JP4535766B2 - Solid-state imaging device, manufacturing method thereof, and electronic information device - Google Patents

Description

  The present invention relates to a solid-state imaging device such as a CCD solid-state imaging device and a method for manufacturing the same, and an electronic information device using the solid-state imaging device for an imaging unit such as a digital still camera, a digital video camera, and a camera-equipped mobile phone.

  This type of solid-state imaging device is required to increase the charge transfer speed in accordance with the recent trend toward higher pixel count. In order to realize these higher pixels and faster charge transfer, it is extremely important to reduce the coupling capacitance between the charge transfer electrodes, to lower the resistance of the charge transfer electrodes, and to make the charge transfer electrodes finer. In addition, with the increase in the number of pixels in a solid-state imaging device, it is also extremely important to reduce smear that causes incident light to leak into the charge transfer region. This conventional solid-state imaging device will be described with reference to FIGS.

  6 is a plan view of an essential part showing a structural example of a conventional CCD type solid-state imaging device, FIG. 7 is a cross-sectional view taken along line AA ′ in FIG. 6, and FIG. 8 is a cross-sectional view taken along line BB ′ in FIG.

  As shown in FIGS. 6 to 8, the CCD solid-state imaging device 10 has a two-layer polysilicon structure, and is read from a photodiode 11 as a photoelectric conversion element on the surface of a semiconductor substrate (not shown) and an adjacent photodiode 11. A charge transfer region 12 for transferring the generated charge, and a first charge transfer electrode 14 and a second charge transfer electrode 15 made of polysilicon provided on the charge transfer region 12 via a gate insulating film 13. An insulating film 16 having an opening 11 a and a light shielding film 17 are provided on the photodiode 11 so as to cover the first charge transfer electrode 14 and the second charge transfer electrode 15.

  The photodiode 11 has a P-type low-concentration impurity region (P-Well) 18 provided on the surface of the semiconductor substrate and an N-type high-concentration impurity layer 19 provided thereon, and a P-type provided on the surface. A buried structure is formed by the type high-concentration impurity layer 20. In this CCD type solid-state image pickup device 10, one having a square lattice arrangement in which photodiodes 11 are arranged in a square lattice shape is widely used.

  An element isolation region 21 is provided on a P-type low-concentration impurity region (P-Well) 18 at the boundary between the photodiodes 11 adjacent to the charge transfer direction (vertical direction in FIG. 6).

  The first charge transfer electrode 14 and the second charge transfer electrode 15 are alternately arranged in the charge transfer direction. On the element isolation region 21, the first charge transfer electrode 14 adjacent to the direction perpendicular to the charge transfer direction and Wiring portions 14a and 15a that electrically connect each of the second charge transfer electrodes 15 are provided. The second charge transfer electrode 15 partially overlaps the first charge transfer electrode 14, and the wiring portion 15 a of the second charge transfer electrode 15 partially overlaps the wiring portion 14 a of the first charge transfer electrode 14. Therefore, a step is formed in each overlapping portion.

  The light shielding film 17 electrically connects the wiring portion 14a that electrically connects the first charge transfer electrodes 14 adjacent in the direction orthogonal to the charge transfer direction and the second charge transfer electrode 15 adjacent in the direction orthogonal to the charge transfer direction. The insulating layer 16 is provided on the wiring portion 15a to be connected electrically, and the light shielding film 17 reflects the step of the overlapping portion between the first charge transfer electrode 14 and the second charge transfer electrode 15. Steps are also formed.

  In the conventional solid-state imaging device 10 configured as described above, the first charge transfer electrode 14 and the second charge transfer electrode 15 are disposed on the element isolation region 21 provided at the vertical boundary portion of each photodiode 11. In order to have a space for the wiring portions 14a and 15a and not sacrifice the sensitivity, it is preferable to reduce the width as much as possible.

  However, if the width of the element isolation region 21 shown in FIG. 8 is narrowed, the widths of the first charge transfer electrode 14 and the second charge transfer electrode 15 made of polysilicon are narrowed, resulting in an increase in electrical resistance. For this reason, in the conventional solid-state imaging device 10, the widths of the wiring portions 14a and 15a of the element isolation region 21 are narrowed, and the first charge transfer electrode 14, the second charge transfer electrode 15, and the wiring portions 14a and 15a thereof. The electrical resistance is lowered by increasing the film thickness.

  However, increasing the thickness of the charge transfer electrode made of polysilicon (hereinafter referred to as polysilicon electrode) hinders microfabrication, and there is a limit to increasing the thickness. In the future, when the number of pixels of the solid-state imaging device increases and the image size increases, the electrical resistance of such a polysilicon electrode becomes a problem, and it becomes difficult to maintain high transfer efficiency during charge transfer.

  In the solid-state imaging device, as a method for reducing the electric resistance of the charge transfer electrode, in addition to increasing the thickness of the polysilicon electrode, the concentration of impurities such as phosphorus or arsenic contained in the polysilicon electrode is set. It is also possible to increase it. However, in this method, even if the concentration is increased beyond the solid solution limit of the impurity, the specific resistance does not decrease. Therefore, as in the case where the thickness of the polysilicon electrode is increased, the solid-state imaging device has a higher pixel and the image size is reduced. There is a limit to cope with increasing size and driving speed.

  Therefore, as another method for reducing the electric resistance of the charge transfer electrode, for example, Patent Document 1 proposes a structure in which a backing metal wiring (so-called metal backing) is provided on a polysilicon electrode. For example, when a backing metal wiring is provided in a CCD type solid-state imaging device, the metal wiring is extended in the vertical direction above the vertical charge transfer region, and the metal wiring and the polysilicon electrode of each layer are electrically connected via a contact hole. It is designed to have a connected structure.

  By the way, in the CCD type solid-state imaging device, the charge transfer electrode is usually configured by using two polysilicon layers or three polysilicon layers as shown in FIGS. At this time, the level difference becomes large in the overlapping portion of the polysilicon electrodes (charge transfer electrodes and their wiring portions). Further, a light shielding film is formed on the charge transfer electrode to prevent light from entering during charge transfer. For example, the light shielding film is formed by depositing aluminum or the like by a sputtering method, and then forming an opening on the photodiode by a photolithography process and a dry etching process. At this time, if the level difference of the underlying polysilicon electrode is large, it is necessary to ensure a sufficient thickness of the light shielding film in order to improve the step coverage in sputtering of the light shielding film. In addition, if the level difference of the polysilicon electrode in the lower layer is large, the patterning accuracy of the light-shielding film is increased due to variations in the film thickness during resist application in the photolithography process for forming the opening of the photodiode. Variation occurs between the photodiodes, which causes a variation in photodiode sensitivity.

Therefore, as a method for stably forming a light shielding film, for example, in Patent Document 2 and Patent Document 3, a polysilicon electrode is polished by a chemical mechanical polishing (CMP) method. A method of flattening the overlapping portion has been proposed.
JP 2001-223352 A JP 11-26743 A JP 2003-158256 A

  As described above, in the conventional solid-state imaging device, if the width of the element isolation region is reduced in order not to sacrifice the sensitivity, there is a problem that the width of the charge transfer electrode made of polysilicon is reduced and the electric resistance is increased.

  Further, if the thickness of the charge transfer electrode made of polysilicon is increased in order to reduce the electric resistance of the charge transfer electrode, it becomes an obstacle to fine processing, and there is a limit to increasing the thickness. Further, there is a limit to a method for increasing the concentration of impurities contained in the charge transfer electrode made of polysilicon in order to reduce the electric resistance of the charge transfer electrode.

  Further, as disclosed in Patent Document 1, when a backing metal wiring is provided in a CCD type solid-state imaging device, a metal wiring extends in the vertical direction above the vertical charge transfer region, and is connected via a contact hole. The metal wiring and the polysilicon electrode of each layer are electrically connected. However, in this structure, the arrangement of the metal wiring and the arrangement of the contact hole that electrically connects the metal wiring and the polysilicon electrode are limited. Further, in the charge transfer electrode (three-layer polysilicon structure) made of three layers of polysilicon, since the three layers of electrodes are overlapped, it is difficult to sufficiently expose the charge transfer electrodes of each layer. It is difficult to provide a backing metal wiring for the polysilicon electrode.

  Further, as disclosed in Patent Documents 2 and 3, in the CCD solid-state imaging device, in the method of polishing the polysilicon electrode by the CMP method, the polysilicon layer of the wiring portion is also polished. Accordingly, it is difficult to apply the methods of Patent Documents 2 and 3 to the conventional charge transfer electrode having a three-layer polysilicon structure.

  The present invention solves the above-described conventional problems, and by reducing the resistance of the charge transfer electrode, the charge transfer speed is increased and the power consumption is reduced, and the step of the charge transfer electrode is reduced and provided in the upper layer. A solid-state imaging device capable of facilitating the processing of the light-shielding film, reducing sensitivity characteristic variation and smear of the photoelectric conversion device, and corresponding to an increase in the number of pixels of the solid-state imaging device and a high speed of charge transfer, and a manufacturing method thereof, An object of the present invention is to provide an electronic information device that uses this solid-state imaging device for an imaging unit.

The solid-state imaging device of the present invention has a plurality of photoelectric conversion elements provided on the surface of the semiconductor substrate, and is provided on the surface of the semiconductor substrate adjacent to the photoelectric conversion elements, and transfers charges read from the photoelectric conversion elements. A charge transfer region that can be enabled, a plurality of charge transfer electrodes provided on the charge transfer region via a gate insulating film, and a light-shielding film that covers the charge transfer electrode and has an opening on the photoelectric conversion element A plurality of charge transfer electrodes sequentially adjacent in the charge transfer direction are provided with the same thickness without overlapping each other, and each charge transfer electrode adjacent in a predetermined direction intersecting the charge transfer direction is provided. No wiring portion is provided between them, and the space is electrically connected by a wiring layer provided above the charge transfer electrode, thereby achieving the above object.

  Preferably, the charge transfer electrode in the solid-state imaging device of the present invention is made of a polysilicon layer, and the wiring layer is made of a metal layer.

Further preferably, the plurality of charge transfer electrodes in the solid-state imaging device of the present invention include first and second charge transfer electrodes alternately arranged in the charge transfer direction, the first charge transfer electrode and the second charge transfer electrode. The charge transfer electrodes are provided with the same thickness without overlapping each other, and no wiring portion is provided between each of the first and second charge transfer electrodes adjacent to each other in a predetermined direction intersecting the charge transfer direction. The space is electrically connected by the wiring layer.

Further preferably, the plurality of charge transfer electrodes in the solid-state imaging device of the present invention have first to fourth charge transfer electrodes sequentially and repeatedly arranged in the charge transfer direction, and the first to fourth charge transfer electrodes. Are provided with the same thickness without sequentially overlapping, and no wiring portion is provided between each of the first to fourth charge transfer electrodes adjacent to each other in a predetermined direction intersecting with the charge transfer direction. They are electrically connected by the wiring layer.

  Further preferably, an interlayer insulating film having a planarized surface is provided so as to cover the light shielding film in the solid-state imaging device of the present invention, and the wiring layer is provided on the interlayer insulating film.

  Further preferably, a contact portion for electrically connecting the charge transfer electrode and the wiring layer in the solid-state imaging device of the present invention is provided in the interlayer insulating film interposed between the charge transfer electrode and the wiring layer. ing.

  Further preferably, the contact portion in the solid-state imaging device of the present invention has a buried contact structure through a contact hole provided between the wiring layer and the charge transfer electrode.

  Further preferably, the light shielding film in the solid-state imaging device of the present invention is provided with a contact hole which is larger than the contact hole diameter of the contact portion and can penetrate the contact hole.

  Further preferably, the width size of the wiring layer in the solid-state imaging device of the present invention is formed to be the same size as the width size of the light shielding film.

The solid-state imaging device manufacturing method of the present invention includes a plurality of photoelectric conversion elements provided on the surface of a semiconductor substrate, and provided on the surface of the semiconductor substrate adjacent to the photoelectric conversion elements, and read from the photoelectric conversion elements A charge transfer region capable of transferring charge; first and second charge transfer electrodes alternately arranged in the charge transfer direction on the charge transfer region via a gate insulating film; and covering the charge transfer electrode, In a method for manufacturing a solid-state imaging device comprising a light-shielding film having an opening on a photoelectric conversion element, a step of forming a gate insulating film on a surface of a semiconductor substrate provided with the photoelectric conversion element and a charge transfer region, and the gate Forming a layer serving as a first charge transfer electrode on the insulating film; forming a second charge transfer electrode film; and subjecting the second charge to the layer serving as the first charge transfer electrode by a chemical mechanical polishing method. Transfer electrode film overlap Forming the same thickness so that the first charge transfer electrode and the second charge transfer electrode do not overlap with each other, and forming a light-shielding film so as to cover the first and second charge transfer electrodes The light-shielding film forming step and the first and second charge-transfer electrodes adjacent to each other in a predetermined direction intersecting the charge-transfer direction are provided in a layer above the charge-transfer electrode and shielded from light without providing a wiring portion. above the film, and forming a wiring layer for electrically connecting the above-described object can be achieved.

The solid-state imaging device manufacturing method of the present invention includes a plurality of photoelectric conversion elements provided on the surface of a semiconductor substrate, and provided on the surface of the semiconductor substrate adjacent to the photoelectric conversion elements, and read from the photoelectric conversion elements A charge transfer region capable of transferring charge, first to fourth charge transfer electrodes sequentially and repeatedly arranged in the charge transfer direction via a gate insulating film on the charge transfer region, and covering the charge transfer electrode, In a method for manufacturing a solid-state imaging device comprising a light-shielding film having an opening on the photoelectric conversion element, a step of forming a gate insulating film on a semiconductor substrate surface provided with the photoelectric conversion element and a charge transfer region; and Forming a layer to be the first and third charge transfer electrodes on the gate insulating film; forming second and fourth charge transfer electrode films; and performing the first and third charges by chemical mechanical polishing. In the layer that becomes the transfer electrode Removing the planarized portion of the second and fourth charge transfer electrode films and flattening the first and fourth charge transfer electrodes so as not to overlap each other, and the first to fourth charge transfer The charge transfer electrode is formed without providing a wiring portion between the step of forming a light shielding film so as to cover the electrode and the first to fourth charge transfer electrodes adjacent to each other in a predetermined direction intersecting the charge transfer direction. above the upper a and the light shielding film than, and forming a wiring layer for electrically connecting the above-described object can be achieved.

  Preferably, after the light shielding film forming step in the method for manufacturing a solid-state imaging device of the present invention, an interlayer insulating film is formed so as to cover the light shielding film, and the surface of the interlayer insulating film is formed by a chemical mechanical polishing method. A step of forming an interlayer insulating film for flattening, and in the wiring layer forming step, the wiring layer is formed on the surface of the flattened interlayer insulating film.

  Further preferably, in the method for manufacturing a solid-state imaging device according to the present invention, a contact hole is formed in the interlayer insulating film interposed between the wiring layer and the charge transfer electrode, and the charge transfer electrode is formed through the contact hole. And a contact portion forming step of forming a contact portion for electrically connecting the wiring layer and the wiring layer.

  Further preferably, in the contact part forming step in the method of manufacturing a solid-state imaging device of the present invention, the contact conductive film is formed on the contact hole of the interlayer insulating film, and the contact conductive film material is formed in the contact hole. At the same time, the conductive film for contact formed on the interlayer insulating film is removed using a chemical mechanical polishing method.

  Further preferably, in the light shielding film forming step in the method of manufacturing a solid-state imaging device of the present invention, in the contact portion forming step, a contact hole that allows an outer peripheral portion of the contact hole to pass through is formed in the light shielding film.

  Furthermore, preferably, the method further includes a step of forming an insulating film for an etching stopper on the charge transfer electrode as a pre-process of the light shielding film forming step in the method for manufacturing a solid-state imaging device of the present invention, and the contact portion forming step The contact hole is formed in the interlayer insulating film and the insulating film.

  Further preferably, in the step of forming a wiring layer in the method for manufacturing a solid-state imaging device of the present invention, the width of the wiring layer is formed to be the same as the width of the light shielding film.

  An electronic information device according to the present invention uses the solid-state imaging device according to any one of claims 1 to 9 for an imaging unit, thereby achieving the above object.

  The operation of the present invention will be described below with the above configuration.

  In the present invention, in a solid-state image pickup device such as a two-layer polysilicon structure CCD solid-state image pickup device and a three-layer polysilicon structure CCD solid-state image pickup device, a charge transfer electrode adjacent in the charge transfer direction is subjected to a chemical mechanical polishing method ( Since it is formed so as not to sequentially overlap each other by CMP or the like, it is possible to reduce an increase in coupling capacitance. In addition, since the plurality of charge transfer electrodes are formed with the same thickness without sequentially overlapping each other, the step of the light shielding film formed thereon can be reduced to facilitate the formation of the light shielding film. As a result, variations in processing of the light shielding film can be reduced, variations in characteristics of photoelectric conversion elements such as photodiodes can be reduced, and smear can be reduced.

  In addition, since the charge transfer electrodes adjacent to the direction crossing the charge transfer direction (including the direction orthogonal to each other) are connected by a wiring layer provided above the charge transfer electrode, the wiring portion is covered with a light shielding film. There is no need to cover, and the area of the light-shielding portion can be reduced to widen the area of the opening on the photoelectric conversion element, thereby reducing the sensitivity reduction.

  In this case, although the metal wiring layer is also shielded from light, the metal wiring layer can be made lower in resistance than the wiring part made of the polysilicon layer, so that the width can be further reduced, and moreover than the light shielding film covering the wiring part. Since only the metal wiring layer is narrower, the area of the opening can be increased.

  Furthermore, by using a wiring layer as a metal layer, for example, a single layer film such as Al, Al-Si, Al-Cu, Cu or W, or a multilayer film of these with TiN, Ti, TiW or W, etc. Charge transfer efficiency can be improved by lowering the resistance of the transfer electrode.

  This wiring layer can be provided on an interlayer insulating film flattened by a CMP method or the like used in a semiconductor manufacturing process, and the contact portion between this wiring layer and the charge transfer electrode has a buried contact structure. Thus, the flattened and thinned charge transfer electrode can be prevented from being scraped by a dry etching process or the like when forming the contact portion.

  In addition, since the contact diameter can be reduced to, for example, about 0.2 μm by using the fine contact formation technique, the wiring layer and the charge transfer electrode (polysilicon electrode) can be provided anywhere on the charge transfer electrode. The contact portion can be formed. For example, it can be installed on an element isolation region covered with a charge transfer electrode.

  Further, when a contact hole is provided in the light shielding film and a contact conductive material for connecting the charge transfer electrode made of polysilicon and the wiring layer made of metal is filled in the contact hole, the wiring layer is made It is possible to prevent light from entering from the contact hole of the light shielding film by forming the same size as the size in the direction intersecting with the charge transfer direction.

  As described above, according to the present invention, an increase in coupling capacitance due to overlapping of charge transfer electrodes is suppressed, the resistance of the charge transfer electrodes is reduced by using metal wiring, the area of the light shielding portion is reduced, and the light shielding film is processed. By reducing the variation, it is possible to reduce variations in the characteristics of the photoelectric conversion element and smear, and to suppress a decrease in sensitivity. Thereby, it is possible to cope with future increase in the number of pixels of the solid-state imaging device, increase in the charge transfer rate, and reduction in power consumption.

  Embodiments of a solid-state imaging device and a method for manufacturing the same according to the present invention will be described below with reference to the drawings.

  FIG. 1 is a main part plan view showing a structural example of an embodiment of a solid-state imaging device of the present invention, and FIG. 2 is a cross-sectional view taken along line CC ′ of FIG. The CC ′ line direction is a direction (horizontal direction in FIG. 1) that intersects (or is orthogonal to) the charge transfer direction.

  As shown in FIGS. 1 and 2, the solid-state imaging device 30 has a two-layer polysilicon structure, and is read from a photodiode 31 as a photoelectric conversion element and an adjacent photodiode 31 on the surface of a semiconductor substrate (not shown). A charge transfer region 32 for transferring charges, and a first charge transfer electrode 34 and a second charge transfer electrode 35 made of a polysilicon layer provided on the charge transfer region 32 via a gate insulating film 33 are provided. A light shielding film 36 having an opening is provided on the photodiode 31 so as to cover the first charge transfer electrode 34 and the second charge transfer electrode 35. Everything on the photodiode 31 is an opening.

  As in the case of the conventional solid-state imaging device 10 shown in FIGS. 6 to 8, the photodiode 31 includes a P-type low concentration impurity region (P-Well) provided on the surface of the semiconductor substrate and an N provided thereon. And a P-type high-concentration impurity layer has a buried structure.

  An element isolation region 41 is provided on a P-type low-concentration impurity region (P-Well) at the boundary portion of the photodiode 10 adjacent in the charge transfer direction (vertical direction in FIG. 1).

  The first charge transfer electrode 34 and the second charge transfer electrode 35 are alternately arranged in the charge transfer direction, and have the same thickness so that the first charge transfer electrode 34 and the second charge transfer electrode 35 do not sequentially overlap each other. Is provided.

  Further, between the first charge transfer electrodes 34 and the second charge transfer electrodes 35 adjacent to each other in the direction intersecting (or perpendicular to) the charge transfer direction (lateral direction in FIG. 1) is more than the charge transfer electrodes 34 and 35. They are electrically connected by a wiring layer 37 provided in the upper layer.

  The light shielding film 36 is provided on the first charge transfer electrode 34 and the second charge transfer electrode 35 via an insulating film 38. Since the first charge transfer electrode 34 and the second charge transfer electrode 35 do not overlap each other and have no stepped portion, the light shielding film 36 can be thinned without causing a stepped portion.

  An interlayer insulating film 39 having a planarized surface is provided on the light shielding film 36, and a wiring layer 37 made of a metal layer is provided on the interlayer insulating film 39. In the insulating film 38 and the interlayer insulating film 39, contact holes are provided on the first charge transfer electrode 34 and the second charge transfer electrode 35, respectively. A film material is provided to form a contact portion 40 having a buried contact structure that electrically connects the first charge transfer electrode 34 or the second charge transfer electrode 35 and the wiring layer 37.

  A contact hole 36 a through which the contact conductive film passes is formed in the light shielding film 36. The diameter of the contact hole 36 a is larger than the contact hole diameter of the contact portion 40. Since each wiring layer 37 that electrically connects each of the first charge transfer electrode 34 and the second charge transfer electrode 35 is higher than the light shielding film 36, the light shielding film 36 is between the adjacent photodiodes 31. It is not provided on the element isolation region 41.

  A method for manufacturing the solid-state imaging device 30 of the present embodiment configured as described above will be described below with reference to FIGS.

  FIG. 3 is a cross-sectional view taken along the line DD ′ for explaining a process for forming a layer serving as a charge transfer electrode of the solid-state image sensor of FIG. 1, and FIG. 4 is a light-shielding film forming process in the method for manufacturing the solid-state image sensor of this embodiment. FIG. 5 is a cross-sectional view taken along the line DD ′ for explaining the charge transfer electrode portion polishing step of the solid-state imaging device in FIG. 1. The DD ′ line direction is the charge transfer direction (vertical direction in FIG. 1).

  First, a mask is formed on a semiconductor substrate made of Si or the like by a photolithography method, and an impurity is added into the semiconductor substrate by using the mask by an ion implantation method. As shown in FIGS. A low-concentration impurity region 42, a charge transfer region 32, a photoelectric conversion element (photodiode) 31, and an element isolation region 41 for pixel isolation are formed.

  Next, a gate insulating film 33 is formed on the surface of the semiconductor substrate on which the photoelectric conversion element 31 and the charge transfer region 32 are provided. That is, the gate insulating film 33 having a thickness of 50 n to 100 nm is formed by thermally oxidizing the surface of the substrate or forming an oxide film, a nitride film, or a laminated layer thereof by a CVD method.

  Further, the first charge transfer electrode 34 is formed on the gate insulating film 33. That is, after forming a polysilicon layer to be the first charge transfer electrode 34 to a thickness of 50 nm to 1000 nm, for example, 300 nm by the CVD method, the resist mask is formed by patterning the pattern of the first charge transfer electrode 34 by the photolithography method. Then, for example, by selectively etching the polysilicon layer by a dry etching method, a layer 34a to be the first charge transfer electrode 34 is formed as shown in FIG. At this time, conventionally, a wiring portion that connects the first charge transfer electrodes 34 adjacent to each other in the direction crossing the charge transfer direction (lateral direction in FIG. 1) is also formed. A wiring portion for connecting the charge transfer electrodes 34 is not formed.

  Further, a layer 35a to be the second charge transfer electrode film 35 is formed, and an overlapping portion between the first charge transfer electrode 34a and the second charge transfer electrode film 35a is flattened by a chemical mechanical polishing method, and the first charge transfer electrode film 35 is flattened. The charge transfer electrode 34 and the second charge transfer electrode 35 are formed with the same thickness so as not to overlap each other. That is, an insulating film is formed to make up for the gate insulating film 33 lost by over-etching during the etching of the first charge transfer electrode portion 34a, and the polysilicon serving as the second charge transfer electrode 35 is formed as shown in FIG. The layer 35 a is formed in the same manner as the polysilicon layer 34 a that becomes the first charge transfer electrode 34. Thereafter, the polysilicon layer 35a to be the second charge transfer electrode 35 and the polysilicon layer 34a to be the first charge transfer electrode portion 34 are sequentially polished by CMP to polish to an arbitrary charge transfer electrode film thickness, for example, 100 nm. .

  Thereafter, the pattern of the second charge transfer electrode 35 is patterned by a photolithography method to form a resist mask, and the polysilicon layer is selectively etched by, for example, a dry etching method to obtain a second mask as shown in FIG. A charge transfer electrode 35 is formed. At this time, conventionally, a wiring portion that connects between the second charge transfer electrodes 35 adjacent to each other in the direction intersecting the charge transfer direction (lateral direction in FIG. 1) is also formed. A wiring portion for connecting the charge transfer electrodes 35 is not formed.

  As a result, as shown in FIGS. 4 and 5, the first charge transfer electrodes 34 and the second charge transfer electrodes 35 are alternately arranged in the charge transfer direction (vertical direction in FIGS. 1 and 4) so as not to overlap. Between the first charge transfer electrodes 34 and the second charge transfer electrodes 35 that are provided with the same thickness and are adjacent to each other in the direction crossing the charge transfer direction (lateral direction in FIGS. 1 and 4) as in the conventional case. A first charge transfer electrode 34 and a second charge transfer electrode 35 that are not provided with a wiring portion are formed. Note that the etching step for forming the second charge transfer electrode 35 may be performed before polishing by the CMP method.

  Further, the first charge transfer electrode 34 and the second charge transfer electrode 35 serve as a stopper for preventing overetching during etching for forming a contact hole for connecting the charge transfer electrodes 34 and 35 and the metal wiring layer 37. A nitride film is formed by a CVD method, and an oxide film by a CVD method is laminated as necessary to form an insulating film 38 of 50 nm to 100 nm as shown in FIG.

  Thereafter, a light shielding film 36 is formed so as to cover the first charge transfer electrode 34 and the second charge transfer electrode 35. That is, the light shielding film 36 is formed on the insulating film 38 by using a single layer film such as Al, Al-Si, Al-Cu, Cu or W, or a multilayer film of these with TiN, Ti, TiW or W. Deposit layers. The layer that becomes the light shielding film 36 covers the flat charge transfer electrodes 34 and 35, so that it is thinner than the charge transfer electrodes having stepped portions and the light shielding films that cover the wiring portions as in the conventional case. Is possible. Thereafter, a resist mask is formed by patterning the pattern of the light-shielding film 36 by photolithography, and the layer that becomes the light-shielding film 36 is selectively etched using, for example, a dry etching method. As shown, a light shielding film 36 is formed.

  At this time, unlike the conventional pattern, the wiring portion made of the polysilicon layer is not provided in the present embodiment, so that the light shielding film 36 is formed only on the charge transfer electrodes 34 and 35 as shown in FIG. . At this time, a contact hole 36 a having a sufficient margin is formed in the light shielding film 36 so that the light shielding film 36 does not contact the contact conductive film when the contact portion connecting the charge transfer electrodes 34 and 35 and the metal wiring layer 37 is formed. It is formed.

  Next, an oxide film, a BPSG film, or the like, which is a layer that becomes the interlayer insulating film 39, is formed by the CVD method, and is uniformly polished from the surface (the highest position) to a height of about 200 nm to 500 nm using the CMP method. As a result, as shown in FIG. 2, an interlayer insulating film 39 having a planarized surface is formed.

  Thereafter, a resist mask is formed on the charge transfer electrodes 34 and 35 by photolithography to pattern a contact hole pattern connecting the charge transfer electrodes 34 and 35 and the metal wiring layer 37, for example, by dry etching. A contact hole is formed in the interlayer insulating film 39 by selective etching using the interlayer insulating film 39.

  At this time, the etching is selectively stopped by the nitride film (insulating film 38) laminated on the charge transfer electrodes 34 and 35, and then the charge transfer is performed by etching only the nitride film (insulating film 38). To prevent over-etching of the electrode film as much as possible. As described above, the flattened and thinned charge transfer electrodes 34 and 35 can be prevented from being cut by a dry etching process or the like when forming the contact portion.

  After that, a single layer film such as Cu, W or TiW or a multilayer film of these with Ti or TiN is formed as the contact portion conductive film, and the contact hole is filled with a conductive material, and then the CMP method is performed. The contact portion conductive film on the interlayer insulating film 39 is removed to form a contact portion 40 having a buried contact structure in the contact hole as shown in FIG.

  Further, a wiring layer 37 that electrically connects each of the first charge transfer electrode 34 and the second charge transfer electrode 35 (between the first charge transfer electrodes 34 or between the second charge transfer electrodes 35) is formed. That is, a metal wiring layer is formed by using a single layer film such as Al, Al-Si, Al-Cu, Cu or W or a multilayer film of these layers and TiN, Ti, TiW or W, etc. A pattern of the metal wiring layer 37 is patterned to form a resist mask, and the metal wiring layer 37 is selectively etched by using, for example, a dry etching method, as shown in FIG. Form.

  At this time, as shown in FIG. 2, the metal wiring layer 37 has a charge of the light shielding film 36 on the light shielding film 36 in order to prevent light from entering the charge transfer region 32 from the contact hole 36 a opened in the light shielding film 36. It is formed in a size equivalent to the size in the direction (horizontal direction in FIG. 4) that intersects (or is orthogonal to) the transfer direction (vertical direction in FIG. 4). A metal wiring layer 37 is formed above the contact hole 36 a, and the contact hole 36 a is shielded from light by the metal wiring layer 37.

  In the solid-state imaging device 30 of the present embodiment manufactured as described above, the first charge transfer electrode 34 and the second charge transfer electrode 35 adjacent in the charge transfer direction (vertical direction in FIG. 1) are polished by the CMP method. Therefore, the coupling capacitance can be prevented from increasing.

  In addition, since the first charge transfer electrode 34 and the second charge transfer electrode 35 are formed with the same thickness without sequentially overlapping each other, the step of the light shielding film 36 formed thereon is reduced to form the light shielding film 36. Can be facilitated. Thereby, the processing variation of the light shielding film 36 can be reduced, the characteristic variation of the photodiode 31 can be reduced, and the smear can be reduced.

  Further, between each of the first charge transfer electrode 34 and the second charge transfer electrode 35 adjacent to each other in the direction crossing (or orthogonal to) the charge transfer direction (vertical direction in FIG. 1) (lateral direction in FIG. 1) (first Between the charge transfer electrodes 34 and between the second charge transfer electrodes 35) are connected by a wiring layer 37 provided above the charge transfer electrodes 34, 35, so that the wiring part is covered with a light shielding film as in the prior art. There is no need, and the area of the light-shielding portion can be sufficiently reduced to widen the opening, thereby reducing sensitivity reduction.

  Furthermore, since the wiring layer 37 is made of a metal layer, it is possible to reduce the resistance of the charge transfer electrode and improve the charge transfer efficiency. The wiring layer 37 is provided on the interlayer insulating film 39 whose surface is flattened, and is electrically connected to the charge transfer electrodes 34 and 35 by the contact portion 40 having a buried contact structure.

  In addition, since the contact diameter can be reduced to, for example, about 0.2 μm by using the fine contact formation technique, the wiring layer 37 and the charge transfer electrode (polyester) can be placed anywhere on the charge transfer electrodes 34 and 35. Contact portions 40 with silicon electrodes 34 and 35 can be formed.

  Further, the wiring layer 37 is formed to have the same width size as the size (width size of the light shielding film 36) in the direction intersecting (or orthogonal to) the charge transfer direction of the light shielding film 36. Accordingly, it is possible to prevent the incident light from entering from the contact hole 36a of the light shielding film 36.

  In summary, according to the present embodiment, the polysilicon charge transfer electrodes 34 and 35 adjacent to each other in the charge transfer direction are polished by the CMP method so as to have substantially the same thickness and intersect with the charge transfer direction ( Alternatively, the charge transfer electrodes adjacent in the orthogonal direction are electrically connected by a metal wiring layer 37 provided in the upper layer. For this reason, since the metal wiring layer 37 is not covered with the light shielding film, the area of the opening 31 on the photodiode can be increased. In addition, the resistance of the charge transfer electrodes 34 and 35 is reduced, so that the charge transfer speed is increased and the power consumption is reduced, and the conventional light shielding film provided on the upper layer by reducing the level difference between the charge transfer electrodes 34 and 35. 36 can be facilitated, and variations in sensitivity characteristics and smear of the photoelectric conversion elements can be reduced.

  In the present embodiment, the CCD type solid-state imaging device 30 having a two-layer polysilicon structure has been described as an example. However, the present invention is not limited to this, and a three-layer polysilicon structure (per pixel in a four-phase drive system). It is also applicable to a multi-layer polysilicon structure having four transfer electrodes) or more. In the case of a three-layer polysilicon structure, a metal wiring layer 37 that connects each of the charge transfer electrodes 34 and 35 adjacent to each other in a direction crossing (or orthogonal to) the charge transfer direction has a two-layer structure, and the upper charge transfer electrode The upper wiring layer is preferably formed thin so as not to shield the opening of the photodiode. Further, when the wiring layer is composed of one layer, a structure in which four metal wiring layers are provided on the element isolation region 41 can be adopted. Here, in the case of the three-layer polysilicon structure, the four-phase driving method is adopted and four transfer electrodes are owned, and in the case of adopting the current CMP method, the processing method is the same as the two-layer polysilicon structure. The width of the electrode transfer method is reduced.

  Although not specifically described in the present embodiment, the solid-state imaging device 30 of the present embodiment is used in an imaging unit of various electronic information devices such as a digital still camera, a digital video camera, and a camera-equipped mobile phone. In addition, the present invention can suppress an increase in coupling capacitance due to overlapping of charge transfer electrodes as in the prior art, reduce the resistance of the charge transfer electrodes, reduce variations in photoelectric conversion element characteristics and smear, and suppress a decrease in sensitivity. As a result, the display quality of the image captured by the imaging unit of the electronic information device is good, and low power consumption can be achieved by high-speed processing.

  As mentioned above, although this invention has been illustrated using preferable embodiment of this invention, this invention should not be limited and limited to this embodiment. It is understood that the scope of the present invention should be construed only by the claims. It is understood that those skilled in the art can implement an equivalent range from the description of specific preferred embodiments of the present invention based on the description of the present invention and common general technical knowledge. Patents, patent applications, and documents cited herein should be incorporated by reference in their entirety, as if the contents themselves were specifically described herein. Understood.

  The present invention relates to a solid-state imaging device such as a CCD solid-state imaging device and a method for manufacturing the same, and a conventional method in the field of electronic information equipment using the imaging device such as a digital still camera, a digital video camera, and a mobile phone with a camera. In the future, the increase in the coupling capacitance due to the overlap of the charge transfer electrodes can be suppressed, the resistance of the charge transfer electrodes can be lowered, the variation in the characteristics of the photoelectric conversion elements and smear can be reduced, and the sensitivity can be reduced. It is possible to cope with an increase in the number of pixels of a solid-state imaging device, an increase in charge transfer speed, and a reduction in power consumption.

  The solid-state imaging device of the present invention can be widely used in an imaging unit of an electronic information device such as a digital still camera, a digital video camera, or a camera-equipped mobile phone, and a captured image with a good display quality can be obtained by high-speed processing. It can be obtained with low power consumption.

It is a principal part top view which shows the structural example of one Embodiment of the solid-state image sensor of this invention. It is CC 'sectional view taken on the line of FIG. FIG. 6 is a cross-sectional view taken along the line DD ′ for explaining a step of forming a layer that becomes a charge transfer electrode of the solid-state imaging device of FIG. 1. It is a principal part top view for demonstrating an example of the light shielding film formation process in the manufacturing method of the solid-state image sensor of this embodiment. FIG. 4 is a DD ′ line cross-sectional view for explaining a charge transfer electrode portion polishing step of the solid-state imaging device of FIG. 1. It is a principal part top view which shows the structural example of the conventional CCD type solid-state image sensor. FIG. 7 is a sectional view taken along line AA ′ of FIG. 6. FIG. 7 is a sectional view taken along line BB ′ in FIG. 6.

Explanation of symbols

DESCRIPTION OF SYMBOLS 30 Solid-state image sensor 31 Opening part of photoelectric conversion element (photodiode) 32 Charge transfer area 33 Gate insulating film 34,35 Charge transfer area 36 Light-shielding film 37 Metal wiring layer 38 Insulating film 39 Interlayer insulating film 40 Contact part 41 Element isolation area 42 P-type low concentration impurity region (P-Well)

Claims (18)

A plurality of photoelectric conversion elements provided on the surface of the semiconductor substrate, a charge transfer region provided on the surface of the semiconductor substrate adjacent to the photoelectric conversion elements and capable of transferring charges read from the photoelectric conversion elements; A solid-state imaging device comprising: a plurality of charge transfer electrodes provided on the charge transfer region via a gate insulating film; and a light shielding film that covers the charge transfer electrode and has an opening on the photoelectric conversion element. ,
A plurality of charge transfer electrodes sequentially adjacent in the charge transfer direction are provided with the same thickness without overlapping each other, and a wiring portion is not provided between each charge transfer electrode adjacent in a predetermined direction intersecting the charge transfer direction. First, a solid-state imaging device in which the space is electrically connected by a wiring layer provided above the charge transfer electrode.    The solid-state imaging device according to claim 1, wherein the charge transfer electrode is made of a polysilicon layer, and the wiring layer is made of a metal layer. The plurality of charge transfer electrodes include first and second charge transfer electrodes alternately arranged in the charge transfer direction, and the first charge transfer electrode and the second charge transfer electrode are the same without overlapping each other. There is no wiring portion between each of the first and second charge transfer electrodes provided in a thickness and adjacent in a predetermined direction intersecting the charge transfer direction, and the space between the first and second charge transfer electrodes is electrically connected by the wiring layer. The solid-state image sensor of Claim 1 or 2 connected. The plurality of charge transfer electrodes include first to fourth charge transfer electrodes sequentially and repeatedly arranged in the charge transfer direction, and the first to fourth charge transfer electrodes are provided with the same thickness without sequentially overlapping. A wiring portion is not provided between each of the first to fourth charge transfer electrodes adjacent to each other in a predetermined direction crossing the charge transfer direction, and the portion is electrically connected by the wiring layer. The solid-state imaging device according to claim 1 or 2.    2. The solid-state imaging device according to claim 1, wherein an interlayer insulating film having a planarized surface is provided so as to cover the light shielding film, and the wiring layer is provided on the interlayer insulating film.   The solid-state imaging device according to claim 5, wherein a contact portion for electrically connecting the charge transfer electrode and the wiring layer is provided in the interlayer insulating film interposed between the charge transfer electrode and the wiring layer. .    The solid-state imaging device according to claim 6, wherein the contact portion has a buried contact structure through a contact hole provided between the wiring layer and the charge transfer electrode.    The solid-state imaging device according to claim 7, wherein the light shielding film is provided with a contact hole that is larger than a contact hole diameter of the contact portion and can penetrate the contact hole.    The solid-state imaging device according to claim 8, wherein a width size of the wiring layer is formed to be the same size as a width size of the light shielding film. A plurality of photoelectric conversion elements provided on the surface of the semiconductor substrate, a charge transfer region provided on the surface of the semiconductor substrate adjacent to the photoelectric conversion elements and capable of transferring charges read from the photoelectric conversion elements; First and second charge transfer electrodes alternately arranged in the charge transfer direction via a gate insulating film on the charge transfer region, and a light-shielding film that covers the charge transfer electrode and has an opening on the photoelectric conversion element In a method for manufacturing a solid-state imaging device comprising:
Forming a gate insulating film on the surface of the semiconductor substrate provided with the photoelectric conversion element and the charge transfer region;
Forming a layer to be a first charge transfer electrode on the gate insulating film;
Forming a second charge transfer electrode film, and removing and planarizing the overlapping portion of the second charge transfer electrode film with respect to a layer to be the first charge transfer electrode by a chemical mechanical polishing method; And forming the same thickness so that the second charge transfer electrodes do not overlap each other;
A light shielding film forming step of forming a light shielding film so as to cover the first and second charge transfer electrodes;
Without providing a wiring portion between each of the first and second charge transfer electrodes adjacent in a predetermined direction intersecting the charge transfer direction, above the upper a and the light-shielding film than the charge transfer electrodes, between said Forming a wiring layer that electrically connects the solid-state imaging device. A plurality of photoelectric conversion elements provided on the surface of the semiconductor substrate, a charge transfer region provided on the surface of the semiconductor substrate adjacent to the photoelectric conversion elements and capable of transferring charges read from the photoelectric conversion elements; The first to fourth charge transfer electrodes sequentially and repeatedly arranged in the charge transfer direction via the gate insulating film on the charge transfer region, and the light shielding covering the charge transfer electrode and having an opening on the photoelectric conversion element In a method for manufacturing a solid-state imaging device comprising a film,
Forming a gate insulating film on the surface of the semiconductor substrate provided with the photoelectric conversion element and the charge transfer region;
Forming a layer to be first and third charge transfer electrodes on the gate insulating film;
The second and fourth charge transfer electrode films are formed, and the overlapping portions of the second and fourth charge transfer electrode films with respect to the layers to be the first and third charge transfer electrodes are removed by chemical mechanical polishing to be flat. Forming the same thickness so that the first to fourth charge transfer electrodes do not overlap each other;
Forming a light shielding film so as to cover the first to fourth charge transfer electrodes;
Without providing a wiring portion between each of said fourth charge transfer electrode adjacent to the predetermined direction crossing the charge transfer direction, above the upper a and the light shielding film than the charge transfer electrodes, said And a step of forming a wiring layer that electrically connects them.    After the light shielding film forming step, further comprising an interlayer insulating film forming step of forming an interlayer insulating film so as to cover the light shielding film, and planarizing the surface of the interlayer insulating film by a chemical mechanical polishing method, 12. The method for manufacturing a solid-state imaging element according to claim 10, wherein in the wiring layer forming step, the wiring layer is formed on the planarized surface of the interlayer insulating film.   A contact hole is formed in the interlayer insulating film interposed between the wiring layer and the charge transfer electrode, and a contact is formed to electrically connect the charge transfer electrode and the wiring layer through the contact hole. The manufacturing method of the solid-state image sensor of Claim 12 which further has a part formation process.    In the contact portion forming step, a contact conductive film is formed on the contact hole of the interlayer insulating film, the contact conductive film material is embedded in the contact hole, and the contact conductive film is formed on the interlayer insulating film. The method for manufacturing a solid-state imaging device according to claim 13, wherein the conductive film is removed using a chemical mechanical polishing method.    15. The method of manufacturing a solid-state imaging device according to claim 13, wherein the light shielding film forming step forms a contact hole in the light shielding film that allows an outer peripheral portion of the contact hole to penetrate in the contact portion forming step.    As a pre-process of the light shielding film forming step, the method further includes a step of forming an insulating film for an etching stopper on the charge transfer electrode. In the contact portion forming step, the contact hole is formed in the interlayer insulating film and the insulating film. The manufacturing method of the solid-state image sensor in any one of Claims 13-15 which forms.    The solid-state imaging device manufacturing method according to claim 15, wherein the wiring layer forming step forms a width size of the wiring layer equal to a width size of the light shielding film. An electronic information device using the solid-state imaging device according to claim 1 for an imaging unit.

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