Reflected Light Path for Charge Control in E-Beam Inspection
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Solution Overview
Problem
In semiconductor IC manufacturing, charged particles can accumulate on samples during electron beam inspection, leading to image quality issues due to large beam currents, and existing solutions face challenges in effectively illuminating the sample with a light beam to control these charges, especially with the dimensions of inspection tools limiting access.
Innovation Solution
A charged particle assessment system comprising a sample holder, a charged particle-optical device projecting a beam, and a projection assembly that directs a light beam to reflect off a facing surface within the system, allowing the light to reach the sample and control charge accumulation, even in narrow gaps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a light beam is directly projected onto the sample to control charge accumulation, then charge control effectiveness is improved, but the device complexity and difficulty of implementation increase due to the narrow gap between the electron-optical device and sample
Solution Approach 1:
The patent introduces an intermediary solution by using the facing surface of the electron-optical device as a reflective surface. Instead of directly projecting light onto the sample through the narrow gap, the system reflects light off the facing surface to illuminate the sample indirectly. This mediator (facing surface) enables charge control without requiring direct light access through the constrained geometry.
Solution Approach 2:
The patent changes the illumination approach from a direct linear path to a multi-dimensional path involving reflection. By utilizing the facing surface as a reflective element, the light path is extended and redirected, allowing illumination to reach the sample from a different spatial dimension without requiring direct access through the narrow gap.
2Measurement precision
If the gap between the electron-optical device and sample is reduced to improve inspection resolution, then measurement precision is improved, but the ability to illuminate the sample with a light beam deteriorates
Solution Approach 1:
The facing surface serves as an intermediary that enables light delivery despite the reduced gap. By reflecting light off this surface, the system bypasses the geometric constraint imposed by the narrow gap, maintaining both high resolution (through small gap) and effective illumination (through reflection).
Solution Approach 2:
Instead of trying to project light directly onto the sample from outside the gap, the system inverts the approach by using the existing facing surface within the gap as a reflective element. This inverted strategy transforms the facing surface from merely a structural component into an active illumination element.
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 improves defect contrast and image quality by effectively illuminating the sample, enhancing the detection of micro and nano-scale defects without requiring direct incidence of the light beam, thus addressing the limitations of existing systems.
Implementation Method 1
the light beam reflects at least twice off the facing surface up-beam, with respect to the light path, of being incident on the portion of the surface of the sample
Implementation Method 2
control the accumulated charges due to effects such as photoconductivity, photoelectric, or thermal effects
Implementation Method 3
The interactions between the material structure at the probing spot and the landing electrons from the beam of electrons cause electrons to be emitted from the surface, such as secondary electrons, backscattered electrons or Auger electrons
Implementation Method 4
The generated secondary electrons may be emitted from the material structure of the sample. By scanning the primary electron beam as the probing spot over the sample surface, secondary electrons can be emitted across the surface of the sample
Implementation Method 5
a projection assembly arranged to direct a light beam along a light path such that the light beam reflects at least twice off the facing surface up-beam
Data Source
AI summary
The embodiments of the present disclosure provide a charged particle assessment system comprising: a sample holder configured to hold a sample having a surface; a charged particle-optical device configured to project a charged particle beam towards the sample, the charged particle beam having a field of view corresponding to a portion of the surface of the sample, the charged particle-optical device having a facing surface facing the sample holder; and a projection assembly arranged to direct a light beam along a light path such that the light beam reflects off the facing surface up-beam, with respect to the light path, of being incident on the portion of the surface of the sample.