional drawing of the solid-state imaging device which concerns on embodiment of this invention. It is a top view which shows the structure of the metal film of the solid-state imaging device concerning embodiment of this invention. It is sectional drawing in the manufacture process of the solid-state imaging device concerning embodiment of this invention. It is sectional drawing in the manufacture process of the solid-state imaging device concerning embodiment of this invention. It is sectional drawing in the manufacture process of the solid-state imaging device concerning embodiment of this invention. It is sectional drawing in the manufacture process of the solid-state imaging device concerning embodiment of this invention. It is sectional drawing in the manufacture process of the solid-state imaging device concerning embodiment of this invention. It is sectional drawing in the manufacture process of the solid-state imaging device concerning embodiment of this invention. It is sectional drawing in the manufacture process of the solid-state imaging device concerning embodiment of this invention. It is sectional drawing which shows the structure of the conventional solid-state imaging device.

Explanation of symbols

100, 500 Solid-state imaging device 101, 501 Semiconductor substrate 102, 502 Light receiving unit 103, 503 Vertical transfer unit 104 Horizontal transfer unit 105 Amplifier unit 110, 112, 114, 116, 117, 504, 509, 510 Insulating film 111, 505 Vertical Transfer electrode 113, 115, 506 Metal film 118, 511 Protective film 119, 512 Color filter 120, 513 Micro lens 140, 521 Incident light 507 Etching stopper 508 Step adjustment film

Claims (8)

A semiconductor substrate;
A photoelectric conversion unit formed on the semiconductor substrate for converting light into signal charge;
An electrode for reading the signal charge converted by the photoelectric conversion unit;
A first insulating film formed above the photoelectric conversion part and the electrode and having a downward convex curved surface on the upper surface;
A step adjustment film formed above the electrode via the first insulating film;
A second insulating film formed above the step adjustment film and the first insulating film;
Formed on the second insulating film, made of a material having a refractive index different from that of the material constituting the second insulating film, and having a microlens shape in contact with the downwardly convex second insulating film A solid-state imaging device comprising: a third insulating film. The solid-state imaging device further includes:
Comprising a light-shielding film formed above the electrode;
The solid-state imaging device according to claim 1, wherein the first insulating film is formed above the photoelectric conversion unit and the light shielding film. The solid-state imaging device according to claim 1, wherein the step adjustment film is made of metal. The solid-state imaging device according to claim 3, wherein the metal is a refractory metal. The solid-state imaging device further includes:
A plurality of photoelectric conversion units arranged in a matrix including the photoelectric conversion units;
A plurality of electrodes including the electrodes for reading signal charges converted by the plurality of photoelectric conversion units arranged in each column,
The said light shielding film is arrange | positioned with respect to the some photoelectric conversion part arrange | positioned at the said matrix form at the stripe form of the column direction, and is arrange | positioned above the said some electrode. Solid-state imaging device. 6. The curvature of the convex microlens shape of the third insulating film is larger than the curvature of the convex curved surface shape of the first insulating film. 6. The solid-state imaging device described in 1. The solid-state imaging device according to claim 1, wherein the first insulating film and the second insulating film are formed of materials having different refractive indexes. A method of manufacturing a solid-state imaging device,
A first step of forming a photoelectric conversion unit for converting light into signal charge on a semiconductor substrate;
A second step of forming an electrode for reading the signal charge converted by the photoelectric conversion unit;
A third step of forming a first insulating film having a downward convex curve shape on the upper surface on the photoelectric conversion portion and the electrode;
A fourth step of forming a step adjustment film on the first insulating film by etching;
A fifth step of forming a second insulating film having a downwardly convex microlens shape on the upper surface on the step adjustment film and the first insulating film;
And a sixth step of forming a third insulating film made of a material having a refractive index different from that of the second insulating film so as to embed the microlens shape of the second insulating film. Manufacturing method of a solid-state imaging device.

Images