Selective Tungsten Etching via Oxygen-Rich Plasma
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Solution Overview
Problem
Existing methods fail to achieve selective etching of tungsten containing layers during semiconductor wafer processing, particularly in distinguishing tungsten from silicon, silicon oxide, silicon oxynitride, or titanium nitride, resulting in inadequate selectivity.
Innovation Solution
A method involving an etch gas comprising O2, N2, and a fluorine containing component, with a plasma formed from this gas, is used to selectively etch tungsten layers, maintaining a chamber pressure of at least 60 mTorr and a bias of 100 to 400 volts to achieve high aspect ratio features with selective etching of tungsten over silicon oxide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching methods are used, then etching can be performed, but selective etching of tungsten over silicon oxide, silicon nitride, and other materials cannot be achieved
Solution Approach 1:
The patent changes the chemical parameters of the etching process by using a specific gas composition (CHF3, CF4, O2, N2) where oxygen and nitrogen atoms are present in at least as great amounts as fluorine atoms. This parameter change enables selective tungsten etching while protecting other materials, resolving the contradiction between achieving selectivity and maintaining process capability
Solution Approach 2:
The patent employs a composite etching plasma environment formed from multiple gas components (CHF3, CF4, O2, N2) that work together to achieve selective etching. The combination of fluorine-containing compounds for etching capability with oxygen and nitrogen for selectivity control creates a composite chemical environment that simultaneously enables etching and provides material discrimination
2Manufacturing precision
If high aspect ratio features are etched, then feature precision is improved, but process complexity increases
Solution Approach 1:
The patent optimizes specific process parameters including chamber pressure (at least 60 mTorr) and bias voltage (100-400 volts) to enable high aspect ratio etching. These parameter changes allow precise control of feature geometry while managing the complexity of the etching process through defined operating conditions
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 enables selective etching of tungsten layers with high aspect ratios and improved selectivity over silicon oxide, allowing for the formation of semiconductor devices with precise tungsten features while minimizing etching of other materials, such as silicon and nitride layers.
Implementation Method 1
A plasma is formed from the etch gas. The tungsten containing layer is etched with the plasma formed from the etch gas.
Implementation Method 2
An etch gas is provided comprising O2 and a fluorine containing component... The tungsten containing layer is etched with the plasma formed from the etch gas
Data Source
AI summary
A method for etching a tungsten containing layer is provided. An etch gas is provided comprising O2 and a fluorine containing component, wherein the etch gas has at least as many oxygen atoms as fluorine atoms. A plasma is formed from the etch gas. The tungsten containing layer is etched with the plasma formed from the etch gas.