Organically Modified Silica CMP Slurry for Scratch Reduction
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Solution Overview
Problem
Existing CMP slurries for copper wiring in semiconductor fabrication face challenges in achieving high removal rates while minimizing scratches, particularly due to the use of prior particles with wide particle size distributions and irregular shapes, which can cause micro-scratches and damage to soft copper and low-k materials.
Innovation Solution
The development of an organically modified colloidal silica (ORMOSIL) slurry with controlled particle size and shape, using organometallic alkoxides like methyl trimethoxysilane, phenyl trimethoxysilane, or vinyl trimethoxysilane, and additives such as hydrophilic agents and polymeric dispersing agents to create a slurry with improved polishing properties and reduced friction, thereby minimizing scratches and optimizing CMP removal rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If prior particles with wide particle size distribution and irregular shapes are used, then the slurry can achieve mechanical polishing action, but micro-scratches and damage occur on soft copper and low-k materials
Solution Approach 1:
The patent changes the particle size parameter from wide distribution to narrow distribution (standard deviation ≤ 30 nm), and changes the shape parameter from irregular to spherical. These parameter changes eliminate micro-scratches while maintaining effective mechanical polishing action on copper and low-k materials.
Solution Approach 2:
The patent uses composite polishing particles consisting of colloidal silica core with organic modifier coating, creating a spherical composite structure that combines the mechanical polishing capability of silica with the scratch-reducing properties of the spherical geometry and organic surface modification.
2Reliability
If copper wiring is used in integrated circuits, then electrical conductivity is improved, but the material becomes softer and more prone to scratching
Solution Approach 1:
The patent changes the particle hardness parameter by using spherical colloidal silica particles with controlled size and organic modification, creating a polishing system that is less abrasive and more selective, thereby protecting soft copper from scratching while maintaining polishing effectiveness.
Solution Approach 2:
The patent applies local quality by making the polishing particles spherical with uniform size distribution, concentrating the polishing action on specific asperities while minimizing contact area and pressure on the bulk copper surface, thereby reducing scratch formation.
3Productivity
If low-k material is used as insulating material, then integration density is improved, but the material becomes softer and easily broken and damaged
Solution Approach 1:
The patent changes the particle size parameter to nanoscale (standard deviation ≤ 30 nm) and shape to spherical, creating ultra-fine polishing particles that can selectively remove copper at higher rates while being gentle enough to protect the softer low-k dielectric material from damage.
Solution Approach 2:
The patent applies partial action by using particles that are small enough to selectively polish copper features without applying excessive mechanical stress to the low-k material, achieving differential removal rates that protect the insulating layer while effectively planarizing copper interconnects.
4Object-affected harmful factors
If spherical particles with narrow particle size distribution are used, then scratches are reduced, but polishing rate may be reduced
Solution Approach 1:
The patent creates composite spherical particles with colloidal silica core and organic modifier coating, where the core provides polishing capability and the coating controls friction and selectivity, achieving both scratch reduction and maintained polishing rate through the synergistic composite structure.
Solution Approach 2:
The patent optimizes the particle size parameter to a specific nanoscale range with narrow distribution, and changes the surface chemistry parameter through organic modification, creating particles that maintain high polishing rates on copper while minimizing scratches on both copper and low-k materials through controlled friction and selectivity.
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 ORMOSIL slurry effectively reduces scratches and dishing phenomena, achieving a desired CMP removal rate with improved selectivity and uniformity, suitable for ultra-highly integrated semiconductor processing, particularly in copper wiring processes with design rules of 0.13 μm or less.
Implementation Method 1
adding an organic solvent and an acid to organometallic alkoxide to synthesize organically modified colloidal silica particles
Implementation Method 2
adding an organic solvent and an acid to organometallic alkoxide to synthesize organically modified colloidal silica particles
Implementation Method 3
mechanical polishing is achieved by polishing particles of the slurry and surface protrusions 9 of the pad 4
Implementation Method 4
chemical etching, which is performed using a slurry, are simultaneously conducted... the surface of the wafer is chemically transformed by an acidic or basic solution of the slurry to instantaneously form a layer weakly bonded to the surface
Data Source
AI summary
A CMP slurry is provided comprising polishing particles, the polishing particle comprising organically modified colloidal silica. Also, a method of preparing a CMP slurry is provided, comprising the steps of: preparing polishing particles comprising organically modified silica; converting the polishing particles into an aqueous state; and adding pure water, a hydrophilic additive and a dispersing agent to the polishing particles. The polishing particles can be synthesized using a sol-gel process. According to the invention, a slurry having excellent polishing properties can be prepared, in which the surface properties of colloidal silica are changed to control the physical properties of the polishing particles and which can ensure a desired CMP removal rate while minimizing the occurrence of scratches.