JP2005302903A - Solid-state imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid-state imaging apparatus equalizing a sensitivity in a light-receiving region while having a constitution in which a manufacturing process is not complicated. <P>SOLUTION: In the solid-state imaging apparatus 20, a dummy pattern 2 is formed so as to surround a part or the whole of the outer periphery of a light receiver 8 formed on a semiconductor substrate 10, and the dummy pattern 2 reflects a light not to be incident on the light receiver 8 and makes it incident on the light receiver 8. According to such a solid-state imaging apparatus 20, the sensitivity in the light receiver can be equalized. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a solid-state imaging device, and more particularly to a solid-state imaging device capable of making the sensitivity in a light receiving region uniform.

  In the conventional solid-state imaging device, sensitivity deterioration at the outer periphery of the light receiving region has been avoided by increasing the area of the photodiode as the light receiving unit. However, in recent years, as the size of the solid-state imaging device is reduced and the number of pixels is increased, a decrease in sensitivity due to a reduction in the area of the light receiving portion has been a problem. For this reason, in order to solve this problem, a solid-state imaging device having a microlens on the light receiving unit has been developed at present.

  Hereinafter, a conventional solid-state imaging device including a microlens will be described with reference to FIGS. FIG. 4 is a plan view schematically showing a configuration of a pixel region of a conventional solid-state imaging device. FIG. 5 is a cross-sectional view schematically showing a cut surface when the pixel region of the solid-state imaging device of FIG. 4 is cut along the D-D ′ line. For convenience of explanation, in FIG. 4, the microlens 101, the first intermediate layer 111, and the second intermediate layer 112 are omitted.

  As shown in FIGS. 4 and 5, in the conventional solid-state imaging device 100, a light receiving unit 108 made of a photodiode and an element for reading signal charges accumulated in the photodiode is formed on a semiconductor substrate 101 made of silicon. Furthermore, a first intermediate layer 111 and a second intermediate layer 112 are provided thereon, and a microlens 101 is formed on the second intermediate layer 112. With this configuration, light incident not only above the light receiving unit 108 but also above the element isolation region 105 is condensed through the microlens 101 and passes through the second intermediate layer 112 and the first intermediate layer 111. Then, the light enters the light receiving unit 108. Then, the light incident on the light receiving unit 108 is converted into a signal charge by the light receiving unit 108 according to the amount of light, and is read out.

  Next, a case where incident light is irradiated onto a conventional solid-state imaging device will be described with reference to FIGS. FIG. 6 is a diagram schematically illustrating a state in the case where a normal incident light A is irradiated to a conventional solid-state imaging device. FIG. 7 is a diagram schematically illustrating a state where oblique incident light B is irradiated to a conventional solid-state imaging device.

  That is, in the structure of the conventional solid-state imaging device shown in FIGS. 4 and 5, when the incident light is vertical light (light in a direction perpendicular to the light receiving portion), as shown in FIG. The light of −X ° to + X ° with respect to A enters the light receiving unit 108. On the other hand, when the incident light of the same light amount as the incident light A and the incident light B of the oblique light (light having an angle in the oblique direction shifted from the direction perpendicular to the light receiving portion) is considered, As shown in FIG. 7, light of −X ° to + X ° with respect to the incident light B enters the light receiving unit 108. However, of the incident light B having a light intensity of −X ° to + X °, a part of the light is shifted outward from the light receiving unit 108 to reduce the amount of light incident on the light receiving unit 108, thereby reducing the sensitivity.

  As shown in FIG. 6 and FIG. 7, when the conventional solid-state imaging device was irradiated with incident light, the intensity of the light incident on the light receiving unit was examined. The results are shown in FIGS. That is, FIG. 8 is a diagram illustrating a result of examining the intensity of incident light on the light receiving unit when the incident light A perpendicular to the conventional solid-state imaging device is irradiated. FIG. 9 is a diagram illustrating a result of examining the intensity of incident light on the light receiving unit when the conventional solid-state imaging device is irradiated with incident light B having an oblique angle.

  As shown in FIG. 8, all of the light at −X ° to + X ° of the incident light A is incident on the central pixel of the light receiving unit 108 in the solid-state imaging device 100 and contributes to sensitivity, thereby obtaining good sensitivity. It is done. On the other hand, as shown in FIG. 9, in the peripheral pixels of the light receiving unit 108, all of the incident light B having a certain angle from the vertical direction of the surface of the light receiving unit 108 is −X ° to + X °. However, since the amount of light incident on the light receiving unit 108 is not incident on the light receiving unit 108, the sensitivity is lowered. That is, in FIG. 9, light incident at an angle between the two arrow heads cannot enter the light receiving unit 108 and does not contribute to sensitivity.

  Furthermore, as shown in FIG. 10, it can be considered that most of the incident light is irradiated outside the region of the light receiving unit 108 and hardly enters the light receiving unit 108. In this case, part of the incident light does not enter the light receiving portion 108, and the sensitivity of the outer peripheral portion is deteriorated with respect to the central portion of the light receiving region. That is, the sensitivity at the periphery of the light receiving unit 108 is further reduced, and the difference in sensitivity between the center of the light receiving unit 108 is increased.

In order to solve such a problem, for example, in Patent Document 1, the surface on which the microlens is formed has a convex shape in which the central portion of the element is raised, thereby suppressing a decrease in sensitivity in the peripheral portion. And a solid-state imaging device that suppresses luminance shading without shifting the light receiving unit.
JP 6-118209 A (published April 28, 1994)

  However, the solid-state imaging device of Patent Document 1 has a problem that not only the number of steps increases in the manufacturing process of the solid-state imaging device, leading to an increase in cost, but also the yield due to the complicated manufacturing process is reduced. is there.

  For this reason, there has been a strong demand for the development of a solid-state imaging device having a configuration in which the sensitivity in the light receiving region is made uniform and the manufacturing process is not complicated.

  The present invention has been made in view of the above problems, and an object thereof is to provide a solid-state imaging device having a configuration in which the sensitivity in the light receiving region is made uniform and the manufacturing process is not complicated. There is.

  In order to solve the above problems, the solid-state imaging device according to the present invention is provided with reflecting means so as to surround a part or all of the outer periphery of the light receiving means provided on the semiconductor substrate. The light is not reflected on the light receiving means, and is reflected to enter the light receiving means.

  According to the above configuration, the reflecting means is disposed on the light receiving means so as to surround all or part of the periphery thereof. For this reason, light that is not normally focused on the light receiving means, for example, incident light having an oblique angle, can be reflected by the reflecting means and incident on the light receiving means. Therefore, it is possible to prevent the occurrence of a difference in sensitivity between the vicinity of the center of the light receiving region and the vicinity of the outer periphery of the light receiving region in the solid-state imaging device, and there is an effect that the sensitivity in the light receiving region can be made uniform. .

  Furthermore, according to the above configuration, the reflection means is only formed on a part or all of the periphery of the light receiving means, so that the manufacturing process is not complicated and the yield can be prevented from being lowered. Play.

  In the solid-state imaging device according to the present invention, it is preferable that an insulating layer is provided between the light receiving means and the reflecting means.

  According to the above configuration, since the reflecting means is provided on the light receiving means via the insulating layer, it is possible to prevent the occurrence of a short circuit due to the electrical connection between the light receiving means and the reflecting means.

  In the solid-state imaging device according to the present invention, it is preferable that the light receiving unit includes a light conversion element and a reading element for reading signal charges accumulated in the light conversion element.

  According to the above configuration, it is possible to form a light receiving means with good sensitivity.

  In the solid-state imaging device according to the present invention, the reflecting means is preferably a metal wiring.

  According to said structure, a reflection means can be provided reliably and easily. The “metal wiring” here is more preferably a dummy pattern. According to such a configuration, it is possible to suppress the sensitivity deterioration of the outer periphery of the light receiving region by adding a dummy pattern for reflection to the metal wiring layer, and to receive light more easily without complicating the manufacturing process. The sensitivity in the area can be made uniform.

  In the solid-state imaging device according to the present invention, a light collecting unit for collecting incident light is provided above the light receiving unit, and the light not incident on the light receiving unit is the light collecting unit. Therefore, it is preferable that the incident light has an angle that is not condensed on the light receiving means.

  According to said structure, since the condensing means is provided, incident light can be more reliably condensed to a light-receiving means. Further, since the reflecting means is provided, light having an angle that is not collected by the light collecting means with respect to the light receiving means (for example, oblique incident light) can be reflected by the reflecting means and incident on the light receiving means. It becomes possible. For this reason, the sensitivity in the vicinity of the central portion of the light receiving region and the sensitivity in the vicinity of the outer peripheral portion of the light receiving region in the solid-state imaging device can be made even more reliably.

  Here, “incident light having an angle that does not collect light on the light receiving means” refers to light that does not irradiate the region where the light receiving means is provided among the light collected by the light collecting means. For example, light having an angle (oblique angle) deviating from a direction perpendicular to the light receiving means and not irradiating the light receiving means may be used.

  Moreover, as the “light collecting means” here, for example, a microlens is preferable.

As described above, the solid-state imaging device according to the present invention is provided with the reflecting means so as to surround a part or all of the outer periphery of the light receiving means provided on the semiconductor substrate.
The reflecting means is for reflecting light that is not incident on the light receiving means so that the light is incident on the light receiving means. There is an effect that the sensitivity can be made uniform. That is, according to the solid-state imaging device according to the present invention, there is an effect that luminance shading can be suppressed.

  Furthermore, according to the solid-state imaging device according to the present invention, since the reflecting means is only formed in part or all around the light receiving means, the manufacturing process is not complicated and the yield is prevented from being lowered. There is an effect that can be.

  One embodiment of the present invention is described below with reference to FIGS. FIG. 1 is a plan view schematically showing the configuration of the pixel region of the solid-state imaging device according to the present embodiment. FIG. 2 is a cross-sectional view schematically showing a cut surface when the pixel region of the solid-state imaging device of FIG. 1 is cut along the C-C ′ line. For convenience of description, in FIG. 1, the microlens 1, the first intermediate layer 11, and the second intermediate layer 12 are omitted.

  As shown in FIGS. 1 and 2, the solid-state imaging device 20 according to the present embodiment includes a microlens 1 that functions as a condensing unit, a dummy pattern 2 of metal wiring that functions as a reflecting unit, and N + on a semiconductor substrate 10. Metal wiring 3 electrically connected to region 6 through contact hole 4, element isolation region 5, gate electrode 7, light receiving portion 8, first intermediate layer 11 functioning as an insulating layer, second intermediate layer 12 is provided. The semiconductor substrate 10 is made of, for example, silicon. Moreover, the 1st intermediate | middle layer 11 and the 2nd intermediate | middle layer 12 can be formed with an acrylic transparent substrate, for example. In addition, the light receiving unit 8 includes a light conversion element such as a photodiode and an element for reading signal charges accumulated in the light conversion element. In this embodiment, the dummy pattern 2 is formed as a dummy pattern having no electrical connection means. However, the present invention is not limited to this and is a metal wiring having a normal electrical connection function. May be.

  On the semiconductor substrate 10, an element isolation region 5, an N + region 6, and a light receiving portion 8 are formed. Above these, the contact hole 4, the gate electrode 7, and the first intermediate layer 11 are formed. In addition, a dummy pattern 2 and a metal wiring 3 are formed above them, and a second intermediate layer 12 and a microlens 1 are formed above them. That is, the first intermediate layer 11 is formed on the semiconductor substrate 10, the metal wiring layer is formed on the first intermediate layer 11, the second intermediate layer 12 is formed, and the second intermediate layer is formed. It can be said that the microlens 1 is formed on 12.

  The configurations of the element isolation region 5, the N + region 6, the light receiving portion 8, the contact hole 4, the gate electrode 7, and the metal wiring 3 formed on the semiconductor substrate 10 are not particularly limited, and a conventionally known solid-state imaging device It can be formed similarly. The first intermediate layer 11 and the second intermediate layer 12 may be a transparent substrate made of a material having a property of transmitting light. Specific thickness, shape, material, and the like are conventionally known solid-state imaging. The thickness, shape, material, and the like that can be used in the apparatus can be suitably used. The configuration of the microlens 1 is not particularly limited as long as it is formed as a light collecting unit that can be used in a conventionally known solid-state imaging device.

  That is, it can be said that the solid-state imaging device 20 according to the present embodiment has substantially the same configuration as the conventional solid-state imaging device except for the dummy pattern 2. Therefore, the dummy pattern 2 which is the most characteristic configuration of the solid-state imaging device 20 according to the present embodiment will be described in detail below.

  As shown in FIG. 1, the dummy pattern 2 is formed so as to surround the entire outer periphery of the light receiving unit 8. That is, the dummy pattern 2 is formed so as to surround the end portion of the light receiving unit 8 along the outer edge portion of the light receiving unit 8 of the light receiving unit 8 formed on the semiconductor substrate 10. Further, as described above, the dummy pattern 2 is formed so as to function as reflecting means for reflecting light that is not incident on the light receiving unit 8 to be incident on the light receiving unit 8. Here, “light that does not enter the light receiving unit 8” refers to light that does not enter the light receiving unit 8 among the light collected by the microlens 1. As described above, among the light irradiated to the solid-state imaging device 20, the light having an angle deviated from the direction perpendicular to the light receiving unit 8 (the surface thereof) is received even if it is condensed by the microlens 1. There is light that is not incident on the portion 8 but is incident on the outside of the light receiving portion 8, which means light having such a so-called oblique angle.

  In the present embodiment, the dummy pattern 2 is formed so as to surround the entire light receiving unit 8, but is not limited thereto, and is formed so as to surround only a part of the outer periphery of the light receiving unit 8, for example. May be. However, since the dummy pattern 2 functions as a reflecting means for reflecting light that is not incident on the light receiving unit 8 and entering the light receiving unit 8, only the part around the light receiving unit 8 is formed. It is preferable to be formed around the entire periphery of the light receiving portion 8. This is because when the dummy pattern 2 is formed around the entire periphery of the light receiving portion 8, the light that protrudes in all directions can be reflected and reliably incident on the light receiving portion 8.

  Further, as shown in FIG. 2, a first intermediate layer 11 that functions as an insulating layer is formed between the dummy pattern 2 and the region where the light receiving portion 8 is formed. That is, the dummy pattern 2 is provided on the light receiving unit 8 via the first intermediate layer 11.

  Due to the above-described configuration, as shown in FIG. 2, when the dummy pattern 2 is not provided, even the light that does not enter the light receiving unit 8 is reflected by the solid-state imaging device 20 according to the present embodiment. Since the dummy pattern 2 functioning as is provided, after being condensed by the microlens 1, it is reflected by the side surface of the dummy pattern 2 and enters the light receiving unit 8.

  Here, FIG. 3 shows the result of examining the intensity of the incident light to the light receiving unit when the solid-state imaging device according to the present embodiment is irradiated with the incident light B having an oblique angle. As shown in the figure, according to the solid-state imaging device 20 according to the present embodiment, the light in the region sandwiched between the two arrow heads in FIG. It can be seen that the light is reflected by the dummy pattern 2 and is incident on the light receiving unit 8. Comparing this result with FIG. 9 showing the same test result in the conventional solid-state imaging device, the solid-state imaging device 20 according to the present embodiment can achieve uniform sensitivity in the light receiving region as compared with the conventional one. It can be seen that luminance shading can be suppressed.

  As described above, according to the solid-state imaging device 20 according to the present embodiment, light that is not normally condensed on the light receiving unit 8, for example, incident light having an oblique angle is reflected by the dummy pattern 2 that functions as a reflecting means. And can be incident on the light receiving unit 8. Therefore, it is possible to prevent the difference in sensitivity between the vicinity of the central portion of the light receiving unit 8 and the vicinity of the outer peripheral portion of the light receiving unit 8 in the solid-state imaging device 20, and make the sensitivity in the light receiving unit 8 uniform. it can.

  Further, in the solid-state imaging device 20 according to the present embodiment, it is possible to suppress the sensitivity deterioration of the outer peripheral portion of the light receiving unit 8 only by adding the dummy pattern 2 as the reflecting means to the metal wiring layer. The manufacturing process is not complicated. For this reason, it is possible to prevent a decrease in yield due to the complexity of the process. That is, since the correction is only on the layout, the process is not complicated as in the prior art (the above-mentioned Patent Document 1), and can be realized without cost.

  In the present embodiment, the light is reflected by the side surface of the dummy pattern 2, but the present invention is not limited to this configuration. That is, the dummy pattern 2 functioning as the reflecting means may be configured to reflect light and enter the light receiving portion 8 as the light receiving means. For example, the dummy pattern 2 may be formed in a semi-cylindrical shape, or a triangular prism. It may be formed in a polygonal column shape such as a shape.

  Needless to say, the material, size, shape, and the like of the dummy pattern 2 can be appropriately set and changed so as to function as a reflecting means.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims. That is, embodiments obtained by combining technical means appropriately modified within the scope of the claims are also included in the technical scope of the present invention.

  For example, in a solid-state imaging device having an optical conversion element provided on a semiconductor substrate and an element for reading out signal charges accumulated in the optical conversion element, the light is received by a metal wiring arranged on the element via an insulating film. A solid-state imaging device in which a dummy pattern is arranged so as to surround the outside of the unit is also included in the present invention.

  As described above, the solid-state imaging device according to the present invention has the advantages as described above. Therefore, various electrical equipment, precision machinery, medical equipment and other manufacturing industries using the solid-state imaging device, and the related industries. In industry, a wide range of industrial applications will be possible.

It is a top view which shows typically the structure of the pixel area | region of the solid-state imaging device which concerns on this Embodiment. FIG. 2 is a cross-sectional view schematically showing a cut surface when a pixel region of the solid-state imaging device of FIG. 1 is cut along a C-C ′ line. It is a figure which shows the result of having investigated the intensity | strength of the incident light to a light-receiving part at the time of irradiating the incident light B which has an oblique angle to the solid-state imaging device which concerns on this Embodiment. It is a top view which shows typically the structure of the pixel area | region of the conventional solid-state imaging device. FIG. 5 is a cross-sectional view schematically showing a cut surface when the pixel region of the solid-state imaging device of FIG. 4 is cut along a D-D ′ line. It is a figure which shows typically a mode at the time of irradiating the normal incident light A with respect to the conventional solid-state imaging device. It is a figure which shows typically a mode at the time of irradiating the diagonal incident light B with respect to the conventional solid-state imaging device. It is a figure which shows the result of having investigated the intensity | strength of the incident light to a light-receiving part at the time of irradiating the normal incident light A to the conventional solid-state imaging device. It is a figure which shows the result of having investigated the intensity | strength of the incident light to a light-receiving part when the incident light B which has an oblique angle is irradiated to the conventional solid-state imaging device. It is a figure which shows typically a mode at the time of entering the incident light which is diagonally incident on the conventional solid-state imaging device and does not enter the light receiving part.

Explanation of symbols

1 Microlens (light collecting means)
2 Dummy pattern (reflecting means, metal wiring)
3 Metal wiring 4 Contact hole 5 Element isolation region 6 N + region 7 Gate electrode 8 Light receiving portion (light receiving means)
10 Semiconductor substrate 11 First intermediate layer (insulating layer)
12 Second intermediate layer 20 Solid-state imaging device

Claims (7)

Reflecting means is provided so as to surround part or all of the outer periphery of the light receiving means provided on the semiconductor substrate,
The solid-state image pickup device, wherein the reflecting means is for reflecting light that is not incident on the light receiving means so as to be incident on the light receiving means.   The solid-state imaging device according to claim 1, wherein an insulating layer is provided between the light receiving unit and the reflecting unit.   The solid-state imaging device according to claim 1, wherein the light receiving unit includes a light conversion element and a reading element for reading signal charges accumulated in the light conversion element.   The solid-state imaging device according to claim 1, wherein the reflecting means is a metal wiring.   The solid-state imaging device according to claim 4, wherein the metal wiring is a dummy pattern. Above the light receiving means, a light collecting means for collecting incident light is provided,
2. The solid-state imaging device according to claim 1, wherein the light that does not enter the light receiving unit is incident light having an angle that is not collected by the light collecting unit. The solid-state imaging device according to claim 6, wherein the condensing unit is a microlens.

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