Abstract:
A manufacturing method of a semiconductor device that is sealed by bonding a sealing member to a substrate mounting a semiconductor element thereon includes the steps of: forming an opening in the sealing member; and closing the opening after the sealing member is bonded to the substrate.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to manufacturing methods of semiconductor devices, and more particularly, to a manufacturing method of a semiconductor device that includes a step of sealing the semiconductor device by providing a sealing member on a substrate mounting a semiconductor element thereon. 
     2. Description of the Related Art 
     Recently, with the rapid progress and development in information communication technologies, improvement of data communication speed and increase in data communication amount have been realized, and mobile electronic devices such as mobile phones and notebook computers incorporating therein a semiconductor device (imaging apparatus) such as a CCD (charge coupled device) image sensor and a CMOS image sensor are becoming popular. Such mobile electronic devices can transmit in real time image data obtained by an imaging apparatus in addition to character data (refer to Japanese Laid-Open Patent Application No. 2002-185827, for example). 
       FIG. 1A  shows such a conventional imaging apparatus  100 . As shown in  FIG. 1A , the imaging apparatus  100  generally includes an optical sensor element  1 , a substrate  2 , and a holder  5 . The optical sensor element  1  is, for example, a CCD image sensor or a CMOS image sensor. The optical sensor element  1  is mounted on the substrate  2 . 
     The holder  5  is provided with a lens  6  for focusing an image on a photo-accepting surface of the optical sensor element  1 . The holder  5  is fixed to the substrate  2  by using adhesive  4 . Thus, the optical sensor element  1  is sealed in an internal space  7  formed in the holder  5 . Accordingly, it is possible to prevent dust from adhering to an imaging surface of the optical sensor element  1 . 
     Referring to  FIGS. 1A and 2A  through  2 C, a description is given below of a manufacturing method of the imaging apparatus  100  having the above-mentioned structure. 
     In order to manufacture the imaging apparatus  100  shown in  FIG. 1A , first, as shown in  FIG. 2A , the optical sensor element  1  is mounted on the substrate  2 . Although not shown in the drawings, the optical sensor element  1  is electrically connected to the substrate  2  by, for example, gold wire. 
     Then, as shown in  FIG. 2B , the adhesive  4  is deposited on a top surface of the substrate  2  at a predetermined portion by using a dispenser  3 . The positions at which the adhesive  4  is deposited are set so as to correspond to the shape of a bottom end of the holder  5 . Generally, a thermo-setting resin, which provides a good bonding and achieves reliable bonding, is used as the adhesive  4 . 
     Upon completion of the depositing process of the adhesive  4 , as shown in  FIG. 2C , the holder  5  is pressed against the substrate  2  at the positions where the adhesive  4  is deposited so as to temporarily fix the holder  5  to the substrate  2 . Then, the substrate  2  on which the holder  5  is temporarily fixed is loaded in a curing apparatus and a curing process (heating process) is performed so as to cure the adhesive  4 . Consequently, the adhesive  4  is cured and the holder  5  is bonded to the substrate  2 . 
     With the above-mentioned manufacturing steps, the imaging apparatus  100  as shown in  FIG. 1A  is manufactured. Since the optical sensor element  1  is sealed by the holder  5  as mentioned above, it is possible to prevent dust or the like from adhering to the optical sensor element  1 . 
     In a state where the holder  5  is temporarily fixed to the substrate  4  by using the adhesive  4 , the internal space  7  formed between the substrate  2  and the holder  5  is airtight. When the curing process is performed in such a state, the air in the internal space  7  is heated and expanded, which results in an increase in the air pressure in the internal space  7 . Thus, a difference (air pressure difference) is generated between the inside and outside of the holder  5 . 
     As mentioned above, in the manufacturing method of the conventional semiconductor device, the curing process is performed in the state where the internal space  7 , which is formed by the holder  5  and the substrate  2 , is sealed. Hence, as shown in  FIG. 1B , there is a problem in that a damaged portion  8  may be generated at a bonding position between the substrate  2  and the holder  5  due to the increase in the air pressure in the holder  5  (internal space  7 ), and airtightness of the internal space  7  formed by the holder  5  and the substrate  2  may not be maintained even if the adhesive  4  is cured. In such a case, dust may enter the internal space  7  via the damaged portion  8  and adhere to the optical sensor element  1 , which causes a reduction in reliability of the imaging apparatus  100 . 
     SUMMARY OF THE INVENTION 
     A general object of the present invention is to provide an improved and useful manufacturing method of a semiconductor device in which one or more of the above-mentioned problems are eliminated. 
     Another and more specific object of the present invention is to provide a manufacturing method of a semiconductor device that can suppress generation of a damaged portion even if the pressure in a sealing member is increased due to heating. 
     In order to achieve the above-mentioned objects, according to one aspect of the present invention, there is provided a manufacturing method of a semiconductor device in which method the semiconductor device is sealed by bonding a sealing member to a substrate mounting a semiconductor element thereon, the manufacturing method including the steps of: 
     forming an opening in the sealing member; and 
     closing the opening after the sealing member having the opening formed therein is bonded to the substrate so as to seal the semiconductor device. 
     According to the present invention, the opening formed in the sealing member is closed after the sealing member is bonded to the substrate so as to seal the semiconductor device. Hence, even if a heating process is performed after the sealing member is bonded to the substrate, the air in the sealing member communicates with the air outside the sealing member (more specifically, the air in the space formed by the sealing member and the substrate communicates with the air outside the sealing member and the substrate). Hence, a pressure difference is not generated between the inside and outside the space formed by the sealing member (more specifically, between the pressure in the space formed by the sealing member and the substrate and the pressure of the air outside the space formed by the sealing member and the substrate). Accordingly, it is possible to prevent a bonding portion between the sealing member and the substrate from being damaged and maintain airtightness of the space. 
     In an embodiment of the present invention, the step of closing the opening may be performed after heating processes of the semiconductor element, the substrate, and the sealing member end. 
     Accordingly, since the opening is closed after the heating processes of the respective members end, it is possible to positively avoid a pressure difference between the inside and outside of the sealing member. 
     In an embodiment of the present invention, the step of closing the opening may be performed by using an adhesive. In addition, the adhesive may be an ultraviolet-curing type resin or an instant adhesive. 
     In a case where the ultraviolet-curing type adhesive is used, the ultraviolet-curing type is cured in a short period of time by irradiation of ultraviolet light. On the other hand, in a case where the instant adhesive is used, the instant adhesive is cured in the air in a short period of time. Hence, it is possible to close the opening in a short period of time. Accordingly, it is possible to avoid faulty bonding that is caused by variation of the pressure in the sealing member during the time period required for the adhesive to be cured. 
     In an embodiment of the present invention, the semiconductor element may be a photoelectric conversion element. 
     By using the photoelectric conversion element as the semiconductor element, it is possible to perform a good photoelectric conversion process. That is, though the photoelectric conversion element is vulnerable to adhesion of dust thereto, according to the present invention, since it is possible to maintain an airtight state of the space formed by the sealing member and the substrate, dust does not enter the space formed by the sealing member and the substrate. Thus, dust does not adhere to the photoelectric conversion element and it is possible to perform good photoelectric conversion by using the photoelectric conversion element. 
     According to the present invention, even if the heating process is performed after the sealing member is bonded to the substrate, the air in the space formed between the sealing member and the substrate communicates with the air outside the space formed by the sealing member and the substrate. Hence, a pressure difference is not generated between inside and outside the space. Accordingly, it is possible to prevent the bonding portion between the sealing member and the substrate from being damaged and maintain airtightness of the space. Thus, it is possible to improve reliability of a semiconductor device. 
     Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the following drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a schematic diagram for explaining a manufacturing method of a conventional semiconductor device; 
         FIG. 1B  is a schematic diagram showing a state where a damaged portion is generated in the semiconductor device shown in  FIG. 1A ; 
         FIGS. 2A ,  2 B and  2 C are schematic diagrams for explaining the manufacturing method of the conventional semiconductor device shown in  FIG. 1A ; 
         FIGS. 3A ,  3 B and  3 C are schematic diagrams for explaining a manufacturing method of a semiconductor device according to one embodiment of the present invention; 
         FIGS. 4A and 4B  are additional schematic diagrams for explaining the manufacturing method of the semiconductor device according to the embodiment of the present invention; and 
         FIG. 5  is a schematic diagram showing a semiconductor device (imaging apparatus) manufactured by the manufacturing method according to the embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A description is given below of a preferred embodiment of the present invention, with reference to the drawings. 
       FIGS. 3A through 3C ,  4 A and  4 B are diagrams for explaining a manufacturing method of a semiconductor device according to one embodiment of the present invention.  FIG. 5  shows a semiconductor device (imaging apparatus)  10  manufactured by the manufacturing method according to the embodiment of the present invention. 
     It should be noted that, in this embodiment, the description is given by taking the imaging apparatus  10  incorporating therein a semiconductor element (hereinafter referred to as “the optical sensor element  11 ”) such as a CCD (charge coupled device) sensor or a CMOS sensor as a semiconductor device. 
     First, for convenience of explanation, the structure of the imaging apparatus  10  is explained, and then, the manufacturing method of the imaging apparatus  10  is explained. 
     As shown in  FIG. 5 , the imaging apparatus  10  generally includes the optical sensor element  11 , a substrate  12 , and a holder  13 , which serves as a sealing member. 
     The optical sensor element  11  is, as mentioned above, a semiconductor element such as a CCD image sensor or a CMOS image sensor. The optical sensor element  11  is mounted on the substrate  12 . More specifically, a control element  14  is mounted on the substrate  12 , and the optical sensor element  11  is mounted on the control element  14 . 
     The control element  14  performs drive control of the optical sensor element  11 . Hence, the optical sensor element  11  is connected to the control element  14  by means of wires  15 . In addition, the control element  14  is electrically connected to the substrate  12  by means of wires  17 . Further, a passive element  16  such as a condenser is also mounted on the substrate  12 . 
     The holder  13  includes a lens holder  20 , a housing  21 , and a condenser lens  22 , for example. The holder  13  is formed into a cylindrical shape and is provided with the condenser lens  22  therein. The condenser lens  22  serves to focus an image with respect to a photo-accepting surface of the optical sensor element  11  in a state where the holder  13  is mounted on the substrate  12 . An aperture  23  for cutting unwanted light is provided on a top surface of the condenser lens  22 . 
     A cover glass  24  is provided at a top portion of the holder  13  that faces the condenser lens  22 . The cover glass  24  is a cover for dust control and prevents dust from adhering to the condenser lens  22 . 
     The housing  21  includes a small diameter portion  21   a  and a large diameter portion  21   b . A shoulder portion  21   c  is formed between the small diameter portion  21   a  and the large diameter portion  21   b . A protruding screw portion is formed on the outer periphery of the small diameter portion  21   a , and a receiving screw portion is formed on the inner periphery of the lens holder  20 . 
     That is, the lens holder  20  is configured to be screwed to the small diameter portion  21   a  of the housing  21 . In a state where the lens holder  20  is screwed to the housing  21 , the lens holder  20  and the housing  21  form an airtight boundary. 
     The bottom portion of the large diameter portion  21   b  is fixed to the substrate  12  by means of adhesive  28 . Thus, an internal space  27  formed between the substrate  12  and the holder  13  is airtight. Accordingly, it is possible to prevent dust from adhering to the optical sensor element  11 , which is located in the internal space  27 . 
     Referring to the shoulder portion  21   c  formed between the small diameter portion  21   a  and the large diameter portion  21   b , in this embodiment, an air hole (opening)  25  is formed in the shoulder portion  21   c , and the air hole  25  is closed with the adhesive  28 . 
     Next, referring to  FIGS. 3A through 3C ,  4 A and  4 B, a description is given below of the manufacturing method of the imaging apparatus  10  having the above-mentioned structure. It should be noted that, in  FIGS. 3A through 3C ,  4 A and  4 B, only a part of the structure shown in  FIG. 5  is illustrated so that the manufacturing method is easily understood. 
     In order to manufacture the imaging apparatus  10  shown in  FIG. 5 , first, as shown in  FIG. 3A , the optical sensor element  11  is mounted on the substrate  12 . Although not shown in the drawings, in this step, the passive element  16  is mounted, and bonding processes of the wires  15  and  17  are also performed. 
     Then, as shown in  FIG. 3B , the adhesive  28  is deposited on the top surface of the substrate  12  at predetermined positions by using a dispenser  29 . The positions at which the adhesive  29  is deposited are set so as to correspond to the shape of the bottom portion of the holder  13  (more specifically, the shape of the bottom portion of the large diameter portion  21   b ). Generally, a thermo-setting resin, which provides a good bonding and achieves reliable bonding, is used as the adhesive  28 . 
     Upon completion of the depositing process of the adhesive  28 , as shown in  FIG. 3C , the bottom portion of the holder  13  is pressed against the substrate  12  at the positions where adhesive  28  is deposited. In the aforementioned manner, the holder  13  is temporarily fixed to the substrate  12 . Then, the substrate  12  on which the holder  13  is temporarily fixed is loaded in a curing apparatus and a curing process (heating process) is performed so as to cure the adhesive  28 . 
     Consequently, the adhesive  28  is cured and the holder  13  is bonded to the substrate  12 . In such a state, the internal space  27  formed between the substrate  12  and the holder  13  is sealed with the optical sensor element  11  located therein. 
       FIG. 4A  shows the substrate  12  and the holder  13  during the curing process. By performing the curing process, the air inside the internal space  27  is heated and expanded. However, the air hole (opening)  25  is formed in the holder  13  in this embodiment. Thus, the internal space  25  communicates with the outside of the holder  13  via the air hole  25 . 
     Hence, even if the air in the internal space  27  formed between the substrate  12  and the holder  13  is heated and expanded, the air is discharged to the outside of the holder  13  via the air hole  25  (such air flows are indicated by arrows A in FIG.  4 A). That is, the pressure in the internal space  27  becomes the same as the pressure outside the holder  13 , and a pressure difference (air pressure difference) is not generated between the inside and outside of the holder  13  during the curing process. Accordingly, it is possible to prevent the bonding portion between the substrate  12  and the holder  13 , more specifically, the portion bonded by means of the adhesive  28 , from being damaged during the curing process. 
     Upon completion of the curing process (heating process) for bonding the holder  13  to the substrate  12 , a process for closing the air hole  25  is subsequently performed. The process for closing the air hole  25  is performed after the temperatures of the substrate  12  and the holder  13  return to normal temperatures. 
     When there are other heating processes for heating the optical sensor element  11 , the substrate  12 , and the holder  13  in addition to the curing process for bonding the holder  13  to the substrate  12 , the process for closing the air hole  25  is performed after such other heating processes are completed. 
     In this embodiment, the adhesive  28  is used in the process for closing the air hole  25 . The adhesive  28  is an ultraviolet-curing type adhesive. By irradiating ultraviolet light to the air hole  25  after filling the air hole  25  with the adhesive  28  in a softened state, the adhesive  28  is cured in a short period of time. 
     By using the ultraviolet-curing type adhesive  28  as in this embodiment, it is possible to cure the adhesive  28  in a short period of time by irradiation of ultraviolet light. It is conceivable that the pressure in the holder  13  (internal space  27 ) may vary since the temperature of the internal space  27  is increased by irradiation of ultraviolet light during the time period required for the adhesive  28  to be cured. However, since the air hole  25  is provided in this embodiment, the pressure in the holder  13  does not vary during the time period required for the adhesive  28  to be cured. Thus, it is possible to avoid faulty bonding. 
     The adhesive  28  is not limited to the ultraviolet-curing type, and an instant adhesive that is cured in the air in a short period of time may be used instead. 
     By closing the air hole  25  in the aforementioned manner, the internal space  27  is separated from the outside of the holder  13 , and the optical sensor element  11  is located in the sealed internal space  27 . Since the air hole  25  is closed after completion of the heating process performed in the manufacturing process of the imaging apparatus  10 , a pressure difference between the inside and outside of the holder  13  is not generated after the internal space  27  having therein the optical sensor element  11  is sealed. 
     Hence, it is possible to prevent the bonding portion between the substrate  12  and the holder  13  from being damaged and maintain the airtight state of the internal space  27 . Thus, it is possible to positively avoid adhesion of dust to the optical sensor element  11 . 
     The optical sensor element  11  (a CCD sensor or a CMOS sensor, for example) used in this embodiment is vulnerable to adhesion of dust. According to this embodiment, since it is possible to positively avoid entering of dust from the outside, it is possible to perform a good photoelectric conversion process by the optical sensor element  11  and improve reliability of the imaging apparatus  10 . 
     Further, in the above-mentioned embodiment, only the single air hole (opening)  25  is formed. However, the number of the air holes  25  is not limited to one. Additionally, in the above-mentioned embodiment, the air hole  25  is provided in the shoulder portion  21   c  of the holder  13  (housing  21 ). However, this is not a limitation of the position of the air hole  25 . The air hole  25  may be formed in the large diameter portion  21   b  or the substrate  12 . 
     According to the present invention, even if the curing process (heating process) is performed after the holder  13  (sealing member) is bonded to the substrate  12 , the air in the internal space  27  formed between the holder  13  and the substrate  12  communicates with the air outside the holder  13  (internal space  27 ). Hence, a pressure difference is not generated between the inside and outside the holder  13  (internal space  27 ). Accordingly, it is possible to prevent the bonding portion between the holder  13  and the substrate  12  from being damaged and maintain airtightness of the internal space  27 . Thus, it is possible to improve reliability of the semiconductor device (imaging apparatus)  10 . 
     The present invention is not limited to the specifically disclosed embodiments, and variations and modifications may be made without departing from the scope of the present invention. 
     The present application is based on Japanese priority application No. 2003-276961 filed on Jul. 18, 2003, the entire contents of which are hereby incorporated by reference.