Selective Silicon Nitride Etching Using Fluoroethane and Oxidizer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current silicon nitride plasma etching processes often result in a rough SiN layer, which can lead to substrate damage and require additional processing steps, and existing etch gases may not provide sufficient selectivity and low surface roughness for gate spacer layer etching.
Innovation Solution
The introduction of an oxidizer at a predetermined flow rate and an etch gas with the formula CxHyFz, where x is 2-5, z is 1 or 2, and a fluorine atom is located on a terminal carbon atom, into a plasma reaction chamber to achieve infinite selectivity and minimize SiN roughness to less than 10 nm, using gases such as fluoroethane, 1-fluoropropane, and 1,1-difluoropropane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etch gases (e.g., CF4, SF6) are used for silicon nitride etching, then etching capability is achieved, but surface roughness increases and selectivity to substrate decreases
Solution Approach 1:
The patent changes the chemical composition parameters of the etch gas from conventional CF4 or SF6 to a specific hydrofluorocarbon formula CxHyFz with controlled ratios of carbon, hydrogen, and fluorine atoms. This parameter change achieves both low surface roughness (0-10 nm) and high selectivity to silicon nitride over silicon and silicon oxide substrates, resolving the contradiction between manufacturing precision and reliability
Solution Approach 2:
The patent uses a composite gas mixture comprising hydrofluorocarbon etch gas combined with oxygen or nitrogen. This composite approach creates a plasma environment that simultaneously provides anisotropic etching capability, maintains surface smoothness, and achieves infinite selectivity to the substrate, effectively resolving the trade-off between etching performance and substrate protection
2Reliability
If H rich etch molecules are used to selectively etch silicon nitride, then selectivity increases, but carbon implantation into substrate occurs requiring additional processing steps
Solution Approach 1:
The patent optimizes the hydrogen-to-fluorine ratio in the etch gas to achieve high selectivity without excessive carbon implantation. By carefully controlling the composition parameters (CxHyFz where y/z falls within specific ranges), the process maintains infinite selectivity to silicon nitride while avoiding the need for subsequent carbon removal steps, thus resolving the contradiction between reliability and device complexity
Solution Approach 2:
The patent introduces oxygen or nitrogen as a additive gas to the hydrofluorocarbon etch gas. This oxidation approach prevents carbon implantation into the substrate by oxidizing carbon species during the etching process, thereby maintaining high selectivity without requiring additional processing steps to remove carbon contamination
3Reliability
If anisotropic etching is achieved for gate spacer layer removal, then selectivity to substrate is improved, but surface roughness increases
Solution Approach 1:
The patent employs a composite plasma environment created by combining hydrofluorocarbon etch gas with oxygen or nitrogen. This composite approach enables simultaneous achievement of anisotropic etching (for selectivity) and surface smoothing (for low roughness), with the oxygen/nitrogen component preventing excessive roughness formation while the hydrofluorocarbon provides the anisotropic etching capability
Solution Approach 2:
The patent adjusts the chemical composition parameters of the etch gas to CxHyFz with specific constraints on x, y, and z values. This parameter optimization enables the plasma to provide both the directional etching needed for selectivity and the surface passivation needed to maintain roughness below 10 nm, resolving the contradiction between reliability and manufacturing precision
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 ensures anisotropic etching with low surface roughness, reducing substrate damage and eliminating the need for subsequent treatments like HBr/O2 or N2/H2 plasma, while maintaining selectivity between silicon nitride and substrate materials.
Implementation Method 1
Silicon nitride plasma etching processes are disclosed that minimize the SiN roughness layer
Implementation Method 2
simultaneously introducing an oxidizer at a predetermined flow rate and an etch gas into a plasma reaction chamber
Data Source
AI summary
Silicon nitride plasma etching processes are disclosed that minimize the SiN roughness layer on a substrate having a SiN layer thereon by simultaneously introducing an oxidizer at a predetermined flow rate and an etch gas into a plasma reaction chamber containing the substrate. The etch gas has the formula CxHyFz, wherein x is 2-5, z is 1 or 2, 2x+2=y+z, and a fluorine atom is located on a terminal carbon atom of the etch gas.