CMP Wafer Loading Orientation for 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 thickness profile partially cancel each other out, reducing substrate asymmetry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If substrate is polished using conventional CMP method, then planarization is achieved, but asymmetric removal profile and initial thickness profile lead to highly asymmetric final thickness profile
Solution Approach 1:
The system measures the substrate thickness profile before polishing and calculates the optimal orientation angle in advance. The substrate is then oriented at this predetermined angle in the carrier head before polishing begins, allowing the asymmetric removal profile to compensate for the initial thickness asymmetry and achieve a more uniform final thickness profile.
Solution Approach 2:
The system changes the orientation parameter of the substrate in the carrier head based on the measured thickness profile. By adjusting the angular position of the substrate relative to the carrier head's removal profile, the system optimizes the polishing outcome to achieve better thickness uniformity across the wafer.
2Manufacturing precision
If substrate orientation is adjusted to compensate for asymmetric removal profile, then within-wafer and wafer-to-wafer uniformity is improved, but measurement and calculation complexity increases
Solution Approach 1:
The system incorporates a metrology station that measures the substrate thickness profile before polishing. This measurement feedback is used to calculate the optimal orientation angle, which is then applied by the robotic arm when loading the substrate into the carrier head. This closed-loop feedback mechanism enables automatic compensation for asymmetric removal profiles while maintaining manageable system complexity.
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 carrier head on the polishing surface, the carrier head having a membrane configured to apply pressure to the substrate in the carrier head
Implementation Method 2
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.