Atomic Layer Deposition of Molecular Clusters for Transistor Threshold Voltage Tuning
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Solution Overview
Problem
As semiconductor technology nodes scale below 10 nm, it becomes increasingly challenging to maintain control over transistor threshold voltage and contact resistance, which are critical for optimizing switching speed and power consumption in integrated circuits.
Innovation Solution
The use of atomic layer deposition (ALD) to form molecular cluster films in the gate and source/drain regions of transistors, where the size and charge of clusters are controlled to adjust the threshold voltage and contact resistance by altering the energy band structures, utilizing ionic and neutral silver bromide (AgBr) or lanthanum oxide (LaOX) clusters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional doping methods are used to adjust threshold voltage, then transistor performance can be tuned, but manufacturing precision and control become increasingly challenging as technology nodes scale below 10 nm
Solution Approach 1:
The patent changes the fundamental parameter being controlled from dopant concentration (conventional method) to molecular cluster size and composition (ALD method). By depositing atomic layers of materials like AgBr or La2O3 with precisely controlled thicknesses and compositions, the threshold voltage can be tuned without relying on diffusion-based doping processes that lose precision at sub-10nm nodes. This transforms the control mechanism from statistical dopant distribution to deterministic atomic layer deposition.
Solution Approach 2:
The patent replaces the mechanical/chemical process of ion implantation and thermal diffusion with a vapor-phase deposition process. Instead of physically shooting ions into the substrate and relying on thermal energy for diffusion, the invention uses atomic layer deposition where precursor gases react on the substrate surface to form precise atomic layers. This substitution eliminates the variability inherent in diffusion-based methods and provides atomic-level precision in controlling the electrical characteristics.
2Length of moving object
If gate oxide thickness is reduced to scale transistors, then device dimensions are reduced, but control of threshold voltage and contact resistance becomes more difficult
Solution Approach 1:
The patent employs composite material structures where thin gate oxides are combined with interfacial layers of molecular clusters (such as AgBr or La2O3). This composite approach allows the gate oxide to be scaled to sub-10nm thickness while the interfacial molecular layer provides a buffer that maintains electrical control. The molecular clusters create favorable band alignment and reduce interface states, enabling reliable threshold voltage control even with extremely thin gate oxides that would otherwise be uncontrollable.
3Ease of manufacture
If dopant implantation is used to form source and drain regions, then contact resistance can be adjusted, but manufacturing complexity and precision requirements increase at smaller nodes
Solution Approach 1:
The patent replaces ion implantation mechanics with atomic layer deposition chemistry. Instead of using high-energy ion beams to force dopants into the lattice and then relying on complex annealing schedules to achieve desired profiles, the invention uses sequential ALD cycles to deposit precise atomic layers of dopant materials. This chemical deposition approach provides inherent precision through the self-limiting nature of ALD reactions, eliminating the need for complex implantation and annealing processes while achieving better profile control at sub-10nm dimensions.
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 allows for precise tuning of transistor performance by adjusting the energy band gaps, enabling a range of threshold voltages and reducing contact resistance, thereby enhancing switching speed and reducing power consumption.
Implementation Method 1
an atomic layer deposition (ALD) system is disclosed, along with a method for depositing on semiconductor wafers certain molecular clusters to form thin film junctions
Data Source
AI summary
Energy bands of a thin film containing molecular clusters are tuned by controlling the size and the charge of the clusters during thin film deposition. Using atomic layer deposition, an ionic cluster film is formed in the gate region of a nanometer-scale transistor to adjust the threshold voltage, and a neutral cluster film is formed in the source and drain regions to adjust contact resistance. A work function semiconductor material such as a silver bromide or a lanthanum oxide is deposited so as to include clusters of different sizes such as dimers, trimers, and tetramers, formed from isolated monomers. A type of Atomic Layer Deposition system is used to deposit on semiconductor wafers molecular clusters to form thin film junctions having selected energy gaps. A beam of ions contains different ionic clusters which are then selected for deposition by passing the beam through a filter in which different apertures select clusters based on size and orientation.