Oriented Wafer Loading for CMP Thickness Asymmetry Correction
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Solution Overview
Problem
Chemical mechanical polishing (CMP) systems face challenges in achieving uniformity due to asymmetric removal profiles and initial thickness profiles of substrates, leading to highly asymmetric final thickness profiles.
Innovation Solution
A system that includes a metrology station for measuring substrate thickness profiles, a carrier head with a membrane for pressure application, and a controller to orient the substrate based on the removal profile of the carrier head, ensuring that the removal profile and substrate thickness profile partially cancel each other out, reducing asymmetry through precise orientation and pressure control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the substrate is polished using a conventional carrier head with uniform pressure distribution, then the polishing process is simple and fast, but the final thickness profile becomes highly asymmetric due to asymmetric removal profiles and initial substrate thickness variations
Solution Approach 1:
The carrier head is divided into multiple independently controllable pressure zones. Each zone can apply different pressure levels to different regions of the substrate, allowing asymmetric pressure distribution to compensate for asymmetric thickness variations and achieve more uniform final thickness profiles
Solution Approach 2:
Different regions of the carrier head are assigned different pressure characteristics tailored to the specific thickness variations in corresponding substrate regions. This local customization of pressure application allows targeted correction of thickness asymmetries while maintaining overall polishing efficiency
2Manufacturing precision
If the substrate orientation is fixed during loading, then the loading process is simple and quick, but the asymmetry in the final thickness profile cannot be corrected
Solution Approach 1:
The substrate thickness profile is measured and analyzed before the polishing process begins. Based on this preliminary information, the optimal substrate orientation is calculated in advance, and the carrier head is pre-configured with the corresponding pressure distribution pattern, eliminating the need for complex real-time adjustments during loading
Solution Approach 2:
The system uses measurement feedback from the substrate thickness profile to dynamically determine the optimal substrate orientation and pressure distribution. This closed-loop control allows the system to automatically compensate for thickness asymmetries by adjusting substrate orientation and pressure patterns based on actual measured data
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 improves within-wafer and wafer-to-wafer uniformity by aligning the substrate orientation with the carrier head's removal profile, resulting in a more symmetrical final thickness profile during polishing.
Implementation Method 1
a sensor configured to measure a thickness profile of a substrate
Implementation Method 2
a carrier head having a membrane configured to apply pressure to the substrate in the carrier head
Implementation Method 3
The exposed surface of the substrate is typically placed against a rotating polishing pad. A polishing slurry with abrasive particles is typically supplied to the surface of the polishing pad
Data Source
AI summary
A method for chemical mechanical polishing includes receiving an angular removal profile for a carrier head and an angular thickness profile of a substrate. Prior to polishing the substrate, a desired angle of the carrier head relative to the substrate is selected for loading the substrate into the carrier head. Selecting the desired angle is performed based on a comparison of the angular removal profile for the carrier head and the angular thickness profile of the substrate to reduce angular non-uniformity in polishing. The carrier head is rotated to receive the substrate at the desired angle, the substrate is transferred to the carrier head and loaded in the carrier head with the carrier head at the desired angle relative to the substrate, and the substrate is polished.