TiSiN Coating via ALD Gradient for Diffusion Barrier
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Solution Overview
Problem
Existing methods for depositing TiSiN layers as diffusion barriers in electronic components face a trade-off between increased diffusion resistance and electrical conductivity, where higher silicon content improves diffusion resistance but increases electrical resistance, making the layer unsuitable as a contact layer.
Innovation Solution
The method involves a three-step ALD process where TiN is initially deposited, followed by an N-free Ti and Si layer sequence, and finally TiSiN, with each step repeated multiple times to form regions with Ti-N bonds, Si-Si bonds, and TiSi2, optimizing diffusion resistance and electrical conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the silicon content in the TiSiN layer is increased to improve diffusion resistance, then the diffusion barrier properties are enhanced, but the electrical resistance of the deposited layer increases, making it unsuitable as a contact layer
Solution Approach 1:
The patent applies local quality by creating a TiSiN layer with non-uniform nitrogen distribution, where the nitrogen concentration varies through the layer thickness. The method deposits the layer in multiple passes with different nitrogen exposure conditions, resulting in a gradient structure where regions closer to the substrate have higher nitrogen content (better diffusion barrier) while regions closer to the surface have lower nitrogen content (better conductivity).
Solution Approach 2:
The patent employs periodic action by depositing the TiSiN layer in multiple alternating cycles of titanium deposition and nitrogen exposure. Each cycle consists of introducing titanium-containing reaction gas, then introducing nitrogen-containing reaction gas, and repeating this sequence n times. This periodic deposition creates the desired nitrogen concentration gradient through controlled temporal variation in nitrogen exposure.
2Reliability
If a TiN layer is deposited first followed by SiN layer to form TiSiN, then the diffusion barrier is improved, but the electrical conductivity deteriorates due to increased silicon content
Solution Approach 1:
The patent applies parameter changes by systematically varying the nitrogen exposure parameters during the deposition process. Specifically, it controls the number of deposition cycles (n), the deposition temperature, and the relative amounts of titanium and nitrogen reaction gases introduced in each cycle. By adjusting these parameters, the method optimizes the nitrogen concentration gradient to simultaneously achieve good diffusion barrier properties and electrical conductivity.
Solution Approach 2:
The patent creates a composite structure within the TiSiN layer by forming a nitrogen concentration gradient that results in different local compositions. The layer effectively becomes a composite of regions with different Ti:N ratios, where the bottom regions are more TiN-rich (better diffusion barrier) and the top regions are more TiSi-rich (better conductivity), combining the advantages of both material compositions.
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 results in a TiSiN coating with enhanced diffusion barrier properties and lower electrical resistance, suitable for use as a contact layer in electronic components, maintaining high conductivity while preventing contact metal diffusion into silicon layers.
Implementation Method 1
The deposition process takes place at elevated temperatures at which a chemical reaction takes place on the substrate surface; in particular a decomposition reaction of the reaction gas may take place on the substrate surface.
Implementation Method 2
In a subsequent Flush or purge step, the residues of the process gas are removed from the process chamber and the same reaction gas or another reaction gas is introduced into the process chamber.
Data Source
AI summary
A method for ALD coating of a substrate with a layer containing Ti, Si, N, wherein a reaction gas and then a flushing gas are introduced into a process chamber holding the substrate in a plurality of successive steps, each in one or more cycles, wherein TiN is deposited in a first step with a reaction gas containing Ti and a reaction gas containing N, TiSi is deposited in a second step with a reaction gas containing Ti and a reaction gas containing Si, and in a third step following the second step, TiSiN is deposited with a reaction gas containing Ti, with a reaction gas containing N and with a reaction gas containing Si.