CMP Carrier Head Membrane Zoning for Wafers With Flats
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Solution Overview
Problem
Existing CMP systems face challenges in achieving uniform planarization of wafers with flats or voids, leading to non-uniform removal rates and increased waste due to phenomena like 'Burning the Flat', which affects yield and increases manufacturing costs.
Innovation Solution
A substrate carrier head with a membrane having a primary and secondary zone, where the secondary zone is isolated from pressure applied to the primary zone, and a membrane support plate provides mechanical support to prevent membrane inflation into voids, ensuring continuous contact and independent pressure control across sub-zones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If pressure is applied uniformly across the entire membrane to achieve continuous contact with the wafer, then contact uniformity is improved, but non-uniform removal rates occur at flat areas causing 'Burning the Flat' phenomenon
Solution Approach 1:
The membrane is divided into two independent pressure zones: a first pressure zone that applies pressure to the central polishing area, and a second pressure zone that applies reduced or zero pressure to the peripheral flat area. This segmentation prevents the membrane from contacting the flat area excessively while maintaining contact over the polishing area, thereby eliminating the 'Burning the Flat' phenomenon while achieving uniform planarization.
2Stability of the object's composition
If the membrane is allowed to contact the flat area to ensure continuous contact, then contact continuity is improved, but removal rate non-uniformity increases due to void formation
Solution Approach 1:
Different regions of the membrane are assigned different pressure characteristics: the central region maintains pressure for continuous contact and effective polishing, while the peripheral region corresponding to the flat area has reduced or zero pressure to prevent void formation and excessive contact. This local differentiation ensures contact continuity where needed while preventing removal rate non-uniformity at flat areas.
3Object-affected harmful factors
If independent pressure control zones are implemented to prevent Burning the Flat, then harmful effects are reduced, but device complexity increases
Solution Approach 1:
The membrane is segmented into distinct pressure zones with independent control, allowing the system to apply different pressures to different regions. This segmentation enables prevention of wafer breakage and Burning the Flat through localized pressure control, while the modular zone design keeps the complexity manageable by focusing control efforts on specific critical areas rather than requiring complex global control.
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 design reduces non-uniformity in planarization, minimizes wafer breakage, and enhances yield by preventing high removal rates at flat areas, thus optimizing the CMP process and reducing manufacturing costs.
Implementation Method 1
a membrane cavity formed along the second surface and configured to apply pressure to the membrane within the primary zone
Implementation Method 2
a membrane support plate configured to support the secondary zone of the membrane
Data Source
AI summary
Carriers for polishing workpieces with flats or voids are provided. In one aspect, a substrate carrier head for a chemical mechanical planarization (CMP) system include a carrier body comprising an aperture configured to receive a wafer and a membrane having a first surface configured to contact a surface of the wafer and a second surface opposing the first surface, the membrane having a primary zone and a secondary zone. The substrate carrier head further includes a membrane cavity formed along the second surface and configured to apply pressure to the membrane within the primary zone, and a membrane support plate configured to support the secondary zone of the membrane.