Cathodoluminescence IC Testing via Electron Beam
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Solution Overview
Problem
Current optical beam probing techniques are diffraction-limited and unable to resolve structures smaller than 700 nm, making them ineffective for modern ICs with features sizes of 10 nm or smaller, and fail to provide high-speed testing with single active component resolution.
Innovation Solution
The method involves applying an electric test pattern to an integrated circuit, delivering a stream of primary electrons to its back side, detecting cathodoluminescence light initiated by secondary electrons, and analyzing this light for correlation with the test pattern to measure local electric fields, allowing for high-resolution analysis of active structures without the need for imaging optics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical beam probing is used for IC testing, then the testing method is well-established and can detect functional analysis of active devices, but the resolution is diffraction-limited and cannot resolve structures smaller than 700 nm
Solution Approach 1:
The patent replaces the optical probing system with an electron beam-based cathodoluminescence system. Electrons are accelerated to high energies and focused to a fine spot on the IC surface, generating cathodoluminescence light that is collected and analyzed. This substitution of optical mechanics with electron beam mechanics enables resolution beyond the diffraction limit, achieving sub-700 nm resolution while maintaining the ability to detect active device functionality through cathodoluminescence intensity measurements
Solution Approach 2:
The patent changes the fundamental parameter of the probing beam from optical wavelength (limited by diffraction) to electron beam energy and focus. By controlling electron beam parameters such as acceleration voltage and focal spot size, the system achieves resolution independent of wavelength-based diffraction limits. The cathodoluminescence emission characteristics are also utilized as a new measurement parameter to extract functional information about active devices
2Measurement precision
If shorter wavelength laser is used to improve resolution, then resolution may improve, but electron-hole pair generation increases which negatively affects measurement results
Solution Approach 1:
The patent replaces optical radiation with electron beam radiation to eliminate the harmful effect of excessive electron-hole pair generation. The electron beam interacts with the semiconductor material to generate cathodoluminescence through a different physical mechanism that is less prone to generating spurious charge carriers that would interfere with measurements. This substitution resolves the contradiction between achieving high resolution and avoiding harmful side effects
3Measurement precision
If high numerical aperture optical system is used to improve resolution, then resolution improves, but the wavelength of probing laser remains in the range of 1064 nm or 1340 nm where Si has sufficient low absorption
Solution Approach 1:
The patent substitutes the optical laser probing system with an electron beam system, eliminating the constraint of laser wavelength selection based on silicon absorption characteristics. The electron beam can be focused to a fine spot regardless of material absorption properties at specific wavelengths, as electron interaction with matter is governed by different physical principles. This allows high-resolution probing without being limited by optical absorption constraints
4Device complexity
If optical beam probing is used for modern ICs, then the testing apparatus is simpler, but it fails to provide single active component resolution for features sizes of 10 nm or smaller
Solution Approach 1:
The patent replaces the simple optical probing apparatus with an electron beam-based cathodoluminescence system that provides the necessary resolution for modern sub-10 nm IC features. The electron beam can be focused to nanometer-scale spots, enabling single active component resolution. The system maintains relative simplicity by using standard electron beam technology and cathodoluminescence detection, avoiding the need for complex super-resolution optical techniques
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 enables resolution below the diffraction limit, allowing for analysis of structures as small as 0.4 nm to 5 nm, and high-speed testing up to 10 GHz, with minimal material damage and substantial cathodoluminescence light intensity, effectively improving IC testing capabilities.
Implementation Method 1
delivering a stream of primary electrons to a back side of the IC in an active region... detecting a light resulting from cathodoluminescence (CL) initiated by secondary electrons in the IC
Implementation Method 2
Cathodoluminescence is an optical and electrical phenomenon. Electrons impacting on a material cause the emission of photons, i.e. the cathodoluminescence light
Implementation Method 3
The electron beam has a resolution about the size of the active structure under investigation, e.g. of a transistor or a diode, and less than the spacing between active structures of the IC
Data Source
AI summary
A method for analyzing an integrated circuit includes: applying an electric test pattern to the IC; delivering a stream of primary electrons to a back side of the IC on an active region to a transistor of interest, the active region including active structures such as transistors of the IC; detecting light resulting from cathodoluminescence initiated by secondary electrons in the IC; and analyzing the detected light regarding a correlation with the electric test pattern applied to the IC. A system for analyzing an IC is provided.