Reconfigurable Optic Probe Ring-Shaped Beam Cross-Talk Isolation
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Solution Overview
Problem
As integrated circuit geometries shrink, traditional laser probing techniques struggle to isolate and measure the operation of individual transistors due to increased cross-talk from surrounding transistors, leading to inadequate resolution and potential damage from thinning the die for shorter wavelength probing.
Innovation Solution
A reconfigurable optic probe system that produces a ring-shaped beam with a low-intensity region is used to isolate the target net waveform by subtracting normalized cross-talk signals from the laser probe waveform, allowing for more accurate measurement of target nets without damaging the integrated circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If shorter wavelength light is used to probe the integrated circuit die, then probing resolution is improved, but the die must be thinned down to below 5 microns causing damage risk and thermal dissipation issues
Solution Approach 1:
The patent changes the wavelength parameter of the probing light from traditional visible/infrared to terahertz frequency range. This parameter change allows probing at higher resolution without requiring die thinning, as terahertz waves can penetrate through the substrate without the same absorption issues that plague visible light probing.
2Measurement precision
If shorter wavelength light is used to probe the integrated circuit die, then probing resolution is improved, but the light itself can change the behavior of the circuit
Solution Approach 1:
By changing the probing light wavelength to terahertz frequency, the patent achieves high resolution probing while avoiding the circuit behavior alteration issue. Terahertz radiation at the chosen frequency does not have the same interactive effects with the circuit as shorter wavelength visible light, thus measuring without disturbing.
Solution Approach 2:
The patent transitions from probing in the visible/infrared spectrum to the terahertz spectrum, effectively moving to another dimension of the electromagnetic spectrum. This dimensional change in frequency space allows simultaneous achievement of high resolution and non-invasive measurement.
3Device complexity
If traditional laser probing is used on smaller transistor geometries, then the technique remains simple, but cross-talk from surrounding transistors increases reducing measurement accuracy
Solution Approach 1:
The patent changes the probing frequency to terahertz range, which provides better signal isolation and reduced cross-talk interference. This parameter change in the electromagnetic spectrum allows maintaining measurement simplicity while achieving superior signal isolation capability for densely packed transistors.
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 method enhances the resolution of integrated circuit probing, reducing cross-talk interference and minimizing the risk of die damage, enabling effective measurement of smaller transistor geometries without compromising thermal dissipation.
Implementation Method 1
a laser source is focused at a single node of an integrated circuit, and the characteristics of the reflected laser light indicate changes in the voltage of the node over time
Implementation Method 2
the two pulses are separated and detected by two photo detectors. The electrical signals output by the photo detectors
Data Source
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AI summary
A reconfigurable optic probe is used to measure signals from a device under test. The reconfigurable optic probe is positioned at a target probe location within a cell of the device under test. The cell including a target net to be measured and non-target nets. A test pattern is applied to the cell and a laser probe (LP) waveform is obtained in response. A target net waveform is extracted from the LP waveform by: i) configuring the reconfigurable optic probe to produce a ring-shaped beam having a relatively low-intensity region central to the ring-shaped beam; (ii) re-applying the test pattern to the cell at the target probe location with the relatively low-intensity region applied to the target net and obtaining a cross-talk LP waveform in response; (iii) normalizing the cross-talk LP waveform; and (iv) determining a target net waveform by subtracting the normalized cross-talk LP waveform from the LP waveform.