JP2004273827A - Solid-state imaging apparatus and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid-state imaging apparatus which can be miniaturized and whose sensibility can be enhanced by improving the light condensing rate, and a manufacturing method of the imaging apparatus. <P>SOLUTION: The solid-state imaging apparatus is provided with a photodiode 2 and a CCD channel 3 which are formed on a semiconductor board 1, gate electrodes 5a, 5b which are formed above the CCD channel 3 via a gate insulating film 4, a flattening layer 7 covering the gate electrodes 5a, 5b, an upward convex micro lens 8 formed on the flattening layer 7, and a shading film 6b formed to avoid the area of the micro lens 8. Since the shading film 6b is formed to cover the area above the micro lens 8 other than that of the micro lens 8, incident light passing through an opening between adjacent shading films 6b is condensed by the micro lens 8, and falls upon the photodiode 2. As a result, reflection losses caused by the shading film thickness is eliminated, thus enhancing incident light to improve a sensibility characteristic without deteriorating a smear characteristic in the apparatus. <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.
[0002]
[Prior art]
The solid-state imaging device includes a lens unit that collects incident light, a light receiving unit that performs photoelectric conversion of the incident light, and a charge transfer unit that transfers charges. In a recent solid-state image sensor, the demand for higher resolution and a larger number of pixels has led to further miniaturization of cells, while sensitivity characteristics have been required to be at the same level as before. Along with this, the light-collecting property becomes insufficient only with the on-chip lens, and a technique for increasing the light-collecting property by further forming a microlens at a position close to the light receiving section (fod diode) is used.
[0003]
FIG. 7 is a schematic cross-sectional view of this type of conventional solid-state imaging device, FIG. 8 is a schematic plan view, and FIG. 9 is a schematic cross-sectional view of a manufacturing process. On a p-type silicon substrate 1, an n-type impurity region 2 (hereinafter referred to as a photodiode) as a charge storage portion (light receiving portion) and an n-type impurity region 3 (hereinafter referred to as a CCD channel) as a charge transfer portion are formed. ing. First gate electrodes 5a and second gate electrodes 5b, which are charge transfer electrodes, are alternately arranged along the charge transfer direction with the gate insulating film 4 interposed therebetween. The light-shielding film 6 is patterned so as to cover the first gate electrode 5a and the second gate electrode 5b via the gate insulating film 4a. A first planarization layer 7 is formed on a light-shielding film (metal film) 6 (FIG. 9A), and a convex microlens 8 is formed on the first planarization layer 7 (FIG. 9 (A)). b)). A second planarization layer 9 made of an acrylic resin is formed on the convex microlens 8 and planarized, and a color filter 10 is formed thereon. Further, an on-chip lens 11 is formed on the color filter 10 (FIG. 9C). The on-chip lens 11 and the microlens 8 can enhance the light collecting property. a7, b7, c7, and d7 indicate paths of incident light.
[0004]
[Patent Document]
JP-A-6-204443
[Problems to be solved by the invention]
However, in the above-described structure that has been conventionally proposed, when the cell size is reduced, the reflection loss due to the light b7 obliquely incident on the light-shielding film 6 increases, which hinders an increase in sensitivity. Here, since the light-shielding film thickness is determined by the light-shielding property of the incident light a7 incident from above the CCD channel, if it is simply made thin, a transmitted light component enters the CCD channel and becomes a pseudo signal (smear). Therefore, if the cell size is reduced and the opening width L7 is reduced when the light-shielding film thickness is constant, the aspect ratio of the light-shielding film thickness to the opening width L7 increases, and the condensing rate for oblique light b7 decreases. In particular, in the structure using the micro lens 8, the oblique light b7 of the incident light increases, so that the incident light b7 incident on the light-shielding film 6 in the opening is vignetted by the light-shielding film 6, thereby reducing the light collection rate. descend. To increase the sensitivity, it is conceivable to increase the opening width L7. However, a simple increase in the opening width L7 increases the number of pseudo signals entering the CCD channel and deteriorates smear.
[0006]
Accordingly, it is an object of the present invention to provide a solid-state imaging device capable of reducing the size, improving the light-collecting efficiency, and increasing the sensitivity, and a method of manufacturing the same.
[0007]
[Means for Solving the Problems]
2. The solid-state imaging device according to claim 1, wherein a charge storage unit and a charge transfer unit are formed on the semiconductor substrate; a charge transfer electrode is formed above the charge transfer unit via a gate insulating film; , A convex microlens formed on the flattening layer, and a light shielding film formed except for the region of the microlens.
[0008]
According to the solid-state imaging device of the first aspect, since the incident light that has passed between the light-shielding films is condensed by the lens and enters the charge accumulating portion, the reflection loss due to the light-shielding film thickness can be eliminated as compared with the related art. In addition, the incident light can be increased to improve the sensitivity characteristics. Further, since the light directly incident on the charge transfer unit can be reduced, it is possible to prevent the smear characteristic from deteriorating. Further, since the distance between the charge storage portion and the lens can be reduced, the light collection rate can be increased, and the sensitivity can be improved.
[0009]
According to a second aspect of the present invention, in the solid-state imaging device according to the first aspect, a side surface light-shielding film is provided on a side wall of the charge transfer electrode.
[0010]
According to the solid-state imaging device of the second aspect, in addition to the same effect as the first aspect, by providing a sidewall of a metal film, for example, on the side wall of the charge transfer electrode, it is possible to further suppress irregular reflection components that enter the charge transfer portion, Sensitivity can be improved without deteriorating smear characteristics.
[0011]
4. The method for manufacturing a solid-state imaging device according to claim 3, wherein a charge storage unit and a charge transfer unit are formed on a semiconductor substrate, and a charge transfer electrode is formed above the charge transfer unit via a gate insulating film; Forming a flattening layer after forming the charge transfer electrode, forming an upwardly convex microlens on the flattening layer, and forming a light-shielding film excluding the microlens region after forming the microlens And
[0012]
According to the method of manufacturing a solid-state imaging device according to the third aspect, the same effect as that of the first aspect can be obtained.
[0013]
According to a fourth aspect of the present invention, in the method for manufacturing a solid-state imaging device according to the third aspect, after forming the charge transfer electrode, a metal film is formed via an insulating film formed to cover the charge transfer electrode. This includes a step of forming a sidewall by anisotropic etching.
[0014]
According to the method for manufacturing a solid-state imaging device according to the fourth aspect, a flattening layer is formed thereafter, an upwardly convex microlens is provided on the flattening layer, and the microlens is formed above the microlens except for the microlens. By providing the light-shielding film, the same effect as that of the second aspect can be obtained.
[0015]
According to a fifth aspect of the present invention, in the method of manufacturing a solid-state imaging device according to the third or fourth aspect, the light-shielding film is formed immediately after the formation of the upwardly convex microlens.
[0016]
According to the method of manufacturing a solid-state imaging device according to the fifth aspect, the same effects as those of the third or fourth aspect can be obtained.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a solid-state imaging device according to a first embodiment of the present invention and a method for manufacturing the same will be described with reference to FIGS. In all the drawings of the embodiments, the same portions are denoted by the same reference numerals.
[0018]
Since the steps up to the formation of the second gate electrode 5b (FIG. 2A) are the same as in the above-described conventional case, the same parts are denoted by the same reference numerals and description thereof is omitted. A first planarization layer 7 is formed to cover the first gate electrode 5a and the second gate electrode 5b, and a convex microlens 8 is formed on the first planarization layer 7 (FIG. 2B). . An insulating film 9a is formed on the convex microlenses 8, and a light-shielding film 6b is formed on the insulating film 9a except for the microlenses 8 (FIG. 2C). Further, a second flattening layer 9b made of an acrylic resin is formed thereon and flattened, and a color filter 10 is formed thereon. Further, an on-chip lens 11 is formed on the color filter 10 (FIG. 2D).
[0019]
Specifically, after the formation of the first gate electrode 5a and the second gate electrode 5b, the first planarization layer 7 is formed on the entire surface using a CVD film. As a method of flattening, there is a method by a CMP (Chemical Mechanical Polish) method or a method of reflowing using a BPSG film as a CVD film. In any case, a low refractive index material whose refractive index of the CVD film is 1.4 to 1.6 is used.
[0020]
Next, a convex microlens 8 made of a SiN film (refractive index: 1.9 to 2.0) is formed by plasma CVD. In the conventional method, the microlens is formed after the formation of the light-shielding film. In the present embodiment, the light-shielding film 6b is formed after the formation of the microlens 8. Thus, the height h1 of the microlens 8 from the position where the gate insulating film 4 is formed can be made smaller than the height h7 of the conventional example. If the distance between the photodiode 2 and the lens 8 can be reduced, the light collecting property can be further improved. Specifically, the thickness can be reduced by 200 to 400 nm corresponding to the thickness of the light shielding film 6b.
[0021]
Next, a CVD insulating film 9a and a light shielding film 6b of a metal film are formed, and the light shielding film 6b is patterned except for the microlenses 8. The CVD insulating film 9a is formed to reduce damage to the microlens 8 due to over-etching during dry etching of the light shielding film 6b, and the CVD insulating film 9a can be omitted depending on etching conditions.
[0022]
The light incident on the microlens 8 can be controlled by the aperture ratio of the light-shielding film 6b (that is, the opening width L1 between the light-shielding films 6b). However, when the light-shielding film 6b and the microlens 8 overlap, the light-collection rate decreases, and When the distance between the light shielding film 6b and the microlens 8 is increased, the effect of shielding the incident light a1 component is reduced and smear is increased. Specifically, it is preferable that the light-shielding film 6b be provided within a region 12 connecting the micro lens 8 and the lens end of the on-chip lens 11. That is, the distance between the microlens 8 and the light shielding film 6b is preferably set to 50 to 300 nm.
[0023]
Next, a second flattening layer 9 made of an acrylic resin (refractive index: 1.3 to 1.6) is formed. Since the refractive index of the convex microlens 8 is larger than that of the acrylic resin, light can be collected as a lens. After the formation of the color filter 10, the on-chip lens 11 is formed. Note that b1, c1, and d1 are incident lights that have entered the on-chip lens 11 and the micro lens 8.
[0024]
A second embodiment of the present invention will be described with reference to FIGS. That is, in the first embodiment, after forming the first gate electrode 5a and the second gate electrode 5b, an insulating film 7a covering these electrodes is formed, and further, a metal film 6a is formed (see FIG. a)), the metal film 6a is anisotropically etched (etched back) to provide side wall light-shielding films on the side of the first gate electrode 5a and the second gate electrode 5b (FIG. 6B). . Thereafter, similarly to the first embodiment, the first planarizing layer 7 and the micro lens 8 are sequentially manufactured (FIGS. 6C and 6D).
[0025]
Light that is irregularly reflected by the sidewalls of the reflective film of the metal film 6a can be blocked, and the smear suppressing effect can be enhanced.
[0026]
The plane pattern of the metal film 6a is shown in FIGS. FIG. 4 shows a case where the micro lens 8 has a semi-cylindrical shape, and FIG. 5 shows a case where the micro lens 8 is circular. The light shielding film 6b is formed outside the micro lens 8. If the light-shielding film 6b is formed inside the microlens 8, the incident light is vignetted by the light-shielding film 6b, so that the light incident on the photodiode 2 itself is reduced and the sensitivity is reduced. It is desirable that the microlens 8 and the light shielding film 6b be separated from each other by 100 nm or more in consideration of the variation in the pattern formation of the metal film 6a.
[0027]
【The invention's effect】
According to the solid-state imaging device of the first aspect, since the incident light that has passed between the light-shielding films is condensed by the lens and enters the charge accumulating portion, the reflection loss due to the light-shielding film thickness can be eliminated as compared with the related art. In addition, the incident light can be increased to improve the sensitivity characteristics. Further, since the light directly incident on the charge transfer unit can be reduced, it is possible to prevent the smear characteristic from deteriorating. Further, since the distance between the charge storage portion and the lens can be reduced, the light collection rate can be increased, and the sensitivity can be improved.
[0028]
According to the solid-state imaging device of the second aspect, in addition to the same effects as those of the first aspect, by providing, for example, a side wall of a metal film on the side wall of the charge transfer electrode, it is possible to further suppress irregular reflection components that enter the charge transfer portion, Sensitivity can be improved without deteriorating smear characteristics.
[0029]
According to the method of manufacturing a solid-state imaging device according to the third aspect, the same effect as that of the first aspect can be obtained.
[0030]
According to the method for manufacturing a solid-state imaging device according to the fourth aspect, a flattening layer is formed thereafter, an upwardly convex microlens is provided on the flattening layer, and the microlens is formed above the microlens except for the microlens. By providing the light-shielding film, the same effect as that of the second aspect can be obtained.
[0031]
According to the method of manufacturing a solid-state imaging device according to the fifth aspect, the same effects as those of the third or fourth aspect can be obtained.
[Brief description of the drawings]
FIG. 1 is a sectional view of a main part of a first embodiment of the present invention.
FIG. 2 is a manufacturing process diagram thereof.
FIG. 3 is a sectional view of a main part of a second embodiment.
FIG. 4 is a plan view in the case where the microlens is in a semi-cylindrical shape.
FIG. 5 is a plan view when a micro lens is circular.
FIG. 6 is a manufacturing process diagram.
FIG. 7 is a sectional view of a main part of a conventional example.
FIG. 8 is a plan view thereof.
FIG. 9 is a manufacturing process diagram.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... p-type silicon substrate 2 ... photodiode 3 ... CCD channel 4, 4a ... gate insulating film 5a ... 1st gate electrode 5b ... 2nd gate electrode 6, 6b ... A light shielding film 6a a metal film 7a an insulating film 7 a first planarizing layer 8 a convex microlens 9a a CVD insulating film 9 a second planarizing layer 10 Color filter 11 On-chip lens 12 Areas a1, b1, c1, d1 Incident light component h1 Microlens height L1 Opening width

Claims (5)

A charge accumulation unit and a charge transfer unit formed on a semiconductor substrate, a charge transfer electrode formed above the charge transfer unit via a gate insulating film, a flattening layer covering the charge transfer electrode, A solid-state imaging device comprising: an upwardly convex microlens formed on a passivation layer; and a light-shielding film formed except for a region of the microlens. The solid-state imaging device according to claim 1, further comprising a side light-shielding film on a side wall of the charge transfer electrode. Forming a charge accumulation portion and a charge transfer portion on a semiconductor substrate, forming a charge transfer electrode over the charge transfer portion via a gate insulating film, and forming a flattening layer after forming the charge transfer electrode; A method for manufacturing a solid-state imaging device, comprising: forming an upwardly convex microlens on the flattening layer; and forming a light-shielding film except for a region of the microlens after the formation of the microlens. 4. The method according to claim 3, further comprising: after forming the charge transfer electrode, forming a metal film via an insulating film formed to cover the charge transfer electrode, and forming a sidewall by anisotropically etching the metal film. Manufacturing method of a solid-state imaging device. The method for manufacturing a solid-state imaging device according to claim 3, wherein the light-shielding film is formed immediately after the formation of the upwardly convex microlenses.

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