CMP Carrier Head Pressure Zoning for Angular Thickness Control
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Solution Overview
Problem
Chemical mechanical polishing (CMP) systems face challenges in achieving uniform material removal rates due to variations in substrate thickness, slurry composition, polishing pad conditions, and load, leading to angular asymmetry and inconsistencies in polishing profiles.
Innovation Solution
A control model that adjusts pressures across multiple zones on the carrier head based on the substrate's orientation relative to the carrier head over time, using a stored function to calculate polishing rates and pressures that minimize the difference between the expected and target thickness profiles, thereby correcting asymmetry and achieving a desired polishing endpoint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If uniform pressure is applied across the carrier head, then the polishing process is simple to control, but angular asymmetry and non-uniform material removal occur due to substrate precession and varying orientations
Solution Approach 1:
The carrier head is divided into multiple independently controllable zones (e.g., four quadrants) that can apply different pressures to different angular regions of the substrate. This segmentation allows the system to compensate for angular asymmetry by applying higher pressure to regions requiring more material removal and lower pressure to regions requiring less removal, thereby achieving uniform thickness profiles despite substrate precession and orientation variations.
Solution Approach 2:
Each zone on the carrier head is assigned a specific pressure value that is optimized for its angular position and the substrate's orientation at that position. This local quality approach ensures that each region of the substrate receives the appropriate pressure to achieve the desired material removal rate, correcting angular asymmetry while maintaining overall thickness uniformity.
2Manufacturing precision
If the substrate rotates relative to the carrier head, then complete coverage of the polishing pad is achieved, but the polishing rate varies angularly due to changing substrate orientation
Solution Approach 1:
The pressure applied by each zone is dynamically adjusted based on the real-time orientation of the substrate relative to the carrier head. As the substrate rotates and changes orientation, the control system updates the pressure distribution across zones to maintain consistent material removal rates. This dynamic adaptation allows the system to compensate for angular asymmetry caused by substrate precession while maintaining ease of operation through automated control.
Solution Approach 2:
The system uses feedback from the substrate's orientation (measured via encoders or sensors) to adjust the pressure distribution across zones. The control algorithm continuously monitors the substrate position and modifies zone pressures to maintain angular symmetry in the polishing profile, thereby achieving precise thickness control despite substrate rotation.
3Productivity
If higher pressure is applied to increase material removal rate, then polishing productivity increases, but variations in material removal rate across the substrate increase
Solution Approach 1:
The carrier head is divided into multiple independently controllable zones that can apply different pressures to different regions of the substrate. This segmentation allows the system to apply higher overall pressure to increase productivity while maintaining uniform material removal across the substrate, as each zone's pressure can be optimized for its specific region and the substrate's orientation at that position.
Data Source
AI summary
Generating a recipe for controlling a polishing system includes receiving a target removal profile that includes a target thickness to remove for a plurality of locations on a substrate that are angularly distributed around the substrate, and storing a first function defining a polishing rate for a zone from a plurality of pressurizable zones of a carrier head that are angularly distributed around a the carrier head. The first function defines polishing rates as a function of pressures. For each particular zone of the plurality of zones a recipe defining a pressure for the particular zone over time is calculated by calculating an expected thickness profile after polishing using the first function, and minimizing a cost function that incorporates a first term representing a difference between the expected thickness profile and a target thickness profile.