Dual-phase interferometry for charge modulation mapping in ICS
Inventors
Yurt, Abdulkadir • Unlu, Selim M. • Goldberg, Bennett B. • Ramsay, Euan
Assignees
Boston University • United States Department of the Air Force
Publication Number
US-9983260-B2
Publication Date
2018-05-29
Expiration Date
2033-10-11
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Abstract
A dual-phase interferometric method and device for charge modulation mapping in integrated circuits provides significant improvement in signal to noise ratio over conventional detection configurations. The method and device can be used for failure analysis and testing of advanced technology IC chips for which high sensitivity in modulation mapping is required.
Core Innovation
The invention provides a dual-phase interferometric method and device for charge modulation mapping in integrated circuits (ICs) that significantly improves signal to noise ratio compared to conventional detection configurations. It enables in-situ monitoring and mapping of electrical activity within IC devices, which is critical for test and fault analysis. The method addresses technical complications arising from advanced manufacturing technologies such as increased substrate doping levels, decreased feature sizes, and lower supply voltages by achieving higher detection sensitivity and signal localization.
The problem being solved is that traditional backside laser-beam techniques for probing transient charge density changes in integrated circuits suffer from extremely low reflectance modulation amplitude, on the order of parts per million of the reflected beam. This low signal magnitude makes sensitive and quantitative measurement difficult. Additionally, challenges such as limited front-side access due to metallization and packaging layers, along with evolving IC manufacturing constraints, demand more sensitive and spatially resolved detection mechanisms.
Claims Coverage
The patent includes multiple independent claims describing both a method and apparatus for detecting electrical activity using a dual-phase interferometric approach, with distinctive inventive features focusing on interferometric processing and enhanced detection sensitivity.
Dual-phase interferometric detection method
A method comprising applying a laser beam to an electrically energized IC substrate, receiving reflected radiation, optically processing the reflected beam to generate two beams with different phase angles, sensing their intensities, and electronically processing these intensities to indicate substrate electrical activity.
Dual-phase interferometric detection apparatus
An apparatus including a polarized radiation source, optics for applying radiation to and receiving reflected radiation from a substrate, an optical system generating two phase-separated beams from the reflected radiation, sensing means for these beams, and processing means to distinguish electrical activity signals from background effects.
Reference beam splitting and optical processing
Optical system feature including splitting a reference beam from the generated radiation, passing it through a quarter wave plate and polarizer, reflecting it back, and combining it with the reflected beam from the substrate to produce beams with phase differences (e.g., π/2) and distinct polarization for sensitive detection.
Use of lock-in amplifiers and balanced detectors
Processing means that include lock-in amplifiers and/or balanced detectors to provide time-resolved and DC components from the sensed radiation, enabling isolation and enhancement of weak modulation signals representative of electrical activity.
Use of scanning optics for two-dimensional mapping
Incorporation of scanning means to apply the laser beam over a two-dimensional area of the substrate, enabling spatial imaging of electrical activity and modulation within the IC.
The claims collectively cover a dual-phase interferometric approach involving generating and combining reference and reflected beams with controlled phase differences, sensing and processing resultant signals to provide improved detection and mapping of electrical activity within IC substrates, with configurations enabling spatial and time-resolved imaging.
Stated Advantages
Significantly improved signal to noise ratio compared to conventional charge modulation detection techniques.
Higher detection sensitivity and enhanced localization capability accommodating advanced IC manufacturing challenges such as increased doping levels and reduced feature sizes.
Ability to perform time-resolved and spatially resolved imaging of electrical activity within integrated circuits.
Differential detection and interferometric mixing reduce common-mode noise and enhance the measurement of weak reflectance modulation signals.
Documented Applications
Failure analysis and testing of advanced technology integrated circuit chips requiring high sensitivity in charge modulation mapping.
Quantitative analysis of delay and jitter effects in parts of electrical circuits through monitoring relative phase of interferometric responses.
Mapping time-dependent electrical signal modulation in devices and metallic interconnects of integrated circuits.
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