Tungsten Conductive Layer Structure for Residual Fluorine Removal
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Solution Overview
Problem
In semiconductor device manufacturing, the use of film formation technologies like CVD and ALD can result in residual fluorine in metal layers, leading to potential failures such as leakage due to incomplete removal of fluorine compounds.
Innovation Solution
A semiconductor device structure is developed with a barrier metal layer and a conductive layer comprising a first metal layer and a second metal layer, where the second metal layer includes an impurity that bonds with tungsten to remove fluorine, using ALD processes with specific gas introductions to ensure uniform impurity concentration and effective fluorine removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If film formation technologies like CVD and ALD are used to form metal layers, then the lines (contact plugs, via plugs, word lines) can be formed, but residual fluorine remains in the metal layers causing leakage failures
Solution Approach 1:
The conductive layer is divided into a first metal layer and a second metal layer. The first metal layer is formed using standard ALD processes, while the second metal layer is formed by introducing material gas and additive gas alternately. This segmentation allows the fluorine removal function to be separated from the metal deposition function, enabling each layer to have specialized purposes.
Solution Approach 2:
An additive gas containing impurity (such as carbon-containing gas or oxygen-containing gas) is introduced as an intermediary substance during the formation of the second metal layer. This additive gas facilitates the removal of fluorine from the metal layer by reacting with it to form volatile compounds (CF4, COF2, CO2), thereby eliminating the harmful fluorine residues without compromising the metal layer formation.
2Ease of manufacture
If reducing gas including hydrogen is used in ALD processes, then metal layers can be formed, but fluorine compounds remain residual causing potential failures
Solution Approach 1:
The ALD process is made continuous by alternately introducing material gas (tungsten hexafluoride) and additive gas (containing impurity for fluorine removal) without interrupting the deposition process. This continuous action ensures that metal deposition and fluorine removal occur simultaneously throughout the layer formation, preventing fluorine accumulation while maintaining manufacturing efficiency.
Solution Approach 2:
The composition of the gas phase is dynamically changed during the ALD process by alternating between material gas and additive gas. The additive gas introduces impurity elements (carbon, oxygen) that change the chemical environment within the metal layer, enabling fluorine to be converted from a harmful residual to a removable compound through parameter changes in gas composition and reaction 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
The solution effectively reduces fluorine-related failures in semiconductor devices by ensuring minimal residual fluorine in the metal layers, improving the reliability of the thermal process and specific resistance of the metal layers.
Implementation Method 1
the second metal layer includes an impurity configured to remove fluorine bonded to the metal
Implementation Method 2
In these film formation technologies, the lines are formed, for example, by alternately introducing material gas including fluorine and metal, such as tungsten hexafluoride (WF6), and reducing gas including hydrogen (H2)
Data Source
AI summary
A semiconductor device according to an embodiment includes: a barrier metal layer provided on a surface of an insulating layer; and a conductive layer having a first metal layer provided on a surface of the barrier metal layer, and a second metal layer provided on a surface of the first metal layer. The second metal layer includes an identical metal to metal of the first metal layer, and an impurity configured to remove fluorine bonded to the metal.