JP2011205031A - Solid-state imaging device and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid-state imaging device structured to prevent characteristic degradation and simultaneously suppressing the occurrence of smear.SOLUTION: The solid-state imaging device includes: a semiconductor substrate 1 having a plurality of transferring channel regions 3 and a plurality of light receiving portions 9 that extend in a vertical direction in proximity to the surface thereof; a plurality of vertical transferring electrodes 11a formed on the semiconductor substrate 1 to cover the plurality of transferring channel regions 3; and light shielding films 13 formed to cover the top of the plurality of vertical transferring electrodes 11a and to open the top of the plurality of light receiving portions 9. The plurality of transferring channel regions 3 are formed such that at least part of them is located in a higher position than the plurality of light receiving portions 9.

Description

  The technology disclosed in the present invention relates to a solid-state imaging device such as a charge-coupled device (CCD) type solid-state imaging device and a manufacturing method thereof. In particular, the present invention relates to a solid-state imaging device having a structure capable of suppressing the occurrence of smear and a manufacturing method thereof.

  Conventionally, CCD type solid-state imaging devices have been widely used as a kind of solid-state imaging device. As a CCD type solid-state imaging device, an interline transfer type having a structure in which a plurality of light receiving portions are formed in a matrix on a semiconductor substrate and each vertical transfer register is provided corresponding to each vertical column of the light receiving portions, etc. A solid-state imaging device is known.

JP-A-10-144907

  Such a conventional CCD type solid-state imaging device has the following problems.

  That is, in the CCD type solid-state imaging device for a small digital still camera which is currently mainstream, with the miniaturization of the solid-state imaging device and the increase in pixel density, for example, the sun emits very strong light like the sun So that smear is likely to occur. This is because the transfer channel is located at the same depth adjacent to the light receiving portion, so that charges generated in a region other than the light receiving portion due to the incidence of light easily reach the transfer channel. In order to suppress the occurrence of such smear, measures such as reducing the size of the opening that exposes the pixel are taken, but reducing the size of the opening, on the other hand, lowering the sensitivity, etc. This leads to deterioration of characteristics.

  In view of the above, an object of the present invention is to provide a solid-state imaging device having a structure capable of suppressing the occurrence of smear while preventing characteristic deterioration, and a method for manufacturing the same.

  In order to achieve the above object, a solid-state imaging device according to one aspect of the present invention is provided with a plurality of transfer channel regions each extending in the vertical direction in the vicinity of the surface and provided in a matrix in a manner spaced from each other. A semiconductor substrate having a plurality of light receiving portions provided adjacent to each of the plurality of transfer channel regions, and a plurality of vertical transfer electrodes formed on the semiconductor substrate so as to cover each of the plurality of transfer channel regions And a light shielding film formed so as to cover each of the plurality of vertical transfer electrodes and to open each of the plurality of light receiving portions, and each of the plurality of transfer channel regions includes at least one of them. The part is formed so as to be positioned above each of the plurality of light receiving parts.

  As described above, each of the plurality of transfer channel regions is formed so that at least a part thereof is positioned above each of the plurality of light receiving units, and therefore, charges are generated in regions other than the light receiving unit due to the incidence of light. It is possible to increase the distance between the region where the occurrence occurs and the transfer channel region. For this reason, for example, the light generated in the region other than the light receiving portion in the semiconductor substrate due to obliquely incident light or the like is suppressed from entering the transfer channel region, and smear is suppressed.

  In the solid-state imaging device according to one aspect of the present invention, each of the plurality of vertical transfer electrodes may surround each side surface and upper surface of the plurality of transfer channel regions in a U-shaped cross-section.

  Thus, since the transfer channel region is three-dimensionally surrounded by the U-shaped vertical transfer electrode, the transfer channel is compared with the case where the transfer channel region is covered with a normal planar vertical transfer electrode. The area that functions as effectively increases. Thus, the sensitivity can be improved by increasing the area of the light receiving portion, as much as the area of the transfer channel region can be reduced.

  In the solid-state imaging device according to one aspect of the present invention, the light shielding unit may surround each side surface and upper surface of the plurality of transfer channel regions in a U-shaped cross-sectional shape.

  Thus, since the transfer channel region is three-dimensionally surrounded by the light shielding film in a U shape, incident light from the oblique direction to the transfer channel region is blocked. As a result, the occurrence of smear can be suppressed. Furthermore, since the side wall portion of the light shielding film also functions as a waveguide for guiding incident light to the light receiving portion, the light collection efficiency on the light receiving portion is increased. As a result, sensitivity is improved.

  In the solid-state imaging device according to one aspect of the present invention, a gate insulating film may be formed between each of the plurality of transfer channel regions and each of the plurality of vertical transfer electrodes.

  In the solid-state imaging device according to one aspect of the present invention, a transparent insulating film may be formed between each of the plurality of vertical transfer electrodes and the light shielding film and on the plurality of light receiving portions.

  According to the solid-state imaging device and the manufacturing method thereof according to one aspect of the present invention, it is possible to suppress smear while preventing a decrease in sensitivity. In addition, a layout with high area efficiency is possible, and the solid-state imaging device can be downsized.

FIG. 1 is a plan view showing the structure of a solid-state imaging device according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing the structure of the solid-state imaging device according to the embodiment of the present invention. Specifically, FIG. 2 is an enlarged cross-sectional view corresponding to the line II-II in FIG. FIG. 3 is a cross-sectional view showing the structure of the solid-state imaging device according to the embodiment of the present invention. Specifically, FIG. 3 is an enlarged cross-sectional view corresponding to line III-III in FIG. 4A and 4B are cross-sectional views illustrating a method for manufacturing a solid-state imaging device according to an embodiment of the present invention in the order of steps, specifically, in a cross section corresponding to the cross-sectional view of FIG. It is process sectional drawing. 5 (a) and 5 (b) are cross-sectional views illustrating a method for manufacturing a solid-state imaging device according to an embodiment of the present invention in the order of steps, specifically, in a cross section corresponding to the cross-sectional view of FIG. It is process sectional drawing. 6A and 6B are cross-sectional views illustrating the method of manufacturing the solid-state imaging device according to the embodiment of the present invention in the order of steps, specifically, in a cross section corresponding to the cross-sectional view of FIG. It is process sectional drawing. 7A and 7B are cross-sectional views illustrating the method of manufacturing the solid-state imaging device according to the embodiment of the present invention in the order of steps, specifically, in a cross section corresponding to the cross-sectional view of FIG. It is process sectional drawing.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following, the technical idea of the present invention will be clearly described with reference to the drawings and detailed description. Any person skilled in the art will understand the preferred embodiment of the present invention, and Modifications and additions can be made by the technology disclosed in the invention, and this does not depart from the technical idea and scope of the present invention.

  First, the structure of a semiconductor device according to an embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 shows a planar structure of a solid-state imaging device according to an embodiment of the present invention.

  As shown in FIG. 1, in the vicinity of the surface of the semiconductor substrate 1, a plurality of light receiving portions 9 are formed in a matrix (vertical direction (column direction) and horizontal direction (row direction)) at intervals from each other. A transfer channel region 3 is formed between the plurality of light receiving portions 9 arranged in the vertical direction so as to extend in the vertical direction, and the transfer channel region 3 is formed in the gate insulating film 10 (not shown in FIG. 1). Vertical transfer electrodes 11a and 11b are formed alternately in the vertical direction at intervals from each other. The transfer channel region 3, the gate insulating film 10, and the vertical transfer electrodes 11a and 11b constitute a vertical transfer register 18 having a CCD structure. Further, an interlayer insulating film 12 is formed on the entire surface of the semiconductor substrate 1 so as to cover the vertical transfer electrodes 11a and 11b and the top and bottom surfaces of the vertical transfer electrodes 11a and 11b as shown in the figure. Further, a light shielding film 13 is formed on the interlayer insulating film 12 so as to cover the vertical transfer register 18 while opening the upper part of each of the plurality of light receiving portions 9 through the interlayer insulating film 12. 1 shows a state in which up to the light-shielding film 13 is formed on the semiconductor substrate 1 for convenience of explanation, and components shown in FIGS. 2 and 3 to be described in detail later are omitted as appropriate. ing.

  2 and 3 are structural cross-sectional views of the solid-state imaging device according to the embodiment of the present invention. FIG. 2 is an enlarged view corresponding to the line II-II in FIG. FIG. 2 shows an enlarged cross section corresponding to the line III-III in FIG.

  As shown in FIGS. 2 and 3, a second conductivity type, for example, p-type semiconductor well region 2 is formed on a semiconductor substrate 1 made of a first conductivity type, for example, n-type silicon. As shown in FIG. 2, an n-type impurity diffusion region 7 is formed in the p-type semiconductor well region 2, and a p-type positive charge accumulation region is formed on the n-type impurity diffusion region 7. 8 is formed. Here, a light receiving portion (photoelectric conversion portion) 9 is constituted by a photodiode PD formed by a pn junction between the p-type semiconductor well region 2 and the n-type impurity diffusion region 7, and the light receiving portion 9 corresponds to a pixel. It is formed as follows.

  As shown in FIGS. 2 and 3, an n-type transfer channel region 3 constituting the vertical transfer register 18 extending in the column direction is formed on the p-type semiconductor well region 2. A p-type semiconductor well region 4 having an impurity concentration higher than that of the p-type semiconductor well region 2 is formed immediately below the n-type transfer channel region 3. Here, the transfer channel region 3 is formed so that a part of the transfer channel region 3 is located above the semiconductor substrate 1 relative to the light receiving portion 9. However, the transfer channel region 3 may be formed so as to be located above the semiconductor substrate 1 with respect to the light receiving portion 9. In addition, as shown in FIG. 2, in the region between the vertical transfer register 18 and each light receiving unit 9 on the n-type semiconductor well region 2, a p-type channel stop region 5 is provided on one side of the vertical transfer register 18. The p-type low-concentration read gate region 6 is formed on the other side.

As shown in FIGS. 2 and 3, on the transfer channel region 3, the p-type channel stop region 5 and the p-type low-concentration read gate region 6 constituting the vertical transfer register 18, for example, silicon A gate insulating film 10 made of an oxide (SiO ₂ ) film or a silicon nitride (SiN) film is formed. Instead of the gate insulating film 10, a so-called ONO film having a structure in which an oxide film, a nitride film, and an oxide film are stacked in this order can also be formed.

  Further, as shown in FIGS. 2 and 3, on the gate insulating film 10, vertical transfer electrodes 11a and 11b made of, for example, a polycrystalline silicon layer are formed so as to be arranged in the vertical direction at intervals from each other. An interlayer insulating film (transparent insulating film) made of a transparent insulating film material such as a silicon oxide film or a silicon nitride film so as to cover the upper surface and side surfaces of each of the vertical transfer electrodes 11a and 11b on the entire surface of the semiconductor substrate 1 12 is formed. Here, as shown in FIG. 2, the side surface and the upper surface of the transfer channel region 3 are covered with a vertical transfer electrode 11a having a U-shaped cross section. The transfer channel 3, the gate insulating film 10, and the vertical transfer electrodes 11a and 11b constitute a vertical transfer register 18 having a CCD structure. Further, for example, tungsten (W) or aluminum (Al) is formed on the interlayer insulating film 12 so as to open the upper part of each of the plurality of light receiving portions 9 through the interlayer insulating film 12 and cover the vertical transfer register 18. A light shielding film 13 made of a metal film such as) is formed. Here, as shown in FIG. 2, the side surface and the upper surface of the transfer channel region 3 are covered with a light shielding film 13 having a U-shaped cross-section.

  Further, as shown in FIGS. 2 and 3, an interlayer insulating film 14 made of, for example, a BPSG film so as to cover the interlayer insulating film 12 and the light shielding film 13 on the entire surface of the semiconductor substrate 1, and the interlayer insulating film A high refractive index film 15 having a refractive index higher than 14 is formed in this order. The interlayer insulating film 14 and the high refractive index film 15 constitute an inner lens. Further, as shown in FIG. 2, a color filter 16 and an on-chip lens 17 are formed on the high refractive index film 15.

  Next, a method for manufacturing a semiconductor device according to an embodiment of the present invention will be described with reference to FIGS. 4 (a) and (b), FIG. 5 (a) and (b), FIG. 6 (a) and (b), and FIG. 7 (a) and (b) are solids according to an embodiment of the present invention. It is sectional drawing which shows the manufacturing method of an image pick-up element in process order, Comprising: Specifically, the process cross section in the cross section corresponding to sectional drawing of FIG. 2 is shown.

  First, as shown in FIG. 4A, after a p-type semiconductor well region 2 is formed in a semiconductor substrate 1 made of a first conductivity type, for example, n-type silicon, an upper portion in the p-type semiconductor well region 2 is formed. Then, an n-type semiconductor region 3a constituting a transfer channel region 3 described later is formed.

  Next, as shown in FIG. 4B, a patterned n-type semiconductor region 3b is formed by using a photolithography method, a dry etching technique, or the like.

  Next, as shown in FIG. 5A, the n-type impurity diffusion region 7 and the p-type are formed in the p-type semiconductor well region 2 or the n-type semiconductor region 3b by using a photolithography method, an ion implantation method, or the like. A positive positive charge accumulation region 8, a p-type semiconductor well region 4, a channel stop region 5, and a read gate region 6 are formed. As a result, the transfer channel region 3 made of an n-type semiconductor region and constituting the transfer register 18 described above is formed. The n-type impurity diffusion region 7 and the p-type positive charge accumulation region 8 constitute a light receiving portion 9. Thus, the transfer channel region 3 is formed so that a part thereof is located above the semiconductor substrate 1 relative to the light receiving portion 9. However, the transfer channel region 3 may be formed so as to be located above the semiconductor substrate 1 with respect to the light receiving portion 9. The p-type semiconductor well region 4 is formed so that its concentration is higher than that of the p-type semiconductor well region 2, and the channel stop region 5 is higher in concentration than the read gate region 6. Formed to be.

  Next, as shown in FIG. 5B, a silicon oxide film or a silicon nitride film is formed on the entire surface of the semiconductor substrate 1 so as to cover the transfer channel region 3 by using a thermal oxidation method or a CVD method. A gate insulating film 10 is formed. Instead of the gate insulating film 10, a so-called ONO film having a structure in which an oxide film, a nitride film, and an oxide film are stacked in this order can also be formed. Subsequently, a polycrystalline silicon film 11c constituting vertical transfer electrodes 11a and 11b described later is deposited on the gate insulating film 10 by using a CVD method or the like. A metal film such as tungsten can also be used instead of the polycrystalline silicon film 11c.

  Next, as shown in FIG. 6A, the portions of the polycrystalline silicon film 11c and the gate insulating film 10 on the light receiving portion 9 are removed by using a photolithography method, a dry etching technique, etc. 11a is formed. Although not shown, the vertical transfer electrode 11b shown in FIGS. 1 and 3 is also formed in this step. In this way, as shown in FIG. 6A, the side surface and the upper surface of the transfer channel region 3 are covered with the vertical transfer electrode 11a or 11b having a U-shaped cross section.

  Next, as shown in FIG. 6B, a transparent insulating film such as a silicon oxide film or a silicon nitride film is formed on the entire surface of the semiconductor substrate 1 so as to cover the vertical transfer electrode 11a by using a CVD method or the like. An interlayer insulating film 12 made of a material is formed, and then a light shielding film 13 made of a metal film such as tungsten (W) or aluminum (Al) is formed.

  Next, as shown in FIG. 7A, using the photolithography method, the dry etching technique, or the like, the portion of the light shielding film 13 on the light receiving portion 9 is removed, and the upper surface of the light receiving portion 7 is made to be the interlayer insulating film 12. Open through. In this way, as shown in FIG. 6B, the upper surface and the side surface of the transfer channel region 3 are covered with the light shielding film 13 having a U-shaped cross section. Although not shown in the figure after performing a simple heat treatment, there are a case where a process for processing the wiring around the imaging element is inserted as a wiring forming process and a case where the light shielding film 13 is used as a wiring part as it is. is there.

  Next, as shown in FIG. 7B, an interlayer insulating film 14 made of, for example, a BPSG film is formed on the entire surface of the semiconductor substrate 1 so as to cover the interlayer insulating film 12 and the light shielding film 13, and then A high refractive index film 15 having a refractive index higher than that of the interlayer insulating film 14 is formed on the interlayer insulating film 14. Thereafter, a photoresist film is formed on the high-refractive index film 15, and the high-refractive index film 15 and the photoresist film are etched back to form an in-layer lens composed of the interlayer insulating film 14 and the high-refractive index film 15. To do. Thereafter, the color filter 16 and the on-chip lens 17 are formed by a known method.

  In this way, the solid-state imaging device according to the embodiment of the present invention shown in FIGS. 1, 2, and 3 is manufactured.

  As described above, according to the solid-state imaging device and the manufacturing method thereof according to the embodiment of the present invention, a part of the transfer channel region 3 is positioned above the semiconductor substrate 1 relative to the light receiving unit 9. For this reason, the distance between the region where charges are generated in the region other than the light receiving unit 9 and the transfer channel region 3 due to the incidence of light increases. Therefore, for example, charges generated in the p-type semiconductor well region 2 below the p-type semiconductor well region 4 due to light incident obliquely or the like, for example, below the p-type semiconductor well region 4 are transferred to the transfer channel region 3. And the occurrence of smear is suppressed.

  Further, the upper surface and the side surface of the transfer channel region 3 are covered with vertical transfer electrodes 11a and 11b having a U-shaped cross section. Thus, since the transfer channel region 3 is three-dimensionally surrounded by the vertical transfer electrodes 11a and 11b in a U-shape, the transfer channel region 3 is covered with a normal planar vertical transfer electrode. Thus, the area functioning as a transfer channel is effectively increased. As a result, when the planar area of the transfer channel region 3 is assumed to be constant, a larger amount of charge can be transferred than when the transfer channel region 3 is covered with a normal planar vertical transfer electrode. it can. Therefore, the sensitivity can be improved by increasing the area (region) of the light receiving section 9 by the amount that the area (region) of the transfer channel region 3 can be reduced.

  Further, the side surface and the upper surface of the transfer channel region 3 are covered with a light shielding film 13 having a U-shaped cross-section. Thus, since the transfer channel region 3 is surrounded by the light shielding film 13 in a U shape, incident light from the oblique direction to the transfer channel region 3 is blocked. As a result, the occurrence of smear can be suppressed.

  Further, the light shielding film 13 has a side wall portion that also functions as a waveguide that guides incident light to the light receiving unit 9, so that the light collection efficiency on the light receiving unit 9 is increased. As a result, sensitivity is improved.

  As described above, according to the solid-state imaging device and the manufacturing method thereof according to the embodiment of the present invention, it is possible to realize a good image quality by improving the sensitivity while suppressing the occurrence of smear, and to achieve a layout with high area efficiency. This makes it possible to reduce the size of the solid-state imaging device.

  INDUSTRIAL APPLICABILITY The present invention is useful for a structure of a solid-state imaging device that can suppress smear while preventing a decrease in sensitivity and a manufacturing method thereof.

1 semiconductor substrate 2 p-type semiconductor well region 3 transfer channel region 4 p-type semiconductor well region 5 channel stop region 6 read gate region 7 impurity diffusion region 8 positive charge storage region 9 light receiving unit 10 gate insulating films 11a and 11b vertical transfer Electrode 12 Interlayer insulation film (transparent insulation film)
13 light shielding film 14 interlayer insulating film 15 high refractive index film 16 color filter 17 on-chip lens 18 vertical transfer register

Claims (5)

A plurality of transfer channel regions each extending in the vertical direction in the vicinity of the surface, and a plurality of light receiving portions provided adjacent to each of the plurality of transfer channel regions and spaced apart from each other in a matrix. A semiconductor substrate having,
A plurality of vertical transfer electrodes formed on the semiconductor substrate so as to cover each of the plurality of transfer channel regions;
A light-shielding film that covers each of the plurality of vertical transfer electrodes and is formed so as to open each of the plurality of light-receiving portions.
Each of the plurality of transfer channel regions is a solid-state imaging device formed so that at least a part thereof is positioned above each of the plurality of light receiving units. The solid-state imaging device according to claim 1,
Each of the plurality of vertical transfer electrodes surrounds a side surface and an upper surface of each of the plurality of transfer channel regions in a U-shaped cross section. The solid-state imaging device according to claim 1 or 2,
The solid-state imaging device, wherein the light shielding portion surrounds a side surface and an upper surface of each of the plurality of transfer channel regions in a U-shaped cross section. The solid-state imaging device according to any one of claims 1 to 3,
A solid-state imaging device, wherein a gate insulating film is formed between each of the plurality of transfer channel regions and each of the plurality of vertical transfer electrodes. The solid-state imaging device according to any one of claims 1 to 3,
A solid-state imaging device, wherein a transparent insulating film is formed between each of the plurality of vertical transfer electrodes and the light shielding film and on the plurality of light receiving portions.

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