Optical Inspection Polarization Control for Semiconductor Wafer Defect Detection
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Solution Overview
Problem
The increasing complexity and density of semiconductor wafers pose challenges in inspecting microscopic structural elements, requiring an inspection system that can provide detailed information about the samples.
Innovation Solution
An optical inspection system utilizing controlled illumination and collection polarization, featuring multiple polarizers such as half-wave plates, quarter-wave plates, and inhomogeneous polarizers to control and adjust polarization states, enhancing signal detection and noise reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical inspection methods are used on complex and dense semiconductor wafers, then the inspection system structure remains simple, but the measurement precision and ability to detect microscopic structural elements deteriorates
Solution Approach 1:
The patent applies parameter changes by systematically varying polarization states (illumination polarization, collection polarization, and analyzer polarization) to enhance the detection capability for different defect types. By controlling polarization parameters through wave plates and polarizers, the system can differentiate between various defect characteristics on semiconductor wafers, thereby improving measurement precision without requiring fundamental changes to the optical system architecture.
2Reliability
If multiple polarizers are introduced to control illumination and collection polarization, then the signal-to-noise ratio improves, but the device complexity increases
Solution Approach 1:
The patent implements universality by designing an optical inspection system where multiple polarizers serve multiple functions simultaneously. The same polarization control components (wave plates, polarizers) are used for both illumination polarization control and collection polarization control, as well as for noise suppression and signal enhancement. This multi-functional approach improves the signal-to-noise ratio while minimizing the increase in device complexity.
3Measurement precision
If polarization control is implemented to reduce radiation noise, then the measurement precision improves, but the ease of operation deteriorates
Solution Approach 1:
The patent applies feedback by implementing a control system that monitors and adjusts polarization states to optimize signal-to-noise ratio. The system can automatically adjust wave plate orientations and polarizer angles based on detected signal characteristics, reducing radiation noise while eliminating the need for manual polarization alignment. This feedback mechanism maintains measurement precision while significantly improving ease of operation.
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 system increases the signal-to-noise ratio by enhancing optical signals of defects and reducing radiation noise, providing comprehensive inspection capabilities for complex semiconductor wafers.
Implementation Method 1
multiple polarizers that are configured to (a) set a polarization of the illumination light beam by selectively introducing, under a control of a control unit, at least one illumination optics polarization change, and (b) set a polarization of the at least one detected light beam by selectively introducing, under a control of the control unit, at least one collection optics polarization change
Data Source
AI summary
An optical inspection system that may include an illumination optics configured to generate an illumination light beam and to illuminate a sample with the illumination light beam; at least one collection optics configured to collect light from the sample; at least one detector configured to detect at least one detected light beam outputted from the at least one collection optics; multiple polarizers that are configured to (a) set a polarization of the illumination light beam by selectively introducing, under a control of the control unit, at least one illumination optics polarization change, and (b) set a polarization of the at least one detected light beam by selectively introducing, under a control of the control unit, at least one collection optics polarization change. The multiple polarizers may include one or more illumination half-wave plates, one or more quarter-wave plates, and one or more inhomogeneous polarizers.