Dual Electron Beam Pre-Dose for High Aspect Ratio Contact Holes
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Solution Overview
Problem
In scanning electron microscopes, the observation and measurement of contact holes with large aspect ratios are hindered by the loss of secondary electrons to the sidewalls, making it difficult to achieve stable charge distribution and high-resolution imaging due to the large irradiation regions and varying electron density during pre-dose processes.
Innovation Solution
The method involves using a first electron beam with a larger diameter for pre-dose to reduce the non-irradiated region and stabilize charge quickly, followed by a second electron beam with a narrower diameter for observation, and adjusting secondary electron generation efficiencies to maintain uniform charge conditions, allowing for oblique beam irradiation and reducing aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a large irradiation region is used for pre-dose to stabilize charge distribution, then charge uniformity is improved, but pre-dose time is significantly extended
Solution Approach 1:
The pre-dose process is divided into multiple scanning passes with different beam parameters. The first pass uses a larger beam diameter to cover a wider area and establish initial charge distribution, while subsequent passes use smaller beam diameters to refine and stabilize the charge in specific regions, thereby reducing the total time required compared to using a single large irradiation region throughout
Solution Approach 2:
The electron beam diameter is dynamically adjusted during the pre-dose process. The system transitions from a larger beam diameter for initial charging to a smaller beam diameter for fine-tuning and stabilization. This dynamic adjustment allows the system to achieve both wide coverage and precise charge control without extending the total pre-dose time
2Measurement precision
If a narrow electron beam is used for observation, then imaging resolution is improved, but charge stabilization becomes difficult in large irradiation regions
Solution Approach 1:
The system performs preliminary charging using a larger electron beam diameter before switching to the narrow beam for observation. This preliminary action establishes a stable charge distribution across the entire irradiation region, ensuring that when the narrow beam is used for high-resolution imaging, the charge remains stable and does not fluctuate
Solution Approach 2:
The system changes the beam diameter parameter between pre-dose and observation phases. During pre-dose, a larger beam diameter is used to ensure adequate charge distribution. During observation, the beam diameter is reduced for high-resolution imaging while the previously established charge distribution remains stable, thus resolving the contradiction between resolution and charge stability
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 rapid stabilization of charge, high-accuracy measurements, and high-resolution imaging of contact holes with large aspect ratios without extending the pre-dose time, while preventing electrostatic damage and maintaining uniform charge distribution.
Implementation Method 1
detect a secondary electron excited by a primary electron beam
Implementation Method 2
performing preliminary irradiation of a primary electron beam prior to electron beam scanning for inspection and measurement
Implementation Method 3
the region for inspection and measurement is made charge positively thereby taking out of the electron from the contact hole is facilitated
Data Source
AI summary
As an aspect for realizing accurate observation, inspection, or measurement of the contact hole with large aspect ratio, a method and a device to scan a second electron beam after scanning a first electron beam to a sample to charge the sample are proposed wherein the beam diameter of the first electron beam is made larger than the beam diameter of the second electron beam.