Acoustic Wafer Orientation Detection During CMP Polishing
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Solution Overview
Problem
Existing chemical mechanical polishing (CMP) processes face challenges in determining substrate orientation during polishing, leading to asymmetric removal profiles and initial non-uniform thickness, which complicates material removal accuracy and uniformity.
Innovation Solution
An in-situ acoustic monitoring system is integrated into a CMP apparatus to detect periodic variations in acoustic signals from the substrate-pad interface, allowing determination of substrate angular orientation and precession rate, enabling precise compensation for asymmetry through controlled chamber pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional CMP monitoring methods are used, then the polishing process can be monitored, but substrate orientation cannot be accurately determined leading to asymmetric removal profiles
Solution Approach 1:
The patent replaces mechanical orientation sensing methods with acoustic field-based detection. Acoustic sensors detect orientation-dependent acoustic signals generated during polishing, converting mechanical orientation measurement into an acoustic field measurement problem, thereby achieving non-contact, high-precision orientation detection without mechanical wear
Solution Approach 2:
The patent utilizes the change in acoustic signal characteristics (amplitude, frequency, or phase) as a function of substrate angular orientation. By monitoring these parameter variations in the acoustic signals, the system can determine substrate orientation dynamically during polishing, enabling real-time compensation for asymmetric removal profiles
2Manufacturing precision
If acoustic sensors are added to determine substrate orientation, then polishing uniformity improves, but device complexity increases
Solution Approach 1:
The acoustic sensors serve multiple functions: they monitor polishing rate through acoustic emission intensity, determine substrate orientation through orientation-dependent signal variations, and detect material transitions through changes in acoustic properties. This multi-functionality reduces the need for separate sensing systems and justifies the added complexity through consolidated monitoring capabilities
Solution Approach 2:
The polishing process itself generates the acoustic signals needed for monitoring and orientation determination. The mechanical interaction between the polishing pad and substrate naturally produces acoustic emissions that contain information about orientation, material removal rate, and process state, eliminating the need for external excitation sources or separate measurement systems
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
Improves wafer-to-wafer and within-wafer polishing uniformity by accurately determining substrate orientation, reducing angularly dependent non-uniformity without requiring new hardware, and enhancing material removal accuracy.
Implementation Method 1
The acoustic signals originate from the interface between the substrate surface and the polishing pad and vary with time according to the polishing stage and material exposed on the substrate surface
Data Source
AI summary
A chemical mechanical polishing apparatus includes a platen to support a polishing pad, a carrier head to hold a surface of a substrate against the polishing pad, a motor to generate relative motion between the platen and the carrier head so as to polish an overlying layer on the substrate, an in-situ acoustic monitoring system comprising an acoustic sensor that receives acoustic signals from the surface of the substrate, and a controller configured to determine a angular orientation of the substrate based on received acoustic signals from the in-situ acoustic monitoring system.