Fin Transistor Gaps Reduce Leakage Current
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Solution Overview
Problem
Conventional FinFETs on bulk Si substrates suffer from significant leakage current at the bottom of the channel due to incomplete gate control, leading to high junction leakage and capacitance, which existing solutions like punch-through stop structures attempt to address but result in broad dopant distribution and increased capacitance.
Innovation Solution
A fin transistor structure is fabricated with a bulk semiconductor substrate where the fin is patterned to have gaps at source/drain regions, allowing insulation material to fill the gaps and directly tie the channel region to the substrate, eliminating the need for a punch-through stop structure and reducing leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a punch-through stop structure is introduced to suppress leakage current, then leakage current is reduced, but dopant distribution becomes broad and junction capacitance increases
Solution Approach 1:
The fin structure is segmented into different regions: the channel region remains directly tied to the substrate for good control, while the source/drain regions are separated from the substrate by gaps filled with insulation material. This segmentation allows different parts of the fin to have different electrical characteristics, suppressing leakage current without requiring broad dopant distribution
Solution Approach 2:
Insulation material is introduced as an intermediary substance filling the gaps between the source/drain regions of the fin and the substrate. This intermediary layer electrically isolates these regions from the substrate, preventing leakage current paths while maintaining the body-tied structure's advantages for the channel region
2Ease of manufacture
If the fin is completely tied to the substrate, then manufacturing is simple, but leakage current at the bottom of the channel increases
Solution Approach 1:
The fin-substrate connection is segmented rather than continuous. The channel region maintains direct contact with the substrate for simple manufacturing and good control, while the source/drain regions are segmented away from the substrate by insulation material, preventing leakage without complicating the overall fabrication process
Solution Approach 2:
Different regions of the fin have different relationships with the substrate: the channel region is directly tied for simplicity and control, while the source/drain regions are locally isolated by insulation material to prevent leakage. This local differentiation solves the contradiction between manufacturing simplicity and leakage suppression
Data Source
AI summary
A fin transistor structure and a method of fabricating the same are disclosed. In one aspect the method comprises providing a bulk semiconductor substrate, patterning the semiconductor substrate to form a fin with it body directly tied to the semiconductor substrate, patterning the fin so that gaps are formed on the bottom of the fin at source/drain regions of the transistor structure to be formed. This is performed wherein a portion of the fin corresponding to the channel region of the transistor structure to be formed is directly tied to the semiconductor substrate, while other portions of the fin at the source/drain regions are separated from the surface of the semiconductor substrate by the gaps. Also, filling an insulation material into the gaps, and fabricating the transistor structure based on the semiconductor substrate with the fin formed thereon are disclosed. Thereby, it is possible to reduce the leakage current while maintaining the advantages of body-tied structures.