Dual Membrane Carrier Head for CMP Uniformity
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Solution Overview
Problem
Existing chemical mechanical polishing (CMP) technologies face challenges in achieving uniformity in substrate polishing due to variations in slurry distribution and substrate non-uniformity, which current substantially uniform pressure methods cannot effectively address.
Innovation Solution
A dual membrane carrier head system is introduced, featuring a base assembly and a membrane assembly with an inner and outer membrane. The inner membrane has multiple individually pressurizable chambers, while the outer membrane applies pressure to the substrate. This setup allows for differential pressure application to various substrate regions, enhancing polishing uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If substantially uniform pressure is applied across the substrate during CMP, then the simplicity of the polishing process is maintained, but polishing uniformity deteriorates due to variations in slurry distribution and substrate non-uniformity
Solution Approach 1:
The carrier head is divided into multiple independently pressurizable zones (first zone, second zone, third zone) with separate pressure control systems. This segmentation allows differential pressure application to different substrate regions, compensating for slurry distribution variations and substrate non-uniformity to achieve improved polishing uniformity across the wafer surface.
Solution Approach 2:
Different pressure levels are applied to different zones of the carrier head based on local requirements. The first zone receives a first pressure, the second zone receives a second pressure, and the third zone receives a third pressure, allowing each region to be optimized for its specific polishing needs rather than applying uniform pressure across the entire substrate.
2Device complexity
If a single membrane structure is used in the carrier head, then the device complexity is reduced, but the ability to apply differential pressure to various substrate regions is limited
Solution Approach 1:
The single membrane structure is replaced with multiple separate membranes (first membrane, second membrane, third membrane), each defining a distinct pressurizable zone. This allows independent pressure control for each zone while maintaining manageable device complexity through modular design.
Solution Approach 2:
Multiple membranes act as intermediaries between the pressure control system and the substrate, enabling differential pressure application. Each membrane transmits pressure independently to its designated zone, providing the adaptability needed for non-uniform polishing compensation.
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 dual membrane carrier head system effectively reduces variations in substrate profile, improves within-wafer uniformity, and extends the lifespan of the inner membrane by reducing wear, thereby lowering maintenance and operational costs.
Implementation Method 1
pressurizing the inner chambers and the lower chamber such that one or more of the individually pressurizable inner chambers of the inner membrane are pressurized to a pressure equal to or greater than the pressure of the lower chamber to supplement the pressure applied by the outer membrane to the substrate
Implementation Method 2
The inner membrane forms a plurality of individually pressurizable inner chambers between an upper surface of the membrane and the membrane support. The outer membrane defines a lower pressurizable chamber between the inner surface of the outer membrane and a lower surface of the inner membrane.
Data Source
AI summary
A carrier head for chemical mechanical polishing includes a base assembly and a membrane assembly connected to the base assembly. The membrane assembly includes a membrane support, an inner membrane secured to the membrane support, wherein the inner membrane forms a plurality of individually pressurizable inner chambers between an upper surface of the membrane and the membrane support, and an outer membrane secured to the membrane support and extending below the inner membrane, the outer membrane having an inner surface and an outer surface, wherein the outer membrane defines a lower pressurizable chamber between the inner surface of the outer membrane and a lower surface of the inner membrane, wherein the inner surface is positioned for contact by a lower surface of the inner membrane upon pressurization of one or more of the plurality of chambers, and wherein the outer surface is configured to contact a substrate.