Semiconductor Base Link Region Reduces Resistance and Capacitance
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Solution Overview
Problem
Conventional semiconductor devices, such as bipolar junction transistors (BJTs) and heterojunction bipolar transistors (HBTs), face a trade-off between base resistance (Rb) and collector junction capacitance (Cjc), which limits their maximum frequency of oscillation (fmax) and frequency response.
Innovation Solution
The semiconductor device design includes a collector region, a base region with multiple dielectric layers and a base link region, which reduces base-collector feedback capacitance and resistance by strategically forming dielectric layers and extrinsic base regions to optimize the coupling between the base and collector regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional BJT and HBT structures are used, then device simplicity is maintained, but base resistance and collector junction capacitance cannot be simultaneously reduced
Solution Approach 1:
The base region is divided into multiple segments including a first base region, a second base region, and an extrinsic base region, with dielectric layers positioned between them. This segmentation allows independent optimization of each base region segment to simultaneously reduce base resistance and collector junction capacitance while maintaining manageable device complexity.
Solution Approach 2:
Dielectric layers are introduced as intermediary elements between the base region and collector region. These dielectric layers act as mediators that reduce the direct coupling and feedback capacitance between base and collector, thereby improving frequency response without requiring fundamental changes to the basic transistor structure.
2Speed
If base resistance is reduced to improve fmax, then collector junction capacitance increases due to conventional structure trade-offs
Solution Approach 1:
Dielectric layers are positioned between the base region and collector region to act as intermediary elements that reduce feedback capacitance. This allows the base resistance to be reduced through optimized base region design while the dielectric layers prevent the corresponding increase in collector junction capacitance that would occur in conventional structures.
Solution Approach 2:
Different regions of the base are given different properties through the segmented structure. The first base region has different characteristics than the second base region, with dielectric layers strategically positioned to provide local capacitance reduction where needed while maintaining low resistance pathways in other areas.
Data Source
AI summary
A semiconductor device includes a semiconductor substrate with a collector region formed within the semiconductor substrate. A base region, including a first base region and a second base region, is formed over the collector region. An extrinsic base region is formed laterally adjacent to and coupled to the second base region. A base link region is disposed proximate to the second base region, wherein the base link region couples the extrinsic base sidewall to the second base region. A method for forming a semiconductor device includes forming the collector region within the semiconductor substrate, forming a plurality of dielectric layers over the collector region, forming an extrinsic base layer over the collector region, etching an emitter window, forming the first base region over the collector region, forming the second base region over the first base region, wherein forming the second base region includes forming the base link region.