Ultra-Thin Nitride Barrier Layer PVD Process
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Solution Overview
Problem
Conventional physical vapor deposition (PVD) methods struggle to consistently produce metal nitride barrier layers thinner than 1 nm, which are necessary for modern semiconductor fabrication, due to limitations in nitrogen flow control, leading to inconsistent properties and higher resistance, especially in dual-layer processes.
Innovation Solution
A modified PVD process that forms an ultra-thin nitrided metallization layer followed by a pure metallization layer using a single ignition step by cutting off nitrogen gas flow before or during the ignition phase, allowing for controlled nitride layer thickness and eliminating the need for multiple gas flushes and plasma re-ignition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional PVD sputtering is used to deposit metal nitride barrier layers, then the process is relatively simple and cost-effective, but it is difficult to consistently produce layers thinner than 2 nm in thickness with controlled nitrogen incorporation
Solution Approach 1:
The patent applies preliminary action by pre-flushing the chamber with nitrogen gas before the sputtering deposition begins. This preliminary nitrogen exposure ensures that when the metal nitride layer is deposited, there is sufficient nitrogen already present in the chamber to achieve consistent sub-2 nm thickness with controlled nitrogen incorporation, resolving the reliability issue of conventional PVD processes.
Solution Approach 2:
The patent employs dynamics by implementing a multi-stage gas flow control strategy during the sputtering process. The nitrogen gas flow is dynamically adjusted: initially flushed into the chamber, then maintained at specific levels during deposition, and finally stopped at precisely timed intervals. This dynamic control enables consistent production of ultra-thin nitride layers with thicknesses below 2 nm while maintaining reliable nitrogen incorporation.
2Reliability
If the nitrogen content of the metal nitride barrier layer is increased to prevent copper diffusion and electromigration, then diffusion protection improves, but the layer becomes more resistive leading to slower signal propagation
Solution Approach 1:
The patent applies parameter changes by precisely controlling the nitrogen gas flow rate and timing during the sputtering process. By adjusting these parameters, the nitrogen content in the deposited metal nitride layer is optimized to provide sufficient diffusion protection against copper while maintaining lower electrical resistance. The nitrogen flow is stopped at specific intervals during deposition to achieve the optimal balance between barrier performance and conductivity.
3Object-generated harmful factors
If the thickness of the metal nitride barrier layer is reduced to lower resistance and improve signal propagation, then electrical performance improves, but the layer becomes less effective at preventing copper diffusion and electromigration
Solution Approach 1:
The patent employs parameter changes by optimizing the nitrogen gas flow timing and sputtering power settings to produce ultra-thin nitride layers (below 2 nm) that maintain high barrier effectiveness. The nitrogen flow is precisely controlled to achieve the minimum necessary thickness for diffusion protection while minimizing resistance. Quality control measurements are performed to ensure the deposited layers meet both thickness and barrier performance specifications.
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 the reliable production of ultra-thin nitride barrier layers less than 1 nm thick, improving adhesion, reducing resistance, and enhancing the reliability of copper interconnects while maintaining cost-effectiveness and process control, thus addressing the challenges of miniaturization in semiconductor fabrication.
Implementation Method 1
Deposition through sputtering is accomplished in an enclosed chamber, with a target electrode composed of at least part of the material to be sputter deposited and a substrate. A noble non-reactive gas such as argon is streamed through the chamber and is ignited to provide a plasma source. Sputtered particles traverse the chamber and stick to the substrate, forming a metal layer.
Implementation Method 2
A noble non-reactive gas such as argon is streamed through the chamber and is ignited to provide a plasma source. Sputtered particles chemically react with the reactive gas and are together deposited on the substrate as the compound material.
Data Source
AI summary
Devices and methods are presented to fabricate diffusion barrier layers on a substrate. Presently, barrier layers comprising a nitride layer and a pure metal layer are formed using a physical vapor deposition (PVD) process that requires multiple ignition steps, and results in nitride-layer thicknesses of no less than 2 nm. This invention discloses devices and process to produce nitride-layers of less than <1 nm, while allowing for formation of a pure metal layer on the nitride-layer without re-igniting the plasma. To achieve this, the flow of nitrogen gas is cut off either before the plasma is ignited, or before the formation of a continuous-flow plasma. This ensures that a limited number of nitrogen atoms is deposited in conjunction with metal atoms on the substrate, thereby allowing for controlled thickness of the nitride layer.