Pulsed current source with internal impedance matching
AssigneeQualiTau, Inc.
InventorJens ULLMANN
Life of this patent
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Abstract
Pulsed current circuitry for electromigration testing of semiconductor integrated circuits and components. The circuit includes a multiplexer that outputs analog voltage pulses, and is capable of generating both bipolar and unipolar voltage pulses. At least one operational amplifier and resistor receive the voltage pulses from the multiplexer and convert the voltage pulses to current pulses. A charge booster circuit is provided for minimizing overshoots and undershoots during transitions between current levels in the test circuit.
Claims20
A test circuit for applying current pulses to a device under test (DUT), the test circuit comprising:
- a multiplexer that outputs analog voltage pulses, the multiplexer being capable of generating both bipolar and unipolar voltage pulses;
- and
- at least one operational amplifier and resistor that receive the voltage pulses from the multiplexer and convert the voltage pulses to current pulses, wherein an operational amplifier outputs current pulses, wherein the current pulses are bipolar or unipolar current pulses depending on whether the at least one operational amplifier and resistor receive bipolar or unipolar voltage pulses.
A method of providing a pulsed current to a device under test (DUT), the method comprising:
- providing a plurality of different voltage levels to a plurality of input terminals of a multiplexer;
- generating voltage pulses from a selected voltage level by using input select combination of input select lines of the multiplexer to determine which of the input terminals of the multiplexer is connected to an output of the multiplexer, wherein input select combination of the multiplexer is performed by assigning address values to input select lines of the multiplexer in a way such that any transitional address value leads to a monotonic change of the output of the multiplexer, wherein the output of the multiplexer comprises voltage pulses;
- and
- converting the voltage pulses to current pulses using a plurality of resistors, operational amplifiers, and capacitors.
A single circuit capable of providing both unipolar and bipolar current pulses, the circuit comprising:
- a muiltiplexer that receives at least one positive voltage signal and at least one negative voltage signal, wherein the multiplexer is capable of generating both bipolar and unipolar voltage pulses from the voltage signals it receives;
- and
- at least one operational amplifier and resistor that receive the voltage pulses from the multiplexer and convert the voltage pulses to current pulses, wherein an operational amplifier outputs bipolar or unipolar current pulses depending on whether the at least one operational amplifier and resistor receive bipolar or unipolar voltage pulses.
A method of using a charge booster circuit for minimizing overshoots and undershoots during transitions between current levels in a test circuit for applying current pulses to a device under test (DUT), the method comprising:
- providing the test circuit including a charge booster circuit, the charge booster circuit comprising at least one operational amplifier, a resistor network, and a capacitor;
- inputting current pulses to the charge booster circuit;
- controlling a charge flowing through the capacitor using the resistor network to match a charge needed to bring voltage across a parasitic capacitor of the test circuit to provide an output of the charge booster circuit;
- and
- delivering the output of the charge booster circuit to the DUT.
Dependencies are inferred from the claim text.