Lateral Bipolar Transistor Delta-Doped Base High Voltage
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Solution Overview
Problem
Conventional semiconductor devices with lateral bipolar transistors are limited in their voltage range and robustness against high voltage peaks, making them unsuitable for power applications due to excessive currents and premature breakdowns caused by high electric field strengths at the collector-base junction.
Innovation Solution
Incorporating a highly doped delta-shaped sub-region in the base region with a doping concentration of 10^19 to 10^20 at/cm^3 and a thickness of 1-15 nm, extending laterally to the collector region, which reduces the maximum electric field strength and prevents punch-through, while using a mixed crystal of silicon and germanium and strain-relaxed buffer layers to enhance high-frequency properties and carrier mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high doping concentration is used in the base region to prevent punch-through, then the transistor can maintain proper operation, but the electric field strength at the collector-base junction becomes excessively high causing premature breakdown and limiting the voltage range
Solution Approach 1:
The patent applies local quality by creating a delta-shaped doping profile where the base region has different doping concentrations at different locations and depths. A highly doped delta region (10^19 to 10^20 atoms/cm³) is positioned near the collector-base junction to prevent punch-through, while the rest of the base region maintains a lower doping concentration (10^17 to 10^18 atoms/cm³) to reduce the electric field strength and avoid premature breakdown. This spatial variation in doping quality resolves the contradiction between preventing punch-through and reducing electric field effects.
2Adaptability or versatility
If the transistor is designed for high voltage operation, then the voltage range expands, but the robustness against short-lived high voltage peaks deteriorates due to excessive currents and premature breakdown
Solution Approach 1:
The patent applies preliminary action by pre-positioning a highly doped delta region in the base region before the transistor operates under high voltage conditions. This delta region, with its high doping concentration and specific spatial distribution, is prepared in advance to handle transient high voltage peaks by providing a low-resistance path that prevents excessive current flow and premature breakdown, thereby enhancing robustness while maintaining broad voltage range adaptability.
3Ease of manufacture
If a conventional lateral bipolar transistor structure is used, then the device can be manufactured with standard processes, but the collector-substrate capacitance and base-collector capacitance are comparatively large limiting high-frequency performance
Solution Approach 1:
The patent applies dimensionality change by transitioning from a conventional planar bipolar transistor structure to a vertical heterojunction bipolar transistor structure. The emitter, base, and collector regions are stacked vertically with the emitter region above the base region and the collector region below, creating a three-dimensional structure that reduces parasitic capacitances (collector-substrate and base-collector) while maintaining compatibility with standard semiconductor manufacturing processes through vertical epitaxial growth and ion implantation techniques.
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 solution enables the semiconductor device to operate over a larger voltage range with improved resistance to high voltage peaks, maintaining excellent high-frequency properties and high collector-base breakdown voltage, suitable for power transistor applications.
Implementation Method 1
these phenomena are connected with the occurrence of avalanche multiplication of charge carriers, which in turn is caused by a high electric field strength at the location of the collector-base junction
Implementation Method 2
the base region contains a mixed crystal of silicon and germanium. In such a device, there is a heterojunction between silicon and silicon-germanium, which heterojunction leads to a further improvement of the high-frequency behavior of the device
Data Source
AI summary
The invention relates to a semiconductor device (10) with a semiconductor body (12) comprising a bipolar transistor with an emitter region (1), a base region (2) and a collector region (3) of, respectively, a first conductivity type, a second conductivity type, opposite to the first conductivity type, and the first conductivity type, wherein, viewed in projection, the emitter region (1) is positioned above or below the base region (2), and the collector region (3) laterally borders the base region (2). According to the invention, the base region (2) comprises a highly doped subregion (2A) the doping concentration of which has a delta-shaped profile in the thickness direction, and said highly doped sub-region (2A) extends laterally as far as the collector region (3). Such a lateral bipolar transistor has excellent high-frequency properties and a relatively high breakdown voltage between the base and collector regions (2, 3), implying that the device is suitable for high power applications. The doping concentration lies preferably between about 1019 and about 1020 at/cm3, and the thickness of the sub-region (2A) lies between 1 and 15 nm and preferably between 1 and 10 nm. The invention also comprises a method of manufacturing such a device (10).