Abstract:
A method for inspecting a solid-state image pickup device by irradiating a solid-state image pickup device with measuring light emitted from a light source, wherein the light source is a surface light emitter comprising a plurality of pixels each including a combination of a red LED, a green LED and a blue LED.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a method and apparatus for irradiating measuring light onto a solid-state image pickup device such as a CCD image sensor and a CMOS image sensor to inspect its electrical characteristics and in particular to an inspection method and inspection apparatus that allows downsizing of apparatus and high-speed inspection.  
         [0003]     2. Description of the Related Art  
         [0004]     When the electrical properties of a solid-state image pickup device, measuring light is irradiated onto the solid-state image pickup device. Related art inspection apparatus uses a halogen lamp as a light source and passes the light from the light source through a color filter to generate measuring light of a color necessary for measurement and through an ND filter to perform intensity adjustment of measuring light.  
         [0005]     A halogen lamp has a short service life so that it must be changed frequently, which leads to higher costs. A mechanism for switching between color filters and introduction of an ND filter adds to the apparatus size. Further, filter switching at inspection takes time and a control signal is transmitted/received via GPIB (General Purpose Interface Bus: IEEE-488) communications thus resulting in lower control response.  
         [0006]     JP-A-2-90645 discloses apparatus for inspecting a solid-state image pickup device using a light-emitting diode (LED) as a light source. By using an LED as a light source, the problems with the halogen lamp are solved.  
         [0007]     While the color of the measuring light is not described in JP-A-2-90645, the technique described in JP-A-2004-213986, that is, the technique for controlling the value of a current applied to a red (R) LED, a green (G) LED and a blue (B) LED to perform color control of illumination light may be applied to apparatus for inspecting an solid-state image pickup device described in JP-A-2-90645 to do without a color filter. This downsizes the apparatus by the volume of the color filter and saves the time required for color filter switching during inspection.  
         [0008]     The red LED, green LED and blue LED are respectively point light sources. Having certain sizes, the LEDs must be arranged in separate positions in the same inspection apparatus. It is thus necessary to provide a condensing optical system and light scattering means (obscure glass described in JP-A-2-90645) to keep uniform the additive color of light across the light receiving face of the solid-state image pickup device.  
         [0009]     As mentioned above, a condensing optical system and light scattering means are required in inspection apparatus even when an LED is used as a light source for the inspection apparatus. Thus the inspection apparatus cannot be further downsized.  
       SUMMARY OF THE INVENTION  
       [0010]     An object of the invention is to provide a method and apparatus for inspecting a solid-state image pickup device capable of downsizing the apparatus as well as allowing quick inspection.  
         [0011]     The invention provides a method and apparatus for inspecting a solid-state image pickup device wherein the method and apparatus use, in the inspection of a solid-state image pickup device by irradiating measuring light emitted from a light source, a surface light emitter composed of plural pixels each including a combination of a red LED, a green LED and a blue LED as the light source.  
         [0012]     The surface light emitter for the inventive method and apparatus for inspecting a solid-state image pickup device may comprise an organic EL device.  
         [0013]     The surface light emitter for the inventive method and apparatus for inspecting a solid-state image pickup device may be provided integrally with a probe card for causing a probe pin to abut against the electrode pad of the solid-state image pickup device above the center through hole of the prove card.  
         [0014]     The surface light emitter for the inventive method and apparatus for inspecting a solid-state image pickup device may be provided in a lid body which is arranged above a socket, to which a solid-state image pickup device package is attached, and is capable of opening and closing an area above the socket. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1  is a schematic cross-sectional view of solid-state image pickup device inspection apparatus according to the first embodiment of the invention;  
         [0016]      FIG. 2  is a schematic surface view of a semiconductor wafer shown in  FIG. 1 ;  
         [0017]      FIG. 3  is a schematic plan view of the semiconductor wafer side of probe card shown in  FIG. 1 ;  
         [0018]      FIG. 4  is a schematic cross-sectional view of a single pixel of the surface light emitter shown in  FIG. 1 ;  
         [0019]      FIG. 5  is a schematic cross-sectional view of solid-state image pickup device inspection apparatus according to the second embodiment of the invention;  
         [0020]      FIG. 6  is a schematic cross-sectional view of the solid-state image pickup device inspection apparatus shown in  FIG. 5  accommodating a package as a target of inspection; and  
         [0021]      FIG. 7  is a schematic cross-sectional view of three pixels of a surface light emitter different from that shown in  FIG. 4 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]     An embodiment of the invention will be described referring to drawings.  
       First Embodiment  
       [0023]      FIG. 1  is a schematic cross-sectional view of solid-state image pickup device inspection apparatus according to the first embodiment of the invention. On the surface of a disc-shaped semiconductor wafer  1  as a target of inspection, for example as shown in  FIG. 2  are formed via an integrated circuit technique a large number of ( 37  in the illustrated example) solid-state image pickup devices  2 . A solid-state image pickup device inspection apparatus  10  according to the intention is designed to inspect individual solid-state image pickup devices in order while moving with respect to the semiconductor wafer  1 .  
         [0024]     The solid-state image pickup device inspection apparatus  10  includes a disc-shaped probe card  11  shown in  FIG. 3 . In the center of the probe card  11  is made a rectangular through hole  12 . From the sides of the through hole  12  are protruded a large number of probe pins  13  extending toward the center and the semiconductor wafer  1 .  
         [0025]     To the side opposite to the semiconductor wafer  1  at the center of the probe card  11  is fixed a bottomed cylindrical member  14  for shielding the through hole  12  from light. To the internal bottom surface of the bottomed cylindrical member  14  is attached a surface light emitter  15 . In the illustrated example, in the bottomed cylindrical member  14  is provided a lens  16  for condensing the light emitted from the surface light emitter  15 .  
         [0026]     The surface light emitter  15  is connected to probe card  11  via a power supply line  17 . The solid-state image pickup device inspection apparatus  10  is connected to a tester (not shown) and communicates an inspection control signal and a detection signal between the tester and the probe card  11  as well as supplies a voltage pulse to the surface light emitter  15  via the power supply line  17 .  
         [0027]      FIG. 4  is a schematic cross-sectional view of a single pixel of the surface light emitter  15 . The surface light emitter  15  according to this embodiment is composed of numerous pixels arranged on a plane where each pixel includes a red color luminescent organic EL device  15   r,  a green color luminescent organic EL device  15   g  and a blue color luminescent organic EL device  15   b  in order to obtain full emitting light colors.  
         [0028]     The surface light emitter  15  includes: a transparent substrate  21 ; a transparent common negative electrode film  22  laminated on the transparent substrate  21 ; a red color luminescent organic EL layer  23   r,  a green color luminescent organic EL layer  23   g  and a blue color luminescent organic EL layer  23   b  laminated on the negative electrode film  22 ; and positive electrode films  24   r,    24   g,    24   b  respectively laminated on the organic EL layers  23   r,    23   g,    23   b.    
         [0029]     Such a surface light emitter  15  may be manufactured exclusively as a surface light emitter although for example an organic EL device of several tens of pixels already used as a display screen on the back of a digital still camera may be used as the surface light emitter  15 .  
         [0030]     In case a solid-state image pickup device  2  on the semiconductor wafer  1  is inspected using thus configured solid-state image pickup device inspection apparatus  10 , the semiconductor wafer  1  arranged below the inspection apparatus  10  are moved in horizontal direction to bring the solid-state image pickup device  2  as a target of inspection just below the through hole  12  in the probe card  11 . The inspection apparatus  10  is lowered with a transport mechanism (not shown) to cause a probe pin  13  to abut against the electrode pad (not shown) of the solid-state image pickup device  2  under a predetermined pin pressure.  
         [0031]     A tester (not shown) applies a voltage pulse across each of the positive electrode films  24   r,    24   g,    24   b  and the negative electrode film  22  of each pixel of the surface light emitter  15  via the power supply line  17 . Thus causes each organic EL layers  23   r,    23   g,    23   b  to emit red (R) light, green (G) light and blue (B) light respectively. The light is emitted as measuring light through the negative electrode film  22  and the transparent substrate  21  toward the solid-state image pickup device  2 .  
         [0032]     The voltage applied across the positive electrode film and the negative electrode film and the voltage pulse width are controlled by the tester (not shown) so that the light quantity of each color is controller and red light, green light and blue light are added and light of an arbitrary color-is emitted as measuring light. Each pixel of the surface light emitter  15  is formed minutely so that light of an arbitrary color is uniformly emitted from the light emitting face of the surface light emitter  15 .  
         [0033]     The measuring light is condensed by the condenser  16  and irradiated onto the light receiving face of the solid-state image pickup device  2  via the through hole  12 . The solid-state image pickup device  2  outputs on an electrode pad an output signal obtained by receiving the measuring light. The output signal is collected by the tester via the probe pin  13 .  
         [0034]     According to this embodiment, light of each color is obtained without using a color filter. A color filter or other switching mechanism is made unnecessary thus reducing the apparatus size. A surface light emitter is used to uniformly emit light of an arbitrary color. This makes it possible to irradiate uniform light onto a solid-state image pickup device without introducing light scattering means, thus further reducing the apparatus size.  
         [0035]     While a condenser  16  is used in the example shown in  FIG. 1 , the condenser  16  is also unnecessary as long as the light quantity of the surface light emitter  15  is sufficient, which further reduces the apparatus size.  
         [0036]     The inspection apparatus of this embodiment controls the color of the measuring light to an arbitrary color by simply controlling the voltage pulse. This eliminates the need for controlling the surface light emitter  15  via GPIB communications thereby allowing quick inspection.  
         [0037]     A configuration where the tester is capable of controlling the emitted color of individual pixels of the surface light emitter  15  allows inspection of the solid-state image pickup device  2  by causing the surface light emitter  15  to display (emit) an arbitrary color image.  
       Second Embodiment  
       [0038]      FIG. 5  is a schematic cross-sectional view of solid-state image pickup device inspection apparatus according to the second embodiment of the invention. While the solid-state image pickup device  2  on the semiconductor wafer  1  is inspected in the first embodiment shown in  FIG. 1 , the solid-state image pickup device inspection apparatus  30  inspects a solid-state image pickup device cut out from a semiconductor wafer and accommodated in a package  2 a. The same members as those in the first embodiment are given the same signs in the following description.  
         [0039]     The solid-state image pickup device inspection apparatus  30  according to this embodiment includes a disc-shaped card  11  connected to a tester (not shown). To the center of the disc-shaped card  11  is fixed an open-top type IC socket  31  connected to wiring (not shown) in the disc-shaped card  11 . To the IC socket  31  is detachably attached the package  2 a as a target of inspection accommodating a solid-state image pickup device.  
         [0040]     To the center of the disc-shaped card  11  is fixed a rectangular ring-shaped base  32  surrounding the IC socket  31 . On the ring-shaped base  32  is placed a bottomed cylindrical member (lid body)  14  for shielding the IC socket  31  from light. To the internal bottom surface of the bottomed cylindrical member  14  is attached the same surface light emitter  15  as in the first embodiment.  
         [0041]     One side of the opening side of the bottomed cylindrical member  14  is coupled to one side of the rectangular ring-shaped base  32  via a hinge  14   a.  This allows the bottomed cylindrical member  14  to rotate about the hinge  14   a  and allows the IC socket  31  placed in the center of the ring-shaped base  32  to be opened/closed by way of the bottomed cylindrical member  14 .  FIG. 6  shows a state where the bottomed cylindrical member  14  is opened to expose the solid-state image pickup device package  2   a  to external light.  
         [0042]     In case a solid-state image pickup device  2  in the package  2   a  is inspected using thus configured solid-state image pickup device inspection apparatus  30 , the bottomed cylindrical member  14  is opened as shown in  FIG. 6  to attach the package  2   a  as a target of inspection to the IC socket  31  and the bottomed cylindrical member  14  is closed as shown in  FIG. 1 .  
         [0043]     In the state of  FIG. 1 , a tester (not shown) applies a voltage pulse on the surface light emitter  15  via the power supply line  17  to perform light emission control of the surface light emitter  15 , same as in the first embodiment. Thus the surface light emitter  15  to emit measuring light of a uniform arbitrary color and the solid-state image pickup device in the package  2   a  receives measuring light condensed by the condenser  16 . The solid-state image pickup device in the package  2   a  outputs an output signal obtained by receiving measuring light to each terminal of the IC socket  31 . The output signal is collected by the tester.  
         [0044]     The solid-state image pickup device inspection apparatus according to this embodiment provides the same effect as the first embodiment. While the condenser  16  is used in this embodiment also, the condenser  16  is also unnecessary as long as the light quantity of the surface light emitter  15  is sufficient, which further reduces the apparatus size.  
         [0045]      FIG. 7  is a schematic cross-sectional view of three pixels of a surface light emitter whose light quantity has been increased. While the surface light emitter shown in  FIG. 4  arranges a red color luminescent organic EL device  15   r,  a green color luminescent organic EL device  15   g  and a blue color luminescent organic EL device  15   b  on a plane in each pixel, the counterpart shown in  FIG. 7  includes the red color luminescent organic EL device  15   r,  the green color luminescent organic EL device  15   g  and the blue color luminescent organic EL device  15   b  laminated in this order in each pixel. The positive electrode films and negative electrode films sandwiching the organic EL layers  23   r,    23   g,    23   b  are transparent electrode films in each pixel. Note that the positive electrode film  24   b  in the uppermost layer is not transparent in order to serve as a reflective film also.  
         [0046]     The configuration shown in  FIG. 7  obtains an emitted light quantity three times as large as that shown in  FIG. 4  as long as the area of the surface light emitter is the same.  
         [0047]     According to the invention, uniform light of an arbitrary color is emitted from a surface light emitter so that a color film or light scattering means are no more necessary thus reducing the apparatus size. It is possible to quickly make control to obtain an arbitrary color thus reducing the inspection time.  
         [0048]     The solid-state image pickup device inspection apparatus according to the invention has a compact size and allows quick inspection so that it is useful for inspection of an image sensor such as a CCD and a CMOS.  
         [0049]     The entire disclosure of each and every foreign patent application from which the benefit of foreign priority has been claimed in the present application is incorporated herein by reference, as if fully set forth: