Abstract:
A method for manufacturing a sloped structure is disclosed. The method includes the steps of: (a) forming a sacrificial film above a substrate; (b) forming a first film above the sacrificial film; (c) forming a second film having a first portion connected to the substrate, a second portion connected to the first film, and a third portion positioned between the first portion and the second portion; (d) removing the sacrificial film; and (e) bending the third portion of the second film after the step (d), thereby sloping the first film with respect to the substrate.

Description:
[0001]    The entire disclosure of Japanese Patent Application No. 2011-164537, filed Jul. 27, 2011 is expressly incorporated by reference herein. 
       BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present invention generally relates to micro sloped structures, methods for manufacturing a sloped structure, and spectrum sensors using the sloped structure. 
         [0004]    2. Related Art 
         [0005]    Spectrum sensors are used in the medical, agricultural and environmental fields for diagnosing and examining objects. For example, in the medical field, a pulse oximeter is used to measure the oxygen saturation of blood, using light absorption of hemoglobin. Also, in the agricultural field, a saccharometer is used to measure the concentration of sugar content of fruits, using light absorption of sugar. 
         [0006]    Japanese Laid-open Patent Application HEI 6-129908 (related art) describes a spectroscopic imaging sensor that restricts incident angles of light with an optical fiber that optically connects interference filters and photovoltaic converter elements, thereby restricting the transmission wavelength bandwidth of light to the photovoltaic conversion elements. However, miniaturization of such a spectrum sensor by the related art is difficult. 
         [0007]    For example, for manufacturing a small-size spectrum sensor, micro sloped structures need to be formed. However, it has been difficult to manufacture such micro structures according to the related art. 
       SUMMARY 
       [0008]    The invention has been made in view of the technical difficulty described above. Some of aspects of the invention pertain to providing a micro sloped structure, a method for manufacturing a micro sloped structure, and a spectrum sensor using the sloped structure. 
         [0009]    In accordance with an embodiment of the invention, a method for manufacturing a sloped structure includes the steps of; (a) forming a sacrificial film above a substrate; (b) forming a first film above the sacrificial film; (c) forming a second film having a first portion connected to the substrate, a second portion connected to the first film, and a third portion positioned between the first portion and the second portion; (d) removing the sacrificial film; and (e) bending the third portion of the second film after the step (d), thereby sloping the first film with respect to the substrate. According to the aspect described above, a micro sloped structure can be readily manufactured with a process having high affinity to a semiconductor device fabrication process. 
         [0010]    In accordance with an aspect of the embodiment of the invention, the manufacturing method may preferably further include the step (f), between the step (b) and the step (c), of patterning the sacrificial film and the first film to expose a side surface of the sacrificial film on which the third portion of the second film is formed. According to this aspect, by forming the sacrificial film and the first film and then patterning them, a sloped structure can be formed at any specified location on the substrate. 
         [0011]    In accordance with an aspect of the embodiment of the invention, the step (e) may preferably include supplying liquid between the first film and the substrate, and then removing the liquid. According to this aspect, the second film can be bent and the first film can be sloped without having to apply an excessive force to the first film and the second film. 
         [0012]    In the embodiment described above, the manufacturing method may preferably further include the step (g), after the step (e), of filling material for a third film between the first film and the substrate. According to this aspect, by forming the third film, the optical characteristic of the sloped structure can be adjusted. 
         [0013]    In the embodiment described above, the manufacturing method may preferably further include the step (h), after the step (g), of removing the first film and the second film. According to this aspect, as the first film and the second film are removed, the degree of freedom in selecting material for the first film and the second film can be improved. 
         [0014]    In accordance with another embodiment of the invention, a sloped structure includes: a first film located above a substrate and sloped with respect to a first surface of the substrate; and a second film located above the substrate and having a first section connected to the first surface of the substrate, a second section connected to the first film, and a third section connecting the first section with the second section. According to this aspect, a useful optical device using a micro sloped structure can be manufactured. In this embodiment, the third section may preferably have a curved surface. 
         [0015]    In accordance with an aspect of the embodiment described above, the second section of the second film may preferably be located above the first film. By this aspect, the number of patterning steps can be reduced compared to the case where the second film is formed below the first film. 
         [0016]    In accordance with an aspect of the embodiment described above, the sloped structure may further include a third film between the first film and the substrate. According to this aspect, by forming the third film, the optical characteristic of the sloped structure can be adjusted. 
         [0017]    In accordance with still another embodiment of the invention, a spectrum sensor includes an angle restriction filter that restricts an incident direction of passing light, a multilayered film that restricts wavelength of transmitting light or reflecting light according to the incident direction, any one of the sloped structures described above that specifies an inclination angle between the incident direction of light passing through the angle restriction filter and a lamination direction of the multilayered film, and a photodiode that detects light passing through the angle restriction filter and transmitted through or reflected at the multilayered film. According to the embodiment described above, by implementing the sloped structure, a small-size spectrum sensor can be manufactured. It is noted that the term “above” used in the description means a direction opposite to the direction toward the back surface of the substrate with the top surface of the substrate as reference. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIGS. 1A-1D  are cross-sectional views showing a method for manufacturing a sloped structure in accordance with a first embodiment of the invention. 
           [0019]      FIGS. 2E-2H  are cross-sectional views showing the method for manufacturing a sloped structure in accordance with the first embodiment of the invention. 
           [0020]      FIGS. 3I-3M  are cross-sectional views showing the method for manufacturing a sloped structure in accordance with the first embodiment of the invention. 
           [0021]      FIGS. 4A-4D  are cross-sectional views showing a method for manufacturing a sloped structure in accordance with a second embodiment of the invention. 
           [0022]      FIGS. 5E-5H  are cross-sectional views showing the method for manufacturing a sloped structure in accordance with the second embodiment of the invention. 
           [0023]      FIGS. 6I-6M  are cross-sectional views showing the method for manufacturing a sloped structure in accordance with the second embodiment of the invention. 
           [0024]      FIGS. 7A-7D  are cross-sectional views showing a method for manufacturing a sloped structure in accordance with a third embodiment of the invention. 
           [0025]      FIGS. 8E-8H  are cross-sectional views showing the method for manufacturing a sloped structure in accordance with the third embodiment of the invention. 
           [0026]      FIGS. 9I-9M  are cross-sectional views showing the method for manufacturing a sloped structure in accordance with the third embodiment of the invention. 
           [0027]      FIGS. 10A-10D  are views showing a first configuration example of the sloped structure in each of the embodiments. 
           [0028]      FIGS. 11A-11D  are views showing a second configuration example of the sloped structure in each of the embodiments. 
           [0029]      FIGS. 12A-12D  are views showing a third configuration example of the sloped structure in each of the embodiments. 
           [0030]      FIGS. 13A-13D  are views showing a fourth configuration example of the sloped structure in each of the embodiments. 
           [0031]      FIGS. 14A-14D  are views showing a fifth configuration example of the sloped structure in each of the embodiments. 
           [0032]      FIGS. 15A-15D  are views showing a sixth configuration example of the sloped structure in each of the embodiments. 
           [0033]      FIG. 16  is a cross-sectional view of a first example of a spectrum sensor in accordance with an embodiment of the invention. 
           [0034]      FIG. 17  is a cross-sectional view of a second example of a spectrum sensor in accordance with an embodiment of the invention. 
       
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0035]    Embodiments of the invention are described in detail below. It is noted that the embodiments described below do not unduly limit the contents of the invention set forth in the scope of patent claims. Also, not all of the compositions described in the embodiments would necessarily be essential for the solution provided by the invention. Furthermore, the same components will be appended with the same reference numbers, and their description will not be repeated. 
       1. FIRST EMBODIMENT 
       [0036]      FIGS. 1-3  are cross-sectional views showing a method for manufacturing a sloped structure in accordance with a first embodiment of the invention. The manufacturing method in accordance with the present embodiment uses the semiconductor processing technology, thereby providing a low-cost manufacturing method that can readily achieve device miniaturization. 
       1-1. Film Formation of First Film 
       [0037]    First, as shown in  FIG. 1A , a sacrificial film  20  is formed on a substrate  10 . The substrate  10  may be, for example, a single crystal silicon substrate, or a silicon substrate with an angle restriction filter (to be described below) formed thereon. As the sacrificial film  20 , for example, a silicon oxide (SiO 2 ) film may be used. 
         [0038]    Next, as shown in  FIG. 1B , a first film  11  that becomes a film composing sloped structures, is formed on the sacrificial film  20 . As the first film  11 , for example, a titanium nitride (TiN) film may be used. 
         [0039]    Next, as shown in  FIG. 1C , a resist film  21  is formed on the first film  11 , and the resist film  21  is patterned into a predetermined shape (for example, a rectangular shape), by exposing and developing the resist film  21 . Then, as shown in  FIG. 1D , the first film  11  and the sacrificial film  20  are etched, using the resist film  21  as an etching mask. By this step, the first film  11  and the sacrificial film  20  are patterned into the same shape as the predetermined shape (for example, a rectangular shape). Thereafter, the resist film  21  is removed. 
         [0040]    In the steps described above, the first film  11  is formed, and then the first film  11  and the sacrificial film  20  are concurrently patterned. However, without any particular limitation to the above, the sacrificial film  20  may be patterned first, and then the first film  11  may be formed on the sacrificial film  20 . 
       1-2. Film Formation of Second Film 
       [0041]    Next, as shown in  FIG. 2E , a second film  12  that serves as a film for composing a sloped structure is formed in a manner to cover the top surface of the first film  11 , the top surface of the substrate  10  exposed in the step shown in  FIG. 1D , and the side surface of the sacrificial film  20  and the side surface of the first film  11  which are exposed by the step shown in  FIG. 1D . The second film  12  may be formed by, for example, a physical vapor deposition (PVD) method including a sputter method, a vacuum deposition method, or the like, or a chemical vapor deposition (CVD) method. As the second film  12 , for example, an aluminum (Al) film may be used. 
         [0042]    Next, as shown in  FIG. 2F , a resist film  22  is formed on the second film  12 , and the resist film  22  is subject to exposure and development thereby being patterned into a predetermined shape. In this instance, the resist  22  is patterned into a shape that covers one side surface  201  of the sacrificial film  20 , one side surface  111  of the first film  11 , a partial region  112  of the top surface of the first film  11  that connects to its side surface, and a partial region  101  of the top surface of the substrate  10 . 
         [0043]    Next, the second film  12  and the first film  11  are etched, using the resist film  22  as an etching mask, as shown in  FIG. 2G . By this etching, the second film  12  is substantially removed, while leaving a first portion  12   a  connected to the substrate  10 , a second portion  12   b  connected to the first film  11 , and a third portion  12   c  extending along one side surface of the sacrificial film  20 . Thereafter, the resist film  22  is removed. 
         [0044]    Next, as shown in  FIG. 2H , the sacrificial film  20  is removed by, for example, wet etching. When the sacrificial film  20  is composed of, for example, silicon oxide, for example, hydrofluoric acid (HF) may be used as the etching liquid for removing the sacrificial film  20 . 
         [0045]    By removing the sacrificial film  20 , a space  102  is formed between the substrate  10  and the first film  11 . The first portion  12   a  of the second film  12  is connected to the substrate  10 , and the second portion  12   b  of the second film  12  is connected to the entire top surface of the first film  11 . The third portion  12   c  of the second film  12  is located between the first portion  12   a  and the second portion  12   b,  thereby supporting the first film  11 . 
         [0046]    In the example described above, the second portion  12   b  of the second film  12  is located above the first film  11 . However, without any particular limitation to the example, the second portion  12   b  of the second film  12  may be located below the first film  11 . For example, a second film  12  may be formed on the top surface and the side surface of a sacrificial film  20  that has been patterned and then the second film  12  may be patterned. Thereafter, a first film  11  may be formed on the second film  12  located above the sacrificial film  20 . 
         [0047]    Also, in the example described above, the second portion  12   b  of the second film  12  is connected to the entire top surface of the first film  11 . However, without any particular limitation to the example, the second portion  12   b  of the second film  12  may be connected at least to a first end section  11   a  of the first film  11 . 
       1-3. Formation of Slope 
       [0048]    Next, as shown in  FIG. 3I , liquid is supplied in the space between the substrate  10  and the first film  11 . For example, the substrate  10 , the first film  11  and the second film  12  may be submerged in liquid having large surface tension (for example, water) stored in a container (not shown), and thereafter removed from the container. 
         [0049]    Next, as shown in  FIG. 3J , the liquid supplied in the space between the substrate  10  and the first film  11  is evaporated. In this instance, the liquid supplied in the space between the substrate  10  and the first film  11  pulls the second end portion  11   b  of the first film  11  toward the substrate  10  by its surface tension. As the liquid supplied in the space between the substrate  10  and the first film  11  evaporates, the liquid in the space reduces. By this, the second film  12  is bent, thereby tilting the first film  11 . The second film  12  may be folded. The first film  11  may preferably be sloped until the second end portion  11   b  of the first film  11  comes in contact with the substrate  10 . More preferably, the second end portion  11   b  and the substrate  10  may adhere to each other by sticking. The “sticking” is a phenomenon in which a substrate and a structure or structures surrounding liquid adhere to each other by the meniscus force generated by the surface tension that works when the liquid evaporates. By the steps described above, a first sloped structure including the first film  11  and the second film  12  is formed. 
         [0050]    Further, as shown in  FIG. 3K , liquid material for a third film  13  is filled between the first film  11  and the substrate  10 , if necessary. Thereafter, the liquid material is solidified by means of heating or the like. As the liquid material for forming the third film, for example, SOG (spin on glass) may be used. 
         [0051]    Next, as shown in  FIG. 3L , among the solidified liquid material, portions on the second film  12  are removed by anisotropic etching. By the steps described above, a second sloped structure including the first film  11 , the second film  12  and the third film  13  is formed. 
         [0052]    Further, as shown in  FIG. 3M , the first film  11  and the second film  12  may be removed by etching, if necessary. When the first film  11  is, for example, a titanium nitride film and the second film  12  is, for example, an aluminum film, aqueous ammonia/hydrogen peroxide mixture (NH 4 OH+H 2 O 2 ) may be used as the etching liquid for removing the first film  11  and the second film  12 . By removing the first film  11  and the second film  12 , a third sloped structure including only the third film  13  is formed. 
         [0053]    In the example described above, the first film  11  and the second film  12  are mutually independent films. However, without any particular limitation to the example, the first film  11  and the second film  12  may be formed from a one-piece film. When the rigidity of at least a portion of the second film  12  is smaller than the rigidity of the first film  11 , the second film  12  may be bent in the steps in  FIG. 3I  and  FIG. 3J , thereby forming the sloped structure. The sloped structure may be formed by folding the second film  12 . 
         [0054]    In the steps described above, the substrate  10  is a silicon substrate, the sacrificial film  20  is a silicon oxide film, the first film  11  is a titanium nitride film, the second film  12  an aluminum film, the etching liquid for removing the sacrificial film  20  is hydrofluoric acid, the third film  13  is SOG, and the etching liquid for removing the first film  11  and the second film  12  is aqueous ammonia/hydrogen peroxide mixture. However, the invention is not limited to the above, and the following combinations are possible. 
         [0055]    For example, the substrate  10  may be a silicon substrate, the sacrificial film  20  may be a titanium nitride and aluminum film, the first film  11  and the second film  12  may be silicon nitride (Si 3 N 4 ) film, the etching liquid for removing the sacrificial film  20  may be aqueous ammonia/hydrogen peroxide mixture, the third film  13  may be SOG, and the etching liquid for removing the first film  11  and the second film  12  may be phosphoric acid (H 3 PO 4 ). 
         [0056]    Also, for example, the substrate  10  may be a silicon substrate, the sacrificial film  20  may be a silicon oxide film, the first film  11  and the second film  12  may be made of resist material, the etching liquid for removing the sacrificial film  20  may be hydrofluoric acid, the third film  13  may be SOG, and the etching liquid for removing the first film  11  and the second film  12  may be white fuming nitric acid. 
         [0057]    Furthermore, for example, the substrate  10  may be a silicon nitride film, the sacrificial film  20  may be a silicon oxide film, the first film  11  may be a titanium nitride film, the second film  12  may be an aluminum film, the etching liquid for removing the sacrificial film  20  may be hydrofluoric acid, the third film  13  may be SOG, and the etching liquid for removing the first film  11  and the second film  12  may be aqueous ammonia/hydrogen peroxide mixture. 
       1-4. Effect of Embodiments 
       [0058]    According to the manufacturing process described above, by using film formation, exposure, development, etching techniques, and the like which have high affinity to a semiconductor device fabrication process, sloped structures can be manufactured. Accordingly, the invention makes it easier to mix and mount sloped structures and semiconductor circuits on a single chip. 
         [0059]    Also, the slope angle of the sloped structure can be finely adjusted by the length from the first end portion  11   a  of the first film  11  to the second end portion  11   b,  and the height of the first film from the substrate  10  (the thickness of the sacrificial film  20 ). 
         [0060]    Further, it is not necessary to make metal molds, which are expensive and quickly worn down, for manufacturing sloped structures, and it is not necessary to remake metal molds for changing the shape of the sloped structures. Moreover, according to the manufacturing process described above, micro sloped structures can be manufactured not only with materials that can be formed by metal molds, but also with any one of other various materials. 
       2. SECOND EMBODIMENT 
       [0061]      FIGS. 4-6  are cross-sectional views showing a method for manufacturing a sloped structure in accordance with a second embodiment of the invention. The manufacturing method in accordance with the second embodiment pertains to a method by which a plurality of sloped structures having different slope angles can be concurrently manufactured on a single substrate  10 . 
         [0062]    Steps shown in  FIGS. 4-6  are generally the same in many respects as those shown in  FIGS. 1-3 . However, as shown in  FIG. 4C  and  FIG. 4D , the process in accordance with the second embodiment is different from the process shown in  FIGS. 1-3  in that a plurality of resist films  21  having different areas are formed on a first film  1 , and a plurality of first films  11  having different lengths are formed. 
         [0063]    Then, sloped structures are formed in a manner similar to the process shown in  FIGS. 1-3 , such that a plurality of sloped structures having different slope angles can be formed according to the length from the first end section  11   a  to the second end section  11   b  of each of the first films  11 . 
       3. THIRD EMBODIMENT 
       [0064]      FIGS. 7-9  are cross-sectional views showing a method for manufacturing a sloped structure in accordance with a third embodiment of the invention. The manufacturing method in accordance with the third embodiment pertains to a method by which a plurality of sloped structures having different slope orientations can be concurrently manufactured on a single substrate  10 . 
         [0065]    Steps shown in  FIGS. 7-9  are generally the same in many respects as those shown in  FIGS. 1-3 . However, as shown in  FIG. 8F  and  FIG. 8G , the process in accordance with the third embodiment is different from the process shown in  FIGS. 1-3  in that resist films  22  are formed in a manner to cover side surfaces of a plurality of sacrificial films  20  which face mutually different directions, and a plurality of second films  12  are formed in a manner that second portions  12   b  of the second films  12  face mutually different directions. 
         [0066]    Then, sloped structures are formed in a manner similar to the process shown in  FIGS. 1-3 , such that a plurality of sloped structures having different slope orientations can be formed according to the orientations of the second portions  12   b  of the second films  12 . 
       4. CONFIGURATION EXAMPLES OF SLOPED STRUCTURES 
     4-1. First Configuration Example 
       [0067]      FIGS. 10A-10D  are views showing a first configuration example of the sloped structure in each of the embodiments.  FIG. 10A  is a plan view,  FIG. 10B  is a rear side view,  FIG. 10C  is a side view, and  FIG. 10D  is a front view. As shown in  FIGS. 10A-10D , a sloped structure  1   a  in accordance with the first configuration example includes a first film  11  and a second film  12  located above a substrate  10 . 
         [0068]    The first film  11  is sloped with respect to the substrate  10 , and includes a first end section  11   a  spaced a longer distance from the substrate  10  and a second end section  11   b  spaced a shorter distance from the substrate  10 . In the first configuration example, the second end section  11   b  of the first film  11  is in contact with the substrate  10 . 
         [0069]    The second film  12  includes a first portion  12   a  connected to the substrate  10 , a second portion  12   b  connected to the top surface of the first film  11 , and a third portion  12   c  located between the first portion  12   a  and the second portion  12   b  and has a curved surface. The curved surface may be made of a bent surface. 
       4-2. Second Configuration Example 
       [0070]      FIGS. 11A-11D  are views showing a second configuration example of the sloped structure in each of the embodiments.  FIG. 11A  is a plan view,  FIG. 11B  is a rear side view,  FIG. 11C  is a side view, and  FIG. 11D  is a front view. As shown in  FIGS. 11A-11D , a sloped structure  1   b  in accordance with the second configuration example is different from that of the first configuration example in that the second film  12  includes a fourth portion  12   d  that protrudes farther than the second end section  11   b  of the first film  11 . 
         [0071]    The fourth portion  12   d  of the second film  12  contacts the substrate  10 , and more preferably adhere to the substrate  10  by sticking. According to the second configuration example, the fourth portion  12   d  provides a large contact surface with the substrate  10 , such that the sloped structure can be stabilized. 
       4-3. Third Configuration Example 
       [0072]      FIGS. 12A-12D  are views showing a third configuration example of the sloped structure in each of the embodiments.  FIG. 12A  is a plan view,  FIG. 12B  is a rear side view,  FIG. 12C  is a side view, and  FIG. 12D  is a front view. As shown in  FIGS. 12A-12D , a sloped structure  1   c  in accordance with the third configuration example is different from that of the first configuration example in that a through-hole  11   c  is formed in the first end portion  11   a  of the first film  11  and the second portion  12   b  of the second film  12 . 
         [0073]    According to the third configuration example, air can escape through the through-hole  11   c  when liquid material for the third film  13  is filled between the first film  11  and the substrate  10 , such that a sloped structure with few air pockets can be formed. 
       4-4. Fourth Configuration Example 
       [0074]      FIGS. 13A-13D  are views showing a fourth configuration example of the sloped structure in each of the embodiments.  FIG. 13A  is a plan view,  FIG. 13B  is a rear side view,  FIG. 13C  is a side view, and  FIG. 13D  is a front view. As shown in  FIGS. 13A-13D , a sloped structure  1   d  in accordance with the fourth configuration example is different from that of the first configuration example in that a through-hole  12   e  is formed in the third portion  12   c  of the second film  12 . 
         [0075]    According to the fourth configuration example, when liquid material for the third film  13  is filled between the first film  11  and the substrate  10 , the liquid material may be charged through the through-hole  12   e,  or air can escape through the through-hole  12   e,  such that the step of filling liquid material can be smoothly conducted. 
       4-5. Fifth Configuration Example 
       [0076]      FIGS. 14A-14D  are views showing a fifth configuration example of the sloped structure in each of the embodiments.  FIG. 14A  is a plan view,  FIG. 14B  is a rear side view,  FIG. 14C  is a side view, and  FIG. 14D  is a front view. As shown in  FIGS. 14A-14D , a sloped structure  1   e  in accordance with the fifth configuration example is different from that of the first configuration example in that a groove  10   a  is formed in the surface of the substrate  10  opposite the first film  11 . 
         [0077]    According to the fifth configuration example, when liquid material for the third film  13  is filled between the first film  11  and the substrate  10 , the liquid material may be charged through the groove  10   a,  such that the step of filling liquid material can be smoothly conducted. 
       4-6. Sixth Configuration Example 
       [0078]      FIGS. 15A-15D  are views showing a sixth configuration example of the sloped structure in each of the embodiments.  FIG. 15A  is a plan view,  FIG. 15B  is a rear side view,  FIG. 15C  is a side view, and  FIG. 15D  is a front view. As shown in  FIGS. 15A-15D , a sloped structure if in accordance with the sixth configuration example is different from that of the first configuration example in that a concave section  11   d  is formed in the second end section  11   b  of the first film  11  and the second portion  12   b  of the second film  12 . 
         [0079]    According to the sixth configuration example, when liquid material for the third film  13  is filled between the first film  11  and the substrate  10 , the liquid material may be charged through the concave section  11   d,  or air can escape through the concave section  11   d,  such that the step of filling liquid material can be smoothly conducted. 
       5. TRANSMISSION TYPE SPECTRUM SENSOR 
       [0080]      FIG. 16  is a cross-sectional view of a first example of a spectrum sensor using the sloped structure in accordance with an embodiment of the invention. The spectrum sensor shown in  FIG. 16  includes an optical device section  50  having photodiodes, an angle restriction filter section  60 , and a spectrum filter section  70 . 
         [0081]    The optical device section  50  is equipped with a substrate  51  formed from semiconductor material such as silicon, and photodiodes  52   a,    52   b  and  52   c  formed in the substrate  10 . Further, the substrate  51  includes an electronic circuit (not shown) formed thereon to perform various operations, such as, applying a predetermined reverse bias voltage to the photodiodes  52   a,    52   b  and  52   c,  detecting a current based on photoelectric power generated at the photodiodes  52   a,    52   b  and  52   c,  amplifying analog signals according to the magnitude of the current, and converting the analog signals to digital signals. 
       5-1. Angle Restriction Filter Section 
       [0082]    The angle restriction filter section  60  is formed above the substrate  51 . The angle restriction filter section  60  includes a shield section  61  that forms optical path walls, and optical paths are formed by transmissive material  62  such as silicon oxide or the like surrounded by the optical path walls. The shield section  61  is formed from material that does not substantially transmit light having wavelengths to be received by the photodiodes  52   a,    52   b  and  52   c.  The shield section  61  may be formed with a plurality of layers in, for example, a predetermined lattice pattern sequentially deposited on the substrate  51 , whereby the optical paths are formed in a direction perpendicular to the surface of the substrate  51 . 
         [0083]    The incident angle of light passing through the optical paths is restricted by the angle restriction filter section  60 . More specifically, when light entered the optical paths is inclined more than a predetermined restriction angle with respect to the direction of the optical paths, the light hits the shield section  61 , a portion of the light is absorbed by the shield section  61 , and the remaining portion is reflected. The reflection is repeated and the reflected light becomes weaker while the light is passing through the optical paths. Accordingly, light that can pass the angle restriction filter section  60  is substantially limited to light that enters the optical paths at inclinations less than the predetermined restriction angle with respect to the optical paths. 
       5-2. Spectrum Filter Section 
       [0084]    The spectrum filter section  70  includes sloped structures  1  formed on the angle restriction filter section  60 , and a multilayer film  72  formed on the sloped structures  1 . The multilayer film  72  is formed from thin films of a low refractive index material such as silicon oxide and thin films of a high refractive index material such as titanium oxide, laminated in multiple layers, and slightly inclined with respect to the substrate  51 . The thin films of a low refractive index and the thin films of a high refractive index each have a predetermined film thickness, for example, on the order of submicron, and are laminated, for example, in about 60 layers in total, such that the entire multilayer film  72  is, for example, about 6 μm in thickness. 
         [0085]    The angle of inclination of the multilayer film  72  with respect to the substrate  51  may be set, for example, between 0 degree and 30 degrees, according to set wavelengths of light to be received by the photodiodes  52   a,    52   b  and  52   c.  In order to have the multilayer film  72  inclined with respect to the substrate  51 , the sloped structures  1  having light transmissivity are formed on the angle restriction filter section  60 , and the multilayer film  72  is formed on the sloped structures  1 . As the sloped structures  1 , sloped structures fabricated by the manufacturing method described above may be used. 
         [0086]    According to the structure described above, a portion of incident light that has entered the spectrum filter section  70  becomes reflected light and another portion thereof becomes transmitting light at an interface between a set of the low refractive index thin film and the high refractive index thin film. Then, a portion of the reflected light reflects again at an interface between another set of the low refractive index thin film and the high refractive index thin film, and couples with the aforementioned transmitting light. In this instance, when light has a wavelength that matches with the optical path length of reflected light, the reflected light and the transmitting light match in phase with each other, and thus strengthen each other. When light has a wavelength that does not match with the optical path length of reflected light, the reflected light and the transmitting light do not match in phase with each other, and thus weaken each other (destructively interfere with each other). 
         [0087]    Here, the optical path length of reflected light is determined by the angle of inclination of the multilayer film  72  with respect to the direction of the incident light. Accordingly, when the interference action described above is repeated in the multilayer film  72 , which is formed from as many as  60  layers in total, light having only specific wavelengths can pass through the spectrum filter section  70 , according to the incident angle of incident light, and is emitted from the spectrum filter section  70  at a predetermined emission angle (for example, at the same angle as the incident angle to the spectrum filter section  70 ). 
         [0088]    The angle restriction filter section  60  allows only light incident on the angle restriction filter section  60  in the predetermined range of restriction angles to pass therein. Accordingly, the wavelengths of light that passes through the spectrum filter section  70  and the angle restriction filter section  60  are restricted to a predetermined range of wavelengths, which is determined by the lamination direction of the multilayer film  72 , and the incident direction of incident light allowed by the angle restriction filter section  60  to pass. 
         [0089]    By forming in advance the sloped structures  1  having angles of inclination that differ depending on the set wavelengths of light to be received by the photodiodes  52   a,    52   b  and  52   c,  the multilayer film  72  can be formed in the same film thickness by a common process, regardless of the set wavelengths of light to be received by the photodiodes  52   a,    52   b  and  52   c.    
       5-3. Optical Device Section 
       [0090]    The photodiodes  52   a,    52   b  and  52   c  included in the optical device section  50  receive light that has passed through the spectrum filter section  70  and the angle restriction filter section  60 , and generate photovoltaic power. The photodiodes  52   a,    52   b  and  52   c  include impurity regions formed by ion injection or the like in the substrate  51  that is composed of semiconductor material. 
         [0091]    As light that has passed through the spectrum filter section  70  and the angle restriction filter section  60  is received by the photodiodes  52   a,    52   b  and  52   c,  photovoltaic power is generated, whereby an electric current is generated. By detecting the electric current by an electronic circuit (not shown), the light is detected. 
       5-4. Method for Manufacturing Spectrum Sensor 
       [0092]    Here, a method for manufacturing the spectrum sensor in the first example is briefly described. The spectrum sensor is manufactured through initially forming the photodiodes  52   a,    52   b  and  52   c  on the substrate  51 , then forming the angle restriction filter section  60  on the photodiodes  52   a,    52   b  and  52   c,  and then forming the spectrum filter section  70  on the angle restriction filter section  60 . 
         [0093]    According to the present embodiment, spectrum sensors can be manufactured in one continuous operation by the semiconductor process, and spectrum sensors using the sloped structures having any desired angles of inclination can be readily formed. Also, by using multiple sloped structures having different angles of inclination, light with multiple wavelengths can be detected. 
       6. REFLECTION TYPE SPECTRUM SENSOR 
       [0094]      FIG. 17  is a cross-sectional view of a second example of a spectrum sensor using the sloped structure in accordance with any one of the embodiments of the invention. The spectrum sensor shown in  FIG. 17  includes an optical device section  50  having photodiodes, an angle restriction filter section  60 , and a spectrum filter section  80 . 
         [0095]    The angle restriction filter section  60  is formed above the spectrum filter section  80 . The angle restriction filter section  60  may be formed separated from the spectrum filter section  80 , or may be formed in contact with the spectrum filter section  80 . 
         [0096]    The spectrum filter section  80  includes sloped structures  1   g  having a high reflection coefficient and a multilayer film  72  formed on the sloped structures  1   g.  As the sloped structures  1   g,  sloped structures manufactured by the manufacturing method described above may be used. 
         [0097]    According to the structure described above, the spectrum filter section  80  restricts wavelengths of reflecting light according to incident direction of light passing through the angle restriction filter section  60 . More specifically, among incident light passed through the angle restriction filter section  60  and entered the spectrum filter section  80 , only light having a specified wavelength is reflected by the spectrum filter section  80 , according to the incident angle, and is emitted from the spectrum filter section  80  at a predetermined emission angle (for example, at the same angle as the incident angle to the spectrum filter section  80 ). 
         [0098]    By forming in advance the sloped structures  1   g  having angles of inclination that differ depending on the set wavelengths of light to be received by the photodiodes  52   a  and  52   b,  the multilayer film  72  can be formed in the same film thickness by a common process, regardless of the set wavelengths of light to be received by the photodiodes  52   a  and  52   b.    
         [0099]    The photodiodes  52   a  and  52   b  included in the optical device section  50  receive light that has passed through the angle restriction filter section  60  and reflected by the spectrum filter section  80 , and generate photovoltaic power. 
         [0100]    As the device that uses the sloped structures, an optical sensor is described above. However, the sloped structure may be used as any one of other types of devices. For example, the sloped structure may be used as an optical device, such as, a prism, a mirror or the like for relaying light signals with a predetermined wavelength in a relay device for optical fibers.