SiGe-Base Horizontal Bipolar Transistor for Low-Complexity RF Performance
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Solution Overview
Problem
The high technological complexity and cost associated with manufacturing high-performance SiGe Heterojunction Bipolar Transistors (HBTs) due to additional fabrication steps and lithography masks, along with inferior electrical characteristics of lateral bipolar transistors in pure-Silicon, necessitate a more efficient and cost-effective method for producing transistors with improved high-frequency performance.
Innovation Solution
A method for manufacturing Horizontal Current Bipolar Transistors (HCBTs) with a Silicon-Germanium (SiGe) base, integrating standard semiconductor technology steps with CMOS and BiCMOS processes, including epitaxial growth of a base layered structure with Germanium and Carbon, and ion implantation to optimize doping profiles, reducing parasitic regions and increasing breakdown voltage flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If standard vertical-current SiGe HBTs are manufactured with optimized process for their characteristics, then cutoff frequency and maximum frequency of oscillations are improved, but device complexity and manufacturing cost increase due to additional fabrication steps and lithography masks
Solution Approach 1:
The patent combines the fabrication processes for SiGe HBTs and CMOS transistors into a unified BiCMOS technology platform. By merging the process flows, the patent eliminates the need for separate standalone SiGe HBT fabrication steps, thereby reducing overall device complexity and manufacturing cost while maintaining high-frequency performance characteristics.
Solution Approach 2:
The patent creates a universal BiCMOS process that can simultaneously fabricate both SiGe HBTs and CMOS transistors using shared fabrication steps. This multi-functional approach allows the same manufacturing infrastructure to produce multiple device types, reducing the need for dedicated complex process lines and lowering overall manufacturing costs.
2Ease of manufacture
If lateral bipolar transistors are fabricated in pure-Silicon, then manufacturing cost is reduced, but electrical characteristics are inferior compared to SiGe HBTs
Solution Approach 1:
The patent applies local quality by introducing SiGe material specifically in the base region of the lateral bipolar transistor where it is most needed for performance enhancement. The SiGe layer is grown epitaxially only in the intrinsic base region, providing localized improvement of electrical characteristics without requiring complete SiGe fabrication throughout the entire device structure.
Solution Approach 2:
The patent uses composite materials by combining Silicon and Germanium to form SiGe alloy in the base region. This composite material approach leverages the beneficial properties of both materials: Silicon provides the base substrate and CMOS compatibility, while Germanium addition enhances carrier mobility and electrical characteristics in the critical base region.
3Reliability
If additional fabrication steps are added to CMOS process to obtain high-performance SiGe HBTs, then RF and mmW application performance is improved, but manufacturing cost and process complexity increase
Solution Approach 1:
The patent performs preliminary action by forming the SiGe base layer through epitaxial growth before subsequent CMOS fabrication steps. This early introduction of SiGe material allows the base region to be pre-configured with enhanced electrical properties, enabling high-frequency performance to be achieved while minimizing the need for additional complex process steps later in the manufacturing flow.
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 enhances the cutoff frequency (fT) and maximum frequency of oscillations (fmax) while maintaining low-cost fabrication and flexibility in breakdown voltage adjustment, outperforming standard vertical-current SiGe HBTs by reducing parasitic parameters and improving electrical characteristics.
Implementation Method 1
a base layered structure layer, comprising of at least one doped layer including Germanium, Carbon or other impurities is grown at the sidewall and, also partially on top of said n-hill region
Implementation Method 2
ion implantation to optimize doping profiles
Data Source
AI summary
A semiconductor device including a Horizontal Current Bipolar Transistor (HCBT) and methods of manufacture. The device has a semiconductor substrate of a first conductivity type defining a wafer plane parallel to the semiconductor substrate and has a base region and a collector region forming a first metallurgical junction. The device also has an emitter region forming a second metallurgical junction with the base region. A flat portion of the first metallurgical junction and a flat portion of the second metallurgical junction are substantially parallel to each other and close an acute angle with the wafer plane. At least a portion of the base region comprises silicon-germanium alloy or silicon-germanium-carbon alloy.