Non-Porous Composite CMP Pad for Reduced Metal Dishing
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Solution Overview
Problem
Existing chemical mechanical polishing (CMP) pads, particularly non-porous pads, suffer from issues such as dishing and reduced removal rates when used on metal/dielectric composite structures, leading to non-planarity and resistance variations in integrated circuit fabrication.
Innovation Solution
A non-porous CMP pad with a polymer matrix and agglomerates of polymer particles, having a specific tensile modulus and size range, provides improved planarization efficiency and reduced dishing, characterized by a viscoelastic property and high Energy Loss Factor (GEL) to enhance polishing performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If porous closed cell pads are used for polishing dielectric layers, then polishing effectiveness is improved, but rigidity decreases and texture collapse occurs leading to dishing
Solution Approach 1:
The invention uses a composite material structure combining a polymeric matrix with embedded polymeric particles of different hardness. The softer matrix provides compliance and texture stability while the harder particles maintain rigidity and prevent dishing, resolving the contradiction between polishing effectiveness and pad rigidity.
Solution Approach 2:
The pad structure incorporates regions of different material properties - the polymeric matrix provides local compliance for texture stability while embedded polymeric particles provide local rigidity. This local differentiation allows the pad to simultaneously achieve good removal rate and prevent dishing.
2Reliability
If non-porous pads with high shear and elastic modulus are used, then microtexture resistance to glazing is improved, but dishing occurs on metal/dielectric composite structures
Solution Approach 1:
The composite structure of polymeric matrix with embedded polymeric particles creates a multi-phase material that combines the benefits of high modulus materials (resistance to glazing) with controlled compliance (prevention of dishing). The harder particles provide microtexture stability while the softer matrix prevents excessive rigidity that causes dishing.
Solution Approach 2:
The invention changes the material parameters by selecting polymeric particles with different hardness than the matrix, creating a gradient of mechanical properties. This parameter differentiation allows the pad to maintain microtexture stability through the harder particles while preventing dishing through the overall compliance of the composite structure.
3Productivity
If porous pads are used for metal/dielectric composite polishing, then initial removal rate is improved, but slurry effluent hold up in pores causes performance issues
Solution Approach 1:
The invention uses a non-porous material structure to eliminate the harmful effect of slurry effluent hold up in pores. By removing porosity entirely, the pad prevents slurry retention while maintaining removal rate through the mechanical action of the composite polymeric structure and embedded particles.
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 pad achieves reduced dishing and maintains high removal rates, minimizing non-planarity and resistance variations, while being less susceptible to glazing, thus improving the quality of integrated circuit fabrication.
Implementation Method 1
This leads to a high rate of relative motion between the substrate and the polishing pad that abrades the substrate surface, leading to removal of material and planarization
Implementation Method 2
The polishing layer is viscoelastic. The polishing layer can have a GEL of greater than 1000 Pa−1
Data Source
AI summary
A chemical mechanical polishing pad comprising a substantially non-porous polishing layer, the polishing layer comprising a polymer matrix and agglomerates of polymer particles embedded in the polymer matrix wherein the polymer particles are present in amounts of 5 to 35 weight percent based on weight of the polishing layer, the agglomerates have a size of greater than 1 μm, the polymer particles have a tensile modulus higher than a tensile modulus of the polymer matrix. The polishing layer viscoelastic and has a GEL of greater than 1000 Pa−1. Polishing a metal/insulator composite with such a pad can result in low amounts of dishing of the metal feature.