Method and Apparatus for Semi-Automatic Extraction and Monitoring of Diode Ideality in a Manufacturing Environment

Abstract

A method, an apparatus, and a computer program are provided for the semi-automatic extraction of an ideality factor of a diode. Traditionally, current/voltage curves for diodes, which provided a basis for extrapolating the ideality factors, had to be determined by hand. By employing a thermal voltage proportional to absolute temperature (PTAT) generator in conjunction with an extraction mechanism, the ideality factor can be extracted in an semi-automatic manner. Therefore, a reliable, quick, and less expensive device can be employed to improve measurements of ideality factors.

1 . An apparatus for determining a diode ideality factor of at least one diode in a manufacturing environment, comprising: 
 a PTAT circuit for generating a thermal voltage output proportional to temperature (PTAT);    an extraction control unit that generates an extraction control output;    a multiplexer (mux) for receiving the thermal voltage output and a signal corresponding to said extraction control output;    a comparator for receiving an output from the mux and an ideal PTAT value, wherein the comparator generates a comparator output; and    a lead zero determining circuit coupled to the comparator which identifies a selected voltage based on the comparator output, wherein the selected voltage corresponds to a diod ideality factor of the at least one diode.    
   
   
       2 - 21 . (canceled)  
   
   
       22 . A method for identifying a diode ideality factor for at least one diode, comprising: 
 generating a plurality of voltages using the at least one diode based on a supply voltage;    selecting a representative voltage from the plurality of voltages based on a determination of a voltage in the plurality of voltages that approximates an ideal voltage; and    calculating an ideality factor based on the selected representative voltage and the supply voltage.    
   
   
       23 . The method of  claim 22 , wherein the ideality factor is calculated as a function relating the supply voltage to the selected representative voltage.  
   
   
       24 . The method of  claim 22 , further comprising: 
 comparing each voltage in the plurality of voltages to the ideal voltage;    determining if each voltage is greater than or less than the ideal voltage;    determining a voltage at which there is a transition in the plurality of voltages where a voltage is greater than the ideal voltage to a voltage that is less than the ideal voltage; and    selecting the representative voltage based on the determined transition.    
   
   
       25 . The method of  claim 24 , wherein the plurality of voltages are generated by a thermal voltage output proportional to temperature (PTAT) device, and wherein the ideal voltage is selected based on a number of voltage divisions in the PTAT device and a current density ratio.  
   
   
       26 . The method of  claim 25 , wherein the PTAT device generates the plurality of voltages based on a voltage difference between at least two forward biased diodes with different current densities.  
   
   
       27 . The method of  claim 22 , wherein calculating the ideality factor comprises dividing the supply voltage by the selected representative voltage.  
   
   
       28 . The method of  claim 22 , wherein the method is applied to a plurality of diodes at a plurality of different locations on a integrated circuit device wafer.  
   
   
       29 . The method of  claim 28 , further comprising: 
 receiving an input specifying a particular location on the integrated circuit device wafer that is selected for which the method is to be applied.    
   
   
       30 . An apparatus for identifying a diode ideality factor for at least one diode, comprising: 
 a voltage generation circuit comprising at least one diode, wherein the voltage generation circuit generates a plurality of voltages using the at least one diode based on a supply voltage; and    a representative voltage selection circuit that selects a representative voltage from the plurality of voltages based on a determination of a voltage in the plurality of voltages that approximates an ideal voltage, wherein an ideality factor is calculated based on the selected representative voltage and the supply voltage.    
   
   
       31 . The apparatus of  claim 22 , wherein the ideality factor is calculated as a ratio of the supply voltage to the selected representative voltage.  
   
   
       32 . The apparatus of  claim 30 , further comprising: 
 a comparator coupled to the voltage generation circuit, the comparator comparing each voltage in the plurality of voltages to the ideal voltage to thereby identify whether each voltage is greater than or less than the ideal voltage;    a determination circuit coupled to the comparator, wherein the determination circuit determines a representative voltage at which there is a transition in the plurality of voltages where a voltage is greater than the ideal voltage to a voltage that is less than the ideal voltage; and    a register coupled to the determination circuit that stores a selection value indicative of the representative voltage based on the determined transition.    
   
   
       33 . The apparatus of  claim 32 , wherein the voltage generation circuit is a thermal voltage output proportional to temperature (PTAT) circuit, and wherein the ideal voltage is selected based on a number of voltage divisions in the PTAT circuit and a current density ratio.  
   
   
       34 . The apparatus of  claim 33 , wherein the PTAT circuit generates the plurality of voltages based on a voltage difference between at least two forward biased diodes with different current densities.  
   
   
       35 . The apparatus of  claim 30 , wherein the apparatus operates on a plurality of diodes at a plurality of different locations on a integrated circuit device wafer.  
   
   
       36 . The apparatus of  claim 35 , further comprising: 
 a location selection circuit that receives an input specifying a particular location on the integrated circuit device wafer that is selected on which the apparatus is to operate.    
   
   
       37 . A computer program product in a computer readable medium, the computer program product comprising a computer readable program which, when executed by a computing device, causes the computing device to: 
 generate a plurality of voltages using the at least one diode based on a supply voltage;    select a representative voltage from the plurality of voltages based on a determination of a voltage in the plurality of voltages that approximates an ideal voltage; and    calculate an ideality factor based on the selected representative voltage and the supply voltage.    
   
   
       38 . The computer program product of  claim 37 , wherein the ideality factor is calculated as a ratio of the supply voltage to the selected representative voltage.  
   
   
       39 . The computer program product of  claim 37 , wherein the computer readable program further causes the computing device to: 
 compare each voltage in the plurality of voltages to the ideal voltage;    determine if each voltage is greater than or less than the ideal voltage;    determine a voltage at which there is a transition in the plurality of voltages where a voltage is greater than the ideal voltage to a voltage that is less than the ideal voltage; and    select the representative voltage based on the determined transition.    
   
   
       40 . The computer program product of  claim 37 , wherein the computer readable program is executed by the computing device on a plurality of diodes at a plurality of different locations on a integrated circuit device wafer.