Lateral Bipolar Junction Transistor Fin Structure Epitaxial Growth
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Solution Overview
Problem
As semiconductor technology advances to nanometer process nodes, there is a need for improved methods to fabricate bipolar junction transistors (BJTs) that enhance device performance, current gain, and operational range while maintaining cost-effectiveness in high-density integrated circuits.
Innovation Solution
The method involves forming PNP and NPN BJTs on semiconductor substrates using fin structures with epitaxial emitters and collectors, along with gate stacks, to create lateral BJTs. This process includes forming n-type and p-type doped regions, etching trenches, depositing insulating materials, and growing epitaxial silicon germanium or silicon phosphide/carbon for the emitter and collector, with gate dielectric layers and spacers to control current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional BJT fabrication methods are used, then manufacturing simplicity is maintained, but current gain and operational range are insufficient
Solution Approach 1:
The BJT structure is segmented into distinct epitaxial regions (emitter, base, collector) formed by separate epitaxial growth steps. This segmentation allows precise control of doping profiles and material composition in each region, improving current gain while maintaining manageable fabrication complexity through modular processing.
Solution Approach 2:
Different epitaxial regions are grown with locally optimized properties: silicon germanium for emitter and collector regions to control band alignment and carrier injection, and silicon phosphide/carbon for base region to optimize recombination characteristics. This local quality optimization enhances operational range and current gain without requiring complete redesign of the entire device structure.
2Productivity
If device density is increased to pursue higher performance, then productivity is improved, but manufacturing precision requirements increase
Solution Approach 1:
The epitaxial growth process is designed to be self-aligning, where the fin structure geometry and pre-formed doped regions automatically define the epitaxial layer boundaries and doping profiles. This self-service mechanism reduces the need for additional alignment steps and precision control, enabling higher device density without proportionally increasing manufacturing precision requirements.
Solution Approach 2:
Fin structures and doped regions are pre-formed before epitaxial growth, establishing the geometric and electrical framework that guides subsequent epitaxial layer formation. This preliminary action ensures that high-density device layouts are already optimized for the epitaxial process, reducing precision requirements during the critical epitaxial growth step.
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 improves the current gain and operational range of BJTs, enabling more efficient control of current flow and enhancing the performance of integrated circuit devices by forming lateral BJTs with precise epitaxial structures and gate control.
Implementation Method 1
a gate dielectric layer and spacers to control current flow
Implementation Method 2
growing epitaxial silicon germanium or silicon phosphide/carbon for the emitter and collector
Data Source
AI summary
A bipolar junction transistor includes a semiconductor substrate, a fin structure, an epitaxial emitter, an epitaxial collector and a gate. The fin structure is disposed on the semiconductor substrate and has a base portion of a first conductivity type, a first recessed portion and a second recessed portion. The epitaxial emitter of a second conductivity type is disposed in the first recessed portion of the fin structure. The epitaxial collector of the second conductivity type is disposed in the second recessed portion of the fin structure. The gate is disposed on the base portion of the fin structure and isolated from the base portion of the fin structure.