CMP Carrier Head Membrane Roughness Zoning for Edge Uniformity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Chemical mechanical polishing (CMP) often results in non-uniform polishing rates across substrate surfaces, leading to underpolishing at edge portions, which can be addressed by applying additional load but requires redesign of the carrier head.
Innovation Solution
A flexible membrane with a central portion of higher surface roughness (>15 microinches) and an edge portion of lower surface roughness (<5 microinches) is used with a carrier head, allowing differential polishing rates without modifying the carrier head, utilizing materials like chloroprene or ethylene propylene diene M-class rubber, and featuring spherical bumps in the central portion and negligible features in the edge portion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a uniform roughness membrane is used, then the manufacturing is simple, but the polishing uniformity deteriorates with edge underpolishing
Solution Approach 1:
The membrane surface is divided into distinct zones with different roughness characteristics: a central region with higher roughness (5-20 microinches) and an edge region with lower roughness (1-5 microinches). This local differentiation allows the membrane to provide appropriate friction and polishing pressure distribution, preventing edge underpolishing while maintaining manufacturing feasibility through segmented surface treatment processes.
2Manufacturing precision
If additional load is applied to the edge to improve polishing uniformity, then the polishing uniformity improves, but the device complexity increases requiring carrier head redesign
Solution Approach 1:
Instead of modifying the mechanical structure of the carrier head to apply differential load, the invention changes the surface roughness parameter of the membrane material itself. By controlling the roughness distribution across the membrane surface, the friction characteristics are modified to achieve uniform polishing pressure distribution without requiring complex carrier head redesign or additional loading mechanisms.
3Ease of operation
If the membrane surface is made smooth, then the substrate release is easy, but the polishing rate decreases
Solution Approach 1:
The membrane employs spatially varying surface properties: the central region maintains higher roughness (5-20 microinches) to ensure adequate polishing rate and prevent substrate adhesion during polishing, while the edge region has lower roughness (1-5 microinches) that facilitates easier substrate release after polishing without significantly compromising overall polishing efficiency.
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 ensures uniform polishing across the substrate by varying the polishing rate based on surface roughness, preventing underpolishing at edges and facilitating easy substrate release without breaking, while maintaining the integrity of the carrier head design.
Implementation Method 1
The outer surface has a central portion and an edge portion surrounding the central portion. The central portion has a first surface roughness and the edge portion has a second surface roughness, the first surface roughness being greater than the second surface roughness.
Data Source
AI summary
An apparatus comprises a flexible membrane for use with a carrier head of a substrate chemical mechanical polishing apparatus. The membrane comprises an outer surface providing a substrate receiving surface, wherein the outer surface has a central portion and an edge portion surrounding the central portion, wherein the central portion has a first surface roughness and the edge portion has a second surface roughness, the first surface roughness being greater than the second surface roughness.