Acoustic Sensor Nanowire Structure for CMP Endpoint Detection
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Solution Overview
Problem
Chemical mechanical polishing (CMP) processes face challenges due to light scattering from slurry solutions, leading to noise in light-based endpoint detection, which affects the reliability of determining the polishing endpoint.
Innovation Solution
Incorporation of an acoustic sensor with a piezoelectric structure comprising nanowires of varying heights in a CMP apparatus, which converts sound waves into electrical signals to accurately determine the polishing endpoint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a light-based endpoint detector is used to determine the polishing endpoint, then the polishing process can be monitored, but light scattering from the slurry solution causes noise and reduces detection reliability
Solution Approach 1:
The patent replaces the optical detection system with an acoustic detection system. The acoustic sensor includes a piezoelectric structure that converts acoustic waves generated during polishing into electrical signals. This substitution eliminates the light scattering problem caused by slurry while maintaining endpoint detection capability through acoustic signal analysis.
Solution Approach 2:
The patent changes the detection parameter from optical properties (light reflection) to acoustic properties (sound wave generation). By monitoring acoustic signals instead of light signals, the system avoids interference from the slurry solution while still detecting polishing endpoint conditions through changes in acoustic characteristics.
2Reliability
If an acoustic sensor with piezoelectric structure is used to detect endpoint, then noise interference is reduced and signal sensitivity is improved, but the device complexity increases
Solution Approach 1:
The piezoelectric structure is segmented into multiple nanowires with different heights. This segmentation creates multiple sensing elements that can be independently optimized for different frequency ranges or signal strengths, improving overall detection reliability while allowing each segment to be simpler in design.
Solution Approach 2:
The patent employs nanowires with asymmetric height distribution - some nanowires are taller than others. This asymmetric design creates a gradient structure that enhances acoustic signal detection by optimizing the response to different vibration modes and frequencies, improving sensitivity without requiring a uniformly complex structure throughout.
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
Enhances the reliability of endpoint detection by improving signal sensitivity and reducing noise interference, ensuring precise control of the polishing process.
Implementation Method 1
an acoustic sensor with a piezoelectric structure comprising nanowires of varying heights in a CMP apparatus, which converts sound waves into electrical signals
Data Source
AI summary
An acoustic sensor includes a first electrode, a second electrode spaced apart from the first electrode in a first direction, and a first piezoelectric structure between the first electrode and the second electrode, where the first piezoelectric structure includes first nanowires extending in the first direction and having a first height and second nanowires extending in the first direction and having a second height that is less than the first height.