CMP Polishing Pad Composition for Stable Removal and Low Defects

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Solution Overview

Problem

In semiconductor manufacturing, existing polishing pads for CMP processes face challenges in maintaining long-term polishing performance and achieving optimal removal rates while minimizing defects, due to variations in physical properties such as hardness and elongation.

Innovation Solution

A polishing pad with a specific nuclear magnetic resonance (NMR) 13C spectrum profile and molecular weight distribution, comprising a urethane-based prepolymer with controlled isocyanate and polyol content, is developed. This pad has a softening control index between 0.10 and 0.45, tensile strength of 20 to 25 N/mm², and elongation of 90 to 130%, ensuring consistent performance over time.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional polishing pads are used for CMP processes, then initial polishing performance may be achieved, but long-term polishing performance deteriorates due to variations in physical properties such as hardness and elongation

Engineering Contradiction:

Improvelong-term polishing performanceVSAvoidphysical properties (hardness and elongation)

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent applies parameter changes by precisely controlling the molecular weight distribution (Mw/Mn ratio between 1.05-2.0) and chemical composition (isocyanate index 80-120) of the polyurethane polishing pad. These parameter controls ensure that the polishing pad maintains stable physical properties including hardness (40-70 Shore A) and elongation (80-150%) throughout its service life, preventing performance deterioration while achieving reliable long-term polishing results

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses composite materials by formulating a polyurethane polishing pad with specific combinations of polyol, isocyanate, and various additives including silane-modified polymers and inorganic fillers. This composite structure creates a material that simultaneously achieves the desired mechanical properties (tensile strength 1.5-3.0 MPa, elongation 80-150%) and polishing performance, maintaining stability over time through the synergistic effects of the composite composition

Inventive Principle:

Principle #40Composite materials

2Productivity

If polishing pad hardness is increased to achieve higher removal rate, then polishing efficiency improves, but defect prevention capability deteriorates

Engineering Contradiction:

Improveremoval rateVSAvoidpolishing defects

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent applies parameter changes by optimizing the hardness of the polishing pad to a specific range (40-70 Shore A) rather than using extreme hardness values. This controlled parameter adjustment enables the pad to achieve sufficient removal rate (200-500 nm/min for silicon dioxide) while maintaining the compliance needed to prevent polishing defects such as scratches and dishing, thus resolving the contradiction between productivity and defect prevention

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent applies local quality by creating a polishing pad with non-uniform density distribution, where the surface layer has different properties than the bulk material. The surface layer is formulated with specific hardness and porosity to optimize contact with the wafer surface, providing both cutting action for removal rate and cushioning effect for defect prevention, while the bulk material provides structural support

Inventive Principle:

Principle #3Local quality

3Manufacturing precision

If polishing pad elongation is increased to improve conformability to substrate surface, then polishing uniformity improves, but mechanical strength deteriorates

Engineering Contradiction:

Improvepolishing uniformityVSAvoidtensile strength

Core Design Contradiction:

Manufacturing precisionVSStrength

Solution Approach 1:

The patent applies parameter changes by precisely controlling the elongation of the polishing pad within the range of 80-150% through adjustment of the polyurethane formulation, including the isocyanate index (80-120) and molecular weight ratio (Mw/Mn: 1.05-2.0). This optimized parameter range provides sufficient conformability to match wafer surface topography and achieve uniform polishing, while maintaining adequate tensile strength (1.5-3.0 MPa) for mechanical durability during handling and operation

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS12258460B2Polishing pad and method of fabricating semiconductor device using the same

Publication Date: 2025.03.25 SK ENPULSE CO LTD

AI summary

Provided is a polishing pad including a polishing layer, wherein the nuclear magnetic resonance (NMR) 13C spectrum of a processed composition prepared by adding 1 g of the polishing layer to a 0.3 M aqueous solution of potassium hydroxide (KOH) and allowing the mixture to react in a closed container at a temperature of 150° C. for 48 hours includes a first peak appearing at 15 ppm to 18 ppm, a second peak appearing at 9 ppm to 11 ppm, a third peak appearing at 138 ppm to 143 ppm, and a fourth peak appearing at 55 ppm to 65 ppm, and the softening control index calculated by Equation 1 is 0.10 to 0.45. The polishing pad includes the polishing layer having physical properties corresponding to the softening control index, and thus may exhibit a removal rate and defect prevention performance within desired ranges in polishing of a polishing target.