CMP Pressure Zoning for Precession Thickness Uniformity
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Solution Overview
Problem
Chemical mechanical polishing (CMP) processes face challenges in achieving consistent material removal rates due to variations in substrate thickness, slurry composition, polishing pad condition, relative speed, and load, leading to angular asymmetry in polished substrates.
Innovation Solution
A method is developed to generate a polishing recipe by receiving a target removal profile, storing functions for substrate orientation and polishing rate, and calculating pressure profiles for each zone of the carrier head over time, using an algorithm that minimizes the difference between the expected and target thickness profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional CMP process is used with constant pressure, then the polishing process is simple to operate, but angular asymmetry occurs in the polished substrate due to substrate precession and variations in polishing parameters
Solution Approach 1:
The carrier head is divided into multiple independently controllable pressurizable zones arranged angularly around the substrate. Each zone can apply different pressure to compensate for angular asymmetry caused by substrate precession, allowing localized pressure adjustment to achieve uniform thickness profile across the substrate surface.
Solution Approach 2:
The system dynamically adjusts pressure in each zone based on real-time substrate orientation and precession characteristics. The pressure profile varies over time to counteract the changing asymmetry patterns, transforming the static pressure application into a dynamic compensation mechanism that maintains manufacturing precision.
2Productivity
If pressure is increased to accelerate material removal, then productivity improves, but variations in material removal rate across the substrate increase due to asymmetry
Solution Approach 1:
Different pressure levels are applied to different angular zones of the substrate based on their specific removal rate requirements. Zones experiencing higher removal rates receive lower pressure, while zones with lower removal rates receive higher pressure, achieving uniform thickness profile across the entire substrate while maintaining high overall productivity.
3Ease of operation
If substrate precession is allowed to occur naturally, then the polishing process is easier to implement, but angular asymmetry in the polished surface increases
Solution Approach 1:
The system intentionally introduces asymmetric pressure distribution across the substrate to counteract the asymmetric effects of precession. By applying higher pressure to specific angular zones at specific times, the system compensates for the natural asymmetry caused by substrate precession, maintaining manufacturing precision without restricting the ease of operation.
Data Source
AI summary
Generating a recipe for a polishing process includes receiving a target removal profile that includes a target thickness to remove for a plurality of locations spaced angularly around a center of a substrate, storing a first function providing substrate orientation relative to the carrier head over time, storing a second function defining a polishing rate below a zone of the zone as a function of one or more pressures of one or more zones from a plurality of pressurizable zones of the carrier head that are spaced angularly around the center of the substrate, and for each particular zone of the plurality of zones, calculating a recipe defining a pressure for the particular zone over time. Calculating the recipe includes calculating an expected thickness profile after polishing from the second function defining the polishing rate and the first function providing substrate orientation relative to the zone over time, and applying a minimizing algorithm to reduce a difference between the expected thickness profile and the target thickness profile.