Polishing Apparatus Zone-Specific Reference Signal Control
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Solution Overview
Problem
Conventional polishing apparatuses face challenges in accurately controlling film thickness uniformity across semiconductor wafers due to sensor signal variations and interference from conductive or magnetic materials in the top ring, leading to inconsistent film thickness measurements, especially at the wafer's periphery.
Innovation Solution
A method is introduced where reference signals are generated for different zones on the substrate, allowing for the adjustment of pressing forces to align monitoring signals with these reference signals, ensuring uniform film thickness across the substrate, and using an eddy current sensor to monitor film thickness without requiring the sensor to be close to the substrate surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single reference signal is used for all zones on the substrate, then the device complexity is reduced, but the film thickness uniformity across different zones deteriorates
Solution Approach 1:
The substrate surface is divided into multiple zones (central zone and peripheral zone), and each zone is assigned its own reference signal. This segmentation allows independent control of pressing forces in different zones, enabling uniform film thickness across the entire substrate despite variations in polishing conditions at different locations.
2Measurement precision
If the sensor effective measuring range is reduced to avoid signal drop at the periphery, then the measurement precision at the periphery is improved, but the area coverage of the sensor deteriorates
Solution Approach 1:
Different reference signals are assigned to different zones based on their specific characteristics. The central zone and peripheral zone each have tailored reference signals that account for local variations in polishing conditions, allowing the sensor to maintain accurate measurements across the entire substrate area without requiring a reduced measuring range.
3Strength
If conductive or magnetic materials are used in the top ring, then the mechanical strength and magnetic properties are improved, but the sensor signal stability deteriorates due to local signal changes
Solution Approach 1:
The invention changes the parameters of the reference signals to account for the influence of conductive or magnetic materials in the top ring. By creating zone-specific reference signals that incorporate the expected signal variations caused by these materials, the system can maintain measurement precision despite the presence of materials that affect sensor signals.
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 enables accurate and uniform film thickness control across all zones of the substrate, including the periphery, without the need for a sensor with a reduced effective measuring range, and minimizes the influence of conductive or magnetic materials, resulting in improved polishing precision and consistency.
Implementation Method 1
the sensor comprises an eddy current sensor
Data Source
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AI summary
The present invention relates to a polishing apparatus and a polishing method for polishing a substrate, such as a semiconductor wafer, to planarize the substrate. The polishing apparatus according to the present invention includes a polishing table (10) having a polishing surface, a top ring (14) configured to press the substrate against the polishing table by applying pressing forces independently to first plural zones on the substrate, a sensor (50) configured to detect a state of the film at plural measuring points, a monitoring device (53) configured to produce monitoring signals with respect to second plural zones on the substrate, respectively, a storage device configured to store plural reference signals each indicating a relationship between reference values of each monitoring signal and polishing times, and a controller configured to operate the pressing forces against the first plural zones such that the monitoring signals, corresponding respectively to the second plural zones, converge on one of the plural reference signals.