Edge Load Ring Venting for CMP Pressure Equalization
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Solution Overview
Problem
Chemical mechanical polishing (CMP) processes face persistent issues with edge effects, resulting in over- or under-polishing of the outermost 5-10 mm of substrates, which affects the precision and uniformity of semiconductor device manufacturing.
Innovation Solution
An edge load ring (ELR) is designed to fit inside a retaining ring of a CMP head, featuring an annular body with a venting feature that equalizes pressure between the inner and outer surfaces, preventing undesirable sticking and improving force distribution across the substrate, thereby enhancing polishing precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If pressure is applied to control force distribution in CMP polishing, then polishing uniformity is improved, but edge effects (over- or under-polishing) occur at the substrate perimeter
Solution Approach 1:
The ELR is designed with different radial zones (first radial zone with first downforce, second radial zone with second downforce) to apply different pressures to different regions of the substrate. This local differentiation of pressure allows the perimeter regions to receive adjusted force compared to the center, compensating for edge effects while maintaining overall polishing uniformity.
2Manufacturing precision
If the ELR applies downforce to the substrate perimeter, then edge polishing control is improved, but the ELR may stick to the substrate causing operational issues
Solution Approach 1:
The ELR incorporates an oscillation mechanism that dynamically adjusts the contact between the ELR and substrate. The ELR oscillates between contacting and not contacting the substrate, preventing sticking while maintaining controlled downforce application to the substrate perimeter during polishing operations.
Solution Approach 2:
The ELR employs periodic oscillation to cycle between contact and non-contact states with the substrate. This periodic action prevents continuous adhesion (sticking) while ensuring that during contact phases, the ELR applies the necessary downforce for edge polishing control.
3Ease of manufacture
If the ELR structure is simplified for ease of manufacture, then manufacturing cost is reduced, but pressure equalization between inner and outer surfaces becomes difficult
Solution Approach 1:
The ELR design extracts and separates the pressure equalization function into a distinct venting feature. This venting feature provides fluid communication between the inner and outer surfaces of the ELR, allowing pressure equalization without complicating the overall ELR structure. The venting feature can be a simple hole or passage integrated into the ELR body.
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 ELR effectively prevents edge effects by equilibrating pressure and improving force distribution, leading to more uniform polishing and reduced substrate damage, thus enhancing the manufacturing process for semiconductor devices.
Implementation Method 1
The annular body includes a venting feature formed through the annular body, the venting feature being in fluid communication between the inner and outer surfaces
Data Source
AI summary
Apparatus and methods relating to chemical mechanical polishing (CMP) are described herein. An edge load ring (ELR) is configured to fit inside a retaining ring of a CMP head. The ELR includes an annular body having an inner surface and an outer surface opposite the inner surface, the outer surface having a diameter configured to slip inside a retaining ring. The annular body includes a body portion formed from a first material and a bottom projection extending below the body portion. The bottom projection has a bottom surface facing away from the body portion, and the bottom projection is formed form a second material different from the first material. The annular body includes a venting feature formed through the annular body, the venting feature being in fluid communication between the inner and outer surfaces.