Fin-Based Bipolar Transistor Current Alignment
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Solution Overview
Problem
The integration of both MOSFET and BJT devices in a single circuit is costly and time-consuming due to the different processes required for their formation, making it desirable to have an efficient BJT structure compatible with the finFET fabrication process.
Innovation Solution
A Bipolar Junction Transistor (BJT) device is designed with elongated emitter, base, and collector lines formed on top of fin interconnect structures, allowing electric current to flow in a single axis, increasing current efficiency, and utilizing the same materials and processes as MOSFET devices for compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If different processes are used to form BJT and MOSFET devices separately, then each device type can be optimized for its specific performance requirements, but the production cost and time increase significantly
Solution Approach 1:
The patent merges the formation processes of BJT and MOSFET devices into a single integrated fabrication sequence. Both device types are formed simultaneously using the same fin structure formation, doping processes, and thermal treatments, eliminating the need for separate production lines and reducing overall manufacturing time and cost while maintaining optimized performance for each device type
Solution Approach 2:
The patent creates a universal fabrication process that can produce both BJT and MOSFET devices using the same equipment, materials, and process parameters. The fin structure serves as a common foundation for both device types, and the doping and thermal processes are designed to achieve the required characteristics for both transistor types simultaneously
2Ease of manufacture
If traditional concentric ring BJT layout is used, then the device structure is simple to manufacture, but the current flow efficiency decreases due to multi-directional current paths
Solution Approach 1:
The patent transitions from the traditional planar concentric ring layout to a vertical fin-based structure where current flows primarily in one direction along the fin length. This dimensional change from 2D planar to 3D vertical architecture enables single-axis current flow while maintaining ease of manufacture through standard fin formation processes
Solution Approach 2:
The patent employs an asymmetric elongated fin structure where the length is significantly greater than the width, creating a preferred current flow path. This asymmetric geometry concentrates current flow along the longitudinal axis of the fin, improving current efficiency while the structure remains compatible with standard fabrication processes
Data Source
AI summary
A method of forming a Bipolar Junction Transistor (BJT) includes forming an elongated collector line, forming an elongated emitter line parallel to the collector line, and forming an elongated base line parallel to the collector line and positioned between the collector line and the base line. The emitter line, the base line, and the collector line are formed over fin structures.