Intermediate Lens Electron Detection for SEM Signal Throughput
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Solution Overview
Problem
Reliably inspecting and imaging samples with charged particle beam apparatuses, such as scanning electron microscopes, at high resolution and throughput is challenging, particularly in the semiconductor industry, where increasing the signal-to-noise ratio and detection efficiency of signal electrons is beneficial.
Innovation Solution
The implementation of an intermediate lens between an on-axis detector and an objective lens in a charged particle beam apparatus, which collimates high energy signal electrons, including backscattered electrons, onto the opening of the on-axis detector, and utilizes different modes of operation for energy filtering to enhance detection efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the primary charged particle beam is guided through an on-axis detector and focused onto a specimen, then high spatial resolution imaging is achieved, but the detection efficiency of signal electrons is reduced
Solution Approach 1:
An intermediate lens is introduced between the objective lens and the on-axis detector to act as an intermediary optical element. This intermediate lens creates a crossover point that redirects high energy signal electrons toward the detector while maintaining the primary beam path through the on-axis opening, thereby improving detection efficiency without compromising spatial resolution.
2Reliability
If the signal-to-noise ratio is increased by improving detection efficiency, then reliable inspection and imaging are achieved, but the throughput of the apparatus is reduced
Solution Approach 1:
The intermediate lens is designed with adjustable excitation levels that allow dynamic switching between different operational modes. In a first mode, the lens is excited to collimate high energy electrons for improved detection; in a second mode, the excitation is adjusted to optimize for higher throughput. This dynamic adaptability enables the system to balance between signal-to-noise ratio and throughput based on inspection requirements.
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 configuration significantly increases the detection efficiency of high energy signal electrons, improves the signal-to-noise ratio, and enhances the throughput of the charged particle beam apparatus, particularly for medium and high landing energies.
Implementation Method 1
providing an excitation of the intermediate lens to collimate high energy signal electrons including backscattered electrons to the opening of the on-axis detector
Implementation Method 2
focusing the primary charged particle beam with the objective lens onto the specimen
Data Source
AI summary
A method of operating a charged particle beam apparatus is described. The method includes guiding a primary charged particle beam through an opening of an on-axis detector, through an intermediate lens, through an objective lens, and onto a specimen, wherein the intermediate lens is disposed between the on-axis detector and the objective lens; focusing the primary charged particle beam with the objective lens onto the specimen; in a first mode of operation, providing an excitation of the intermediate lens to collimate high energy signal electrons including backscattered electrons to the opening of the on-axis detector; in the first mode of operation, detecting low energy signal electrons including secondary electrons with the on-axis detector; and in the first mode of operation, detecting the backscattered electrons with a second electron detector upstream of the on-axis detector. Also a corresponding charged particle beam apparatus is described.