Work Function Measurement Using Sequential Electron Excitation
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Solution Overview
Problem
Current electron spectroscopy techniques face challenges in achieving high spatial resolution and accuracy for characterizing small features in integrated circuits, particularly in determining work function and detecting electric charge leakages, while minimizing electrical charging artifacts.
Innovation Solution
A novel electron spectroscopy technique that utilizes multiple excitation sources, including high-energy radiation, low-energy electron beams, and electrical biasing, to perform sequential measurement modes, canceling electrical charging artifacts by averaging results from opposite charging directions, and using modulated excitations for high-accuracy measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional electron spectroscopy techniques (XPS, AES) are used to characterize sample surfaces, then chemical composition and elemental identification can be obtained, but spatial resolution is limited and surface charging artifacts distort the spectra
Solution Approach 1:
The patent applies preliminary anti-action by introducing a charge compensation mechanism before the harmful charging effect can fully distort the measurement. A low-energy electron flood gun is used to pre-neutralize positive charging on the sample surface, and a positive ion source compensates for negative charging, thereby preventing spectrum distortion before it occurs during the electron spectroscopy measurement
Solution Approach 2:
The patent uses intermediary charged particle sources (electron flood gun and positive ion source) as mediators between the sample surface and the electron spectrometer. These intermediaries control the electrical charge state of the sample surface, acting as a buffer that prevents direct interaction between the primary electron beam and the charging artifacts that would otherwise distort the measurement
2Measurement precision
If high-energy electron beams are used to improve spatial resolution, then smaller regions can be characterized, but surface damage increases due to high energy bombarding
Solution Approach 1:
The patent applies parameter changes by switching between different electron beam energy levels. A low-energy electron flood gun (minimal damage) is used for charge compensation, while a high-energy focused electron beam is used only when spatial resolution is required. This dynamic adjustment of beam energy parameters allows optimization between spatial resolution and surface damage based on measurement needs
3Measurement precision
If charge compensation is applied to eliminate charging artifacts, then measurement accuracy improves, but additional complexity is introduced to the measurement system
Solution Approach 1:
The patent applies universality by designing a measurement system where the charge compensation sources (electron flood gun and ion source) serve multiple functions. These components not only compensate for charging artifacts but also enable work function measurements through controlled charging, and can be used to study electrical properties of the sample. This multi-functionality justifies the added system complexity by providing multiple measurement capabilities
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
Enables fast and precise characterization of chemical and electrical properties of small structures, detecting failures at a single element level, and identifying electric charge leakages, with improved spatial resolution and reduced measurement artifacts.
Implementation Method 1
exciting said at least region of the sample by the high energy electromagnetic radiation to induce a first-mode secondary electron emission spectral response
Implementation Method 2
exciting the sample by the e-radiation of relatively low energy electron flux followed by a gradual variation of the bias voltage
Data Source
AI summary
A measurement system includes: an excitation system; a detector; and a control unit. The excitation system includes excitation sources generating excitations of different types comprising: a high energy electromagnetic radiation source; at least one electric power supply providing a bias voltage to a sample; and at least one electron beam source generating relatively low energy e-radiation in the form of an electron beam. The excitation system includes first and second sequentially performed measurement modes, for respectively, exciting the sample by the high energy radiation to induce a first-mode secondary electron emission spectral response, and supplying initial bias voltage to the sample and exciting the sample with the e-radiation followed by a gradual variation of the bias voltage from said initial bias voltage to induce a second-mode electric current variations in the sample. The detector detects said first-mode secondary electron emission spectral response and generates first-mode measured data, and monitors the electric current through the sample and generates second-mode measured data indicative of sample current readout.