CMP Carrier Head Membrane Roughness Zoning for Uniform Polishing
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Solution Overview
Problem
Chemical mechanical polishing (CMP) often results in non-uniform polishing across substrate surfaces, leading to underpolishing at edge portions, which requires additional load adjustments and redesigns of carrier heads to achieve uniformity.
Innovation Solution
A flexible membrane with a central portion having a surface roughness greater than 15 microinches and an edge portion with a surface roughness less than 5 microinches is used in the carrier head, allowing differential polishing rates across the substrate without modifying the carrier head, utilizing chloroprene, silicon, or ethylene propylene diene M-class rubber materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a uniform surface roughness membrane is used, then the carrier head structure is simple, but non-uniform polishing occurs with underpolishing at edge portions
Solution Approach 1:
The membrane surface is divided into distinct regions with different roughness characteristics: a central portion with high roughness (greater than 15 microinches) and an edge portion with low roughness (less than 5 microinches). This local differentiation allows the central area to provide high polishing rate while the edge portion prevents substrate sticking, thereby achieving uniform polishing across the entire substrate without requiring complex carrier head modifications
2Productivity
If higher load is applied to prevent underpolishing at edges, then polishing rate increases, but substrate sticking during dechuck occurs
Solution Approach 1:
The edge portion of the membrane is engineered with low surface roughness (less than 5 microinches) which reduces adhesion between the membrane and substrate. This allows the carrier head to apply higher loading forces to prevent underpolishing at edges without causing the substrate to stick during dechuck operations, thus maintaining both high productivity and ease of operation
3Manufacturing precision
If carrier head is modified to achieve uniform polishing, then polishing uniformity improves, but device complexity and manufacturing cost increase
Solution Approach 1:
Instead of modifying the carrier head structure, the invention applies different surface roughness treatments to different portions of the membrane itself. The central portion is treated to have high roughness (greater than 15 microinches) for high polishing rate, while the edge portion is treated to have low roughness (less than 5 microinches) to prevent sticking. This approach achieves uniform polishing without requiring complex carrier head redesign or additional components
Solution Approach 2:
The invention changes the surface roughness parameter of the membrane across different regions to achieve the desired polishing behavior. By controlling the surface roughness to vary from the central portion to the edge portion, the system achieves uniform polishing rates without modifying the carrier head structure, thereby simplifying manufacturing while improving polishing uniformity
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
The membrane 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, thus enhancing CMP efficiency.
Implementation Method 1
Pressurization or evacuation of a chamber behind the flexible membrane controls the load on the substrate
Implementation Method 2
Pressurization or evacuation of a chamber behind the flexible membrane controls the load on the substrate
Implementation Method 3
Chemical mechanical polishing (CMP) is one accepted method of planarization
Implementation Method 4
The exposed surface of the substrate is placed against a polishing pad, such as circular pad or linear belt, that moves relative to the substrate
Implementation Method 5
A polishing liquid, such as a slurry with abrasive particles, is supplied to the surface of the polishing pad
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.