CMP Polishing Pad Striation Reduction via Microsphere Fluidization
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Solution Overview
Problem
Conventional polishing pads for chemical mechanical planarization often exhibit striations due to variations in bulk density of microspheres, leading to unpredictable and detrimental polishing performance, which existing methods and apparatuses are inadequate in controlling effectively.
Innovation Solution
A method and apparatus that utilize a storage hopper with a porous membrane and fluidizing gas source to reduce the initial bulk density of microspheres by at least 20%, ensuring consistent flow and minimizing striations, involving a bulk density control unit that fluidizes the microspheres and uniformly distributes them for forming a polishing pad with reduced striations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If microspheres are blended and mixed in a mass flow feed delivery system, then the polishing pad can be formed efficiently, but striations occur due to variations in bulk density of microspheres
Solution Approach 1:
The hopper is equipped with a vibration mechanism that vibrates the hopper walls to prevent microsphere clustering and maintain uniform bulk density during delivery, thereby eliminating striations while preserving efficient mass flow feed delivery
Solution Approach 2:
The bulk density of microspheres is controlled by adjusting parameters such as hopper vibration frequency, gas flow rate through porous membranes, or hopper angle, allowing optimization of both flow efficiency and density uniformity
2Speed
If microspheres are allowed to flow freely in mass flow feed delivery system, then delivery is simple and fast, but microspheres cluster together causing striations
Solution Approach 1:
Vibration of the hopper prevents microsphere clustering during rapid delivery, maintaining both high delivery speed and uniform distribution by continuously agitating the microspheres to prevent settling and clustering
Solution Approach 2:
Gas flow through porous membranes in the hopper creates fluidization effects that keep microspheres suspended and uniformly distributed during rapid delivery, preventing clustering while maintaining high delivery rates
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 solution effectively reduces striations in polishing pads, resulting in consistent and improved polishing performance by ensuring uniform bulk density distribution, addressing the inefficiencies of prior art in controlling bulk density and enhancing the reliability of CMP processes.
Implementation Method 1
fluidizing the microspheres and reducing the initial bulk density by feeding gas into the plenum
Data Source
AI summary
The present invention provides a method of forming a chemical mechanical polishing pad, comprising providing a tank with polymeric materials and providing a storage hopper with microspheres having an initial bulk density, wherein the storage hopper further comprises a porous membrane provided over a plenum. The method further provides the steps of connecting a fluidizing gas source to the plenum through a gas inlet line and fluidizing the microspheres and reducing the initial bulk density by feeding gas into the plenum. In addition, the method further provides the steps of providing a delivery system for delivering the polymeric materials and the microspheres to a mixer, forming a mixture of the polymeric materials and the microspheres, pouring the mixture into a mold to form a molded product and cutting the molded product into the polishing pad.