Magnetic force microscopy method and apparatus to detect and image currents in integrated circuits
First Claim
1. A method to non-invasively and nondestructively detect internal current in integrated circuits having internal conductive paths and a top surface, said method comprising the steps of:
- (a) positioning an integrated circuit onto a stage of an apparatus having a magnetic tip attached to a cantilever, said cantilever having a base and a resonant frequency;
(b) applying an electrical signal to said integrated circuit to produce magnetic fields from the conductive paths;
(c) approaching said integrated circuit with said magnetic tip of said apparatus to within a distance from said top surface of said integrated circuit small enough for a magnetic interaction to occur between said magnetic tip and the magnetic fields from said internal conductive paths and large enough that said magnetic tip does not physically interact with said top surface of said integrated circuit;
(d) vibrating said cantilever at its resonant frequency;
(e) scanning said integrated circuit and said magnetic tip relative to each other;
(f) detecting changes in the resonance properties of said cantilever caused by interactions in the magnetic forces between said conductive paths and said magnetic tip and determining current paths, magnitudes, and direction in said conductive paths from said changes in the resonance properties of said cantilever; and
(g) generating a map of said current in said integrated circuit.
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Accused Products
Abstract
A magnetic force microscopy method and improved magnetic tip for detecting and quantifying internal magnetic fields resulting from current of integrated circuits. Detection of the current is used for failure analysis, design verification, and model validation. The interaction of the current on the integrated chip with a magnetic field can be detected using a cantilevered magnetic tip. Enhanced sensitivity for both ac and dc current and voltage detection is achieved with voltage by an ac coupling or a heterodyne technique. The techniques can be used to extract information from analog circuits.
50 Citations
29 Claims
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1. A method to non-invasively and nondestructively detect internal current in integrated circuits having internal conductive paths and a top surface, said method comprising the steps of:
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(a) positioning an integrated circuit onto a stage of an apparatus having a magnetic tip attached to a cantilever, said cantilever having a base and a resonant frequency; (b) applying an electrical signal to said integrated circuit to produce magnetic fields from the conductive paths; (c) approaching said integrated circuit with said magnetic tip of said apparatus to within a distance from said top surface of said integrated circuit small enough for a magnetic interaction to occur between said magnetic tip and the magnetic fields from said internal conductive paths and large enough that said magnetic tip does not physically interact with said top surface of said integrated circuit; (d) vibrating said cantilever at its resonant frequency; (e) scanning said integrated circuit and said magnetic tip relative to each other; (f) detecting changes in the resonance properties of said cantilever caused by interactions in the magnetic forces between said conductive paths and said magnetic tip and determining current paths, magnitudes, and direction in said conductive paths from said changes in the resonance properties of said cantilever; and (g) generating a map of said current in said integrated circuit. - View Dependent Claims (2, 3, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 24, 27)
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4. A method to non-invasively and nondestructively detect internal currents in integrated circuits having internal conductive paths and a top surface, said method comprising the steps of:
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(a) positioning an integrated circuit onto a stage of a scanning probe microscope having a magnetic tip attached to a cantilever having a resonant frequency; (b) applying an electrical signal to said integrated circuit to induce magnetic fields from said currents in the conductive paths, the electrical signal having an ac component at about the resonant frequency of the cantilever and a dc component; (c) approaching said integrated circuit with a magnetic tip of said scanning probe microscope to within a distance from said top surface of said integrated circuit, wherein said distance is small enough for a magnetic interaction to occur between said magnetic tip and said magnetic fields from said currents in said conductive paths and large enough that said magnetic tip will not physically interact with said top surface of said integrated circuit; (d) vibrating said cantilever, wherein said cantilever vibrates at about its resonant frequency; (e) scanning said integrated circuit and said magnetic tip relative to each other; (f) detecting changes in the resonance properties of said cantilever caused by interactions in the magnetic forces between said currents in said conductive paths and said magnetic tip and determining current paths, magnitudes, and direction from said changes in the resonance properties of said cantilever; and (g) generating a map of said current in said integrated circuit. - View Dependent Claims (22, 23, 25, 26, 28, 29)
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Specification