CMP Pad with Consistent Positive Zeta Potential
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Solution Overview
Problem
Current chemical mechanical polishing (CMP) pads lack consistent positive zeta potential across their surfaces, which affects the planarization performance and productivity in semiconductor device manufacturing, particularly in maintaining optimal performance across varying pH levels.
Innovation Solution
A CMP pad with a polishing layer composition comprising a polyfunctional isocyanate, a hydroxyl-substituted quaternary ammonium curative, and optionally microelements, ensuring a consistent positive zeta potential across the entire surface, independent of pH from 2 to 12, when paired with a positively charged silica abrasive slurry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional CMP pads are used, then polishing can be performed, but the zeta potential is not consistently positive across the surface and varies with pH, reducing planarization performance
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition of the polishing pad to achieve a consistently positive zeta potential. Specifically, it uses a polyfunctional isocyanate with unreacted NCO groups and a quaternary ammonium curative, adjusting the stoichiometric ratio to create a surface with stable positive charge across varying pH conditions, thereby improving reliability and planarization performance
Solution Approach 2:
The invention uses composite materials by combining specific chemical components in the polishing pad formulation: a polyfunctional isocyanate (with at least two unreacted NCO groups per molecule), a quaternary ammonium curative (with at least two hydroxyl groups per molecule), and optionally a second curative. This composite chemical structure creates the desired consistent positive zeta potential across the pad surface
2Adaptability or versatility
If pH varies during polishing, then different polishing conditions can be accommodated, but the zeta potential of conventional pads changes, affecting performance consistency
Solution Approach 1:
The patent addresses pH variation by changing the chemical parameters of the polishing pad formulation. The use of unreacted isocyanate groups and quaternary ammonium curative creates a surface chemistry that maintains positive zeta potential across pH 2-12, making the pad adaptable to different pH conditions while maintaining reliability
3Productivity
If material removal rate is increased, then productivity improves, but selectivity between different materials may be compromised
Solution Approach 1:
The patent uses parameter changes in the chemical composition to achieve both high removal rate and selectivity. By adjusting the stoichiometric ratio of curatives to isocyanate groups and selecting specific chemical components, the pad surface creates optimal interaction with silica abrasive particles, enabling enhanced material removal while maintaining selectivity between different semiconductor materials
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 provides improved CMP planarization performance and productivity by maintaining a stable positive zeta potential, enhancing material removal rates and enabling the processing of complex semiconductor substrates with consistent results across different pH conditions.
Implementation Method 1
a polishing pad having a positive zeta potential, the polishing pad comprising a polishing layer having a composition, and a polishing surface
Implementation Method 2
When an active slurry contains an abrasive having a positive zeta potential (e.g., alumina), the polishing surface may be designed to have a more negative zeta potential relative to other regions of the surface of the polishing article to attract the abrasive to the interface between the polishing article and the liquid interface
Implementation Method 3
the composition is a reaction product of ingredients, comprising: (a) a polyfunctional isocyanate having an average of at least two unreacted isocyanate (NCO) groups per molecule; (b) a first curative consisting of a hydroxyl substituted quaternary ammonium
Implementation Method 4
In conventional CMP, a wafer is mounted on a carrier assembly and positioned in contact with a polishing pad in a CMP apparatus... the wafer surface is polished and made planar by the chemical and mechanical action of the pad surface and slurry
Data Source
AI summary
The present invention concerns a chemical mechanical polishing pad having a polishing layer that possesses a consistent positive zeta potential across the entire surface. Also disclosed is a chemical mechanical polishing method using the polishing pad together with a positively charged slurry.