Apparatus and method for analyzing functional failures in integrated circuits
First Claim
1. An apparatus for analyzing an integrated circuit (IC) to identify at least one circuit element responsible for producing a functional failure in the IC, comprising:
- (a) means for operating the IC under conditions wherein the functional failure occurs, with the functional failure producing over time a fraction of defective output states and a remainder of good output states at an output from the IC in response to a set of input test vectors repeatedly provided to the IC;
(b) a laser producing a beam having a photon energy less than a bandgap energy of a substrate whereon the IC is formed;
(c) means for focusing and scanning the laser beam across the IC, thereby producing localized heating within the IC that generates a change in the fraction of defective output states from the IC, the focusing and scanning means further providing a position signal to indicate the location of the laser beam on the IC at any instant in time; and
(d) means, receiving inputs of the position signal and the change in the fraction of defective output states from the IC, for mapping the location of each circuit element within the IC responsible for the change in the fraction of defective output states from the IC.
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Abstract
An apparatus and method are presented for identifying and mapping functional failures in an integrated circuit (IC) due to timing errors therein based on the generation of functional failures in the IC. This is done by providing a set of input test vectors to the IC and adjusting one or more: of the IC voltage, temperature or clock frequency; the rate at which the test vectors are provided to the IC; or the power level of a focused laser beam used to probe the IC and produce localized heating which changes the incidence of the functional failures in the IC which can be sensed for locating the IC circuit elements responsible for the functional failures. The present invention has applications for optimizing the design and fabrication of ICs, for failure analysis, and for qualification or validation testing of ICs.
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Citations
55 Claims
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1. An apparatus for analyzing an integrated circuit (IC) to identify at least one circuit element responsible for producing a functional failure in the IC, comprising:
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(a) means for operating the IC under conditions wherein the functional failure occurs, with the functional failure producing over time a fraction of defective output states and a remainder of good output states at an output from the IC in response to a set of input test vectors repeatedly provided to the IC;
(b) a laser producing a beam having a photon energy less than a bandgap energy of a substrate whereon the IC is formed;
(c) means for focusing and scanning the laser beam across the IC, thereby producing localized heating within the IC that generates a change in the fraction of defective output states from the IC, the focusing and scanning means further providing a position signal to indicate the location of the laser beam on the IC at any instant in time; and
(d) means, receiving inputs of the position signal and the change in the fraction of defective output states from the IC, for mapping the location of each circuit element within the IC responsible for the change in the fraction of defective output states from the IC. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. An apparatus for analyzing an integrated circuit (IC) to locate any signal propagation paths that produce timing errors within the IC that result in an incorrect value of an output voltage from the IC, comprising:
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(a) means for operating the IC under conditions which produce an incidence of the timing errors in the IC in response to a set of input test vectors provided to the IC;
(b) a laser having a laser beam with a photon energy less than a bandgap energy of a semiconductor substrate whereon the IC is formed;
(c) a scanning optical microscope for receiving the laser beam and producing therefrom a focused laser beam which is scanned across a portion of the IC, with the scanning optical microscope further generating a position signal indicative of the position of the focused laser beam at any instant in time, and with the focused laser beam producing localized heating within the IC that changes the incidence of the timing errors in the IC;
(d) means connected to the IC for measuring the output voltage from the IC and generating therefrom an analytical output signal whenever the output voltage switches between the incorrect value and a correct value; and
(e) a display for receiving the position signal and the analytical output signal and generating therefrom a map for locating each signal propagation path within the IC responsible for producing the timing errors. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43)
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44. A method for analyzing an integrated circuit (IC) and identifying any circuit elements in the IC responsible for producing functional failures in the IC, comprising steps for:
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(a) controlling operational parameters of the IC to induce a level of incidence of the functional failures therein, with the functional failures producing an incorrect value of an output voltage from the IC in response to a set of input test vectors provided to the IC;
(b) scanning the IC with a focused laser beam having a photon energy less than a bandgap energy of a substrate whereon the IC is formed to locally heat circuit elements within the IC, thereby changing the level of incidence of the functional failures in the IC; and
(c) measuring the change in the level of incidence of the functional failures in the IC as a function of the position of the focused laser beam incident on the IC, thereby locating the circuit elements in the IC responsible for producing the functional failures in the IC. - View Dependent Claims (45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55)
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Specification