Silicon Etching Plasma Chemistry for High-Aspect-Ratio Features
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Solution Overview
Problem
Conventional etching processes face challenges in high aspect ratio structures, such as reduced etch rates, clogging, bowing, bending, and imbalances between oxide and nitride etch rates, particularly in 3D NAND memory structures where aspect ratios are high and etchant species may not reach the etch front effectively.
Innovation Solution
The use of a combination of hydrogen-containing and fluorine-containing precursors, such as diatomic hydrogen and nitrogen trifluoride, with a bias power applied to the substrate, to increase etch rates and maintain directionality, along with co-reactants like boron or phosphorous-containing precursors, to enhance etching through alternating layers of silicon-containing materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional etching processes are used for high aspect ratio structures, then the etching can be performed with standard equipment, but the etch rate decreases and clogging occurs
Solution Approach 1:
The patent changes the chemical parameters of the etching process by using a dual-precursor plasma system (silane and sulfur hexafluoride) instead of conventional single-precursor chemistries. This parameter change enables significantly higher etch rates while maintaining anisotropic etching and preventing clogging in high aspect ratio structures through controlled volatile byproduct formation and removal
Solution Approach 2:
The patent employs a composite etching chemistry approach by combining silane (SiH4) and sulfur hexafluoride (SF6) precursors in plasma. This composite chemical system produces synergistic effects where silane provides silicon-containing etch species for high etch rates while SF6 provides fluorine for selective etching and volatile byproduct formation, resolving the contradiction between etch rate and etch uniformity
2Manufacturing precision
If local plasma is used to penetrate constrained trenches, then the etching can reach deep features, but substrate damage occurs through electric arcs
Solution Approach 1:
The patent changes the plasma generation parameters by using inductively coupled plasma with specific power density and gas flow parameters. This creates a non-local plasma field that penetrates constrained trenches effectively while controlling the plasma chemistry to prevent electric arc formation and substrate damage through optimized silane-SF6 reaction dynamics
3Productivity
If wet etching is used to remove silicon oxide, then the etching is selective and fast, but the process cannot penetrate constrained trenches and deforms remaining material
Solution Approach 1:
The patent replaces wet chemical etching with a plasma-based chemical vapor deposition etching process. This substitution maintains the selective etching capability and high etch speed of wet processes while adding the advantages of plasma etching: ability to penetrate constrained trenches through directional ion bombardment and absence of liquid handling issues that cause material deformation
Solution Approach 2:
The patent uses a composite plasma chemistry system combining silane and sulfur hexafluoride precursors to achieve etching performance that combines the selectivity and speed of wet etching with the trench-penetration capability of dry plasma etching, while preventing material deformation through controlled volatile byproduct removal
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 significantly increases etch rates, prevents etch rate slowdown, and ensures anisotropic etching, reducing issues like bowing, bending, and clogging, while maintaining uniformity and directionality, even in high aspect ratio features.
Implementation Method 1
forming plasma effluents of the hydrogen-containing precursor and 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
Implementation Method 3
applying a bias power to the substrate support during the contacting. A voltage of the bias power may be greater than or about 500 V
Data Source
AI summary
Exemplary methods of semiconductor processing may include providing a hydrogen-containing precursor and a fluorine-containing precursor to a processing region of a semiconductor processing chamber. A substrate may be disposed on a substrate support within the processing region. One or more layers of silicon-containing material may be disposed on the substrate. The methods may include forming plasma effluents of the hydrogen-containing precursor and the fluorine-containing precursor. The methods may include contacting one or more layers of silicon-containing material with plasma effluents of the hydrogen-containing precursor and the fluorine-containing precursor. The contacting may etch a portion of the one or more layers of silicon-containing material.