Cationic Fluoropolymer Polishing Pad for CMP Removal Rate
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Solution Overview
Problem
Current Chemical Mechanical Planarization (CMP) processes for 3D NAND manufacturing are bottlenecked by slow removal rates during the planarization of thick dielectric layers, with conventional pads and slurries failing to achieve significant increases in removal rate without introducing polishing defects.
Innovation Solution
Development of a polymer-polymer composite polishing pad with a hydrophilic polymeric matrix and embedded cationic fluoropolymer particles, which enhance the attraction of slurry particles and increase removal rates while maintaining low defectivity by modifying the pad's surface zeta potential and mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional CMP pads and slurries are used for planarization of thick dielectric layers, then the process is simple and reliable, but the removal rate is slow and process time is lengthy
Solution Approach 1:
The invention modifies the zeta potential of the polishing pad surface by incorporating charged polymer particles (e.g., carboxylated particles with negative charge or amine-functionalized particles with positive charge) into the pad matrix. This chemical parameter change enables electrostatic attraction of oppositely charged slurry particles (e.g., cationic ceria or anionic silica), significantly increasing the concentration of active particles at the pad-wafer interface and thereby enhancing the removal rate without extending process time
Solution Approach 2:
The invention creates a composite polishing pad structure by integrating charged polymer particles within the pad matrix. This composite material combines the mechanical properties of the base pad material with the electrostatic properties of the charged particles, enabling both high removal rate through electrostatic particle concentration and maintenance of pad structural integrity for reliable operation
2Productivity
If higher pressure and velocity are applied to increase removal rate, then the removal rate increases, but polishing defects are introduced
Solution Approach 1:
The invention replaces the purely mechanical approach of increasing pressure and velocity with a chemical/electrostatic mechanism. By utilizing electrostatic attraction between charged pad particles and oppositely charged slurry particles, the system concentrates active particles at the interface without requiring increased mechanical energy input, thereby achieving higher removal rates without introducing pressure-induced polishing defects
3Productivity
If slurry particle concentration is increased to improve removal rate, then the removal rate increases, but slurry stability decreases and particle precipitation occurs
Solution Approach 1:
The invention performs preliminary action by pre-charging the polishing pad particles with appropriate electrical charge before the polishing process begins. This pre-conditioning of the pad surface creates electrostatic attraction zones that actively capture and concentrate slurry particles at the pad-wafer interface, ensuring high particle concentration and sustained removal rate throughout the polishing process without slurry depletion or precipitation issues
Solution Approach 2:
The charged polymer particles in the pad matrix serve as intermediaries that facilitate the interaction between the slurry particles and the wafer surface. These intermediary particles create electrostatic fields that attract and hold slurry particles, effectively mediating the transfer of material from wafer to slurry to pad, thereby maintaining slurry stability and preventing particle precipitation while sustaining high removal rates
Data Source
AI summary
The invention provides a polymer-polymer composite polishing pad useful for polishing or planarizing a substrate of at least one of semiconductor, optical and magnetic substrates. The polymer-polymer composite polishing pad includes a polishing layer having a polishing surface and a polymeric matrix forming the polishing layer. The polymer matrix is hydrophilic as measured with distilled water at a pH of 7 at a surface roughness of 10 μm rms after soaking in distilled water for five minutes. Cationic fluoropolymer particles having nitrogen-containing end groups are embedded in the polymeric matrix. The cationic fluoropolymer particles can increase polishing removal rate of substrate on a patterned wafer when polishing with slurries containing anionic colloidal silica.