Grinding Endpoint Detection via Thickness Extremum Filtering
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Solution Overview
Problem
In semiconductor manufacturing, accurately stopping the grinding process to remove molding compound and dielectric materials from thin layers is crucial for process yield, but existing methods lack precision, leading to potential damage and inefficiencies.
Innovation Solution
An endpoint detection system is implemented, using an EPD sensor and controller to sense and analyze thickness signals from a reconstructed wafer, determining thickness extrema to accurately determine the endpoint of the grinding process, ensuring precise stopping and protecting conductive pillars and semiconductor dies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional grinding control methods are used, then the grinding process can be completed, but the endpoint detection precision is insufficient leading to potential damage to thin layers
Solution Approach 1:
The patent implements real-time feedback by continuously monitoring thickness during grinding and comparing it against target values. The system adjusts grinding parameters based on the feedback signal from the thickness measurement, enabling precise endpoint detection and preventing damage to thin layers through closed-loop control.
Solution Approach 2:
The patent replaces traditional mechanical endpoint detection methods with optical or electromagnetic thickness measurement systems. This substitution enables non-contact, high-precision thickness monitoring during grinding, significantly improving endpoint detection accuracy and reducing the risk of damage to thin layers.
2Productivity
If traditional grinding control methods are used, then the process can proceed, but processing efficiency is reduced due to lack of precise endpoint detection
Solution Approach 1:
The patent maintains continuous thickness measurement and grinding operation simultaneously, eliminating idle time for intermediate inspections. The real-time monitoring system allows the grinding process to proceed continuously with automatic endpoint detection, maximizing productivity and minimizing time loss.
Solution Approach 2:
The system performs automatic endpoint detection and self-adjustment without requiring manual intervention. The thickness measurement system continuously monitors the grinding process and automatically determines the endpoint, freeing operators from time-consuming manual measurements and improving overall processing efficiency.
3Measurement precision
If simple thickness monitoring is used, then the system remains simple, but it cannot accurately detect endpoint among multiple dies with varying thicknesses
Solution Approach 1:
The patent divides the wafer into multiple measurement zones corresponding to individual dies or die groups. The thickness measurement system separately monitors each zone, allowing precise endpoint detection for each die even when thicknesses vary. This segmentation enables accurate local measurements without requiring complex global analysis.
Solution Approach 2:
The system dynamically adjusts measurement parameters such as measurement frequency, threshold values, and sampling rates based on the grinding stage and die characteristics. This adaptive parameter adjustment improves endpoint detection accuracy for varying die thicknesses while maintaining manageable system complexity through intelligent control algorithms.
Data Source
AI summary
An apparatus for detecting an endpoint of a grinding process includes a connecting device, a timer and a controller. The connecting device is connected to a sensor that periodically senses an interface of a reconstructed wafer comprising a plurality of dies of at least two types to generate a thickness signal comprising thicknesses from a surface of an insulating layer of the reconstructed wafer to the interface of the reconstructed wafer. The timer is configured to generate a clock signal having a plurality of pulses with a time interval. The controller is coupled to the sensor and the timer, and configured to filter the thickness signal according to the clock signal to output a thickness extremum among the thicknesses in the thickness signal within each time interval, wherein the thickness signal after the filtering is used to determine the endpoint of the grinding process being performed on the reconstructed wafer.