Atomic Layer Deposition of Titanium Nitride Films
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Solution Overview
Problem
The semiconductor industry faces challenges in reducing the size of devices such as transistors and interconnects, leading to step coverage and material diffusion issues, particularly with high aspect ratio contact holes, and existing deposition methods like CVD and PVD result in poor conductivity and incomplete coverage.
Innovation Solution
The use of atomic layer deposition (ALD) to form titanium nitride (TiN) layers with specific precursors like tetrakisdiethylamidotitanium and ammonia, achieving low resistivity and excellent step coverage by controlling the thickness of TiN films through repeatable ALD cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If CVD or PVD methods are used to deposit TiN layers, then the deposition process can be completed, but the resulting layers have poor conductivity (high resistivity) or poor conformality (incomplete coverage)
Solution Approach 1:
The patent changes the fundamental deposition parameters by switching from CVD/PVD to ALD methodology, which uses sequential precursor exposure and self-limiting surface reactions. This parameter change enables atomic-level control of film growth, achieving both low resistivity (600-800 µohm-cm) and superior conformality (>80% step coverage) that cannot be achieved with conventional deposition methods
Solution Approach 2:
The patent replaces the physical vapor deposition or chemical vapor deposition mechanical processes with an atomic-layer deposition chemical process that relies on surface chemistry and self-limiting reactions. This substitution of the deposition mechanism enables precise thickness control and uniform coverage on high aspect ratio structures
2Speed
If device size is reduced to improve operational speed and reduce power requirements, then transistor performance improves, but step coverage issues arise when thin conductor lines traverse steep contact steps
Solution Approach 1:
The patent changes the deposition methodology from conventional CVD/PVD to ALD, which provides superior step coverage (>80%) even on high aspect ratio contact holes. This parameter change enables thin conductor lines to traverse steep contact steps without coverage gaps, maintaining reliability in scaled devices
Solution Approach 2:
The patent segments the deposition process into atomic layers through sequential precursor exposure, where each ALD cycle deposits a controlled monolayer. This segmentation approach ensures uniform coverage on complex 3D structures with high aspect ratios, maintaining step coverage integrity as devices are scaled down
3Length of moving object
If thinner dielectric and conductive layers are used to reduce device size, then device dimensions are reduced, but sensitivity to intermingling or diffusion of different materials increases
Solution Approach 1:
The patent changes the TiN layer deposition to ALD methodology, which produces films with low resistivity (600-800 µohm-cm) and superior conformality. These improved film properties enhance the barrier effectiveness against material diffusion in thinner layer structures, maintaining reliability as device dimensions are reduced
Solution Approach 2:
The patent uses TiN as a composite barrier layer between conductive interconnects and surrounding insulator layers. The ALD-deposited TiN forms a continuous, conformal composite structure that effectively prevents metal diffusion into dielectric materials, even in thin layer configurations
4Manufacturing precision
If ALD is used to deposit TiN layers, then low resistivity and excellent step coverage are achieved, but the process requires precise control of deposition cycles
Solution Approach 1:
The patent employs self-limiting surface reactions in the ALD process, where each precursor exposure automatically terminates when the surface is saturated. This self-service mechanism provides inherent thickness control without requiring complex real-time monitoring, achieving atomic-level precision through the chemistry itself rather than external control systems
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 ALD method produces highly conductive TiN layers with resistivity as low as 600 µohm-cm and greater than 75% step coverage, addressing the issues of material diffusion and coverage in high aspect ratio contact holes, while maintaining manufacturing robustness.
Implementation Method 1
a first species is chemisorbed on a substrate to form a first species monolayer onto the substrate from a gaseous first precursor
Implementation Method 2
The chemisorbed first species is contacted with a second precursor plasma effective to react with the first species monolayer to remove organic groups from the first species monolayer
Implementation Method 3
forming a titanium nitride layer on a substrate by atomic layer deposition (ALD)
Data Source
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Figure 3~4
AI summary
The use of atomic layer deposition (ALD) to form a conductive titanium nitride layer produces a reliable structure for use in a variety of electronic devices. The structure is formed by depositing titanium nitride by atomic layer deposition onto a substrate surface using a titanium-containing precursor chemical such as TDEAT, followed by a mixture of ammonia and carbon monoxide or carbon monoxide alone, and repeating to form a sequentially deposited TiN structure. Such a TiN layer may be used as a diffusion barrier underneath another conductor such as aluminum or copper, or as an electro-migration preventing layer on top of an aluminum conductor. ALD deposited TiN layers have low resistivity, smooth topology, high deposition rates, and excellent step coverage and electrical continuity.