MOFSET mismatch characterization circuit
View Patent ↗A semiconductor device comprising a first inverter circuit including a first PMOS transistor and a first NMOS transistor, a drain electrode of the first PMOS transistor coupled to a drain electrode of the first NMOS transistor, and a second inverter circuit including a second PMOS transistor and a second NMOS transistor, a drain electrode of the second PMOS transistor coupled to a drain electrode of the second NMOS transistor. A first output voltage pad coupled to gate electrodes of the first and second PMOS and NMOS transistors, and between the drain electrode of the first PMOS transistor and the drain electrode of the NMOS transistor to self-bias the first inverter circuit. A second output voltage pad coupled between the drain electrode of the second PMOS transistor and the drain electrode of the second NMOS transistor.
1. A semiconductor device comprising:
a first P-type metal oxide semiconductor (PMOS) transistor having a source electrode, a drain electrode, and a gate electrode;
a second PMOS transistor having a source electrode, a drain electrode, and a gate electrode;
a first N-type metal oxide semiconductor (NMOS) transistor having a source electrode, a drain electrode, and a gate electrode; and
a second NMOS transistor having a source electrode, a drain electrode, and a gate electrode, wherein
the drain electrodes of the first PMOS and NMOS transistors are coupled together to a first output terminal, wherein a signal at the first output terminal depends only on an output of the first PMOS and NMOS transistors,
the first output terminal is connected as an only input to the gate electrodes of the first and second PMOS transistors and the first and second NMOS transistors,
the drain electrode of the second PMOS transistor is coupled to the drain electrode of the second NMOS transistor at a second output terminal,
an absolute value circuit including
a first comparator configured to generate a switch signal, and
a second comparator configured to receive the first output at a first input and the second output at a second input when the switch signal is a first value, and to receive the second output at the first input and the first output at the second input when the switch signal is a second value; and
a summing amplifier having an input coupled to the output of the second comparator, wherein the summing amplifier output a signal that indicates mismatch between the transistors.
2. The semiconductor device of claim 1 further comprising:
the first output terminal coupled between the drain and gate electrodes of the first PMOS transistor and the first NMOS transistor,
the second output terminal coupled between the drain electrodes of the second PMOS transistor and the second NMOS transistor.
3. The semiconductor device of claim 1 further comprising:
a first voltage supply coupled to the source electrodes of the first and second PMOS transistors.
4. The semiconductor device of claim 1 further comprising:
a second voltage supply coupled to the source electrodes of the first and second NMOS transistors.
5. The semiconductor device of claim 1 further comprising:
the first PMOS and NMOS transistors form a self-biased inverter circuit.
6. The semiconductor device of claim 5 wherein:
the second PMOS and NMOS transistors are included in a second circuit stage to amplify transistor mismatch of the self-biased inverter circuit.
7. The semiconductor device of claim 1 further comprising:
the difference between the voltages at the first and second output terminals is based on mismatch between at least one of: the first and second PMOS transistors, and the first and second NMOS transistors.
8. The semiconductor device of claim 1 further comprising:
the first and second PMOS transistors and the first and second NMOS transistors form a first mismatch circuit;
a second mismatch circuit including:
a first output terminal,
first and second PMOS transistors,
first and second NMOS transistors, and
a second output terminal;
a first absolute value circuit configured to output the difference between the voltage at the first and second output terminals of the first mismatch circuit;
a second absolute value circuit configured to output a difference between voltage at the first and second output terminals of the second mismatch circuit;
a summing amplifier circuit including an input coupled to the outputs of the first and second absolute value circuits, the summing amplifier is configured to generate a standard deviation of the mismatch between the transistors in the first and second mismatch circuits.
9. The semiconductor device of claim 1 further comprising:
a summing amplifier including a first input coupled to an output of the second comparator, a second input coupled to ground, and a resistor coupled between an output of the summing amplifier and the first input of the summing amplifier, wherein the output of the summing amplifier indicates mismatch between the transistors.
10. The semiconductor device of claim 1 wherein:
geometry of the transistors is minimum length NMOS transistors with width scaled four to nine times minimum length, and
minimum length for the PMOS transistors with width for the PMOS transistors scaled to give current drive comparable to the NMOS transistors.
11. A method comprising:
configuring a test circuit that measures mismatch between transistors in a semiconductor device by taking the difference between voltage at a first output terminal and voltage at a second output terminal, the configuring including:
forming the first output terminal as an only input to gate electrodes of first and second PMOS transistors and first and second NMOS transistors;
forming drain electrodes of the first PMOS transistor and first NMOS transistor coupled to the first output terminal, wherein a signal at the first output terminal depends only on an output of the first PMOS and NMOS transistors;
forming drain electrodes of the second PMOS transistor and second NMOS transistor coupled to the second output terminal;
coupling the first and second output terminals to an absolute value circuit, the absolute value circuit including
a first comparator for generating a switch signal, and
a second comparator for receiving the first output at a first input and the second output at a second input when the switch signal is a first value, and for receiving the second output at the first input and the first output at the second input when the switch signal is a second value; and
coupling an input of a summing amplifier to the output of the second comparator.
12. The method of claim 11 further comprising:
amplifying the transistor mismatch with the second PMOS and NMOS transistors.
13. The method of claim 11 , wherein the first PMOS and NMOS transistors form a first inverter circuit, the method further comprising:
coupling output from the first inverter circuit to an input of the first inverter circuit to self-bias the first inverter circuit.
14. The method of claim 11 further comprising:
forming the second output terminal coupled between the drain electrode of the second PMOS transistor and the drain electrode of the second NMOS transistor.
15. The method of claim 11 further comprising:
coupling a first voltage supply to the source electrode of the first PMOS transistor and source electrode of the second PMOS transistor.
16. The method of claim 11 further comprising:
coupling a second voltage supply to the source electrodes of the first NMOS transistor and the second NMOS transistor.
17. A semiconductor device comprising:
a plurality of mismatch circuits, each of the mismatch circuits including:
a first inverter circuit including a first PMOS transistor and a first NMOS transistor, a drain electrode of the first PMOS transistor coupled to a drain electrode of the first NMOS transistor;
a second inverter circuit including a second PMOS transistor and a second NMOS transistor, a drain electrode of the second PMOS transistor coupled to a drain electrode of the second NMOS transistor;
a first output voltage pad is coupled to provide an only input to gate electrodes of the first and second PMOS and NMOS transistors
the first voltage output pad is coupled between the drain electrode of the first PMOS transistor and the drain electrode of the first NMOS transistor, wherein a signal at the first output terminal depends only on an output of the first PMOS and NMOS transistors;
a second output voltage pad coupled between the drain electrode of the second PMOS transistor and the drain electrode of the second NMOS transistor;
a plurality of absolute value circuits, each absolute value circuit corresponding to one of the plurality of mismatch circuits and having a first input connected to the first output voltage output pad, and a second input and a third input connected to the second output voltage output pad, wherein
a difference between voltage at the first input and the second input of the absolute value circuit is used to set a switch signal,
a complement of the first switch signal is coupled to operate a first switch connected between the first input of the absolute value circuit and a first input of a comparator,
the switch signal is used to operate a second switch connected between the second input of the absolute value circuit and the first input of the comparator,
the complement of the switch signal is used to operate a third switch connected between the second input of the absolute value circuit and a second input of the comparator,
first switch signal is used to operate a fourth switch connected between the first input of the absolute value circuit and the second input of the comparator, and
an output of the first comparator is coupled as an input to a summing amplifier and an output of the summing amplifier indicates mismatch between the transistors.
18. The semiconductor device of claim 17 further comprising:
source electrodes of the first and second PMOS transistors are coupled to Vdd, and
source electrodes of the first and second NMOS transistors are coupled to Vss.
19. The semiconductor device of claim 17 wherein:
geometry of the transistors is at least one of the group consisting of:
minimum length and width for the transistors;
greater than minimum length and width for the transistors;
minimum length and width for the NMOS transistors, minimum length for the PMOS transistors and width for the PMOS transistors scaled to give current drive comparable to the NMOS transistors; and
minimum length NMOS transistors with width scaled four and nine times minimum length, minimum length for the PMOS transistors and width for the PMOS transistors scaled to give current drive comparable to the NMOS transistors.
20. The semiconductor device of claim 17 wherein:
a difference between the voltages at the first and second output pads is based on mismatch between at least one of: the first and second PMOS transistors, and the first and second NMOS transistors.
21. The semiconductor device of claim 17 wherein
a difference between voltage at the first output voltage pad and the second output voltage pad indicates transistor mismatch between the transistors on the semiconductor device.
22. The semiconductor device of claim 17 further comprising:
a wafer including a plurality of semiconductor die structures and horizontal and vertical scribe streets between the die structures, wherein the first and second inverter circuits are located in one of the scribe streets.
23. The semiconductor device of claim 17 further comprising:
a wafer including a plurality of semiconductor die structures, wherein the first and second inverter circuits are located in at least one of the die structures.