Wafer Sensor Chattering Correction via Edge Timing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In chemical mechanical polishing (CMP), determining the endpoint of the polishing process is challenging due to variations in material removal rates caused by initial thickness, slurry composition, polishing pad conditions, and relative speed, leading to uncertainties in achieving desired flatness or thickness, which can result in over- or under-polishing and electrical issues.
Innovation Solution
An in-situ monitoring system with a sensor that sweeps across the substrate generates signal values based on layer thickness, detecting the leading and trailing edges of the substrate or retaining ring, and calculates positions using the times these edges cross the sensor, reducing chattering and improving edge reconstruction accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If in-situ monitoring system sweeps sensor across substrate to detect polishing endpoint, then measurement precision is improved, but chattering occurs causing position determination errors
Solution Approach 1:
The patent introduces an intermediary computational process that uses signal processing and mathematical modeling to mediate between the raw sensor signals and position determination. The system uses a polynomial model to represent the relationship between sensor position and signal values, and applies correction algorithms to eliminate chattering effects, thereby achieving reliable position determination despite the noisy raw signals.
Solution Approach 2:
The system implements feedback by continuously monitoring the sensor signals during the sweep, detecting chattering patterns, and applying real-time corrections to the position calculation. The correction process uses the detected chattering characteristics to adjust the position determination, ensuring accurate results even when chattering occurs during the polishing process.
2Manufacturing precision
If polishing process continues to achieve desired flatness, then manufacturing precision is improved, but over-polishing or under-polishing occurs due to material removal rate variations, worsening production efficiency
Solution Approach 1:
The patent replaces the traditional time-based or thickness-based endpoint detection with an in-situ optical monitoring system that directly measures the substrate surface characteristics during polishing. This substitution allows real-time detection of the polishing endpoint based on actual surface flatness rather than relying on predetermined polishing times or estimated material removal rates, thereby preventing both over-polishing and under-polishing.
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 approach significantly reduces chattering, enabling more accurate and reliable determination of sensor positions and edge reconstruction, making the polishing process more consistent and less dependent on process conditions.
Implementation Method 1
with optical or eddy current sensors, in order to detect the polishing endpoint
Data Source
AI summary
A method of controlling polishing includes sweeping a sensor of an in-situ monitoring system across a substrate as a layer of the substrate undergoes polishing, generating from the in-situ monitoring system a sequence of signal values that depend on a thickness of the layer, detecting from the sequence of signal values, a time that the sensor traverses a leading edge of the substrate or a retaining ring and a time that the sensor traverses a trailing edge of the substrate or retaining ring; and for each signal value of at least some of the sequence of signal values, determining a position on the substrate for the signal value based on the time that the sensor traverses the leading edge and the time that the sensor traverses a trailing edge.