Polishing Apparatus Eddy Current Sensor Zone Segmentation
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Solution Overview
Problem
Existing polishing methods for semiconductor wafers with conductive films, such as copper or tungsten, face instability in detecting the end point of polishing due to noise and interconnect patterns from underlying layers, leading to inaccurate film thickness measurements and unstable end-point detection.
Innovation Solution
A polishing apparatus and method that includes a film thickness measuring sensor, a representative value generating device, and a correction device to process signals and compute film thickness, dividing the substrate into zones and using a representative value to filter noise and correct signals, ensuring stable end-point detection and high-quality polishing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an eddy current sensor is used to measure film thickness during polishing, then real-time measurement capability is provided, but measurement precision deteriorates due to noise and interconnect patterns from underlying layers
Solution Approach 1:
The semiconductor wafer is divided into multiple zones (e.g., first zone, second zone, third zone) based on their electrical characteristics. The eddy current sensor measures film thickness separately in each zone, allowing differentiation between regions with and without underlying interconnect patterns. This segmentation enables selective use of measurement data from zones less affected by noise.
Solution Approach 2:
Different zones of the wafer are treated with different measurement strategies based on their local characteristics. Zones with underlying interconnect patterns (higher noise) are distinguished from zones without such patterns (lower noise). The system selectively weights or selects measurement data from zones with better measurement quality, applying local quality assessment to each measured region.
2Reliability
If zone division is implemented to reduce noise impact, then measurement stability improves, but device complexity increases
Solution Approach 1:
The wafer surface is divided into discrete zones that can be independently measured and evaluated. This segmentation simplifies the complex problem of noise reduction by treating different regions separately, allowing straightforward comparison and selection of reliable measurement data without requiring complex global processing algorithms.
Solution Approach 2:
The system continuously monitors film thickness measurements from multiple zones and uses this feedback to determine when polishing should stop. By comparing measurements across zones and tracking the progression of film removal, the system automatically detects the end-point condition, providing stable and reliable control without manual intervention.
3Device complexity
If smoothing over the entire wafer surface is used, then device complexity is reduced, but measurement precision deteriorates due to loss of local film thickness information
Solution Approach 1:
Instead of smoothing data across the entire wafer surface, the system divides the surface into zones and processes measurements within each zone independently. This approach preserves local film thickness information while reducing the complexity of processing by limiting the scope of analysis to smaller, manageable regions with similar characteristics.
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 solution enables stable detection of the polishing end point and accurate film thickness measurement, reducing the impact of noise and interconnect patterns, resulting in high-quality polishing without being affected by underlying layers.
Implementation Method 1
the eddy current sensor uses eddy current generated in a conductive film such as a metal film formed in a top layer of a semiconductor wafer to measure a film thickness of the conductive film
Implementation Method 2
a magnetic flux is formed by a sensor coil, and the magnetic flux passes through the conductive film of the semiconductor wafer located in front of the sensor coil, thus being alternatively changed
Data Source
AI summary
A polishing apparatus is used for polishing and planarizing a substrate such as a semiconductor wafer on which a conductive film such as a copper (Cu) layer or a tungsten (W) layer is formed. The polishing apparatus includes a polishing table having a polishing surface, a motor for rotating the polishing table, a top ring for holding a substrate and pressing the substrate against the polishing surface, a film thickness measuring sensor disposed in the polishing table for scanning a surface of the substrate, and a computing device for processing signals of the film thickness measuring sensor to compute a film thickness of the substrate.