Electro-Optic Polarization Control for Semiconductor Wafer Inspection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current defect inspection methods for semiconductor wafers often require optimizing inspection conditions for each type of defect, leading to potential misses and reduced throughput due to the need for switching polarization conditions using optical switches.
Innovation Solution
An optical inspection device that adjusts light polarization using an electro-optic device based on control unit instructions, allowing for simultaneous inspection with multiple illumination conditions such as polarization, power, and angle, without the need for optical switch switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple inspection conditions are used to detect various defects, then detection accuracy is improved, but inspection throughput is reduced due to the need to switch polarization conditions using optical switches
Solution Approach 1:
The patent replaces the mechanical optical switch system with an electro-optic device (Pockels cell) that uses electrical fields to control polarization. This substitution eliminates the mechanical moving parts and switching delays, allowing for rapid polarization state changes that maintain both high detection accuracy across multiple conditions and high inspection throughput.
Solution Approach 2:
The patent changes the control parameter from mechanical switching positions to electrical voltage applied to the Pockels cell. By applying different voltages, the polarization state of the illumination light can be rapidly changed between multiple conditions (e.g., s-polarization, p-polarization, circular polarization) without physical movement, thereby improving both detection comprehensiveness and inspection speed.
2Adaptability or versatility
If optical switches are used to switch polarization conditions, then multiple inspection parameters can be applied, but device complexity increases
Solution Approach 1:
The patent replaces complex mechanical optical switching systems with a simpler electro-optic modulation system. The Pockels cell requires only electrical voltage control to achieve the same polarization switching function, significantly reducing mechanical complexity while maintaining the ability to apply multiple inspection parameters.
Solution Approach 2:
The Pockels cell serves multiple functions: it can generate various polarization states (linear, circular, elliptical) and control illumination intensity by adjusting the voltage. This single device replaces what would otherwise require multiple separate optical switches and polarization control elements, reducing overall system complexity while maintaining versatility.
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
Improves throughput by enabling the detection of defects under various conditions in a single inspection, reducing the likelihood of missed defects and optimizing sensitivity across different polarization states and angles.
Implementation Method 1
an electro-optic device unit to which the light generated by the light source unit is inputted. On the basis of the instructions from the control unit, the electro-optic device unit adjusts the light to be in a desired polarization state
Data Source
AI summary
Proposed is an inspection device that is provided with: an illuminating optical unit that irradiates a discretionary region of a sample with light; a control unit that gives instructions to the illuminating optical unit; and at least one detection unit that detects light transmitted from the sample. The illuminating optical unit includes a light source unit that generates light, and an electrooptic element unit to which the light generated by the light source unit is inputted, and on the basis of the instructions given from the control unit, the electrooptic element unit adjusts the light to be in a desired polarization state, said light having been generated by the light source unit, and irradiates the sample with the light.