SiGe Heterojunction Bipolar Transistor Strain Engineering
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Solution Overview
Problem
As semiconductor devices shrink, their current drive capability and high-frequency performance are compromised by increased chip delay and 1/f noise, and the SiGe HBT process is limited by long development cycles and high costs due to instability and incompatibility with CMOS processes.
Innovation Solution
A heterojunction bipolar transistor design using a P-type doped single crystal Si substrate with specific epitaxial layers and strain engineering, including a buried layer, collector region, and embedded SiGe structure, optimized for reduced parasitic effects and improved frequency characteristics, fully compatible with the 90-nm CMOS process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If device size is decreased to improve integration density, then productivity increases, but high-frequency performance deteriorates due to increased 1/f noise and chip delay
Solution Approach 1:
The patent employs a heterojunction structure combining different semiconductor materials (e.g., SiGe/Si or III-V/Si) to create a bipolar transistor that maintains high-frequency performance at reduced device sizes. The composite material approach allows exploitation of superior carrier mobility in the heterojunction region while keeping the device footprint small, thereby resolving the contradiction between integration density and high-frequency performance.
2Reliability
If SiGe HBT process is used to improve high-frequency characteristics, then frequency performance increases, but manufacturing cost and development cycle increase due to process instability and incompatibility with CMOS
Solution Approach 1:
The patent merges SiGe HBT technology with CMOS process compatibility by integrating the bipolar transistor fabrication into the existing CMOS manufacturing flow. This combination allows simultaneous production of both CMOS and SiGe HBT devices on the same wafer using shared process steps, thereby reducing manufacturing cost and development cycle while maintaining superior high-frequency characteristics.
Solution Approach 2:
The patent creates a universal fabrication process that can produce both standard CMOS devices and high-performance SiGe HBT devices using the same manufacturing infrastructure. The process design enables multi-functionality where a single fabrication line can switch between producing different device types, eliminating the need for separate specialized production lines and reducing overall manufacturing complexity and cost.
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 design enhances carrier mobility and frequency characteristics by reducing intrinsic resistance and collector junction capacitance, while being cost-effective and compatible with existing CMOS processes, thus overcoming the limitations of previous SiGe HBT technologies.
Implementation Method 1
the N- doped collector region is ion implanted to form the P+ doped on both sides as a non-intrinsic base region
Implementation Method 2
a N+ doped single crystal Si layer is epitaxially formed on the single crystal Si substrate as a buried layer
Implementation Method 3
an N- doped single crystal Si layer is epitaxially formed on the surface of the buried layer as a collector region
Implementation Method 4
a P-type SiGe layer base region, an intrinsic Si cap layer and a N+ doped polycrystalline Si layer emitter region are selective epitaxially formed in the active region
Data Source
AI summary
The disclosure provides a heterojunction bipolar transistor and a preparation method thereof. Since an emitter region has the same physical structure as a base region, and improves frequency characteristics of the device; Simultaneously with biaxial strain, uniaxial strain is introduced. Carrier transmission time in the collector region will be effectively reduced. By this structure, the width of the effective collector region is reduced, the collector junction capacitance is reduced, and the frequency characteristics of the device are further improved; an appropriate choice of the thickness of the Si cap layer can effectively reduce the accumulation of carriers at an interface and increase the gain of the device; at the same time, the preparation method of the bipolar transistor is completely compatible with a 90-nanometer CMOS process, which effectively reduces the development and manufacturing cost of the device.