Dual-Phase Interferometry for IC Charge Modulation Mapping
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Solution Overview
Problem
In-situ monitoring and mapping of electrical activity in integrated circuits (ICs) face challenges due to the low amplitude of reflectance modulation and large intensity differences between applied radiation and signal components, especially with advancing manufacturing technologies like increasing substrate doping levels and decreasing feature sizes, which require higher detection sensitivity and localization capability.
Innovation Solution
A dual-phase interferometric confocal imaging method and device that uses polarized infrared CW laser radiation, optics to adjust phase and polarization of reflected and reference beams, and lock-in amplifiers to detect electrical activity with enhanced resolution, isolating the signal from background effects and providing time-resolved and DC components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional reflectance-based probing techniques are used, then the measurement setup is simple, but the detection sensitivity is insufficient due to low amplitude of reflectance modulation (parts per million level)
Solution Approach 1:
The patent introduces an interferometric detection system that uses a reference beam as an intermediary to amplify the weak reflectance modulation signal. The reference beam interferes with the reflected beam from the IC, converting the tiny amplitude modulation (parts per million) into a measurable intensity variation through constructive and destructive interference patterns, thereby achieving high detection sensitivity without direct amplification of the weak signal
Solution Approach 2:
The patent replaces direct intensity measurement with optical phase measurement through interferometry. By converting the measurement from the time domain (intensity modulation) to the phase domain, the system achieves enhanced sensitivity to electrical activity changes while filtering out background noise and large intensity variations
2Measurement precision
If the intensity of applied laser radiation is increased to improve signal detection, then the signal-to-noise ratio improves, but the large intensity difference between applied radiation and signal component creates measurement challenges
Solution Approach 1:
The interferometric system uses a reference beam with controlled intensity as an intermediary to bridge the gap between the strong applied laser radiation and the weak reflected signal. The reference beam's intensity is adjusted to be comparable to the reflected beam, allowing both to interfere constructively and produce a measurable signal that preserves the original signal-to-noise ratio while eliminating the dynamic range problem
Solution Approach 2:
The patent transforms the measurement from a single-dimensional intensity comparison (where the signal is lost in the large intensity difference) to a two-dimensional interferometric measurement space. By measuring both amplitude and phase through interference patterns, the system can extract the weak signal information independently of the large background intensity
3Reliability
If substrate doping levels are increased to improve device performance, then device reliability improves, but the detection sensitivity requirement increases due to reduced electrical activity signals
Solution Approach 1:
The interferometric detection system acts as a highly sensitive intermediary that can detect the reduced electrical activity signals resulting from higher substrate doping levels. The phase-sensitive measurement capability of the interferometer allows it to detect subtle changes in refractive index caused by lower carrier concentrations, maintaining measurement precision even when device reliability is improved through higher doping
4Manufacturing precision
If feature size is decreased to improve integration density, then manufacturing precision improves, but localization capability requirement increases to resolve smaller electrical activity features
Solution Approach 1:
The patent uses confocal optics to segment the measurement volume into a tightly focused probe region, allowing independent measurement of electrical activity at different spatial locations. This segmentation capability enables the system to resolve and localize electrical activity in smaller features by confining the measurement to a diffraction-limited volume, thereby maintaining localization capability as feature sizes decrease
Solution Approach 2:
The patent employs wavelength optimization and numerical aperture adjustment to change the spatial resolution parameters of the optical system. By selecting appropriate laser wavelengths and optimizing the focusing optics, the system achieves sub-micron localization capability that matches the decreasing feature sizes in advanced IC technologies
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances detection sensitivity and localization capability, providing improved spatial resolution and signal-to-noise ratio for mapping electrical activity in ICs, effectively addressing the limitations of conventional reflectance-based probing techniques.
Implementation Method 1
The presence of free-carriers alters the local refractive index and thus influences the intensity of the focused laser beam reflected from the device
Implementation Method 2
dual-phase interferometric confocal imaging method and device that uses polarized infrared CW laser radiation, optics to adjust phase and polarization of reflected and reference beams
Data Source
AI summary
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.