Abstract:
An infrared detection element is configured to prevent decreases in detection precision when a beam bends. The infrared detection element basically has a substrate structure, a light receiver configured and arranged to receive infrared rays and at least one beam having one end fixed to the substrate and another end fixed to the light receiver to support the light receiver above the substrate. At least one protuberance is provided on at least one of the substrate, the light receiver and the beam with the at least one protuberance being configured and arranged to limit direct contact between any two of the beam, the light receiver and the substrate structure during bending of the beam, except at the at least one protuberance.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims priority to Japanese Patent Application No. 2006-004401, filed on Jan. 12, 2006. The entire disclosure of Japanese Patent Application No. 2006-004401 is hereby incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention generally relates to an infrared detection element. More specifically, the present invention relates to an infrared detection element that is configured to prevent decreases in detection precision when a beam bends.  
         [0004]     2. Background Information  
         [0005]     Thermal infrared detection elements are known in which a light receiver on which an infrared ray absorption band is formed is supported on a hollow substrate by a very small beam, and the temperature of the light receiver is detected by a thermopile or the like (for example, see Unexamined Patent Application Publication No. 2001-281065).  
         [0006]     In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved infrared detection element. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.  
       SUMMARY OF THE INVENTION  
       [0007]     It has been discovered that in thermal infrared detection elements of the above description, a risk arises that the beam will bend and the light receiver or beam will come into contact with the substrate when the detection element is subjected to impact or force, increased speed, or the like. In particular, when the beam is severely bent, a problem arises in that a twisting force is also applied, the light receiver or beam is brought into linear contact with the substrate, and heat dissipates from the light receiver toward the substrate, causing the detection precision to decrease.  
         [0008]     In view of the foregoing problems, the present invention provides an infrared detection element that basically comprises a substrate structure, a light receiver configured and arranged to receive infrared rays and at least one beam having one end fixed to the substrate and another end fixed to the light receiver to support the light receiver above the substrate. At least one protuberance is provided on at least one of the substrate, the light receiver and the beam with the at least one protuberance being configured and arranged to limit direct contact between any two of the beam, the light receiver and the substrate structure during bending of the beam, except at the at least one protuberance.  
         [0009]     These and other objects, features, aspects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     Referring now to the attached drawings which form a part of this original disclosure:  
         [0011]      FIG. 1A  is a simplified top plan view of an infrared detection element in accordance with a first embodiment of the present invention;  
         [0012]      FIG. 1B  is a simplified cross-sectional view of the infrared detection element illustrated in  FIG. 1  as seen along section line  1 - 1  in  FIG. 1A ;  
         [0013]      FIG. 2  is a simplified top plan view of an infrared detection element for describing an infrared detection element that does not include a protuberance;  
         [0014]      FIG. 3A  is a simplified side elevational view showing a first step in manufacturing the infrared detection element of the present invention;  
         [0015]      FIG. 3B  is a simplified side elevational view showing a second step in manufacturing the infrared detection element of the present invention;  
         [0016]      FIG. 4A  is a simplified top plan view showing a third step in manufacturing the infrared detection element of the present invention;  
         [0017]      FIG. 4B  is a simplified cross-sectional view showing the third step in manufacturing the infrared detection element of the present invention;  
         [0018]      FIG. 5A  is a simplified top plan view showing a fourth step in manufacturing the infrared detection element of the present invention;  
         [0019]      FIG. 5B  is a simplified cross-sectional view showing the fourth step in manufacturing the infrared detection element of the present invention as seen along section line  5 - 5  in  FIG. 5A ;  
         [0020]      FIG. 5C  is a simplified cross-sectional view showing a fifth step in manufacturing the infrared detection element of the present invention as seen along section line  5 - 5  in  FIG. 5A ;  
         [0021]      FIG. 6A  is a simplified top plan view showing a sixth step in manufacturing the infrared detection element of the present invention;  
         [0022]      FIG. 6B  is a simplified cross-sectional view showing the sixth step in manufacturing the infrared detection element of the present invention as seen along section line  6 - 6  in  FIG. 6A ;  
         [0023]      FIG. 7A  is a simplified top plan view showing a seventh step in manufacturing the infrared detection element of the present invention;  
         [0024]      FIG. 7B  is a simplified cross-sectional view showing the seventh step in manufacturing the infrared detection element of the present invention as seen along section line  7 - 7  in  FIG. 7A ;  
         [0025]      FIG. 8  is a simplified top plan view of an infrared detection element in accordance with a first modification of the present invention;  
         [0026]      FIG. 9  is a simplified top plan view of an infrared detection element in accordance with a second modification of the present invention;  
         [0027]      FIG. 10A  is a simplified top plan view of an infrared detection element in accordance with a third modification of the present invention;  
         [0028]      FIG. 10B  is a simplified cross-sectional view of the infrared detection element in accordance with the third modification of the present invention as seen along section line  10 - 10  in  FIG. 10A ;  
         [0029]      FIG. 11A  is a simplified top plan view of the infrared detection element in accordance with the third modification of the present invention in which the infrared detection element has been subjected to an impact or force to bend the beam;  
         [0030]      FIG. 11B  is a simplified cross-sectional view of the infrared detection element in accordance with the third modification of the present invention as seen along section line  11 - 11  in  FIG. 11A ;  
         [0031]      FIG. 12A  is a simplified top plan view of an infrared detection element in accordance with a fourth modification of the present invention in which the infrared detection element has not been subjected to an impact or force to bend the beam;  
         [0032]      FIG. 12B  is a simplified top plan view of the infrared detection element in accordance with the fourth modification of the present invention in which the infrared detection element has been subjected to an impact or force to bend the beam;  
         [0033]      FIG. 13A  is a simplified top plan view of an infrared detection element in accordance with a fifth modification of the present invention in which the infrared detection element has not been subjected to an impact or force to bend the beam;  
         [0034]      FIG. 13B  is a simplified top plan view of the infrared detection element in accordance with the fifth modification of the present invention in which the infrared detection element has been subjected to an impact or force to bend the beam;  
         [0035]      FIG. 14  is a top plan view of an infrared detection element in accordance with a sixth modification of the present invention;  
         [0036]      FIG. 15A  is a simplified cross-sectional view of the infrared detection element in accordance with the sixth modification of the present invention as seen along section line  15 A- 15 A in  FIG. 14 ;  
         [0037]      FIG. 15B  is a simplified cross-sectional view of the infrared detection element in accordance with the sixth modification of the present invention as seen along section line  15 B- 15 B in  FIG. 14 ;  
         [0038]      FIG. 16A  is a simplified top plan view showing a first step in manufacturing the infrared detection element of the sixth modification of the present invention;  
         [0039]      FIG. 16B  is a simplified cross-sectional view showing the first step in manufacturing the infrared detection element of the sixth modification of the present invention as seen along section line  16 - 16  in  FIG. 16A ;  
         [0040]      FIG. 17A  is a simplified top plan view showing a second step in manufacturing the infrared detection element of the sixth modification of the present invention;  
         [0041]      FIG. 17B  is a simplified cross-sectional view showing the second step in manufacturing the infrared detection element of the sixth modification of the present invention as seen along section line  17 - 17  in  FIG. 17A ;  
         [0042]      FIG. 18A  is a simplified top plan view showing a third step in manufacturing the infrared detection element of the sixth modification of the present invention;  
         [0043]      FIG. 18B  is a simplified cross-sectional view showing the third step in manufacturing the infrared detection element of the sixth modification of the present invention as seen along section line  18 - 18  in  FIG. 18A ;  
         [0044]      FIG. 19A  is a simplified top plan view showing a fourth step in manufacturing the infrared detection element of the sixth modification of the present invention;  
         [0045]      FIG. 19B  is a simplified cross-sectional view showing the fourth step in manufacturing the infrared detection element of the sixth modification of the present invention as seen along section line  19 - 19  in  FIG. 19A ;  
         [0046]      FIG. 20A  is a simplified top plan view showing a fifth step in manufacturing the infrared detection element of the sixth modification of the present invention;  
         [0047]      FIG. 20B  is a simplified cross-sectional view showing the fifth step in manufacturing the infrared detection element of the sixth modification of the present invention as seen along section line  20 - 20  in  FIG. 20A ;  
         [0048]      FIG. 21A  is a simplified top plan view showing a sixth step in manufacturing the infrared detection element of the sixth modification of the present invention;  
         [0049]      FIG. 21B  is a simplified cross-sectional view showing the sixth step in manufacturing the infrared detection element of the sixth modification of the present invention as seen along section line  21 - 21  in  FIG. 21A ;  
         [0050]      FIG. 22A  is a simplified top plan view showing an infrared detection element in accordance with a seventh modification of the present invention;  
         [0051]      FIG. 22B  is a simplified cross-sectional view showing the infrared detection element of the seventh modification of the present invention as seen along section line  22 - 22  in  FIG. 22A ;  
         [0052]      FIG. 23A  is a simplified top plan view showing an eighth step in manufacturing the infrared detection element of the seventh modification of the present invention;  
         [0053]      FIG. 23B  is a simplified cross-sectional view showing the eighth step in manufacturing the infrared detection element of the seventh modification of the present invention as seen along section line  23 - 23  in  FIG. 23A ;  
         [0054]      FIG. 24A  is a simplified cross-sectional view showing a ninth step in manufacturing the infrared detection element of the seventh modification of the present invention as seen along section line  24 B- 24 B in  FIG. 24B ;  
         [0055]      FIG. 24B  is a simplified cross-sectional view showing the ninth step in manufacturing the infrared detection element of the seventh modification of the present invention as seen along section line  24 - 24  in  FIG. 24A ;  
         [0056]      FIG. 25A  is a simplified, enlarged perspective view of a distal end of the protuberance in accordance with one modification of the present invention;  
         [0057]      FIG. 25B  is a simplified, enlarged perspective view of a distal end of the protuberance in accordance with another modification of the present invention;  
         [0058]      FIG. 25C  is a simplified, enlarged perspective view of a distal end of the protuberance in accordance with still another modification of the present invention; and  
         [0059]      FIG. 25D  is a simplified, enlarged perspective view of a distal end of the protuberance in accordance with yet still another modification of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0060]     Selected embodiments of the present invention will now be explained with reference to the drawings. It will be apparent to those skilled in the art from this disclosure that the following descriptions of the embodiments of the present invention are provided for illustration only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents. In view of the following embodiments, the parts of the embodiment that are identical to the parts will be given the same reference numerals.  
         [0061]     Referring initially to  FIGS. 1A and 1B , an infrared detection element is illustrated in accordance with a first embodiment of the present invention.  FIG. 1A  is a simplified top plan view of the infrared detection element, while  FIG. 1B  is a simplified cross-sectional view of the infrared detection element. Basically, the infrared detection element of the illustrated embodiment includes a silicon (Si) substrate  1 , a frame  2 , a light receiver  3  and a pair of substantially L-shaped beams  4  supporting the light receiver  3  on the frame  2 . Thus, an end of each of the beams  4  is connected to the frame  2 , while the other end of each of the beams  4  is connected to the light receiver  3 . In  FIG. 1A , a portion of the light receiver  3  and the beams  4  are shown in section in order to better understand the inner structure of the light receiver  3  and the beams  4 . The silicon (Si) substrate  1  and the frame form a substrate structure that supports the light receiver  3  by the beams  4 .  
         [0062]     A concavity  1   a  is etched into the substrate  1 . The light receiver  3  and the beams  4  are located along an upper part of the concavity  1   a . The concavity  1   a  can also be a through hole. Thus, the concavity can also be referred to as a substrate space that generically refers to both a concavity and a through hole. Also a cavity  11  is formed in the substrate  1  to form a space between the light receiver  3  and the substrate  1  and a space between the beams  4  and the substrate  1 .  
         [0063]     As seen in  FIG. 1B , the frame  2 , the light receiver  3 , and the beams  4  are formed of a multi-layer film that comprises an insulating film  102  made from a silicon nitride (SiN) film, an interlayer insulating film  103 , and a protecting film  104 . An infrared-absorbing film or member  105  is formed on the protecting film  104  of the light receiver  3 . An etching stopper layer  101  is formed between the insulating layer  102  in the frame  2  and the substrate  1 . The etching stopper layer  101  functions as an etching stopper when the substrate  1  is etched to form the cavity  11 .  
         [0064]     P-polysilicon  6  and N-polysilicon  7  that constitute thermopiles are formed on the beams  4 , respectively. The P-polysilicon  6  of one of the beams  4  is connected to the N-polysilicon  7  of the other one of the beams  4  by an aluminum wire  8   a . Also the N-polysilicon  7  of one of the beams  4  is connected to the P-polysilicon  6  of the other one of the beam  4  by an aluminum wire  8   b . The P-polysilicon  6  of one of the beams  4  is connected by an aluminum wire  8   c  to another end of the N-polysilicon  7 . A connector  9  is formed on another end of the N-polysilicon  7  and on the P-polysilicon  6  that is formed one on of the beams  4 , and a detection circuit (not shown) is connected to the connector  9 .  
         [0065]     The serially connected pair of P-polysilicon  6  and N-polysilicon  7  thus forms a single thermocouple. A thermopile is formed by serially connecting two thermocouples in the order PNPN. In a thermopile, a greater output voltage can be obtained because the electromotive forces of the individual thermocouples are added together. As shown in  FIG. 1B , in the infrared detection element of the illustrated embodiment, the light receiver  3  and the beams  4  are formed higher in the drawing than the surface of the substrate  1 . A structure is provided whereby protuberances  5  that protrude toward the frame  2  are additionally formed on each of the beams  4 , and portions having these protuberances  5  make contact with the substrate  1  first when the light receiver  3  and the beams  4  are displaced toward the substrate  1 . For this reason, the protuberances  5  are preferably formed at positions where displacement is most likely to occur.  
         [0066]     When infrared rays impinge on the light receiver  3 , they are absorbed by an infrared-absorbing film  105  (e.g., a film including a metal compound or the like) that is formed on the upper surface of the light receiver  3 , and the energy of the infrared ray is converted to thermal energy. As a result, the temperature of the light receiver  3  increases. The light receiver-side of the thermopile serves as a hot junction, while the connector on the side of the frame  2  serves as a cold junction. The thermo-electromotive force proportional to the difference in temperature is created through the Seebeck effect. The infrared rays can be detected by removing the electromotive force from the connector  9  to the exterior as an infrared ray detection signal.  
         [0067]     In such a thermal infrared detection element, thermally isolating the light receiver  3  results in improved sensitivity. Therefore, the cross-sectional area of the beams  4  is reduced while the length of the beams  4  is increased so that the heat resistance of the beams  4  increases. For example, when the length of a side of the frame  2  is set at  100  μm, the width of the beams  4  is about 5 μm and the thickness is about 2 μm. For this reason, the beams  4  are readily bent when the infrared detection element is subjected to a force or accelerated. Thus, the light receiver  3  and the beams  4  readily move in a vertical direction shown in  FIG. 1B .  
         [0068]     Therefore, in an infrared detection element in which a protuberance  5  is not formed (see  FIG. 2 ), such as in the prior art, the outside surface of the beams  4  indicated by the symbol A in  FIG. 2  readily makes linear contact with the substrate structure (e.g., substrate  1  and/or frame  2 ) when the beams  4  are displaced toward the substrate  1  (into the page in  FIG. 2 ). As a result, a problem is presented in that the thermal energy of the light receiver  3  dissipates from the light receiver  3  toward the substrate  1  via the contacting portion. As a result of which, the temperature of the light receiver  3  decreases and the temperature detection precision of the thermopile decreases.  
         [0069]     However, the protuberances  5  are formed on the beams  4  in the present invention. Therefore, the protuberances  5  make contact with the substrate structure (e.g., substrate  1  and/or frame  2 ) when displacement occurs, downward movement is hindered, and the light receiver  3  and main bodies of the beams  4  can be prevented from making contact with the substrate structure (e.g., substrate  1  and/or frame  2 ). The area of contact between the protuberances  5  and the substrate structure (e.g., substrate  1  and/or frame  2 ) is reduced, and a substantially point-type contact can be obtained. As a result, when contact is made, transmission of heat from the light receiver  3  to the substrate  1  can substantially be prevented, and decreases in the temperature detection precision of the thermopile can also be prevented. In addition, when the protuberances  5  come into contact with the concavity  1 , considerable bending of the beams  4  can be minimized, and damage to the beams  4  due to excessive deformation can be prevented.  
         [0070]     In the illustrated embodiment, the light receiver  3  and the beams  4  are disposed higher in the drawing (the thickness direction of the substrate  1 ) than the surface of the substrate  1 , as shown in  FIG. 1B . For this reason, when the light receiver  3  and the beams  4  are displaced toward the substrate  1 , the allowable displacement before contact is made with the substrate structure (e.g., substrate  1  and/or frame  2 ) can be made larger than in the prior art, and the likelihood of contact can be reduced. In the illustrated embodiment, the light receiver  3  and the beams  4  are disposed above the substrate  1 . However, these members can be located at the same height.  
         [0071]     A method for manufacturing the infrared detection element shown in  FIG. 1  shall next be described. First, a polysilicon layer  10  is formed on the surface of the silicon substrate  1  by CVD or another method, as shown in  FIG. 3A . The silicon substrate  1  is formed so that a surface of the substrate has a (100) plane orientation and the polysilicon layer  10  is formed in the (100) plane. A peripheral portion of the rectangular polysilicon layer  10  formed on the substrate  1  is then etched into a stepped pattern to form a step  101  in the shape of a rectangular frame, as shown in  FIG. 3B . A portion of the step  101  is used as an etching stopper, while the inside rectangular portion  100  is used as an etching sacrifice layer. The etching stopper  101  and the etching sacrifice layer  100  are described hereunder.  
         [0072]     In the step shown in  FIG. 4 , the etching stopper  101  is formed by the ion implantation of boron into the polysilicon layer  101  provided so as to surround the periphery of the etching sacrifice layer  100 . In the next step, which is shown in  FIG. 5 , a silicon nitride (SiN) film is formed as an insulating film  102  on the etching sacrifice layer  100  and the etching stopper  101  by LPCVD (low-pressure chemical vapor deposition) or the like. The P-polysilicon  6  and the N-polysilicon  7  are each formed on the insulating film  102 .  
         [0073]     For example, a polysilicon film is formed over the entire surface of the insulating layer  102 , the N-polysilicon is formed by the ion implantation of phosphorus (P) or arsenic (As) into the polysilicon layer, and the P-polysilicon is formed by the ion implantation of boron (B) into the polysilicon layer. These layers are then patterned through etching, thereby forming the P-polysilicon  6  and the N-polysilicon  7  in shapes such as those shown in  FIG. 5A . An intermediate insulating film  103  composed of a silicon oxide film or the like is next formed, as shown in  FIG. 5C . The aluminum wires  8   a  to  8   c  and the connector  9  (not shown) are formed. Now a protecting film  104  composed of a silicon oxide film or the like is subsequently formed over the entire surface.  
         [0074]     In the step shown in  FIG. 6 , an infrared-absorbing film  105  is formed on the protecting film  104  of the light receiver  3 , and an etching slit S is formed by anisotropic etching using plasma etching or the like. In the step shown in  FIG. 7 , the polysilicon etching sacrifice layer  100  and the silicon substrate  1  are anisotropically etched from the etching slit S using hydrazine (anisotropic etching liquid). Etching stops at the etching stopper  101 , and the concavity  1   a  is formed on the substrate  1 . The surface of the substrate  1  is aligned with the (100) plane, and is therefore etched to a pyramidal shape by crystalline anisotropic etching. The surface of the concavity  1   a  is aligned with the (111) plane of the silicon single crystal. The infrared detection element shown in  FIG. 1  is formed according to these steps.  
         [0075]      FIG. 8  is a simplified top plan view of an infrared detection element in accordance with a first modification of the present invention. In the embodiment described above, a configuration was employed in which the light receiver  3  was supported by the beams  4 . However, in the first modification, a structure is employed in which the light receiver  3  is supported on one side by a single beam  4 . In this instance, the position where displacement is greatest is to the right of and below the light receiver  3 , which is a position on the light receiver  3  that is furthest from where the beam  4  and light receiver  3  make contact. For this reason, a protuberance  5  is formed on this position on the light receiver  3 . The contacting area can thereby be kept to a minimum when the light receiver  3  is displaced toward the substrate structure (e.g., substrate  1  and/or frame  2 ), and the detection precision can be prevented from decreasing. The manufacturing steps are the same as that of the infrared detection element of the first embodiment described above, and a description thereof is accordingly omitted.  
         [0076]      FIG. 9  is a simplified top plan view of an infrared detection element in accordance with a second modification of the present invention. In the infrared detection element of the second modification, the light receiver  3  is supported by a pair of the beams  4 . The beams  4  are each formed into zigzag shapes and include a first beam  401 , a second beam  402 , and a third beam  403 . The beams  4  become progressively narrower in the order of the beam  403 , the beam  402 , and the beam  401 . When the beams  4  have such a shape, a heat transmission path from the light receiver  3  to the frame  2  becomes longer and the beams  4  become narrower closer to the light receiver  3 . Therefore, the amount of heat transmitted from the light receiver  3  toward the substrate  1  is extremely low, and the heat detection precision can be prevented from decreasing. On the other hand, the beams  4  readily bend, and the light receiver  3  readily comes into contact with the substrate structure (e.g., substrate  1  and/or frame  2 ).  
         [0077]     In the infrared detection element of the second modification, the protuberance  5  is formed on the portion where the first beam  401  and the second beam  402  are connected. When the beams  4  bend due to impact, force or other action, the light receiver  3  will undergo the greatest amount of displacement toward the substrate structure (e.g., substrate  1  and/or frame  2 ). However, displacement is limited by the protuberance  5  coming into contact with the substrate structure (e.g., substrate  1  and/or frame  2 ), and the light receiver  3  can thereby be prevented from coming into contact with the substrate structure (e.g., substrate  1  and/or frame  2 ). As a result, the contacting area between the beams  4  and the substrate structure (e.g., substrate  1  and/or frame  2 ) during displacement can be greatly reduced, and the detection precision during deformation can be prevented from deteriorating.  
         [0078]     In the second modification shown in  FIG. 9 , the protuberances  5  are formed on the portion where the first beam  401  and the second beam  402  are connected. However, the position of the protuberance  5  is not limited to this position. As long as the light receiver  3  can be prevented from making contact with the substrate structure (e.g., substrate  1  and/or frame  2 ). The position can, for example, be a connector between the first beam  401  and the light receiver  3 . In addition, the area of contact between the protuberance  5  and the substrate structure (e.g., substrate  1  and/or frame  2 ) is extremely small. Therefore, the protuberance  5  can also be provided to the outer periphery of the light receiver  3 , as in the example shown in  FIG. 8 . However, the protuberance  5  is preferably provided to the beams  4  rather than the light receiver  3  in order to minimize the amount of heat released by the light receiver  3  toward the substrate  1 , and in order to minimize reduction in the detection sensitivity.  
         [0079]      FIG. 10  is a diagram showing a third modification of the present invention, with  FIG. 10A  being a top plan view of the infrared detection element, and  FIG. 10B  being a cross-sectional view along F-F′. In third modification, the beams  4  are formed into a coil shape so as to surround the light receiver  3 . The protuberance  5  is formed on the side of the frame  2 , and protrudes so as to extend from the frame  2  toward the beams  4 . The light receiver  3  and the beams  4  are formed higher than the frame  2 , as shown in  FIG. 10B . Thus, when the infrared detection element having the coil-shaped beams  4  is subjected to an impact, force or other action, and the light receiver  3  and the beams  4  are subjected to a downward force as shown in  FIG. 11B , the beams  4  will bend so as to twist and move downward, and the light receiver  3  will be displaced downward while being rotated, as shown in  FIG. 11A .  
         [0080]     As a result, the beam  4  that is placed on the left side of the light receiver  3  in the drawing and that is adjacent the protuberance  5  will be prevented from moving in a leftward direction, rising onto or making contact with the protuberance  5 , and moving even further downward during deformation. The position where the protuberance  5  is formed can be set to a position where the deformed beam  4  will rise onto the protuberance  5 , with the state of deformation of the beam  4  having been predicted in advance. In the resulting structure, the beam  4  and substrate  1  will short-circuit through the protuberance  5 , rigidity will mechanically increase, and forceful breakage will tend not to occur. In the structure provided in third modification, the beam  4  is stopped by the protuberance  5  formed on the frame  2 . Therefore, the concavity  1   a  does not need to be formed using crystalline anisotropic etching, which exposes the (111) plane of the substrate  1 , as in a detection element such as the one described in the above embodiment. The protuberance  5  on the beam  4  is prevented from being deformed through contact made with an inclined surface of the concavity  1   a  of the substrate  1 . In other words, the concavity  1   a  such as shown in  FIG. 10B  can be formed by isotropic etching, or by anisotropic etching perpendicular to the surface of the substrate  1 . In addition, a through-hole rather than a concavity  1   a  can be used on the lower part of the light receiver  3  and the beams  4 .  
         [0081]      FIG. 12  is a diagram showing a fourth modification of the present invention, with  FIG. 12A  being a top plan view of an infrared detection element in which a beam  4  is not deformed, and  FIG. 12B  being a top plan view of an instance in which the beam  4  has been subjected to a force and has been deformed. In the fourth modification, a protuberance  5  is formed on both the beam  4  and the frame  2 , and a protuberance  5   a  that protrudes toward the frame  2  is formed on the beam  4 . A protuberance  5   b  that protrudes toward the beam  4  is also formed on the frame  2  on the side on which the protuberance  5   a  protrudes. In this instance as well, the light receiver  3  and the beams  4  are formed at positions that are higher than the frame  2  in relation to the thickness direction of the substrate in a manner similar to the third modification (see  FIG. 10B ).  
         [0082]     As described in the abovementioned third modification, when the infrared detection element having a coiled beam  4  such as that shown in  FIG. 11A  is subjected to a downward force, the beam  4  is deformed so that the light receiver  3  rotates. However, when a downward force is applied and an inertial force is further exerted upward by an impact, force or the like in a plane such as the one shown in  FIG. 12B , the beam  4  and light receiver  3  are displaced toward the upper part of the drawing, and the part of the beam  4  that approaches the protuberance  5  decreases in size, as compared with the case shown in  FIG. 11A . For this reason, the beam  4  deforms dramatically below the frame  2  without being stopped by the protuberance  5  on the frame  2  side, and the beam  4  makes contact with a surface defining the concavity  1   a.    
         [0083]     In fourth modification, a protuberance  5   a  is provided to the beam  4  so that a protuberance  5   b  provided to the frame  2  is surrounded on either side. The protuberance  5   a  of the beam  4  accordingly rises up onto or strikes the protuberance  5   b  on the frame  2  and is thereby stopped, even when subjected to a force in the planar direction other than a downward force. As a result, the protuberance  5   a  and protuberance  5   b  come into contact, the rigidity of the beam  4  is thereby temporarily increased, and forceful breakage is much less likely to occur.  
         [0084]     In  FIG. 12 , the protuberance  5   b  is formed on the frame  2 . However, in accordance with a fifth modification of the present invention, the protuberance  5   a  on the beam  4  can be made to protrude toward the light receiver  3 , and the protuberance  5   b  that is stopped by the protuberance  5   a  can be provided to the light receiver  3 , as shown in  FIG. 13A . In this instance, when the beam  4  bends, the protuberance  5   b  of the light receiver  3  does not rise up onto the protuberance  5   a  formed on the beam  4 . However, the side surfaces of the protuberances  5   a ,  5   b  come into contact with each other as shown in  FIG. 13   b , the protuberance  5   b  is stopped by the protuberance  5   a , and further rotation of the light receiver  3  is prevented. As a result, bending of the beam  4  is decreased, and the light receiver  3  and the beams  4  can be prevented from making contact with the surface of the concavity  1   a.    
         [0085]     Such an effect can also be achieved by using the protuberances  5   a ,  5   b  shown in  FIG. 12 . The protuberances  5   a ,  5   b  can be formed to the same height. However, the protuberance  5   b  is preferably formed at a higher position than the protuberance  5   a . The protuberances  5   a ,  5   b  will therefore readily be stopped, and a state in which the protuberance  5   b  rises onto the protuberance  5   a  will readily occur. The protuberances  5   a ,  5   b  are preferably disposed in positions that are in close proximity to each other in order to enable the protuberance  5   a  to be readily stopped by the protuberance  5   b . In  FIGS. 12 and 13 , a single protuberance has a protuberance on either side; however, the number of protuberances is not particularly limited.  
         [0086]      FIG. 14  is a diagram showing a sixth modification of the present invention. In sixth modification, a protuberance formed on the light receiver  3  and a protuberance formed on the beam  4  engage during bending of the beam  4 , and further bending of the beam  4  is prevented in the same manner as in sixth modification. In sixth modification, the downward displacement of the light receiver  3  during bending of the beam  4  is minimized by engagement between a protuberance  512  on the light receiver  3  and a protuberance  501  on the beam  4 , but a protuberance  511  on the light receiver  3  and a protuberance  502  on the beam  4  also engage when the light receiver  3  is upwardly displaced, whereby upward displacement of the light receiver  3  is also minimized. As a result, the light receiver  3  and the beams  4  can be prevented from making contact with the surface defining the concavity  1   a  of the substrate  1 , and damage to the beam  4  due to excessive bending can also be prevented.  
         [0087]     The protuberances  501 ,  502 ,  511  and  512  are each formed in pairs at the top and bottom of the drawing.  FIG. 15A  is a cross-sectional view along  15 A- 15 A of the portion having the protuberances  501  and  511 .  FIG. 15B  is a cross-sectional view along  15 B- 15 B of the portion having the protuberances  502  and  512 . As shown in  FIG. 15A , the protuberance  501  is formed on the bottom surface of the beam  4 , while the protuberance  511  is formed on the top surface of the light receiver  3 . The protuberances  501  and  511  are disposed so as to overlap across a gap formed in the thickness direction of the substrate. For this reason, when the light receiver  3  is displaced in the direction of the arrow, the protuberance  511  strikes the protuberance  501  of the beam  4 , and the light receiver  3  and the beams  4  engage in the contacting portion, making it possible to prevent the portion having the light receiver  3  from being markedly displaced. As a result, the light receiver  3  and the beams  4  can be prevented from making linear contact with the surface defining the concavity  1   a , and excessive bending of the beam  4  can be prevented.  
         [0088]      FIGS. 16 through 20  are diagrams describing a process for manufacturing the infrared detection element of sixth modification. A case in which the frame  2 , the light receiver  3 , and the beams  4  are formed at the same height shall be described hereunder. First, the etching sacrifice layer  100  and the etching stopper layer  101  are created by forming a polysilicon layer on the silicon substrate  1 , as shown by the cross-sectional diagram along  16 - 16  in  FIG. 16B . As described above, the frame  2 , the light receiver  3 , and the beams  4  are formed to the same height. Therefore, the etching sacrifice layer  100  and the etching stopper layer  101  have the same thickness.  
         [0089]     The light receiver  3  and the beams  4  may be made higher than the frame  2  by making the etching sacrifice layer  100  thicker in the same manner as in  FIG. 4B . Next, the following element are formed in the stated order in the same manner as in the step shown in  FIG. 5 : the insulation layer  102  formed from a silicon nitride film, the P-polysilicon  6  and N-polysilicon  7  on the insulation layer  102 , the interlayer insulating film  103 , the aluminum wires  8   a  through  8   c , the connector  9  (not shown), and the protecting film  104 . Thus, a temperature sensor is formed.  
         [0090]     In the step shown in  FIG. 17 , an etching slit S is formed using anisotropic etching. The anisotropic etching is performed until the insulating film  102  is exposed. In the step shown in  FIG. 18 , the insulating film  102 , which is a substrate for the beams  4  and the light receiver  3 , is etched using anisotropic etching, and the protuberances  501 ,  512 , which are provided to the bottom surfaces of the beams  4  and the light receiver  3 , are formed. In the step shown in  FIG. 19 , the etching slit S is filled with a polyimide or the like to form a slit sacrifice layer  108 . A resist material, silicon, or a material other than a polyimide may be used as the material for the slit sacrifice layer  108 .  
         [0091]     In the step shown in  FIG. 20 , a silicon nitride film or the like is formed on a top surface of the substrate shown in  FIG. 19 . The silicon nitride film is then etched into a pattern, thereby forming the upper protuberances  502  and  511 . In the step shown in  FIG. 21 , an infrared-absorbing film  105  is formed on the protecting film  104  of the light receiver  3 . The slit sacrifice layer  108  is then removed, and the concavity  1   a  is subsequently formed on the substrate  1  by performing crystalline anisotropic etching using hydrazine.  
         [0092]      FIG. 22  is a diagram showing a seventh modification of the present invention. In the infrared detection element of the seventh modification, the protuberances  5  protrude from the bottom surfaces of the beams  4  toward the concavity  1   a . The protuberance  5  is formed on the beams  4  (see  FIG. 22B ). For this reason, when the beams  4  and the light receiver  3  are displaced downwardly (in the direction of the concavity  1   a ) due to an impact, force or other action, the protuberance  5  strikes the substrate  1 . Thus, the beam  4  is prevented from making linear contact with the substrate  1 , and excessive bending of the beams  4  can also be prevented. In addition, the beams  4  can be more effectively prevented from bending in comparison to when a protuberance that is parallel to the substrate  1  is used. The protuberance  5  can also be formed on the bottom surface of the light receiver  3 .  
         [0093]      FIGS. 23 and 24  are diagrams describing the manufacturing process. In the step shown in  FIG. 23 , holes  61  are formed in the silicon substrate  1 . The holes  61  are used for forming a protuberance  5 , and are formed in correspondence with the position where the protuberance  5  of the beam  4  is formed. A lateral cross-section of the holes  61  need not be rectangular in shape. The polysilicon etching-sacrifice layer  100  is next formed on the surface of the substrate  1 , and holes  62  having the shape of the protuberance  5  are subsequently formed by subjecting the area having the holes  61  to anisotropic etching.  
         [0094]     In the step shown in  FIG. 24 , boron or another material is ion-implanted into the peripheral part of the etching sacrifice layer  100 , thereby forming the etching stopper  101 . Next, a silicon nitride film or other insulating film  102  is formed, and the insulating film  102  deposited in the holes  62  forms the protuberance  5 . The manufacturing process is thereafter the same as the process for manufacturing the infrared detection element shown in  FIG. 1  (see  FIGS. 5 through 7 ), and a description thereof shall accordingly be omitted. In  FIG. 24 ,  FIG. 24B  shows a cross section of the substrate along  24 B- 24 B, and  FIG. 24A  shows a cross section along  24 A- 24 A in  FIG. 24B .  
         [0095]      FIGS. 25A through 25D  illustrate several diagrams showing various shapes of distal ends of the protuberances  5  of the present invention. In  FIG. 25A , the distal end of the protuberance is triangular, whereby the area of the portion where the protuberance  5  and the surface defining the concavity  1   a  or the frame  2  come into contact is minimized, thereby enabling the sensitivity of the detection element due to this contact to minimally decrease. In the example shown in  FIG. 25B , the distal end of the protuberance is arched, whereby damage to the distal end of the protuberance due to contact between the protuberance  5  and the surface defining the concavity  1   a  or the frame  2  is prevented. In the example shown in  FIG. 25C , the distal end of the protuberance is curved in the shape of a knife or other type of blade, whereby the surface area of the contacting portion during bending of the beam  4  will correspond to the degree of bending of the beam  4 , and the protuberance  5  is less likely to be damaged.  
         [0096]     In the example shown in  FIG. 25D , the protuberance  5  is bifurcated so as to have a thick portion  522  and a thin portion  521 . The structure allows the thin portion  521  to make contact first when the beam  4  bends toward the surface defining the concavity  1   a  or the frame  2 . When the light receiver  3  is displaced toward the concavity  1   a , the thin portion  521  is initially supported by making contact with the concavity  1   a . If a supporting limit of the thin portion  521  is exceeded, the thick portion  522  will make contact with the concavity  1   a  and will be supported.  
         [0097]     As described above, the protuberance  5  that comes into contact with the surface defining the concavity  1   a  or the frame  2 , and the light receiver  3  and the beams  4  are supported by the protuberance  5  upon being displaced. Therefore, the surface area of the contacting portion can be made smaller than in the prior art, and the detection performance of the detection element resulting from this contact can be prevented from declining. In addition, excessive bending of the beam  4  can be prevented, and damage to the beam  4  can be avoided.  
       General Interpretation of Terms  
       [0098]     In understanding the scope of the present invention, the term “comprising” and its derivatives, as used herein, are intended to be open ended terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers and/or steps. The foregoing also applies to words having similar meanings such as the terms, “including”, “having” and their derivatives. Also, the terms “part,” “section,” “portion,” “member” or “element” when used in the singular can have the dual meaning of a single part or a plurality of parts. Accordingly, these terms, as utilized to describe the present invention should be interpreted relative to a vehicle equipped with the present invention. The terms of degree such as “substantially”, “about” and “approximately” as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed.  
         [0099]     While only selected embodiments have been chosen to illustrate the present invention, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made herein without departing from the scope of the invention as defined in the appended claims. For example, the size, shape, location or orientation of the various components can be changed as needed and/or desired. Components that are shown directly connected or contacting each other can have intermediate structures disposed between them. The functions of one element can be performed by two, and vice versa. The structures and functions of one embodiment can be adopted in another embodiment. It is not necessary for all advantages to be present in a particular embodiment at the same time. Every feature which is unique from the prior art, alone or in combination with other features, also should be considered a separate description of further inventions by the applicant, including the structural and/or functional concepts embodied by such feature(s). Thus, the foregoing descriptions of the embodiments according to the present invention are provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.