Bulk FinFET Punchthrough Stopper via STI Liner Diffusion
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Solution Overview
Problem
Bulk finFETs suffer from punchthrough currents due to their lower manufacturing cost compared to SOI finFETs, which can degrade electrical performance, and existing solutions like dopant implantation introduce device variability.
Innovation Solution
A semiconductor structure and method involving a semiconductor substrate with fins, a punchthrough stopper region in the lower portion of each fin, a doped shallow trench isolation liner, and an annealing process to diffuse dopants from the liner, forming a self-aligned punchthrough stopper without ion implantation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dopant implantation is performed to form a punchthrough stopper, then punchthrough currents are suppressed, but device variability increases
Solution Approach 1:
The patent replaces the mechanical ion implantation process with a thermal diffusion process. Instead of physically implanting dopant ions into the substrate, the invention uses thermal energy to diffuse dopants from the shallow trench isolation liner into the semiconductor substrate, forming the punchthrough stopper region. This substitution eliminates the variability introduced by ion implantation while achieving the same electrical effect of suppressing punchthrough currents.
Solution Approach 2:
The shallow trench isolation liner serves as an intermediary material that contains and controls the dopant source. Rather than directly implanting dopants into the substrate, the dopants are first incorporated into the STI liner during its formation, and then thermally diffused into the substrate. This intermediary approach provides better control over dopant distribution and reduces device variability.
2Ease of manufacture
If bulk finFET structure is used instead of SOI finFET, then manufacturing cost decreases, but punchthrough currents increase
Solution Approach 1:
The patent performs preliminary doping of the shallow trench isolation liner before the fin formation is complete. By incorporating dopants into the STI liner early in the fabrication process and then using thermal diffusion to form the punchthrough stopper, the method prevents punchthrough currents from the outset rather than requiring additional corrective steps later. This preliminary action maintains the cost advantage of bulk finFETs while ensuring electrical performance.
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 reduces device variability and improves electrical performance by eliminating the need for ion implantation, thereby enhancing the reliability and efficiency of bulk finFETs.
Implementation Method 1
annealing the semiconductor structure
Data Source
AI summary
An improved bulk FinFET with a punchthrough stopper region, and method of fabrication are disclosed. The dopants used to form the punchthrough stopper are supplied from a shallow trench isolation liner. An anneal diffuses the dopants from the shallow trench isolation liner into the bulk substrate and lower portion of the fins, to form the punchthrough stopper region.