Lateral Bipolar Transistor Segmented Base for High Frequency
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Solution Overview
Problem
Current bipolar junction transistor structures and fabrication methods lack improved designs that enhance device performance, particularly in terms of base resistance optimization and maximum oscillation frequency.
Innovation Solution
A lateral bipolar junction transistor structure is developed with a base layer and an extrinsic base layer stacked in a lateral direction, where the extrinsic base layer has a wider width than the base layer, and airgaps are formed between the base and collector to reduce capacitance, facilitating better device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional bipolar junction transistor structure is used, then the fabrication process is simple, but the base resistance is high and maximum oscillation frequency is limited
Solution Approach 1:
The base is segmented into two distinct layers: an intrinsic base layer and an extrinsic base layer. The intrinsic base layer (first width) is positioned between the emitter and collector, while the extrinsic base layer (second width, greater than first width) is stacked laterally adjacent to it. This segmentation allows the intrinsic base to maintain low resistance for high-frequency operation while the extrinsic base provides additional functionality without interfering with the primary current flow path.
Solution Approach 2:
The patent transitions from a conventional planar base structure to a stacked lateral configuration where the extrinsic base layer is positioned in a lateral direction adjacent to the intrinsic base layer. This dimensional arrangement allows both base layers to coexist without increasing the vertical profile, enabling improved electrical characteristics while maintaining compatibility with standard fabrication processes.
2Reliability
If the base width is reduced to increase oscillation frequency, then maximum oscillation frequency improves, but base resistance increases
Solution Approach 1:
The base is divided into intrinsic and extrinsic regions with different widths and functions. The intrinsic base layer has a narrower width optimized for high-frequency operation, while the extrinsic base layer has a wider width that can provide additional current paths and reduce overall base resistance without compromising the high-frequency performance of the intrinsic region.
Solution Approach 2:
Different regions of the base are assigned different properties: the intrinsic base layer has dimensions optimized for high-frequency operation, while the extrinsic base layer has dimensions optimized for resistance reduction. This local differentiation allows each region to perform its specific function optimally without compromising the other.
Data Source
AI summary
Structures for a bipolar junction transistor and methods of forming a structure for a bipolar junction transistor. The structure includes an emitter having a raised portion, a collector having a raised portion, and a base having a base layer and an extrinsic base layer stacked with the base layer. The base layer and the extrinsic base layer are positioned in a lateral direction between the raised portion of the emitter and the raised portion of the collector, the base layer has a first width in the lateral direction, the extrinsic base layer has a second width in the lateral direction, and the second width is greater than the first width.