Low-Temperature Plasma Etching of Silicon-Oxygen Features
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Solution Overview
Problem
Conventional etching processes struggle to maintain uniform critical dimensions and prevent bowing, bending, or twisting of features in high-aspect-ratio structures, especially when etching silicon-and-oxygen-containing materials.
Innovation Solution
The use of a combination of fluorine-containing and hydrogen-containing precursors in a semiconductor processing chamber, forming a hydrogen fluoride (HF)-containing plasma, while maintaining a substrate support pedestal temperature below -20°C, to etch features with critical dimensions less than 30 nm and aspect ratios greater than 5:1.
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 a plasma-based process that uses ion bombardment and reactive species to achieve trench penetration while maintaining selectivity through controlled chemistry and physical effects
Solution Approach 2:
The patent changes the physical state from liquid to plasma and controls temperature, pressure, and composition parameters to achieve both penetration and selectivity that wet etching cannot provide
2Ease of operation
If local plasma is used to penetrate constrained trenches, then penetration capability is improved, but substrate damage occurs through electric arcs
Solution Approach 1:
The patent uses fluorocarbon-based plasma chemistry that forms protective carbonaceous films on substrate surfaces, preventing direct plasma damage and electric arc formation while maintaining effective etching
Solution Approach 2:
The patent introduces fluorocarbon species as intermediaries that mediate between the plasma and substrate, providing both etching functionality and protective effects to prevent substrate damage
3Ease of manufacture
If room temperature processing is used, then process simplicity is maintained, but feature profile uniformity and bowing control are poor
Solution Approach 1:
The patent changes the temperature parameter to cryogenic conditions, which fundamentally alters the plasma chemistry and surface reactions to achieve superior profile control and uniformity that cannot be obtained at room temperature
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 uniformity of feature profiles, prevents etch rate slowdown, and reduces the occurrence of bowing, bending, or twisting, while maintaining high etch rates and selectivity.
Implementation Method 1
forming plasma effluents of the fluorine-containing precursor and the hydrogen-containing precursor
Implementation Method 2
Chemical etching is used for a variety of purposes including transferring a pattern in photoresist into underlying layers
Implementation Method 3
A substrate support pedestal temperature may be maintained at less than or about −20° C. during the semiconductor processing method
Data Source
AI summary
Exemplary semiconductor processing methods may include providing a fluorine-containing precursor and a hydrogen-containing precursor to a processing region of a semiconductor processing chamber. A substrate may be housed in the processing region. A layer of a silicon-containing material may be disposed on the substrate. The methods may include forming plasma effluents of the fluorine-containing precursor and the hydrogen-containing precursor. The methods may include contacting the substrate with the plasma effluents of the fluorine-containing precursor and the hydrogen-containing precursor. The contacting may etch a feature in the layer of silicon-containing material. A substrate support pedestal temperature may be maintained at less than or about −20° C. during the semiconductor processing method.