Polishing Pad Manufacturing via Viscosity-Controlled Foaming
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Solution Overview
Problem
Conventional methods for forming pores on polishing pads in the CMP process fail to produce uniform and minute-sized pores, which are essential for advanced semiconductor manufacturing, as they either produce pores that are too large or lack the required precision and uniformity.
Innovation Solution
A method involving the production of a urethane prepolymer with specific viscosity and mixing it with inert gas and a low-boiling blowing agent to create a polishing layer with uniformly sized pores, utilizing polypropylene glycol with tetravalent functional groups to form a three-dimensional bonding structure, which maintains pore shape and enhances polishing performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional pore forming methods (inert gas only or chemical blowing agent) are used, then the polishing pad can be manufactured with some porosity, but the pore size cannot be controlled to be uniformly 31 µm or smaller
Solution Approach 1:
The patent changes the physical and chemical parameters of the blowing agent system by selecting specific low-boiling-point compounds (diethyl carbonate, ethyl formate, ethyl acetate) with boiling points between 60-150°C, and controls the urethane prepolymer viscosity within 20,000-40,000 mPas at 25°C. These parameter specifications enable uniform pore formation of 31 µm or smaller while maintaining manufacturability through controlled chemical reactions.
Solution Approach 2:
The patent employs a composite blowing agent system combining inert gas (5-40% by volume) with low-boiling chemical blowing agents (0.1-10% by volume). This composite approach leverages the advantages of both systems: the inert gas provides stable bubble nucleation while the chemical blowing agent ensures uniform expansion and pore formation, achieving precise pore size control that neither agent could achieve alone.
2Manufacturing precision
If the viscosity of urethane prepolymer is not controlled within 20,000-40,000 mPas at 25°C, then the mixing and gelation process can be simplified, but the pore size uniformity and polishing performance deteriorate
Solution Approach 1:
The patent establishes a specific viscosity range (20,000-40,000 mPas at 25°C) for the urethane prepolymer as a critical process parameter. This parameter control ensures optimal balance between mixture流动性 (fluidity) for complete mixing and gelation, and viscosity for maintaining pore structure during curing, thereby achieving uniform pore sizes without requiring overly complex processing equipment.
3Reliability
If pores are formed without specific viscosity control and blowing agent selection, then the manufacturing process is simpler, but the polishing pad cannot maintain saturated slurry state and exhibits glazing
Solution Approach 1:
The patent creates a porous polishing pad structure with uniformly distributed pores of 31 µm or smaller through controlled foaming of the urethane prepolymer mixture. This porous structure provides capillary action and surface area for maintaining saturated slurry state during polishing, preventing glazing while the specific viscosity and blowing agent selection ensure the process remains manufacturable.
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 method achieves the production of polishing pads with pores of 31 µm or smaller in size, ensuring consistent polishing performance and extended pad lifetime, while maintaining uniformity and preventing glazing, thus supporting advanced semiconductor processes.
Implementation Method 1
mixing the urethane prepolymer with an inert gas and a low-boiling blowing agent having a boiling point of 60°C to 150°C
Implementation Method 2
low-boiling blowing agent having a boiling point of 60°C to 150°C
Implementation Method 3
manufacturing a polishing layer including porous pores by causing a mixture produced at the mixing to be subjected to gelation and curing
Data Source
Figure 1~2
Figure 3(a)~3(c')
Figure 4(a)~5
AI summary
A method of manufacturing a polishing pad includes producing an urethane prepolymer having a viscosity of 20,000 cps (at 25°C) to 40,000 cps (at 25°C) by mixing a plurality of polymers, mixing the urethane prepolymer with an inert gas and a low-boiling blowing agent having a boiling point of 60°C to 150°C, and manufacturing a polishing layer including porous pores by causing a mixture produced at the mixing to be subjected to gelation and curing in a predetermined cast.