CMP Retainer Ring Segmentation for Wafer Edge Pressure
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Solution Overview
Problem
Conventional polishing apparatuses experience a decrease in depressing force at the periphery of the wafer during the CMP process, leading to non-uniform surfaces and reduced polishing rates due to membrane sheet deformation, which affects the yield of semiconductor device manufacturing.
Innovation Solution
The polishing apparatus incorporates a retainer ring with a first member of larger inner diameter and thickness, and a second member of equal thickness to the wafer, along with a membrane sheet that depresses the wafer and the second member onto the polishing pad, using edge-depressing members to apply uniform pressure and prevent membrane sheet contact with the wafer periphery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the membrane sheet periphery is aligned with the wafer periphery, then the structure is compact and simple, but the membrane sheet deforms and bulges downward during polishing, causing pressure decrease at the wafer periphery
Solution Approach 1:
The retainer ring is divided into two separate members: a first member (ring-shaped) that provides structural support, and a second member (plate-shaped) that directly contacts the wafer periphery. This segmentation allows each component to perform its specific function independently, preventing membrane deformation while maintaining structural integrity.
Solution Approach 2:
The second member of the retainer ring acts as an intermediary between the first member and the wafer periphery. It transfers the depressing force from the membrane sheet to the wafer edge, ensuring uniform pressure distribution and preventing the membrane sheet from directly contacting and deforming around the wafer.
2Force
If high-pressure air is supplied into the closed space to depress the wafer, then the wafer is held firmly against the polishing pad, but the membrane sheet deforms and the periphery is raised, reducing depressing force
Solution Approach 1:
The second member of the retainer ring is positioned to contact the wafer periphery before the membrane sheet can deform and rise. This preliminary positioning prevents the membrane sheet from bulging upward, maintaining its flat configuration and ensuring consistent depressing force across the entire wafer surface during polishing.
3Device complexity
If the membrane sheet has the same diameter as the wafer, then the structure is compact, but the periphery of the membrane sheet is raised during polishing, causing non-uniform surface
Solution Approach 1:
The retainer ring is segmented into two functional members that work together to maintain membrane sheet flatness. The first member provides the ring structure, while the second member (plate-shaped) with dimensions matching the wafer prevents membrane rise at the periphery, ensuring uniform polishing across the entire surface.
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 configuration maintains consistent polishing pressure across the wafer surface, enhancing polishing rate and uniformity, reducing surface variation to ±5% compared to ±10% with conventional methods.
Implementation Method 1
High-pressure air is supplied into the closed space 18, whereby the wafer 12 is depressed toward the polishing pad 11
Implementation Method 2
the membrane sheet depresses the wafer and the second member toward the polishing pad
Implementation Method 3
The CMP process is employed to impart such a flat surface to the each film
Data Source
AI summary
A polishing apparatus includes a polishing pad for polishing a wafer and a polishing head for holding the wafer. The polishing head includes a retainer ring, a membrane sheet, and a head body. The retainer ring retains the wafer in a horizontal direction. The membrane sheet depresses the wafer to the polishing pad. The head body supports the retainer ring and the membrane sheet. The retainer ring includes a fixed retainer ring and a released retainer ring. The released retainer ring is interposed between the inner periphery of the fixed retainer ring and the periphery of the wafer to retain the wafer in the horizontal direction.