Quantum Dot Source-Drain Tuning for MOSFET Threshold Control
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Solution Overview
Problem
As technology nodes for integrated circuits scale below 10 nm, maintaining precise control of electrical characteristics in bulk semiconductor devices, such as MOSFETs, becomes increasingly challenging due to difficulties in controlling the threshold voltage (Vt) and energy band structure, which affects device performance.
Innovation Solution
Incorporating metallic quantum dots into the source and drain regions of MOSFETs, allowing for precise control of the threshold voltage by altering the energy gap through varying the size, shape, and composition of the quantum dots, such as silver bromide films, which can be rich in bromine or silver atoms, and using ALD deposition to tune the energy band structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional doping methods are used to control threshold voltage, then device performance can be improved, but manufacturing precision deteriorates due to difficulties in controlling doping concentrations and locations
Solution Approach 1:
The patent changes the fundamental parameter of doping control from post-growth ion implantation to in-situ doping during epitaxial crystal growth. This allows precise control of dopant concentration and spatial distribution at the atomic level during the crystal formation process, eliminating the precision problems associated with conventional doping methods.
Solution Approach 2:
The patent incorporates dopants into the crystal structure during the epitaxial growth process itself, before the crystal is fully formed. This preliminary action ensures that dopants are uniformly distributed at the intended locations and concentrations, avoiding the need for subsequent high-temperature annealing and precise location control that characterizes conventional doping approaches.
2Productivity
If technology nodes scale below 10 nm, then device density and integration are improved, but control of electrical characteristics deteriorates due to challenges in maintaining threshold voltage and energy band structure
Solution Approach 1:
The patent employs in-situ doping during epitaxial growth to precisely control the energy band structure and threshold voltage at scaled dimensions. By controlling dopant incorporation at the atomic level during crystal formation, the method maintains electrical characteristic control even as device dimensions shrink below 10 nm, where conventional methods fail.
Solution Approach 2:
The patent enables different doping concentrations and compositions to be established in different regions (source and drain) during the epitaxial growth process. This local quality control allows optimization of electrical characteristics in specific device regions, maintaining performance control at scaled dimensions where uniform doping is insufficient.
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 improved control over the threshold voltage and enhanced transistor performance by precisely modifying the energy band structure, leading to better switching speed and operational characteristics.
Implementation Method 1
Quantum dot structures have intermediate electronic properties that differ from both bulk materials and discrete molecules, and these electronic properties can be tuned by varying the size and spacing of the quantum dot crystals
Implementation Method 2
In one embodiment, the quantum dots can be formed by any suitable deposition technique, such as, for example, molecular beam epitaxy (MBE), chemical vapor deposition (CVD), physical vapor deposition (PVD), or atomic layer deposition (ALD)
Data Source
AI summary
Incorporation of metallic quantum dots (e.g., silver bromide (AgBr) films) into the source and drain regions of a MOSFET can assist in controlling the transistor performance by tuning the threshold voltage. If the silver bromide film is rich in bromine atoms, anion quantum dots are deposited, and the AgBr energy gap is altered so as to increase Vt. If the silver bromide film is rich in silver atoms, cation quantum dots are deposited, and the AgBr energy gap is altered so as to decrease Vt. Atomic layer deposition (ALD) of neutral quantum dots of different sizes also varies Vt. Use of a mass spectrometer during film deposition can assist in varying the composition of the quantum dot film. The metallic quantum dots can be incorporated into ion-doped source and drain regions. Alternatively, the metallic quantum dots can be incorporated into epitaxially doped source and drain regions.