Halogen Abatement for High Aspect Ratio EPI Growth
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional halogen abatement techniques for substrates with high aspect ratio features are ineffective or damaging to the etch profile, as they either fail to remove halogen residues and byproducts sufficiently or cause oxidation, leading to corrosion and profile damage.
Innovation Solution
A mild post-etch treatment method using a combination of mild fluorine-based plasma and nonreactive gas plasma is applied sequentially or in mixture to remove halogen residues and byproducts without damaging the etch profile, employing a fluorine-containing gas like NF3 and a nonreactive gas like Ar, with controlled source and bias powers to maintain the substrate temperature between 0°C and 200°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional O2 based post-etch treatment is used for halogen abatement, then halogen residues are removed from the substrate surface, but the silicon surface is oxidized which hinders epitaxial growth
Solution Approach 1:
The patent introduces a fluorine-containing plasma as an intermediary substance to remove halogen residues without directly oxidizing the silicon surface. The fluorine plasma reacts with halogen residues to form volatile fluorinated compounds that can be easily removed, serving as a mediator between the halogen contamination and the silicon surface without causing oxidative damage.
Solution Approach 2:
The patent changes the chemical composition parameter of the plasma from oxygen-based to fluorine-based, fundamentally altering the reaction chemistry. This parameter change allows the plasma to remove halogen residues through fluorination reactions rather than oxidation reactions, thereby eliminating the harmful oxidation effect on the silicon surface while maintaining effective halogen abatement.
2Object-generated harmful factors
If aggressive fluorine-based PET is used to achieve >99% halogen abatement, then halogen residues are effectively removed, but the memory hole sidewall etch profile is significantly impacted
Solution Approach 1:
The patent applies partial action by using mild fluorine-based PET conditions with controlled, lower doses of fluorine-containing gas and moderate RF power. This partial application is sufficient to remove the majority of halogen residues (>98% abatement) without the excessive action that would cause significant damage to the sidewall etch profile. The process stops before complete halogen removal would be achieved by aggressive methods, accepting a small residual amount to preserve structural integrity.
Solution Approach 2:
The patent modifies the process parameters of fluorine-based PET by reducing the flow rate of fluorine-containing gas and lowering the RF power compared to aggressive conditions. This parameter optimization achieves the optimal balance between halogen removal efficiency and sidewall profile preservation, demonstrating that milder parameters can achieve sufficient abatement without the harmful effects of aggressive processing.
3Object-generated harmful factors
If H2 based PET or high temperature baking is used for halogen abatement, then some halogen removal is achieved, but the effectiveness is insufficient for high aspect ratio applications
Solution Approach 1:
The patent changes the chemical nature of the plasma from hydrogen-based to fluorine-based, fundamentally improving the chemical affinity for halogen removal. Fluorine has a higher electronegativity and forms more volatile compounds with halogens compared to hydrogen, significantly enhancing the abatement effectiveness. This parameter change in chemical composition makes the process reliable for high aspect ratio applications where conventional methods fail.
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 method achieves >98% halogen removal from the substrate surface without impacting the etch profile, reducing outgassing and byproduct accumulation, and maintaining chamber stability, as demonstrated by ion chromatography measurements.
Implementation Method 1
forming and maintaining a plasma of the first process gas or a plasma of the mixture of the first process gas and the second process gas in the etch chamber to remove the residue from the surface
Implementation Method 2
exposing the substrate to the first process gas or to the mixture of the first process gas and the second process gas, the substrate having halogen residue formed on an exposed surface
Implementation Method 3
forming and maintaining a plasma of the second process gas in the etch chamber to remove the residue from the surface by applying a second source power and a bias power
Data Source
AI summary
In an embodiment, a method of processing a substrate includes introducing a first process gas or a mixture of the first process gas and a second process gas into an etch chamber; exposing the substrate to the first process gas or to the mixture of the first and second process gases, the substrate having halogen residue formed on an exposed surface, the substrate having high aspect ratio features; forming and maintaining a plasma of the first process gas or a plasma of the mixture of the first and second process gases in the etch chamber to remove the residue from the surface by applying a first source power; exposing the substrate to the second process gas; and forming and maintaining a plasma of the second process gas in the etch chamber to remove the residue from the surface by applying a second source power and a bias power.