Multi-Energy SEM Beam Switching for Accurate EPE Measurement
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Solution Overview
Problem
Existing SEM techniques for measuring edge placement error (EPE) and overlay shift in integrated circuits suffer from measurement inaccuracies due to varying responses of IC layers to high landing energy and noise in low landing energy images, leading to lower accuracy and throughput.
Innovation Solution
An inspection system utilizing multiple landing energy beams, with a beam controller to selectively deliver and switch between different energy levels, minimizing manual adjustments and reducing measurement drift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high landing energy SEM is used to take see-through images of different layers, then measurement of EPE or overlay shift is enabled, but measurement accuracy deteriorates due to varying responses of IC layers to high energy beams
Solution Approach 1:
The system dynamically switches between high landing energy and low landing energy beams based on the inspection requirements. The beam energy is made variable and adaptable rather than fixed, allowing the system to optimize for different measurement scenarios and maintain accuracy across varying IC layer responses.
Solution Approach 2:
The patent changes the physical parameter of beam landing energy to resolve the contradiction. By using high landing energy for see-through imaging to enable measurement and low landing energy for high-precision imaging to ensure accuracy, the system adjusts this critical parameter based on the specific measurement task at hand.
2Measurement precision
If low landing energy SEM images are taken from different layers and aligned together, then EPE or overlay shift measurement is enabled, but measurement accuracy deteriorates due to noise in low energy images
Solution Approach 1:
The system dynamically selects between low and high landing energy modes based on the specific measurement requirements. Rather than always using low energy for layer-by-layer imaging, the system adapts its energy level to minimize noise while achieving the necessary measurement precision.
Solution Approach 2:
The patent adjusts the beam energy parameter to overcome the noise problem inherent in low landing energy imaging. By switching to high landing energy when see-through imaging is required, the system eliminates noise issues while maintaining the ability to perform accurate measurements through proper image alignment and processing.
3Adaptability or versatility
If manual setting adjustments are performed between high and low energy measurements, then flexibility in measurement is maintained, but productivity deteriorates due to time-consuming adjustments
Solution Approach 1:
The patent combines multiple energy sources (high landing energy and low landing energy beams) into a single integrated system. This merging eliminates the need for separate manual setup procedures and allows automatic switching between energy modes, maintaining measurement flexibility while dramatically improving productivity.
Solution Approach 2:
The system performs automatic beam switching and energy adjustment without requiring manual intervention. The inspection system self-manages the transition between high and low landing energy modes based on the measurement task, eliminating time-consuming manual setting adjustments while maintaining full measurement flexibility.
4Adaptability or versatility
If measurements are taken at different times with different beam energies, then comprehensive inspection is achieved, but measurement accuracy deteriorates due to measurement drift
Solution Approach 1:
The system performs preliminary setup by configuring both high and low landing energy beams in advance within the same inspection session. This preliminary preparation ensures that both energy modes are ready for immediate use without requiring separate measurement sessions, thereby eliminating drift between measurements while maintaining comprehensive inspection capabilities.
Solution Approach 2:
The patent maintains continuous measurement action by switching between high and low landing energy beams within the same inspection session without interrupting the measurement process. This continuity eliminates time gaps between measurements that would cause drift, while still allowing comprehensive inspection using both energy modes for different measurement objectives.
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
Improves measurement accuracy and throughput by automatically switching between high and low landing energy beams, reducing errors and eliminating the need for manual setting adjustments.
Implementation Method 1
SEM delivers low energy electrons to a surface and records secondary or backscattered electrons leaving the surface using a detector
Implementation Method 2
SEM delivers low energy electrons to a surface and records secondary or backscattered electrons leaving the surface using a detector
Implementation Method 3
SEM delivers low energy electrons to a surface and records secondary or backscattered electrons leaving the surface using a detector
Data Source
AI summary
Inspection systems and methods are disclosed. An inspection system may include a first energy source configured to provide a first landing energy beam and a second energy source configured to provide a second landing energy beam. The inspection system may also include a beam controller configured to selectively deliver one of the first and second landing energy beams towards a same field of view, and to switch between delivery of the first and second landing energy beams according to a mode of operation of the inspection system.