Cryogenic Silicon Etching for Smooth High-Aspect-Ratio Sidewalls
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Solution Overview
Problem
Conventional etching processes face challenges in efficiently etching silicon-containing materials, particularly in 3D structures with high aspect ratios, often requiring multiple chambers and leading to sidewall roughness due to repeated passivation deposition and etching.
Innovation Solution
The use of cryogenic etching with specific etchant precursors, such as hydrogen fluoride (HF), nitrogen trifluoride (NF3), and sulfur hexafluoride (SF6), in a single semiconductor processing chamber to etch multiple layers of silicon-containing materials with reduced sidewall roughness and increased etch rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching processes are used to etch silicon-containing materials in 3D structures with high aspect ratios, then the etching can be performed, but multiple chambers are required and sidewall roughness occurs due to repeated passivation deposition and etching
Solution Approach 1:
The patent combines multiple etching functions into a single processing chamber. The system can perform sequential etching of different silicon-containing materials (such as silicon nitride and silicon oxide) without requiring transfer to another chamber, thereby reducing device complexity while maintaining manufacturing precision through controlled plasma parameters and cryogenic temperature operation
Solution Approach 2:
The patent employs cryogenic temperature operation and adjusts plasma parameters (power, pressure, gas composition) to achieve smooth sidewalls during etching. By changing the temperature parameter to cryogenic levels and optimizing plasma conditions, the process eliminates sidewall roughness that would otherwise require repeated passivation deposition cycles in conventional systems
2Manufacturing precision
If wet HF etching is used to remove silicon oxide, then selective etching of silicon oxide over other dielectrics is achieved, but the process cannot penetrate constrained trenches and may deform remaining material
Solution Approach 1:
The patent replaces wet chemical etching with plasma-based etching processes. The plasma etching mechanism uses reactive species and ion bombardment to achieve anisotropic etching that can penetrate deep, constrained trenches while maintaining material selectivity through careful control of plasma composition and processing parameters, avoiding the deformation issues associated with wet etching
3Manufacturing precision
If local plasma is used to etch constrained trenches, then better penetration and less deformation are achieved, but substrate damage occurs through electric arcs
Solution Approach 1:
The patent employs cryogenic temperature operation as an inert-like environment that suppresses harmful electric arc formation. The low temperature conditions stabilize the plasma discharge, preventing substrate damage from electric arcs while maintaining the ability to penetrate constrained trenches with controlled plasma etching
Solution Approach 2:
The patent changes the temperature parameter to cryogenic levels and adjusts plasma power and pressure parameters to achieve stable, damage-free etching. These parameter changes allow the system to maintain plasma reactivity for trench penetration while suppressing the formation of harmful electric arcs that would damage the substrate
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 allows for efficient etching of multiple silicon-containing layers with improved uniformity and reduced sidewall roughness, enhancing throughput by eliminating the need for multiple chambers and reducing surface deformation.
Implementation Method 1
forming plasma effluents of the etchant precursor
Implementation Method 2
The processing region may be maintained at a cryogenic temperature while contacting the substrate with the plasma effluents of the etchant precursor
Data Source
AI summary
Exemplary semiconductor processing methods may include providing an etchant precursor to a processing region of a semiconductor processing chamber. A substrate may be disposed within the processing region. The substrate may include a layer of a silicon-containing material. The silicon-containing material may be a silicon-and-carbon-containing material, a silicon-carbon-and-nitrogen-containing material, a silicon-and-nitrogen-containing material, a silicon-and-oxygen-containing material, or silicon material. The methods may include forming plasma effluents of the etchant precursor. The methods may include contacting the substrate with the plasma effluents of the etchant precursor. The contacting may etch a portion of the layer of the silicon-containing material. The processing region may be maintained at a cryogenic temperature while contacting the substrate with the plasma effluents of the etchant precursor.