JP2009146957A - Solid-state imaging apparatus, and manufacturing method of solid-state imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve a light convergence rate while enhancing uniformity of the amount of incident light to each pixel in a light receiving pixel region, and also to effectively prevent erroneous incident light from being incident on a light shield pixel region constituting optical black generating a black reference signal. <P>SOLUTION: In a solid-state imaging apparatus, the film thickness of a protective film 31 in the light receiving pixel region 3 can be made constant by providing a boundary pixel region 2 between the light shield pixel region 1 and light receiving pixel region 3, so pixel characteristics of a light receiving pixel region 3 disposed closest to the light shield pixel region 1 can be matched with the same characteristics as respective pixel characteristics in other light receiving pixel regions 3, and erroneous light can be effectively prevented from being incident on photoelectric converting elements in the light shield pixel region 1 forming an optical black region on which black is based. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a solid-state imaging device that captures an image using a photoelectric conversion element and a manufacturing method thereof.

  Conventionally, in a solid-state imaging device such as a CCD image sensor or a CMOS image sensor, light to the photoelectric conversion element is blocked in order to adjust the luminance of the imaging signal obtained by the photoelectric conversion element in the light receiving pixel region arranged in two dimensions. A light-shielded pixel region having a light-shielding film is provided, and a signal from the light-shielded pixel region is used as a luminance reference signal. This reference signal provides a black reference, and the light-shielded pixel region that generates the black reference signal without receiving light is called optical black.

  It is desirable that the photoelectric conversion elements in the light-shielding pixel area constituting the optical black have exactly the same characteristics as the photoelectric conversion elements in the light-receiving pixel area. Therefore, the light-receiving pixel area and the light-shielding pixel area are arranged as close as possible. The

  Also in the solid-state imaging device, the pixel area has been miniaturized due to a demand for further miniaturization and the like, and as a result, the sensitivity is lowered due to the reduction in the area of the photoelectric conversion element. A technology is known in which a microlens is formed on the surface on which the protective film provided on the photoelectric conversion element is flattened, and is focused on the photoelectric conversion element to suppress the decrease in sensitivity. However, a structure in which an in-layer lens composed of a film having a refractive index different from that of an adjacent layer is provided between the microlens and the photoelectric conversion element for further condensing is proposed.

  Hereinafter, the configuration of a conventional solid-state imaging device having a microlens and a convex in-layer lens will be briefly described with reference to FIG. FIG. 7 is a cross-sectional view showing a solid-state imaging device having a conventional microlens and a convex in-layer lens.

In FIG. 7, 1 is a light-shielding pixel region, 3 is a light-receiving pixel region, 4 is a photoelectric conversion element, 104 is a first metal wiring layer, 105 is a second metal wiring layer, 106 is a third metal wiring layer, and 107 is a protective film. , 108 are intra-layer lenses, 109 is a planarizing film, 110 is a color filter layer, and 111 is a microlens. As shown in FIG. 7, the conventional solid-state imaging device includes a light-shielding pixel region 1 and a light-receiving pixel region 3, and includes a microlens 111, an intralayer lens 108, a photoelectric conversion element, and a plurality of metal wiring layers. A third metal wiring layer 106 is formed as a light shielding film via a protective film 107 immediately below the inner lens 108 in the light shielding pixel region 1. By providing the in-layer lens 108 in this manner, the distance to the photoelectric conversion element can be shortened, and the light collection efficiency can be increased without causing a decrease in sensitivity (for example, see Patent Document 1).
JP 2007-13061 A

  However, in the structure in which the light-receiving pixel region 3 and the light-shielding pixel region 1 are arranged next to each other as shown in FIG. 7, the level difference caused by the film thickness of the third metal wiring 106 that is the light-shielding film of the light-shielding pixel region 1 is flattened. Therefore, the in-layer lens 108 provided in the light-receiving pixel disposed adjacent to the step is not the same as the in-layer lens 108 provided in the light-receiving pixel sufficiently away from the step. Therefore, the combined height of the inner lens 108 and the protective film 107 fluctuates, or the inner lens 108 tilts, resulting in the light collection rate and optical characteristics of the pixel. Varies, and the amount of incident light on the photoelectric conversion element 4 varies. In addition, incident light reflected by the side surface of the stepped portion of the third metal wiring layer 106 is incident on the light receiving pixel region 3 adjacent to the light shielding pixel region 1, and fluctuations in sensitivity due to receiving illegal reflected light are added, An imaging signal from a light receiving pixel adjacent to the light shielding pixel region 3 causes a characteristic variation. As a result, the device cannot obtain uniform imaging characteristics over all pixels in the light receiving pixel region 3.

  In addition, in the case of a CMOS image sensor that has been miniaturized, a multilayer wiring is often used for wiring between pixels, and the distance between the inner lens and the photoelectric conversion element becomes large, and the pixel is disposed adjacent to the light shielding pixel. Part of the light incident on the light-receiving pixels becomes stray light due to diffraction and reflection by the wiring film, and is incident on the adjacent light-shielding pixels, so that the black reference signal generated by the light-shielded pixels receives illegal light and is generated Signal will be included. In particular, in the case of long-wavelength light, since the incident depth is large, the ratio of reaching the light-shielded pixels increases.

  Accordingly, the present invention can improve the light collection rate while improving the uniformity of the amount of light incident on each pixel in the light receiving pixel region, and can effectively use the illegal incident light to the light shielding pixel region constituting the optical black that generates the black reference signal. The purpose is to prevent.

  In order to achieve the above-described object, a solid-state imaging device according to the present invention includes a semiconductor substrate having a photoelectric conversion element formed on a main surface and having a light-receiving pixel region, a boundary pixel region, and a light-shielding pixel region; An interlayer insulating film formed on the interlayer insulating film, a wiring layer formed on the interlayer insulating film, a first intra-layer lens formed on the interlayer insulating film in the light receiving pixel region, and the boundary pixel region A first incident light limiting film formed on the interlayer insulating film; and a light shielding film formed on the interlayer insulating film in the light shielding pixel region, wherein the boundary pixel region includes a light receiving pixel region and the light shielding pixel. It is characterized by being formed between the regions.

Further, a second in-layer lens is further provided on the interlayer insulating film in the boundary pixel region.
In addition, a second incident light limiting film is further provided on the interlayer insulating film in the light-shielding pixel region.

Further, the wiring layer, the first incident light limiting film, and the second incident light limiting film are made of the same material.
Further, a color filter is provided on the interlayer insulating film in the light receiving pixel region.

Moreover, a microlens is provided on the interlayer insulating film in the light receiving pixel region.
In addition, a contact pad for connecting to the outside is further provided, and the light shielding film and the contact pad are formed of the same material.

The bottom surface of the first intra-layer lens is lower than the top surface of the light shielding film.
A step of forming a photoelectric conversion element on a semiconductor substrate having a light-receiving pixel region, a boundary pixel region, and a light-shielding pixel region; a step of forming an interlayer insulating film on the semiconductor substrate; and a wiring on the interlayer insulating film Forming a layer; forming an incident light limiting film on the interlayer insulating film in the boundary pixel region; forming a light shielding film on the interlayer insulating film in the light shielding pixel region; and the light receiving pixel. And forming an intra-layer lens on the interlayer insulating film in the region.

Further, the wiring layer forming step and the incident light limiting film forming step are performed simultaneously.
As described above, it is possible to improve the light collection rate while improving the uniformity of the amount of light incident on each pixel in the light receiving pixel region, and to prevent illegal incident light to the light shielding pixel region constituting the optical black that generates the black reference signal. Can do.

  According to the solid-state imaging device of the present invention, by providing the boundary pixel region between the light-shielding pixel region and the light-receiving pixel region, the thickness of the protective film in the light-receiving pixel region can be made constant. On the other hand, the photoelectric conversion element of the light-shielding pixel region which can match the pixel characteristic of the light receiving pixel arranged closest to the pixel characteristic of each of the other light receiving pixels and forms an optical black region serving as a black reference It is possible to effectively prevent unauthorized incident light on the screen.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components exemplified in the present embodiment should be changed as appropriate according to the configuration of the apparatus to which the present invention is applied and various conditions. It is not limited to those examples.

First, the configuration of the solid-state imaging device of the present invention will be described with reference to FIGS.
FIG. 1 is a cross-sectional view showing a configuration of a solid-state imaging device according to the present invention, which shows a part of a solid-state imaging device having imaging pixels, where 1 is a light-shielding pixel region, 2 is a boundary pixel region, and 3 is light-receiving Pixel region, 4 is a photoelectric conversion element that converts incident light into a charge signal, 11 is a first interlayer insulating film, 12 is a second interlayer insulating film, 13 is a third interlayer insulating film, 14 is a fourth interlayer insulating film, 21 is a first metal wiring layer that transmits a charge signal as an image signal, 22 is a second metal wiring layer that transmits a charge signal as an image signal, 23 is a third metal wiring layer that transmits a charge signal as an image signal, and 24 An incident light limiting film, 25 is a light shielding film, 31 is a protective film, 32 is an inner lens, 33 is a first planarizing film, 34 is a color filter film, 35 is a second planarizing film, and 36 is a microlens.

  As shown in FIG. 1, the light shielding film 25 includes a first interlayer insulating film 11, a second interlayer insulating film 12, and a third interlayer insulating film 13 in order to shield incident light on the photoelectric conversion element 4 in the light shielding pixel region 1. In addition, a part of the third metal wiring layer 23 is provided as the incident light limiting film 24 via the fourth interlayer insulating film 14. The light shielding film 25 is not formed in the boundary pixel region 2, the intralayer lens 32 is provided on the protective film 31, and the incident light limiting film 24 that attenuates the incident light is provided below the inner lens 32. The first interlayer insulating film 11, the second interlayer insulating film 12, the third interlayer insulating film 13, the fourth interlayer insulating film 14, and the protection so that sufficient incident light can reach the photoelectric conversion element 4 in the light receiving pixel region 3. An in-layer lens 32 is provided via the film 25.

  Here, a metal film mainly composed of Al is used for the light shielding film 25 in the light shielding pixel region 1, and the wiring film and incident light of the first metal wiring layer 21, the second metal wiring layer 22, and the third metal wiring layer 23 are used. The limiting film 24 is a metal film mainly composed of Cu. Further, although not shown here, the light shielding film 25 can be formed of the same metal film as the contact pad film mainly composed of Al used for connection to the outside, and is formed at the same time.

  In general, when a Cu film is formed in a large area, it is thinned with respect to the periphery at the center of the formation region due to a phenomenon called dishing. However, for the purpose of attenuating incident light in the light-shielding pixel region 1 and the boundary pixel region 2. Since the incident light limiting film 24 arranged has only one or two columns in the boundary pixel region 2, there is almost no thinning due to dishing, and there is an effect of sufficiently attenuating incident light. On the other hand, dishing that occurs in the light-shielding pixel region 1 that requires a large region is not problematic because the light-shielding film 25 exists on the top. In the present embodiment, the incident light limiting film 24 is disposed over the light shielding pixel region 1, but it is also possible to form a part of the gap, and the incident light limiting film 24 formed by a metal wiring layer is completely used as the light shielding pixel region 1. It is possible to adopt a configuration not provided in

  FIG. 2 is a plan view showing the configuration of the solid-state imaging device of the present invention, which is a plane in which the configurations of the light-shielding film 25 and the inner lens 32 are understood, and is between the light-shielding pixel region 1 and the light-receiving pixel region 3. A provided boundary pixel region 2 is shown. A light shielding film 25 is disposed in the light shielding pixel region 1, and an intralayer lens 32 is provided in the light receiving pixel region 3 and the boundary pixel region 2. In this embodiment, the boundary pixel region 2 is provided for one pixel, but it is also possible to provide a pixel column of two or more pixels. The incident light limiting film 24 disposed for the purpose of attenuating incident light in the light-shielding pixel region 1 and the boundary pixel region 2 is disposed up to the end of the in-layer lens 32 in the light-receiving pixel region 3. This is sufficiently effective in preventing illegally incident light on the region 1. In addition, the incident light limiting film 24 arranged for the purpose of attenuating incident light is thinned with respect to the periphery at the center of the formation region due to a phenomenon called dishing when formed in a large area with a Cu film. However, since the number of pixels set in the boundary pixel region 2 is only one or two columns, there is almost no thinning by dishing, and there is an effect of attenuating sufficient incident light. On the other hand, dishing that occurs in the light-shielding pixel region 1 that requires a large region is not problematic because the light-shielding film 25 exists on the top.

Next, the manufacturing method of the solid-state imaging device according to the present invention described above will be described with reference to FIGS.
3 is a process cross-sectional view illustrating a process for forming an element region in the method for manufacturing a solid-state imaging device according to the present invention, FIG. 4 is a process cross-sectional view illustrating a process for forming a light shielding film in the method for manufacturing a solid-state image capturing apparatus according to the present invention. FIG. 6 is a process cross-sectional view illustrating an intra-layer lens forming process in the method for manufacturing a solid-state imaging device of the present invention, and FIG. 6 is a process cross-sectional view illustrating a color filter layer forming process in the method for manufacturing a solid-state image capturing apparatus of the present invention. Parts corresponding to 1 are denoted by the same reference numerals.

  First, as shown in FIG. 3, the photoelectric conversion elements 4 of the respective pixels are formed in the same manner in the light-shielding pixel region 1, the boundary pixel region 2, and the light-receiving pixel region 3 on the substrate. For the purpose of taking out, the first metal wiring layer 21, the second metal wiring layer 22 and the third metal wiring layer 23 are formed by the damascene method using a Cu film to form the first interlayer insulating film 11, the second interlayer insulating film 12 and the third interlayer. It is formed through the insulating film 13. Here, the third metal wiring layer 23 is formed as a wiring layer in the light receiving pixel region 3, and is formed as an incident light limiting film 24 over the region covering each pixel in the light shielding pixel region 1 and the boundary pixel region 2.

  Next, as shown in FIG. 4, after the fourth interlayer insulating film 14 is formed on the upper surfaces of the third metal wiring layer 23 and the incident light limiting film 24, the light shielding film 25 is made of the light shielding pixel region 1 using an Al film. At the same time, a contact pad electrode is formed on the outside. Thereafter, the protective film 31 is formed to be thinner than the light shielding film 25, so that the upper surface of the protective film 31 in the light receiving pixel region 1 and the boundary pixel region 2 is positioned lower than the upper surface of the light shielding film 25. Increase optical properties.

  Then, as shown in FIG. 5, an intralayer lens 32 is formed on the protective film 31 for each pixel in the boundary pixel region 2 and the light receiving pixel region 3. Thereafter, a first planarizing film 33 is formed, and a step between the light shielding film 25 and the inner lens 32 is planarized.

  Then, as shown in FIG. 6, a color filter layer 34 is formed, and a second planarizing film 35 is formed for the planarization. As the color filter, RGB primary color filters, cyan, magenta, yellow, green complementary color filters, or no color filter may be provided. When the color filter layer 34 is not provided, it is not necessary to provide the second flattening layer 35, the microlens 35 can be formed on the first flattening layer 33, and the solid-state imaging device can be further thinned. Is possible.

Finally, a microlens 36 is formed on the second planarizing film 35 to obtain the solid-state imaging device of the present invention shown in FIG.
As described above, in the solid-state imaging device according to the present invention, by providing the boundary pixel region between the light-shielding pixel region and the light-receiving pixel region, only the edge of the light-shielding film formed on the light-shielding pixel region is caused by the difference in thickness of the protective film. Since the slope is formed, the film thickness of the protective film is entirely constant over the light receiving pixel region, and the distance between the in-layer lens formed thereon and the photoelectric conversion element is kept constant. As a result, the condensing characteristic of the inner lens of each pixel is uniform over the entire light receiving pixel area, and the light condensing characteristic is made uniform while improving the light condensing efficiency with respect to the photoelectric conversion element in the light receiving pixel area. it can. In addition, by providing a boundary pixel region between the light-shielding pixel region and the light-receiving pixel region, it is possible to effectively prevent illegal incident light on the light-shielding pixel region constituting the optical black that generates the black reference signal.

In the above description, a MOS image sensor is assumed as the solid-state imaging device of the present invention. However, the present invention can be similarly applied to a CCD image sensor having no wiring layer on the light receiving surface.
Further, the present invention is not limited to the above-described solid-state imaging device using visible light, and can be similarly applied to a solid-state imaging device using invisible light such as infrared rays.

  In the above-described embodiment, three interlayer insulating films and three metal wiring layers are provided, but two layers may be provided, thereby further reducing the thickness of the solid-state imaging device. Further, the interlayer insulating film and the metal wiring layer may each be four or more layers, and the distance between the light receiving pixel for condensing and the microlens may be increased.

  Furthermore, although each metal wiring layer is a Cu film by a damascene method, it may be formed by an Al film by an etching method. Thereby, since the incident light limiting film is formed of Al, it is possible to make the light shielding property higher than that of Cu.

  The present invention can improve the light collection rate while improving the uniformity of the amount of light incident on each pixel in the light-receiving pixel region, and prevents illegal incident light on the light-shielding pixel region constituting the optical black that generates the black reference signal. It is useful for a solid-state imaging device that captures an image using a photoelectric conversion element, a manufacturing method thereof, and the like.

Sectional drawing which shows the structure of the solid-state imaging device of this invention The top view which shows the structure of the solid-state imaging device of this invention Process sectional drawing explaining the element area | region formation process in the manufacturing method of the solid-state imaging device of this invention Process sectional drawing explaining the light shielding film formation process in the manufacturing method of the solid-state imaging device of this invention Process sectional drawing explaining the intra-layer lens formation process in the manufacturing method of the solid-state imaging device of this invention Process sectional drawing explaining the color filter layer formation process in the manufacturing method of the solid-state imaging device of this invention Sectional drawing which shows the structure of the solid-state imaging device which has a micro lens and a convex inner lens

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light-shielding pixel area | region 2 Boundary pixel area | region 3 Light reception pixel area | region 4 Photoelectric conversion element 11 1st interlayer insulation film 12 2nd interlayer insulation film 13 3rd interlayer insulation film 14 4th interlayer insulation film 21 1st metal wiring layer 22 2nd Metal wiring layer 23 Third metal wiring layer 24 Incident light limiting film 25 Light-shielding film 31 Protective film 32 Inner lens 33 First planarizing film 34 Color filter film 35 Second planarizing film 36 Microlens 104 First metal wiring layer 105 Second metal wiring layer 106 Third metal wiring layer 107 Protective film 108 In-layer lens 109 Flattening film 110 Color filter layer 111 Microlens

Claims (10)

A semiconductor substrate having a photoelectric conversion element formed on a main surface and having a light receiving pixel region, a boundary pixel region, and a light shielding pixel region;
An interlayer insulating film formed on the semiconductor substrate;
A wiring layer formed on the interlayer insulating film;
A first inner lens formed on the interlayer insulating film in the light receiving pixel region;
A first incident light limiting film formed on the interlayer insulating film in the boundary pixel region;
A light shielding film formed on the interlayer insulating film in the light shielding pixel region,
The boundary pixel region is formed between a light-receiving pixel region and the light-shielding pixel region.   The solid-state imaging device according to claim 1, further comprising a second intra-layer lens on the interlayer insulating film in the boundary pixel region.   The solid-state imaging device according to claim 1, further comprising a second incident light limiting film on the interlayer insulating film in the light-shielding pixel region.   The solid-state imaging device according to claim 1, wherein the wiring layer, the first incident light limiting film, and the second incident light limiting film are made of the same material.   The solid-state imaging device according to claim 1, further comprising a color filter on the interlayer insulating film in the light receiving pixel region.   The solid-state imaging device according to claim 1, further comprising a microlens on the interlayer insulating film in the light receiving pixel region.   The solid-state imaging device according to claim 1, further comprising a contact pad for connecting to the outside, wherein the light shielding film and the contact pad are formed of the same material.   8. The solid-state imaging device according to claim 1, wherein a bottom surface of the first in-layer lens is lower than an upper surface of the light shielding film. Forming a photoelectric conversion element on a semiconductor substrate having a light receiving pixel region, a boundary pixel region, and a light shielding pixel region;
Forming an interlayer insulating film on the semiconductor substrate;
Forming a wiring layer on the interlayer insulating film;
Forming an incident light limiting film on the interlayer insulating film in the boundary pixel region;
Forming a light shielding film on the interlayer insulating film in the light shielding pixel region;
And a step of forming an intra-layer lens on the interlayer insulating film in the light-receiving pixel region.   The method for manufacturing a solid-state imaging device according to claim 9, wherein the wiring layer forming step and the incident light limiting film forming step are performed simultaneously.

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