Selective Etching of Nickel and Cobalt Silicide Lines
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Solution Overview
Problem
Current etching chemistries are inadequate for selectively removing nickel silicide and cobalt silicide from semiconductor substrates without affecting other materials like silicon nitride or undoped silicon dioxide, which is crucial for forming precise conductive lines in integrated circuitry.
Innovation Solution
A method involving exposure to a fluid comprising H2SO4, H2O2, H2O, and HF at temperatures above 50°C and pressures between 350 Torr to 1100 Torr is used to etch nickel silicide and cobalt silicide, providing selective etching relative to silicon nitride or undoped silicon dioxide, allowing for the formation of conductive lines with precise recessing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional etching chemistries are used, then etching of conductive metal silicides can be achieved, but selectivity against other materials like silicon nitride or undoped silicon dioxide is insufficient
Solution Approach 1:
The patent modifies the chemical composition parameters of the etching fluid by incorporating specific ratios of H2SO4, H2O2, HF, and H3PO4, along with temperature control (50-100°C), to achieve differential etching rates across multiple materials. This parameter optimization enables simultaneous selectivity against silicon nitride, undoped silicon dioxide, and doped silicon dioxide while maintaining effective silicide removal
Solution Approach 2:
The etching fluid employs a composite chemical system combining multiple acids (H2SO4, HF, H3PO4) and oxidants (H2O2) in specific concentrations. This composite formulation creates synergistic effects where the combination provides enhanced selectivity and etching performance that individual chemicals cannot achieve alone, allowing differentiated attack on silicides versus dielectric materials
2Productivity
If etching rate is increased to improve productivity, then manufacturing efficiency increases, but selectivity control becomes more difficult
Solution Approach 1:
The patent achieves high etching rates (e.g., 50-100 nm/min for nickel silicide) while maintaining selectivity by optimizing temperature (50-100°C range) and chemical concentrations. The elevated temperature accelerates the etching kinetics for silicides while the specific chemical composition ensures dielectric materials etch at controlled rates, thus achieving both productivity and precision simultaneously
3Manufacturing precision
If selective etching of silicides is achieved, then conductive line formation precision improves, but process complexity increases
Solution Approach 1:
The patent develops a universal etching fluid composition that simultaneously provides selectivity against multiple material types (silicon nitride, undoped silicon dioxide, doped silicon dioxide) in a single process step. This multi-functional chemistry eliminates the need for multiple sequential etching processes, thereby achieving high conductive line precision while actually reducing overall process complexity
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
This approach enables efficient and selective etching of nickel silicide and cobalt silicide, achieving high etch rates while maintaining selectivity over other substrate materials, thereby facilitating the formation of conductive lines with precise dimensions and structures in semiconductor processing.
Implementation Method 1
at least one of nickel silicide or cobalt silicide is exposed to a fluid comprising H2SO4, H2O2, H2O, and HF effective to etch the at least one of nickel silicide or cobalt silicide from the substrate
Implementation Method 2
The at least one of elemental nickel or the elemental cobalt and silicon of the line are annealed effective to form at least one of a nickel silicide-comprising line or a cobalt silicide-comprising line
Data Source
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AI summary
The invention includes methods of etching nickel silicide and cobalt silicide. In one implementation, at least one of nickel silicide or cobalt silicide is exposed to a fluid comprising H2SO4, H2O2, H2O,and HF at a temperature of at least 50°C and at a pressure from, 350 Torr to 1100 Torr effective to etch the at least one of nickel silicide or cobalt silicide from the substrate.