Active cancellation matrix for process parameter measurements

Abstract

An active cancellation matrix for process parameter measurements provides feedback paths for each test location wherein each feedback path is used to sense the applied voltage and the sensed voltage is used to adjust the source voltage for any variations along the input path. The devices under test are arranged in a row and column array, and the feedback and voltage input paths are formed along respective rails which extend generally parallel to a row of devices under test. Selectors are used to selectively route the outputs of the test nodes to a measurement unit such as a current sensor. The input voltages can be varied to establish current-voltage (I-V) curves for the devices under various conditions. In the example where the devices under test are transistors, each source input includes three voltage inputs (rails) for a drain voltage, a source voltage, and a gate voltage.

1 .- 7 . (canceled) 
   
   
       8 . An active cancellation matrix for an array of devices under test, comprising:
 a plurality of source inputs for generating voltage signals;   a plurality of voltage rails wherein each of said voltage rails connects a respective one of said source inputs to a plurality of test nodes arranged in a row, with first wire sections formed by taps along the voltage rail to the test nodes, each first wire section having a respective transmission load; and   a plurality of feedback rails, wherein each of said feedback rails connects a feedback input of a respective one of the source inputs to the test nodes in the row, with second wire sections formed by taps along the feedback rail to the test nodes, each second wire section used to sense a voltage applied at the node and adjust the voltage signal for any variations in the first transmission load of a corresponding first wire section, and wherein the voltage and feedback rails are generally parallel to a direction of the row of test nodes.   
   
   
       9 . (canceled) 
   
   
       10 . The active cancellation matrix of  claim 8  wherein different rows of test nodes are arranged to form a row and column array of test nodes. 
   
   
       11 . The active cancellation matrix of  claim 8 , further comprising means for varying the amplitude of the voltage signals. 
   
   
       12 . The active cancellation matrix of  claim 8 , further comprising:
 a measurement unit; and   one or more selectors which route outputs of the test nodes to said measurement unit.   
   
   
       13 . The active cancellation matrix of  claim 8  wherein:
 the devices under test are transistors; and   each source input includes three voltage inputs for a drain voltage, a source voltage, and a gate voltage.   
   
   
       14 . A system for testing electronic devices arranged in a row and column array, comprising:
 a plurality of column inputs, each column input having a voltage source connected to a column voltage rail disposed along a first direction with taps along said column voltage rail to devices under test arranged in a common column;   a plurality of row inputs, each row input having a voltage source connected to a row voltage rail disposed along a second direction which is generally orthogonal to the first direction with taps along said row voltage rail to devices under test arranged in a common row;   a plurality of column feedback rails, each column feedback rail disposed along the first direction with taps along said column feedback rail to corresponding devices under test arranged in the common column, wherein said column feedback rail senses an applied voltage and adjusts a voltage source for any variations in a transmission load of a corresponding column voltage rail;   a plurality of row feedback rails, each row feedback rail disposed along the second direction with taps along said row feedback rail to corresponding devices under test arranged in the common row, wherein said row feedback rail senses an applied voltage and adjusts a voltage source for any variations in a transmission load of a corresponding row voltage rail;   at least one measurement device; and   one or more selectors which route outputs of the devices under test to said measurement device.   
   
   
       15 . The system of  claim 14 , further comprising means for varying the amplitude of the voltage sources. 
   
   
       16 . The system of  claim 14  wherein each of said voltage sources includes a respective operational amplifier having a feedback input which is connected to a corresponding one of the column or row feedback rails. 
   
   
       17 . The system of  claim 14  wherein said row and column feedback rails are selectively connected to one or more of the devices under test using switches which are controlled by select logic that also controls selection of said row and column inputs. 
   
   
       18 . The system of  claim 14  wherein said measurement device is a current sensor. 
   
   
       19 . The system of  claim 14  wherein
 the devices under test are transistors;   each column input provides a drain voltage for corresponding transistors arranged in a common column;   each row input provides a gate voltage for corresponding transistors arranged in a common row; and   said one or more selectors route source outputs of the transistors to said measurement device.