Isotropic Silicon Nitride Etching via Remote Plasma
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Solution Overview
Problem
Conventional etching processes for semiconductor manufacturing face challenges in selectively etching silicon nitride while minimizing the etching of silicon oxide, particularly in 3D NAND structures where high aspect ratios and delicate structures require precise control to avoid deformation and crosstalk between memory cells.
Innovation Solution
The method involves flowing a fluorine-containing precursor into a remote plasma region of a semiconductor processing chamber, generating plasma effluents that are then directed into a processing region to selectively etch silicon nitride laterally, while using a purge precursor and additive precursors to form a passivation layer over silicon oxide, maintaining high selectivity and protecting exposed oxide surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a wet HF etch is used to preferentially remove silicon oxide, then oxide removal efficiency is improved, but the process cannot penetrate constrained trenches and may deform remaining material
Solution Approach 1:
The patent replaces wet chemical etching with a plasma-based process that uses reactive species and ion bombardment instead of liquid chemistry. The plasma process employs fluorine-containing precursors to generate reactive fluorine atoms that chemically react with silicon nitride, while ion acceleration provides the mechanical energy needed for etching without causing deformation through controlled ion bombardment rather than uncontrolled liquid flow
Solution Approach 2:
The patent changes the physical and chemical parameters of the etching process by using specific fluorine-containing precursors (SF6, CF4, C4F8) at controlled flow rates, pressures, and radio frequency powers. By adjusting these parameters, the process achieves high etch rates for silicon nitride while maintaining selectivity and preventing oxide deformation through optimized plasma conditions
2Length of moving object
If a dry plasma etch is used to penetrate constrained trenches, then trench penetration capability is improved, but substrate damage occurs through electric arc discharge
Solution Approach 1:
The patent introduces a remote plasma generation region as an intermediary between the plasma source and the substrate. The plasma is generated in a separate chamber or region and then transported to the substrate processing area, allowing the reactive species to reach the substrate without the harmful electric arc discharge that occurs in local plasma configurations. This intermediary approach maintains trench penetration capability while eliminating substrate damage
Solution Approach 2:
The patent extracts the plasma generation function from the substrate processing region by using a remote plasma source. The harmful electric arc discharge is separated from the substrate area, with only the beneficial reactive species being transported to etch the trenches. This extraction of the plasma generation step from the processing region eliminates substrate damage while maintaining etching effectiveness
3Manufacturing precision
If selective etching of silicon nitride is performed, then etch selectivity is improved, but isotropic etching capability is reduced
Solution Approach 1:
The patent achieves both high selectivity and isotropic etching by optimizing plasma process parameters including using specific fluorine-containing precursors, controlling radio frequency power at low levels (50-200 W), maintaining appropriate pressure (1-10 mTorr), and adjusting gas flow rates. These parameter changes create a plasma chemistry that preferentially reacts with silicon nitride while producing neutral radical species that etch isotropically rather than directionally
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 isotropic etching of silicon nitride with a selectivity greater than 20:1 relative to silicon oxide, reducing deformation and crosstalk, and allowing for precise control over etching operations in complex semiconductor structures.
Implementation Method 1
forming a plasma within the remote plasma region to generate plasma effluents of the fluorine-containing precursor
Implementation Method 2
Chemical etching is used for a variety of purposes including transferring a pattern in photoresist into underlying layers
Data Source
AI summary
Exemplary methods of etching a silicon-containing material may include flowing a fluorine-containing precursor into a remote plasma region of a semiconductor processing chamber. The methods may include forming a plasma within the remote plasma region to generate plasma effluents of the fluorine-containing precursor. The methods may include flowing the plasma effluents into a processing region of the semiconductor processing chamber. A substrate may be positioned within the processing region. The substrate may include a trench formed through stacked layers including alternating layers of silicon nitride and silicon oxide. The methods may include isotropically etching the layers of silicon nitride while substantially maintaining the silicon oxide.