GeOI Lateral Bipolar Transistor Silicon Passivation
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Solution Overview
Problem
Germanium-on-insulator (GeOI) lateral bipolar junction transistors have limited current gain due to excessive base current, primarily attributed to defects at the Ge/BOX interface, which hampers their potential in power-efficient applications compared to SiGeOI and SOI devices.
Innovation Solution
A semiconductor structure with a silicon passivation layer on an insulator layer, including a germanium layer with dopants of a specific conductivity type, and an extrinsic base region, is formed to reduce interface defects and enhance current gain. This structure involves bonding substrates with oxide-to-oxide bonding and doping to create regions with opposite conductivity types, thereby improving the GeOI transistor performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If GeOI lateral bipolar transistors are used to achieve lower operation voltage and power-efficient applications, then power efficiency is improved, but current gain is limited due to excessive base current
Solution Approach 1:
A silicon passivation layer is introduced as an intermediary between the germanium layer and the BOX layer. This intermediate layer passivates the Ge/BOX interface, reducing interface defects that cause excessive base current, thereby improving current gain while maintaining the power efficiency benefits of GeOI transistors
Solution Approach 2:
The interface properties of the Ge/BOX interface are modified by introducing the silicon passivation layer. This changes the electrical and structural parameters at the interface, reducing defect density and improving the transistor's current gain characteristic
2Reliability
If GeOI wafers with good passivation of the Ge/BOX interface are used to fully utilize the benefit of GeOI bipolar transistor, then current gain is improved, but manufacturing complexity increases
Solution Approach 1:
The silicon passivation layer is formed on the germanium layer before bonding to the BOX layer. This preliminary passivation action ensures that the Ge/BOX interface is already protected against defect formation, simplifying the overall manufacturing process by preventing rather than correcting interface issues
Solution Approach 2:
The silicon passivation layer serves as a mediator that simplifies the interface between germanium and BOX. Rather than requiring complex processes to achieve good interface quality, the intermediate silicon layer provides inherent passivation, reducing manufacturing complexity
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 proposed structure effectively reduces interface defects and enhances the current gain of GeOI lateral bipolar junction transistors, allowing them to operate at lower voltages with improved efficiency, comparable to SiGeOI and SOI devices.
Implementation Method 1
bonding a first substrate including a germanium layer, a first silicon passivation layer, and a first oxide layer to a second substrate including a second oxide layer to form a vertical stack of an insulator layer
Implementation Method 2
the germanium layer and the first silicon passivation layer have a doping of the first conductivity type
Data Source
AI summary
Semiconductor structure including germanium-on-insulator lateral bipolar junction transistors and methods of fabricating the same generally include formation of a silicon passivation layer at an interface between the insulator layer and a germanium layer.