Process parameter extraction
First Claim
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1. An apparatus comprising:
- a first circuit fabricated on a semiconductor substrate to generate a first oscillating signal that propagates through the first circuit, the first oscillating signal having a frequency dependent on at least in part a parameter of a process used to fabricate the first circuit;
a second circuit fabricated on the semiconductor substrate near the first circuit to generate a second oscillating signal that propagates through the second circuit, a phase relationship existing between the first and second oscillating signals at adjacent points of the first and second circuits; and
a third circuit coupled to the first and second circuits to regulate logical state transitions in the first and second oscillating signals to cause the phase relationship to be near a predetermined value.
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Abstract
An apparatus includes a test circuit, a first counter and a second counter. The test circuit is fabricated on a semiconductor substrate to generate an oscillating signal. The oscillating signal has a frequency that is dependent on at least in part a parameter of a process used to fabricate the test circuit. The first counter measures a time interval, and the second counter is coupled to the first counter to count a number of periods of the oscillating signal during the time interval.
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Citations
22 Claims
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1. An apparatus comprising:
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a first circuit fabricated on a semiconductor substrate to generate a first oscillating signal that propagates through the first circuit, the first oscillating signal having a frequency dependent on at least in part a parameter of a process used to fabricate the first circuit;
a second circuit fabricated on the semiconductor substrate near the first circuit to generate a second oscillating signal that propagates through the second circuit, a phase relationship existing between the first and second oscillating signals at adjacent points of the first and second circuits; and
a third circuit coupled to the first and second circuits to regulate logical state transitions in the first and second oscillating signals to cause the phase relationship to be near a predetermined value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
a first flip-flop to regulate the logical state transitions of the first oscillating signal; and
a second flip-flop to regulate the logical state transitions of the second oscillating signal.
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5. The apparatus of claim 1, wherein the circuit comprises:
logic to detect edge transitions in at least one of the first and second oscillating signals.
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6. The apparatus of claim 1, wherein the first circuit and the third circuit in combination form a ring oscillator.
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7. The apparatus of claim 1, wherein at least one of the first and second circuits comprises:
a chain of inverters.
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8. The apparatus of claim 1, wherein the first circuit comprises a first chain of at least one inverter, the second circuit comprises a second chain of at least one inverter, and the first chain has a different number of inverters than the second chain.
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9. A test apparatus comprising:
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a first oscillator fabricated in a semiconductor substrate to generate a first oscillating signal, a frequency of the first oscillating signal being substantially influenced by a first process parameter of the substrate and not being substantially influenced by a second process parameter of the substrate; and
a second oscillator fabricated in the semiconductor substrate to generate a second oscillating signal, a frequency of the second oscillating signal being substantially influenced by the second process parameter and not being substantially influenced by the first process parameter. - View Dependent Claims (10, 11, 12, 13, 14)
a third oscillator fabricated in the semiconductor substrate to generate a third oscillating signal, a frequency of the third oscillating signal not being substantially influenced by the first and second process parameters.
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12. The test apparatus of claim 9, wherein the first and second oscillators are located adjacent to each other.
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13. The test apparatus of claim 9, further comprising:
at least one counter to measure at least one of the first and second frequencies.
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14. The test apparatus of claim 9, wherein at least one of the first and second oscillators comprises a ring oscillator.
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15. A method comprising:
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fabricating a first circuit in a semiconductor substrate;
fabricating a second circuit in the semiconductor substrate;
using the first circuit to generate a first oscillating signal;
using the second circuit to generate a second oscillating signal; and
regulating the generation of the first oscillating signal and regulating the generation of the second oscillating signal to establish a phase relationship between the signals, wherein the first oscillating signal has a frequency that is a function of one or more process parameters that characterize a process used to fabricate the first circuit. - View Dependent Claims (16, 17)
synchronizing edges of the first and second oscillating signals.
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18. A method comprising:
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generating a first oscillating signal, a frequency of the first oscillating signal being substantially influenced by a first process parameter of a substrate and not being substantially influenced by a second process parameter of the substrate;
generating a second oscillating signal, a frequency of the second oscillating signal being substantially influenced by a second process parameter and not being substantially influenced by the first process parameter; and
using the first and second oscillating signals to extract at least one of the first and second process parameters. - View Dependent Claims (19, 20, 21, 22)
obtaining a measure of the first and second frequencies to extract at least one of the first and second process parameters.
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21. The method of claim 18, further comprising:
generating a third oscillating signal, a frequency of the third oscillating signal not being substantially influenced by the first process parameter of the substrate and not being substantially influenced by the second process parameter.
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22. The method of claim 21, further comprising:
using the first, second and third oscillating signals to extract at least one of the first and second process parameters.
Specification