Plasma Etching Chemistry for Selective Deep Silicon Features
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Solution Overview
Problem
Existing etch processes for semiconductor processing face challenges in achieving high selectivity and minimal deformation of features, especially in constrained trenches, while avoiding damage to substrates due to electric arcs in local plasmas.
Innovation Solution
The method involves forming plasma effluents from a combination of precursors, including a silicon-and-fluorine-containing precursor like silicon tetrafluoride, an etchant precursor, and an oxygen-containing precursor, which are used to etch silicon-containing materials with high selectivity relative to mask materials, while simultaneously etching the mask and depositing a silicon-and-oxygen-containing material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If wet HF etch is used to preferentially remove silicon oxide, then etch selectivity is improved, but penetration into constrained trenches is poor and material deformation occurs
Solution Approach 1:
The patent replaces wet chemical etching with plasma-based etching processes. Specifically, it uses a combination of fluorocarbon-based plasma (for sidewall passivation and anisotropic etching) and oxygen plasma (for silicon oxide removal). This substitution allows the process to achieve both high selectivity and effective penetration into constrained trenches by utilizing plasma's ability to deliver reactive species directly to the etch front without liquid flow limitations.
Solution Approach 2:
The patent employs a composite plasma chemistry approach, combining multiple plasma components (fluorocarbon and oxygen plasmas) to achieve functions that neither component could accomplish alone. The fluorocarbon provides sidewall protection and directional etching, while oxygen provides selective silicon oxide removal, creating a synergistic effect that resolves the contradiction between selectivity and penetration.
2Volume of moving object
If local plasma is used to penetrate constrained trenches, then penetration capability is improved, but substrate damage occurs due to electric arcs
Solution Approach 1:
The patent carefully controls plasma process parameters including pressure (maintained at low levels to prevent arc formation), power density, gas flow rates, and temperature. By optimizing these parameters, the process achieves sufficient ion energy for trench penetration while preventing the formation of damaging electric arcs on the substrate surface.
Solution Approach 2:
The patent introduces fluorocarbon-based plasma as an intermediary that forms protective sidewall polymers and passivation layers. This intermediary layer protects the substrate and mask materials from direct exposure to high-energy ions, enabling trench penetration without substrate damage from electric arcs.
3Volume of moving object
If plasma etching is used to etch silicon-containing material, then penetration into constrained trenches is improved, but mask material damage and feature deformation occur
Solution Approach 1:
The patent applies different plasma chemistries to different spatial locations and functions: fluorocarbon plasma is used for sidewall passivation and anisotropic etching where mask protection is needed, while oxygen plasma is used selectively for silicon oxide removal where mask damage is minimized. This spatial and functional differentiation of plasma properties protects mask material integrity while achieving penetration.
Solution Approach 2:
The patent employs a cyclic or alternating plasma process sequence, switching between fluorocarbon-based plasma (for sidewall protection and directional etching) and oxygen plasma (for silicon oxide removal). This periodic application of different plasma types allows the mask to be protected during critical phases while still achieving the required etch penetration.
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 enhances the formation and deepening of features in semiconductor structures with minimal change in mask thickness, achieving high selectivity and reducing the risk of feature clogging and substrate damage.
Implementation Method 1
forming plasma effluents of a plurality of precursors... The plasma effluents may then contact a silicon-containing material and a mask material on a substrate
Implementation Method 2
Contacting the silicon-containing material and the mask material with the plasma effluents may cause (i) etching the silicon-containing material with the plasma effluents
Implementation Method 3
depositing a silicon-and-oxygen-containing material on the mask material with the plasma effluents
Implementation Method 4
simultaneously etching the mask material and depositing a silicon-and-oxygen-containing material on the mask material
Data Source
AI summary
Methods of semiconductor processing may include forming plasma effluents of a plurality of precursors (e.g., an etchant precursor, an oxygen-containing precursor, and a silicon-and-fluorine-containing precursor like silicon tetrafluoride). The plasma effluents may then contact a silicon-containing material and a mask material on a substrate in a processing region of a semiconductor processing chamber. The mask material may have one or more apertures therein that allow the plasma effluents access to the silicon-containing material. Contacting the silicon-containing material and the mask material with the plasma effluents may cause (i) etching the silicon-containing material with the plasma effluents to form and/or deepen one or more features in the silicon-containing material and (ii) simultaneously etching the mask material and depositing a silicon-and-oxygen-containing material on the mask material with the plasma effluents.