JP2006344754A - Solid state imaging device and its fabrication process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small solid state imaging device in which sensitivity is enhanced sharply by improving the amount of transmitting light when the opening width of a light shielding film is decreased. <P>SOLUTION: The solid state imaging device comprises a semiconductor substrate 11 on which a plurality of photoelectric converting sections 17 are formed, a light shielding film 19 formed on the semiconductor substrate 11 above the photoelectric converting section 17 and provided with a plurality of openings 20 for respective photoelectric converting sections 17, and a high refractive index layer 125 formed in the opening 20. The opening 20 has an opening width smaller than the maximum wavelength expressed in terms of the wavelength of light incident to the photoelectric converting section 17 in the vacuum, and the high refractive index layer 125 is composed of a high refractive index material having such a refractive index as passing the light of maximum wavelength through the opening 20. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a solid-state imaging device used for a digital camera or the like, and more particularly to a light receiving cell constituting the solid-state imaging device.

In a general solid-state imaging device, a plurality of light receiving cells are formed on a semiconductor substrate. Each light receiving cell photoelectrically converts light incident through an opening of the light shielding film and color separation formed on the light shielding film. And a color filter that performs the above. As a color filter, a primary color filter or a complementary color filter is generally used. The primary color filter uses red (R), blue (B), and green (G). The complementary color filter uses cyan (C), which is a complementary color of red, magenta (M), which is a complementary color of green, and a complementary color of blue. Some yellow (Y) is used. In general, in a solid-state imaging device using a complementary color filter, signals obtained through these three colors and green (G) are used. Then, one of the above colors is assigned to each light receiving cell in a certain pattern. By doing so, each light receiving cell generates a signal according to the luminance of the color signal color-separated by the color filter. (For example, see Patent Documents 1 and 2.)
Further, in order to realize the high sensitivity by enlarging the above signal, a high S / N ratio is achieved by forming microlenses and the like above and below the color filter. (For example, refer to Patent Document 3.)
As a means for achieving high sensitivity, a high refractive index material and a low refractive index material formed so as to surround the periphery of the high refractive index material are placed in the opening of the light shielding film, and the high refractive index material and the low refractive index material are reduced. There is a proposal of a method of collecting light using total reflection at the boundary with the refractive index material. (For example, see Patent Document 4)
FIG. 7 shows a cross-sectional view of the light receiving cells 1a, 1b, and 1c of the conventional solid-state imaging device.

  Each light receiving cell is formed by forming an insulating layer 13, a metal layer 14, and a color filter layer 15 on the basis of a semiconductor substrate 11 made of silicon to which an N-type impurity is added. At this time, the photoelectric conversion layer 12 is formed in the semiconductor substrate 11. The photoelectric conversion layer 12 is an N-type region formed by ion-implanting P-type impurities into the semiconductor substrate 11 to form a P-type well 16 and further ion-implanting N-type impurities into the P-type well 16. This is a layer having a certain photoelectric conversion portion 17.

  The insulating layer 13 is a layer composed of an interlayer film 18 provided on the photoelectric conversion layer 12 in order to insulate the photoelectric conversion layer 12 and the metal layer 14.

  The metal layer 14 is a layer including the light shielding film 19 and the inner lens 30. In forming the metal layer 14, an interlayer film 29 as a planarizing layer is formed on the light shielding film 19 after the light shielding film 19 is formed. Further, after the interlayer film 29 on the light shielding film 19 is formed, the inner lens 30 is formed. An interlayer film 31 is formed on the inner lens 30 so as to cover the surface of the inner lens 30.

  The color filter layer 15 is a layer having a color filter composed of a blue filter film 21a, a green filter film 21b, and a red filter film 21c, and an interlayer film 22 on the color filter.

Incident light 24 is incident from above the light receiving cells 1a, 1b, and 1c, and is collected by the microlens 23 formed on the color filter, and the blue filter film 21a, the green filter film 21b, or the red filter film 21c. Transparent. The light transmitted through the color filter is condensed again by the inner layer lens 30 and then reaches the photoelectric conversion unit 17 through the opening 20. When the light receiving cells 1a, 1b and 1c are large light receiving cells having a square of 5.6 μm on one side as in the prior art, the width of the opening 20 is as large as 2.0 μm or more. Therefore, for example, visible light having a red wavelength of 650 nm on the long wavelength side can be sufficiently transmitted through the opening without being affected by the width of the opening. Further, light having a near-infrared wavelength on the long wavelength side used in a dark field camera or the like can sufficiently pass through the opening.
Japanese Patent Laid-Open No. 10-341012 JP-A-5-326902 JP 2000-164837 A JP-A-6-224398

However, when the light receiving cell is miniaturized and reduced in size to realize a higher pixel of the solid-state imaging device, the width of the opening of the light shielding film is red (R) light, green (G) light, and blue (B) light. It approaches the wavelength of visible light such as. When the width of the opening of the light shielding film is smaller than the wavelength of visible light, the wavelength band of the light having passed through the color filter is equal to or greater than a specific wavelength determined by the width of the opening. Light is blocked, and light having a wavelength longer than the cut-off wavelength cannot be transmitted through the opening, and cannot reach the photoelectric conversion unit. In this case, in particular, a decrease in the transmittance of red (R) light on the long wavelength side becomes significant. For example, when light having a red wavelength of 650 nm is transmitted through a narrow opening in vacuum, the light having a wavelength of 650 nm is filled with a silicon oxide film (SiO ₂ ) having a refractive index of 1.45 in vacuum. The opening has a wavelength of 450 nm which is a value obtained by dividing the wavelength by the refractive index (650 nm / 1.45 = 450 nm). Therefore, the transmittance of light having a wavelength of 650 nm in this vacuum becomes almost zero when the width of the opening is about 450 nm, but actually starts decreasing from around the opening width of 650 nm. Therefore, when the material filling the opening is a low refractive index material such as a silicon oxide film (SiO ₂ ), light having a wavelength substantially equal to or larger than the width of the opening cannot be transmitted.

In particular, when the light receiving cell is a small light receiving cell having a square shape with a side of 3.2 μm or less, the width of the opening becomes 1.0 μm or less. With such a narrow opening width, a long wavelength red wavelength visible light or a long wavelength side light such as 1.0-2.0 μm near infrared light is a flat surface that fills the opening. In particular, when the layer is made of a low refractive index material, it cannot be transmitted. For example, when the planarizing layer filling the opening is made of a low refractive index silicon oxide film (SiO ₂ ) having a refractive index of 1.5, a low refractive index resin having a refractive index of 1.3 to 1.7, or the like. In this case, light having a long wavelength cannot be transmitted through the opening.

  In view of the above, an object of the present invention is to provide a small solid-state imaging device capable of greatly improving sensitivity by improving the amount of transmitted light when the opening width of the light shielding film is reduced.

  In order to achieve the above object, a solid-state imaging device according to the present invention includes a semiconductor substrate, a photoelectric conversion unit formed on the semiconductor substrate, and an opening formed so as to be positioned above the photoelectric conversion unit. A light-shielding film disposed on the semiconductor substrate and a high refractive index layer formed in the opening, wherein the opening is a vacuum of light incident on the photoelectric conversion unit through the opening The high refractive index layer has a refractive index that transmits light of the maximum wavelength of light incident on the photoelectric conversion unit through the opening. It is comprised from the high refractive index material which has. Here, the solid-state imaging device further includes a filter film that is installed on the light-shielding film so as to be positioned above the opening, and transmits light in a specific wavelength range, and the opening includes the filter film May have an aperture width smaller than the maximum wavelength of the light to be transmitted.

  In the solid-state imaging device according to the present invention, utilizing the principle that the wavelength of the light passing through the opening is a value obtained by dividing the wavelength in vacuum by the refractive index (wavelength in vacuum / (refractive index = N)), By filling the opening with a high refractive index material, the wavelength of light transmitted through the opening is made relatively small. Therefore, when the refractive index in the opening is N, the maximum wavelength in the transmission wavelength band of the light transmitted through the opening is converted to the wavelength in vacuum, and the refraction of the high refractive index material filling the opening It becomes larger by a factor (N times). As a result, the width of the opening is narrowed, and the opening is filled with a high refractive index material even when the width of the opening is equal to or less than the wavelength of the light to be transmitted in vacuum. Thus, light can be transmitted. That is, it is possible to realize a small solid-state imaging device that greatly improves the sensitivity of light on the long wavelength side and can greatly improve the sensitivity.

  Moreover, in order to achieve the said objective, the said high refractive index layer may be filled in the said opening part.

  By adopting the above configuration, the high refractive index material is filled over the entire area in the opening, and the average refractive index in the entire opening can be increased, so that the light transmitted through the opening is in a vacuum. Can be greatly shifted to the long wavelength side, and the sensitivity of light on the long wavelength side can be further improved.

  Also, as shown in Patent Document 4, a low refractive index material is placed so as to surround the periphery of the high refractive index material in the opening, and the light is condensed using total reflection at the boundary between the high refractive index material and the low refractive index material. In the case of this method, since it is necessary to positively introduce a low refractive index material into the opening, the width of the high refractive index material in the opening is changed from the width of the opening to the width of the low refractive index material in the opening. The value obtained by subtracting Therefore, the wavelength of light that can be substantially transmitted in this case is always determined by the width of the high refractive index material that is smaller than the width of the opening. For this reason, the substantial aperture width is reduced, and the light having a longer transmission wavelength is restricted, which is disadvantageous for improving the sensitivity. However, with the above configuration, the width of the opening becomes the width of the high refractive index material in the opening, and the substantial opening width can be increased. Therefore, an improvement in sensitivity can be realized.

  In order to achieve the above object, the high refractive index layer may be made of a high refractive index material having a refractive index of 1.8 or more.

  Using the high refractive index material having a refractive index of 1.8 or more as the material constituting the high refractive index layer filling the opening as in the above configuration, the width of the opening is 1.0 μm or less. Even in this case, it is possible to transmit light having a long wavelength side wavelength such as near-red light having a long wavelength in visible light or near infrared light having a wavelength of 1.0 to 2.0 μm.

  In order to achieve the above object, the thickness of the high refractive index layer may be substantially the same as the thickness of the light shielding film or thicker than the thickness of the light shielding film.

  By adopting the above configuration, the cutoff wavelength converted to the wavelength in vacuum is set to the longer wavelength side by making the thickness of the material with a high refractive index in the opening equal to or greater than the thickness in the height direction of the opening. Therefore, the transmission wavelength band on the long wavelength side of the light transmitted through the opening can be widened, and the sensitivity on the long wavelength side can be improved.

  Moreover, in order to achieve the said objective, the said high refractive index layer may have a convex lens shape, and may collect the light which injects into the said photoelectric conversion part through the said opening part.

  By adopting the above configuration, the upper surface of the high refractive index material that transmits the light in the opening has a convex lens shape and can be condensed just above the opening, so the width of the opening is close to the wavelength of visible light In particular, the light collection rate can be significantly improved.

  Further, even when the light receiving cell is miniaturized and the cell pitch is reduced in the lateral direction, as shown in FIG. 7 and Patent Document 3, the inner lens and the interlayer film above and below the inner lens are not changed. Since it is necessary, the vertical dimension on the light-shielding film is the same as the conventional one. Therefore, although the cell pitch is reduced in the horizontal direction, the vertical dimension cannot be reduced, so that it is difficult to collect light in a narrow opening, and the light collection efficiency is extremely deteriorated. However, with the above configuration, the inner lens above the light shielding film, which was necessary in the structure of the conventional solid-state imaging device, can be omitted, and the height of the entire light receiving cell can be reduced. The above problems do not occur.

  In order to achieve the above object, the high refractive index material may be any one of titanium oxide, tantalum oxide, and niobium oxide.

  By using a high refractive index material such as titanium oxide, tantalum oxide, niobium oxide or hafnium oxide for the high refractive index layer as described above, a refractive index of 1.5, which is commonly used as an insulating film, is generally used. Compared to silicon oxide, the refractive index in the opening can be made particularly large, and the transmission wavelength band of light transmitted through the opening converted to a wavelength in vacuum can be shifted to the long wavelength side. Therefore, the sensitivity on the long wavelength side can be further improved.

  In order to achieve the above object, the opening width may be 1.0 μm or less.

  With the above configuration, the effect of broadening the transmission wavelength band of light transmitted through the opening to the long wavelength side in the band of 1.0 μm or less which is the main absorption band of silicon constituting the photoelectric conversion unit is large. Therefore, a remarkable improvement in sensitivity can be realized.

  As described above, in the solid-state imaging device of the present invention, a fine light receiving cell can be realized without sacrificing sensitivity, and the number of pixels in a specific optical size (for example, 1/4 inch) of the imaging unit can be reduced. Therefore, the camera using the solid-state imaging device of the present invention can realize a high-quality camera having high sensitivity and high pixels.

  In order to achieve the above object, a method of manufacturing a solid-state imaging device according to the present invention forms a light-shielding film on a semiconductor substrate on which a photoelectric conversion unit is formed, and is positioned above the photoelectric conversion unit in the light-shielding film. An opening forming step for forming an opening, and a high refractive index layer forming step for forming a high refractive index layer in the opening and on the light-shielding film. In the high refractive index layer forming step, the high refractive index The high refractive index layer having a film thickness that makes the surface of the layer flat is formed. Here, in the high refractive index layer forming step, the high refractive index layer having a film thickness of ½ or more of the width of the opening may be formed.

  By adopting the above configuration, a high refractive index layer having a high refractive index is formed in the opening, and a high refractive index layer having a high refractive index is continuously formed on the high refractive index layer in the opening. Since the upper part of the opening can be flattened with a high refractive index layer having a high refractive index, light incident on the opening can be incident on the opening without irregular reflection, and a decrease in sensitivity can be prevented. .

  In order to achieve the above object, the method of manufacturing the solid-state imaging device may further include a flattening step of flattening the surface of the high refractive index layer.

  By having the above configuration, after forming a high refractive index layer having a high refractive index in the opening, and further continuously forming a high refractive index layer having a high refractive index on the high refractive index layer in the opening, Since the high refractive index layer having a high refractive index is flattened and etched by CMP or the like, the flatness of the high refractive index layer above the opening can be increased, and irregular reflection of light incident on the opening can be minimized. As a result, it is possible to minimize the variation between the light receiving cells with the amount of light that can enter the opening, and to greatly improve the sensitivity variation.

  In order to achieve the above object, the method for manufacturing the solid-state imaging device may further include a lens forming step of processing the high refractive index layer located above the opening into a convex lens shape.

  By having the above configuration, after forming a high refractive index layer having a high refractive index in the opening, and further continuously forming a high refractive index layer having a high refractive index on the high refractive index layer in the opening, Since the inner lens is formed using a high refractive index layer having a high refractive index, the special film forming process necessary for the conventional inner lens is eliminated, and the process for manufacturing the solid-state imaging device is reduced. Can do. As a result, an inexpensive solid-state imaging device can be provided. In addition, since the inner lens is in front of the light shielding film, even when the width of the opening is small, light can be efficiently collected and high sensitivity can be realized.

  The solid-state imaging device according to the present invention has an opening portion even when the width of the opening portion is narrowed by using a high refractive index material having a high refractive index for the opening portion of the light shielding film formed on the photoelectric conversion portion. The transmission wavelength band of the transmitted light can be kept large. Thereby, even when the light receiving cell of the solid-state imaging device becomes small and the opening becomes small, it is possible to prevent a significant decrease in sensitivity on the long wavelength side, and it is possible to realize downsizing and high sensitivity. . Furthermore, by continuously forming and flattening a high refractive index material filling the opening above the opening, it is possible to reduce irregular reflection of light above the opening, preventing a decrease in sensitivity and at the same time between the light receiving cells. High image quality can be achieved by suppressing variations in sensitivity. In addition, after continuously forming a high refractive index material filling the opening also on the opening, a microlens is formed using the high refractive index material, so that a high-sensitivity and high S / N solid-state imaging device can be obtained. Therefore, a high-quality camera can be realized.

  Hereinafter, a solid-state imaging device according to an embodiment of the present invention will be described with reference to the drawings. In addition, this invention is not limited by the following embodiment.

(Embodiment 1)
FIG. 1 is a cross-sectional view of light receiving cells 111a, 111b, and 111c of the solid-state imaging device according to Embodiment 1 of the present invention. The semiconductor substrate 11, the photoelectric conversion layer 12, and the insulating layer 13 of each light receiving cell have the same structure as that of the conventional light receiving cell shown in FIG.

  The metal layer 114 is a layer including the light shielding film 19 and the intralayer lens 30 as in the conventional solid-state imaging device. However, in the solid-state imaging device according to Embodiment 1 of the present invention, the metal layer 114 is a light-shielding film. After 19 is formed, it has a high refractive index layer 125 formed so as to fill the opening 20 of the light shielding film 19 and made of a high refractive index material. At this time, like the structure of the conventional light receiving cell, the interlayer film 29 and the inner lens 30 are formed above the light shielding film 19, and the interlayer film 31 is formed on the inner lens 30. . Further, the color filter layer 15 including the interlayer film 22 is formed on the metal layer 114, and the microlens 23 is formed on the color filter layer 15.

  In the solid-state imaging device of the first embodiment, the light that has been condensed by the microlens 23 and transmitted through the color filter layer 15 is again condensed by the intralayer lens 30, and then the high refractive index layer 125 is formed. It reaches the photoelectric conversion unit 17 through the opening 20.

  Here, the opening 20 has an opening width smaller than the maximum wavelength converted to the wavelength in vacuum of the light incident on the photoelectric conversion unit 17. That is, the aperture width is smaller than the maximum wavelength of red (R) color light in vacuum. The high refractive index material has a refractive index that transmits light having a maximum wavelength converted to a wavelength in vacuum of light incident on the photoelectric conversion unit 17 through the opening 20. That is, it has a refractive index that transmits red (R) light incident on the photoelectric conversion unit 17 through the opening 20.

  FIG. 2 is a diagram showing the transmission characteristics of the color filter layer 15 and the opening 20.

It is well known that light having a wavelength equal to or greater than the width of the opening 20 among the light incident on the opening is difficult to transmit through the opening 20 and is blocked. When the width of the opening 20 is wide (for example, 2 μm or more), since the width of the opening 20 is wide, the cutoff wavelength 101 is far longer than the red spectrum. Therefore, the light transmitted through the red (R), green (G), and blue (B) spectral color filters can pass through the opening 20. However, when the width of the opening 20 becomes narrow due to miniaturization of the light receiving cells 111a, 111b, and 111c, the width of the opening 20 is narrow, so that the cutoff wavelength 102 is transmitted through the red (R) filter film 21c. Below the wavelength. As a result, in the opening 20 below the red (R) filter film 21c, the transmittance of red light becomes extremely small, the amount of light that can reach the photoelectric conversion unit 17 is reduced, and the sensitivity may be lowered. There is sex. In the solid-state imaging device according to the present invention, the high refractive index layer 125 is formed in the opening 20 in order to eliminate this problem. By using the high refractive index layer 125 in the opening 20, the wavelength of light transmitted through the opening 20 is 1 / (refractive index = N) of the refractive index with respect to the wavelength in vacuum. And can be made smaller. For example, when titanium oxide (TiO ₂ ) having a refractive index of 2.5 is used as the high refractive index layer 125, the wavelength of light transmitted through the opening 20 is 1/2. The wavelength of red light of 650 nm in vacuum is 260 nm in the opening 20. Therefore, for example, in the opening 20 having an opening width of 650 nm, the wavelength of red light of 650 nm in a vacuum is 260 nm. As a result, the wavelength of the red light 260 nm (650 nm in vacuum) in the opening 20 becomes considerably smaller than the opening width 650 nm, and the red light can sufficiently pass through the opening 20.

When considering the cutoff wavelength, the refractive index in the opening 20 is 1, for example, the cutoff wavelength of the opening 20 having an opening width of 650 nm in terms of the wavelength in vacuum is higher in the opening 20. By embedding with titanium oxide (TiO ₂ ) having a refractive index of 2.5 and setting the refractive index in the opening 20 to 2.5, it is 1625 nm, which is 2.5 times 650 nm in terms of the cutoff wavelength in vacuum. . Accordingly, by filling the inside of the opening 20 with a high refractive index material having a refractive index = N, the cutoff wavelength in vacuum that can be transmitted through the opening 20 can be made N times wider, and the opening width becomes narrower. However, as shown in FIG. 2, the cutoff wavelength 103 can be made larger than visible light. That is, even when the width of the opening 20 becomes small, the cutoff wavelength can be shifted to the long wavelength side by using a material having a high refractive index as a material filling the inside of the opening 20. Can be widened, and the sensitivity on the long wavelength side can be improved.

  The largest cutoff wavelength can be realized by making the width of the high refractive index material in the opening 20 described above the same as the width of the opening 20.

  Further, titanium oxide having a refractive index of 2.5 is exemplified as the high refractive index material constituting the high refractive index layer 125. However, by setting the refractive index in the opening 20 to be 1.8 or more, even when the width of the opening 20 is 1.0 μm or less, light having a wavelength near red of a long wavelength in visible light, Since light having a wavelength on the long wavelength side such as near infrared light of 1.0 to 2.0 μm can be transmitted, the high refractive index material filling the opening 20 is 1.8 or more, particularly 2. The material is not limited to titanium oxide as long as it is a high refractive index material having a refractive index of 2 or more.

  Further, the thickness 28 of the high refractive index material shown in FIG. 1 is substantially the same as the thickness 27 of the light shielding film 19, that is, the thickness 27 of the opening 20 or larger than the thickness 27 of the opening 20, and the opening 20 is filled with the high refractive index material. It is exhausted. As a result, the cutoff wavelength of the opening 20 converted to the wavelength in vacuum can be shifted to the longest wavelength side, so that the transmission band on the long wavelength side can be widened and the sensitivity on the long wavelength side is improved. Can be made.

  Further, by using silicon nitride, titanium oxide, tantalum oxide, niobium oxide, or the like as a high refractive index material filling the opening 20, a refractive index of silicon oxide (about approximately) generally used as an insulating film. 1.5), the refractive index can be particularly large, and the cutoff wavelength of the opening 20 converted to the wavelength in vacuum can be shifted to the longest wavelength side most, so that the transmission band on the long wavelength side The sensitivity on the long wavelength side can be further improved.

  In the solid-state imaging device according to the first embodiment, visible light is exemplified as incident light. However, since the same effect is recognized for the wavelength of near-infrared light, near-infrared light that can be photoelectrically converted by silicon. Even for light in a band of 1.0 μm or less corresponding to the wavelength of 1, the effect of widening the wavelength transmission band to the long wavelength side is great, and a significant improvement in sensitivity can be realized.

  FIG. 3 is a cross-sectional view illustrating a method of forming a structure on the light shielding film 19 in the light receiving cells 111a, 111b, and 111c of the solid-state imaging device according to the first embodiment of the present invention. FIG. 3 shows a process from the process of forming the opening 20 in the light receiving cells 111a, 111b, and 111c of the solid-state imaging device according to the first embodiment to the process of forming the interlayer film 29 above the light shielding film 19.

  In this forming method, first, a patterned resist is formed on the light shielding film 19. That is, a resist is formed on the light shielding film 19 and the resist in a region where the opening 20 is formed is removed. Thereafter, a part of the light shielding film 19 is removed using a resist as a mask by a dry etching technique, and a first step (FIG. 3A) for forming an opening 20 located above the photoelectric conversion unit 17 is performed.

  Next, a second step (FIG. 3B) of forming a high refractive index layer 125 that transmits light in the opening 20 and on the light shielding film 19, and the high refractive index layer 125 in the opening 20 and the light shielding film. A third step (FIG. 3C) further formed on 19 is continuously performed. Thus, the process of planarizing the high refractive index layer 125 on the opening 20 with the high refractive index layer 125 itself can be performed by continuously performing the second process and the third process.

  Finally, a fourth step (FIG. 3D) for forming the interlayer film 29 above the light shielding film 19 having a refractive index smaller than that of the high refractive index layer 125 is performed.

  By performing the above first to fourth steps, the structure on the light shielding film 19 in the light receiving cells 111a, 111b, and 111c of the solid-state imaging device of the first embodiment can be formed. Like the solid-state imaging device of the present invention, when the width of the opening 20 is narrow, when the high refractive index material is continuously formed after the second step of filling the opening 20 with the high refractive index material, the opening The high refractive index material having a concave shape in the portion 20 has a concave portion with a narrower width as the film thickness increases, and finally the left and right side walls of the concave portion come into contact with each other so that the surface is flat. The rate layer 125 can be made. At this time, when the high refractive index material is evenly attached to the plane and side surfaces of the light shielding film 19, the film thickness of the high refractive index layer 125 is set to be 1/2 or more of the width (d) of the opening 20. The recess can be made flat. Since the high refractive index layer 125 is flattened, the surface of the interlayer film 29 above the light shielding film 19 on the high refractive index layer 125 can be formed flat, and the interlayer film 29 is formed by CMP (chemical mechanical polishing) or the like. A planarization step can be eliminated, or a planarization amount and time such as CMP can be reduced.

  When this forming method is applied to a solid-state imaging device having a structure in which the width (d) of the opening 20 is large as in the prior art, the film thickness of the high refractive index layer 125 ( Since d / 2) becomes considerably large, the film thickness of the high refractive index layer 125 becomes large when flattened by the above-described forming method, and there arises a problem that condensing is difficult. Therefore, this forming method is practically effective particularly in the case of the narrow opening 20 in which the width (d) of the opening 20 is 1.5 μm or less.

  When the above forming method is used, the high refractive index layer 125 on the opening 20 can be easily flattened in terms of the characteristics of the solid-state imaging device. As a result, there is no unevenness at the interface with the interlayer film 29, and light can be incident on the opening 20 without irregular reflection at the interface, so that the sensitivity reduction can be greatly improved.

  In the forming method of FIG. 3, the interlayer film 29 on the light shielding film 19 is formed immediately after the high refractive index layer 125 is formed and the surface is flattened, but after the third step of forming the high refractive index material. Furthermore, a fifth step of planarizing the high refractive index layer 125 by CMP or the like may be added. Thereby, the irregular reflection of light at the interface between the high refractive index layer 125 and the interlayer film 29 above the light shielding film 19 can be further reduced, and the sensitivity reduction can be extremely improved. In addition, variation in the amount of light incident on the opening 20 of each light receiving cell can be minimized, and sensitivity variation can be greatly improved.

(Embodiment 2)
FIG. 4 is a cross-sectional view of the light receiving cells 211a, 211b, and 211c of the solid-state imaging device according to Embodiment 2 of the present invention. The semiconductor substrate 11, the photoelectric conversion layer 12, and the insulating layer 13 of each light receiving cell have the same structure as that of the conventional light receiving cell shown in FIG.

  The metal layer 214 is a layer including the light shielding film 19 as in the conventional solid-state imaging device. However, in the solid-state imaging device according to Embodiment 2 of the present invention, the metal layer 214 is formed after the light shielding film 19 is formed. The high refractive index layer 225 is formed to fill the opening 20 of the light shielding film 19 and is made of a high refractive material. At this time, the high refractive index layer 225 is processed into the shape of a convex in-layer lens. As a result, the interlayer film 29 and the inner lens 30 above the light shielding film 19, which are necessary in the structure of the conventional solid-state imaging device, can be omitted, and the overall height of the light receiving cell can be reduced. .

  In the solid-state imaging device according to the second embodiment, the incident light 24 is transmitted through the microlens 23 and the color filter layer 15 and directly through the high-refractive index layer without passing through the intralayer lens 30 of the conventional solid-state imaging device. The light is condensed by the intralayer lens formed at 225 and reaches the photoelectric conversion unit 17. As a result, the high refractive index layer 225 in the opening 20 has a convex in-layer lens shape and can be condensed directly above the opening 20, so that the width of the opening 20 is the wavelength of visible light. In particular, the light condensing rate can be greatly improved when it is close to.

  FIG. 5 is a cross-sectional view illustrating a method of forming a structure on the light shielding film 19 in the light receiving cells 211a, 211b, and 211c of the solid-state imaging device according to Embodiment 2 of the present invention. FIG. 5 shows from the manufacturing process of the opening 20 in the light receiving cells 211 a, 211 b, and 211 c of the solid-state imaging device of Embodiment 2 to the forming process of the interlayer film 31 on the light shielding film 19.

  In this manufacturing method, the first to third steps (FIGS. 5A to 5C) for forming the high refractive index layer 225 by the same method as the method for forming the solid-state imaging device in the first embodiment shown in FIG. )), The fourth to seventh steps of forming an in-layer lens using the formed high refractive index layer 225 itself are added, and thereafter, the interlayer film 31 is formed on the light shielding film 19. The 8th process of forming is performed. The fourth to eighth steps will be described in detail below.

  First, the 4th process of apply | coating the resist 32 on the high refractive index layer 225 is performed (FIG.5 (d)).

  Next, a fifth step of performing exposure and development is performed so as to leave the resist 32 in a region where no lens is formed (FIG. 5E).

  Next, a sixth step of shaping the remaining resist 32 into a lens by heating is performed (FIG. 5F).

  Next, the lens-shaped resist 32 and the high refractive index layer 225 are uniformly etched to perform a seventh step of forming an in-layer lens by the high refractive index layer 225 (FIG. 5G).

  Finally, an eighth step of forming the interlayer film 31 on the light shielding film 19 is performed (FIG. 5H).

  As described above, by performing the fourth to seventh steps of forming the inner lens using the high refractive index layer 225, the special film forming step necessary for the conventional inner lens is deleted, Since steps for manufacturing the solid-state imaging device can be reduced, a low-cost solid-state imaging device can be provided. In addition, since the inner lens is located immediately before the light shielding film 19, even when the width of the opening 20 is small, light can be efficiently collected and high sensitivity can be realized.

(Embodiment 3)
FIG. 6 is a cross-sectional view of the light receiving cells 311a, 311b, and 311c of the solid-state imaging device according to Embodiment 3 of the present invention.

  The solid-state imaging device of the third embodiment differs from the solid-state imaging device of the first embodiment in that the insulating layer 13, the metal layer 114, and the microlens 23 have the same refractive index. For example, by using one material, the insulating layer 13, the metal layer 114, and the microlens 23 are configured to have the same refractive index. As a result, the manufacturing cost can be suppressed.

  Although the solid-state imaging device of the present invention has been described based on the embodiment, the present invention is not limited to this embodiment. The present invention includes various modifications made by those skilled in the art without departing from the scope of the present invention.

  For example, you may comprise a camera using the solid-state imaging device of the said embodiment.

  The present invention can be used for a solid-state imaging device or the like, and in particular, can be used for a solid-state imaging device used for a digital camera, a digital video camera, or the like.

It is sectional drawing of the light reception cells 111a, 111b, 111c of the solid-state imaging device of Embodiment 1 of this invention. FIG. 6 is a diagram illustrating transmission characteristics of the color filter layer 15 and the opening 20. It is sectional drawing which shows the formation method of the structure on the light shielding film 19 in the light reception cell 111a, 111b, 111c of the solid-state imaging device of Embodiment 1 of this invention. It is sectional drawing of the light reception cell 211a, 211b, 211c of the solid-state imaging device of Embodiment 2 of this invention. It is sectional drawing which shows the formation method of the structure on the light shielding film 19 in the light reception cell 211a, 211b, 211c of the solid-state imaging device of Embodiment 2 of this invention. It is sectional drawing of the light reception cells 311a, 311b, 311c of the solid-state imaging device of Embodiment 3 of this invention. It is sectional drawing of the light reception cell 1a, 1b, 1c of the conventional solid-state imaging device.

Explanation of symbols

1a, 1b, 1c, 111a, 111b, 111c, 211a, 211b, 211c, 311a, 311b, 311c Photosensitive cell 11 Semiconductor substrate 12 Photoelectric conversion layer 13 Insulating layer 14, 114, 214 Metal layer 15 Color filter layer 16 P-type well 17 Photoelectric conversion portion 18, 22, 29, 31 Interlayer film 19 Light shielding film 20 Opening portion 21a, 21b, 21c Filter film 23 Micro lens 24 Incident light 125, 225 High refractive index layer 27 Opening thickness 28 High refractive index material Thickness 30 Inner lens 32 Resist

Claims (13)

A semiconductor substrate;
A photoelectric conversion part formed on the semiconductor substrate;
An opening formed so as to be positioned above the photoelectric conversion unit, a light shielding film installed on the semiconductor substrate;
A high refractive index layer formed in the opening,
The opening has an opening width smaller than the maximum wavelength converted to a wavelength in vacuum of light incident on the photoelectric conversion unit through the opening,
The high-refractive index layer is made of a high-refractive index material having a refractive index that transmits light having the maximum wavelength of light incident on the photoelectric conversion unit through the opening. . The solid-state imaging device according to claim 1, wherein the opening is filled with the high refractive index layer. The solid-state imaging device according to claim 1, wherein the high refractive index layer is made of a high refractive index material having a refractive index of 1.8 or more. 4. The solid-state imaging device according to claim 1, wherein a thickness of the high refractive index layer is substantially the same as a thickness of the light shielding film or thicker than a thickness of the light shielding film. The solid-state imaging device according to any one of claims 1 to 4, wherein the high refractive index layer has a convex lens shape and collects light incident on the photoelectric conversion unit through the opening. The solid-state imaging device according to any one of claims 1 to 5, wherein the high refractive index material is any one of titanium oxide, tantalum oxide, and niobium oxide. The solid-state imaging device according to claim 1, wherein the opening width is 1.0 μm or less. The solid-state imaging device further includes a filter film that is installed on the light-shielding film so as to be located above the opening, and that transmits light in a specific wavelength range,
The solid-state imaging device according to claim 1, wherein the opening has an opening width smaller than the maximum wavelength of light transmitted by the filter film. A camera comprising the solid-state imaging device according to claim 1. An opening forming step of forming a light shielding film on the semiconductor substrate on which the photoelectric conversion portion is formed, and forming an opening located above the photoelectric conversion portion in the light shielding film;
A high refractive index layer forming step of forming a high refractive index layer in the opening and on the light shielding film,
In the high refractive index layer forming step, the high refractive index layer having a thickness that makes the surface of the high refractive index layer flat is formed. The method for manufacturing a solid-state imaging device according to claim 10, wherein, in the high refractive index layer forming step, the high refractive index layer having a film thickness equal to or greater than ½ of the width of the opening is formed. The method for manufacturing a solid-state imaging device according to claim 10 or 11, further comprising a flattening step of flattening a surface of the high refractive index layer. The method for manufacturing the solid-state imaging device further includes a lens forming step of processing the high refractive index layer located above the opening into a convex lens shape. The manufacturing method of the solid-state imaging device of description.

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