Offset Circumferential Grooves in CMP Pads
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Solution Overview
Problem
Current chemical mechanical polishing (CMP) pads face challenges in achieving uniformity and minimizing pattern transfer to semiconductor wafers, leading to defects and uneven polishing, particularly due to the transfer of groove patterns from the polishing pad to the wafer surface.
Innovation Solution
The development of CMP polishing pads with a polishing layer featuring a geometric center and a plurality of offset circumferential grooves, where each groove has its own distinct geometric center, and an outermost groove that is concentric with the polishing layer, reducing pattern transfer and enhancing polishing uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If concentric circular grooves are used on the polishing pad, then slurry transport is facilitated, but pattern transfer occurs from the polishing pad to the wafer surface
Solution Approach 1:
The patent applies asymmetry by offsetting the circumferential grooves from the center of the polishing pad. Instead of concentric grooves centered at the pad's geometric center, the grooves are positioned with their center offset from the pad center, creating an asymmetric groove pattern that disrupts the transfer of circular patterns to the wafer surface while maintaining effective slurry transport channels
2Manufacturing precision
If carrier oscillation is introduced to minimize pattern transfer, then polishing uniformity improves, but polishing temperature increases
Solution Approach 1:
The patent applies preliminary action by pre-configuring the groove pattern on the polishing pad to minimize pattern transfer before polishing begins. The offset circumferential groove design is built into the pad structure in advance, eliminating the need for dynamic carrier oscillation during polishing, thereby achieving polishing uniformity without the temperature penalty of oscillation
3Manufacturing precision
If circumferential grooves are offset from the center, then pattern transfer is reduced, but groove configuration complexity increases
Solution Approach 1:
The patent applies local quality by creating zones of different groove characteristics - the offset circumferential grooves are positioned at specific locations and orientations to address pattern transfer in critical areas, while maintaining a systematic overall pattern that is manufacturable. The groove depth, width, and spacing can vary locally to optimize performance without requiring completely complex random patterns
Data Source
AI summary
The present invention provides a chemical mechanical (CMP) polishing pad for planarizing at least one of semiconductor, optical and magnetic substrates comprising a polishing layer that has a geometric center, and in the polishing layer a plurality of offset circumferential grooves, such as circular or polygonal grooves, which have a plurality of geometric centers and not a common geometric center. In the polishing layer of the present invention, each circumferential groove is set apart a pitch distance from its nearest or adjacent circumferential groove or grooves; for example, the pitch increases on the half or hemisphere of the polishing layer that is farthest from the geometric center of its innermost circumferential groove and decreases on the half of the polishing layer nearest that geometric center. Preferably, the polishing layer contains an outermost circumferential groove that is complete and continuous.