JP2009117570A - Photoelectric conversion device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent wrinkles and cracks on a protective film close to the step of an opening, in a photoelectric conversion device in which a color filter constituted of a color resist film is formed on the opening, the protective film is formed thereon, and then a top support substrate made of glass, and the like, is bonded thereon. <P>SOLUTION: A color resist film 56 is expanded to the outer edge of an opening 92, and a protective film 58 is stacked thereon. The protective film 58 is formed selectively so as to cover the color resist film 56. On a top structural layer 54, made up of a stacked interlayer insulating film, and the like; an opening 92 is formed, a planarizing frame 90 is formed, by using the top metal wiring layer of the top structural layer 54 so as to surround the opening; and the surface of the top structural layer 54 on the outer edge of the opening 92 is planarized. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a photoelectric conversion device in which a color filter is embedded in an opening formed at a position of a light receiving portion, and a protective film is laminated thereon.

  In recent years, in order to reduce the size of a photoelectric conversion device including a photoelectric conversion element, a chip size package (CSP) in which wiring is taken out from the side surface of the element has been applied.

  FIG. 3 is a partial cross-sectional view of a conventional photoelectric conversion device in which CSP is applied to the photoelectric conversion element. On the upper surface of the semiconductor substrate 2, there are provided a light receiving unit 6 in which a diffusion layer 4 constituting a photodiode is formed, and a circuit unit 8 that is disposed around the light receiving unit 6 and performs signal processing on a received light signal. On the surface of the semiconductor substrate 2, an upper structure layer 18 composed of a plurality of interlayer insulating films 10, 12, 14 and a plurality of metal wiring layers is laminated. The metal wiring layer is made of, for example, an aluminum (Al) film, and the wiring 20 and the planarization pad 22 are formed in the circuit unit 8 by the first Al layer. Here, the planarization pad 22 is disposed in a region between the wirings 20 and alleviates unevenness on the surface of the interlayer insulating film 12 to be stacked next. The configuration shown in FIG. 3 has a two-layer wiring structure. A second Al layer is laminated on the surface of the interlayer insulating film 12 and is patterned to form a wiring 24 in the circuit portion 8.

  An opening 26 is formed in the upper structure layer 18 corresponding to the position of the light receiving portion 6 in order to increase the light incident efficiency to the photodiode of the light receiving portion 6. A color resist film 28 is embedded in the opening 26 as a color filter. A protective film 30 is laminated on the upper surfaces of the color resist film 28 and the upper structure layer 18. The protective film 30 has a moistureproof function for the color resist film 28.

In the CSP, an upper support base 32 is bonded to the upper surface of the upper structural layer 18 on which the protective film 30 is laminated by a resin layer 34, and a lower support base 36 is bonded to the lower surface of the semiconductor substrate 2 by a resin layer 38. The upper support base 32 is made of a light-transmitting substrate such as glass, and allows light from the outside to enter the light receiving unit 6.
JP 2005-332917 A

  When the resin layer 34 and the upper support base 32 are laminated on the protective film 30 as in the above CSP, there is a problem that wrinkles and cracks occur in the protective film 30 near the edge of the opening 26. . This is considered to be because there is a difference in shrinkage ratio between the upper support base 32 or the resin layer 34 and the protective film 30. In particular, a step is present between the upper surface of the upper structure layer 18 and the surface of the color resist film 28 at the edge of the opening 26. Further, when the color resist film applied to the upper surface of the upper structure layer 18 is removed by etching and left only inside the opening 26, a gap may be formed between the side surface of the opening 26 and the color resist film 28. Therefore, the protective film 30 is bent at the step of the opening 26 or enters the gap with the color resist film 28 to have a shape / structure different from that of the other parts. Corresponding stresses tend to concentrate, and wrinkles and cracks are likely to occur.

  In addition, although the planarization pad 22 can be roughly planarized, fine undulations corresponding to the gap between the planarization pads 22 remain. As a result, undulations are also formed on the surface of the upper structural layer 18, which reduces the adhesion between the protective film 30 and the surface of the upper structural layer 18, or causes stress density, thereby causing wrinkles and wrinkles. Cracks can be easily generated.

  The wrinkles and cracks affect the function of the protective film 30 with respect to the color resist film 28 and may cause a problem in the reliability of the photoelectric conversion device.

  The present invention has been made to solve the above problems, and an object thereof is to provide a photoelectric conversion device in which a protective film is suitably formed in an opening provided corresponding to the position of a light receiving portion.

  The photoelectric conversion device according to the present invention includes a semiconductor substrate on which a light receiving portion is formed, an upper structural layer stacked on the semiconductor substrate, and an opening formed in the upper structural layer corresponding to the position of the light receiving portion. And an optical filter selectively formed in the opening and the outer edge thereof, and the opening and the outer edge where the optical filters are stacked are selected. A filter protective film that covers the optical filter and a transparent substrate that is bonded to the upper structure layer on which the filter protective film is formed via a resin layer.

  According to the present invention, the optical filter composed of a photoresist such as a color resist is disposed not only inside the opening but also to the outer edge thereof. The surface of the optical filter becomes gentler than the step of the opening covered by the optical filter. By forming a protective film on the optical filter, the bending of the protective film can be relaxed and the uniformity can be improved. Thereby, stress concentration is relieved and the generation of wrinkles and cracks can be suppressed. Further, by setting the protective film to the outer edge of the opening, the absolute amount of distortion in the entire protective film is reduced, and this point is also considered effective in suppressing wrinkles and the like. Furthermore, by placing a frame under the outer edge of the opening and improving the flatness of the surface of the outer edge, the adhesion of the protective film is improved and the stress is dispersed, thereby suppressing wrinkles and the like. It is done.

  Hereinafter, embodiments of the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings. The present embodiment is, for example, a photoelectric conversion device assembled as a CSP, and FIG. 1 is a schematic cross-sectional view of the main part thereof. The schematic structure of the photoelectric conversion device 50 shown in FIG. 1 is that a photoelectric conversion element 60 comprising a semiconductor substrate 52 and an upper structure layer 54, a color resist film 56, a protective film 58 and the like laminated on the surface of a semiconductor substrate 52 is provided with a support member 62. , 64. In the CSP, the wiring formed in the upper structure layer 54 is connected to the external wiring formed along the side surface of the laminate, and the external wiring is extended to the back surface of the laminate, for example, a hemispherical external terminal. Connected. Further, a protective film for preventing corrosion or the like is formed on the side surface and the back surface of the laminate on which the external wiring is arranged. In FIG. 1, the structure other than the laminated body is not shown, but the structure is basically the same as that shown in FIGS.

  The semiconductor substrate 52 is, for example, a silicon substrate, and a light receiving unit 70 and a circuit unit 72 are provided on the surface thereof. In the light receiving unit 70, a diffusion layer 74 constituting a photodiode is formed. In the circuit portion 72, a structure of a circuit element (not shown) such as a CMOS is formed.

  After the structure of various circuit elements on the surface of the semiconductor substrate 52 is formed as described above, a structure such as a wiring structure or a protective film is formed on the semiconductor substrate 52. For example, an antireflection film (not shown) made of, for example, a silicon nitride film is laminated on the surface of the semiconductor substrate 52 on which the gate electrode of the MOS transistor is formed, and a first interlayer insulating film 80 is laminated thereon. Further, a first Al layer is deposited and laminated as a metal film by vapor deposition or the like. Incidentally, the interlayer insulating film is formed using SOG (Spin On Glass) or the like.

  The first Al layer is patterned using a photolithography technique, and the first layer wiring 82 and the planarization pad 84 are formed in the circuit portion 72 by the first Al layer. Here, the planarization pad 84 is disposed in a region between the wirings 82 and reduces unevenness on the surface of the interlayer insulating film 86 to be stacked next.

  After the interlayer insulating film 86 is stacked, a second Al layer is stacked thereon. Similarly to the first Al layer, the second Al layer is formed by vapor deposition or the like so as to obtain good flatness, and then patterned using a photolithography technique. A frame 90 is formed on the circuit portion 72. The flattening frame 90 is a frame-like pattern that is disposed in the vicinity of a position where an opening 92 to be formed later is to be formed and surrounds the opening 92.

  After the patterning of the second Al layer, the interlayer insulating film 94 is stacked thereon, and the stacking of the upper structural layer 54 including the interlayer insulating films 80, 86, 94 and the first Al layer and the second Al layer is completed.

  Thereafter, the interlayer insulating film laminated as the upper structural layer 54 on the light receiving portion 70 is etched back to form the opening 92. Thereby, the interlayer insulating film on the light receiving unit 70 can be thinned, and the light incident efficiency to the light receiving unit 70 can be increased.

  A color resist film 56 is laminated as a color filter on the opening 92 and its outer edge. The color resist film is applied and formed on the entire upper surface of the upper structural layer 54 including the opening 92 by spin coating, and then patterned. As a result, the portion of the color resist film outside the outer edge near the opening 92 is removed, and the color resist film 56 remaining in the opening 92 and its periphery is formed. The color resist film 56 is embedded in the opening 92, and this part functions exclusively as a color filter. Further, the color resist film 56 is extended to the outer edge portion of the opening 92 to cover the step of the opening 92, and a gentle surface is formed on the upper surface of the color resist film 56 so as to straddle the inside and outside of the opening 92. .

  A protective film is laminated on the color resist film 56. This protective film is formed, for example, by laminating a silicon oxide film and a silicon nitride film. For example, a silicon oxide film and a silicon nitride film are deposited on the entire upper surface of the upper structural layer 54 by a method such as CVD, a protective film is formed, and then patterned to selectively cover the color resist film 56. Then, the protective film 58 remaining is formed. The protective film 58 has a moistureproof function for the color resist film 56.

  A support member 62 is laminated on the upper surface of the upper structural layer 54 on which the protective film 58 is laminated. The support member 62 includes an upper support base 98 and a resin layer 100, and the upper support base 98 is bonded to the upper surface of the photoelectric conversion element 60 on which the upper structure layer 54 is formed by the resin layer 100. The upper support base 98 is made of a light-transmitting substrate such as glass, and allows light from the outside to enter the light receiving unit 70. The resin layer 100 is formed using an epoxy resin or the like.

  On the other hand, a support member 64 is stacked on the lower surface of the photoelectric conversion element 60, that is, on the back surface of the semiconductor substrate 52. The support member 64 includes a lower support base 102 and a resin layer 104, and the lower support base 102 is bonded to the lower surface of the photoelectric conversion element 60 by the resin layer 104. The lower support base 102 can also be made of a substrate such as glass. Similarly to the resin layer 100, the resin layer 104 is formed using an epoxy resin or the like.

  FIG. 2 is a schematic diagram showing a planar layout 110 in the vicinity of the opening 92 of the photoelectric conversion device 50 in association with the cross-sectional structure 112 along the line A-A ′ shown in the layout 110. For example, the flattening frame 90 is also formed in a rectangle corresponding to the opening 92 formed in a rectangle. The lower limit value of the distance α between the inner edge of the flattening frame 90 and the opening 92 is determined according to the processing accuracy of the opening 92 formed after the flattening frame 90. That is, α is set so that the planarization frame 90 is not exposed on the side surface of the opening 92 in consideration of the alignment accuracy of the etching mask when forming the opening 92 and the amount of overetching in the lateral direction of etching. Is done.

  The distance β between the end portion of the color resist film 56 and the opening 92 is set in consideration of processing accuracy when forming the color resist film 56 by patterning, and the color resist film 56 is considered in consideration of misalignment and the like. It is determined so as to surely get on the outer edge of the opening 92.

  The flattening frame 90 flattens undulations that may occur on the surface of the interlayer insulating film 86 by the flattening pad 84, the wiring 82, and the like thereunder. That is, the flatness is improved on the surface of the upper structure layer 54 on the region where the flattening frame 90 is disposed, and the surface of the flat upper structure layer 54 surrounding the outside of the opening 92 can be formed. By arranging the bonding surface between the protective film 58 and the upper structural layer 54 in the region where the flatness is improved, the adhesion at the bonding surface between the protective film 58 and the upper structural layer 54 is improved and the stress is uniform. Is improved.

  From this point of view, it is preferable that the bonding surface between the protective film 58 and the upper structural layer 54 be within the arrangement region of the planarizing frame 90. In this case, the distance γ between the outer edge of the flattening frame 90 and the opening 92 is set to be larger than the distance between the opening 92 and the end of the protective film 58, and β> α is set. The

It is typical sectional drawing of the principal part of the photoelectric conversion apparatus which concerns on embodiment of this invention. It is the schematic diagram which matched and represented the planar layout of the opening part vicinity of the photoelectric conversion apparatus which concerns on embodiment of this invention, and a vertical cross-section. It is a fragmentary sectional view of the photoelectric conversion apparatus of the conventional CSP structure.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 50 Photoelectric conversion apparatus, 52 Semiconductor substrate, 54 Upper structure layer, 56 Color resist film, 58 Protective film, 60 Photoelectric conversion element, 62,64 Support member, 70 Light-receiving part, 72 Circuit part, 74 Diffusion layer, 80,86, 94 Interlayer insulation film, 82, 88 wiring, 84 flattening pad, 90 flattening frame, 92 opening, 98 upper support base, 100, 104 resin layer, 102 lower support base.

Claims (3)

A semiconductor substrate having a light receiving portion formed thereon;
An upper structural layer laminated on the semiconductor substrate;
An opening formed in the upper structure layer corresponding to the position of the light receiving portion;
An optical filter made of a photoresist having a predetermined light transmission characteristic, selectively formed in the opening and its outer edge,
A filter protective film that is selectively formed in the opening and the outer edge where the optical filter is laminated, and covers the optical filter;
A transparent substrate bonded via a resin layer to the upper structure layer on which the filter protective film is formed;
A photoelectric conversion device comprising: The photoelectric conversion device according to claim 1,
The upper structural layer includes a frame made of a band-shaped metal film disposed along the outer edge portion and surrounding the opening portion under the outer edge portion where the optical filter and the filter protective film are stacked. A photoelectric conversion device characterized by comprising: The photoelectric conversion device according to claim 2,
The upper structural layer is formed by laminating at least one metal wiring layer and an interlayer insulating film,
The frame is formed using an uppermost layer of the metal wiring layers;
A photoelectric conversion device characterized by the above.

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