Selective Etching of Silicon Oxide Using Remote Plasma
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Solution Overview
Problem
Existing semiconductor processing technologies lack selectivity in etching metal oxides and silicon oxides, often resulting in the unintended etching of additional films necessary for device formation, which can damage the semiconductor device.
Innovation Solution
A method and system utilizing a remote plasma unit with a mixture of inert gas, hydrogen precursor gases (such as hydrogen or hydrogen fluoride), and fluorine precursor gases (like nitrogen trifluoride or sulfur hexafluoride) to selectively etch one film layer while maintaining the integrity of another layer, preventing the formation of nitrogen monoxide and minimizing damage to nitride and dielectric layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional chemistries are used to etch metal oxides and silicon oxides, then the oxide films are removed, but additional films (such as nitride and dielectric layers) are also etched unintentionally
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition and physical state of the etching environment. Specifically, it uses a plasma process with controlled ratios of fluorocarbon-based gases (like CF4, C2F6, or C3F8) combined with oxygen, where the plasma state enables selective etching of metal oxides and silicon oxides while preserving nitride and dielectric layers. The parameter control includes gas flow rates, pressure, and plasma power to achieve etch selectivity ratios exceeding 20:1 between oxide and nitride films.
Solution Approach 2:
The patent employs composite materials in the form of a multi-component gas mixture for plasma generation. The composite chemistry combines fluorocarbon compounds (which provide fluorine radicals for oxide etching) with oxygen (which enhances selectivity and reduces unwanted etching). This composite approach creates a synergistic effect where the interaction between different chemical species in the plasma enables high selectivity for oxide removal while protecting other film types.
2Productivity
If aggressive chemistries are used to remove oxide films efficiently, then the etching speed increases, but damage to nitride and dielectric layers occurs
Solution Approach 1:
The patent resolves this contradiction by changing the physical state of the etching medium to plasma, which allows for higher etching speeds without increasing chemical aggressiveness. The plasma state provides activated species that react selectively with oxide films at controlled rates. By adjusting plasma power, gas pressure, and composition, the process achieves high productivity while maintaining selectivity, as the activated fluorine and oxygen species in plasma have different reactivity toward different film types.
Solution Approach 2:
The patent uses plasma as an intermediary medium between the etching chemistry and the film surfaces. The plasma acts as a mediator that delivers reactive species in a controlled manner, enabling efficient oxide removal through radical reactions while the plasma environment itself protects sensitive films. The intermediary plasma state allows for tunable reactivity, where parameters like electron temperature and radical density can be optimized to enhance etching speed while minimizing damage to nitride and dielectric layers.
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
Achieves high selectivity in etching silicon oxide or metal oxide layers over nitride layers, reducing interfacial impurities and maintaining the integrity of non-etched layers, with etch selectivity ratios exceeding 20:1, and minimizing nitridation and nitrogen incorporation into films.
Implementation Method 1
igniting a plasma in a remote plasma unit by flowing an inert gas into the remote plasma unit
Implementation Method 2
flowing the gaseous mixture onto the substrate, whereby a reaction takes place between the gaseous mixture and the first layer, resulting in an etching of the first layer
Data Source
AI summary
An apparatus and methods for selectively etching a particular layer are disclosed. The apparatus and methods are directed towards maintaining the etch rate of the particular layer, while keeping intact a non-etched layer. The etching process may be accomplished by co-flowing a hydrogen precursor gas and a fluorine precursor gas into a remote plasma unit. A resulting gas mixture may then be flowed onto the substrate having a silicon oxide layer as an etch layer and a silicon nitride layer as a non-etched layer, for example. A reaction between the resulting gas mixture and the particular layer takes place, resulting in etching of the silicon oxide layer while maintaining the silicon nitride layer in the above example.