JP2007281047A - Solid imaging element and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structure and a manufacturing method of a solid imaging element capable of reducing occurrence of smears while keeping high light condensing efficiency. <P>SOLUTION: The solid imaging element has a first convex in-layer microlens 102 formed via a first interlayer film immediately above a light receiver 101, and has an on-chip lens 104 formed via a second interlayer film 109 and a color filter 110 immediately above the first in-layer microlens 102. A second concave in-layer microlens 103 is provided immediately below a region surrounded by the on-chip lens 104 on a surface layer of the second interlayer film 109 between the first in-layer microlens 102 and the on-chip lens 104. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a structure of a solid-state imaging device and a manufacturing method thereof.

  Currently, solid-state imaging devices (Charge-Coupled Devices; CCDs) are widely used as light receiving devices for digital cameras. In recent years, with the miniaturization of semiconductor processes, the size of solid-state imaging devices and the increase in density of pixels have progressed, and a decrease in sensitivity has become a problem.

  Conventionally, in order to improve sensitivity, a structure in which an in-layer microlens and an on-chip lens are provided on each unit light receiving portion is used.

  The structure of a conventional solid-state image sensor will be described with reference to FIG. FIG. 6A is a plan view of the solid-state imaging device having the first conventional structure as viewed from above. A first in-layer microlens 502 is disposed so as to cover the entire light receiving portion 501, and an on-chip lens 503 is formed so as to cover the entire first in-layer microlens 502.

  FIG. 6B is a cross-sectional view in the B-B ′ direction in FIG.

  As shown in FIG. 6B, a plurality of light receiving portions 501 are formed on the surface layer of the semiconductor substrate, and a gate 504 and a light shielding film 505 covering the gate 504 are formed so as to be positioned between the light receiving portions 501. ing. The light receiving portion 501 and the light shielding film 505 are covered with a first interlayer film 507, and a first in-layer microlens 502 is formed on the first interlayer film 507. Further, the first in-layer microlens 502 is disposed above the light receiving unit 501. The upper surface of the first in-layer microlens 502 is covered with the second interlayer film 508. A color filter 506 is formed on the entire surface of the second interlayer film 508, and an on-chip lens 503 is formed on the color filter 506 at a position directly above the light receiving unit 501 and the first in-layer microlens 502. Has been.

  It can be seen from FIG. 6B that the solid-state imaging device formed in this way has a gap between adjacent on-chip lenses 503. The light passing through the gap further passes through the color filter 506, the second interlayer film 508, and the first interlayer film 507, and reaches the light shielding film 505. Therefore, since the light passing between the on-chip lenses 503 cannot be condensed on the light receiving unit 501, high light collection efficiency cannot be obtained.

  In order to solve this problem, Patent Document 1 describes that an intra-layer microlens is arranged at a position where a gap between on-chip lenses is filled. Hereinafter, the second conventional structure will be described with reference to FIG.

  FIG. 7A is a plan view of a solid-state imaging device having a second conventional structure. An on-chip lens 603 is disposed so as to cover the entire light receiving unit 601, and a first in-layer microlens 602 is disposed so as to fill a gap between the on-chip lenses 603.

  FIG. 7B is a cross-sectional view in the C-C ′ direction in FIG.

  As shown in FIG. 7B, a plurality of light receiving portions 601 are formed on the surface layer of the semiconductor substrate, and a gate 604 and a light shielding film 605 covering the gate 604 are formed between the light receiving portions 601. The light receiving portion 601 and the light shielding film 605 are covered with a first interlayer film 607, and a concave first in-layer microlens 602 is formed above the first interlayer film 607. Further, the first in-layer microlens 602 is disposed above the light shielding film 605 disposed between the light receiving portions 601.

  A color filter 606 is formed so as to cover the entire surface of the first in-layer microlens 602 and the first interlayer film 607. On the color filter 606, an on-chip lens 603 is located immediately above the light receiving unit 601. Is formed.

According to the second conventional structure, the light passing through the gap between the adjacent on-chip lenses 603 is provided under the color filter 606 below the on-chip lens 603 and disposed in the gap between the on-chip lenses 603. With the concave first in-layer microlens 602 thus formed, light can be condensed on the light receiving unit 601 and high light collection efficiency can be obtained.
JP 11-87673 A

  However, in the solid-state imaging device having the second conventional structure, the light that has passed through the ineffective region of the gap between the on-chip lenses is refracted by the first in-layer microlens and collected in the light receiving unit to increase the light collection efficiency. At the same time, smear due to oblique light is generated.

  The generation of smear due to oblique light in the second conventional structure will be described with reference to FIG. FIG. 8 is a cross-sectional view of a solid-state imaging device having a second conventional structure, and the structure is the same as FIG. 7B. In FIG. 8, the light refracted by the first in-layer microlens 602 is also collected by the light receiving unit 601 (Y), but at the same time, part of the light enters the lower layer of the light shielding film 605 to generate smear (Z). . That is, the sensitivity characteristic is deteriorated.

  In view of the above, an object of the present invention is to improve sensitivity characteristics by reducing the occurrence of smear while maintaining high light collection efficiency in a solid-state imaging device having both in-layer microlenses and on-chip lenses. .

  In order to achieve the above object, the present invention refracts incident light passing through a gap, that is, an ineffective region of an on-chip lens on a color filter, by the second in-layer microlens and the first in-layer microlens. It is characterized by making it.

  That is, the solid-state imaging device of the present invention includes a plurality of light receiving portions formed on a substrate, and a convex first in-layer microlens provided via a first interlayer film at a position immediately above the light receiving portion. An on-chip lens provided immediately above the first in-layer microlens, and a concave second in-layer microlens in a layer sandwiched between the on-chip lens and the first in-layer microlens. The second in-layer microlens has a structure arranged immediately below a region surrounded by the on-chip lens.

  Thereby, the light passing through the on-chip lens is refracted by the first in-layer microlens and can reach the light receiving unit, so that high light collection efficiency can be obtained. Furthermore, since the light passing through the ineffective area surrounded by the on-chip lens is refracted by the concave second in-layer microlens and the convex first in-layer microlens, the light passes through the interface between the light receiving unit and the light shielding film. It is possible to reduce smear that occurs due to the penetration of.

  It is also preferable to provide a second interlayer film between the first in-layer microlens and the second in-layer microlens and a color filter between the second in-layer microlens and the on-chip filter.

  The first in-layer microlens is formed of an oxide film or an acrylic resin, the second interlayer film is formed of an oxynitride film, and the second in-layer microlens is formed of an oxide film or an acrylic resin. Is preferred.

  In this way, the difference in refractive index between the in-layer microlens and the interlayer film can be used to suppress the occurrence of smear and increase the light collection efficiency to the light receiving unit.

  In addition, it is preferable to have a third interlayer film between the second interlayer film and the second in-layer microlens.

  The first intralayer microlens is formed of a nitride film, the second interlayer film is formed of an oxynitride film, the third interlayer film is formed of a nitride film, and the second intralayer microlens is oxidized. It is preferably formed of a film or an acrylic resin.

  In this way, the difference in refractive index between the second interlayer film and the first interlayer film can also be used, so that the occurrence of smear can be suppressed and the light collection efficiency to the light receiving section can be further increased.

  In order to achieve the above object, the first solid-state imaging device manufacturing method according to the present invention includes a step of forming a plurality of light receiving parts on a substrate and a light shielding film covered at a position filling a gap between the light receiving parts. A step of forming a gate; a step of forming a convex first in-layer microlens via a first interlayer film at a position directly above the light-receiving portion; a first in-layer microlens and a first interlayer film Forming a second interlayer film thereon, forming a hard mask having an opening on the second interlayer film, and isotropically etching the second interlayer film through the hard mask. A step of removing the hard mask and embedding and planarizing a material to be the second in-layer microlens, a step of forming a color filter, and an on-chip lens at a position immediately above the first in-layer microlens. And forming a process. Opening of the hard mask is that formed immediately above the position of the region surrounded by the first layer microlens.

  In this way, the light passing through the on-chip lens is refracted by the first in-layer microlens and reaches the light receiving unit, so that the light collection efficiency can be improved, and further, the invalidity surrounded by the on-chip lens. The light passing through the region is refracted by the concave second in-layer microlens and the convex first in-layer microlens to reduce smear that occurs when light enters the interface between the light receiving portion and the light shielding film. The solid-state image sensor which can be manufactured can be manufactured.

  The second method for manufacturing a solid-state imaging device of the present invention includes a step of forming a plurality of light receiving portions on a substrate, a step of forming a gate covered with a light shielding film at a position filling a gap between the light receiving portions, Forming a convex first in-layer microlens via a first interlayer film at a position directly above the first portion; a second interlayer film on the first in-layer microlens and the first interlayer film; A step of sequentially forming the third interlayer film, a step of forming a hard mask having an opening on the third interlayer film, and isotropic etching are performed on the third interlayer film through the hard mask. A step of removing a hard mask and embedding and planarizing a material to be a second in-layer microlens; a step of forming a color filter; and a position directly above the first in-layer microlens via the color filter. To form an on-chip lens Has bets, the opening of the further hard mask is to be formed immediately above the position of the region surrounded by the first layer microlens.

  In this way, the difference in refractive index between the second interlayer film and the first interlayer film can also be used, and the solid that can suppress the occurrence of smear and further increase the light collection efficiency to the light receiving unit. An image sensor can be manufactured.

  ADVANTAGE OF THE INVENTION According to this invention, generation | occurrence | production of a smear can be reduced and a sensitivity characteristic can be improved, maintaining a high condensing efficiency in the solid-state image sensor which has an in-layer microlens and an on-chip lens.

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

(First embodiment)
The structure of the solid-state imaging device according to the first embodiment of the present invention will be described with reference to FIG.

  FIG. 1A is a plan view of the solid-state imaging device according to the present invention as viewed from above. A first in-layer microlens 102 is disposed so as to cover the entire light receiving unit 101, and an on-chip lens 104 is formed so as to cover the entire first in-layer microlens 102.

  FIG. 1B is a cross-sectional view in the A-A ′ direction in FIG. In FIG. 1B, a plurality of light receiving portions 101 are formed on the surface layer of a semiconductor substrate 105, and a gate 106 and a light shielding film 107 covering the gate 106 are formed between the light receiving portions 101. The light receiving unit 101 and the light shielding film 107 are covered with a first interlayer film 108, and a convex first in-layer microlens 102 is formed on the first interlayer film 108. The first in-layer microlens 102 is disposed above the light receiving unit 101. The first intra-layer microlens 102 is entirely covered with a second interlayer film 109. A concave second in-layer microlens 103 is formed above the second interlayer film 109. Further, the second in-layer microlens 103 is disposed above the light shielding film 107. A color filter 110 is formed so as to cover the entire surface of the second interlayer film 109 and the second in-layer microlens 103, and the light receiving unit 101 and the first in-layer microlens 102 are formed on the color filter 110. An on-chip lens 104 is formed immediately above. In other words, the second in-layer microlens 103 is provided at a position that complements the gap between the on-chip lenses 104.

  Hereinafter, the progress of incident light in the solid-state imaging device shown in the first embodiment will be described with reference to FIG.

  FIG. 2 is a schematic view of the traveling direction of incident light in the solid-state imaging device of the first embodiment. X indicates the traveling direction of incident light. Incident light that has passed through the color filter 110 from the gap between the on-chip lenses 104 is refracted when passing through the second in-layer microlens 103 and further refracted when passing through the first in-layer microlens 102. In this way, incident light is refracted in two stages to prevent light from entering the lower layer of the light shielding film 107. That is, smear is reduced.

  Next, the manufacturing method of the solid-state image sensor in the 1st Embodiment of this invention is demonstrated using FIG. A cross-sectional view of each step is shown in FIG.

  First, as shown in FIG. 3A, a plurality of light receiving portions 101 are formed on the surface layer of the semiconductor substrate 105, and a gate 106 and a light shielding film 107 are formed between the light receiving portions 101 so as to cover the gates 106. To do. Thereafter, a first interlayer film 108 is deposited so as to cover the entire surface of the light receiving portion 101 and the light shielding film 107.

  Next, as shown in FIG. 3B, a plasma nitride film having a refractive index of 2.0 is normally formed as a first in-layer microlens 102 via a first interlayer film 108 above the light receiving portion 101. A convex lens is formed in the lens forming step.

  Next, as shown in FIG. 3C, a plasma oxynitride film having a refractive index of 1.7 is formed as the second interlayer film 109 on the first interlayer film 108 and the first in-layer microlens 102. accumulate. Further, a film 111 for forming a hard mask is deposited on the second interlayer film 109.

  Next, as shown in FIG. 3D, a resist mask 112 having an opening for defining the position of the second in-layer microlens is formed on the film 111 for forming the hard mask. Thereafter, normal dry etching is performed to form the hard mask 111.

  Next, as illustrated in FIG. 3E, the resist 112 is removed, and the second interlayer film 109 is etched using the hard mask 111. By performing isotropic dry etching or wet etching as the etching of the second interlayer film 109, a concave depression is formed.

  Next, as shown in FIG. 3F, the hard mask 111 is removed. Thereafter, as shown in FIG. 3G, an oxide film having a refractive index of 1.4 is deposited as a material for the second intra-layer lens, and planarized by using ordinary means such as etch back or CMP. Thus, the concave second in-layer microlens 103 is formed.

  Next, as shown in FIG. 3H, the color filter 110 is formed so as to cover the entire surface of the second interlayer film 109 and the second in-layer microlens 103. Further, an on-chip lens 104 is formed on the color filter 110 as shown in FIG. The on-chip lens 104 is formed so as to be disposed immediately above the light receiving unit 101 and the first in-layer microlens 102. In other words, the on-chip lens 104 is formed at a position that complements the second in-layer microlens 103.

  In the first solid-state imaging device of the present invention, a plasma nitride film having a refractive index of 2.0 is used as the first in-layer microlens 102, and a plasma oxynitride film having a refractive index of 1.7 is used as the second interlayer film 109. An oxide film having a refractive index of 1.4 was selected as the second in-layer microlens 103, but a plasma nitride film having a refractive index of about 1.6 to 2.6 was used as the material of the first in-layer microlens 102. A plasma oxynitride film having a refractive index of about 1.5 to 1.9 is used as the material of the second interlayer film 109, and a refractive index of about 1.2 to 1.7 is used as the material of the second in-layer microlens 103. An oxide film may be used.

  The material of the second in-layer microlens 103 is effective for reducing smear even when an acrylic resin having a refractive index of about 1.5 to 1.7 is used.

(Second Embodiment)
The structure of the solid-state imaging device according to the second embodiment of the present invention will be described with reference to FIG.

  A plan view of the second solid-state imaging device according to the present invention when viewed from above is the same as that of the first embodiment, as shown in FIG. FIG. 4 shows a cross-sectional view of the solid-state imaging device in the second embodiment. FIG. 4 is a cross-sectional view in the A-A ′ direction in FIG.

  In FIG. 4, a plurality of light receiving portions 101 are formed on the surface layer of a semiconductor substrate 105, and a gate 106 and a light shielding film 107 covering the gate 106 are formed between the light receiving portions 101. The light receiving unit 101 and the light shielding film 107 are covered with a first interlayer film 108, and a convex first in-layer microlens 102 is formed on the first interlayer film 108. The first in-layer microlens 102 is disposed above the light receiving unit 101. The first in-layer microlens 102 and the first interlayer film 108 are entirely covered with the second interlayer film 109, and the above is the same as in the first embodiment.

  The difference from the first embodiment is that a third interlayer film 113 is further formed on the second interlayer film 109, and a concave second in-layer microlens 103 is formed on the surface layer of the third interlayer film 113. It is to have established. The second in-layer microlens 103 is disposed above the light shielding film 107 as in the first embodiment.

  The color filter 110 is formed so as to cover the entire surface of the third interlayer film 113 and the second in-layer microlens 103. On the color filter 110, the light receiving unit 101 and the first in-layer microlens 102 are formed. An on-chip lens 104 is formed at a position immediately above.

  Next, the manufacturing method of the solid-state image sensor in the 2nd Embodiment of this invention is demonstrated using FIG. A cross-sectional view of each step is shown in FIG.

  First, as shown in FIG. 5A, a plurality of light receiving portions 101 are formed on the surface layer of the semiconductor substrate 105, and a gate 106 and a light shielding film 107 are formed between the light receiving portions 101 so as to cover the gates 106. To do. Thereafter, a first interlayer film 108 is deposited so as to cover the entire surface of the light receiving portion 101 and the light shielding film 107.

  Next, as shown in FIG. 5B, a plasma nitride film having a refractive index of 2.0 is usually used as the first in-layer microlens 102 via the first interlayer film 108 above the light receiving portion 101. A convex lens is formed by forming the lens.

  Next, as shown in FIG. 5C, a plasma oxynitride film having a refractive index of 1.7 is formed as the second interlayer film 109 on the first interlayer film 108 and the first in-layer microlens 102. accumulate. The above is the same as the manufacturing method of the solid-state imaging device in the first embodiment.

  Next, the second interlayer film 109 is etched back to such an extent that the first in-layer microlenses 102 are not exposed.

  Thereafter, as shown in FIG. 5D, a plasma nitride film having a refractive index of 2.0 is deposited as the third interlayer film 113. Further, a film 111 for forming a hard mask is deposited on the third interlayer film 113. Thereafter, a resist mask 112 having an opening for defining the position of the second in-layer microlens is formed on the film 111 for forming the hard mask. Further, the hard mask 111 is formed by etching a portion not covered with the resist mask 112.

  The subsequent steps are the same as the method for manufacturing the solid-state imaging device in the first embodiment.

  As shown in FIG. 5E, the resist mask 112 is removed. Further, the third interlayer film 113 is etched using the hard mask 111. By performing isotropic dry etching or wet etching on the etching of the third interlayer film 113, a concave recess is formed on the surface of the third interlayer film 113. At this time, the etching is performed so as not to reach the second interlayer film 109, and the concave depression is formed only in the third interlayer film 113.

  Next, as shown in FIG. 5F, the hard mask 111 is removed. Thereafter, as shown in FIG. 5G, an oxide film having a refractive index of 1.4 is deposited as a material for the second intralayer lens, and is planarized using ordinary means such as etch back and CMP. Thus, the concave second in-layer microlens 103 is formed in the third interlayer film 113.

  Next, as shown in FIG. 5H, the color filter 110 is formed so as to cover the entire surface of the third interlayer film 113 and the second in-layer microlens 103. Further, an on-chip lens 104 is formed on the color filter 110 as shown in FIG. The on-chip lens 104 is formed so as to be disposed above the light receiving portion 101 and the first in-layer microlens 102.

  In the solid-state imaging device of the second embodiment, the difference in the refractive index of the interlayer film can be designed to be large by making the interlayer film into two layers. Therefore, compared with the solid-state imaging device described in the first embodiment. Thus, it is possible to further improve the light collection efficiency while suppressing the occurrence of smear.

  In the second solid-state imaging device of the present invention, the material of the first in-layer microlens 102 is a plasma nitride film having a refractive index of about 1.6 to 2.6, and the material of the second interlayer film 109 is The oxide film having a refractive index of about 1.2 to 1.7, the material of the third interlayer film 113 is a plasma nitride film having a refractive index of about 1.6 to 2.6, and the second in-layer microlens 103 is used. As the material, an oxide film having a refractive index of about 1.2 to 1.7 may be used.

  Further, an acrylic resin having a refractive index of about 1.5 to 1.7 may be used as the material of the second in-layer microlens 103.

  The present invention is suitable for a solid-state imaging device having a plurality of light-receiving elements formed on a semiconductor substrate, a signal charge detection device provided therein, and a camera having the solid-state imaging device, for example, a CCD image sensor, a MOS image sensor. It is suitable for digital still cameras, camera-equipped mobile phones, cameras built in notebook computers, camera units connected to information processing equipment, and the like.

The top view and sectional drawing which show the structure of the solid-state image sensor concerning 1st Embodiment Schematic which shows the course of the incident light in the solid-state image sensor which concerns on 1st Embodiment. Process drawing which shows the manufacturing method of the solid-state image sensor which concerns on 1st Embodiment. Sectional drawing which shows the solid-state image sensor which concerns on 2nd Embodiment. Process drawing which shows the manufacturing method of the solid-state image sensor which concerns on 2nd Embodiment. Plan view and sectional view showing the structure of a conventional solid-state image sensor Plan view and sectional view showing the structure of a conventional solid-state image sensor Schematic showing the path of incident light in a conventional solid-state image sensor

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Light-receiving part 102 1st layer micro lens 103 2nd layer micro lens 104 On-chip lens 105 Semiconductor substrate 106 Gate 107 Light-shielding film 108 1st interlayer film 109 2nd interlayer film 110 Color filter 111 Hard mask Film to be formed 112 Resist mask 113 Third interlayer film 501 Light receiving portion 502 First in-layer microlens 503 On-chip lens 504 Gate 505 Light shielding film 506 Color filter 507 First interlayer film 508 Second interlayer film 601 Light receiving portion 602 First in-layer microlens 603 On-chip lens 604 Gate 605 Shading film 606 Color filter 607 First interlayer film

Claims (7)

A plurality of light-receiving portions formed on a substrate; a convex first in-layer microlens provided via a first interlayer film immediately above the light-receiving portion; and the first in-layer microlens An on-chip lens provided immediately above, and a concave second in-layer micro lens in a layer sandwiched between the on-chip lens and the first in-layer micro lens,
The second in-layer microlens is disposed immediately below a region surrounded by the on-chip lens. A second interlayer film between the first in-layer microlens and the second in-layer microlens, and a color filter between the second in-layer microlens and the on-chip filter. The solid-state imaging device according to claim 1. The first in-layer microlens is formed of a nitride film, the second interlayer film is formed of an oxynitride film, and the second in-layer microlens is formed of an oxide film or an acrylic resin. The solid-state imaging device according to claim 2, wherein the solid-state imaging device is provided. The solid-state imaging device according to claim 2, further comprising a third interlayer film between the second interlayer film and the second in-layer microlens. The first intra-layer microlens is formed of a nitride film, the second interlayer film is formed of an oxynitride film, the third interlayer film is formed of a nitride film, The solid-state imaging device according to claim 4, wherein the second intra-layer microlens is formed of an oxide film or an acrylic resin. A step of forming a plurality of light receiving portions on the substrate, a step of forming a gate covered with a light-shielding film at a position filling a gap between the light receiving portions, and a position protruding directly above the light receiving portion via a first interlayer film Forming a first in-layer microlens of the mold, forming a second interlayer film on the first in-layer microlens and the first interlayer film, and on the second interlayer film Forming a hard mask having an opening in the substrate, performing isotropic etching on the second interlayer film through the hard mask, removing the hard mask, and forming a second in-layer microlens A step of embedding and planarizing a material to be formed, a step of forming a color filter on the second interlayer film and the second microlens in the second layer, and the color at a position directly above the microlens in the first layer ONCH through filter And forming a Prens,
The manufacturing method of a solid-state imaging device, wherein the opening of the hard mask is formed at a position immediately above a region surrounded by the first in-layer microlens. A step of forming a plurality of light receiving portions on the substrate, a step of forming a gate covered with a light-shielding film at a position filling a gap between the light receiving portions, and a position protruding directly above the light receiving portion via a first interlayer film Forming a first in-layer microlens of the mold, forming a second interlayer film and a third interlayer film in order on the first in-layer microlens and the first interlayer film, Forming a hard mask having an opening on the third interlayer film; performing isotropic etching on the third interlayer film through the hard mask; and removing the hard mask. A step of embedding and planarizing a material to be a second in-layer microlens, a step of forming a color filter so as to cover the third interlayer film and the second in-layer microlens, and the first layer The column is positioned directly above the inner microlens. And forming an on-chip lens through a filter,
The manufacturing method of a solid-state imaging device, wherein the opening of the hard mask is formed at a position immediately above a region surrounded by the first in-layer microlens.

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