JP2004241524A - Solid-state imaging device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the uniformity of a color and sensitivity in the periphery of an effective pixel region by reducing a difference in level between the effective pixel region and an OPB pixel region. <P>SOLUTION: On transfer electrodes 11, first light shielding films 12 and 13 are formed. Then, an insulation film 14 is formed, and thereafter, a second light shielding film 15 and a flattening film 16 of the OPB pixel region are formed sequentially. At that time, after forming the insulation film 14, the insulation film 14 on the OPB pixel region 22 is made thin, and then the second light shielding film 15 is formed on the thinned insulation film 14. Consequently, such a solid-state imaging device can be obtained wherein a difference in level between the top face of the insulation film 14 on the effective pixel region 21 and the top face of the second light shielding film 15 on the OPB pixel region 22 is reduced. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a solid-state imaging device and a method for manufacturing the same, and more particularly, to a solid-state imaging device and an effective black region by reducing a step between an effective pixel region and an optical black (hereinafter, referred to as “OPB”) pixel region. The present invention relates to a solid-state imaging device with improved uniformity of color and sensitivity at a peripheral portion of a pixel region.
[0002]
[Prior art]
FIG. 2 is a plan view of a solid-state imaging device using a CCD (Charge Coupled Device). As shown in FIG. 2, the solid-state imaging device has a structure in which an effective pixel area 21 in which an effective pixel group is arranged is surrounded by an OPB pixel area 22 in which an OPB pixel group is arranged. The solid-state imaging device removes noise components such as dark current by outputting data of the effective pixel region 21 with reference to the OPB pixel region 22.
[0003]
FIG. 3 is a sectional view showing the vicinity of a boundary between an effective pixel area 21 and an OPB pixel area 22 of a conventional solid-state imaging device. In the solid-state imaging device shown in FIG. 3, first light-shielding films 12 and 13 and an insulating film 14 are provided on a transfer electrode 11 of a CCD, and a second light-shielding film 15 is provided on an insulating film 14 in an OPB pixel region 22. Is provided. A flattening film 16 is provided on the insulating film 14 on the effective pixel region 21 and the second light-shielding film 15 on the OPB pixel region, and a color filter 17 and an on-chip lens 18 are further provided thereon. ing. As described above, in the conventional solid-state imaging device, in order to realize the required light-shielding characteristics, the OPB pixel region 22 has two light-shields, the first light-shielding film 13 and the second light-shielding film 15 on the insulating film 14. Covered with membrane.
[0004]
However, when the light shielding films 13 and 15 are provided in the OPB pixel region 22 as shown in FIG. 3, a large level difference occurs between the effective pixel region 21 and the OPB pixel region 22. As a result, the flattening film 16 formed thereafter is not sufficiently flattened, and a step remains. Therefore, in the subsequent resist coating step for forming a protective film and the like, particularly during the formation of the color filter 17, the film thickness of the color filter 17 near the boundary between the effective pixel region 21 and the OPB pixel region 22 due to this step. It will be uneven. The non-uniformity of the film thickness of the color filter 17 causes non-uniformity of color and sensitivity in the peripheral portion of the effective pixel region 21, and depending on the degree, causes imaging failure.
[0005]
As a technique for reducing the level difference between the effective pixel area 21 and the OPB pixel area 22 in order to suppress color and sensitivity non-uniformity in the solid-state imaging device having the double light-shielding film, for example, a technique described in Patent Document 1 is described. Things are known.
[0006]
Patent Literature 1 describes that by providing a dummy pixel between an effective pixel and an OPB pixel, a step of a sensor surface shape due to a doubly provided light-shielding film is made gentler than before. . Thereby, when a color filter is formed on the upper surface of the sensor, it is possible to improve the uniformity of the film thickness of the color filter.
[0007]
[Patent Document 1]
JP-A-5-110045 (paragraph number 0012, FIGS. 1 and 2)
[0008]
[Problems to be solved by the invention]
As described in Patent Literature 1, when a dummy pixel is provided between an effective pixel and an OPB pixel, and the step of the sensor surface shape is absorbed by the dummy pixel, the entire solid-state imaging device is equivalent to the area of the dummy pixel. It gets bigger.
[0009]
Therefore, in the present invention, the color and sensitivity at the periphery of the effective pixel region are reduced by reducing the step between the effective pixel region and the OPB pixel region without providing a dummy pixel between the effective pixel and the OPB pixel. The aim is to improve the uniformity.
[0010]
[Means for Solving the Problems]
The solid-state imaging device according to the present invention is a solid-state imaging device in which a first light-shielding film is formed on a transfer electrode, and an insulating film, a second light-shielding film in an optical black pixel region, and an upper layer film are sequentially formed. The insulating film on the black pixel region is thinned, and a second light-shielding film is formed on the thinned insulating film.
[0011]
In the solid-state imaging device of the present invention, since the second light-shielding film provided on the optical black pixel region is formed on the thinned insulating film, the second light-shielding film is optically connected to the upper surface of the insulating film on the effective pixel region. A step with the upper surface of the second light-shielding film on the black pixel region is reduced.
[0012]
The method of manufacturing a solid-state imaging device according to the present invention is directed to a solid-state imaging device in which a first light-shielding film is formed on a transfer electrode, and an insulating film, a second light-shielding film in an optical black pixel region, and an upper layer film are sequentially formed. In the manufacturing method, after forming the insulating film, the insulating film on the optical black pixel region is thinned, and a second light-shielding film is formed on the thinned insulating film.
[0013]
According to the method for manufacturing a solid-state imaging device of the present invention, after the insulating film on the optical black pixel region is thinned, the second light-shielding film is formed on the thinned insulating film. A solid-state imaging device in which a step between the upper surface of the insulating film on the pixel region and the upper surface of the second light-shielding film on the optical black pixel region is reduced is obtained.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a cross-sectional view near a boundary between an effective pixel region and an OPB pixel region of a solid-state imaging device according to an embodiment of the present invention.
[0015]
As shown in FIG. 1, in the solid-state imaging device according to the present embodiment, first light-shielding films 12 and 13 and an insulating film 14 are provided on a transfer electrode 11 of a CCD, and further on an insulating film 14 in an OPB pixel region 22. A second light shielding film 15 is provided. The difference from the conventional example shown in FIG. 3 is that the insulating film 14 on the OPB pixel area 22 except on the effective pixel area 21, that is, under the second light-shielding film 15 is thinned. The second light-shielding film 15 is formed on the thinned insulating film 14.
[0016]
The thinning of the insulating film 14 on the OPB pixel region 22 is performed by forming the insulating film 14, masking the effective pixel region 21 with a photoresist, and dry-etching the insulating film 14 on the OPB pixel region 22. However, when the first light-shielding film 13 in the OPB pixel region 22 is etched, the light-shielding ability of the OPB pixel region 22 is reduced. To be etched.
[0017]
As described above, by thinning the insulating film 14 only on the OPB pixel region 22 except on the effective pixel region 21, the upper surface of the insulating film 14 on the effective pixel region 21 and the second light shielding film on the OPB pixel region 22 are reduced. The step with respect to the upper surface of the insulating film 15 can be reduced by an amount corresponding to the thinning amount of the insulating film 14. Therefore, the planarization film 16 as an upper layer film formed on the insulating film 14 on the effective pixel region 21 and the second light-shielding film 15 on the OPB pixel region can be sufficiently planarized thereafter. . Thereby, the sensitivity unevenness due to the unevenness of the thickness of the flattening film 16 is reduced.
[0018]
In addition, it is possible to make the film thickness uniform in a resist coating process for forming a protective film or the like as an upper layer film on the flattening film 16. In particular, when the color filter 17 is formed as the upper layer film, the color filter 17 becomes uniform, and the color and sensitivity at the periphery of the effective pixel region 21 become uniform. Uniform color unevenness and sensitivity unevenness are reduced.
[0019]
Further, as shown in FIG. 1, even when the on-chip lens 18 is formed on the color filter 17, since the flattening film 16 is sufficiently flattened, the on-chip lens formed on the color filter 17 is formed. 18 is prevented from being deformed. As a result, unevenness in sensitivity due to deformation of the on-chip lens 18 is prevented.
[0020]
In the present embodiment, a method using dry etching has been described as a method for thinning the insulating film 14, but it is also possible to perform wet etching, grinding, polishing, or the like. In short, any method can be used as long as the insulating film 14 on the OPB pixel region 22 can be thinned while securing a remaining film margin not to be cut down to the first light shielding film 13 in the OPB pixel region 22.
[0021]
In the present embodiment, the planarization film 16 and the color filter 17 have been described as an example of the upper layer film. However, the upper layer formed on the insulating film 14 on the effective pixel region 21 and the light shielding film 15 on the OPB pixel region is described. The membrane is not limited to these.
[0022]
【The invention's effect】
According to the present invention, the following effects can be obtained.
[0023]
(1) Since the insulating film on the optical black pixel region is thinned and the second light-shielding film is formed on the thinned insulating film, a dummy pixel is provided between the effective pixel and the OPB pixel. Can be provided, the level difference between the effective pixel area and the OPB pixel area can be reduced, and the uniformity of color and sensitivity at the periphery of the effective pixel area can be improved.
[0024]
(2) When a color filter is provided on the upper layer film in which the step between the effective pixel region and the OPB pixel region is reduced, the film thickness of the color filter becomes uniform, and color unevenness due to the non-uniform film thickness of the color filter and Sensitivity unevenness can be reduced.
[0025]
(3) When the on-chip lens is provided on the upper layer film in which the step between the effective pixel area and the OPB pixel area is reduced, the deformation of the on-chip lens is prevented, so that the sensitivity unevenness due to the deformation of the on-chip lens occurs. Is prevented.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view near a boundary between an effective pixel region and an OPB pixel region of a solid-state imaging device according to an embodiment of the present invention.
FIG. 2 is a plan view of a solid-state imaging device using a CCD.
FIG. 3 is a cross-sectional view near a boundary between an effective pixel area and an OPB pixel area of a conventional solid-state imaging device.
[Explanation of symbols]
Reference Signs List 11 transfer electrodes 12, 13 first light shielding film 14 insulating film 15 second light shielding film 16 flattening film 17 color filter 18 on-chip lens 21 effective pixel area 22 OPB (optical black) pixel area

Claims (4)

In a solid-state imaging device, a first light-shielding film is formed on a transfer electrode, and an insulating film, a second light-shielding film in an optical black pixel region, and an upper film are sequentially formed.
A solid-state imaging device, wherein an insulating film on the optical black pixel region is thinned, and the second light-shielding film is formed on the thinned insulating film. The solid-state imaging device according to claim 1, further comprising a color filter on the upper layer film. The solid-state imaging device according to claim 1, further comprising an on-chip lens on the upper layer film. In a method for manufacturing a solid-state imaging device, a first light-shielding film is formed on a transfer electrode, and an insulating film, a second light-shielding film in an optical black pixel region, and an upper layer film are sequentially formed.
After the formation of the insulating film, the insulating film on the optical black pixel region is thinned,
A method for manufacturing a solid-state imaging device, comprising forming the second light-shielding film on the thinned insulating film.

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