Polarization Imaging for Semiconductor Defect Detection
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Solution Overview
Problem
Current inspection systems for semiconductor devices struggle to reliably identify both macro defects and exposure or defocus defects using a single optical system, as they are typically dedicated to one type of defect and lack the capability to effectively distinguish between polarization-dependent and independent defects.
Innovation Solution
An inspection system employing a light source, a first polarizing filter, and a second polarizing filter positioned at a selected relative angle to detect polarization-dependent defects such as defocus and exposure defects, while also identifying macro defects like chips, cracks, and scratches, by capturing and analyzing differential images to determine the presence of defects based on changes in pixel intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dedicated inspection systems are used for macro defects, then macro defect detection capability is improved, but the ability to identify exposure or defocus defects deteriorates
Solution Approach 1:
The inspection system is designed to perform multiple functions using a single optical system. By incorporating polarization-sensitive detection capabilities, the system can simultaneously detect macro defects (chips, cracks, scratches) and exposure/defocus defects, eliminating the need for separate dedicated inspection systems for each defect type.
Solution Approach 2:
The system changes the parameter of light polarization to differentiate between defect types. By analyzing polarization-dependent reflectivity changes, the system can distinguish polarization-dependent defects (exposure/defocus defects) from polarization-independent defects (macro defects), enabling a single system to detect both categories effectively.
2Device complexity
If a single optical system is used for both macro defects and exposure/defocus defects, then device complexity is reduced, but measurement precision for distinguishing defect types deteriorates
Solution Approach 1:
Polarization-sensitive detection acts as an intermediary mechanism that enables a single optical system to distinguish between different defect types. The polarization state of reflected light serves as a mediator that carries information about the defect type, allowing the system to maintain high measurement precision while using only one inspection system.
3Reliability
If traditional inspection methods are used, then macro defects can be detected, but exposure and defocus defects require separate precision metrology tools increasing inspection time
Solution Approach 1:
The system merges macro defect inspection and exposure/defocus defect inspection into a single integrated process. By using polarization-sensitive detection in conjunction with traditional optical inspection, the system simultaneously identifies both defect types in one inspection pass, significantly reducing the total inspection time while maintaining reliability for both defect categories.
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
Enables simultaneous or successive detection of defocus, exposure, and macro defects, improving the reliability and efficiency of semiconductor device inspection by correlating image intensity with defect presence, thereby enhancing yield and quality in manufacturing processes.
Implementation Method 1
The polarizer and analyzer, are angularly arranged with respect to one another such that an image intensity of an image captured by the optical sensor is at least partially correlated with the presence of polarization dependent defects on the substrate under test
Implementation Method 2
an optical sensor that receives light reflected from the substrate
Data Source
AI summary
Methods of monitoring critical dimensions in a semiconductor fabrication process include capturing at least one image of a first structure that has an effect on the polarization state of light reflected therefrom. For at least some of the first structure images, a value is calculated indicative of intensity of light reflected from the first structure. A critical dimension of the first structure is obtained and correlated with the calculated value. At least one image of a subsequent structure is captured. A determination is made, based at least in part on the calculated value, of a critical dimension of the subsequent structure.