Aromatic Isocyanate CMP Pad for Semiconductor Planarization
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Solution Overview
Problem
Conventional chemical mechanical polishing (CMP) pads fail to provide acceptable removal rates and planarization performance for semiconductor wafers, despite advancements in materials and processes.
Innovation Solution
Development of CMP polishing pads with a specific formulation involving a polyurethane layer formed from a reaction mixture of aromatic isocyanates, polyols, and aromatic diamines, optimized for density, hardness, and surface texture, paired with a ceria slurry to enhance polishing performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional CMP pads with aliphatic isocyanate and polysiloxane-polyalkyleneoxide surfactant are used, then damping performance is improved, but removal rate in polishing deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters by replacing aliphatic isocyanate with aromatic isocyanate (MDI or TDI) and modifying the surfactant system to use polyether polyol with specific molecular weights and ratios. This chemical parameter change resolves the contradiction by achieving both acceptable damping performance and significantly improved removal rates with ceria slurry.
Solution Approach 2:
The patent creates a composite polishing pad structure combining aromatic isocyanate-based polyurethane with specific polyether polyols and surfactants. This composite material approach allows the pad to simultaneously achieve the required mechanical stability and enhanced chemical-mechanical polishing performance with ceria abrasive.
2Strength
If polishing pad density is increased to improve mechanical strength, then pad durability is improved, but surface texture quality deteriorates
Solution Approach 1:
The patent applies local quality by creating a surface layer with optimized composition (higher polyether polyol content and surfactant concentration) that provides superior surface texture and porosity, while the bulk material maintains higher density and mechanical strength. This gradient structure resolves the contradiction between strength and surface quality.
Solution Approach 2:
The patent incorporates porous structure in the surface layer through controlled foam formation and surfactant action, creating voids and channels that enhance surface texture and slurry penetration. This porous surface layer on a denser substrate resolves the contradiction by providing both mechanical strength and surface texture quality.
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 new CMP pads achieve superior removal rates and planarization efficiency, with improved surface texture and mechanical properties, outperforming traditional pads when used with ceria abrasive.
Implementation Method 1
the polyurethane is a product of a reaction mixture comprising (i) a liquid aromatic isocyanate component... and (ii) a liquid polyol component
Implementation Method 2
the wafer surface is polished and made planar by the chemical and mechanical action of the pad surface and slurry
Implementation Method 3
the wafer surface is polished and made planar by the chemical and mechanical action of the pad surface and slurry
Implementation Method 4
In addition to the contact force between a pad and slurry particles, surface forces also act between the wafer and the slurry particles, and impact the CMP material removal rate
Data Source
AI summary
CMP polishing pads or layers made from a polyurethane reaction product of a reaction mixture comprising (i) a liquid aromatic isocyanate component comprising one or more aromatic diisocyanates or a linear aromatic isocyanate-terminated urethane prepolymer, and (ii) a liquid polyol component comprising a) one or more polymeric polyols, b) from 12 to 40 wt. %, based on the total weight of the liquid polyol component, of a curative mixture of one or more small chain difunctional polyols having from 2 to 9 carbon atoms, a liquid aromatic diamine, wherein the mole ratio of the total moles of hydroxyl and amino moieties in the liquid polyol, small chain difunctional polyols and liquid aromatic diamine to mole of isocyanate in the aromatic diisocyanates or linear aromatic isocyanate-terminated urethane prepolymer ranges from 1.0:1.0 to 1.15:1.0. The polishing layer is capable of forming a total texture depth, as measured by Sdr, a parameter defined by the ISO 25178 standard, upon treatment by a surface conditioning disk, in the range of from 0 to 0.4. Also disclosed is a chemical mechanical polishing method using the polishing pad together with a ceria abrasive slurry.