Patent Publication Number: US-2010126289-A1

Title: Method of mounting contactor

Description:
TECHNICAL FIELD 
     The present invention relates to a method of mounting a contactor on a probe board, the contactor is for electrical connection with an input/output terminal of a semiconductor integrated circuit device or other electronic device (hereinafter also referred to as representatively as an “IC device”) in a probe card establishing electrical connection between an IC device when testing an IC device. 
     BACKGROUND ART 
     A large number of semiconductor integrated circuit devices are built into a silicon wafer or other semiconductor wafer, then are diced, bonded, packaged, and otherwise processed to form finished electronic devices. Such IC devices are subjected to operational tests before shipment. These IC tests are run in the state of the finished products and in the state of the wafer. 
     As the probe needles for establishing electrical connection with an IC device when testing the IC device in the wafer state, ones made at a semiconductor wafer using photolithography or other semiconductor production technology (hereinafter also referred to simply as “silicon finger contactors”) have been known in the past (for example, see Patent Literature 1). Each silicon finger contactor comprises: a base part attached to a probe board; beam parts with rear end sides provided at the base part and with front end sides sticking out from the base part in finger shapes (comb shape); and conductive parts formed on the surfaces of the beam parts and electrically connecting with input/output terminals of an IC device. 
     When using such silicon finger contactor to produce a probe card, the probe board is coated with an adhesive at predetermined position, the base part of the silicon finger contactor is positioned at the coated position, and the adhesive is cured to mount the silicon finger contactor on the board. 
     This series of mounting steps is performed using a dedicated mounting system. Image processing technology etc. is used to position each silicon finger contactor  60  on the board  51 . Specifically, as shown in  FIG. 8 , first the positions of first marks  51   d  actually provided on the board  51  and the positions of second marks  61   b  provided on the silicon finger contactor  60  are recognized, a midpoint M 1  is calculated from the positions of the first marks  51   d , and a midpoint M 2  is calculated from the positions of the second marks  61   b . Next, the silicon finger contactor  60  is positioned on the board  51  so that the midpoint M 2  of the marks  61   b  of the contactor  60  is positioned a predetermined distance L away from the midpoint M 1  of the first marks  51   d.    
     A large number of silicon finger contactors  60  are mounted on the board  51  by the above procedure, but as shown in  FIG. 8 , the processing tolerance of the first marks  51   d  is about ±10 μm or so, so there is a maximum 20 μm or so variation between adjoining first marks  51   d . On the other hand, the input/output terminals at the wafer under test side have a narrow pitch of several tens to several hundreds of μm, so there is a good possibility of missed contact between the contactors  60  and the input/output terminals on the wafer under test at the time of testing an IC device. 
     As factors influencing the mounting precision, in addition to the processing precision of the first marks on the board, the error in recognition of the marks, operating precision, etc. of the mounting system may be mentioned, but these precisions can be made within ±several μm, so the processing precision of the first marks has the greatest effect on the mounting precision. 
     Further, along with the greater size of the boards on which the silicon finger contactors are mounted and the greater number of silicon finger contactors mounted, the processing error of the first marks cumulates, so the effect of the processing precision of the first marks on the mounting precision tends to be larger.
     Patent Literature 1: Japanese Patent Publication (A) No. 2000-249722   Patent Literature 2: Japanese Patent Publication (A) No. 2001-159642   Patent Literature 3: International Publication No. 03/071289 pamphlet   

     SUMMARY OF INVENTION 
     Technical Problem 
     The problem to be solved by the present invention is to provide a method of mounting a contactor able to mount a contactor on a board with a high precision. 
     Solution to Problem 
     To achieve the above object, according to the present invention, there is provided a method of mounting a contactor on a board, the contactor for electrical contact with input/output terminal of a device under test at the time of testing the device under test, the method of mounting a contactor comprising: a first recognition step of recognizing a position of a reference point provided on the board; a first calculation step of recognizing a position of a first mark provided on the board for showing a position for mounting the contactor and calculating an actual relative position of the first mark with respect to the reference point; a second calculation step of calculating a theoretical relative position in design of the first mark with respect to the reference point; a third calculation step of calculating a relative amount of deviation of the actual relative position with respect to the theoretical relative position on the basis of the actual relative position calculated in the first calculation step and the theoretical relative position calculated in the second calculation step; a second recognition step of recognizing the positions of the first mark; a specifying step of specifying a mounting position of the contactor on the board on the basis of the amount of deviation calculated in the third calculation step and the position of the first mark recognized in the second recognition step; and a mounting step of mounting the contactor at the position specified in the specifying step. 
     While not particularly limited in the invention, preferably the specifying step comprises: calculating the theoretical position in design of the first mark on the basis of the position of the first mark recognized in the second recognition step and the amount of deviation calculated in the third calculation step; and specifying the theoretical position as the mounting position of the contactor on the board. 
     While not particularly limited in the invention, preferably the method further comprises a third recognition step of recognizing a position of a second mark provided on the contactor for recognizing the position of the contactor, wherein the mounting step comprises mounting the contactor on the board so that the second mark is positioned at the mounting position or the second mark is positioned a predetermined distance away from the mounting position. 
     While not particularly limited in the invention, preferably the first recognition step and the first calculation step respectively comprise recognizing the position of the reference point and the positions of the first mark by a first measurement system, and the second recognition step and the third recognition step respectively comprise recognizing the position of the first mark and the position of the second mark by a second measurement system different from the first measurement system. 
     While not particularly limited in the invention, preferably, when mounting a plurality of the contactors on the same board, the respective first recognition steps comprise recognizing the position of the same reference point. 
     While not particularly limited in the invention, preferably the method further comprises a coating step of coating an adhesive on the mounting position specified in the specifying step. 
     While not particularly limited in the invention, preferably the contactor has a base part fixed to the board, beam parts with rear end sides provided at the base part and front end sides sticking out from the base part, and conductive parts formed on surfaces of the beam parts and electrically connecting with input/output terminals of the device under test, one the base part is provided with a plurality of the beam parts, and the second mark is provided at the base part. 
     ADVANTAGEOUS EFFECTS OF INVENTION 
     In the present invention, a reference point at a board is provided, a relative position of an actual first mark (actual relative position) and relative position of a first mark in the design (theoretical relative position) with respect to the reference point are calculated, the relative amount of deviation of the actual relative position with respect to the theoretical relative position is calculated, and this amount of deviation is considered when specifying the mounting position of the contactor on the board. Due to this, it is possible to cancel out the processing error occurring when providing the first mark on the board, so it is possible to accurately mount the contactor on the board. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic cross-sectional view of an electronic device test system in an embodiment of the present invention. 
         FIG. 2  is a cross-sectional view showing a probe card in an embodiment of the present invention. 
         FIG. 3  is a bottom view showing a probe card in an embodiment of the present invention. 
         FIG. 4  is a cross-sectional view showing a silicon finger contactor in an embodiment of the present invention. 
         FIG. 5  is a plan view showing a silicon finger contactor in an embodiment of the present invention. 
         FIG. 6  is a flow chart showing a method of mounting a contactor in an embodiment of the present invention. 
         FIG. 7A  is a partial plan view of a mount base for explaining steps S 11  to S 14  in  FIG. 6 . 
         FIG. 7B  is a partial plan view of a mount base for explaining steps S 22  to S 27  in  FIG. 6 . 
         FIG. 7C  is a side view showing step S 24  in  FIG. 6 . 
         FIG. 7D  is a side view showing step S 27  in  FIG. 6 . 
         FIG. 7E  is a side view showing step S 28  in  FIG. 6 . 
         FIG. 8  is a plan view showing a conventional method of mounting a contactor. 
     
    
    
     REFERENCE SIGNS LIST 
     
         
           1  . . . electronic device test system 
           10  . . . test head 
           50  . . . probe card 
           51  . . . mount base 
           51   c  . . . reference point 
           51   d  . . . first mark 
         M 1  . . . midpoint 
           51   e  . . . first mark in design 
         M 0  . . . midpoint 
           51   f  . . . mounting position 
           52  . . . bonding wire 
           53  . . . support column 
           54  . . . limiter 
           55  . . . circuit board 
           56  . . . base member 
           57  . . . stiffener 
           60  . . . probe needle 
           61  . . . base part 
           61   b  . . . second mark 
         M 2  . . . midpoint 
           62  . . . beam part 
           63  . . . conductive layer 
           80  . . . prober 
         W . . . semiconductor wafer 
         Δm . . . amount of deviation 
       
    
     EMBODIMENTS OF INVENTION 
     Below, an embodiment of the present invention will be explained based on the drawings. 
     First, the configuration of an electronic device test system comprising a probe card to which a method of mounting a contactor in the present embodiment is applied will be briefly explained. 
       FIG. 1  is a schematic cross-sectional view showing the configuration of an electronic device test system in an embodiment of the present invention,  FIG. 2  is a cross-sectional view of a probe card in an embodiment of the present invention,  FIG. 3  is a bottom view of a probe card in an embodiment of the present invention,  FIG. 4  is a cross-sectional view of a silicon finger contactor in an embodiment of the present invention, and  FIG. 5  is a plan view of a silicon finger contactor in an embodiment of the present invention. 
     The electronic device test system  1  in the present embodiment is a system for testing the electrical characteristics of an IC device built in a semiconductor wafer W made of for example silicon (Si) etc. This electronic device test system  1 , as shown in  FIG. 1 , comprises: a test head  10  electrically connected to a tester (not shown) for testing an IC device via a cable (not shown); a probe card  50  for electrically connecting an IC device on the semiconductor wafer W and the test head  10 ; and a prober  80  pushing the semiconductor wafer W against the probe card  50 . 
     The probe card  50 , as shown in  FIG. 1  to  FIG. 3 , comprises: a large number of silicon finger contactors  60  for electrical contact with input/output terminals of an IC device built in a semiconductor wafer W; a mount base  51  on which the silicon finger contactors are mounted; a circuit board  55  having interconnect patterns (not shown) electrically connected to the silicon finger contactors  60  via bonding wires  52 ; a base member  56  and stiffener  57  for reinforcing the probe card  50 ; support columns  53  for supporting the mount base  51 ; and limiters  54  suppressing deformation of the mount base  51 , and is connected via a HIFIX  11  to the test head  10 . 
     Each silicon finger contactor  60 , as shown in  FIG. 4  and  FIG. 5 , comprises: a base part  61  fixed to the mount base  51 ; beam parts  62  with rear end sides provided at the base part  61  and with front end sides sticking out from the base part  61 ; and conductive layers  63  formed at the surfaces of the beam parts  62 . 
     The base part  61  and beam parts  62  of this silicon finger contactor  60  are made from a silicon substrate using photolithography or other semiconductor production technology. As shown in  FIG. 5 , a single base part  61  is provided with a plurality of (in this example, four) beam parts  62  in finger shapes (comb shape). By using semiconductor production technology to produce the contactor  60  in this way, it is possible to easily match the pitch between the beam parts  62  with the narrow pitch between the input/output terminals built in the wafer W under test. Note that, in the present invention, the number of the beam parts  62  provided at one base part  61  may be freely set. 
     As shown in  FIG. 4 , a step  61   a  is formed at the rear end of the base part  61 . By controlling the ratio of the depth and length of this step  61   a , it is possible to freely set the slant angle β of the contactor  60  with respect to the mount base  51 . Note that, the smaller this slant angle β, the more preferable. 
     Further, in the present embodiment, as shown in  FIG. 5 , the both ends of the top surface of the base part  61  are provided with second marks  61   b  used when mounting the contactor  60  on the mount base  51 . Each second mark  61   b  is, for example, composed by forming a through hole or metal plating layer at the base part  61 . 
     An insulating layer  62   a  is formed on the top surfaces of the beam parts  62  for electrically insulating the conductive layer  63  from other parts in the silicon finger contactor  60 . This insulating layer  62   a  is, for example, made of a SiO 2  layer or boron-doped layer. 
     The conductive layer  63  is formed on the surface of this insulating layer  62   a . As the material composing the conductive layer  63 , for example, tungsten, palladium, rhodium, platinum, ruthenium, iridium, nickel, or other metal material may be mentioned. 
     The thus configured silicon finger contactor  60 , as shown in  FIG. 4 , is fixed by an adhesive  51   b  on the mount base  51  and the front ends face input/output terminals of an IC device built into the wafer W under test. As the binder  51   b  for fixing the silicon finger contactor  50  to the mount base  51 , for example, an ultraviolet light curing type adhesive etc. may be mentioned. 
     The mount base  51  is a circular shaped board made of a material having somewhat larger efficient thermal expansion than that of the wafer W under test. As the specific material composing the mount base  51 , for example, ceramic, kovar, tungsten carbide, stainless invar steel, etc. may be mentioned. Note that, from the viewpoints of ease of processing and inexpensiveness, it is preferable to compose the mount base  51  by a ceramic board. By making the mount base  51  out of a material having a suitable efficient thermal expansion with respect to the wafer W under test, it is possible to reduce the fluctuations in the contact pressures of the contactors  60  caused due to application of temperature and the positional deviation between the front ends of the contactors  60  and the terminals on the wafer W under test. 
     As shown in  FIG. 2  and  FIG. 3 , rectangular through holes  51   a  running through the mount base  51  from the front surface to the back surface are formed behind the contactors  60  at the mount base  51 . Bonding wires  52  connected to the conductive layers  63  of the contactors  60  are connected via the through holes  51   a  of the mount base  51  to terminals (not shown) on the circuit board  55 . The contactors  60  and the circuit board  55  can be connected by bonding wires  52  given slack so as to allow for the difference in thermal expansion of the mount base  51  and circuit board  55 . 
     Further, in the present embodiment, as shown in  FIG. 3 , a reference point  51   c  used when mounting the contactors  60  on the mount base  51  is provided at a predetermined position of the mount base  51 . This reference point  51  is, for example, composed of a through hole formed in the mount base  51 . 
     The circuit board  55  is for example a circular board made of a glass epoxy resin. Terminals (not shown) to which the bonding wires  52  are connected are formed at the bottom surface of the circuit board  55 . Contactors  55   c  connecting with connectors  12  at the HIFIX  11  side are provided at the top surface of the circuit board  55 . Interconnect patterns (not shown) electrically connecting the terminals of the bottom surface and connectors  55   c  of the top surface are formed inside the circuit board  55 . As the connectors  12 ,  55   c , for example ZIF (Zero Insertion Force) connectors may be used. First through holes  55   a  for passing the support columns  53  and second through holes  55   b  for passing the limiters  54  are formed at the circuit board  55  so as to pass through from the front surface to the back surface. 
     A base member  56  and stiffener  57  are provided on the top surface of the circuit board  55  in order to reinforce the probe card  50 . The base member  56  and the stiffener  57  are fixed by for example bolting. Further, the stiffener  57  and the circuit board  55  are fixed at the outer peripheral part of the board  55  by for example bolting. On the other hand, the base member  56  and the circuit board  55  are not directly fixed, so the circuit board  55  is unconstrained at its center part and deformation of the circuit board  55  due to heat expansion of the circuit board  55  is not directly transmitted to the base member  56 . As the material composing the base member  56  and stiffener  57 , for example, stainless steel, carbon steel, etc. may be mentioned. 
     The support columns  53  are columnar members for supporting the mount base  51 . As shown in  FIG. 2 , first ends of the support columns  53  are fixed to the mount base  51 , while the other ends of the support columns  53  are directly fixed through the first through holes  55   a  to the base member  56 . By directly fixing the support columns  53  to the base member  56 , it is possible to prevent the effects of heat expansion of the circuit board  55  from causing fluctuations in the positions of the support columns  53 . As the material composing the support columns  53 , for example stainless invar steel etc. may be mentioned. As the technique for fixing the support columns  53  to the mount base  51  or base member  56 , for example bolting, bonding, etc. may be mentioned. 
     In the present embodiment, the mount base  51  on which the contactors  60  are mounting and the circuit board  55  on which interconnect patterns electrically connected to the contactors  60  are formed are made from separate boards, and the mount base  51  and the circuit board  55  are noncontact, so even if the circuit board  55  deforms due to heat expansion etc., the deformation will not be transmitted to the mount base  51  mounting the contactors  60 , and fluctuation of the contact pressure and positional deviation of the contactors  60  can be reduced. 
     The limiters  54  are columnar members for preventing deformation of the mount base  51  when pressing the wafer W against the contactors  60 . As shown in  FIG. 2 , first ends of the limiters  54  contact the back surface of the mount base  51  or are positioned near the back surface, while the other ends of the limiters  54  are directly fixed through the second through holes  55   b  to the base member  56 . As the material composing the limiters  54 , in the same way as the support column  53 , for example, stainless invar steel etc. may be mentioned. As the technique for fixing the limiters  54  to the base member  56 , for example bolting, bonding, etc. may be mentioned. The limiters  54  are designed to closely contact the back surface of the mount base  51  and keep the mount base  51  from deforming to the circuit board  55  side when the wafer W is pressed against the probe card  50 . Note that, when the mount base  51  has sufficient strength so as not to deform when pressing the wafer W against the contactors  60 , the limiters  54  are unnecessary. 
     The thus configured probe card  50 , as shown in  FIG. 1 , is fixed to a ring-shaped holder  70  in posture that the contactors  60  face to lower side via the center opening  71 . The holder  70  is fixed to the ring-shaped adapter  75  in the state holding the probe card  50 . Further, the adapter  75  is fixed to the opening  82  formed in the top plate  81  of the prober  80 . This adapter  75  is for adapting a different size probe card due to the type of the wafer W under test and the shape of the test head  10  to the opening  82  of the prober  80 . The probe card  50  side and the HIFIX  11  side, as shown in  FIG. 1 , are mechanically coupled by mutual engagement of hooks  13  provided at the bottom surface of the HIFIX  11  and hooks  76  provided at the adapter  75 . 
     The HIFIX  11  is attached to the bottom part of the test head  10 . Connectors  12  to which coaxial cables are connected are provided at the bottom surface of this HIFIX  11 . By connecting the connectors  12  of the test head  10  side and the connectors  55   c  provided at the top surface of the circuit board  55  of the probe card  50 , the test head  10  and the probe card  50  are electrically connected. 
     The prober  80  can hold the wafer W by a vacuum chuck and has a conveyor arm  83  enabling the held wafer W to be moved in the XYZ-directions and can convey the wafer W inside the prober  80 . Further, at the time of a test, the conveyor arm  83  faces and pushes the wafer W against the probe card  50  facing into the prober  80  via the opening  82 . In that state, the tester inputs test signals to the IC device on the wafer W via the test head  10  for receiving the output to test the IC device. 
     Below, referring to  FIG. 6  to  FIG. 7E , a method of mounting a contactor on a mount base in the present embodiment will be explained.  FIG. 6  is a flow chart showing a method of mounting a contactor in an embodiment of the present invention, while  FIG. 7A  to  FIG. 7E  is a view for explaining the steps in  FIG. 6 . 
     First, in step S 10  of  FIG. 6 , a three-dimensional measurement system is used to measure the position of the reference point  51   c  provided in advance on the mount base  51 . This reference position  51   c  is set as the origin (0,0) in the three-dimensional measurement system. As the three-dimensional measurement system used in step S 10  and step S 11  of  FIG. 6 , for example, a CNC video measuring device, confocal laser microscope, or other non-contact type can be mentioned. 
     Next, the three-dimensional measurement system is used to measure the positions of the two first marks  51   d  actually provided on the mount base  51  in step S 11  of  FIG. 6  as shown in  FIG. 7A . In step S 12  of  FIG. 6 , the relative position m 1  (actual relative position (x 1 ,y 1 )) of the midpoint M 1  of the first marks  51   d  with respect to the reference point  51   c  is calculated. Note that, the first marks  51   d  actually provided on the mount base  51  are, for example, composed of through holes formed in the mount base  51 . 
     Next, the positions of the design first marks  51   e  in the mount base  51  are read from the CAD data, and the relative position m 0  of the midpoint M 0  of the first marks  51   e  with respect to the reference point  51   c  (theoretical relative position (x 0 ,y 0 )) is calculated in step S 13  of  FIG. 6 . 
     Next, in step S 14  of  FIG. 6 , the relative amount of deviation Δm of the design first marks  51   e  with respect to the first marks  51   d  actually provided on the mount base  51  is calculated from the actual relative position m 1  calculated in step S 12  and the theoretical relative position m 0  calculated in step S 13 . Specifically, this amount of deviation Δm is calculated by (Δx,Δy)=(x 1 −x 0 ,y 1 −y 0 ). 
     In step S 20  of  FIG. 6 , the amount of deviation Δm calculated using the three-dimensional measurement system in the above way is input to the mounting system for mounting the contactor  50  on the mount base  51 . Next, the mounting system uses image processing technology etc. to measure the positions of the two first marks  51   d  actually formed on the mount base  51  in step S 21  of  FIG. 6 , and the position (X m ,Y m ) of the midpoint M 1  of these two first marks  51   d  is calculated in step S 22  as shown in  FIG. 7B . 
     Next, in step S 23  of  FIG. 6 , as shown in  FIG. 7B , the position  51   f  at which the silicon finger contactor  60  should be mounted on the mount base  51  (mounting position) is specified on the basis of the midpoint M 1  calculated in step S 22  and the amount of deviation Δm input in step S 20 . Specifically, the mounting position is calculated by (X a ,Y a )=(X m −Δx,Y m −Δy). That is, in the present embodiment, the position  51   f  at which the contactor  60  should be mounted on the mount base  51  matches the midpoint M 0  of the design first marks  51   e  in the mount base  51 , and it is possible to cancel out the processing error caused when forming the first marks  51   d  on the mount base  51 . 
     Next, as shown in  FIG. 7C , the coating unit  101  of the mounting system coats an adhesive  51   b  on the mounting position  51   f  of the mount base  51  in step S 24  of  FIG. 6 . This coating unit  101 , while not particularly shown, for example, has a syringe in which an ultraviolet light curing adhesive is filled and can apply a predetermined amount of adhesive on the mount base 
     Next, the mounting system uses a pickup unit  102  to hold a silicon finger contactor  60  by suction and, in that state, uses image processing technology etc. to measure the positions of the two second marks  61   b  actually provided at the both ends of the base part  61  of the contactor  60  in step S 25  of  FIG. 6 , and the position of the midpoint M 2  of these two second marks  61   b  is calculated in step S 26  as shown in  FIG. 7B . 
     Next, in step S 27  of  FIG. 6 , the mounting system moves the silicon finger contactor  60  by the pickup unit  102  as shown in  FIG. 7D  and places the silicon finger contactor  60  on the mount base  51  in the state where the midpoint M 2  of the second marks  61   b  is separated from the mounting position  51   f  by exactly a predetermined distance L as shown in  FIG. 7B . Note that, as shown in  FIG. 7D , the front end of the pickup unit  102  is provided with a pickup surface  102   a  having substantially the same angle as the mounting angle β of the contactor  60  with respect to the mount base  51   
     Next the illuminating unit  103  of the mounting system illuminates the adhesive  51   b  with ultraviolet light to cure the adhesive  51   b  and fix the contactor  60  to the mount base  51  in step S 28  of  FIG. 6  as shown in  FIG. 7E . 
     As explained above, in the present embodiment, the reference point  51   c  is provided on the mount base  51  on which the contactor  60  mounted, the relative position of the actual first marks  51   d  (actual relative position m 1 ) and the relative position of the design first marks  51   d  (theoretical relative position m 0 ) with respect to the reference point  51   c  are calculated, the relative amount of deviation Δm of the actual relative position m 1  with respect to the theoretical relative position m 0  is calculated, and the amount of deviation Δm is considered when specifying the mounting position of the contactor  60  on the mount base  51 . For this reason, the processing error caused when forming the first marks  51   d  on the mount base  51  can be cancelled out, so it is possible to precisely mount the silicon finger contactor  60  on the mount base  51 . 
     Note that, the above explained embodiment was described for facilitating understanding of the present invention and was not described for limiting the present invention. Therefore, the elements disclosed in the above embodiment include all design changes and equivalents falling under the technical scope of the present invention. 
     For example, in the above embodiment, the explanation was given with reference to use of a silicon finger contactor  60  as a contactor mounted on the board, but the present invention is not particularly limited so long as the contactor requires positioning when being mounted on a board. 
     Further, in the above embodiment, the explanation was given with reference to use of a mount base  51  as the board on which the contactors are mounted, but the present invention is not particularly limited to this. For example, when directly mounting contactors on a circuit board, it is possible to provide the reference point and first marks on the circuit board.