Lateral SiGe Bipolar Transistor Base With Graded Germanium Profile
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Solution Overview
Problem
There is a need for improved structures and methods for forming bipolar junction transistors, particularly for heterojunction bipolar transistors, to enhance performance and efficiency.
Innovation Solution
A lateral bipolar junction transistor structure is developed, featuring a semiconductor substrate with graded germanium concentration in the intrinsic base, formed by specific epitaxial growth and ion implantation processes, allowing for a controlled germanium distribution between the emitter and collector terminals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a heterojunction bipolar transistor is used with different semiconductor materials for emitter/collector and intrinsic base, then the energy bandgap creates heterojunctions that improve performance, but the manufacturing complexity and precision requirements increase
Solution Approach 1:
The patent applies local quality by implementing a graded germanium concentration profile within the intrinsic base region. The germanium concentration varies spatially, being higher near the collector and lower near the emitter, which creates localized variations in bandgap energy. This gradual transition optimizes carrier transport at different locations within the base, improving overall transistor performance while managing the complexity of heterojunction fabrication
Solution Approach 2:
The patent utilizes parameter changes by systematically varying the germanium concentration parameter throughout the intrinsic base region. This gradient in composition creates a corresponding gradient in bandgap energy, which is carefully controlled to optimize the heterojunction characteristics. The parameter variation approach allows for improved carrier injection and transport while maintaining manufacturability through established epitaxial growth techniques
2Productivity
If a graded germanium concentration is implemented in the intrinsic base, then current control and efficiency are enhanced, but the manufacturing precision requirements increase
Solution Approach 1:
The patent implements parameter changes by establishing a controlled gradient in germanium concentration across the intrinsic base. This gradual variation in composition is achieved through precision epitaxial growth processes that can maintain tight control over the doping profile. The parameter gradient is designed to optimize current transport while remaining within the capabilities of existing manufacturing precision
Solution Approach 2:
The graded germanium structure applies local quality by creating spatially varying material properties within the base region. The composition is tailored locally to optimize carrier injection at the emitter-base junction and collector-base junction separately, improving overall current control efficiency. This localized optimization is achieved through controlled variations in germanium concentration rather than uniform composition
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
The graded germanium concentration in the intrinsic base improves the transistor's performance by optimizing the base-emitter and base-collector junctions, enhancing current control and efficiency.
Implementation Method 1
a portion comprising silicon-germanium with a germanium concentration that is graded in the lateral direction
Implementation Method 2
formed by specific epitaxial growth and ion implantation processes
Implementation Method 3
formed by specific epitaxial growth and ion implantation processes
Data Source
AI summary
Structures for a bipolar junction transistor and methods of forming a structure for a bipolar junction transistor. The structure includes a first terminal having a first raised semiconductor layer on a semiconductor substrate, a second terminal having a second raised semiconductor layer on the semiconductor substrate, and an intrinsic base on the semiconductor substrate. The intrinsic base is positioned in a lateral direction between the first raised semiconductor layer of the first terminal and the second raised semiconductor layer of the second terminal. The intrinsic base includes a portion containing silicon-germanium with a germanium concentration that is graded in the lateral direction.