Needle load measuring method, needle load setting method and needle load detecting mechanism

Abstract

With a probe-test method and a prober for examining certain electric characteristics of an object of examination, a main chuck is adapted to be driven to move in the X-, Y-, Z- and 0-directions in order to bring the object into contact with the probes of the prober and then the shaft of the support of the main chuck is warped under the contact pressure applied by the probes to tilt the main chuck. The position where each of the probes contacts the corresponding one of the electrodes on the object is displaced (moved) in the X-, Y- and Z-directions by the tilt. The displacement is predicted by an operation unit and the main chuck is moved in the X-, Y- and Z-directions to correct the displacement.

What is claimed is:  
     
         1 . A method of measuring a needle load applied by a plurality of probes to a wafer chuck in inspecting the electrical characteristics of a to-be-inspected object by using a probe apparatus, comprising the steps of: 
 overdriving a wafer chuck having a to-be-inspected object placed thereon by using a wafer chuck lift mechanism so as to bring said to-be-inspected object(s) into contact with a plurality of probes of said probe apparatus; and    measuring the sinking amount of said wafer chuck caused by the needle load applied by said plural probes to the wafer chuck via the to-be-inspected object when the to-be-inspected object is brought into contact with the plural probes;    wherein the needle load corresponding to the measured sinking amount is obtained on the basis of the data showing the relationship between the needle load applied to the wafer chuck and the sinking amount of the wafer chuck caused by said needle load.    
     
     
         2 . The method of measuring the needle load according to    claim 1   , wherein the step of measuring the sinking amount of said wafer chuck is performed at a plurality of points of said wafer chuck.  
     
     
         3 . The method of measuring the needle load according to    claim 1   , wherein the wafer chuck having said to-be-inspected object placed thereon is overdriven by a lift mechanism comprising a ball screw, a driving mechanism for rotating said ball screw, and a nut member.  
     
     
         4 . The method of measuring the needle load according to    claim 2   , wherein the step of measuring the sinking amount comprises the sub-steps of: 
 detecting a pseudo overdriving amount of the wafer chuck performed by said lift mechanism, said pseudo overdriving amount being the overdriving amount of the wafer chuck performed by said lift mechanism when said needle load is not applied to the wafer chuck;    detecting the actual overdriving amount of the wafer chuck performed by said lift mechanism, said actual overdriving amount being the actual overdriving amount of the wafer chuck performed by said lift mechanism when the needle load is applied to the wafer chuck; and    obtaining the sinking amount of the wafer chuck from the difference between the pseudo overdriving amount and the actual overdriving amount.    
     
     
         5 . The method of measuring the needle load according to    claim 4   , wherein the step of detecting the pseudo overdriving amount comprises the process of detecting said pseudo overdriving amount on the basis of the amount of rotation of the driving mechanism for rotating said ball screw measured by a rotary encoder.  
     
     
         6 . The method of measuring the needle load according to    claim 4   , wherein the step of detecting the actual overdriving amount comprises the process of detecting the actual overdriving amount of said wafer chuck by a linear encoder.  
     
     
         7 . The method of measuring the needle load according to    claim 5   , wherein the step of detecting the actual overdriving amount comprises the process of detecting the actual overdriving amount of said wafer chuck by a linear encoder.  
     
     
         8 . A method of setting a needle load applied by a plurality of probes to a to-be-inspected object at a predetermined value in inspecting the electrical characteristics of said to-be-inspected object by overdriving a wafer chuck having said to-be-inspected object placed thereon in a probe apparatus so as to bring said to-be-inspected object into an electrical contact with said plural probes, comprising the step of: 
 detecting the sinking amount of said wafer chuck caused by the needle load applied by said plural probes in the process of overdriving said wafer chuck;    wherein the needle load applied to the to-be-inspected object placed on said wafer chuck is set at a predetermined value by setting the sinking amount detected in said step at a sinking amount corresponding to a predetermined needle load on the basis of the data showing the relationship between the needle load applied to the wafer chuck and the sinking amount of the wafer chuck caused by the needle load.    
     
     
         9 . The method of measuring the needle load according to    claim 8   , wherein the step of measuring the sinking amount of said wafer chuck is performed at a plurality of points of said wafer chuck.  
     
     
         10 . The method of measuring the needle load according to    claim 8   , wherein the wafer chuck having said to-be-inspected object placed thereon is overdriven by a lift mechanism comprising a ball screw, a driving mechanism for rotating said ball screw, and a nut member.  
     
     
         11 . The method of measuring the needle load according to    claim 7   , wherein the step of measuring the sinking amount comprises the sub-steps of: 
 detecting a pseudo overdriving amount of the wafer chuck performed by said lift mechanism, said pseudo overdriving amount being the overdriving amount of the wafer chuck performed by said lift mechanism when said needle load is not applied to the wafer chuck;    detecting the actual overdriving amount of the wafer chuck performed by said lift mechanism, said actual overdriving amount being the actual overdriving amount of the wafer chuck performed by said lift mechanism when the needle load is applied to the wafer chuck; and    obtaining the sinking amount of the wafer chuck from the difference between the pseudo overdriving amount and the actual overdriving amount.    
     
     
         12 . The method of measuring the needle load according to    claim 10   , wherein the step of detecting the pseudo overdriving amount comprises the process of detecting the pseudo overdriving amount on the basis of the rotation amount of the driving mechanism for rotating the ball screw, which is measured by a rotary encoder.  
     
     
         13 . The method of measuring the needle load according to    claim 10   , wherein the step of detecting the actual overdriving amount comprises the process of detecting the actual overdriving amount of said wafer chuck by a linear encoder.  
     
     
         14 . The method of measuring the needle load according to    claim 11   , wherein the step of detecting the actual overdriving amount comprises the process of detecting the actual overdriving amount of said wafer chuck by a linear encoder.  
     
     
         15 . A probe apparatus for inspecting the electrical characteristics of a to-be-inspected object, comprising: 
 a wafer chuck for placing a to-be-inspected object thereon;    a lift mechanism for vertically moving said wafer chuck;    a plurality of probes brought into an electrical contact with a plurality of electrodes of the to-be-inspected object placed on said wafer chuck overdriven by said lift mechanism;    a measuring mechanism for measuring the sinking amount of said wafer chuck caused by the needle load applied by said plural probes to the to-be-inspected object(s) when the wafer chuck is overdriven to bring the to-be-inspected object placed on the wafer chuck into contact with said plural probes; and    a needle load detecting mechanism for obtaining the needle load corresponding to the measured sinking amount on the basis of the data showing the relationship between the needle load applied to the wafer chuck and the sinking amount of the wafer chuck.    
     
     
         16 . The probe apparatus according to    claim 15   , wherein the sinking amount of the wafer chuck is measured at a plurality of points of the wafer chuck.  
     
     
         17 . The probe apparatus according to    claim 15   , wherein said lift mechanism comprises a ball screw, a driving mechanism for rotating said ball screw and a nut member.  
     
     
         18 . The probe apparatus according to    claim 15   , wherein the measuring mechanism of the sinking amount comprises: 
 a first lift amount detecting mechanism for detecting a pseudo lift amount of the wafer chuck performed by said lift mechanism, said first lift amount detecting mechanism detecting a pseudo overdriving amount that said lift mechanism may overdrive said wafer chuck when said needle load is not applied to the wafer chuck;    a second lift amount detecting mechanism for detecting the actual overdriving amount of the wafer chuck performed by said lift mechanism, said second lift amount detecting mechanism detecting the actual overdriving amount of the wafer chuck performed by said lift mechanism when the needle load is applied to the wafer chuck;    a calculating mechanism for obtaining the sinking amount of the wafer chuck from the difference between the pseudo overdriving amount detected by said first lift amount detecting mechanism and the actual overdriving amount detected by said second lift amount detecting mechanism;    a storing device for storing the data showing the relationship between the needle load applied to said wafer chuck and the sinking amount of the wafer chuck caused by said needle load; and    a needle load detecting mechanism for obtaining the needle load corresponding to the sinking amount of the wafer chuck obtained by said calculating mechanism on the basis of the data showing the relationship between the needle load applied to said wafer chuck and the sinking amount of the wafer chuck caused by said needle load.    
     
     
         19 . The probe apparatus according to    claim 16   , wherein the measuring mechanism of the sinking amount comprises: 
 a first lift amount detecting mechanism for detecting a pseudo lift amount of the wafer chuck performed by said lift mechanism, said first lift amount detecting mechanism detecting a pseudo overdriving amount that said lift mechanism may overdrive said wafer chuck when said needle load is not applied to the wafer chuck;    a second lift amount detecting mechanism for detecting the actual overdriving amount of the wafer chuck performed by said lift mechanism, said second lift amount detecting mechanism detecting the actual overdriving amount of the wafer chuck performed by said lift mechanism when the needle load is applied to the wafer chuck;    a calculating mechanism for obtaining the sinking amount of the wafer chuck from the difference between the pseudo overdriving amount detected by said first lift amount detecting mechanism and the actual overdriving amount detected by said second lift amount detecting mechanism;    a storing device for storing the data showing the relationship between the needle load applied to said wafer chuck and the sinking amount of the wafer chuck caused by said needle load; and    a needle load detecting mechanism for obtaining the needle load corresponding to the sinking amount of the wafer chuck obtained by said calculating mechanism on the basis of the data showing the relationship between the needle load applied to said wafer chuck and the sinking amount of the wafer chuck caused by said needle load.