Beam-Tilt Deflector Layout for Low-Aberration Charged-Particle Imaging
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Solution Overview
Problem
Current charged-particle beam inspection systems face challenges in maintaining image resolution and throughput when inspecting complex structures like angled holes and vias due to off-axis aberrations introduced by beam-tilting, which affects the accuracy and yield in defect detection during integrated circuit manufacturing.
Innovation Solution
A charged-particle beam apparatus with a configuration that includes multiple deflectors and a controller to adjust the beam-tilt angle, allowing the charged-particle beam to pass through a wobbling center of the objective lens, minimizing aberrations and maintaining image resolution while scanning complex structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If beam-tilting is performed to improve accessibility of complex structures, then inspection capability is improved, but off-axis aberrations increase and render the technique inadequate
Solution Approach 1:
The beam deflection function is segmented into multiple independent deflectors (first deflector for initial deflection, second deflector for correction, third deflector for wobbling center adjustment). Each deflector performs a specific function, allowing the system to achieve beam tilting while maintaining image quality by compensating for aberrations introduced at each stage.
Solution Approach 2:
The patent introduces intermediate deflectors between the beam source and the sample that act as mediators to control and correct the beam path. These deflectors serve as intermediary elements that enable beam tilting while simultaneously compensating for the resulting aberrations, thus resolving the contradiction between accessibility and image resolution.
2Adaptability or versatility
If beam-tilt angle is increased to access angled holes and vias, then accessibility to complex structures is improved, but off-axis aberrations worsen
Solution Approach 1:
The patent applies preliminary anti-action by using the second and third deflectors to pre-compensate for the off-axis aberrations before the beam reaches the sample. The second deflector corrects the beam path, and the third deflector adjusts the wobbling center, thereby counteracting the harmful effects of beam tilting before they can degrade image quality.
Solution Approach 2:
The system dynamically changes multiple parameters including beam deflection angles, wobbling center position, and deflector excitation signals to optimize the balance between beam tilt angle and image resolution. By adjusting these parameters in coordination, the system can access complex structures while maintaining acceptable image quality.
3Manufacturing precision
If multiple deflectors are added to correct aberrations, then image resolution is maintained, but device complexity increases
Solution Approach 1:
The patent makes the deflectors multi-functional: they simultaneously perform beam tilting, aberration correction, and wobbling center adjustment. This universality reduces the need for separate dedicated components for each function, thereby managing device complexity while achieving multiple objectives.
Solution Approach 2:
The patent merges the functions of beam deflection and aberration correction into a coordinated system of deflectors that work together. Rather than using completely separate systems for tilting and correction, the deflectors are integrated and controlled in combination, reducing overall system complexity while maintaining image resolution.
4Area of stationary object
If beam deflection is used to scan field-of-view, then inspection coverage is improved, but probe spot position stability deteriorates
Solution Approach 1:
The patent employs feedback control through the third deflector that continuously monitors and adjusts the wobbling center position based on the beam's current state. This feedback mechanism ensures that as the beam scans across the field-of-view, the probe spot position remains stable by dynamically compensating for any deviations caused by beam tilting.
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
The solution enables high-resolution imaging and improved throughput by reducing off-axis aberrations and maintaining the probe spot position, enhancing the accuracy and yield in defect detection for complex integrated circuit structures.
Implementation Method 1
a charged-particle source configured to generate a charged-particle beam along a primary optical axis
Implementation Method 2
a first deflector located between the charged-particle source and an objective lens and configured to deflect the charged-particle beam away from the primary optical axis
Implementation Method 3
a second deflector located substantially at a focal plane of the objective lens and configured to deflect the charged-particle beam back towards the primary optical axis
Implementation Method 4
a third deflector located substantially at a principal plane of the objective lens, wherein the third deflector is configured to shift a wobbling center of the objective lens to an off-axis wobbling location
Implementation Method 5
pass through the off-axis wobbling location to land on a surface of a sample at a first landing location and having a beam-tilt angle
Data Source
AI summary
Systems and methods of imaging a sample using a tilted charged-particle beam. The apparatus may comprise a first deflector located between the charged-particle source and an objective lens and configured to deflect the charged-particle beam away from the primary optical axis; a second deflector located substantially at a focal plane of the objective lens and configured to deflect the charged-particle beam back towards the primary optical axis; and a third deflector located substantially at a principal plane of the objective lens, wherein the third deflector is configured to shift a wobbling center of the objective lens to an off-axis wobbling location, and wherein the first and the second deflectors are configured to deflect the charged-particle beam to pass through the off-axis wobbling location to land on a surface of a sample at a first landing location and having a beam-tilt angle.