Polyurethane CMP Pad for Uniformity and Dishing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional chemical mechanical polishing (CMP) pads face challenges such as short pad life, dishing of metal features, oxide erosion, and increased surface scratches due to their softness, which compromises planarity and uniformity in semiconductor wafer processing.
Innovation Solution
A polyurethane CMP pad formulation derived from a polyether/polyester prepolymer reaction mixture with specific weight percentages, incorporating surfactants, curatives, and foaming agents, achieving high damping performance, moderate hardness, and high porosity to enhance energy dissipation and stiffness, thereby reducing dishing and improving uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If soft CMP pads are used, then low defect density and good within-wafer uniformity are achieved, but pad life is short and dishing increases
Solution Approach 1:
The patent uses a composite polymeric material combining polyether and polyester segments in a specific ratio (60-80 wt% polyether, 20-40 wt% polyester). This composite structure integrates the softness and low defect density of polyether with the stiffness and durability of polyester, resolving the contradiction between uniformity and pad life
Solution Approach 2:
The patent modifies the chemical composition parameters of the polymeric material by controlling the weight percentages of polyether and polyester segments. This parameter adjustment optimizes the balance between softness (for uniformity) and stiffness (for pad life and dishing reduction)
2Manufacturing precision
If soft CMP pads are used, then low defect density is achieved, but dishing of metal features increases
Solution Approach 1:
The composite polymeric material with polyether/polyester segments creates a structure that maintains softness for low defect density while incorporating stiffness elements that resist dishing during the polishing process
Solution Approach 2:
By adjusting the polyether to polyester ratio and controlling the density (0.6-0.95 g/cc), the patent optimizes the material properties to simultaneously achieve low defect density and minimize dishing
3Shape
If stiff CMP pads are used, then dishing is reduced, but surface scratches and defects increase
Solution Approach 1:
The composite structure combines stiff polyester segments (for dishing reduction) with soft polyether segments (for scratch reduction), creating a balanced material that prevents both dishing and surface defects
Solution Approach 2:
The patent controls the stiffness parameter through compositional adjustment, finding the optimal balance point where sufficient stiffness prevents dishing while excessive stiffness that causes scratching is avoided
4Duration of action of stationary object
If polyether prepolymer is used, then pad life and stiffness are improved, but damping performance decreases
Solution Approach 1:
The patent creates a composite where polyether segments provide stiffness and pad life while polyester segments contribute damping performance, achieving a synergistic effect that balances durability with energy dissipation
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 polyurethane CMP pads exhibit improved within-wafer and within-die uniformity, reduced dishing and erosion, extended pad life, and enhanced polishing performance by effectively absorbing energy during cyclic deformation.
Implementation Method 1
CMP pads with low rebound tend to absorb relatively high amounts of energy during cyclic deformation, causing less dishing during polishing
Implementation Method 2
A portion of this energy is dissipated inside the pad as heat, and the remaining portion is stored in the pad and subsequently released as elastic energy
Implementation Method 3
a foaming agent introduced into the reaction mixture to form the polishing pad
Implementation Method 4
the resulting pads exhibit a moderate hardness with high porosity
Data Source
AI summary
Polyurethane composition based on a certain polyether and polyester prepolymer reaction mixture, wherein the composition is utilized in manufacturing chemical mechanical polishing/planarizing (CMP) pads. The CMP pads have low rebound and can dissipate irregular energy as well as stabilize polishing to yield improved uniformity and less dishing of the substrate.