Offset Pore Poromeric Polishing Pad for Low Defectivity
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Solution Overview
Problem
Current poromeric polishing pads, such as Politex and Optivision, face challenges in achieving low defectivity and high TEOS:Cu selectivity ratio, especially in advanced copper-barrier polishing applications, where they often result in excessive foam and potential poisoning of dielectric materials.
Innovation Solution
A porous polyurethane polishing pad with a unique structure featuring large interconnected pores, middle-sized columnar pores, and small pores, which increases the pad's compressibility and contact area, thereby enhancing polishing performance and reducing defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional poromeric polishing pads (Politex, Optivision) are used, then polishing operation can be performed, but defectivity is not sufficiently low and TEOS:Cu selectivity ratio is not high enough
Solution Approach 1:
The patent employs a poromeric polishing pad with a controlled porous structure containing interconnected pores of varying sizes (large, medium, and small pores). This porous architecture enhances slurry penetration and chemical mechanical action while maintaining low defectivity. The pore distribution and connectivity are specifically engineered to improve TEOS removal rate without compromising defectivity, resolving the contradiction between manufacturing precision and productivity.
Solution Approach 2:
The polishing pad utilizes a composite poromeric structure combining polyurethane matrix with controlled pore formations. The composite nature of the material, integrating different pore sizes and densities within the same pad structure, enables simultaneous achievement of low defectivity and high TEOS:Cu selectivity ratio, addressing the technical contradiction between precision and productivity.
2Manufacturing precision
If poromeric polishing pads are used to achieve low defectivity, then wafer yield increases, but excessive foam is produced and dielectric materials may be poisoned
Solution Approach 1:
The patent modifies the chemical and physical parameters of the poromeric polishing pad, including pore size distribution, pore connectivity, and material composition. These parameter changes optimize the pad's interaction with polishing slurries, reducing excessive foam generation and preventing dielectric poisoning while maintaining low defectivity. The controlled pore structure regulates slurry flow and chemical reactions at the pad-wafer interface.
3Area of stationary object
If polishing pad compressibility is increased for better conformance, then contact area increases, but pad structure complexity increases
Solution Approach 1:
The patent utilizes a porous poromeric structure with interconnected pores of varying sizes that naturally provide compressibility and conformance to the wafer surface. The porous architecture allows the pad to deform and adapt to surface irregularities, increasing contact area without requiring complex external structures. The inherent porosity of the material provides the necessary mechanical compliance.
Solution Approach 2:
The polishing pad features a nested pore structure with large, medium, and small pores interconnected within the same matrix. This nested arrangement of pores at different scales provides multi-level compliance and conformance capabilities, enabling the pad to adapt to various surface topographies while maintaining a relatively simple overall structure.
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 innovative polishing pad design achieves ultra-low defectivity and stable removal rates for copper and TEOS, improving wafer yield and extending pad life, while maintaining high compressibility for effective conformance and polishing.
Implementation Method 1
the large pores having horizontal offset upper and lower sections, middle-sized pores and small pores combine for increasing compressibility of the polishing pad and contact area of the top polishing surface during polishing
Data Source
AI summary
The invention provides a porous polyurethane polishing pad that includes a porous matrix having large pores that extend upward from a base surface and open to an upper surface. The large pores extend to the top polishing surface and have lower and upper sections with a vertical orientation. The lower and upper sections are offset in a horizontal direction. Middle-sized pores with a columnar shape and a vertical orientation originate adjacent the middle sections and small pores with a columnar shape and a vertical orientation originate between the middle-sized pores. The pores combine for increasing compressibility of the polishing pad and contact area of the top polishing surface during polishing.