JP2012019113A - Solid-state imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid state imaging device with high color reproducibility and high sensitivity.SOLUTION: A solid-state imaging device including a plurality of pixels 111R, 111G, 111B, and 111IR comprises a color separation filter 104 which transmits light with predetermined wavelengths corresponding to each pixel 111R, 111G, 111B, and 111IR among incident light. The color separation filter 104 is a multilayer film interference filter having a transmission band in the visible region and the near-infrared region, in which first layers 302, 304, 306, and 308 composed of a high refractive index material, third layers 422, 424, 426, 427, 429, and 431, second layers 305 and 309 composed of a low refractive index material, and fourth layers 423, 425, 428, and 430 are alternately stacked. The area of the third layers 422, 424, 426, 427, 429, and 431 is smaller than that of the second layers 305 and 309, and the fourth layers 423, 425, 428, and 430.

Description

  The present invention relates to a solid-state imaging device used for a digital camera or the like, and more particularly to a solid-state imaging device that detects visible light and near-infrared light.

  In recent years, the application range of solid-state imaging devices such as digital cameras and mobile phones has been explosively expanding, and colorization is essential in any field. Thus, a configuration using an organic material such as a pigment or a dye as a material for the color filter has been proposed (see, for example, Patent Document 1).

  FIG. 10 is a graph showing spectral characteristics of pixels in a conventional solid-state imaging device.

  This figure shows a transmission characteristic 901 of a B (blue transmission) filter, a transmission characteristic 902 of a G (green transmission) filter, and a transmission characteristic 903 of an R (red transmission) filter. The solid-state imaging device of Patent Document 1 constitutes an IR (infrared light transmission) filter that transmits only an infrared component (hereinafter referred to as an IR component) in incident light by laminating an R filter and a B filter. is doing.

  Therefore, the solid-state imaging device of Patent Document 1 is output from the R pixel having the R filter, the G pixel having the G filter, and the B pixel having the B filter using the reference signal output from the pixel having the IR filter. High color reproducibility is realized by performing color signal processing that removes the influence of the IR component included in the pixel signal.

  As another color filter configuration, a color filter configuration using a dielectric multilayer film has also been proposed.

JP 2006-237737 A

  However, when an organic material is used as the material of the color filter, 700 to 850 nm which is an infrared region (IR region) of the transmission characteristics 901 of the B filter, the transmission characteristics 902 of the G filter, and the transmission characteristics 903 of the R filter shown in FIG. There are variations in transmission characteristics. Therefore, the influence of the IR component included in the pixel signal output from the RGB pixel cannot be removed uniformly. That is, the IR component cannot be removed from the pixel signal output from the RGB pixel, or the IR component is excessively differentiated.

  As a result, a color misregistration that deviates from the emission color of the RGB pixel that should be visually recognized occurs. That is, there is a problem that color reproducibility is poor.

  On the other hand, when a dielectric multilayer film is used as the color filter, there is a problem that the sensitivity is lowered due to an increase in the thickness of the color filter.

  In view of the above problems, an object of the present invention is to provide a solid-state imaging device having high color reproducibility and sensitivity.

  In order to solve the above-described problems, a solid-state imaging device according to the present invention is a solid-state imaging device having a plurality of pixels arranged in a two-dimensional shape, and emits light having a predetermined wavelength corresponding to each pixel in incident light. A color separation filter that transmits, the color separation filter in a visible region and a near infrared region in which a high refractive index layer and a low refractive index layer having a lower refractive index than the high refractive index layer are alternately stacked. In the multilayer interference filter having a transmission band, the area of at least one high refractive index layer of the plurality of high refractive index layers is smaller than the area of the plurality of low refractive index layers.

  Thereby, the incident light is collected by the diffraction effect of the light due to the refractive index difference between the high refractive index layer and the low refractive index layer of the color separation filter. Therefore, even when a thick color filter is used, it is possible to suppress a decrease in sensitivity. As a result, high color reproducibility and sensitivity can be realized.

  Each of the at least one high refractive index layer may be surrounded by at least one of the plurality of low refractive index layers.

  As a result, a light diffraction effect is strongly generated, so that the light collection efficiency is further improved.

  The at least one high refractive index layer may be disposed at the center of each pixel.

  Thereby, the influence by the light which does not respond | correspond to each pixel can be reduced. That is, color mixing can be prevented.

  The at least one high refractive index layer may be formed of a plurality of high refractive index layers formed at different positions in the stacking direction and having different areas.

  In addition, the areas of the plurality of high refractive index layers formed at different positions in the stacking direction and having different areas are such that one high refractive index layer located on the light incident surface side faces the light incident surface. You may reduce toward another high refractive index layer located in the surface side.

  Thereby, the light collection efficiency is further improved.

  Further, the substrate includes a substrate having a plurality of light receiving portions corresponding to the plurality of pixels, which is provided on a surface facing the light incident surface of the color separation filter, and the area of each of the at least one high refractive index layer is S. If the area of each pixel is S1 and the area of each light receiving portion is S2, S2 ≦ S ≦ S1 may be satisfied.

The color separation filter includes a visible / near infrared filter having a transmission band in a visible region and a near-infrared region, and a near-infrared normalizing filter laminated on the visible / near-infrared filter, infrared filter, when the setting wavelength and lambda _1, a plurality of three-layer film including a plurality of first layer is the high refractive index layer having a first optical thickness of lambda _1/4, the plurality of And a second layer that is the low-refractive index layer having the first optical film thickness, and each of the plurality of three-layer films includes two first layers. And a first spacer layer, which is a low refractive index layer for controlling light to be transmitted, formed between the two first layers, and the near-infrared normalization filter includes Substantially transparent in the visible region and the first near-infrared wavelength band in the near-infrared region, and A substantially opaque in a second infrared wavelength band between the visible region first near-infrared wavelength band, when the setting wavelength and lambda _2, the second optical film of lambda _2/4 A plurality of third layers that are the high-refractive-index layer having a thickness and a fourth layer that is the low-refractive-index layer having the second optical film thickness stacked on the third layer. A λ / 4 multilayer film and a second spacer layer that is formed between the plurality of λ / 4 multilayer films and that is the low refractive index layer for controlling transmitted light may be provided.

  Thereby, visible light and near-infrared light in a wide wavelength region can be selectively transmitted.

  According to the present invention, a solid-state imaging device with high color reproducibility and sensitivity can be realized.

1 is a schematic plan view illustrating an example of a configuration of a solid-state imaging device according to an embodiment. It is sectional drawing which shows an example of a structure of the solid-state imaging device which concerns on embodiment. It is a graph which shows the spectral characteristic of the solid-state imaging device concerning an embodiment. It is a graph which shows the spectral characteristic of the near-infrared normalization filter of the solid-state imaging device which concerns on embodiment. It is a figure which shows the condensing pattern by the electromagnetic field simulation result of the solid-state imaging device which concerns on embodiment. It is sectional drawing which shows the structure of the solid-state imaging device concerning the comparative example 1. It is a figure which shows the structure and spectral characteristic of the visible near-infrared filter of a solid-state imaging device which concerns on the comparative example 1, and a near-infrared normalization filter. 6 is a graph showing spectral characteristics of a solid-state imaging device according to Comparative Example 1. It is sectional drawing which shows the structure of the solid-state imaging device concerning the comparative example 2. 10 is a graph showing transmission characteristics of a color separation filter of a solid-state imaging device according to Comparative Example 2. It is a figure which shows an example of the process of the solid-state imaging device which concerns on embodiment. It is a figure which shows an example of the process of the continuation of FIG. 9A. It is a figure which shows an example of the process of the continuation of FIG. 9B. It is a figure which shows an example of the process of the continuation of FIG. 9C. It is a figure which shows an example of the process of the continuation of FIG. 9D. It is a figure which shows an example of the process of the continuation of FIG. 9E. It is a graph which shows the spectral characteristic of the pixel in the conventional solid-state image sensor.

  Embodiments according to the present invention will be specifically described below with reference to the drawings.

  FIG. 1 is a schematic plan view showing an example of the configuration of a solid-state imaging device according to an embodiment of the present invention.

  The solid-state imaging device 100 shown in the figure eliminates an infrared cut filter and includes incident light in addition to pixels in which color filters that transmit light components of R (red), G (green), and B (blue) are arranged. An infrared light filter (IR filter) that transmits only the IR (near-infrared) component therein is disposed, and has a pixel that detects only the IR component.

  As a specific configuration, the solid-state imaging device 100 illustrated in FIG. 1 is, for example, a CCD (Charge Coupled Device) image sensor including an imaging unit 110, a storage unit 120, a horizontal transfer unit 130, and an output unit 140.

  The imaging unit 110 generates signal charges by photoelectrically converting incident light. The imaging unit 110 includes two-dimensionally arranged R (red light reception) pixels 111R, G (green light reception) pixels 111G, B (blue light reception) pixels 111B, and IR (infrared light reception) pixels 111IR. Hereinafter, the R pixel 111R, the G pixel 111G, the B pixel 111B, and the IR pixel 111IR may be referred to as pixels 111R, 111G, 111B, and 111IR, respectively. The imaging unit 110 has an array in which the pixels 111R arranged in a staggered pattern among the pixels 111R in the Bayer array are replaced with the pixels 111IR.

  The accumulation unit 120 selectively performs one of accumulation of signal charges generated by the imaging unit 110 and transfer to the horizontal transfer unit 130.

  The horizontal transfer unit 130 outputs the signal charge transferred from the storage unit 120 to the output unit 140 by transferring the signal charge in the horizontal direction.

  The output unit 140 converts the signal charge transferred from the horizontal transfer unit 130 into a voltage signal and outputs the voltage signal.

  Thus, the voltage signal output from the output unit 140 includes a red signal corresponding to the light received by the R pixel 111R, a green signal corresponding to the light received by the G pixel 111G, and a light received by the B pixel 111B. And a blue signal corresponding to the IR signal and an infrared signal corresponding to the light received by the IR pixel 111IR.

  In the solid-state imaging device 100 configured as described above, the infrared signal corresponding to the light received by the IR pixel 111IR is the light received by each light receiving pixel (R pixel 111R, G pixel 111G, B pixel 111B). As a reference signal that gives information on the amount of signal generated due to the IR component in the red signal, green signal, and blue signal according to the influence of the IR component included in each color signal (red signal, green signal, blue signal) Color signal processing to be removed can be performed. For example, by subtracting the reference signal from each of the red signal, the green signal, and the blue signal, the influence of the IR component included in the red signal, the green signal, and the blue signal can be eliminated. As a result, high color reproducibility can be realized.

  Next, a detailed configuration of the imaging unit 110 will be described.

  FIG. 2 is a cross-sectional view showing an example of the configuration of the solid-state imaging device 100 according to the present embodiment. Specifically, it is a diagram showing a cross-sectional configuration of the imaging unit 110, and for the sake of explanation, the configurations of a B pixel 111B, an R pixel 111R, a G pixel 111G, and an IR pixel 111IR are shown from the left in the drawing.

  The solid-state imaging device 100 shown in the figure includes a color separation filter that transmits light of a predetermined wavelength corresponding to the R pixel 111R, the G pixel 111G, the B pixel 111B, and the IR pixel 111IR among the incident light. This is a multilayer interference filter with a transmission band in the visible region and near infrared region, in which a high refractive index layer and a low refractive index layer having a refractive index lower than that of the high refractive index layer are alternately laminated. At least one high refractive index layer area of the refractive index layer is smaller than a plurality of low refractive index layer areas.

  Thereby, in the solid-state imaging device 100 according to the present embodiment, incident light is collected by the diffraction effect of light due to the refractive index difference between the high refractive index layer and the low refractive index layer of the color separation filter. Therefore, even when a thick color filter is used, it is possible to suppress a decrease in sensitivity. As a result, high color reproducibility and sensitivity can be realized.

  Hereinafter, a specific configuration will be described with reference to FIG.

  As shown in FIG. 2, in the solid-state imaging device 100, a P-type semiconductor layer 102, an interlayer insulating film 103, a color separation filter 104, and a condenser lens (also referred to as a microlens) 105 are sequentially stacked on an N-type semiconductor layer 101. Has been. Note that a photodiode 106 in which an N-type impurity is ion-implanted is formed for each pixel on the P-type semiconductor layer 102 side of the interlayer insulating film 103. A P-type semiconductor layer is interposed between adjacent photodiodes 106, and this is called an element isolation region. Here, the color separation filter 104 is a multilayer interference filter that transmits visible light and near infrared light, and a visible near infrared filter 104a that is a multilayer interference filter that separates incident light into R, G, B, and IR light. The filter has a configuration in which a near-infrared normalization filter 104b that is a filter is stacked.

  A light shielding film 107 is formed in the interlayer insulating film 103. The individual photodiodes 106 and the condensing lens 105 have a corresponding relationship, and the light shielding film 107 prevents the light transmitted through the condensing lens 105 from entering the photodiode 106 that has no corresponding relationship.

  Note that the N-type semiconductor layer 101 and the P-type semiconductor layer 102 correspond to the substrate of the present invention, and the photodiode 106 corresponds to the light receiving portion of the present invention.

[Visible near infrared filter]
Here, a specific configuration of the visible near-infrared filter 104a and the near-infrared normalization filter 104b will be described.

  First, the configuration of the visible / near infrared filter 104a will be described.

When the set wavelength is λ ₁ (for example, 530 [nm]), the visible near-infrared filter 104a has an optical film thickness substantially equal to ¼ of the set wavelength λ ₁ and is made of a high refractive index material. One set of λ / 4 multilayer films formed of a second type material having a different refractive index composed of one layer and a second layer made of a low refractive index material. Here, the optical film thickness is a value obtained by multiplying the physical film thickness by the refractive index, and the set wavelength λ ₁ is the peak wavelength of the transmission band in the visible region of the visible near-infrared filter 104a.

Specifically, the visible / near infrared filter 104a includes a λ / 4 multilayer film in which a first layer 304, a second layer 305, and a first layer 306 are stacked in this order, and λ / 4. sandwiching the multilayer film has a first spacer layer (also referred to as a "defect layer" or "resonant layer") 303 and 307, further, the first layer 302 and 308 and its structure is the lambda _1/4 film It has a structure sandwiched between. In other words, the first spacer layers 303 and 307 are formed between the first layers 302 and 304 and the first layers 306 and 308, respectively. That is, the visible and near infrared filter 104a includes a three-layer film including a first layer 306, a first spacer layer 307, and a first layer 308, a first layer 302, a first spacer layer 303, A three-layer film composed of the first layer 304, and a second layer 305 formed between the two three-layer films. In addition, a second layer 309 for planarizing the light incident surface is provided over the first layer 308.

The first layers 302, 304, 306, and 308 have the same film thickness in any of the R pixel 111R, the G pixel 111G, the B pixel 111B, and the IR pixel 111IR, and have high refraction made of, for example, titanium dioxide (TiO ₂ ). Consists of rate material.

The second layer 305 has the same film thickness in any of the R pixel 111R, the G pixel 111G, the B pixel 111B, and the IR pixel 111IR, and is made of, for example, a low refractive index material made of silicon dioxide (SiO ₂ ). Yes.

Here, setting the wavelength lambda ₁ that determines the thickness of lambda _1/4 film can be 530 nm, the respective optical thickness of three layers consisting of first and second layers becomes 132.5 nm. Since the refractive index of titanium dioxide at a wavelength of 530 nm is 2.53 and the refractive index of silicon dioxide is 1.48, the physical thickness of the first layers 304 and 306 made of titanium dioxide is 52 nm, and the second film made of silicon dioxide. The physical film thickness of the layer 305 is 91 nm. In other words, the first layers 304 and 306 made of high refractive index material made of titanium dioxide having a physical thickness of 52 nm and the second layer 305 made of silicon dioxide having a physical thickness of 91 nm and made of silicon dioxide having a physical thickness of 91 nm form a set of λ. / 4 multilayer film is formed.

  Then, on the N-type semiconductor layer 101 and P-type semiconductor layer 102 side of the λ / 4 multilayer film, a first spacer layer made of a low refractive index material having a different optical film thickness for each of the pixels 111R, 111G, 111B, and 111IR. On the other hand, a first spacer layer 307 made of a low refractive index material having a different optical film thickness for each of the pixels 111R, 111G, 111B, and 111IR is provided on the condenser lens 105 side of the λ / 4 multilayer film. Is formed.

  Here, each of the first spacer layers 303 and 307 has an optical film thickness corresponding to the light transmitted through the pixels 111R, 111G, 111B, and 111IR of the visible / near infrared filter 104a. That is, the first spacer layers 303 and 307 are layers used for controlling light to be transmitted, and transmit R, G, B, and IR light by changing the film thickness.

  Specifically, the film thicknesses of the first spacer layers 303 and 307 are 45 nm for the R pixel 111R, 182 nm for the G pixel 111G, 140 nm for the B pixel 111B, and 91 nm for the IR pixel 111IR.

  The thickness of each of the first layers 302 and 308 is 52 nm.

  The second layer 309 is, for example, a TEOS (Tetra Ethyl Ortho Silicate) planarization film.

  The visible and near infrared filter 104a configured as described above can achieve color separation only by changing the film thickness of the first spacer layers 303 and 307.

[Configuration and transmission characteristics of near-infrared normalized filter]
Next, the configuration of the near infrared normalization filter 104b will be described.

The near-infrared normalization filter 104b has an optical film thickness substantially equal to ¼ of the set wavelength λ ₂ when the set wavelength is λ ₂ (for example, 850 [nm]). Two layers of λ / 4 multilayer films formed of layers of two kinds of materials having different refractive indexes, each including a third layer and a fourth layer made of a low refractive index material. Specifically, in the near-infrared normalization filter 104b, a third layer 422, a fourth layer 423, a third layer 424, a fourth layer 425, and a third layer 426 are stacked in this order. A first set of λ / 4 multilayer films, a third layer 427, a fourth layer 428, a third layer 429, a fourth layer 430, and a third layer 431 are sequentially stacked. / 4 multilayer film. A second spacer layer 433 made of a low refractive index material is formed between the two sets of λ / 4 multilayer films.

Here, the set wavelength λ ₂ is the peak wavelength of the transmission band in the near infrared region of the near infrared normalizing filter 104b.

  Further, in order to improve the transmittance in the short wavelength region, each of the third layer 422 on the N-type semiconductor layer 101 side and the third layer 431 on the condenser lens 105 side has λ / 8 made of a low refractive index material. Films 421 and 432 are formed.

  Here, as shown in FIG. 2, the number of layers of the near-infrared normalization filter 104b in the R pixel 111R, the G pixel 111G, the B pixel 111B, and the IR pixel 111IR is eleven.

Of the two layers of materials having different refractive indexes, the third layers 422, 424, 426, 427, 429 and 431 are specifically high refractive index materials made of titanium dioxide (TiO ₂ ). Specifically, the fourth layers 423, 425, 428, and 430 are made of a low refractive index material made of silicon dioxide (SiO ₂ ). Further, the λ / 8 films 421 and 432 and the second spacer layer are also specifically made of a low refractive index material made of silicon dioxide (SiO ₂ ).

  In addition, the third layers 422, 424, 426, 427, 429, and 431 and the fourth layers 423, 425, 428, and 430 respectively include an R pixel 111R, a G pixel 111G, a B pixel 111B, and an IR. The optical film thickness is the same in any of the pixels 111IR.

Here, since the setting wavelength λ ₂ for determining the film thickness of the λ / 4 film is 850 nm, the third layers 422, 424, 426, 427, 429 and 431 and the fourth layers 423, 425, 428 and 430 are used. The respective optical film thicknesses are 212.5 nm. Since the refractive index of titanium dioxide at a wavelength of 850 nm is 2.41 and the refractive index of silicon dioxide is 1.44, the physical thickness of the third layer made of titanium dioxide is 88 nm, and the physical thickness of the fourth layer. Becomes 148 nm.

  Specifically, a third layer 422, 424 and 426 of a high refractive index material made of titanium dioxide having a physical thickness of 88 nm, and a fourth layer 423 of a low refractive index material made of silicon dioxide having a physical thickness of 148 nm and 425 forms one set of λ / 4 multilayer films. Further, the third layers 427, 429 and 431 of high refractive index material made of titanium dioxide having a physical thickness of 88 nm and the fourth layers 428 and 430 of low refractive index material made of silicon dioxide having a physical thickness of 148 nm are provided. Another set of λ / 4 multilayer films is formed. Further, on each of the third layer 422 on the N-type semiconductor layer 101 side and the third layer 431 on the condenser lens 105 side, a λ / 8 film 421 made of silicon dioxide having a physical thickness of 148 nm and made of silicon dioxide. And 432 are formed. In addition, a second spacer layer 433 made of low refractive index material made of silicon dioxide having a physical thickness of 0 nm is formed between the two sets of λ / 4 multilayer films.

  FIG. 3A is a graph showing the spectral characteristics of the solid-state imaging device 100 according to the present embodiment, and shows the design results calculated using the matrix method. In the graph shown in FIG. 3A, the vertical axis represents the light collection efficiency of the color separation filter 104, and the horizontal axis represents the wavelength of transmitted light.

  FIG. 3B is a graph showing the spectral characteristics of the near-infrared normalization filter 104b of the solid-state imaging device 100 according to the present embodiment. In the graph shown in FIG. 3B, the vertical axis represents the transmittance of the near-infrared normalization filter 104b, and the horizontal axis represents the wavelength of transmitted light.

  As shown in FIG. 3B, the near-infrared normalization filter 104b is substantially in the first near-infrared wavelength band (800-850 nm) in the near-infrared region (700-850 nm) and the visible region. It is transparent. As shown in FIG. 3, the near-infrared normalization filter 104b is not substantially transparent in the second near-infrared wavelength band (700 to 750 nm) in the near-infrared region (700 to 850 nm). That is, it is not substantially transparent between the visible region and the second near infrared wavelength band between the first near infrared wavelength band. Here, “substantially transparent” means that the transmittance for transmitting light is 80% or more, and “not substantially transparent” means that the transmittance is 20% or less.

As described above, the solid-state imaging device 100 includes the color separation filter 104 that transmits light having a predetermined wavelength corresponding to each of the pixels 111R, 111G, 111B, and 111IR in the incident light. A visible near-infrared filter 104a having a transmission band in the near-infrared region and a near-infrared normalizing filter 104b stacked on the visible-near-infrared filter 104a, the visible-near-infrared filter 104a having a set wavelength of λ When _1, a plurality of three-layer film including a plurality of first layers 302, 304, 306 and 308 is a high refractive index layer having a first optical thickness of lambda _1/4, a plurality of three-layer film And a second layer 305 having a first optical film thickness, and each of the plurality of three-layer films is formed between the two first layers and the two first layers. Control the transmitted light The first spacer layers 303 and 307, which are low refractive index layers, and the near-infrared normalization filter 104b is substantially in the visible region and the first near-infrared wavelength band in the near-infrared region. a transparent and substantially opaque in a second infrared wavelength band between the visible region and the first near-infrared wavelength band, when the setting wavelength and lambda _2, lambda _2/4 A third layer 422, 424, 426, 427, 429 and 431 having a second optical film thickness, and a fourth layer 423, 425 having a second optical film thickness stacked on the third layer. A plurality of λ / 4 multilayer films composed of 428 and 430, and a second spacer layer 433 formed between the plurality of λ / 4 multilayer films for controlling the transmitted light.

  The near-infrared normalization filter 104b can selectively transmit visible light and near-infrared light in a wide wavelength region with the above configuration.

  Further, as shown in FIG. 2, the areas of the third layers 422, 424, 426, 427, 429 and 431 made of the high refractive index material of the near-infrared normalization filter 104b are from the light incident surface side. As it goes to the N-type semiconductor layer 101 and the P-type semiconductor layer 102 side, it becomes smaller. The periphery of the third layers 422, 424, 426, 427, 429 and 431 made of a high refractive index material is a fourth layer made of a low refractive index material of the near-infrared normalization filter 104b. Layers 423, 425, 428, and 430 and λ / 8 films 421 and 432 of low refractive index material are formed. With such a configuration, light is collected by the light diffraction effect due to the difference in refractive index between the high refractive index material and the low refractive index material. Therefore, even when a thick color separation filter is used, it is possible to suppress a decrease in sensitivity.

  In other words, each of the third layers 422, 424, 426, 427, 429 and 431 composed of a high refractive index material is composed of a fourth layer 423, 425, 428 composed of a low refractive index material. 430 and λ / 8 films 421 and 432 of a low refractive index material. Thereby, since the diffraction effect is strongly generated, the light collection efficiency is further improved.

  The third layers 422, 424, 426, 427, 429, and 431 are formed at different positions in the stacking direction and have different areas. Furthermore, the areas of the third layers 422, 424, 426, 427, 429 and 431 of the high refractive index materials which are formed at different positions in the stacking direction and have different areas are located on the light incident surface side. It decreases from the one third layer 431 toward the other third layer 422 located on the opposite surface side of the light incident surface. That is, the third layers 422, 424, 426, 427, 429, and 431 have a tapered structure in the stacking direction. Thereby, the light collection efficiency is further improved.

  FIG. 4 shows the result of electromagnetic field simulation by the finite element method, and it can be seen that the above-mentioned taper structure causes the light diffraction effect. Thus, the light is collected on the photodiode 106. In addition, the high refractive index layers shown in the figure are the third layers 422, 424, 426, 427, 429 and 431, and the low refractive index layers are the fourth layers 423, 425, 428 and 430.

(Comparative Example 1)
Hereinafter, the improvement of the light condensing efficiency by a taper structure is demonstrated using the comparative example 1. FIG.

  FIG. 5 is a cross-sectional view illustrating a configuration of the solid-state imaging device according to Comparative Example 1.

  The solid-state imaging device 200 shown in the figure is different from the solid-state imaging device 100 according to the embodiment in that it includes a near-infrared normalization filter 204b instead of the near-infrared normalization filter 104b.

  The near-infrared normalization filter 204b includes a first layer λ in which a third layer 222, a fourth layer 223, a third layer 224, a fourth layer 225, and a third layer 226 are stacked in this order. / 4 multilayer film, a second set of λ / 4 multilayer films in which a third layer 227, a fourth layer 228, a third layer 229, a fourth layer 230, and a third layer 231 are sequentially stacked, Have A second spacer layer 233 made of a low refractive index material is formed between the two sets of λ / 4 multilayer films. Further, in order to improve the transmittance in the short wavelength region, each of the third layer 222 on the N-type semiconductor layer 101 side and the third layer 231 on the condenser lens 105 side has λ / 8 made of a low refractive index material. Films 221 and 232 are formed. The materials and thicknesses of the third layer, the fourth layer, and the λ / 8 film are the same as those in the embodiment.

  The near-infrared normalization filter 204b has a third layer 222, 224, 226, 227, 229 and 231 of a high refractive index material formed in a solid film shape as compared with the near-infrared normalization filter 104b. Is different.

  That is, the solid-state imaging device 200 according to the comparative example 1 is spectrally separated by a laminated configuration of two filters of a visible near-infrared filter 104a and a near-infrared normalization filter 204b as shown in FIGS. 6 (a) and 6 (b). According to the characteristics, the spectral characteristics of 700 nm or more of the color separation filter can be made substantially the same in the R, G, B, and IR pixels as shown in FIG. With such a configuration, high color reproducibility can be obtained without causing a color shift even when illumination with a low color temperature is used. 6C shows the spectral characteristics of the visible near infrared filter 104a, and FIG. 6D shows the spectral characteristics of the near infrared normalization filter 204b.

  However, in this case, in order to realize high color reproducibility, it is necessary to increase the number of dielectric multilayer films, and the film thickness of the color filter becomes thick. 106) and the surface of the solid-state imaging device 200 are increased.

  As a result, the amount of light reaching the light receiving unit (photodiode 106) of the solid-state imaging device 200 is reduced, and sensitivity is reduced. In this case, as shown in FIG. 5, even if the condenser lens 105 is formed on the surface of the solid-state imaging device 200 and the light is collected, the light is diffracted because the distance from the light receiving unit (photodiode 106) is large. The condensed light spreads due to the effect, and the wiring is damaged.

  FIG. 7 is a graph showing the spectral characteristics of the solid-state imaging device 200 according to Comparative Example 1.

  4 is compared with the spectral characteristics of the solid-state imaging device 100 according to the embodiment shown in FIG. 4, the spectral characteristics of the solid-state imaging device 100 according to the embodiment are compared. It is obvious that the characteristics are higher than the spectral characteristics of the solid-state imaging device 200 according to Comparative Example 1.

  That is, in the solid-state imaging device 200 according to Comparative Example 1, even though the light collected by the light diffraction effect spreads and the wiring is distorted, the transmittance of the color separation filter is 100%. Condensation efficiency decreases.

  In other words, in Comparative Example 1, the light collection efficiency was about 60% in the color separation filters of each color, but in the solid-state imaging device 100 according to the present embodiment, the light collection efficiency is about 80%. Compared with Comparative Example 1, the light collection efficiency is improved 1.3 to 1.4 times.

  As described above, in the solid-state imaging device 100 according to the present embodiment, the third layers 422, 424, 426, 427, 429, and 431 are tapered in the stacking direction as compared with the first comparative example. High condensing efficiency can be realized.

(Comparative Example 2)
On the other hand, in order to improve the light collection efficiency, a configuration of a solid-state imaging device using a thin color separation filter can be considered.

  Hereinafter, a solid-state imaging device according to Comparative Example 2 of the embodiment of the present invention will be described with reference to the drawings.

  The solid-state imaging device according to this comparative example is different from the solid-state imaging device 100 according to the present embodiment in that the color separation filter is thinly formed. Specifically, the solid-state imaging device according to this comparative example does not include a near-infrared normalization filter.

  FIG. 8A is a diagram illustrating a cross-sectional configuration of a solid-state imaging device according to Comparative Example 2 in which a dielectric multilayer film 510 is used as a color separation filter (color filter), and FIG. 8B is a color separation filter illustrated in FIG. 8A. It is a graph which shows the transmission characteristic of (color filter).

  As shown in FIG. 8B, the color separation filter (color filter) of the solid-state imaging device according to Comparative Example 2 can also perform R, G, B, and (IR) color separation.

  However, when the signal output from the RGB pixel is differentiated from the reference signal of the IR pixel, as shown in FIG. 8B, the RGB spectral characteristics of each pixel vary from 700 nm to 850 nm. In particular, color shift occurs especially for low color temperature illumination.

  On the other hand, since the solid-state imaging device 100 according to the present embodiment has a small variation in the RGB spectral characteristics of 700 nm to 850 nm, the color shift can be reduced. In other words, high color reproducibility can be realized.

  Further, the solid-state imaging device 100 according to the present embodiment has a condensing effect due to the refractive index difference between the high refractive index material and the low refractive index material of the color separation filter, even when a thick color filter is used. It is possible to suppress a decrease in sensitivity.

  Next, a method for manufacturing the solid-state imaging device 100 according to the present embodiment having the above-described configuration will be described.

  9A to 9F are diagrams illustrating an example of a method for manufacturing the solid-state imaging device 100 according to the present embodiment. Here, only the points different from the conventional one are described, and the same steps as the conventional one are omitted.

  First, as shown in FIG. 9A, after forming the P-type semiconductor layer 102, the photodiode 106, the interlayer insulating film 103, and the light-shielding film 107 on the N-type semiconductor layer 101, the low refraction of the near-infrared normalization filter 104b is reduced. The rate layer is formed by a film forming method used in a normal semiconductor process such as CVD or sputtering (for example, silicon dioxide). Specifically, a λ / 8 film 421 made of a low refractive index material for the near infrared normalization filter 104b is formed.

  Thereafter, as shown in FIG. 9B, a high refractive index layer of the near-infrared normalizing filter 104b is formed by a film forming method used in a normal semiconductor process such as CVD or sputtering (for example, titanium dioxide). In other words, the high refractive index layer 422a made of a high refractive index material is formed.

  Thereafter, as shown in FIG. 9C, a resist 610 is patterned on the high refractive index layer 422a by lithography.

  Thereafter, as shown in FIG. 9D, the third layer 422 made of a high refractive index material is formed by patterning the high refractive index layer 422a using wet etching or dry etching.

  Thereafter, as shown in FIG. 9E, a desired pattern can be obtained by removing the resist 610.

  Thereafter, as shown in FIG. 9F, the film is formed by a film forming method used in a normal semiconductor process such as CVD or sputtering.

  Thereafter, the near-infrared normalization filter 104b is formed by repeating the above process. Note that the visible and near infrared filter 104a can be realized by performing the same process.

  Through the above steps, the solid-state imaging device 100 according to the present embodiment can be manufactured.

  In the present embodiment, all of the third layers 422, 424, 426, 427, 429 and 431 made of the high refractive index material of the near-infrared normalization filter 104b are patterned by the above process. The number of layers is not limited.

  As described above with reference to the drawings, the solid-state imaging device 100 according to the embodiment of the present invention includes a plurality of pixels (R pixel 111R, G pixel 111G, B pixel 111B, and IR pixel arranged in a two-dimensional manner. 111IR), and includes a color separation filter 104 that transmits light having a predetermined wavelength corresponding to each of the pixels 111R, 111G, 111B, and 111IR in incident light, and the color separation filter 104 has a high refractive index. First layers 302, 304, 306 and 308 made of a material, third layers 422, 424, 426, 427, 429 and 431, and a second made of a low refractive index material having a refractive index lower than that of a high refractive index material. Multilayer interference having layers 305 and 309 and fourth layers 423, 425, 428, and 430 alternately stacked and having a transmission band in the visible region and the near infrared region A filter, the area of the third layer 422,424,426,427,429 and 431 is smaller than the area of the second layer 305 and 309 and the fourth layer 423,425,428 and 430.

  Thus, in the solid-state imaging device according to the embodiment of the present invention, light is collected by the light diffraction effect due to the refractive index difference between the high refractive index material and the low refractive index material of the color separation filter 104. Therefore, even when a thick color filter is used, it is possible to suppress a decrease in sensitivity.

  Preferably, the area of each of the third layers 422, 424, 426, 427, 429, and 431 is smaller than the area of the fourth layer adjacent to the third layer.

  Note that each of the first layers 302, 304, 306, and 308 and the third layers 422, 424, 426, 427, 429, and 431 is the high refractive index layer of the present invention, and the second layer 305 and Each of 309 and the fourth layers 423, 425, 428, and 430 is the low refractive index layer of the present invention.

  In addition, third layers 422, 424, 426, 427, 429, and 431 are arranged at the center of each pixel (R pixel 111R, G pixel 111G, B pixel 111B, and IR pixel 111IR).

  Thereby, the influence by the light which does not respond | correspond to each pixel (R pixel 111R, G pixel 111G, B pixel 111B, and IR pixel 111IR) can be reduced. That is, color mixing can be prevented.

  Furthermore, a plurality of photodiodes 106 corresponding to a plurality of pixels (R pixel 111R, G pixel 111G, B pixel 111B, and IR pixel 111IR) provided on the surface opposite to the light incident surface of the color separation filter 104 are provided. The third layer 422, 424, 426, 427, 429, and 431 has an area S, and the area of each pixel (R pixel 111R, G pixel 111G, B pixel 111B, and IR pixel 111IR) is provided. S1, When the area of each photodiode 106 is S2, S2 ≦ S ≦ S1 is satisfied.

  As described above, the solid-state imaging device according to the present invention has been described based on the embodiment. However, the present invention is not limited to this embodiment. Unless it deviates from the meaning of this invention, the form which carried out the various deformation | transformation which those skilled in the art can think to the said embodiment, and the form constructed | assembled combining the component in a different embodiment is also contained in the scope of the present invention. .

For example, in the above embodiment, the case where titanium dioxide is used as the high refractive index material has been described. Needless to say, the present invention is not limited to this, and the following may be used instead. That is, other materials such as silicon nitride (Si ₃ N ₄ ), tantalum trioxide (Ta ₂ O ₃ ), and zirconium dioxide (ZrO ₂ ) may be used as the high refractive index material instead of titanium dioxide. . Moreover, you may use materials other than silicon dioxide also about a low refractive index material. The effects of the present invention can be obtained regardless of the material used for the multilayer interference filter.

  In the above-described embodiment, the case where silicon dioxide is used as the material for the first and second spacer layers has been described. It may be used. As the material of the first and second spacer layers, the same material as either the high refractive index layer or the low refractive index layer constituting the dielectric layer may be used, or a different material may be used. Further, as described above, different materials may be used for the two defect layers.

  In the above embodiment, the solid-state imaging device 100 is a CCD image sensor. However, a MOS (Metal Oxide Semiconductor) image sensor may be used.

  The solid-state imaging device according to the present invention can be used for imaging devices such as digital cameras and digital video cameras.

100, 200 Solid-state imaging device 101 N-type semiconductor layer 102 P-type semiconductor layer 103 Interlayer insulating film 104 Color separation filter 104a Visible and near-infrared filter 104b and 204b Near-infrared normalization filter 105 Condensing lens 106 Photodiode 107 Light-shielding film 110 Imaging unit 111B B pixel (pixel)
111G G pixel (pixel)
111IR IR pixel (pixel)
111R R pixel (pixel)
120 Storage unit 130 Horizontal transfer unit 140 Output unit 221, 232, 421, 432 λ / 8 film 222, 224, 226, 227, 229, 231, 422, 424, 426, 427, 429, 431 Third layer 223, 225, 228, 230, 423, 425, 428, 430 Fourth layer 233, 433 Second spacer layer 302, 304, 306, 308 First layer 303, 307 First spacer layer 305, 309 Second Layer 422a High refractive index layer 510 Dielectric multilayer 610 Resist 901 Transmission characteristics of B filter 902 Transmission characteristics of G filter 903 Transmission characteristics of R filter

Claims (7)

A solid-state imaging device having a plurality of pixels arranged two-dimensionally,
A color separation filter that transmits light of a predetermined wavelength corresponding to each pixel of incident light;
The color separation filter includes a multilayer interference filter having a transmission band in a visible region and a near infrared region, in which a high refractive index layer and a low refractive index layer having a lower refractive index than the high refractive index layer are alternately laminated. And
An area of at least one high refractive index layer of the plurality of high refractive index layers is smaller than an area of the plurality of low refractive index layers. The solid-state imaging device according to claim 1, wherein each of the at least one high refractive index layer is surrounded by at least one of the plurality of low refractive index layers. The solid-state imaging device according to claim 1, wherein the at least one high refractive index layer is disposed at the center of each pixel. The solid-state imaging according to any one of claims 1 to 3, wherein the at least one high refractive index layer includes a plurality of high refractive index layers that are formed at different positions in the stacking direction and have different areas. apparatus. The areas of the plurality of high refractive index layers which are formed at different positions in the stacking direction and have different areas are from one high refractive index layer located on the light incident surface side to the opposite surface side of the light incident surface. The solid-state imaging device according to claim 4, wherein the solid-state imaging device decreases toward another high-refractive-index layer positioned at the position. Furthermore, provided with a substrate having a plurality of light receiving portions corresponding to the plurality of pixels, provided on the opposite surface side of the light incident surface of the color separation filter,
The area of each said at least 1 high refractive index layer is set to S, the area of each pixel is set to S1, and the area of each light-receiving part is set to S2, S2 <= S <= S1 is satisfy | filled. Solid-state imaging device. The color separation filter is
A visible near infrared filter having a transmission band in the visible region and the near infrared region; and
A near-infrared normalization filter laminated on the visible near-infrared filter,
The visible near-infrared filter has a set wavelength λ ₁ ,
a plurality of three-layer film including a plurality of first layer is the high refractive index layer having a first optical thickness of lambda _1/4,
A second layer which is formed between the plurality of three-layer films and is the low refractive index layer having the first optical film thickness;
Each of the plurality of three-layer films is a first low-refractive index layer formed between two first layers and two first layers for controlling light to be transmitted. A spacer layer of
The near infrared normalization filter is:
Substantially transparent in the visible region and a first near-infrared wavelength band in the near-infrared region, and a second between the visible region and the first near-infrared wavelength band Substantially opaque in the near-infrared wavelength band,
If the set wavelength is λ ₂ ,
the third layer and the low refractive index layer having a third of said second optical film thickness that is laminated to a layer in which said high refractive index layer having a second optical thickness of lambda _2/4 A plurality of λ / 4 multilayer films composed of a fourth layer;
The second spacer layer, which is the low refractive index layer for controlling light to be transmitted, formed between the plurality of λ / 4 multilayer films. Solid-state imaging device.