Wafer Warp Measurement Correction for Holding Deformation
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Solution Overview
Problem
The deformation caused by holding a wafer periphery during measurement affects the reproducibility of Warp values across different systems, making it difficult to determine the true Warp value and system reliability due to varying measurement systems' influences.
Innovation Solution
A method using a flatness measurement system with a first and second optical system to measure surface variations on both main surfaces, calculate the periphery-holding deformation amount, and subtract it from the Warp value to obtain an actual Warp value, minimizing system differences and enhancing reproducibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the periphery of the wafer is held by grippers at three locations to enable measurement, then the wafer can be positioned and measured, but the wafer is deformed by external force applied to the three points, causing the measured Warp value to differ from the actual Warp value and reducing reproducibility across different measurement systems
Solution Approach 1:
The invention extracts and separates the deformation component caused by periphery holding from the total measured Warp value. By measuring surface variations with optical systems and calculating the deformation amount, the method isolates the holding-induced deformation to subtract it from the raw Warp measurement, obtaining the actual Warp value free from holding effects.
Solution Approach 2:
The invention introduces surface variation measurements as an intermediary step between the holding operation and the Warp measurement. By using optical systems to measure surface variations on both main surfaces of the wafer, the method creates an intermediate data set that enables calculation of the deformation amount, serving as a mediator to correct the final Warp value.
2Productivity
If multiple measurement systems are used to measure Warp values, then more measurements can be obtained, but the deformation by holding the wafer periphery causes different deformation amounts among systems due to anisotropic influence from the elastic modulus of silicon single crystal, making it impossible to know the true Warp value
Solution Approach 1:
The invention enables each measurement system to self-correct its measurements by using its own optical systems to measure surface variations and calculate its own deformation amount. This self-service approach allows each system to independently obtain the actual Warp value by subtracting its specific holding-induced deformation from its raw Warp measurement, ensuring accuracy without relying on other systems.
Solution Approach 2:
The invention changes the measurement parameters by measuring not only the Warp value but also surface variations on both main surfaces of the wafer. By adding these additional measurement parameters, the method enables calculation of the deformation amount and subsequent correction of the Warp value, transforming the measurement process from direct Warp reading to corrected Warp determination.
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 method allows for the accurate measurement of actual wafer Warp values by accounting for and eliminating the deformation caused by the holding process, reducing system variability and improving reproducibility across multiple measurement systems.
Implementation Method 1
a first optical system and a second optical system respectively located on a first main surface and a second main surface of the wafer
Data Source
AI summary
A method for measuring a wafer profile while holding a periphery of the wafer by using a flatness measurement system, including first and second optical systems respectively located on first and second main surfaces of the wafer, the method including: a first step measuring each surface variation on the main surfaces using one of the optical systems; a second step of calculating a periphery-holding deformation amount, caused by holding the wafer periphery, through utilization of the surface variations measured with the optical system; and a third step of calculating an actual wafer Warp value through subtraction of the periphery-holding deformation amount from a Warp value outputted by the flatness measurement system. This provides a method for measuring a wafer profile to enable measurement of actual wafer Warp value by using a flatness measurement system, and to successfully acquire a Warp value with little influence from a difference among systems.