Gate Stack Vt Tuning Layers Protected From Halide Etching
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Solution Overview
Problem
Metal oxide layers used for threshold voltage tuning in semiconductor devices are susceptible to etching by halide-containing reactants during the deposition of metal nitride layers, leading to reduced process control and challenges in fabricating multi-Vt layer structures.
Innovation Solution
A protective layer is formed directly over the metal oxide threshold voltage tuning layer, which is then followed by the deposition of a metal nitride layer using a metal halide reactant. This protective layer can be an etch-resistant metal oxide layer or a nitrided layer formed by post-deposition nitridation of the metal oxide layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal oxide layer is deposited on high-k material for threshold voltage tuning, then the electrical requirements of multi-Vt layer structures are met, but the metal oxide layer is etched by halide containing reactants during metal nitride deposition
Solution Approach 1:
A protective layer is introduced as an intermediary between the metal oxide Vt tuning layer and the metal halide reactant. This protective layer acts as a mediator that allows the metal halide to deposit the metal nitride layer while preventing direct contact and etching of the metal oxide layer, thus resolving the contradiction between maintaining Vt tuning capability and preventing etching damage
Solution Approach 2:
The protective layer is deposited in advance before the metal nitride deposition process. This preliminary protective action prevents the harmful etching effect from occurring during subsequent processing steps, allowing the metal oxide layer to maintain its integrity while still enabling threshold voltage tuning functionality
2Manufacturing precision
If a protective layer is deposited over the metal oxide layer to prevent etching, then etching control is improved, but the device structure becomes more complex
Solution Approach 1:
The protective layer is designed with optimized thickness parameters (typically 1-10 nm) and specific material composition that balance its protective function with minimal impact on device structure. By carefully controlling these parameters, the layer provides sufficient etching protection while maintaining overall structural simplicity and compatibility with existing device architectures
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 protective layer effectively reduces the etching of the threshold voltage tuning metal oxide layer during the deposition of the overlying metal nitride layer, thereby improving process control and enabling the fabrication of reliable multi-Vt layer structures.
Implementation Method 1
the first metal oxide layer is treated with a nitrogen reactant... the etch protective layer is a portion of the metal oxide in which nitrogen is incorporated
Implementation Method 2
depositing a metal nitride layer using a metal halide reactant... the metal nitride layer is formed by contacting a substrate with a first metal halide reactant
Data Source
AI summary
Threshold voltage (Vt) tuning layers may be sensitive to etching by reactants used to deposit overlying gate material, such as metal nitride. Methods for depositing Vt tuning layers are provided. In some embodiments Vt tuning layers may comprise a Vt tuning material in a neutral matrix. In some embodiments, processes for reducing or eliminating the etching of Vt tuning layers by halide reactants are described. In some embodiments a Vt tuning layer, such as a metal oxide layer, is treated by a nitridation process following deposition and prior to subsequent deposition of a metal nitride capping layer. In some embodiments an etch-protective layer, such as a NbO layer, is deposited over a Vt tuning layer prior to deposition of an overlying metal nitride layer.