HBT Emitter-Base Oxide Interface for Low Cbe and Re
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional Si/SiGe heterojunction bipolar transistors face challenges in achieving low emitter-base capacitance (Cbe) and resistance (Re) while maintaining controlled dopant diffusion and beta variation for power amplifier applications.
Innovation Solution
The implementation of a heterojunction bipolar transistor with a silicon-oxygen lattice interface, featuring a single crystalline semiconductor emitter and base regions with an oxide interface, formed using techniques such as epitaxial growth and selective etching, to control doping profiles and reduce capacitance and resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If poly-silicon emitters are used over a single crystal base, then emitter-base capacitance can be reduced, but emitter resistance increases and dopant diffusion control becomes difficult
Solution Approach 1:
The patent employs a composite structure combining poly-silicon emitter material with a single crystal semiconductor base, creating a heterojunction that leverages the low capacitance properties of poly-silicon while maintaining the high mobility and controlled diffusion characteristics of single crystal material. This composite approach resolves the contradiction by integrating materials with complementary properties.
Solution Approach 2:
The invention applies different material qualities to different regions: poly-silicon is used specifically in the emitter region where low capacitance is critical, while the base maintains single crystal structure for controlled dopant diffusion. This localized application of material properties optimizes each region's function without compromising the other.
2Reliability
If emitter doping is increased to reduce emitter resistance, then Re decreases, but dopant diffusion into the base increases uncontrollably
Solution Approach 1:
The patent introduces an intermediate layer or interface structure between the heavily doped emitter and the base region that acts as a barrier to dopant diffusion. This intermediary structure allows high emitter doping for low resistance while preventing excessive dopant migration into the base, thus resolving the contradiction between Re reduction and diffusion control.
Solution Approach 2:
The invention changes the physical or chemical parameters at the emitter-base interface, such as creating a graded composition profile or introducing a thin interfacial layer with specific properties that selectively block dopant diffusion while maintaining electrical conductivity. This parameter modification enables simultaneous achievement of low Re and controlled diffusion.
3Manufacturing precision
If a clean emitter-base interface with lower emitter doping is used to control diffusion, then dopant diffusion is reduced, but emitter resistance increases
Solution Approach 1:
The patent segments the emitter structure into multiple regions or layers with different doping levels and material compositions. The upper emitter region has lower doping for diffusion control, while the lower emitter region or contact region has higher doping for low resistance. This segmentation allows each region to optimize its function independently.
Solution Approach 2:
The invention employs a nested structure where a heavily doped emitter region is contained within or adjacent to a lightly doped emitter region. The outer lightly doped region controls diffusion at the interface, while the inner heavily doped region provides low resistance pathways, creating a nested configuration that satisfies both requirements.
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 configuration provides improved beta control, reduced Cbe, lower Re, and optimized beta-temperature behavior, enabling tighter beta variation and enhanced performance in power applications.
Implementation Method 1
an oxide interface at a junction of the emitter region and the base region
Data Source
AI summary
The present disclosure relates to semiconductor structures and, more particularly, to a heterojunction bipolar transistor having an emitter base junction with a silicon-oxygen lattice interface and methods of manufacture. The device includes: a collector region buried in a substrate; shallow trench isolation regions, which isolate the collector region buried in the substrate; a base region on the substrate and over the collector region; an emitter region composed of a single crystalline of semiconductor material and located over with the base region; and an oxide interface at a junction of the emitter region and the base region.