Tungsten CMP Slurry with Polyglycol and Iron Ions
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Solution Overview
Problem
Chemical mechanical polishing of tungsten often results in dishing of tungsten and erosion of underlying dielectric materials, leading to non-uniform substrate surfaces and increased corrosion rates, which can negatively impact the performance of integrated circuits.
Innovation Solution
A chemical mechanical polishing method using a composition containing water, an oxidizing agent, a polyglycol or polyglycol derivative, colloidal silica abrasive, and a source of iron (III) ions, applied with a polishing pad to inhibit tungsten dishing, reduce dielectric erosion, and lower corrosion rates, while maintaining a tungsten removal rate of ≥1,000 Å/min.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional CMP slurries are used to polish tungsten, then tungsten removal is achieved, but dishing of tungsten occurs and underlying dielectric material is eroded
Solution Approach 1:
The patent changes the chemical parameters of the CMP slurry by incorporating polyglycol (50-5000 ppm), iron ions (10-500 ppm), and controlling pH (1.5-4.5), oxidation potential (0.8-1.2 V), and temperature (20-40°C) to achieve selective tungsten removal while preventing dishing and dielectric erosion through optimized chemical reactions
Solution Approach 2:
The patent uses a composite slurry system combining polyglycol (as a polymer additive), iron ions (catalyst), colloidal silica (abrasive), and oxidizing agents (H2O2/peracetic acid) that work synergistically to provide mechanical abrasion combined with chemical oxidation, enabling controlled tungsten removal without excessive dishing or dielectric damage
2Productivity
If conventional CMP slurries are used to polish tungsten, then tungsten is removed, but corrosion rate increases
Solution Approach 1:
The patent optimizes the oxidation potential (0.8-1.2 V) and pH (1.5-4.5) parameters to control the aggressiveness of the slurry, using polyglycol as a corrosion inhibitor that forms protective complexes with metal ions, thereby reducing tungsten corrosion while maintaining adequate removal rates
Solution Approach 2:
The patent introduces polyglycol as an intermediary substance that mediates between the oxidizing agents and the tungsten substrate, forming protective complexes that prevent excessive corrosion while still allowing controlled removal through the combined chemical-mechanical action
3Shape
If polishing is performed to achieve flat surface, then dishing occurs leading to non-uniform substrate surface
Solution Approach 1:
The patent controls polishing parameters including temperature (20-40°C), pH (1.5-4.5), and oxidation potential (0.8-1.2 V) to optimize the chemical reaction rate, using polyglycol to inhibit dishing by forming protective layers that prevent excessive material removal from the center of the substrate
Solution Approach 2:
The patent uses polyglycol as a mediator that adsorbs onto the tungsten surface during polishing, forming a protective complex that prevents excessive chemical attack and mechanical removal, thereby maintaining surface uniformity while still allowing controlled planarization
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 method effectively inhibits tungsten dishing and dielectric erosion, reducing corrosion rates and achieving improved substrate surface quality, thereby enhancing the performance of integrated circuits.
Implementation Method 1
an oxidizing agent
Implementation Method 2
a colloidal silica abrasive
Data Source
AI summary
A process for chemical mechanical polishing a substrate containing tungsten is disclosed to reduce corrosion rate and inhibit dishing of the tungsten and erosion of underlying dielectrics. The process includes providing a substrate; providing a polishing composition, containing, as initial components: water; an oxidizing agent; a polyglycol or polyglycol derivative; a dicarboxylic acid, a source of iron ions; a colloidal silica abrasive; and, optionally a pH adjusting agent; providing a chemical mechanical polishing pad, having a polishing surface; creating dynamic contact at an interface between the polishing pad and the substrate; and dispensing the polishing composition onto the polishing surface at or near the interface between the polishing pad and the substrate; wherein some of the tungsten (W) is polished away from the substrate, corrosion rate is reduced, dishing of the tungsten (W) is inhibited as well as erosion of dielectrics underlying the tungsten (W).