Lateral SiGe Bipolar Transistor Base Grading for Current Control
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Solution Overview
Problem
There is a need for improved structures and methods for forming bipolar junction transistors, particularly for lateral configurations, to enhance performance and efficiency.
Innovation Solution
A lateral bipolar junction transistor structure is developed, featuring a semiconductor substrate with a first and second raised terminal and an intrinsic base positioned laterally between them, where the intrinsic base includes a silicon-germanium portion with a graded germanium concentration in both lateral and vertical directions, achieved through specific fabrication processes involving ion implantation and thermal diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a lateral bipolar junction transistor structure is used, then integration density and device performance are improved, but manufacturing complexity increases
Solution Approach 1:
The transistor structure is divided into distinct lateral components (emitter, base, collector) arranged side-by-side on the substrate, enabling independent formation and integration of each component through separate processing steps while maintaining overall device functionality
Solution Approach 2:
The transistor layout transitions from a vertical stack to a lateral arrangement, utilizing the planar dimension of the substrate to position emitter, base, and collector regions horizontally, which improves integration density and enables new fabrication approaches
2Reliability
If a graded germanium concentration in the intrinsic base is implemented, then transistor performance and current control are improved, but manufacturing precision requirements increase
Solution Approach 1:
The germanium concentration in the intrinsic base is varied continuously as a gradient from one region to another, with higher concentration near the emitter and lower near the collector, to optimize carrier transport and current control characteristics
Solution Approach 2:
Different regions of the intrinsic base are assigned different germanium concentrations tailored to their specific functional requirements, with the graded profile providing locally optimized properties for carrier injection, transport, and collection
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 controlling collector-emitter current effectively and optimizing material properties, leading to enhanced operational characteristics.
Implementation Method 1
The intrinsic base includes a portion comprising silicon-germanium with a germanium concentration that is graded in the lateral direction
Implementation Method 2
achieved through specific fabrication processes involving ion implantation and thermal diffusion
Implementation Method 3
achieved through specific fabrication processes involving ion implantation and thermal diffusion
Data Source
Figure 1~2
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AI summary
A structure for a lateral bipolar junction transistor, the structure comprising: a semiconductor substrate (10); a first terminal (16), for example a collector, including a first raised semiconductor layer (16) on the semiconductor substrate (10); a second terminal (18), for example an emitter, including a second raised semiconductor layer (18) on the semiconductor substrate (10); and an intrinsic base (12, 30, 28) on the semiconductor substrate, the intrinsic base positioned in a lateral direction between the first raised semiconductor layer (16) of the first terminal and the second raised semiconductor layer (18) of the second terminal. The intrinsic base includes a first portion (30) comprising silicon-germanium with a first germanium concentration that is graded in the lateral direction, a second region (12) with a substantially uniform low germanium concentration and a third region (28) with a substantially uniform high germanium content.