Patent Publication Number: US-2010127341-A1

Title: Imaging Device Manufacturing Method, Imaging Device and Portable Terminal

Description:
TECHNICAL FIELD 
     The present invention relates to a manufacturing method of a compact imaging device suitable for being installed in, for example, a mobile phone, an imaging device and a portable terminal. 
     BACKGROUND 
     In recent years, a compact and thin imaging device is increasingly installed in a portable terminal representing a compact and thin electronic instrument such as a mobile phone and a PDA (Personal Digital Assistant). Utilizing these instruments, besides phonetical information, image information can be transmitted between remote places. 
     As a manufacturing method of such a compact imaging device, there is known a method wherein a plurality of image sensors are formed in a shape of an array on a silicon wafer, then a lens array wherein a plurality of optical lenses are formed is bonded with the silicon wafer, and the wafer is cut in accordance with arrangement of the image sensors (for example, refer to Patent Document 1: Unexamined Japanese Patent Application Publication No, 2002-290842. 
     Patent Document 1: Unexamined Japanese Patent Application Publication No. 2002-290842. 
     DISCLOSURE OF THE INVENTION 
     Problems to be Resolve by the Invention 
     In the manufacturing method of the aforesaid Patent Document 1, since the wafer is cut to separate after bonding a plurality of the lens arrays corresponding to individual image sensors on the silicon wafer, it is unavoidable that the lenses are disposed on defective image sensors having some kinds of problems. Therefore the lens along with the defective image sensor has to be discarded, which results in increase of the cost. 
     The present invention has one aspect to solve the above problem and an object of the present invention is to provide a manufacturing method which enables lower cost manufacturing of the imaging device, a lower cost imaging device through the manufacturing method thereof and a portable terminal using the imaging device thereof. 
     Means to Resolve the Problems 
     A manufacturing method of an imaging device described in claim  1  having an imaging optical unit to lead object light and an imaging element on which a plurality of light receiving pixel sections are formed to conduct photoelectric conversion of the object light led by the imaging optical unit includes steps of: 
     forming a plurality of the imaging elements on one surface of an silicon wafer; 
     disposing at least a portion of the imaging optical unit to face the light receiving pixels of non-defective imaging elements respectively; 
     cutting the silicon wafer into each imaging element; 
     placing a plurality of the imaging elements having been cut along with at least the portion of the imaging optical unit; 
     connecting the substrate with the plurality of the imaging elements electrically; 
     molding the plurality of the imaging elements sealed by the substrate and at least some of the imaging optical units with a resin integrally; and 
     separating the molded substrate into each imaging element by cutting. 
     According to the present invention, by cutting the silicon wafer into each imaging element and placing a plurality of the imaging elements on a substrate, non-defective imaging elements can be put into subsequent processes. In addition, by judging the defective elements before cutting, the imaging optical units to be combined with the imagine elements are saved, thus the imaging device can be manufactured at a low cost. 
     The imaging device manufacturing method described in claim  2  is based on that described in claim  1  is further characterized in that at least the portion of the imaging optical unit is a lens and a lens frame to retain the lens. For example, in order to passing through a solder reflow bath, a glass lens superior in heat resistance is used in the imaging optical unit. However, since the glass lens has an inferior molding property compared to that of the plastic lens, it is difficult to protrude a flange section in an optical axis direction. Thus the imaging optical unit is formed by installing the glass lens in the lens frame in advance, then the above imaging optical units are respectively disposed so as to face the light receiving pixel section of the imaging element, whereby a distance between the lens and the imaging element can be adjusted accurately. 
     The imaging device manufacturing method described in claim  3  based on that described in claim  1  is further characterized in that at least a portion of the imaging optical units is a lens frame to retain the lens. After the lens frame is disposed so as to face the light receiving pixel section of the imaging element, by installing the lens, a distance between the lens and the imaging element can be adjusted accurately. 
     The imaging device manufacturing method described in claim  4  based on that described in any one of claims  1  to  3  is further characterized in that the imaging optical unit is provided with a glass lens. 
     The imaging device described in claim  5  is an imaging device disposed on a substrate having: an imaging element, having a light receiving surface on which pixels are installed, disposed on the substrate; a lens to from an object image on the light receiving surface of the imaging element; and a lens frame to retain the lens, wherein the imaging element and the lens frame are molded integrally with a resin, thereby being manufactured at a low cost. 
     The portable terminal described in claim  6  is characterized in that the imaging device described in claim  5  is installed therein. 
     Effect of the Invention 
     According to the present invention, there are provided the manufacturing method capable of manufacturing the lower cost imaging device and the portable terminal using the imaging device thereof. 
    
    
     
         FIG. 1   a  to  1   d  are schematic diagrams showing processes of a manufacturing method of an imaging device related to the present embodiment in a preceding period. 
         FIGS. 2   a  to  2   d  are schematic diagrams showing processes of a manufacturing method of an imaging device related to the present embodiment in a latter period. 
         FIG. 3  is a cross-sectional view showing an imaging device manufactured in the above manufacturing processes. 
         FIG. 4  is an external view of a mobile phone  100  representing an exemplary portable terminal having an imaging device  50 . 
         FIG. 5  is a block-diagram of control of a mobile phone  100 . 
         FIG. 6  is a cross-sectional view equivalent to that in  FIG. 3  related to an exemplary variation of the present embodiment. 
     
    
    
     DESCRIPTION OF THE SYMBOLS 
       11  silicon wafer 
       12  imaging element 
       13  adhesive 
       14  lens frame 
       15  spacer 
       19  dicing blade 
       21  substrate 
       21   b  external electrode 
       50  imaging device 
       60  operation button 
       71  upper housing 
       72  lower housing 
       73  hinge 
       80  wireless communication section 
       91  memory section 
       100  mobile phone 
       101  control section 
     D 1 , D 2  display screen 
     F IR cut filter 
     ID terminal 
     LB lens 
     MD resin material 
     OU imaging optical unit 
     YB wire bonding 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An embodiment of the present invention will be described with reference to the drawings.  FIG. 1   a  to  1   d  are schematic diagrams showing processes of the manufacturing method of the imaging device related to the present embodiment in a preceding period. The left figures show outlined total views of a wafer in each status, and right figures are outlined cross-sectional views of a single imaging element in the wafer. 
     First, a plurality of imaging elements  12  are formed on one surface of the silicon wafer  11  shown by  FIG. 1   a . More specifically, By repeating known film forming processes such as a photo lithography process, an etching process and an impurity addition process, a transition electrode, an isolation film, and wiring are formed in a multilayer structure, and the plurality of the imaging elements  12  are formed in a shape of an array. The above imaging elements  12  are, for example, CCD (Charge Coupled Device) type image sensors, and CMOS (Complementary Metal-Oxide Semiconductor) type image sensors. 
     Alongside the above, the imaging optical unit OU is assembled. As the cross-sectional view in  FIG. 1   c  shows, the imaging optical unit OU is configured with a lens frame  14  in a shape of a rectangular tubular, an IR cut filter F disposed under the lens frame  14 , a glass lens LB disposed above the lens frame  14  and a spacer  15  disposed between IR cut filter F and the lens LB, which are bonded each other. 
     Further, chips of image elements  12  on the silicon wafer  11  are examined to distinguish defectives from non-defectives (NG in  FIG. 1   a  to  1   d  are defectives). Next, as  FIG. 1   b  shows, an adhesive  13  is applied onto only vicinities of all the imaging elements  12  which have been judged to be non-defectives. The adhesive  13  is applied onto a position except a light receiving pixel area of the imaging element  12 . Also, by adjusting application amount of the adhesive, a distance between the imaging optical unit OU (for example, the lens LB) which is bonded above the light receiving pixel area of the imaging element  12  and the imaging element  12  is determined. 
     Incidentally, distinguishing of the chips of the imaging element  12 , i.e. non-defectives from defectives is carried out using semiconductor examination apparatus commercially available. The chip is judged as a non-defective if defects are not found. The followings are confirmed as examination items; chipping of wiring patterns, existence of burrs at time of dicing, a width and a pitch of the wiring pattern, existence of flaws, taint and crack, and adhesion of foreign matters. 
     After that, as  FIG. 1   c  shows, the imaging optical unit OU is placed on the adhesive applied so as to be bonded. By bonding the imaging optical unit OU, the light receiving pixel area of the imaging element  12  is sealed by the lens frame  14  and the IR cut filter F. 
     Next, as  FIG. 1   d  shows, the silicon wafer  11  is cut into individual imaging elements by a dicing saw  19 . Whereby, individual chips of the imaging elements  12 , wherein the light receiving pixel area is sealed by the image optical unit OU, are formed. 
     Thus, since only non-defective imaging elements  12  are combined with the imaging optical units, the imaging optical unit OU is not wasted and a yield rate can be enhanced. 
       FIGS. 2   a  to  2   d  are schematic diagrams showing processes of the manufacturing method of an imaging device related to the present embodiment in a later process. A plurality of the chips of the imaging element  12 , wherein the chips of the imaging elements  12  are bonded respectively with the imaging optical units OU, are lined up and placed on the substrate  21 . On the substrate  21 , a plurality of wires corresponding to individual chips of the imaging element  12  are formed so that the plurality of the chips of the imaging element  12  can be placed thereon. 
     Next, as  FIG. 2   b  shows, the chip of the imaging element  12  and the substrate  21  are electrically connected through wire bonging YB. On the other surface of the substrate  21 , a plurality of external electrodes  21   b  (for example, solder ball) used for connecting with other unillustrated control substrates are formed. Whereby, input and output of signals between the other unillustrated control substrates in connection with the substrate  21  and the imaging element  12  are possible. 
     After that, as  FIG. 2   c  shows, a resin material MD is filled on an imaging element  12  side surface of the substrate  21  so as to cover an outer circumference of the imaging optical unit OU as the figure shows, and the imaging optical unit OU is molded integrally in the way that only the image surface side of the lens LB is exposed. 
     Further, by cutting and separating the imaging optical unit OU molded integrally, the imaging element  12  and the substrate  21  along the broken lines shown in  FIG. 2   b , individual imaging devices  50  shown by  FIG. 2   e  are separated and completed. 
     As described above, in the present example, in the processes of cutting the silicon wafer into the individual chips of the imaging elements and placing the plurality of the chips of the imaging elements on the substrate, only non-defective chips can be used for the latter process, whereby the manufacturing method to manufacture the imaging device at low cost can be obtained. 
       FIG. 3  is a cross-sectional view showing the imaging device manufactured in the aforesaid manufacturing method. As  FIG. 3  shows, the imaging device  50  is provided with the imaging element  12 . In  FIG. 1 , in the imaging element  12 , at a center section of a light receiving side plane thereof, a photoelectric conversion section (unillustrated) representing a light receiving pixel section where the pixels (photoelectric conversion elements) are disposed two dimensionally is formed. The photoelectric conversion section performs photoelectric conversion of an object image formed through the lens LB, and at a periphery thereof, a signal processing circuitry section (unillustrated) is formed. The signal processing circuitry section is provided with a drive circuitry section to drive each pixel sequentially and to obtain a signal charge, an A/D conversion section to convert each signal charge into a digital signal and a signal processing section to create an imaging signal output using the digital signal thereof which are not illustrate and are connected with the substrate  21  through the terminal (sensor pad) on the surface via wiring bonding YB so as to communicate signals with an outside. 
     The imaging element  12  converts the signal charge form the photoelectric conversion section into an image signal and outputs to a prescribed circuitry on the substrate  21 . Incidentally, the imaging element is not limited to the CMOS type imaging sensor, thus other imaging elements such as a CCD can be used. 
     In  FIG. 3  an end section of the lens frame  14  in a tubular shape formed with a black resin contacts with a periphery of the imaging element  12 , via a resin having a prescribed thickness. At an upper part of inside the lens frame, a glass lens LB is formed which is in contact with an upper surface of the IR cut filter F via a spacer  15  having a prescribed thickness. The lens LB is in contact with a lower surface of an upper flange section  14   a  of the lens frame  14 . Here, by adjusting a length L 1  (a length of the leg section of the lens frame  14 ) from the lower surface of the upper flange section  14   a  to a bottom end of the lens frame  14 , the lens LB and the imaging element  12  can be positioned in an optical axis direction within the prescribed range, thus focusing work can be simplified. Incidentally, the prescribed range means the range of about ±F×2P (F: lens F number, P: pixel pitch of imaging element) in an air equivalent length, within which a deviation between the light receiving surface of the imaging element  12  and an imaging point of the lens LB falls. 
     A portable terminal provided with the imaging device  50  manufactured as above will be described.  FIG. 4  is an external view of a mobile phone  100  representing an example of a portable terminal provided with the imaging device  50 . 
     The mobile phone  100  shown by  FIG. 4  has an upper housing  71  as a case provided with display screens D 1  and D 2  and a lower housing  72  provided with operation buttons  60  representing an input section which are connected via a hinge  73 . The imaging device  50  is installed blow the display screen D 2  in the upper housing  71  so that the imaging device  50  can capture light from an outer surface side of the upper housing  71 . 
     Meanwhile, the position of the imaging device can be above the display screen D 2  or at a side surface in the upper housing  71 . The mobile phone is not limited to a folding type. 
       FIG. 5  is a control block diagram of the mobile phone  100 . As  FIG. 5  shows, the imaging device  50  is connected to the control section  101  of the mobile phone  100  via the external electrode  21   b  so as to output image signals such as a brightness signal and a color difference signal to the control section  101 . 
     On the other hand, the mobile phone  100  to perform overall control for each section is provided with a control section (CPU)  101  to execute a program in accordance with each process, the operation buttons  60  representing the input section to input instructions such as telephone numbers, display screens D 1  and D 2  to display prescribed data and photographed images, a wireless communication section  80  to realize various data communication between an external server, a memory section (ROM)  91  to store various necessary data such as a system program for the mobile phone  100 , various processing programs and an ID of the terminal, and a temporally memory section (RAM)  92  to temporarily store various processing programs, processed data to be executed by the control section  101  and image data captured by the imaging device  50  which is used as a work area. 
     Also, the image signal inputted from the imaging device  50  is stored in the memory section  91  through the control section  101  of the mobile phone  100 , and displayed on the display screen D 1  or D 2 , furthermore, transmitted to an outside as image information via the wireless communication section  80 . 
       FIG. 6  is a cross-sectional view which is similar to  FIG. 3  related to an exemplary variation of the present embodiment. In  FIG. 6 , a periphery of the lens frame  14  representing a part of the image optical unit OU is molded with the resin material MD and integrated with the imaging element  12  and the substrate  21 . A female thread  14   b  is formed inside the lens frame  14 . On the other hand, on the outer circumference of a holder  14 ′ in a shape of a cylinder retaining the lens LB, a male thread  14   c  is formed. By engaging the female thread  14   b  with the male thread  14   c , the lens LB is mounted on the lens frame  14  via the holder  14 ′. When this occurs, by adjusting the engaging amount of the threads of the holder  14 ′, the lens LB and the imaging element  12  are position in the light axis direction within the prescribed range. 
     As above, while the present invention has been described with reference to the embodiments, it is to be understood that changes and variations may be made without departing from the spirit or scope of the appended claims. For example, by bonding only the lens frame  14  onto the silicon wafer  11  in advance, the IR cut filter F and the lens LB can be installed onto the lens frame  14  from an object side after completion of molding. Or, the IR cut filter is no always necessary to be provided. For example, the filter can be omitted by forming an IR cut film on the optical surface of the lens LB.