Sub-fin Doping via Dopant Source Layers in FinFET Arrays
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Solution Overview
Problem
The manufacturing of FinFETs faces challenges in sub-fin doping, particularly at advanced nodes, due to difficulties in isolation doping and integration of conformal masking layers, which affect carrier mobility and device geometry.
Innovation Solution
A gap fill approach for sub-fin doping that eliminates the need for intra fin barrier or masking layers, using dopant source layers to fill intra fin gaps and drive dopants into sub-fin regions, thereby enabling precise doping of semiconductor fins without affecting the active channel region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conformal masking layers are used for sub-fin doping, then doping precision is improved, but device complexity increases due to integration challenges at small fin-pitch layouts
Solution Approach 1:
The patent removes the conformal masking layer from the doping process entirely. Instead of using complex multi-layer masking structures, the invention directly forms dopant source layers in the intra-fin regions without requiring additional barrier or masking layers, thereby eliminating the geometric challenges associated with small fin-pitch layouts while maintaining doping precision
Solution Approach 2:
The patent segments the doping process by selectively forming dopant source layers only in the intra-fin regions between adjacent fins, rather than using a blanket masking approach. This segmentation allows precise doping control in specific locations without requiring complex conformal masking structures across the entire fin array
2Productivity
If intra fin spacing is reduced to increase device density, then productivity is improved, but manufacturing precision deteriorates due to challenges in localized dopant introduction
Solution Approach 1:
The patent transitions from a two-dimensional surface-level masking approach to a three-dimensional volumetric doping approach. By forming dopant source layers that extend vertically and fill the intra-fin gaps between adjacent fins, the process achieves precise dopant introduction even when horizontal spacing between fins is reduced, enabling higher device density without sacrificing doping precision
Solution Approach 2:
The patent performs preliminary formation of dopant source layers in the intra-fin regions before the actual doping step. This preliminary action ensures that dopants are pre-positioned in the correct locations with proper concentration profiles, enabling precise doping control even at reduced intra-fin spacing where conventional masking approaches would fail
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 method allows for effective sub-fin doping, reducing leakage and enabling the formation of complementary device architectures, while avoiding unintentional doping of the channel regions, thus improving device performance and scalability.
Implementation Method 1
driving dopants from the dopant source layers into sub-fin regions of the fins below the channel regions
Data Source
AI summary
A gap fill method for sub-fin doping includes forming semiconductor fin arrays over a semiconductor substrate, forming a first dopant source layer over a first fin array and filling intra fin gaps within the first array, and forming a second dopant source layer over a second fin array and filling intra fin gaps within the second array. The first and second dopant source layers are recessed to expose a channel region of the fins. Thereafter, an annealing step is used to drive dopants from the dopant source layers locally into sub-fin regions of the fins below the channel regions.