SEM Objective Lens and Compensation Electrode for Off-Axis Focus
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Solution Overview
Problem
Current scanning electron microscope devices face challenges with off-axis aberration, limited field of view, and reduced resolution due to high-energy electron beams, which can cause unrecoverable damage to wafers and are inefficient for defect detection in semiconductor manufacturing.
Innovation Solution
The proposed solution involves a scanning electron microscope device with a deflection mechanism comprising a first and second electrostatic deflector, a magnetic yoke with an excitation coil, and a compensation electrode that adjusts the electron beam's focus dynamically by changing voltage in real-time, along with an optional third deflector to minimize off-axis aberration and enhance the field of view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-energy electron beam is used to improve resolution, then detection precision is improved, but wafer damage increases and reliability deteriorates
Solution Approach 1:
The patent dynamically changes the energy parameter of the electron beam by adjusting acceleration voltage based on the position being inspected. Low energy (e.g., 1-5 kV) is used for most areas to prevent damage, while high energy (e.g., 10-30 kV) is selectively applied only to areas requiring high-resolution inspection, thus resolving the contradiction between detection precision and wafer integrity
Solution Approach 2:
The patent implements dynamic beam energy adjustment during the inspection process. The acceleration voltage is changed in real-time based on the inspection requirements of different regions, allowing the system to adapt between low-energy mode for general scanning and high-energy mode for detailed examination, thereby maintaining both wafer safety and detection precision
2Reliability
If deceleration mode is used to control landing energy, then wafer damage is reduced, but off-axis aberration increases and measurement precision deteriorates
Solution Approach 1:
The patent applies different beam control strategies to different spatial regions. On-axis regions use deceleration mode for safe landing energy control, while off-axis regions use immersion mode with magnetic lens focusing to maintain beam quality and resolution, thus resolving the contradiction between wafer protection and off-axis measurement precision
3Productivity
If field of view is increased to improve productivity, then detection speed is improved, but off-axis aberration increases and measurement precision deteriorates
Solution Approach 1:
The patent dynamically adjusts the incident angle of the electron beam during scanning. By changing the beam angle adaptively, the system can maintain optimal focus and minimize off-axis aberration even when inspecting large-area fields of view, thus resolving the contradiction between productivity and off-axis measurement precision
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 reduces off-axis beam spot size, improves image resolution, and increases the maximum available field of view, enhancing the operational efficiency and throughput of electron beam inspection systems.
Implementation Method 1
an electrostatic deflector configured to deflect the electron beam
Implementation Method 2
a magnetic lens configured to focus the electron beam
Implementation Method 3
project electron beam to a surface of the sample to generate backscattered electrons and secondary electrons
Data Source
AI summary
A scanning electron microscope device for a sample to be detected and an electron beam inspection apparatus are provided, the scanning electron microscope device being configured to project electron beam to a surface of the sample to generate backscattered electrons and secondary electrons, and comprising: an electron beam source, a deflection mechanism, and an objective lens assembly. The deflection mechanism comprises a first deflector located downstream the electron beam source and a second deflector located downstream the first deflector. The objective lens assembly comprises: an excitation coil; and a magnetic yoke, formed by a magnetizer material as a housing which opens towards the sample and comprising a hollow body defining an internal chamber where the excitation coil is accommodated, and at least one inclined portion extending inward from the hollow body at an angle with reference to the hollow body and directing towards the optical axis, with an end of the at least one inclined portion being formed into a pole piece. The deflection mechanism further comprises a compensation electrode, which is located between the pole piece and the surface of the sample and is configured to adjust a focusing position of the electron beam at which the electron beam is focused, in a condition of excitation thereof with a voltage being applied thereon, by adjusting the voltage.