CMP Support Plate Aperture Segmentation for Wafer Uniformity
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Solution Overview
Problem
Chemical mechanical polishing (CMP) processes face challenges in achieving uniform wafer thickness due to uneven pressure distribution, leading to edge humps and non-uniform polishing results, as central apertures do not adequately support membrane pressure radially, resulting in thicker outer edges compared to central regions.
Innovation Solution
The use of a support plate with apertures arranged in a circumferential edge region, allowing for more even pressure distribution across the wafer, combined with a retaining ring design that applies pressure differentially to combat edge humps, ensures uniform contact and planarization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If apertures are arranged centrally on the support plate, then pressure is applied to the central region of the wafer, but pressure distribution becomes uneven causing edge humps and non-uniform polishing
Solution Approach 1:
The single central aperture is segmented into multiple apertures arranged in a circumferential pattern around the periphery of the support plate. This segmentation distributes the pressure application points from a single central location to multiple locations around the edge, enabling more uniform radial pressure distribution across the wafer surface and eliminating edge humps caused by concentrated central pressure.
Solution Approach 2:
The aperture arrangement transitions from a one-dimensional central point to a two-dimensional circumferential distribution pattern. By arranging apertures along a circular path at the periphery of the support plate, the pressure application is distributed across multiple spatial dimensions, creating uniform radial pressure fields that improve wafer thickness uniformity during polishing.
2Manufacturing precision
If a retaining ring is used to apply pressure to the wafer edge, then edge humps can be combated, but the structure becomes more complex
Solution Approach 1:
The retaining ring structure is merged with the support plate to form an integrated assembly. The retaining ring is attached to the periphery of the support plate, combining the functions of structural support, pressure application, and wafer retention into a single unified component, thereby reducing overall device complexity while maintaining effective edge hump control.
Solution Approach 2:
The retaining ring serves multiple functions simultaneously: it provides structural support for the aperture arrangement, applies differential pressure to the wafer edge to combat humps, and retains the wafer during polishing. This multi-functionality reduces the need for separate components, simplifying the overall polishing head structure.
Data Source
AI summary
To provide improved planarization, techniques in accordance with this disclosure include a CMP station that includes a support plate having a plurality of apertures. An aperture of the plurality of apertures has a first opening and a second opening connected by a slot. Other systems and methods are also disclosed.