Patent Publication Number: US-11652120-B2

Title: Light detection device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of U.S. patent application Ser. No. 16/827,866 filed Mar. 24, 2020, which is a divisional application of U.S. patent application Ser. No. 16/152,494, filed Oct. 5, 2018, which claims the benefit of priority to Japanese Patent Application No. 2017-196297, filed Oct. 6, 2017, the entire contents of each of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a light detection device. 
     BACKGROUND 
     As a light detection device, there is known a light detection device including a back-illuminated light receiving element which includes a plurality of light receiving portions, a circuit element, a bump which is disposed between the light receiving element and the circuit element, and an underfill which is disposed between the light receiving element and the circuit element. In such a light detection device, there is a case in which the underfill reaches a side surface of the light receiving element in order to reliably bond the light receiving element and the circuit element to each other. 
     However, when the underfill reaches the side surface of the light receiving element, there is a case in which light incident and refracted by the underfill is incident from the side surface of the light receiving element to the light receiving portion since the light receiving element is of a back illumination type. Since such light is noise light, the detection accuracy of the light detection device is degraded when such light is incident to the light receiving portion. 
     In order to solve the above-described problems, there is proposed a light detection device in which a resin containing a filler having a light shielding property is used as an underfill (for example, see Japanese Unexamined Patent Publication No. 2009-111090). 
     SUMMARY 
     However, there is concern that light cannot be sufficiently shielded in accordance with a wavelength even when the resin containing the filler having the light shielding property is used as the underfill. 
     An object of the present disclosure is to provide a highly reliable light detection device. 
     A light detection device of the present disclosure includes: a back-illuminated light receiving element including a plurality of light receiving portions; a circuit element; a connection member disposed between the light receiving element and the circuit element and configured to electrically and physically connects the light receiving element and the circuit element to each other; an underfill disposed between the light receiving element and the circuit element; and a frame-shaped light shielding mask disposed on the circuit element to surround the light receiving element when viewed from a light incident direction to the light receiving element, in which the light shielding mask includes a frame having an opening in which the light receiving element is located and a light shielding layer formed on an inner surface of the opening, in which a first opening edge on the side of the circuit element in the opening is located at the outside of an outer edge of the light receiving element when viewed from the light incident direction, in which a second opening edge opposite to the circuit element in the opening is located at the inside of the outer edge of the light receiving element when viewed from the light incident direction, in which the opening is narrowed from the first opening edge toward the second opening edge, in which a width of the frame increases from the first opening edge toward the second opening edge, and in which the underfill reaches a gap between the light receiving element and the light shielding layer formed on the inner surface of the opening. 
     In the light detection device, the light receiving element is located at the inside of the opening of the frame and the light shielding layer is formed on the inner surface of the opening of the frame. Further, the opening of the frame is narrowed from the first opening edge on the side of the circuit element toward the second opening edge opposite to the circuit element. Accordingly, even when light (stray light) is incident from the outside of the opening of the frame to the light shielding layer, the light is easily reflected toward, for example, the opposite side to the light receiving element. Thus, it is possible to prevent degradation in the detection accuracy of the light detection device due to the light incident from the side surface of the light receiving element to the light receiving portion. Further, in the light detection device, the underfill reaches a gap between the light receiving element and the light shielding layer. At this time, since the opening of the frame is narrowed from the first opening edge on the side of the circuit element toward the second opening edge opposite to the circuit element, the underfill reaching a gap between the light receiving element and the light shielding layer easily becomes stable. Thus, it is possible to obtain a stable fixing strength in the entire periphery of the light shielding mask. Furthermore, in the light detection device, the width of the frame increases from the first opening edge on the side of the circuit element toward the second opening edge opposite to the circuit element. Accordingly, the strength of the light shielding mask surrounding the light receiving element increases. Thus, it is possible to protect the light receiving element from an external force. Further, since the light receiving element, the circuit element, and the light shielding mask are fixed together by the underfill which is the same material, these components can be easily and stably fixed. With the above-described configuration, it is possible to obtain the highly reliable light detection device. 
     In the light detection device of the present disclosure, the light receiving element may be in contact with the light shielding layer formed on the inner surface of the opening. Accordingly, since the position of the light shielding mask with respect to the light receiving element becomes stable, the above-described operations and effects more easily achieved. 
     In the light detection device of the present disclosure, the underfill may reach a position in which the light receiving element is in contact with the light shielding layer formed on the inner surface of the opening. Accordingly, it is possible to obtain a more stable fixing strength in the entire periphery of the light shielding mask. Furthermore, it is possible to prevent degradation in the light receiving element due to the intrusion of moisture or the like from the side surface of the light receiving element. 
     In the light detection device of the present disclosure, the plurality of light receiving portions may be arranged along a predetermined direction and the light receiving element and the light shielding mask may have an elongated shape in which the predetermined direction is a longitudinal direction. When the plurality of light receiving portions are arranged along the predetermined direction, the light is easily incident from the side surface of the light receiving element to all light receiving portions and the strength of the light receiving element easily decreases. Thus, when the plurality of light receiving portions are arranged along the predetermined direction, a configuration in which the light shielding mask is provided and the underfill reaches a gap between the light receiving element and the light shielding layer is particularly effective. 
     In the light detection device of the present disclosure, the frame and a substrate of the circuit element may be formed of the same material. Accordingly, it is possible to prevent the deformation of at least one of the circuit element and the light shielding mask due to a difference in thermal expansion coefficient between the substrate of the circuit element and the frame of the light shielding mask. 
     In the light detection device of the present disclosure, the frame and the substrate of the circuit element may be formed of silicon. Accordingly, it is possible to prevent the deformation of at least one of the circuit element and the light shielding mask due to a difference in thermal expansion coefficient between the substrate of the circuit element and the frame of the light shielding mask by using versatile materials. 
     In the light detection device of the present disclosure, a substrate of the light receiving element may be formed of a compound semiconductor. When the substrate of the light receiving element is formed of the compound semiconductor, the side surface of the substrate of the light receiving element is easily chipped. Thus, when the substrate of the light receiving element is formed of the compound semiconductor, a configuration in which the light shielding mask is provided and the underfill reaches a gap between the light receiving element and the light shielding layer is particularly effective in order to suppress the chipping of the side surface of the substrate of the light receiving element. Furthermore, when the substrate of the light receiving element is formed of the compound semiconductor, the chipping or the like occurs on the side surface of the substrate of the light receiving element at the time of manufacturing the light detection device in many cases. For this reason, when stray light is incident, the uniformity among the plurality of light receiving portions is easily degraded due to the irregular reflection or the like. Thus, when the substrate of the light receiving element is formed of the compound semiconductor, a configuration in which the light shielding mask is provided and the underfill reaches a gap between the light receiving element and the light shielding layer is particularly effective in order to ensure the uniformity among the plurality of light receiving portions. 
     In the light detection device of the present disclosure, the light shielding layer may be formed on a surface on the side of the circuit element in the frame. Accordingly, it is possible to prevent, for example, a problem in which the light incident to the circuit element through the surface on the side of the circuit element in the frame is scattered and is incident to the light receiving portion of the light receiving element. 
     In the light detection device of the present disclosure, the underfill may reach a portion in which a surface on the light incident side in the light receiving element intersects a side surface of the light receiving element. Accordingly, since it is possible to cover the side surface of the light receiving element, it is possible to stably fix the light receiving element. Furthermore, it is possible to more reliably suppress the intrusion of moisture onto the mounting surface of the light receiving element. 
     In the light detection device of the present disclosure, the underfill may reach an outer edge of the surface on the light incident side in the light receiving element. Accordingly, since it is possible to cover the intersection portion between the surface on the light incident side in the light receiving element and the side surface of the light receiving element, it is possible to more stably fix the light receiving element. Furthermore, it is possible to more reliably suppress the intrusion of moisture onto the mounting surface of the light receiving element. 
     In the light detection device of the present disclosure, at least one end portion of the second opening edge in the predetermined direction may be located at the outside of at least one end portion of the outer edge of the light receiving element in the predetermined direction when viewed from the light incident direction. Accordingly, a portion between one end portion of the light receiving element in the predetermined direction and one end portion of the light shielding mask in the predetermined direction can serve as an underfill resin releasing hole at the time of manufacturing the light detection device and can suppress an extra underfill from protruding from the surface on the light incident side in the light receiving element in the manufactured light detection device. 
     A light detection device of the present disclosure includes: a light receiving element unit including a plurality of back-illuminated light receiving elements respectively including a plurality of light receiving portions; a circuit element; a connection member disposed between the light receiving element unit and the circuit element and configured to electrically and physically connect the light receiving element unit and the circuit element to each other; an underfill disposed between the light receiving element unit and the circuit element; and a frame-shaped light shielding mask disposed on the circuit element to surround the light receiving element unit when viewed from a light incident direction to the light receiving element unit, in which the light shielding mask includes a frame having an opening in which the light receiving element unit is located and a light shielding layer formed on an inner surface of the opening, in which a first opening edge on the side of the circuit element in the opening is located at the outside of an outer edge of the light receiving element unit when viewed from the light incident direction, in which a second opening edge opposite to the circuit element in the opening is located at the inside of the outer edge of the light receiving element unit when viewed from the light incident direction, in which the opening is narrowed from the first opening edge toward the second opening edge, in which a width of the frame increases from the first opening edge toward the second opening edge, and in which the underfill reaches a gap between the light receiving element unit and the light shielding layer formed on the inner surface of the opening. 
     According to the light detection device, the reliability is improved similarly to the above-described light detection device. Further, it is possible to increase the size of the light receiving element unit while suppressing a decrease in yield and a decrease in mechanical strength. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of a light detection device of a first embodiment. 
         FIG.  2    is a plan view of the light detection device illustrated in  FIG.  1   . 
         FIG.  3    is a cross-sectional view of the light detection device taken along a line illustrated in  FIG.  2   . 
         FIG.  4    is an enlarged cross-sectional view of the light detection device illustrated in  FIG.  3   . 
         FIG.  5    is an enlarged cross-sectional view of the light detection device taken along a line V-V illustrated in  FIG.  2   . 
         FIG.  6    is an enlarged cross-sectional view of a light detection device of a comparative example. 
         FIG.  7    is an enlarged cross-sectional view of the light detection device of the comparative example. 
         FIG.  8    is a plan view of a light detection device of a second embodiment. 
         FIG.  9    is a cross-sectional view of the light detection device taken along a line IX-IX illustrated in  FIG.  8   . 
         FIG.  10    is an enlarged cross-sectional view of the light detection device illustrated in  FIG.  9   . 
         FIG.  11    is an enlarged cross-sectional view of a modified example of the light detection device of the second embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the drawings. Additionally, in drawings, the same reference numerals will be given to the same or equivalent components and a repetitive description thereof will be omitted. 
     First Embodiment 
     As illustrated in  FIGS.  1 ,  2 , and  3   , a light detection device  1 A of a first embodiment includes a light receiving element  10 , a circuit element  20 , a plurality of bumps (connection members)  30 , an underfill  40 , and a light shielding mask  50 . Hereinafter, a light incident direction to the light receiving element  10  will be referred to as a Z-axis direction, a direction perpendicular to the Z-axis direction will be referred to as an X-axis direction, and a direction perpendicular to the Z-axis direction and the X-axis direction will be referred to as a Y-axis direction. 
     The light receiving element  10  includes a substrate  11  which is formed of a compound semiconductor such as InGaAs. The substrate  11  includes a principal surface  11   a  and a principal surface  11   b  which face each other in the Z-axis direction. A portion along the principal surface  11   a  of the substrate  11  is provided with a plurality of light receiving portions  12 . The plurality of light receiving portions  12  are arranged in one dimension along the X-axis direction (a predetermined direction). Each of the light receiving portions  12  is, for example, a photodiode in which a second conductive region is formed in a portion along the principal surface  11   a  of the first conductive substrate  11 . The light receiving element  10  receives the light incident from the principal surface  11   b  of the substrate  11  by each light receiving portion  12 . That is, the light receiving element  10  is a back-illuminated light receiving element. The light receiving element  10  is formed in an elongated shape in which the X-axis direction is a longitudinal direction. As an example, the light receiving element  10  is formed in a rectangular plate shape in which the X-axis direction is a longitudinal direction and the length in the X-axis direction, the width in the Y-axis direction, and the thickness in the Z-axis direction are respectively 13.18 mm, 0.7 mm, and 0.3 mm. 
     The circuit element  20  includes a substrate  21  formed of silicon. The substrate  21  is provided with a signal readout circuit, a signal processing circuit, a signal output circuit, and the like. The substrate  21  includes a principal surface  21   a  on which the light receiving element  10  is mounted. The circuit element  20  processes an electric signal output from each light receiving portion  12  of the light receiving element  10  in response to the light receiving amount. The circuit element  20  is, for example, a CMOS readout circuit (ROIC: readout integrated circuit). 
     The plurality of bumps  30  are disposed between the light receiving element  10  and the circuit element  20 . The plurality of bumps  30  electrically and physically connect the light receiving element  10  and the circuit element  20  to each other between the principal surface  11   a  of the substrate  11  and the principal surface  21   a  of the substrate  21  facing each other in the Z-axis direction. More specifically, the principal surface  11   a  of the substrate  11  and the principal surface  21   a  of the substrate  21  are respectively provided with a plurality of electrode pads (not illustrated) and each bump  30  electrically and physically connects the electrode pads facing each other in the Z-axis direction. Each bump  30  is, for example, an In bump. 
     The underfill  40  is disposed between at least the light receiving element  10  and the circuit element  20 . The underfill  40  is formed of an epoxy-based resin, a urethane-based resin, a silicone-based resin, an acrylic-based resin, a composite resin thereof, or the like. The underfill  40  is filled in a region between the light receiving element  10  and the circuit element  20  and seals the plurality of bumps  30  and the plurality of electrode pads. In the light detection device  1 A, it is possible to protect each bump  30 , ensure an insulation property between the adjacent bumps  30 , and ensure a fixing strength between the light receiving element  10  and the circuit element  20  by the underfill  40 . 
     The light shielding mask  50  is formed in a frame shape and is disposed on the circuit element  20  (specifically, the principal surface  21   a  of the substrate  21 ) to surround the light receiving element  10  when viewed from the Z-axis direction. The light shielding mask  50  is formed in an elongated shape in which the X-axis direction is a longitudinal direction. The light shielding mask  50  includes a frame  52  provided with an opening  51  and a light shielding layer  53 . 
     The light receiving element  10  is located at the inside of the opening  51 . That is, the light receiving element  10  is located between a first opening edge  51   a  and a second opening edge  51   b . The first opening edge  51   a  is the opening edge on the side of the circuit element  20  in the opening  51  and the second opening edge  51   b  is the opening edge opposite to the circuit element  20  in the opening  51 . The first opening edge  51   a  is located at the outside of the outer edge  10   a  of the light receiving element  10  when viewed from the Z-axis direction and the second opening edge  51   b  is located at the inside of the outer edge  10   a  of the light receiving element  10  when viewed from the Z-axis direction (see  FIG.  2   ). Additionally, the side surface  11   c  of the substrate  11  corresponds to the outer edge  10   a  of the light receiving element  10  when viewed from the Z-axis direction. 
     As illustrated in  FIGS.  3 ,  4 , and  5   , the frame  52  is formed in a frame shape by silicon. The frame  52  includes a surface  52   a  and a surface  52   b  which are perpendicular to the Z-axis direction and includes a side surface  52   c  which is parallel to the Z axis. The opening  51  opens to the surface  52   a  on the side of the circuit element  20  and the surface  52   b  opposite to the circuit element  20 . The opening  51  is narrowed from the first opening edge  51   a  toward the second opening edge  51   b  and the width W of the frame  52  increases from the first opening edge  51   a  toward the second opening edge  51   b . An inclination angle of the inner surface  51   c  of the opening  51  (an angle formed between the surface  52   b  of the frame  52  and the inner surface  51   c  of the opening  51 ) is an angle equal to or larger than 30° and equal to or smaller than 60° (in the light detection device  1 A, 54.7°). Here, the width W of the frame  52  is the “width in a direction perpendicular to the extension direction” of the “extension portion formed to surround the opening  51  (one side portion with respect to the opening  51 )” when viewed from the Z-axis direction (that is, the light incident direction to the light receiving element  10 ). 
     An example of the shape of the frame  52  is as follows. The frame  52  is formed in a rectangular frame shape in which the X-axis direction is a longitudinal direction and the length in the X-axis direction, the width in the Y-axis direction, and the thickness in the Z-axis direction are respectively 15 mm, 2 mm, and 0.32 mm. The opening  51  is formed in a truncated pyramid shape. The first opening edge  51   a  is formed in a rectangular shape in which the X-axis direction is a longitudinal direction and the length in the X-axis direction and the width in the Y-axis direction are respectively 13.56 mm and 1.08 mm. Then, the second opening edge  51   b  is formed in a rectangular shape in which the X-axis direction is a longitudinal direction and the length in the X-axis direction and the width in the Y-axis direction are respectively 13.11 mm and 0.63 mm. The frame  52  having such a shape can be obtained, for example, by performing alkali etching on a single crystal silicon substrate. 
     The light shielding layer  53  is formed on the inner surface  51   c  of the opening  51  and the surface  52   a  of the frame  52 . That is, the light shielding layer  53  is integrally formed by including a first portion  53   a  formed on the inner surface  51   c  of the opening  51  and a second portion  53   b  formed on the surface  52   a  of the frame  52 . A portion along the second opening edge  51   b  opposite to the circuit element  20  in the light shielding layer  53  protrudes on the outer edge portion of the light receiving element  10  (specifically, on the outer edge portion of the principal surface  11   b  of the substrate  11 ). The light shielding layer  53  is formed of metal such as Al. The thickness of the light shielding layer  53  may be a thickness in which stray light can be sufficiently reflected and is, for example, 1 μm. The light shielding layer  53  can be obtained, for example, by depositing metal on the inner surface  51   c  of the opening  51  and the surface  52   a  of the frame  52 . Additionally, it is desirable that the thickness of the light shielding layer  53  formed on the surface  52   a  of the frame  52  is larger than the thickness of the light shielding layer  53  formed on the inner surface  51   c  of the opening  51 . In that case, it is desirable that the thickness of the light shielding layer  53  formed on the inner surface  51   c  of the opening  51  decreases from the first opening edge  51   a  toward the second opening edge  51   b . In this way, when the thickness of the light shielding layer  53  formed on the surface  52   a  of the frame  52  is set to be large, it is possible to cover the corner portion of the first opening edge  51   a  by the light shielding layer  53  having a sufficient thickness and to prevent a problem in which the thickness of the light shielding layer  53  formed on the inner surface  51   c  of the opening  51  increases more than necessary (that is, an unnecessary material may not be used to form the light shielding layer  53 ). 
     The light receiving element  10  is in contact with the light shielding layer  53  formed on the inner surface  51   c  of the opening  51  (that is, the first portion  53   a  of the light shielding layer  53 ). More specifically, a corner portion  11   d  which is an intersection line between the side surface  11   c  of the substrate  11  and the principal surface  11   b  of the substrate  11  in the light receiving element  10  is in contact with the first portion  53   a  of the light shielding layer  53 . The underfill  40  reaches a gap between the light receiving element  10  (specifically, the side surface  11   c  of the substrate  11 ) and the first portion  53   a  of the light shielding layer  53  and reaches a position in which the light receiving element  10  is in contact with the first portion  53   a  of the light shielding layer  53 . That is, the underfill  40  is filled in a region between the light receiving element  10  and the first portion  53   a  of the light shielding layer  53 . Furthermore, the underfill  40  is formed on the surface  52   a  of the frame  52  and reaches a gap between the light shielding layer  53  (that is, the second portion  53   b  of the light shielding layer  53 ) and the principal surface  21   a  of the substrate  21  of the circuit element  20  to fill the gap. In this way, the underfill  40  is integrally formed by including a first portion  41  which is disposed between the light receiving element  10  and the circuit element  20 , a second portion  42  which is disposed between the light receiving element  10  and the first portion  53   a  of the light shielding layer  53 , and a third portion  43  which is disposed between the circuit element  20  and the light shielding mask  50 . 
     Additionally, the light detection device  1 A is manufactured as follows. First, the light receiving elements  10  are mounted onto the circuit element  20  by the plurality of bumps  30 . Next, an underfill resin is coated in the periphery of the light receiving element  10 . Next, the light shielding mask  50  is mounted on the circuit element  20  to cover the light receiving element  10 . At this time, since the light receiving element  10  is in contact with the first portion  53   a  of the light shielding layer  53 , the light shielding mask  50  is appropriately positioned to the light receiving element  10 . Then, in this state, the underfill resin spreads in a region between the light receiving element  10  and the circuit element  20 , a region between the light receiving element  10  and the first portion  53   a  of the light shielding layer  53 , and a region between the circuit element  20  and the second portion  53   b  of the light shielding layer  53 . Meanwhile, since the opening  51  is narrowed from the first opening edge  51   a  toward the second opening edge  51   b  and the light receiving element  10  is in contact with the first portion  53   a  of the light shielding layer  53 , it is possible to suppress the leakage of the underfill resin onto the principal surface  11   b  of the substrate  11  of the light receiving element  10 . Even when the underfill resin reaches the principal surface  11   b  of the substrate  11  beyond the corner portion  11   d  of the substrate  11 , the underfill resin easily stays along the second opening edge  51   b  (that is, the underfill resin easily remains on the outer edge portion of the principal surface  11   b ) since the second opening edge  51   b  is located at the inside of the outer edge  10   a  of the light receiving element  10 . As a result, it is possible to suppress the leakage of the underfill resin to the regions on the plurality of light receiving portions  12  of the principal surface  11   b . Next, the underfill resin is thermally cured so that the light shielding mask  50  is fixed by the underfill  40 , thereby obtaining the light detection device  1 A. 
     As described above, in the light detection device  1 A, the light receiving element  10  is located at the inside of the opening  51  of the frame  52  and the light shielding layer  53  is formed on the inner surface  51   c  of the opening  51  of the frame  52 . Further, the opening  51  of the frame  52  is narrowed from the first opening edge  51   a  on the side of the circuit element  20  toward the second opening edge  51   b  opposite to the circuit element  20 . Accordingly, even when light (stray light) is incident from the outside of the opening  51  of the frame  52  into the light shielding layer  53 , the light is easily reflected to, for example, the opposite side to the light receiving element  10 . Thus, it is possible to prevent degradation in the detection accuracy of the light detection device  1 A when the light is incident from the side surface of the light receiving element  10  (in the light detection device  1 A, the side surface  11   c  of the substrate  11 ) to the light receiving portion  12 . Further, in the light detection device  1 A, the underfill  40  reaches a gap between the light receiving element  10  and the light shielding layer  53 . At this time, since the opening  51  of the frame  52  is narrowed from the first opening edge  51   a  on the side of the circuit element  20  toward the second opening edge  51   b  opposite to the circuit element  20 , the underfill  40  reaching a gap between the light receiving element  10  and the light shielding layer  53  easily becomes stable. Thus, it is possible to obtain a stable fixing strength in the entire periphery of the light shielding mask  50 . Furthermore, in the light detection device  1 A, the width W of the frame  52  increases from the first opening edge  51   a  on the side of the circuit element  20  toward the second opening edge  51   b  opposite to the circuit element  20 . Accordingly, the strength of the light shielding mask  50  surrounding the light receiving element  10  increases. Thus, it is possible to protect the light receiving element  10  from an external force. Further, since the light receiving element  10 , the circuit element  20 , and the light shielding mask  50  are fixed together by the underfill  40  which is the same material, these components can be easily and stably fixed. Accordingly, it is possible to obtain the highly reliable light detection device  1 A. The configuration of the light detection device  1 A is extremely effective when the light detection device  1 A is configured as a wafer level chip size package (CSP). 
     For example, the amount of the underfill  40  reaching each side surface of the light receiving element  10  differs due to the side surface of the light receiving element  10  or differs due to a position within one side surface unless a method of highly accurately disposing light shielding plates and preventing the leakage of the underfill  40  from a gap between the adjacent light shielding plates even when the plurality of light shielding plates are disposed to respectively face the plurality of side surfaces of the light receiving elements  10 . In such a configuration, a high-strength portion and a low-strength portion are generated and hence breakage easily occurs from the low-strength portion. In contrast, in the light detection device  1 A of the above-described first embodiment, since the frame-shaped light shielding mask  50  is disposed to surround the light receiving element  10 , the amount of the underfill  40  reaching each side surface of the light receiving element  10  becomes uniform in any position of each side surface of the light receiving element  10 . Thus, in the light detection device  1 A of the above-described first embodiment, uniform strength is obtained and hence breakage is suppressed. 
     Further, in the light detection device  1 A, the light receiving element  10  is in contact with the light shielding layer  53  formed on the inner surface  51   c  of the opening  51  (that is, the first portion  53   a  of the light shielding layer  53 ). Accordingly, since the position of the light shielding mask  50  with respect to the light receiving element  10  becomes stable, the above-described operations and effects more easily achieved. 
     Further, in the light detection device  1 A, the underfill  40  reaches a position in which the light receiving element  10  is in contact with the light shielding layer  53  formed on the inner surface  51   c  of the opening  51  (that is, the first portion  53   a  of the light shielding layer  53 ). Accordingly, it is possible to obtain a stable fixing strength in the entire periphery of the light shielding mask  50 . Furthermore, it is possible to prevent degradation in the light receiving element  10  due to the intrusion of moisture or the like from the side surface of the light receiving element  10 . 
     Further, in the light detection device  1 A, the plurality of light receiving portions  12  are arranged along a predetermined direction (in the light detection device  1 A, the X-axis direction) and the light receiving element  10  and the light shielding mask  50  are formed in an elongated shape in which the predetermined direction is a longitudinal direction. When the plurality of light receiving portions  12  are arranged along the predetermined direction, the light is easily incident from the side surfaces of the light receiving elements  10  to all light receiving portions  12  and the strength of the light receiving elements  10  easily decrease. Thus, when the plurality of light receiving portions  12  are arranged along the predetermined direction, a configuration in which the light shielding mask  50  is provided and the underfill  40  reaches a gap between the light receiving element  10  and the light shielding layer  53  is particularly effective. 
     Further, in the light detection device  1 A, the substrate  21  of the circuit element  20  and the frame  52  of the light shielding mask  50  are formed of silicon. Accordingly, it is possible to prevent the deformation of at least one of the circuit element  20  and the light shielding mask  50  due to a difference in thermal expansion coefficient between the substrate  21  of the circuit element  20  and the frame  52  of the light shielding mask  50 . 
     Further, in the light detection device  1 A, the substrate  11  of the light receiving element  10  is formed of a compound semiconductor. When the substrate  11  of the light receiving element  10  is formed of the compound semiconductor, the side surface  11   c  of the substrate  11  of the light receiving element  10  is easily chipped. Thus, when the substrate  11  of the light receiving element  10  is formed of the compound semiconductor, a configuration in which the light shielding mask  50  is provided and the underfill  40  reaches a gap between the light receiving element  10  and the light shielding layer  53  is particularly effective in order to suppress the chipping of the side surface  11   c  of the substrate  11  of the light receiving element  10 . Furthermore, when the substrate  11  of the light receiving element  10  is formed of the compound semiconductor, the chipping or the like occurs on the side surface  11   c  of the substrate  11  of the light receiving element  10  at the time of manufacturing the light detection device in many cases. For this reason, when stray light is incident, the uniformity among the plurality of light receiving portions  12  is easily degraded due to the irregular reflection or the like. However, since the light shielding mask  50  is provided, the second opening edge  51   b  of the light shielding mask  50  is located at the inside in relation to the outer edge  10   a  of the light receiving element  10 . For this reason, since the outer edge  10   a  of the light receiving element  10  is covered when viewed from the light incident direction, it is possible to suppress degradation in the uniformity among the plurality of light receiving portions  12  caused by the incident stray light. Thus, when the substrate  11  of the light receiving element  10  is formed of the compound semiconductor, a configuration in which the light shielding mask  50  is provided and the underfill  40  reaches a gap between the light receiving element  10  and the light shielding layer  53  is particularly effective in order to ensure the uniformity among the plurality of light receiving portions  12 . Of course, such an effect is effective even when the substrate  11  of the light receiving element  10  is formed of a semiconductor (for example, silicon) other than the compound semiconductor. 
     Further, in the light detection device  1 A, the light shielding layer  53  is formed on the surface  52   a  on the side of the circuit element  20  in the frame  52  in addition to the inner surface  51   c  of the opening  51 . Accordingly, it is possible to prevent, for example, a problem in which the light incident to the circuit element  20  through the surface  52   a  on the side of the circuit element  20  in the frame  52  is scattered and is incident to the light receiving portion  12  of the light receiving element  10 . 
     Further, in the light detection device  1 A, the inclination angle of the inner surface  51   c  of the opening  51  is an angle equal to or larger than 30° and equal to or smaller than 60°. When the inclination angle is within this angle range, it is possible to sufficiently increase particularly the strength of the light shielding mask  50  and to appropriately control the raising of the underfill  40 . Additionally, even when the inclination angle is an angle other than this angle range, such an effect is obtained. 
     Further, in the light detection device  1 A, the underfill  40  reaches an intersection portion (in the light detection device  1 A, the corner portion  11   d ) between the side surface of the light receiving element  10  (in the light detection device  1 A, the side surface  11   c ) and the surface (in the light detection device  1 A, the principal surface  11   b ) on the light incident side in the light receiving element  10 . Furthermore, in the light detection device  1 A, the underfill  40  reaches the outer edge of the surface on the light incident side in the light receiving element  19 . Accordingly, since it is possible to cover the intersection portion between the surface on the light incident side in the light receiving element  10  and the side surface of the light receiving element  10  as well as the side surface of the light receiving element  10 , it is possible to more stably fix the light receiving element  10 . Furthermore, it is possible to more reliably suppress the intrusion of moisture onto the mounting surface of the light receiving element  10 . 
       FIG.  6    is an enlarged cross-sectional view of a light detection device of a comparative example and illustrates a portion corresponding to  FIG.  4   .  FIG.  7    is an enlarged cross-sectional view of the light detection device of the comparative example and illustrates a portion corresponding to  FIG.  5   . The light detection device of the comparative example illustrated in  FIGS.  6  and  7    is chiefly different from the light detection device  1 A of the above-described first embodiment in that the light shielding mask  50  is not provided. In the light detection device of the comparative example, the underfill  40  is raised on the side surface  11   c  of the substrate  11  in the periphery of the light receiving element  10 . For this reason, the following problem can be generated. 
     As illustrated in  FIG.  6   , when light is incident to a portion  44  located at both sides of the light receiving element  10  in the X-axis direction in the underfill  40 , there is concern that the light is refracted on the surface of the portion  44  and the boundary face between the portion  44  and the side surface  11   c  of the substrate  11  and is incident from the side surface  11   c  of the substrate  11  to the light receiving portions  12  of both ends. In this case, since noise light is detected by the light receiving portions  12  of both ends, the uniformity among the plurality of light receiving portions  12  arranged in one dimension along the X-axis direction is degraded. This is a problem peculiar to the back-illuminated light receiving element  10 . 
     Further, as illustrated in  FIG.  7   , when light is incident to the portions  44  located at both sides of the light receiving element  10  in the Y-axis direction of the underfill  40 , there is concern that the light is refracted on the surface of the portion  44  and the boundary face between the portion  44  and the side surface  11   c  of the substrate  11  and is incident from the side surface  11   c  of the substrate  11  to the light receiving portion  12 . Such a phenomenon can be generated in all of the plurality of light receiving portions  12  arranged in one dimension along the X-axis direction. In this case, when an object is relatively moved along the Y-axis direction to acquire a two-dimensional image of the object, a ghost image appears at the front and rear sides in a direction corresponding to the Y-axis direction with respect to the image of the object. This is a problem peculiar to the back-illuminated light receiving element  10 . 
     Compared to the light detection device of the comparative example, the light detection device  1 A of the above-described first embodiment includes the light shielding mask  50 . For this reason, according to the light detection device  1 A of the above-described first embodiment, it is possible to solve degradation in uniformity and the appearance of the ghost image (the problem peculiar to the back-illuminated light receiving element  10 ). 
     Second Embodiment 
     As illustrated in  FIGS.  8  and  9   , a light detection device  1 B of a second embodiment is different from the light detection device  1 A of the first embodiment in that a light receiving element unit  100  includes the plurality of light receiving elements  10  and a part of the second opening edge  51   b  of the light shielding mask  50  is located at the outside of an outer edge  100   a  of the light receiving element unit  100 . Except for these differences, one light receiving element  10  of the light detection device  1 A of the first embodiment can be read as the light receiving element unit  100  of the light detection device  1 B of the second embodiment. Thus, according to the light detection device  1 B of the second embodiment, the same operations and effects as those of the light detection device  1 A of the first embodiment are obtained. Hereinafter, the above-described differences will be described in detail. 
     In the light detection device  1 B, two light receiving elements  10  are arranged in one dimension along the X-axis direction. A portion along the principal surface  11   a  of the substrate  11  of each light receiving element  10  is provided with a plurality of light receiving portions  12 . The plurality of light receiving portions  12  are arranged in one dimension along the X-axis direction. Each light receiving element  10  is formed in an elongated shape in which the X-axis direction is the longitudinal direction. As an example, each light receiving element  10  is formed in a rectangular plate shape in which the X-axis direction is the longitudinal direction. In this way, each light receiving element  10  is a one-dimensional image sensor and two light receiving elements  10  are arranged in parallel in a direction in which a plurality of light receiving portions  12  serving as a plurality of pixels are arranged. Furthermore, for example, a gap of about 5 μm is formed between the adjacent light receiving elements  10  and the underfill  40  enters the gap. That is, the underfill  40  is disposed between the adjacent light receiving elements  10 . In each light receiving element  10 , the light receiving portion  12  closest to the gap is set as a dummy and an electric signal output from the light receiving portion  12  may not be used to generate an image. 
     When viewed from the Z-axis direction, both end portions of the second opening edge  51   b  of the light shielding mask  50  in the X-axis direction are located at the outside of both end portions of the outer edge  100   a  of the light receiving element unit  100  in the X-axis direction. Accordingly, a portion between one end portion of the light receiving element unit  100  in the X-axis direction and one end portion of the light shielding mask  50  in the X-axis direction and a portion between the other end portion of the light receiving element unit  100  in the X-axis direction and the other end portion of the light shielding mask  50  in the X-axis direction can serve as an underfill releasing hole at the time of manufacturing the light detection device  1 B and can suppress an extra underfill  40  from protruding from the surface on the light incident side in each light receiving element  10  in the manufactured light detection device  1 B. Furthermore, the outer edge  100   a  of the light receiving element unit  100  when viewed from the Z-axis direction is defined by an outer portion excluding the adjacent inner portions in the outer edges  10   a  of the light receiving elements  10  when viewed from the Z-axis direction. 
     As an example, a pair of sides  54  facing each other in the Y-axis direction of the second opening edge  51   b  is located at the inside of a pair of sides  14  facing each other in the Y-axis direction of the outer edge  100   a  of the light receiving element unit  100  when viewed from the Z-axis direction. Meanwhile, a pair of sides  55  facing each other in the X-axis direction of the second opening edge  51   b  is located at the outside of a pair of sides  15  facing each other in the X-axis direction of the outer edge  100   a  of the light receiving element unit  100  when viewed from the Z-axis direction. 
     As illustrated in  FIG.  10   , in both end portions of the light shielding mask  50  in the X-axis direction, the second portion  42  of the underfill  40  creeps up on the side surface  11   c  of the substrate  11  and the surface of the first portion  53   a  of the light shielding layer  53 . The second portion  42  which creeps up on the side surface  11   c  of the substrate  11  reaches the corner portion  11   d  of the substrate  11 . A groove-shaped concave portion is formed between the second portion  42  creeping up on the side surface  11   c  of the substrate  11  and the second portion  42  creeping up on the surface of the first portion  53   a  of the light shielding layer  53 . When the underfill resin creeps up on the surface of the first portion  53   a  of the light shielding layer  53  at the time of manufacturing the light detection device  1 B, it is possible to more reliably suppress an extra underfill  40  from protruding from the surface on the light incident side in each light receiving element  10  in the manufactured light detection device  1 B. However, there is a case in which the second portion  42  of the underfill  40  creeps up on the side surface  11   c  of the substrate  11  and the surface of the first portion  53   a  of the light shielding layer  53  and a groove-shaped concave portion is not formed between the second portion  42  creeping up on the side surface  11   c  of the substrate  11  and the second portion  42  creeping up on the surface of the first portion  53   a  of the light shielding layer  53 . Further, there is a case in which the second portion  42  of the underfill  40  creeps up on the side surface  11   c  of the substrate  11  and does not creep up on the surface of the first portion  53   a  of the light shielding layer  53 . 
     As illustrated in  FIG.  8   , each of a pair of sides  56  facing each other in the X-axis direction of the first opening edge  51   a  of the light shielding mask  50  is separated from each of the pair of sides  15  facing each other in the X-axis direction of the outer edge  100   a  of the light receiving element unit  100  by a distance D when viewed from the Z-axis direction. As illustrated in  FIG.  10   , when the distance D is smaller than 200 μm, it is possible to suppress light from being incident from the side surface  11   c  of the substrate  11  into the light receiving portions  12  of both ends. As a result, it is possible to suppress deterioration in uniformity between the plurality of light receiving portions  12  arranged in one dimension along the X-axis direction. 
     Meanwhile, as illustrated in  FIG.  11   , when the distance D is equal to or larger than 200 μm, it is possible to reliably exhibit the function of the underfill resin releasing hole at the time of manufacturing the light detection device  1 B and to more reliably suppress an extra underfill  40  from protruding from the surface on the light incident side in each light receiving element  10  in the manufactured light detection device  1 B. Furthermore, in any one of the cases of  FIGS.  10  and  11   , the light receiving portions  12  of both ends in the X-axis direction of each light receiving element  10  are set as a dummy and an electric signal output from the light receiving portion  12  may not be used to generate an image. 
     Modified Example 
     The present disclosure is not limited to the above-described first and second embodiments. For example, the materials and shapes of components are not limited to the above-described materials and shapes and various materials and shapes can be employed. As an example, the material of the substrate  11  of the light receiving element  10  is not limited to the compound semiconductor such as InGaAs and may be silicon or the like. Further, the substrate  21  of the circuit element  20  and the frame  52  of the light shielding mask  50  may be formed of a material (for example, resin, ceramic, or the like) other than silicon. Here, when the substrate  21  of the circuit element  20  and the frame  52  of the light shielding mask  50  are formed of the same material, it is possible to prevent the deformation of at least one of the circuit element  20  and the light shielding mask  50  due to a difference in thermal expansion coefficient between the substrate  21  of the circuit element  20  and the frame  52  of the light shielding mask  50 . 
     Further, the inclination angle of the inner surface Mc of the opening  51  does not need to be uniform and the inclination angle may decrease or increase, for example, from the first opening edge  51   a  toward the second opening edge  51   b . For example, when the inner surface  51   c  of the opening  51  is a concave curved surface in a cross-section parallel to the Z-axis direction, the inclination angle decreases from the first opening edge  51   a  toward the second opening edge  51   b . For example, when the inner surface  51   c  of the opening  51  is a convex curved surface in a cross-section parallel to the Z-axis direction, the inclination angle increases from the first opening edge  51   a  toward the second opening edge  51   b . Further, the shape of the opening  51  may be, for example, a shape obtained by the combination of the vertical hole and the tapered hole. That is, the opening  51  which is narrowed from the first opening edge  51   a  toward the second opening edge  51   b  may be formed so that a partially uniform portion exists or a partially enlarged portion exists as long as the opening is narrowed on the whole. Here, when the opening  51  is continuously narrowed from the first opening edge  51   a  toward the second opening edge  51   b , it is possible to allow an appropriate amount of the underfill  40  to flow between the light receiving element  10  and the first portion  53   a  of the light shielding layer  53  while ensuring the mechanical strength of the light shielding mask  50 . Furthermore, since there is no unnecessary portion in the shape of the opening  51 , it is possible to realize a decrease in size of the light detection devices  1 A and  1 B. 
     Further, when the width W of the frame  52  increases from the first opening edge  51   a  toward the second opening edge  51   b  on the whole, a partially uniform portion may exist or a partially narrowed portion may exist. Here, when the width W of the frame  52  continuously increases from the first opening edge  51   a  toward the second opening edge  51   b , it is possible to decrease the size of the light detection devices  1 A and  1 B while ensuring the mechanical strength of the light shielding mask  50 . Further, the width W of the frame  52  does not need to be uniform in all portions and the width W of the frame  52  illustrated in  FIG.  4    and the width W of the frame  52  illustrated in  FIG.  5    may be the same or different. 
     Further, in the light detection devices  1 A and  1 B of the above-described first and second embodiments, the underfill  40  may not reach a region between the circuit element  20  and the second portion  53   b  of the light shielding layer  53  (that is, the light shielding layer  53  formed on the surface  52   a  of the frame  52 ). Further, the light shielding layer  53  may not be formed on the surface  52   a  of the frame  52  as long as the light shielding layer is formed on the inner surface  51   c  of the opening  51 . Also in such a case, it is possible to obtain the same operations and effects as those of the light detection devices  1 A and  1 B of the above-described first and second embodiments. 
     In the light detection devices  1 A and  1 B of the above-described first and second embodiments, the light receiving element  10  is in contact with the first portion  53   a  of the light shielding layer  53  and the bottom surface of the light shielding mask  50  (the surface  52   a  of the frame  52  or the second portion  53   b  of the light shielding layer  53 ) is separated from the circuit element  20 . However, the light detection devices  1 A and  1 B may have the following configuration. That is, the light receiving element  10  may be separated from the first portion  53   a  of the light shielding layer  53  and the bottom surface of the light shielding mask  50  may be in contact with the circuit element  20 . Alternatively, the light receiving element  10  may be in contact with the first portion  53   a  of the light shielding layer  53  and the bottom surface of the light shielding mask  50  may be in contact with the circuit element  20 . Alternatively, the light receiving element  10  may be separated from the first portion  53   a  of the light shielding layer  53  and the bottom surface of the light shielding mask  50  may be separated from the circuit element  20 . In any case, when the underfill  40  reaches a gap between the light receiving element  10  and the first portion  53   a  of the light shielding layer  53 , the underfill may not reach the outer edge of the surface on the light incident side in the light receiving element  10  and may not reach the intersection portion between the surface on the light incident side in the light receiving element  10  and the side surface of the light receiving element  10 . Further, the underfill  40  may not reach a gap between the bottom surface of the light shielding mask  50  and the circuit element  20 . When the underfill  40  reaches a gap between the light receiving element  10  and the first portion  53   a  of the light shielding layer  53  in a case in which the light receiving element  10  is in contact with the first portion  53   a  of the light shielding layer  53 , the light receiving element  10  may not reach a contact position with the first portion  53   a  of the light shielding layer  53 . That is, the underfill  40  may reach (contact) a gap between at least a part of the side surface of the light receiving element  10  (in the light detection devices  1 A and  1 B, the side surface  11   c  of the substrate  11 ) and at least a part of the first portion  53   a  of the light shielding layer  53 . 
     Additionally, even when the light receiving element  10  is in contact with the first portion  53   a  of the light shielding layer  53 , there is no need to allow the first portion  53   a  of the light shielding layer  53  to contact, for example, the entirety of the corner portion  11   d  of the substrate  11  of the light receiving element  10 . In the present specification, the expression of the “contact” means that at least a part of components physically contact to each other. 
     Further, the light receiving element  10  may have a configuration in which the plurality of light receiving portions  12  are arranged in two dimensions. Further, the light receiving element  10  is not limited to a configuration in which the second conductive region is formed in a portion along the principal surface  11   a  of the first conductive substrate  11 . For example, the second conductive region may be formed in a region along the principal surface  11   a  of the first conductive substrate  11  and the first conductive region may be formed inside the region. That is, the light receiving element  10  may have any configuration as long as the back-illuminated light receiving element is provided. Further, the circuit element  20  may be a member simply provided with a wiring. Further, the circuit element  20  may include a substrate formed of a material other than the semiconductor material. Further, the shape of the circuit element  20  is not limited to the substrate and may have, for example, a shape like a casing with a concave portion. 
     Further, an optical element such as a filter may be mounted on the surface  52   b  of the frame  52 . Further, the light shielding layer  53  is not limited to a layer (a light reflection layer) having a function of reflecting light and may be a layer (a light absorption layer) having a function of absorbing light. For example, when the light shielding layer  53  is formed of indium tin oxide (ITO), antimony tin oxide (ATO), lanthanum hexaboride (LaB 6 ), cesium tungsten oxide, or the like, the light shielding layer  53  may be formed as a light absorption layer. However, it is desirable that the light shielding layer  53  is the light reflection layer from the viewpoint of suppressing the generation of heat. Further, the light receiving element  10  and the circuit element  20  may be electrically and physically connected to each other by, for example, an anisotropic conductive resin layer instead of the bump  30 . In that case, in the anisotropic conductive resin layer, a portion between the electrode pads facing each other in the Z-axis direction serves as a connection member and a portion other than the connection member serves as the underfill  40  (that is, the underfill reaches a gap between the light receiving element  10  and the first portion  53   a  of the light shielding layer  53  as well as a gap between the light receiving element  10  and the circuit element  20 ). 
     Further, the underfill  40  may reach a corner portion formed by the principal surface  21   a  of the substrate  21  of the circuit element  20  and the side surface  52   c  of the frame  52  of the light shielding mask  50  through a region between the circuit element  20  and the light shielding mask  50 . Accordingly, since the fixing of the light shielding mask  50  with respect to the circuit element  20  is reinforced, the stability of the device is improved. 
     Further, in the light detection device  1 A of the first embodiment, all of the second opening edge  51   b  are located at the inside of the outer edge  10   a  of the light receiving element  10  when viewed from the Z-axis direction, but a part of the second opening edge  51   b  may be located at the outside of the outer edge  10   a  of the light receiving element  10  when viewed from the Z-axis direction. That is, at least a part of the second opening edge  51   b  may be located at the inside of the outer edge  10   a  of the light receiving element  10  when viewed from the Z-axis direction. In the light detection device  1 A of the first embodiment, one end portion of the second opening edge  51   b  in the X-axis direction may be located at the outside of one end portion of the outer edge  10   a  of the light receiving element  10  in the X-axis direction when viewed from the Z-axis direction. Accordingly, a portion between one end portion of the light receiving element  10  in the X-axis direction and one end portion of the light shielding mask  50  in the X-axis direction can serve as an underfill resin releasing hole at the time of manufacturing the light detection device  1 A and can suppress an extra underfill  40  from protruding from the surface on the light incident side in the light receiving element  10  in the manufactured light detection device  1 A. Furthermore, considering the stability of the device, both end portions of the second opening edge  51   b  in the X-axis direction are preferably located at the outside of both end portions of the outer edge  10   a  of the light receiving element  10  in the X-axis direction when viewed from the Z-axis direction. 
     Further, in the light detection device  1 B of the second embodiment, the light receiving element unit  100  includes two light receiving elements  10  arranged in one dimension along the X-axis direction, but the light receiving element unit  100  may include a plurality of light receiving elements  10  arranged in one dimension or two dimensions along the surface on the side of the light receiving element unit  100  in the circuit element  20 . Accordingly, it is possible to increase the size of the light receiving element unit  100  while suppressing a decrease in yield and a decrease in mechanical strength. Furthermore, also in that case, each light receiving element  10  may have a configuration in which a plurality of light receiving portions  12  are arranged in two dimensions. Further, the plurality of light receiving elements  10  constituting one light receiving element unit  100  may not have the same size. 
     According to the present disclosure, it is possible to provide the highly reliable light detection device.