Patent Publication Number: US-2009225204-A1

Title: Solid state imaging device and camera

Description:
TECHNICAL FIELD 
     The present invention relates to a solid-state imaging device and a camera, and particularly to an art for shielding infrared light included in incident light. 
     BACKGROUND ART 
     In recent years, the range of applications for solid-state imaging devices such as digital cameras and mobile phones has been expanding explosively. This increases a demand for solid-state imaging devices capable of imaging using invisible light such as infrared light and ultraviolet light in addition to color-imaging using visible light. 
       FIG. 1  is a cross-sectional view showing the structure of a solid-state imaging device according to a conventional art (see Patent Document 1, for example). As shown in  FIG. 1 , a solid-state imaging device  8  is composed of planarizing layers  804  and  805  and an invisible light cut filter  806  that are sequentially laminated on a silicon substrate  801 . 
     The invisible light cut filter  806  is a multilayer film that is composed of alternately laminated dielectric layers and metal layers. Also, photodiodes  802  and CCDs (Charge Coupled Devices)  803  are formed in one surface of a silicon substrate  801  that is closer to the planarizing layer  804 . 
     A red filter  807  for transmitting red light and invisible light is formed inside the planarizing layer  804 . Color separation filters  808  are formed inside the planarizing layer  805 . 
     The photodiodes  802  have sensitivity to infrared regions. Accordingly, the cutoff of invisible light by the invisible light cut filter  806  can prevent signal charges from being generated due to infrared light. Therefore, it is possible to perform imaging using visible light with high accuracy. 
     Incident light that has penetrated through the color separation filter  808  without penetrating through the invisible light cut filter  806  includes only blue light and invisible light. If this incident light further penetrates through the red filter  807 , the blue light is cut off. Accordingly, only the invisible light enters the photodiodes  802 . This realizes imaging using invisible light. 
     With the above structure, it is possible to realize a solid-state imaging device capable of imaging using infrared light in addition to color-imaging using visible light. 
     Patent Document 1: Japanese Patent No. 3078458 
     Patent Document 2: International Patent Publication No. WO 2005/069376 A1 
     DISCLOSURE OF THE INVENTION 
     Problems the Invention is Going to Solve 
     However, a film thickness of the planarizing layer  804  excluding the red filter  807  and a film thickness of the planarizing layer  805  excluding the color separation filters  808  are each substantially 3 μm. Accordingly, a total film thickness of the filters is as much as 6 μm or more. 
     In such a case, if the pixel size is 2 μm or less, light obliquely entering the color separation filters  808  (hereinafter referred to as “oblique light”) further enters the photodiodes  802  other than the photodiodes  802  respectively corresponding to the color separation filters  808 . This causes problems such as deterioration in the color separation function, increase of noises, and deterioration in the wavelength sensitivity. 
     Furthermore, there is a problem that complicated manufacturing processes lead to high manufacturing cost. 
     The present invention is made to solve the above-described problems. An object of the present invention is to provide a solid-state imaging device that is capable of shielding infrared light and having a high wavelength separation function and can be manufactured at low cost, and a camera including such a solid-state imaging device. 
     Means to Solve the Problems 
     In order to achieve the above object, the present invention provides a solid-state imaging device that performs color-imaging using visible light, the solid-state imaging device comprising two-dimensionally arrayed pixels each including: a visible light filter that is composed of a multilayer interference filter that mainly transmits visible light having a wavelength within a predetermined wavelength range; and an infrared filter that is composed of a plurality of λ/4 multilayer films each having a different set-wavelength λ and that reflects infrared light, wherein the visible light filter and the infrared filter are layered in contact with each other. 
     EFFECT OF THE INVENTION 
     With this structure, an infrared filter can be structured without metal layers, unlike the conventional art according to the Patent Document 1. Accordingly, it is possible to downsize the solid-state imaging device by reducing a thickness thereof. Also, it is possible to realize a high wavelength separation function by preventing oblique light. 
     Note that a color filter using a multilayer interference filter has a color separation function in visible regions, as described in the Patent Document 2. However, this color filter cannot shield infrared light of 700 nm to 1000 nm. Therefore, an optical filter for shielding infrared light is required. On the other hand, according to the present invention, a plurality of laminated λ/4 multilayer films can shield infrared light without using an optical filter. 
     Note that “to mainly transmit visible light having a wavelength within a predetermined wavelength range” means that it is possible to transmit invisible light in addition to visible light having a wavelength within a predetermined wavelength range when a multilayer interference filter is used as a color filter. 
     The solid-state imaging device according to the present invention is characterized in that the infrared filter is composed of dielectric materials. With this structure, an infrared filter can be formed without planarizing layers, unlike the conventional art according to the Patent Document 1. Accordingly, it is possible to downsize the solid-state imaging device. Also, it is possible to reduce manufacturing cost by reducing the number of steps required in the manufacturing processes of the solid-state imaging device. 
     The solid-state imaging device according to the present invention is characterized in that the infrared filter is composed of same dielectric materials used as materials of the visible light filter. With this structure, an infrared filter can be formed without metal materials, unlike the conventional art according to the Patent Document 1. Accordingly, it is possible to manufacture the solid-state imaging device using fewer kinds of materials. This can reduce manufacturing cost of the solid-state imaging device. 
     In this case, the dielectric materials may include titanium dioxide as a higher refractive index material and silicon dioxide as a lower refractive index material. With this structure, it is possible to achieve a high wavelength separation capability by increasing a difference in refractive index between the high refractive index material and the low refractive index material of the λ/4 multilayer films. 
     The solid-state imaging device according to the present invention is characterized in that the visible light filter is layered on the infrared filter. 
     With this structure, it is possible to downsize the solid-state imaging device and reduce manufacturing cost of the solid-state imaging device. 
     Specifically, it is preferable that the multilayer interference filter includes λ/4 multilayer films each having a set-wavelength λ within a visible wavelength range, and the infrared filter is composed of the λ/4 multilayer films each having the set-wavelength λ within an infrared wavelength range. When the set-wavelength of each of the λ/4 multilayer films that constitute the infrared filter is within a range of 700 nm to 1000 nm inclusive, it is possible to realize an excellent wavelength separation capability. In this case, it is preferable that the multilayer interference filter is composed of two λ/4 multilayer films with a dielectric layer sandwiched therebetween. 
     A camera according to the present invention is a camera having a solid-state imaging device that performs color-imaging using visible light, the solid-state imaging device comprising two-dimensionally arrayed pixels each including: a visible light filter that is composed of a multilayer interference filter that mainly transmits visible light having a wavelength within a predetermined wavelength range; and an infrared filter that is composed of a plurality of λ/4 multilayer films each having a different set-wavelength λ and reflects infrared light, wherein the visible light filter and the infrared filter are layered in contact with each other. With this structure, it is possible to achieve ahigh wavelength separation capability by eliminating an influence of infrared light in performing color-imaging using visible light. Also, it is possible to reduce manufacturing cost of the camera. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view showing the structure of a solid-state imaging device according to a conventional art; 
         FIG. 2  is a cross-sectional view showing the main structure of a digital camera according to an embodiment of the present invention; 
         FIG. 3  is a cross-sectional view showing the main structure of a solid-state imaging element  101  according to the embodiment of the present invention; 
         FIG. 4  is a cross-sectional view showing the structure of a wavelength separation filter  206  according to the embodiment of the present invention; 
         FIGS. 5A and 5B  are graphs showing transmissivity characteristics of the wavelength separation filter  206  according to the embodiment of the present invention, where  FIG. 5A  shows transmissivity characteristics of the whole of the wavelength separation filter  206 , and  FIG. 5B  shows transmissivity characteristics of a multilayer interference filter  301 ; 
         FIG. 6  shows manufacturing processes of the wavelength separation filter  206 ; 
         FIGS. 7A to 7C  are graphs showing relations between the number of layers of λ/4 multilayer films  302  to  304  and characteristics of wavelength separation, where  FIG. 7A  shows a relation in a case where x and y are 2 (11 layers in total),  FIG. 7B  shows a relation in a case where x and y are 4 (19 layers in total), and  FIG. 7C  shows a relation in a case where x and y are 6 (27 layers in total); and 
         FIG. 8  is a cross-sectional view showing the structure of a wavelength separation filter according to a modification (3) of the present invention. 
     
    
    
     DESCRIPTION OF CHARACTERS 
     
         
         
           
               1 : digital camera 
               8 : solid-state imaging device according to a conventional art 
               7  and  206 : wavelength separation filter 
               101 : solid-state imaging element 
               102 : imaging lens 
               103 : cover glass 
               104 : gear 
               105 : optical finder 
               106 : zoom motor 
               107 : finder eyepiece 
               108 : LCD monitor 
               109 : circuit board 
               201 : N-type semiconductor layer 
               202 : P-type semiconductor layer 
               203  and  802 : photodiode 
               204 : interlayer insulation film 
               205 : light shielding film 
               207 : condenser lens 
               301  and  701 : multilayer interference filter 
               302  to  304  and  702  to  704 : λ/4 multilayer film 
               401 ,  411 ,  601 ,  611 , and  621 : transmissivity characteristic of blue filter 
               402 ,  412 ,  602 ,  612 , and  622 : transmissivity characteristic of green filter 
               403 ,  413 ,  603 ,  613 , and  623 : transmissivity characteristic of red filter 
               501 ,  503 ,  507 , and  509 : titanium dioxide layer 
               502 ,  504 , and  508 : silicon dioxide layer 
               505  and  506 : resist 
               801 : silicon substrate 
               803 : CCD 
               804  and  805 : planarizing layer 
               806 : invisible light cut filter 
               807 : red filter 
               808 : color separation filter 
           
         
       
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     The following describes an embodiment of a solid-state imaging device and a camera according to the present invention using a digital camera as an example, with reference to the drawings. 
     [1] Structure of Digital Camera 
     First, the structure of a digital camera according to the embodiment is described. 
       FIG. 2  is a cross-sectional view showing the main structure of the digital camera according to the embodiment. 
     As shown in  FIG. 2 , a digital camera  1  includes a solid-state imaging element  101 , an imaging lens  102 , a cover glass  103 , a gear  104 , an optical finder  105 , a zoom motor  106 , a finder eyepiece  107 , an LCD (liquid crystal display) monitor  108 , and a circuit board  109 . 
     A user of the digital camera  1  observes a subject by looking through the optical finder  105  through the finder eyepiece  107  to select a camera angle. Also, the user operates the zoom motor  106  to adjust a zoom of the imaging lens  102  via the gear  104 . 
     Light from the subject penetrates through the cover glass  103  and the imaging lens  102 , and then enters the solid-state imaging element  101 . An imaging signal acquired in the solid-state imaging element  101  is signal-processed in the circuit board  109 , and is displayed on the LCD monitor  108 . Also, on the LCD monitor  108 , imaging modes and the like are displayed. 
     The cover glass  103  protects the imaging lens  102 , and furthermore achieves the waterproofing function. 
     [2] Structure of Solid-State Imaging Element  101   
     Next, the structure of the solid-state imaging element  101  according to the embodiment is described. The solid-state imaging element  101  includes two-dimensionally arrayed pixels, and performs imaging by detecting an amount of received light for each pixel. 
       FIG. 3  is a cross-sectional view showing the main structure of the solid-state imaging element  101  according to the embodiment. As shown in  FIG. 3 , the solid-state imaging element  101  is composed of a P-type semiconductor layer  202 , an interlayer insulation film  204 , a wavelength separation filter  206 , and condenser lenses  207  that are sequentially laminated on an N-type semiconductor layer  201 . 
     A photodiode  203  is formed for each pixel on an inner surface of the P-type semiconductor layer  202  that is closer to the interlayer insulation film  204  by ion-implanting N-type impurities such as arsenic (As). The P-type semiconductor layer  202  that functions as an element separation region separates adjacent photodiodes  203 . 
     Furthermore, the interlayer insulation film  204  is composed of translucent materials such as silicon oxide (SiO 2 ), silicon nitride (SiN), and borophosphosilicate glass (BPSG). Inside the interlayer insulation film  204 , light shielding films  205  are formed, which also function as metal wirings. The light shielding films  205  include apertures respectively corresponding to the photodiodes  203 . 
     The wavelength separation filter  206  realizes color-imaging by transmitting light having a wavelength within a wavelength range predetermined for each pixel. In the embodiment, the wavelength separation filter  206  transmits any of red light, green light, and blue light for each pixel. Furthermore, the wavelength separation filter  206  shields invisible light. 
     The condenser lens  207  is provided for each pixel, and condenses incident light onto the photodiode  203  corresponding thereto. In this case, the light shielding film  205  shields light such that the incident light condensed by the condenser lens  207  enters only the photodiode  203  corresponding to the condenser lens  207 . 
     [3] Structure of Wavelength Separation Filter  206   
     Next, the structure of the wavelength separation filter  206  is described in further detail. 
     The wavelength separation filter  206  is composed of an infrared filter for shielding infrared light that is laminated on a visible light filter for transmitting any of red light, green light, and blue light. The visible light filter is composed of a multilayer interference filter. The infrared filter is composed of a plurality of λ/4 multilayer films. 
       FIG. 4  is a cross-sectional view showing the structure of the wavelength separation filter  206 . As shown in  FIG. 4 , the wavelength separation filter  206  is composed of λ/4 multilayer films  302  to  304  that are sequentially laminated on a multilayer interference filter  301 . Although the condenser lenses  207  are provided on the wavelength separation filter  206  and the interlayer insulation film  204  is provided beneath the wavelength separation filter  206  as shown in  FIG. 3 , these compositional elements are omitted in  FIG. 4 . The multilayer interference filter  301  is composed of a part for transmitting blue light (“blue filter”)  301 B, a part for transmitting green light (“green filter”)  301 G, and a part for transmitting red light (“red filter”)  301 . 
     The multilayer interference filter  301  is composed of two λ/4 multilayer films with a dielectric layer (“spacer layer”) sandwiched therebetween. Each of the λ/4 multilayer films is a multilayer film composed of two types of dielectric layers that are alternately laminated and have the same optical thickness and different refractive indexes. The λ/4 multilayer film reflects light having a wavelength within a wavelength range that has, as a center wavelength, four times an optical thickness of the dielectric layer (hereinafter referred to as a “set-wavelength”). Here, the optical thickness is a value obtained by multiplying a physical thickness of the dielectric layer by a refractive index of the dielectric layer. A λ/4 multilayer film having a set-wavelength of 530 nm has an optical thickness of 132.5 nm for each dielectric layer. 
     In the embodiment, titanium dioxide (TiO 2 ) is used as a material of a high refractive index layer, and silicon dioxide (SiO 2 ) is used as a material of a low refractive index layer. Since titanium dioxide has a refractive index of 2.51, the high refractive index layer has a physical thickness of 52.8 nm. Since silicon dioxide has a refractive index of 1.45, the low refractive index layer has a physical thickness of 91.4 nm. 
     The spacer layer is a translucent insulation layer composed of silicon dioxide, and has a film thickness corresponding to a wavelength of light to be transmitted by the wavelength separation filter  206 . The spacer layer has physical thicknesses of 130 nm, 0 nm, and 30 nm in the blue filter  301 B, the green filter  301 G, and the red filter  301 R, respectively. 
     In the multilayer interference filter  301 , the blue filter  301 B and the red filter  301 R are each composed of seven layers, and the green filter  301 G is composed of five layers. 
     The λ/4 multilayer films  302  to  304  have set-wavelengths different from each other that are in a range of 800 nm to 1000 nm. In the embodiment, the λ/4 multilayer films  302  to  304  have set-wavelengths of 800 nm, 900 nm, and 1000 nm, respectively. Each of the λ/4 multilayer films  302  to  304  has a constant film thickness regardless of color of light transmitted by the multilayer interference filter  301 . 
     Each of the λ/4 multilayer films  302  to  304  is composed of alternately laminated silicon dioxide layers and titanium dioxide layers in the same way as the multilayer interference filter  301 . The layer structure of the λ/4 multilayer films  302  to  304  is expressed as below. 
       (0.5L 1 ·H 1 ·0.5L 1 ) x (0.5L 2 ·H 2 ·0.5L 2 )(0.5L 3 ˜H 3 ·0.5L 3 ) y    
     L 1 , L 2 , and L 3  represent low refractive index layers of the λ/4 multilayer films  302  to  304 , respectively. H 1 , H 2 , and H 3  represent high refractive index layers of the λ/4 multilayer films  302  to  304 , respectively. 0.5L i  (i=1 to 3) represents a low refractive index layer having an optical thickness equal to ½ of Li. 
     (0.5L i ·H i ·0.5L i ) represents a laminated structure in which a high refractive index layer H i  having an optical thickness equal to ¼ of the set-wavelength and a low refractive index layer 0.5L i  having an optical thickness equal to ⅛ of the set-wavelength are sequentially laminated on a low refractive index layer 0.5L i  having an optical thickness equal to ⅛ of the set-wavelength. 
     Also, (0.5L i ·H i ·0.5L i ) n  represents a laminated structure in which the laminated structure (0.5L i ·H i ·0.5L i ) is repeated n times. Note when the laminated structure (0.5L i ·H i ·0.5L i ) is repeated a plurality of times, the highest layer 0.5L i  included in the lower laminated structure (0.5L i ·H i ·0.5L i ) and the lowest layer 0.5L i  included in the higher laminated structure (0.5L i ·H i ·0.5L i ) constitute a low refractive index layer L i  having an optical thickness equal to ¼ of the set-wavelength. 
     Likewise, the highest layer 0.5L 1  included in the λ/4 multilayer film  302  and the lowest layer 0.5L 2  included in the λ/4 multilayer film  303  constitute a single silicon dioxide layer. The highest layer 0.5L 2  included in the λ/4 multilayer film  303  and the lowest layer 0.5L 3  included in the λ/4 multilayer film  304  constitute a single silicon dioxide layer. Also, x and y are 11. Accordingly, in the embodiment, the total number of layers that constitute the λ/4 multilayer films  302  to  304  is 23. 
     [4] Transmissivity Characteristics 
     Next, transmissivity characteristics of the wavelength separation filter  206  are described. 
       FIGS. 5A and 5B  are graphs showing transmissivity characteristics of the wavelength separation filter  206  according to the embodiment, where  FIG. 5A  shows transmissivity characteristics of the whole of the wavelength separation filter  206 , and  FIG. 5B  shows transmissivity characteristics of the multilayer interference filter  301 . 
     In  FIG. 5 , graphs  401  and  411  show transmissivity characteristics relating to the blue filter  301 B. Also, graphs  402  and  412  show transmissivity characteristics relating to the green filter  301 G. Graphs  403  and  413  show transmissivity characteristics relating to the red filter  301 . 
     As shown in  FIG. 5A , with the use of the wavelength separation filter  206  according to the embodiment, wavelength separation of incident light can be performed for each of the three wavelength ranges in visible light region. Furthermore, transmissivity of light having a wavelength within a wavelength range of 700 nm to 1000 nm can be suppressed to 2% or less, with respect to all of the red filter  301 , the green filter  301 G, and the blue filter  301 B. 
     On the other hand, as shown in  FIG. 5B , with the use of only the multilayer interference filter  301 , wavelength separation of incident light can be performed for each of the three wavelength ranges in visible light region. However, the transmissivity of light having a wavelength within the wavelength range of 700 nm to 1000 nm increases. For example, the blue filter  301 B has a as much as 80% or more transmissivity of infrared light having a wavelength within a wavelength range of 800 nm or more. 
     If receiving such infrared light, the photodiodes  203  generate signal charges. Accordingly, the use of only the multilayer interference filter  301  for color-imaging using visible light cannot achieve a sufficient wavelength separation function. 
     On the other hand, with the use of the wavelength separation filter  206  according to the embodiment, infrared light does not enter the photodiodes  203 . Therefore, it is possible to achieve a high wavelength separation function. 
     [5] Manufacturing Method of Wavelength Separation filter  206   
     Next, a manufacturing method of the wavelength separation filter  206  is described. 
       FIG. 6  shows manufacturing processes of the wavelength separation filter  206  according to the embodiment. In  FIG. 6 , the manufacturing processes of the wavelength separation filter  206  proceed from a process (a) to a process (h). Also, depictions of the N-type semiconductor layer  201 , the P-type semiconductor layer  202 , the photodiodes  203 , and the light shielding films  205  are omitted in  FIG. 6 . 
     First, as shown in the process (a), a titanium dioxide layer  501 , a silicon dioxide layer  502 , a titanium dioxide layer  503 , and a silicon dioxide layer  504  are sequentially laminated on the interlayer insulation film  204  using an RF (radio frequency) sputtering device. 
     The titanium dioxide layers  501  and  503  and the silicon dioxide layer  502  each have an optical thickness of 132.5 nm, and these layers constitute a λ/4 multilayer film. Also, the silicon dioxide layer  504  has a physical thickness equal to a physical thickness of a spacer layer that constitutes the blue filter  301 B. 
     Next, a resist  505  is formed on a part of the silicon dioxide layer  504  that corresponds to the blue filter  301 B (a process (b)). A part of the silicon dioxide layer  504  on which the resist  505  is not formed is etched to reduce a film thickness thereof (a process (c)). Then, the resist  505  is removed (a process (d)). 
     Furthermore, a resist  506  is formed on a part of the silicon dioxide layer  504  that correspond to the red filter  301 R and the blue filter  301 B (a process (e)). After a part of the silicon dioxide layer  504  on which the resist  506  is not formed is etched (a process (f)), the resist  506  is removed. 
     In order to etch the silicon dioxide layer  504 , for example, a resist material is applied on a wafer surface, pre-exposure baking (prebake) is performed. Then, exposure is performed using a lithography device such as a stepper, and the resists  505  and  506  are formed by performing resist development and final baking (postbake). Then, the silicon dioxide layer  504  can be physically etched using a tetrafluoromethane (CF 4 ) etching gas. 
     Next, on the silicon dioxide layer  504  and on a part of the titanium dioxide layer  503  that corresponds to the green filter  301 G, titanium dioxide layers  507 , silicon dioxide layers  508 , and titanium dioxide layers  509  are sequentially formed using an RF sputtering device (a process (g)). As a result, the blue filter  301 B and the red filter  301 R are each composed of seven layers. The green filter  301 G is composed of five layers including, as one layer, a titanium dioxide layer composed of the titanium dioxide layer  507  laminated on the titanium dioxide layer  503 . 
     Then, silicon dioxide layers and titanium dioxide layers are alternately laminated on the titanium dioxide layer  509  to form the λ/4 multilayer films  302  to  304  (the process (h)). As described above, the λ/4 multilayer films  302  to  304  have set-wavelengths of 800 nm, 900 nm, and 1000 nm, respectively. 
     [6] Modifications 
     Although the present invention has been described based on the above embodiment, the present invention is not of course limited to the embodiment, and further includes the following modifications. 
     (1) Although only the case in which the total number of layers that constitute the λ/4 multilayer films  302  to  304  is 23 has been described in the above embodiment, the present invention is of course not limited to this structure. Instead, a λ/4 multilayer film composed of any other number of layers may be used. 
       FIGS. 7A to 7C  are graphs showing relations between the total number of layers of the λ/4 multilayer films  302  to  304  and characteristics of wavelength separation, where  FIG. 7A  shows a relation in a case where x and y are 2 (11 layers in total),  FIG. 7B  shows a relation in a case where x and y are 4 (19 layers in total), and  FIG. 7C  shows a relation in a case where x and y are 6 (27 layers in total). 
     Note that each of the λ/4 multilayer films  302  to  304  has a set-wavelength that is the same as that in the above embodiment. Also, in  FIG. 7 , graphs  601 ,  611 , and  621  show transmissivity characteristics of the blue filter  301 B. Furthermore, graphs  602 ,  612 , and  622  show transmissivity characteristics of the green filter  301 G. Graphs  603 ,  613 , and  623  show transmissivity characteristics of the red filter  301 R. 
     As shown in  FIGS. 7A to 7C , the transmissivity of light having a wavelength within a wavelength range of 700 nm to 1000 nm exceeds 10% in  FIG. 7A , drops to 5% or less in  FIG. 7B , and is suppressed to 1% or less in  FIG. 7C . In this way, as the λ/4 multilayer films  302  to  304  have more number of layers, the transmissivity of light having a wavelength within the wavelength range of 700 nm to 1000 nm is reduced more. Accordingly, better transmissivity characteristics can be achieved. 
     However, increase in the number of layers might cause increase in manufacturing cost and decrease in yield rate. Therefore, it is desirable that the number of layers is determined so as to achieve characteristics of wavelength separation commensurate with manufacturing cost. 
     (2) Although only the case in which three kinds of λ/4 multilayer films each having a different set-wavelength is used for shielding infrared light is described in the above embodiment, the present invention is of course not limited to this structure. Instead of the three kinds of λ/4 multilayer films, two kinds of λ/4 multilayer films or four kinds of λ/4 multilayer films may be used. Furthermore, a λ/4 multilayer film having a set-wavelength different from that in the above embodiment may be used for shielding infrared light. 
     However, needles to say, a set-wavelength of a λ/4 multilayer film needs to be determined so as to shield infrared light, at least near infrared light having a wavelength within a wavelength range of 700 nm to 1000 nm. 
     (3) Although only the case in which the λ/4 multilayer films are formed on the multilayer interference film  301  is described in the above embodiment, the present invention is of course not limited to this structure. Instead, a multilayer interference film may be formed on a λ/4 multilayer film. 
       FIG. 8  is a cross-sectional view showing the structure of a wavelength separation filter according to the modification (3). As shown in  FIG. 8 , a wavelength separation filter  7  according to the modification (3) is composed of λ/4 multilayer films  703  and  704  and a multilayer interference film  701  that are sequentially laminated on a λ/4 multilayer film  702 . 
     With this structure, no difference is formed between pixels in the λ/4 multilayer films  702  to  704 . In other words, dielectric layers that constitute the λ/4 multilayer films  702  to  704  can be planarized over a plurality of two-dimensionally arrayed pixels. This can suppress deterioration in characteristics caused by oblique light, which becomes prominent due to pixel size reduction. 
     (4) Although only the case in which silicon dioxide and titanium dioxide are used as the dielectric materials is described in the above embodiment, the present invention is of course not limited to this structure. Instead, the following may be used: magnesium oxide (MgO), ditantalum pentoxide (Ta 2 O 5 ), zirconium dioxide (ZrO 2 ) silicon nitride (SiN), trisilicon tetranitride (Si 3 N 4 ), dialuminum trioxide (Al 2 O 3 ), magnesium difluoride (MgF 2 ), and hafnium trioxide (HfO 3 ). 
     Particularly, trisilicon tetranitride, ditantalum pentoxide, and zirconium dioxide are preferably used as high refractive index materials. Regardless of type of dielectric materials, the effects of the present invention can be achieved. 
     (5) Although the case in which each of the λ/4 multilayer films that constitute the multilayer interference film as a visible light filter is composed of eight layers is described in the above embodiment, the present invention is of course not limited to this structure. Instead, the λ/4 multilayer interference films may be composed of four layers, 12 layers, 16 layers, or more number of layers. 
     Also, the spacer layer may be composed of a material that is the same as a material of the high refractive index layer of the λ/4 multilayer films or a material of the low refractive index layer of the λ/4 multilayer films. Furthermore, the spacer layer may be composed of a material that is different from all the materials of the layers that constitute the λ/4 multilayer films. 
     INDUSTRIAL APPLICABILITY 
     The solid-state imaging device and the camera according to the present invention are effective as an art for shielding infrared light included in incident light.