Plasma Etching of 3D Dielectric Layers Using Sequential Protective Films
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Solution Overview
Problem
The challenge in microelectronics is to precisely etch dielectric layers on three-dimensional (3D) structures like FinFET transistors without damaging the underlying semiconductor material or leaving residues, especially as feature sizes decrease beyond the 32 nm node, where conventional plasma etching becomes less effective.
Innovation Solution
A method involving sequential plasma etching steps using fluorine-based compounds and oxygen to form protective layers, allowing for precise control over the etching process, ensuring that the dielectric layer is completely removed from the sides of the FinFET structure while minimizing consumption of the semiconductor material, and maintaining anisotropic etching to preserve the structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional plasma etching is used to etch the dielectric layer on 3D structures, then the dielectric layer can be removed, but the underlying semiconductor material is damaged or residues are left
Solution Approach 1:
The etching process is divided into multiple sequential steps with different chemistries and parameters. Each step targets specific aspects of dielectric removal while progressively protecting the semiconductor material, breaking down the harmful single-step etching into controlled segments
Solution Approach 2:
A preliminary etching step is performed first to selectively remove the dielectric layer before subsequent steps that protect and further process the structure. This preliminary action removes the harmful dielectric material before the semiconductor protection mechanisms are fully engaged
2Manufacturing precision
If the dielectric layer is completely removed from the sides of the FinFET structure, then spacer formation is enabled, but residues remain on the structure
Solution Approach 1:
The etching parameters (chemistry composition, power, pressure, temperature) are changed between sequential steps to optimize for complete dielectric removal in early steps while transitioning to parameters that prevent residue formation in later steps
3Productivity
If the etching process is made more aggressive to remove dielectric layer faster, then productivity increases, but anisotropic etching is compromised and structural integrity is damaged
Solution Approach 1:
The etching process uses periodic alternation between aggressive high-speed etching steps and gentler precision steps. This periodic action allows the system to achieve high overall productivity while maintaining anisotropic etching quality through the alternating phases of different etching intensities
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 precise, residue-free etching of dielectric layers on 3D structures with minimal damage to the semiconductor material, ensuring high dimensional control and maintaining the structural integrity of FinFET transistors, even at nanoscale dimensions.
Implementation Method 1
a first etching of the dielectric layer, by plasma, using a chemistry comprising at least: at least one first compound based on fluorine (F)
Implementation Method 2
generate an ionic bombardment directed mainly in a direction parallel to said flank
Implementation Method 3
form a first protective layer by oxidation of an upper portion of the top of the structure in a semiconductor material
Data Source
Figure 1~2
Figure 3A~3F
Figure 4~5
AI summary
The invention relates in particular to a method for etching a dielectric layer (40) covering at least one vertex (31) and one flank (32, 32) of a structure (30), the method comprising a plurality of sequences each comprising at least the following successive steps: - a first etching of the dielectric layer (40), by plasma, using a chemistry comprising at least: ∘ at least one first compound based on fluorine (F) and ∘ at least one second compound taken from SiwCl(2w+2) and SiwF(2w+2)w, x, y and z being integers, ∘ oxygen (O).the first etching being carried out so as to: ∘ interrupt the first etching before consumption of the entire thickness of the dielectric layer (40) located on the side (32) and after having consumed the entire thickness of the dielectric layer (40) located on the top (31), ∘ form a first protective layer (50) on the top (31) and form a second protective layer (60) on the side (32), ∘ a second etching to completely remove the second protective layer (60) while retaining a portion of the thickness of the first protective layer (50), the sequence being repeated until the complete removal of the dielectric layer (40) located on the side (32) of the structure (30).