Vacuum Plasma Doping for Shallow Semiconductor Junctions
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Solution Overview
Problem
Conventional doping methods for semiconductor devices, such as ion implantation, face challenges in achieving high dopant activation with shallow junction depths, especially in three-dimensional structures like horizontal gate all around nanowires, where maintaining compatibility with advanced device dimensions is crucial.
Innovation Solution
A method involving plasma cleaning to remove native oxide from the substrate surface, followed by the deposition of a dopant layer using a plasma source, and subsequent ion implantation under vacuum conditions to introduce dopant ions, ensuring high dopant activation and shallow junction depths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ion implantation is used for doping, then dopant activation can be achieved, but junction depth becomes too deep for advanced device dimensions
Solution Approach 1:
The doping process is segmented into two distinct stages: (1) plasma deposition of dopant atoms as a thin layer on the substrate surface, and (2) ion implantation to drive these pre-deposited dopants into the substrate. This segmentation allows dopant activation without excessive junction depth penetration, as the dopants are already positioned at the surface before implantation begins.
Solution Approach 2:
The plasma deposition step performs a preliminary action by depositing dopant atoms onto the substrate surface before the ion implantation process. This preliminary placement of dopants at the surface ensures that subsequent implantation drives them to the desired shallow depth rather than requiring deep penetration from the outset.
2Reliability
If conventional doping methods are used, then doping can be achieved, but defectivity increases in three-dimensional structures
Solution Approach 1:
The invention changes the physical and chemical parameters of the doping process by using plasma-based deposition and implantation instead of conventional thermal diffusion. The plasma process operates at lower temperatures and different energy levels, reducing structural damage and defect formation in three-dimensional nanowire structures while maintaining effective dopant incorporation.
3Manufacturing precision
If multiple process steps are performed separately, then each step can be optimized, but process time and vacuum maintenance become problematic
Solution Approach 1:
The plasma deposition and ion implantation steps are merged into a single continuous process performed in the same vacuum chamber without breaking vacuum. This combination eliminates the time loss associated with chamber pumping and loading/unloading between separate processes, while maintaining optimal conditions for both deposition and implantation throughout the combined sequence.
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 enhances dopant activation, reduces defectivity, and achieves better control over dopant concentration and junction depth, resulting in improved performance metrics like lower contact resistance and current characteristics in semiconductor devices.
Implementation Method 1
performing a deposition of a dopant layer on the substrate surface using a plasma source
Implementation Method 2
exposing the substrate to an implant process when the dopant layer is disposed on the substrate surface, wherein the implant process introduces an ion species comprising the dopant element into the substrate
Implementation Method 3
exposing a substrate surface of the semiconductor substrate to a plasma clean
Data Source
AI summary
A method of doping a substrate may include exposing a substrate surface of the semiconductor substrate to a plasma clean, performing a deposition of a dopant layer on the substrate surface using a plasma source, after the plasma clean, the dopant layer comprising a dopant element; and exposing the substrate to an implant process when the dopant layer is disposed on the substrate surface, wherein the implant process introduces an ion species comprising the dopant element into the substrate, wherein the substrate is maintained under vacuum over a process duration spanning the plasma clean, the deposition of the dopant layer, and the implant process, and wherein at least a portion of the dopant layer is implanted into the substrate during the implant process.