BJT Emitter-Base and Base-Collector Superlattices for Dopant Control
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Solution Overview
Problem
Current semiconductor devices face limitations in achieving enhanced performance due to challenges in carrier mobility and dopant diffusion, which affect the efficiency and reliability of bipolar junction transistors (BJTs).
Innovation Solution
The implementation of a semiconductor superlattice structure with stacked groups of semiconductor and non-semiconductor monolayers, where the non-semiconductor monolayers are constrained within the crystal lattice of adjacent semiconductor portions, enhances carrier mobility and acts as a dopant barrier, reducing unwanted scattering and diffusion effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional semiconductor structures are used, then manufacturing is simpler, but carrier mobility is limited and dopant diffusion occurs
Solution Approach 1:
The base and collector regions are segmented into multiple thin semiconductor monolayers (e.g., silicon layers) separated by non-semiconductor monolayers (e.g., oxygen, carbon, or insulating layers). This segmentation creates a superlattice structure where each layer is only a few atomic layers thick, enabling quantum confinement effects that enhance carrier mobility while the non-semiconductor layers act as dopant diffusion barriers.
Solution Approach 2:
The patent employs composite material structures combining semiconductor monolayers (silicon, germanium, silicon-germanium alloys) with non-semiconductor monolayers (oxygen, carbon, nitrogen, or insulating materials). This composite approach creates a superlattice with properties superior to conventional homogeneous structures, achieving both high carrier mobility through quantum effects and dopant blocking through the non-semiconductor interlayers.
2Reliability
If dopant diffusion is allowed, then manufacturing is easier, but device performance degrades due to unwanted scattering and diffusion
Solution Approach 1:
Non-semiconductor monolayers (oxygen, carbon, nitrogen, or insulating materials) are inserted as intermediary layers between semiconductor regions. These intermediary layers serve dual functions: they block dopant diffusion between adjacent semiconductor regions while also providing quantum confinement that enhances carrier mobility. The intermediaries effectively prevent harmful dopant mixing without requiring complex manufacturing processes.
3Speed
If superlattice structure is implemented, then carrier mobility is enhanced, but manufacturing complexity increases
Solution Approach 1:
The patent utilizes parameter changes at the atomic scale, varying the thickness of semiconductor and non-semiconductor monolayers to optimize quantum confinement effects. By controlling layer thicknesses (typically 1-10 atomic layers) and material composition, the superlattice structure achieves enhanced carrier mobility through quantum mechanical effects while maintaining compatibility with existing semiconductor manufacturing processes.
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 improved charge carrier mobility and reduced dopant diffusion, leading to enhanced performance and reliability of BJTs by lowering conductivity effective mass and providing a barrier to dopant and material diffusion, thereby improving device mobility and reducing performance degradation.
Implementation Method 1
at least one first non-semiconductor monolayer constrained within a crystal lattice of adjacent first base semiconductor portions... acts as a dopant barrier, reducing unwanted scattering and diffusion effects
Implementation Method 2
a Si—Ge short period superlattice with higher mobility achieved by reducing alloy scattering in the superlattice
Implementation Method 3
The resulting biaxial strain in the upper silicon layer alters the carrier mobilities enabling higher speed and/or lower power devices
Data Source
AI summary
A bipolar junction transistor (BJT) may include a substrate defining a collector region therein. A first superlattice may be on the substrate including a plurality of stacked groups of first layers, with each group of first layers including a first plurality of stacked base semiconductor monolayers defining a first base semiconductor portion, and at least one first non-semiconductor monolayer constrained within a crystal lattice of adjacent first base semiconductor portions. Furthermore, a base may be on the first superlattice, and a second superlattice may be on the base including a second plurality of stacked groups of second layers, with each group of second layers including a plurality of stacked base semiconductor monolayers defining a second base semiconductor portion, and at least one second non-semiconductor monolayer constrained within a crystal lattice of adjacent second base semiconductor portions. An emitter may be on the second superlattice.