Monocrystalline Extrinsic Base in Vertical Bipolar Transistors
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Solution Overview
Problem
Conventional semiconductor devices, such as bipolar junction transistors (BJTs) and heterojunction bipolar transistors (HBTs), face limitations in achieving reduced base resistance, which restricts their maximum frequency of oscillation and frequency response due to the use of polycrystalline extrinsic base regions, resulting in limited hole mobility and higher base resistance.
Innovation Solution
The formation of a semiconductor device with a monocrystalline extrinsic base region, coupled to a seed region using selective or non-selective epitaxy, reduces base resistance by optimizing the seed region's geometry and material composition, enabling improved electrical coupling and mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a polycrystalline extrinsic base region is used in conventional semiconductor devices, then the device structure is simpler to manufacture, but the base resistance increases and hole mobility decreases
Solution Approach 1:
The patent changes the crystalline structure parameter of the extrinsic base region from polycrystalline to monocrystalline. This parameter change fundamentally alters the material properties, reducing base resistance and improving hole mobility while maintaining manufacturability through selective or non-selective epitaxial growth processes.
2Ease of manufacture
If a polycrystalline extrinsic base region is used in conventional semiconductor devices, then the device structure is simpler to manufacture, but the maximum frequency of oscillation decreases
Solution Approach 1:
The patent changes the crystalline structure parameter of the extrinsic base region from polycrystalline to monocrystalline. This parameter change fundamentally alters the material properties, reducing base resistance and improving hole mobility while maintaining manufacturability through selective or non-selective epitaxial growth processes.
3Reliability
If a monocrystalline extrinsic base region is formed using selective or non-selective epitaxy, then hole mobility increases and base resistance decreases, but the manufacturing process becomes more complex
Solution Approach 1:
The patent applies preliminary action by forming a seed region before the extrinsic base region. This seed region serves as a foundation that enables subsequent monocrystalline growth through selective or non-selective epitaxy, thereby reducing base resistance while managing manufacturing complexity through structured process sequencing.
Solution Approach 2:
The patent introduces a seed region as an intermediary element between the substrate and the monocrystalline extrinsic base region. This intermediary facilitates the formation of high-quality monocrystalline material, enabling reduced base resistance while managing the complexity of the manufacturing process through a controlled growth interface.
4Speed
If a monocrystalline extrinsic base region is formed using selective or non-selective epitaxy, then hole mobility increases and base resistance decreases, but the manufacturing process becomes more complex
Solution Approach 1:
The patent applies preliminary action by forming a seed region before the extrinsic base region. This seed region serves as a foundation that enables subsequent monocrystalline growth through selective or non-selective epitaxy, thereby reducing base resistance and improving frequency response while managing manufacturability through structured process sequencing.
Solution Approach 2:
The patent introduces a seed region as an intermediary element between the substrate and the monocrystalline extrinsic base region. This intermediary facilitates the formation of high-quality monocrystalline material, enabling reduced base resistance and improved speed while managing the complexity of the manufacturing process through a controlled growth interface.
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 hole mobility and reduces base resistance, thereby increasing the maximum frequency of oscillation and improving frequency response in semiconductor devices.
Implementation Method 1
The formation of a semiconductor device with a monocrystalline extrinsic base region, coupled to a seed region using selective or non-selective epitaxy
Implementation Method 2
an extrinsic base region having an upper surface formed over the seed region and electrically coupled to the base region. At least a portion of the extrinsic base region may include a monocrystalline material
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
A bipolar junction transistor (200) is formed, including a semiconductor substrate (210), a collector region (226, 220) formed within the semiconductor substrate (210) in a first semiconductor region having an upper surface and a collector sidewall (225), an intrinsic base region (230, 232, 234) disposed over the collector region, a seed region (240, 244, 246) formed at an upper surface of the collector (230) outside the intrinsic base region, an extrinsic base region (250) having an upper surface and formed over the seed region (244) and electrically coupled to the intrinsic base region (230, 232, 234), and an emitter region (262) formed over the base region, wherein the seed region (240) is made of a monocrystalline semiconductor material and has a lower portion (244) coupled to the collector (220) and an upper portion (246) coupled to the extrinsic base (250).