Non-aqueous Fluoride Etchant for Metal Nitride Selectivity
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Solution Overview
Problem
Current cleaning and etching compositions for microelectronic substrates are either too aggressive or not selective enough, particularly failing to effectively remove metal nitride and photoresist etch residues without damaging low-k dielectric materials or tungsten substrates, due to limitations in etch rates and substrate compatibility.
Innovation Solution
A non-aqueous cleaning composition comprising a fluoride activating agent, an oxidizer, and an anhydrous organic solvent, with a pH of 5.5 or less, specifically designed to selectively etch titanium nitride and photoresist etch residues relative to copper and low-k dielectric layers, providing high etch rates and broad compatibility with tungsten and low-k dielectric materials without using hydrogen peroxide or particle-generating corrosion inhibitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If acidic fluoride based chemistries are used for metal nitride etching, then etch rates improve, but substrate compatibility deteriorates (particularly with low-k dielectrics and tungsten)
Solution Approach 1:
The patent changes the chemical parameters of the etching composition by using non-aqueous solvents (such as propylene carbonate, ethylene carbonate, dimethyl carbonate) instead of traditional aqueous solutions. This fundamental parameter change allows the composition to achieve high etch rates for metal nitrides while maintaining compatibility with low-k dielectrics and tungsten substrates, resolving the contradiction between etch rate and substrate compatibility
Solution Approach 2:
The invention creates a composite cleaning composition that combines multiple components: fluoride source (such as HF, NF3, or CF4), non-aqueous solvent system, and optional additives. This composite formulation synergistically provides both high etch rate for metal nitrides and selectivity/compatibility with sensitive substrates, simultaneously achieving both contradictory requirements
2Reliability
If traditional cleaning compositions are used, then broad substrate compatibility is maintained, but etch rates for metal nitride become too low
Solution Approach 1:
The patent fundamentally changes the solvent parameter from aqueous to non-aqueous systems. This parameter change enables the composition to interact with metal nitride surfaces more effectively, dramatically increasing etch rates while the non-aqueous nature of the solvent system prevents unwanted reactions with water-sensitive substrates like low-k dielectrics and tungsten, thus maintaining substrate compatibility
3Productivity
If aqueous-based metal nitride etch chemistries are used, then etch rates are achieved, but compatibility with tungsten and low-k dielectric materials deteriorates
Solution Approach 1:
The invention changes the physical state parameter of the solvent from aqueous to non-aqueous. This eliminates water from the composition, preventing water-related corrosion mechanisms that would otherwise attack tungsten and low-k dielectric materials. The non-aqueous fluoride-based chemistry maintains effective etching of metal nitrides while being benign to water-sensitive substrates
Solution Approach 2:
The non-aqueous solvent acts as an intermediary medium that facilitates the delivery of fluoride species to metal nitride surfaces for etching, while simultaneously providing a protective environment that prevents harmful interactions with tungsten and low-k dielectrics. The solvent mediates between the reactive fluoride species and the sensitive substrates
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 dramatic improvements in metal nitride etch rates and substrate compatibility, offering high etch rates exceeding 600-700 Å/min and excellent selectivity between titanium nitride hard masks and tungsten metals, while maintaining compatibility with low-k dielectric materials and minimizing corrosion.
Implementation Method 1
selectively etching titanium nitride and photoresist etch residues relative to copper, tungsten, and low-k dielectric layers
Implementation Method 2
about 0.01% to about 20.00% by weight of at least one oxidizer
Data Source
AI summary
Provided therefore herein is a novel acidic fluoride activated cleaning chemistry. The present invention includes novel acidic fluoride activated, unique organic-solvent based microelectronic selective etchant/cleaner compositions with high metal nitride etch and broad excellent compatibility, including tungsten (W) and low-k. It does not use W-incompatible oxidizers, such as hydrogen peroxide or particle-generating corrosion inhibitors.