Electron-beam probing of photodiodes
AssigneeSanta Barbara Research Center
InventorsIchiro Kasai, Roderic L. Osgood, Charley B. Burgett, Richard J. Joyce, Michael D. Warfield
Life of this patent
Estimating the term…
Abstract
Method and apparatus for testing photodiode arrays using an electron beam. The diodes are charged at successive intervals over the RC time constant curve to develop successively increasing voltages at the ends of succeeding time intervals. Diode voltage and current are measured at the end of each interval and the resulting data are used to develop a current-voltage characteristic for each diode.
Claims20
Photodiode testing apparatus comprising:
- electron beam control means for charging the parallel resistance and capacitance of a photodiode during a selected time interval;
- secondary emission electron means for measuring the voltage of the photodiode at predetermined times within said interval;
- means for measuring photodiode current at said times;
- means for correlating the corresponding measurements of photodiode voltage and current to derive a plurality of data points relating thereto;
- and
- means for determining a current-voltage curve for the photodiode from the derived data points.
Apparatus for testing a plurality of photodiodes in a photodiode array comprising:
- means for repetitively scanning a selected plurality of photodiodes in said array by irradiating each of the selected diodes in succession with an electron beam for a selected time interval, wherein each repeated scan of a given photodiode develops a photodiode voltage proportional to the diode irradiation duty cycle;
- means for measuring secondary electrons emitted from each of the scanned photodiodes in succession to provide a measurement of diode voltage;
- means for measuring individual photodiode current in each of the selected photodiodes concurrently with the measurement of diode voltage;
- and
- means for correlating corresponding voltage and current measurements to derive a plurality of data points corresponding to individual voltage and current measurements in order to develop a current voltage characteristic for each of the diodes being measured.
The method of testing an array of elements to determine the current-voltage characteristic of each element, wherein each element has an inherent effective resistance and capacitance, the method comprising:
- directing an E-beam to scan each element in turn;
- limiting the time duration of irradiation of each element during a given scan to an interval which is only a minor portion of the charging time constant of the element;
- measuring individual element voltage by detecting secondary emission electrons from each irradiated element at the end of said interval;
- measuring current through each element at the end of each interval;
- respectively scanning each of the elements within a time period succeeding the initial scan which is less than the discharge time constant of the elements;
- repeating the steps of measuring voltage and current for each successive scan;
- and
- correlating the successive measurements of voltage and current for each individual element to develop a current-voltage characteristic for each element over a range of varying voltages and currents.
Dependencies are inferred from the claim text.