JP4299643B2 - Solid-state imaging device and manufacturing method thereof - Google Patents

Description

  The present invention relates to a solid-state imaging device and a manufacturing method thereof, and more particularly to a solid-state imaging device in which a color filter is formed on a photoelectric conversion unit (light receiving unit) and a manufacturing method thereof.

2. Description of the Related Art Conventionally, there is a CCD solid-state imaging device as shown in FIG. The base device in this CCD solid-state imaging device has a periodic step of several μm because the electrode 3 and the light shielding film 5 are formed. Further, the outermost surface of the base device is covered with a protective film 6 such as Si ₃ N ₄ . Therefore, in a so-called on-chip process performed after the formation of the base device, the flattening layer 7 is formed by spin-coating a transparent flattening material prior to the formation of the color filters 8, 9, 10. It is necessary to form the color filters 8, 9, and 10 after reducing the level difference of the base device.

  However, as the integration of pixels increases, reduction in the Z direction as well as reduction in the X and Y directions has become important and necessary. In FIG. 2, 1 is a substrate, 2 is a light receiving portion (photoelectric conversion portion), 4 is an interlayer insulating film, 11 is a protective layer, and 12 is a microlens.

  FIG. 3 shows a conceptual diagram of an optical system in the unit cell shown in FIG. In FIG. 3, when the distance L in the Z direction from the light receiving portion 2 to the microlens 12 is long, the oblique incident light 15 is shielded by the convex portion 13 made of the electrode 3 or the like, and the incident light is effectively used. become unable. Reference numeral 14 denotes vertically incident light.

  By the way, imaging devices (cameras, etc.) using a solid-state imaging element have become compact in optical system with the progress of high integration, and accordingly, the adoption of lenses with extremely short exit pupil positions has become active. . As shown in FIG. 4, the feature of the lens having an extremely short exit pupil position is that the incident angle of light on the surface of the solid-state imaging device 16 is larger in the case of the short pupil position lens 18 than in the normal lens. In other words, the ratio of the oblique incident light 20 to the total luminous flux incident on the imaging region 17 of the solid-state imaging device 16 is increased. As a result, the amount of incident light is non-uniform between the central portion and the peripheral portion of the imaging region 17 and a shading phenomenon occurs. The main cause of the occurrence of this shading phenomenon is that the incident angle of the oblique incident light 20 is larger in the peripheral portion than in the central portion of the imaging region 17, so that a convex portion (light-shielding film) formed in the transfer region of the solid-state imaging device 16 Etc.), the luminous flux is likely to be kicked. This shading phenomenon becomes more prominent as the distance in the Z direction from the light receiving portion of the solid-state imaging device 16 to the microlens increases as described above. Reference numeral 19 denotes normal incident light.

  On the other hand, there is a demand for higher image quality in the color tone of the screen, and accordingly, it is necessary to further improve the quality of the transmitted color spectral characteristics of the color filter. For that purpose, it is necessary to improve the quality of the hue, and this can be dealt with by increasing the thickness of the color filter. However, increasing the thickness of the color filter is contrary to the Z-direction reduction requirement described above.

  In addition, when forming a solid-state imaging device by high integration as described above, in FIG. 2, the registration (alignment accuracy) to the base device in the process of forming the color filters 8, 9, 10 and the microlens 12 is as follows. There is a strong demand compared to the prior art. Here, in the wafer alignment, the alignment between the base device and the upper layer is performed by detecting the reflected / diffracted light of the laser beam from the alignment mark formed on the base device through the flattening layer 7. ing. However, a large optical deviation is likely to occur in detecting the imaging position of the alignment mark through the planarizing layer 7 having a thickness of several μm.

  When such a shift is applied when the color filters 8, 9, and 10 are formed on the flattening layer 7, the image quality is sensitively affected as follows. That is, as shown in FIG. 5, even if the deviation amount D between the pixel 21 and the color filters 8, 9, 10 is the same, the greater the thickness H of the planarization layer 7, the more the crosstalk light to the adjacent pixel 21 '. The ratio of (mixed color light) 22 to normal light 23 increases.

  Although some problems have been described above, these problems have emerged as problems with the progress of higher integration of solid-state imaging devices. These problems are caused by forming the color filters 8, 9, and 10 after forming the thick planarization layer 7 on the underlying device (that is, increasing the interval in the Z direction).

  As a method for solving the above-described problems, for example, a method for manufacturing an optical color filter for a solid-state imaging device disclosed in Patent Document 1 is known. Hereinafter, the manufacturing method of this optical color filter for solid-state image sensors will be described with reference to FIG.

  First, as shown in FIG. 6A, a stepped portion 27 made of an electrode, a light shielding film, or the like is formed between the light receiving portions (photoelectric conversion portions) 26 on the substrate 25 to obtain a solid-state imaging device. Then, a resist layer 28 is applied to the solid-state imaging device, and the step portions between the step portions 27 are embedded. Next, as shown in FIG. 6 (b), a plurality of predetermined regions in the resist layer 28 centering on the light receiving portions 26 for the same color are opened, and the same color is formed on the entire surface including the opening. A layer of a polymer resin containing a dye (hereinafter referred to as a dyed layer) 29 is formed, and the dyed layer 29 is embedded in the predetermined region. Next, as shown in FIG. 6C, the dyed layer 29 is etched back, leaving the dyed layer 29 only in the openings. Thereafter, as shown in FIG. 6D, the resist layer 28 is removed with a stripping solution.

  Hereinafter, a series of steps shown in FIGS. 6A to 6D are repeatedly performed for the light receiving portions 26 of all colors, and a plurality of dyed layers 29a to 29d are embedded on all the light receiving portions 26, and each dyed layer 29a is embedded. ˜29d are color filters. Thereafter, a planarization layer 30 is formed.

  However, the method for manufacturing an optical color filter for a solid-state imaging device disclosed in Patent Document 1 has the following problems. That is, in the step shown in FIG. 6B, the dye layer (polymer resin layer) 29 is embedded after the resist layer 28 is patterned. Therefore, a resist step 31 generated when the resist layer 28 is patterned is added to the original step portion 32, and the dyed layer 29 is embedded in a larger step. Therefore, the coating film thickness of the dyed layer 29 becomes non-uniform (striation), and in an extreme case, the step composed of “resist step 31 + step 32” may not be completely embedded.

  The patterning of the resist layer 28 is performed on a light shielding film (not shown) above the stepped portion 27. However, in that case, the edge shape of the resist layer 28 is forward-tapered because it is easily subjected to halation from the light shielding film. Therefore, when the polymer resin that becomes the dyeing layer 29 is embedded, the embedded dyeing layer 29 is reversely tapered to reflect the base pattern (the edge pattern of the resist layer 28). As a result, a void is generated at the edge portion of the adjacent color filter. That is, the adjacent color filters 29 such as the color filters 8, 9, and 10 shown in FIG. Therefore, there is a problem that the image quality is deteriorated.

  Further, since unnecessary portions of the polymer resin, which is the dye layer 29 for each color, are removed by etch back (generally easy to vary), there is also a problem that the surface of each dye layer (filter) 29 does not become flat.

As described above, in the method for manufacturing an optical color filter for a solid-state imaging device disclosed in Patent Document 1, adjacent color filters 29 cannot be continuously formed in contact with each other. Therefore, the planarization layer 30 needs to be formed. As a result, although the color filters 29a to 29d are directly embedded in the step portions between the step portions 27, the vertical distance from the light receiving portion 26 to the microlens (not shown) is reduced. Therefore, improvement of the above-mentioned shading phenomenon and detection error of the base alignment mark cannot be expected so much.
Japanese Patent Laid-Open No. 3-98002

  SUMMARY OF THE INVENTION An object of the present invention is to provide a high-accuracy and high-quality solid-state imaging device that is drastically reduced in the vertical direction, and a method for manufacturing the same.

In order to solve the above-described problems, a solid-state imaging device of the present invention
A unit cell composed of a convex region composed of a transfer region formed on a substrate, a concave region composed of a light receiving region adjacent to the convex region on the substrate, and a color filter formed on the unit cell And a solid-state imaging device having a microlens,
The convex region and the concave region have a protective film on their surfaces,
The color filter is directly embedded in the recessed area Rutotomoni extends to the center portion of the projecting portion positioned on opposite sides of the recess area,
Adjacent the color filter is to ensure continuity edge portion overlap one another,
The surfaces of the plurality of color filters having overlapping continuity are substantially flat,
One edge portion of the overlapping edge portions has a forward tapered shape, while the other edge portion rides on the one edge portion,
The convex regions sequentially stacked layers insulating film is configured to cover the electrode with the light shielding film and the protective film,
In the convex region, the protective film is in contact with the upper surface of the light shielding film and in contact with the lower surface of the color filter.

According to the above configuration, the color filter is formed by being directly embedded in the recessed area between the protruding areas formed by the transfer area formed on the substrate, and the edge portions of the adjacent color filters are mutually connected. Overlapping to ensure continuity . Therefore, shielding of oblique incident light is reduced, the above-mentioned shading phenomenon is improved, and image quality deterioration is prevented.

Furthermore, the convex region is an electrode are sequentially laminated layers insulating film is configured to cover a light-shielding film and the protective film, the protective film in the convex regions is and contact with the upper surface of the light shielding film above It is in contact with the lower surface of the color filter. Therefore, there is nothing between the color filter and the protective film and between the protective film and the light-shielding film, and the color filter is formed at a position closer to the substrate without using a planarizing layer or the like. Therefore, the detection error of the base alignment mark when forming the color filter is small, and the amount of deviation of the color filter is small. Furthermore, inevitably, the microlens is also formed at a position close to the substrate. Therefore, the base alignment mark detection error when forming the microlens is small, and the amount of misalignment of the microlens is small. As a result, a higher quality image can be obtained.

  In the solid-state imaging device of one embodiment, a surfactant is added to the color filter.

  According to this embodiment, a surfactant is added to the color filter. Therefore, the applicability of the color filter can be improved, and the color filter can be uniformly applied to the recessed area.

In addition, the manufacturing method of the solid-state imaging device of the present invention includes
A method for manufacturing a solid-state imaging device according to the present invention, comprising:
The above color filter
Extends to the central portion of the convex portion located on both sides of the unrealized the recessed area a predetermined recessed area after applying a color filter material having a viscosity of less than 10CP on columns of the unit cells at 2000rpm following rotational speed The step of forming a pattern and directly embedding the color filter material in the concave region is repeated for the number of colors of the color filter, and adjacent color filters are formed so as to contact each other. .

  According to the above configuration, the color filter is formed by directly embedding the color filter material in the recessed regions existing between the projecting region formed by the transfer region formed on the substrate. Therefore, the color filter is formed with respect to a lower step, and the thickness of the color filter is prevented from being striae and the surface is formed to be substantially flat. Therefore, it is not necessary to form a planarizing layer, and the vertical dimension is reduced. Furthermore, since the edge shape of the color filter is a forward taper, no void is generated at the edge portion of the adjacent color filter. Therefore, adjacent color filters are in contact with each other and are formed continuously. As a result, deterioration of image quality is prevented.

  At that time, the viscosity of the color filter material is adjusted to a low viscosity of 10 CP or less and applied at a low rotation speed of 2000 rpm or less. Therefore, the color filter material is uniformly embedded in the recessed area, and the color filter thickness is prevented from being striae and the surface is formed to be substantially flat.

  Further, in the convex region, the protective film is formed so as to be in contact with the upper surface of the light-shielding film and in contact with the lower surface of the color filter. A filter is formed. Therefore, the detection error of the base alignment mark when forming the color filter is small, and the displacement of the color filter is reduced. Furthermore, inevitably, the microlens is also formed at a position close to the substrate. Therefore, the ground alignment mark detection error in forming the microlens is reduced, and the displacement of the microlens is reduced. In this way, a higher quality image can be obtained.

  In the manufacturing method of the solid-state imaging device of one embodiment, a dyeable polymer material made of a photosensitive resin is used as the color filter material.

  According to this embodiment, a color filter using a dyeable polymer material made of a photosensitive resin is formed in contact with an adjacent color filter in the recessed area without a planarizing layer. In this way, deterioration of image quality is prevented.

  In the manufacturing method of the solid-state imaging device of one embodiment, a color resist is used as the color filter material.

  According to this embodiment, a color filter using a color resist is formed in contact with an adjacent color filter without a planarizing layer in the concave region. In this way, deterioration of image quality is prevented.

As is clear from the above, the solid-state imaging device according to the present invention directly embeds the color filter in the recessed area and forms adjacent color filters so that the edge portions overlap each other to ensure continuity. Thus, the shading phenomenon can be improved and the deterioration of the image quality can be prevented. Furthermore, convex regions sequentially laminated layers insulating film, covering the electrode serves as a light-shielding film and the protective film, the protective film in the convex regions on the bottom surface of and the color filter in contact with the upper surface of the light shielding film Since they are formed in contact with each other, there is nothing between the color filter and the protective film and between the protective film and the light shielding film, and the color filter is formed at a position closer to the substrate without using a planarizing layer or the like. Has been. Therefore, the detection error of the base alignment mark when forming the color filter is small, and the amount of deviation of the color filter is small. Furthermore, inevitably, the microlens is also formed at a position close to the substrate. Therefore, the base alignment mark detection error when forming the microlens is small, and the amount of misalignment of the microlens is small. Therefore, higher quality image quality can be obtained.

  That is, according to the present invention, the vertical dimension can be reduced without degrading the performance of the device. As a result, it is possible to improve the shading failure, improve the alignment accuracy of color filters and microlenses, and suppress deterioration in image quality due to crosstalk, so that a high-precision and high-definition solid-state imaging device can be obtained. .

  Further, in the method for manufacturing a solid-state imaging device according to the present invention, the color filter is formed by directly embedding the color filter material in the recessed region, so that the color filter can be formed for a lower step. Therefore, striation of the thickness of the color filter can be prevented to form the surface substantially flat, and the vertical dimension can be reduced by omitting the formation of the flattening layer. As a result, the shading phenomenon can be improved by reducing the shielding of oblique incident light. Furthermore, since the edge shape of the color filter can be a forward taper, adjacent color filters can be continuously formed by contacting each other. Therefore, deterioration of image quality can be prevented.

  At that time, the viscosity of the color filter material is adjusted to a low viscosity of 10 CP or less and applied at a low rotation speed of 2000 rpm or less. Therefore, the color filter material can be uniformly embedded in the recessed area, and the surface of the color filter can be formed substantially flat by preventing the thickness of the color filter from striation.

  Further, in the convex region, the protective film is formed so as to be in contact with the upper surface of the light-shielding film and in contact with the lower surface of the color filter, so that the color filter is disposed at a position close to the substrate without using a planarizing layer or the like. Can be formed. Accordingly, it is possible to reduce the detection error of the base alignment mark when forming the color filter, and to reduce the deviation of the color filter. Furthermore, since the microlens is inevitably formed at a position close to the substrate, the detection error of the base alignment mark when forming the microlens can be reduced, and the displacement of the microlens can be reduced. Accordingly, it is possible to further improve the image quality.

  That is, according to the present invention, the vertical dimension can be reduced without degrading the performance of the device. As a result, it is possible to improve the shading failure, improve the alignment accuracy of color filters and microlenses, and suppress deterioration in image quality due to crosstalk, so that a high-precision and high-definition solid-state imaging device can be obtained. .

  Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments. FIG. 1 is a diagram illustrating a method for manufacturing a solid-state imaging device according to the present embodiment. As shown in FIG. 1A, a unit pixel cell of a base device includes a light receiving portion (photoelectric conversion portion) 42 formed on a substrate 41, an electrode 43 formed between each light receiving portion 42, and interlayer insulation. The film 44, the light shielding film 45, and the protective film 46 are combined with a convex region 47 as a charge transfer portion.

  First, as shown in FIG. 1B, a color filter material 49 is directly applied to the entire surface including the concave regions 48 (regions of the light receiving portion 42) between the convex regions 47 by spin coating or the like. By doing so, the above-mentioned striation can be improved as compared with the case where the color filter material is embedded in a state having a high step through the resist layer patterned as in the case of the above-mentioned JP-A-3-98002. it can.

  In this case, the color filter material 49 may be a dyed substrate or a colored color resist. If there is a problem in adhesion or applicability, an adhesion enhancer (for example, hexamethyldisilazane) may be applied in a gas phase to the surface of the base device, or a surfactant may be added in the color filter material 49. It can respond by adding. However, in order to uniformly embed the color filter material 49 in the recessed area 48 of the light receiving portion 42, it is better to optimize the viscosity of the color filter material 49 to be applied. That is, for example, by adjusting the viscosity to a low viscosity of 10 CP or less and applying the color filter material 49 with a spin at a relatively low speed of 2000 rpm or less, the occurrence of the striation can be prevented.

  Next, the uniformly applied color filter material 49 is subjected to pattern transfer exposure in order to leave the color filter material 49 in a predetermined region, and then the following development processing is performed. That is, when the color filter material 49 is a substrate to be dyed, a dyeing process and a fixing process using tannic acid / tartar are performed. In the case of a color resist, a hardening process by a heat treatment is performed instead of the fixing process. In this way, as shown in FIG. 1C, the color filter 50 of the specific color is formed only in the predetermined area centered on the light receiving unit 42 related to the specific color.

  In that case, since the edge of the remaining color filter 50 is formed in a forward tapered shape, it is possible to ensure continuity with the color filters of other colors that are subsequently formed adjacent to each other. Further, in the photolithography after the color filter material 49 is applied, the alignment target mark formed on the base can be directly detected from the surface of the color filter material 49 that is close to the substrate 41. Therefore, the detection error is extremely small as compared with the case where detection is performed from a position far from the substrate 41 through the thick flattening film as in the case of the above-mentioned Japanese Patent Application Laid-Open No. 3-98002, as shown in FIG. The finished pattern shape has good symmetry.

  Thereafter, the same color filter forming process as described above is repeated for a predetermined number of colors, so that all color filters 50, 51, 52 are formed as shown in FIG. In this state, the step of several μm existing in the underlying device in FIG. 1A is suppressed to about 1/10 or less and is substantially flattened. At the same time, the color filters 50, 51, 52 formed adjacent to each other are continuously formed, and the image quality can be improved.

  In addition, since the substantial film thickness of the color filters 50, 51, 52 embedded in the recessed area 48 is more than twice the normal thickness, the degree of freedom in increasing the color density of the color filters 50, 51, 52 is increased. It is possible to dramatically improve and improve the image quality. In addition, if the color density is the same as before, the degree of freedom is greatly reduced in terms of reducing the amount of dye added (dispersion amount or dissolution amount) for the purpose of improving the storage stability and characteristics (resist sensitivity) of color resist materials. To improve. That is, according to the present embodiment, it is possible to improve the hue and improve the characteristics of the color resist while reducing in the Z direction.

  Next, after the color filters 50, 51, 52 are formed, an overcoat layer is formed of a transparent material such as acrylic in order to flatten the minute steps and protect the color filters 50, 51, 52. Next, although not described in detail, the process proceeds to a microlens formation step as in the case of manufacturing a conventional solid-state imaging device. In this microlens formation process, since the transparent layer such as the flattening layer formed on the color filter in the conventional method for manufacturing a solid-state imaging device has been deleted, An error in detecting the alignment mark can be reduced. Therefore, it is possible to further improve the image quality.

  As described above, in the present embodiment, the color filter material 49 is directly applied to the entire surface of the underlying device so as to embed the recessed region 48 (the region of the light receiving unit 42). Therefore, the striation can be improved as compared with the case where the color filter material is embedded from a high position through the patterned resist layer. Next, the color filter material 49 is subjected to pattern transfer exposure and then developed to form the color filter 50. Therefore, the edge of the color filter 50 is formed in a forward tapered shape, and continuity with the color filters 51 and 52 of other colors formed adjacent to each other can be ensured. Further, during the pattern transfer exposure, the base alignment mark can be directly detected from the surface of the color filter material 49 that is close to the substrate 41. Therefore, the detection error can be reduced and the deterioration of the image quality can be reduced.

  In addition, the substantial thickness of the embedded color filters 50, 51, 52 is more than twice the normal thickness, and the degree of freedom to increase the color density of the color filters 50, 51, 52 is the same as the conventional color density. For example, the degree of freedom to improve the characteristics by reducing the amount of dye added to the color resist material can be improved while reducing in the Z direction.

  Also, when forming a microlens, a conventional transparent layer such as a flattening layer is not formed, so that errors in detecting a base alignment mark can be reduced. Therefore, it is possible to further improve the image quality.

It is a figure which shows the manufacturing method of the solid-state imaging device of this invention. It is sectional drawing of the single cell in the conventional CCD solid-state imaging device. It is a conceptual diagram of the optical system in the single cell of FIG. It is characteristic explanatory drawing of a lens whose exit pupil position is extremely short. It is explanatory drawing of the bad influence which the position shift of a base device and a color filter has on image quality. It is explanatory drawing of the manufacturing method of the conventional optical color filter for solid-state image sensors.

41 ... substrate,
42. Light receiving part (photoelectric conversion part),
43 ... electrodes,
44 ... interlayer insulating film,
45 ... light shielding film,
46 ... Protective film 47 ... Convex region,
48 ... recessed area,
49 ... Color filter material,
50, 51, 52 ... Color filters.

Claims (5)

A unit cell composed of a convex region composed of a transfer region formed on a substrate, a concave region composed of a light receiving region adjacent to the convex region on the substrate, and a color filter formed on the unit cell And a solid-state imaging device having a microlens,
The convex region and the concave region have a protective film on their surfaces,
The color filter is directly embedded in the recessed area Rutotomoni extends to the center portion of the projecting portion positioned on opposite sides of the recess area,
Adjacent the color filter is to ensure continuity edge portion overlap one another,
The surfaces of the plurality of color filters having overlapping continuity are substantially flat,
One edge portion of the overlapping edge portions has a forward tapered shape, while the other edge portion rides on the one edge portion,
The convex regions sequentially stacked layers insulating film is configured to cover the electrode with the light shielding film and the protective film,
In the convex region, the protective film is in contact with an upper surface of the light shielding film and is in contact with a lower surface of the color filter. The solid-state imaging device according to claim 1,
A solid-state imaging device, wherein a surfactant is added to the color filter. It is a manufacturing method of the solid-state imaging device according to claim 1,
The above color filter
Extends to the central portion of the convex portion located on both sides of the unrealized the recessed area a predetermined recessed area after applying a color filter material having a viscosity of less than 10CP on columns of the unit cells at 2000rpm following rotational speed The step of forming a pattern and directly embedding the color filter material in the concave region is repeated as many times as the number of colors of the color filter so that adjacent color filters are in contact with each other. Manufacturing method of solid-state imaging device. In the manufacturing method of the solid-state imaging device according to claim 3,
A method for manufacturing a solid-state imaging device, wherein a dyeable polymer material made of a photosensitive resin is used as the color filter material. In the manufacturing method of the solid-state imaging device according to claim 3,
A method of manufacturing a solid-state imaging device, wherein a color resist is used as the color filter material.

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