Molybdenum Metal Contact Stack Without Nitride Resistance Penalty
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Solution Overview
Problem
Integrated circuits face challenges with high contact resistance due to the inclusion of nitrogen-containing capping layers and liner materials, which hinder the reduction of via resistance in middle-of-line (MOL) structures.
Innovation Solution
A method involving physical vapor deposition (PVD) of a metal cap layer followed by atomic layer deposition (ALD) of a molybdenum conductor layer is employed, eliminating nitrogen-based layers to form a metal contact stack with reduced resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If nitrogen-containing capping layers and liner materials are used to improve adhesion and pass post-processing steps, then adhesion and process compatibility are improved, but contact resistance increases
Solution Approach 1:
The patent removes nitrogen-containing capping layers and liner materials from the contact stack structure. By extracting these harmful layers that contribute to contact resistance, the invention achieves lower resistance while maintaining adhesion through alternative material selection (tungsten and molybdenum layers) that provide both adhesion and low resistance properties simultaneously
Solution Approach 2:
The invention employs a composite metal contact stack consisting of tungsten and molybdenum layers. This composite structure combines the adhesion benefits traditionally provided by nitrogen-containing layers with the low resistance properties of pure metals, achieving both objectives without compromising either adhesion or contact resistance
2Reliability
If liner material is added to improve adhesion of metals to dielectric materials, then adhesion is improved, but via resistance increases
Solution Approach 1:
The patent eliminates the liner material layer from the contact stack. By removing this additional layer that contributes to via resistance, the invention achieves lower resistance while the tungsten and molybdenum layers provide sufficient adhesion to dielectric materials without requiring an additional liner layer
Solution Approach 2:
The tungsten and molybdenum layers in the contact stack serve multiple functions simultaneously: they provide adhesion to dielectric materials (replacing the adhesion function of liner materials) and maintain low via resistance (unlike traditional liner materials). This multi-functional approach eliminates the need for separate liner material layers
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 method achieves a sheet resistance of less than 20 μΩ-cm, significantly reducing contact resistance and enhancing the performance of transistors and MOL applications.
Implementation Method 1
depositing a metal cap layer on a substrate by physical vapor deposition (PVD)
Implementation Method 2
depositing a molybdenum conductor layer by atomic layer deposition (ALD) on the metal cap layer
Data Source
AI summary
Methods for depositing a metal contact stack on a substrate are described. The metal stack includes a metal cap layer and a molybdenum conductor layer. The method includes depositing the metal cap layer on the substrate by physical vapor deposition (PVD) and depositing the molybdenum conductor layer by atomic layer deposition (ALD) on the metal cap layer.