Heterojunction Bipolar Transistor Collector Sinker via Impurity Outdiffusion
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Solution Overview
Problem
The existing methods for manufacturing heterojunction bipolar transistors (HBTs) face challenges in reducing collector resistance while maintaining open-base breakdown voltage and minimizing manufacturing complexity, particularly in advanced CMOS nodes, where high RF performance is required without increasing costs or process complexity.
Innovation Solution
The method involves forming a trench through the shallow trench insulation and filling it with an impurity that outdiffuses to extend into the substrate, reducing collector resistance without compromising breakdown voltage, and eliminating the need for additional masks or implantation steps by using existing masks for trench formation and impurity deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a collector sinker is implemented to reduce collector resistance, then RF performance is improved, but the open-base breakdown voltage decreases
Solution Approach 1:
The patent applies local quality by creating a selectively implanted collector region with specific doping characteristics in a localized area adjacent to the active region. This selective implantation provides low resistance where needed for RF performance while maintaining higher resistance characteristics in other areas to preserve breakdown voltage.
Solution Approach 2:
The patent transitions from a conventional planar collector sinker approach to a three-dimensional structure by forming a collector region that extends vertically and laterally with controlled doping profiles. This dimensional approach allows optimization of resistance characteristics without compromising breakdown voltage through spatial separation of functions.
2Reliability
If additional process steps are added to reduce collector resistance, then RF performance is improved, but manufacturing complexity increases
Solution Approach 1:
The patent merges the collector sinker formation with the existing shallow trench insulation process. The collector region is formed during the same fabrication sequence that creates the isolation structures, eliminating the need for separate mask and implantation steps dedicated solely to sinker formation.
Solution Approach 2:
The patent makes the shallow trench insulation process multi-functional by having it serve both as isolation structure formation and as the framework for collector region implantation. This universal approach allows the same process steps to achieve multiple objectives, reducing overall manufacturing complexity.
3Ease of manufacture
If advanced CMOS nodes are used for HBT production, then cost is reduced, but additional process options are required to achieve high RF performance
Solution Approach 1:
The patent adjusts doping parameters, implantation energies, and thermal processing conditions to adapt standard CMOS processes for HBT fabrication. By modifying process parameters rather than adding entirely new process modules, the patent enables high RF performance in advanced CMOS nodes with minimal additional complexity.
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 results in a HBT with reduced collector resistance and improved breakdown voltage characteristics, suitable for high-frequency applications, while simplifying the manufacturing process and reducing costs by eliminating the need for extra masks and implantation steps.
Implementation Method 1
at least partially filling said trench with an impurity; and forming a collector connection in the substrate by developing said impurity to extend into the substrate
Data Source
AI summary
Disclosed is a method of manufacturing a heterojunction bipolar transistor comprising a substrate, an upper region of said substrate comprising an active region of the bipolar transistor bordered by shallow trench insulation, said active region comprising a buried collector region extending to a depth beyond the depth of the shallow trench insulation, the method comprising forming a trench in the substrate adjacent to said active region, said trench extending through the shallow trench insulation; at least partially filling said trench with an impurity; and forming a collector sinker in the substrate by developing said impurity to extend into the substrate to a depth beyond the depth of the shallow trench insulation. An IC comprising a heterojunction bipolar transistor manufactured by this method is also disclosed.