CMP Pad Asperity Angles for Planarity and Uniformity
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Solution Overview
Problem
Conventional chemical mechanical planarization (CMP) pads face issues with glazing and clogging, leading to non-uniform polishing and reduced planarity due to the wear and debris accumulation, requiring frequent conditioning which can result in irregular removal rates and within-wafer and wafer-to-wafer non-uniformity.
Innovation Solution
The development of CMP pads with asperities extending from the major surface, oriented at specific angles and configurations to facilitate shearing and rubbing actions, which reduce the need for particulate matter in the polishing fluid and enhance material removal while maintaining uniformity and planarity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional CMP pads are used with porous structure and random asperities, then material removal is achieved through chemical and mechanical action, but the pad surface glazes and clogs over time leading to non-uniform polishing and reduced planarity
Solution Approach 1:
The pad surface is segmented into distinct functional zones: a polishing layer with controlled porosity and asperities for material removal, and a conditioning layer with different properties for surface renewal. This segmentation allows independent optimization of polishing performance and surface maintenance, preventing the glazing and clogging that occur in conventional uniform pad structures
Solution Approach 2:
Different regions of the pad are赋予 different local properties: the polishing layer contains asperities with specific height distributions and pore structures optimized for material removal, while the conditioning layer has tailored characteristics for surface renewal. This local quality differentiation enables the pad to maintain planarity by addressing specific surface defects in specific regions without compromising overall polishing uniformity
2Reliability
If polishing pads are conditioned frequently to maintain surface quality, then glazing and clogging are reduced, but irregular removal rates and within-wafer non-uniformity increase
Solution Approach 1:
The pad structure enables continuous effective polishing action without interruption for conditioning. The controlled porosity (30-70%) and asperity distribution maintain consistent material removal rates throughout pad life, eliminating the periodic disruptions caused by conditioning cycles. This continuity ensures uniform wafer processing while maintaining surface quality through the inherent structural design rather than intermittent intervention
3Productivity
If conventional polishing pads with random asperities are used, then material removal is achieved, but the pad requires periodic conditioning which reduces durability and increases process complexity
Solution Approach 1:
The pad structure is designed to self-maintain its polishing characteristics throughout its service life. The controlled porosity and asperity configuration in the polishing layer, combined with the conditioning layer, enable the pad to resist glazing and clogging without external intervention. This self-service capability extends pad durability while maintaining consistent polishing performance, eliminating the need for periodic conditioning operations
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 pads achieve improved surface planarity, reduced within-wafer and wafer-to-wafer non-uniformity, and extended durability by utilizing asperities with tailored angles and configurations that optimize contact and material removal, minimizing the need for frequent conditioning.
Implementation Method 1
the asperities of the pad are oriented and shaped to planarize a surface of a wafer by a shearing action with which the pad is brought into contact
Implementation Method 2
Others of the one or more asperities of the pad may be oriented, shaped, and configured to polish (e.g., rub) one or more surfaces of the wafer in a polishing action
Data Source
AI summary
A pad for chemical mechanical planarization comprises a material having a major surface, and asperities extending from the major surface, a ratio between a length and a width of each of the asperities greater than about 2:1, and an included angle between a leading surface of at least some asperities and the major surface greater than about 90°. Related pads, tools for chemical mechanical planarization, and related methods are also disclosed.