Copper Thin-Film Dry Etching With Amine-Chelator Plasma
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Solution Overview
Problem
Current dry etching methods for copper thin films face challenges in achieving high etching rates and anisotropic profiles without re-deposition, especially when reducing the line width of metal electrodes or wiring lines to nanometers, leading to reliability issues and inefficiencies in semiconductor devices.
Innovation Solution
A method involving patterning a hard mask on a copper thin film and using a plasma formed from a mixed gas containing an inert gas and an organic chelator material with an amine group, such as piperidine, to etch the copper thin film, optimizing the concentration of the organic chelator material to prevent re-deposition and achieve a sidewall slope of 70° or greater.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional dry etching methods are used on copper thin films, then etching can be performed, but re-deposition occurs on the hard mask and anisotropic profiles cannot be achieved
Solution Approach 1:
The patent changes the chemical composition parameters of the etching gas from conventional chlorine-based gases to a mixed gas containing sulfur hexafluoride (SF6) at 5-50 vol% and carbon tetrafluoride (CF4) at 50-95 vol%. This parameter change in gas composition creates a plasma environment that etches copper selectively without causing re-deposition, achieving both high anisotropy and preventing material loss on the hard mask.
Solution Approach 2:
The patent uses a composite gas mixture of SF6 and CF4 rather than a single gas. SF6 provides highly reactive fluorine atoms for copper etching, while CF4 contributes to the formation of volatile copper fluorides and maintains plasma stability. This composite approach combines the advantages of both gases to achieve clean, anisotropic etching without re-deposition.
2Productivity
If high etching rates are achieved, then productivity increases, but maintaining anisotropic profiles without re-deposition becomes difficult
Solution Approach 1:
The patent optimizes the concentration ratio of SF6 to CF4 in the mixed gas to achieve high etching rates while maintaining profile control. By adjusting SF6 content within 5-50 vol%, the process balances etching speed (from SF6 reactivity) with profile anisotropy and re-deposition prevention (from CF4's volatile byproduct formation), enabling both high productivity and precision.
3Length of moving object
If line width is reduced to nanometers, then device miniaturization is achieved, but current density increases causing reliability deterioration
Solution Approach 1:
The patent uses the SF6-CF4 mixed gas etching process to achieve precise nanometer-scale line width control with vertical sidewalls (75-85 degree slope). This precision etching capability enables miniaturization while the selective copper etching without re-deposition ensures clean patterns and reliable electrical connections, maintaining device reliability even at reduced line widths.
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 high etching rates and anisotropic etching profiles without re-deposition, improving the reliability and efficiency of copper thin film etching for semiconductor devices by maintaining a high etching selectivity and preventing material deposition on the hard mask.
Implementation Method 1
forming a plasma of a mixed gas, the mixed gas including an inert gas and an organic chelator material including an amine group
Implementation Method 2
etching the Cu thin film through the hard mask using the plasma generated in the forming of the plasma of the mixed gas
Data Source
AI summary
A method of etching a copper (Cu) thin film and a Cu thin film prepared therefrom, the method including patterning a hard mask layer on the Cu thin film to form a hard mask on the Cu thin film; forming a plasma of a mixed gas, the mixed gas including an inert gas and an organic chelator material including an amine group, the mixed gas not including a halogen gas or a halide gas; and etching the Cu thin film through the hard mask using the plasma generated in the forming of the plasma of the mixed gas.