Acidic CMP Slurry for Selective Barrier Removal
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Solution Overview
Problem
Current chemical mechanical polishing (CMP) compositions face challenges in selectively removing barrier materials relative to interconnect metals and dielectric materials, particularly in low-k and ultra-low k integrations, where high selectivity and low metal and dielectric losses are required, while maintaining low metal removal rates to prevent dishing and preserving the integrity of fragile low-k dielectric materials.
Innovation Solution
A CMP composition comprising water, 1 to 40 wt% abrasive with an average particle size of ≤100 nm, 0 to 10 wt% oxidizer, and 0.001 to 5 wt% quaternary compound, along with a material having a specific formula, is used to create a polishing solution with a pH ≤5, which effectively removes barrier materials like tantalum nitride with high selectivity over copper and low-k dielectric materials, even at low down force pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If neutral-to-basic polishing slurries are used to remove barrier materials, then barrier material removal rate is improved, but selectivity over interconnect metals deteriorates due to high metal removal rates causing dishing
Solution Approach 1:
The patent changes the pH parameter from neutral-to-basic to acidic range (pH 2-7.5), which fundamentally alters the chemical reaction pathways. This parameter change enables selective removal of barrier materials while suppressing metal dissolution, resolving the contradiction between removal rate and selectivity
Solution Approach 2:
The patent employs a composite slurry formulation containing multiple components working synergistically: oxidizing agents (hydrogen peroxide, potassium iodate) for chemical activation, corrosion inhibitors (benzotriazole, iminodiacetic acid) for metal protection, and specific surfactants. This composite approach enables simultaneous achievement of high barrier removal and metal preservation
2Productivity
If oxidizing agents are added to increase barrier material removal rate, then productivity is improved, but harmful effects increase due to oxidation of tantalum forming unwanted oxide layers
Solution Approach 1:
The patent optimizes the concentration and type of oxidizing agents, using them in controlled amounts (hydrogen peroxide 0.05-5 wt%, potassium iodate 0.01-1 wt%) and controlling pH conditions to favor selective oxidation of copper over tantalum, minimizing unwanted oxide layer formation while maintaining high removal rates
Solution Approach 2:
The patent introduces corrosion inhibitors as intermediary substances that mediate between the oxidizing agents and the metal surfaces. These inhibitors selectively adsorb on metal surfaces, preventing unwanted oxidation of tantalum while allowing controlled oxidation of copper and barrier materials
3Reliability
If low down force pressures are used to prevent damage to low-k dielectric materials, then reliability is improved, but barrier material removal rate decreases
Solution Approach 1:
The patent replaces reliance on high mechanical pressure with chemically-driven removal mechanisms. The acidic slurry with oxidizing agents creates strong chemical etching action that achieves high removal rates independent of mechanical pressure, enabling low down force operation that protects low-k dielectrics
Solution Approach 2:
The patent changes the dominant removal mechanism from mechanically-driven to chemically-driven by adjusting slurry composition (acidic pH, oxidizing agents). This parameter change decouples removal rate from applied pressure, allowing high removal rates at low pressures suitable for fragile low-k dielectrics
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 achieves high barrier material removal rates with favorable selectivity over other materials, reducing dishing and damage to low-k dielectric materials, while minimizing delamination and fracture, thus enhancing wafer throughput and polishing performance.
Implementation Method 1
1 to 40 wt% abrasive having an average particle size of ≤100 nm
Implementation Method 2
0 to 10 wt% oxidizer
Data Source
AI summary
A method for chemical mechanical polishing of a substrate comprising a barrier material in the presence of at least one of an interconnect metal and a low-k dielectric material using a chemical mechanical polishing composition comprising water; 1 to 40 wt % abrasive having an average particle size of ≦100 nm; 0.001 to 5 wt % quaternary compound; a material having a formula (I):wherein R is selected from C2-C20 alkyl, C2-C20 aryl, C2-C20 aralkyl and C2-C20 alkaryl; wherein x is an integer from 0 to 20; wherein y is an integer from 0 to 20; wherein x+y≧1; and, wherein the chemical mechanical polishing composition has a pH≦5.