Lrl vector calibration to the end of the probe needles for non-standard probe cards for ate rf testers

Abstract

A method and apparatus for radio frequency vector calibration of s-parameter measurements to the tips of the wafer probe needles of an automatic test equipment production tester. The method involves a modified Line-Reflect-Line (LRL) calibration routine that uses a Thru-Reflect-Line to LRL shift to eliminate the need for a precisely characterized reflect standard used during a conventional LRL calibration. The method further involves de-embedding the non-ideal effects of the non-zero length thru standard used during the calibration routine to improve measurement accuracy of the tester. The apparatus may involve the use of RF relays to allow multiple wafer probe needles to share RF test ports.

1 .- 7 . (canceled) 
   
   
       8 . An apparatus for testing an integrated circuit comprising:
 an automatic test equipment production tester including a test head having at least two radio frequency measurement ports and a plurality of wafer probes, each wafer probe having a plurality of wafer probe needles;   at least one radio frequency relay comprising:   an input port;   at least two output ports; and   a plurality of relay states;   wherein the input port of the at least one radio frequency relay is operably connected to one of the at least two measurement ports and each of the at least two output ports of the relay is operably connected to one of the plurality of wafer probe needles.   
   
   
       9 . The apparatus of  claim 8  further comprising a memory in communication with the automatic test equipment production tester to store a set of calibration correction factors for each relay state. 
   
   
       10 . The apparatus of  claim 9  wherein a set of calibration correction factors for each relay state is obtained by performing a modified Line-Reflect-Line calibration method, wherein a reference plane is shifted to tips of the wafer probe needles based only on knowledge of geometric lengths of two line calibration standards. 
   
   
       11 . The apparatus of  claim 10  wherein each set of calibration correction factors is stored in the memory. 
   
   
       12 .- 14 . (canceled) 
   
   
       15 . The apparatus of  claim 8 , wherein the plurality of wafer probes and the at least one radio frequency relay are implemented on a load board coupled to the at least two radio frequency measurement ports. 
   
   
       16 . The apparatus of  claim 8 , wherein each of the radio frequency measurement ports is configured to be shared by a plurality of output pins of a device under test (DUT), each output pin being coupled to a corresponding one of the plurality of states of the radio frequency relay via a respective wafer probe needle. 
   
   
       17 . The apparatus of  claim 10 , wherein the line calibration standards are configured to be accommodated without having to adjust spacing between the wafer probes during calibration. 
   
   
       18 . The apparatus of  claim 10 , wherein the line calibration standards are implemented on a wafer using microstrip lines. 
   
   
       19 . A method for testing an integrated circuit comprising:
 providing a relay coupled to a radio frequency measurement port in an automatic test equipment production tester, the relay having a plurality of states, each relay state configured to operably connect the radio frequency measurement port with a corresponding wafer probe needle included in a wafer probe;   obtaining a set of calibration correction factors corresponding to each relay state; and   storing the respective set of calibration correction factors to each relay state.   
   
   
       20 . The method of  claim 19 , wherein the operation of obtaining comprises:
 performing a modified Line-Reflect-Line (LRL) calibration method, wherein a reference plane is shifted to the tips of the wafer probe needles based only on knowledge of geometric lengths of a non-zero-length through calibration standard and a second line calibration standard.   
   
   
       21 . The method of  claim 20 , wherein performing the modified LRL calibration method further comprises:
 de-embedding effects of the non-zero-length through calibration standard, resulting in shifting the reference plane to the tips of the wafer probe needles.   
   
   
       22 . The method of  claim 19 , wherein the method further comprises:
 sharing the radio frequency measurement port by a plurality of output pins of a device under test (DUT), wherein each output pin is coupled to a corresponding one of the plurality of states of the radio frequency relay via a respective wafer probe needle.