Tungsten Film Stack Without TiN for Low-Resistance Interconnects
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Solution Overview
Problem
Conventional tungsten deposition processes result in high resistivity issues due to the high resistivity of titanium nitride (TiN) layers and challenges in reducing the resistivity of bulk CVD tungsten, especially with increasing aspect ratios and smaller feature sizes, leading to unacceptably high line resistance or via contact resistance in integrated circuits.
Innovation Solution
A method involving the formation of a tungsten stack on a substrate using a physical vapor deposition (PVD) tungsten liner layer with controlled grain size greater than 100 Ångstroms, followed by a chemical vapor deposition (CVD) tungsten film, eliminating the need for a TiN layer and nucleation layer, and potentially using Kr as a process gas to enhance properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a TiN layer is used as barrier and liner layer followed by bulk CVD tungsten deposition, then the deposition process is conventional and well-established, but the resistivity of the tungsten film stack becomes unacceptably high
Solution Approach 1:
The patent removes the TiN barrier/liner layer from the conventional deposition structure and replaces it with a PVD tungsten liner layer. This extraction of the problematic high-resistivity TiN layer directly addresses the resistivity issue while maintaining the essential barrier and liner functions through the PVD tungsten layer alone.
Solution Approach 2:
The patent changes the deposition method from CVD to PVD for the liner layer, and controls the grain size parameter to be greater than 100 Ångstroms. This parameter change in the deposition process and grain size control reduces the resistivity of the tungsten film stack while maintaining conventional process feasibility.
2Productivity
If aspect ratio increases and feature sizes decrease, then device integration density improves, but line resistance and via contact resistance become unacceptably high
Solution Approach 1:
The patent changes the deposition process from CVD to PVD and controls grain size to greater than 100 Ångstroms, which reduces resistivity and enables acceptable line resistance even as aspect ratios increase and feature sizes decrease, thereby supporting higher integration density.
Solution Approach 2:
The patent creates a composite structure with PVD-deposited tungsten liner layer having controlled grain size greater than 100 Ångstroms followed by CVD tungsten film. This composite material approach reduces overall stack resistivity, enabling lower line resistance in high-density interconnect structures.
3Ease of manufacture
If bulk CVD tungsten is grown on nucleation layer, then the deposition process is simple, but the resistivity reduction becomes challenging
Solution Approach 1:
The patent changes the liner layer deposition from CVD to PVD and controls grain size to greater than 100 Ångstroms, which reduces resistivity while maintaining a relatively simple two-step deposition process (PVD liner + CVD fill), thus balancing ease of manufacture with resistivity control.
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 significantly reduces stack resistivity to less than 13 ρohm-cm, improving the properties of tungsten films and layers, particularly in narrow trenches and high aspect ratios, by directly depositing tungsten films on PVD-deposited liner layers without intermediate air breaks or bias power, resulting in improved grain size and orientation.
Implementation Method 1
forming a tungsten liner layer on a surface of the substrate using a physical vapor deposition process
Implementation Method 2
forming a tungsten film directly on the tungsten liner layer using a chemical vapor deposition process
Data Source
AI summary
Apparatus and methods to provide electronic devices comprising tungsten film stacks are provided. A tungsten liner formed by physical vapor deposition is filled with a tungsten film formed by chemical vapor deposition directly over the tungsten liner.