Calibrating WIS Camera Spectral Responsivity
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Solution Overview
Problem
Conventional wafer inspection system (WIS) modules produce non-uniform inspection results due to hardware differences, such as spectral responsivity variations, leading to inconsistent interpretation of color differences and film thickness or critical dimension measurements across multiple modules.
Innovation Solution
A system and method for calibrating multiple spectral band values using a test wafer with predetermined patterns of thickness or color changes to generate spectral band offset values, which are applied to compensate for responsivity differences between camera systems in WIS modules, ensuring uniform inspection results by generating calibrated spectral band values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple WIS modules are used to inspect substrates, then inspection productivity is improved, but measurement precision deteriorates due to spectral responsivity differences between modules
Solution Approach 1:
The patent applies parameter changes by introducing spectral band offset values that adjust the spectral responsivity parameters of each WIS module. These offset values are determined through calibration using a reference wafer and are applied to correct the spectral band values obtained from substrates, ensuring consistent measurements across multiple modules while maintaining high inspection productivity
Solution Approach 2:
The patent uses an intermediary calibration process involving a reference wafer with known spectral characteristics. This reference wafer serves as a mediator to determine the spectral band offset values for each WIS module, enabling the system to compensate for hardware differences and achieve uniform measurement precision across all modules
2Measurement precision
If spectral band offset values are applied to compensate for responsivity differences, then measurement precision is improved, but device complexity increases due to calibration requirements
Solution Approach 1:
The patent implements preliminary action by performing calibration of spectral band offset values before actual substrate inspection. The offset values are determined in advance using a reference wafer and stored for subsequent application during normal operation, eliminating the need for complex real-time calibration and reducing operational complexity
Solution Approach 2:
The patent uses a reference wafer as a copy or representation of ideal spectral characteristics. By comparing actual WIS module measurements against this reference copy, the system can determine correction offset values without requiring complex theoretical models or multiple reference standards
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 calibration method enables uniform inspection results across multiple WIS modules by compensating for spectral responsivity differences, allowing a common model to accurately convert color differences to film thickness or critical dimension values, thereby improving process control and defect detection.
Implementation Method 1
a camera system configured to obtain multiple spectral band values from the substrate when the substrate is disposed within the WIS module
Implementation Method 2
the controller is configured to apply a plurality of multiple spectral band offset values to the multiple spectral band values received from the camera system to generate calibrated multiple spectral band values, which compensate for spectral responsivity differences between the camera systems included within the plurality of WIS modules
Data Source
AI summary
Various embodiments of systems and methods for calibrating wafer inspection system modules are disclosed herein. More specifically, the present disclosure provides various embodiments of systems and methods to calibrate the multiple spectral band values obtained from a substrate by a camera system included within a WIS module. In one embodiment, multiple spectral band values are red, green, and blue (RGB) values. As described in more detail below, the calibration methods disclosed herein may use a test wafer having a predetermined pattern of thickness changes or color changes to generate multiple spectral band offset values. The multiple spectral band offset values can be applied to the multiple spectral band values obtained from the substrate to generate calibrated RGB values, which compensate for spectral responsivity differences between camera systems included within a plurality of WIS modules.