Transistor With High Breakdown Voltage Using Pitch Multiplication
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Solution Overview
Problem
Current methods for forming transistors with high breakdown voltage face challenges in integrating with low voltage circuitry due to high resistivity and limited breakdown voltage characteristics, necessitating the development of more effective semiconductor fabrication techniques.
Innovation Solution
The use of pitch multiplication to form transistors with narrow and denser active area strips through the creation of sacrificial mandrels, spacer formation, and shallow trench isolation (STI) structures, which reduce peak electric-field at transistor junctions and increase breakdown voltage without altering transistor size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If transistors are formed in a thick and low-doped epitaxial layer to achieve high breakdown voltage, then breakdown voltage is improved, but resistivity increases making integration with low voltage circuitry difficult
Solution Approach 1:
The transistor structure is segmented into distinct doped regions: a first doped region at the source, a second doped region at the drain, and a third doped region in the middle of the channel. This segmentation allows different parts of the transistor to have different doping concentrations, enabling the channel region to maintain low resistivity for good electrical contact while the source and drain regions provide high breakdown voltage characteristics.
Solution Approach 2:
Different regions of the transistor are given different local properties through selective doping. The channel region has lower doping concentration to reduce resistivity and improve electrical contact, while the source and drain regions have higher doping concentration to provide high breakdown voltage. This local differentiation resolves the contradiction between low resistivity and high breakdown voltage.
2Reliability
If a shallow, elongated N-type region is formed to take advantage of the DIELER effect, then breakdown voltage is improved with relatively low resistivity, but higher breakdown voltage characteristics are still desirable
Solution Approach 1:
The transistor structure is segmented into distinct doped regions: a first doped region at the source, a second doped region at the drain, and a third doped region in the middle of the channel. This segmentation allows different parts of the transistor to have different doping concentrations, enabling the channel region to maintain low resistivity for good electrical contact while the source and drain regions provide high breakdown voltage.
Solution Approach 2:
Different regions of the transistor are given different local properties through selective doping. The channel region has lower doping concentration to reduce resistivity and improve electrical contact, while the source and drain regions have higher doping concentration to provide high breakdown voltage. This local differentiation resolves the contradiction between low resistivity and high breakdown voltage.
Data Source
AI summary
Transistors are formed using pitch multiplication. Each transistor includes a source region and a drain region connected by strips of active area material separated by shallow trench isolation (STI) structures, which are formed by dielectric material filling trenches formed by pitch multiplication. During pitch multiplication, rows of spaced-apart mandrels are formed and spacer material is deposited over the mandrels. The spacer material is etched to define spacers on sidewalls of the mandrels. The mandrels are removed, leaving free-standing spacers. The spacers constitute a mask, through which an underlying substrate is etched to form the trenches and strips of active area material. The trenches are filled to form the STI structures. The substrate is doped, forming source, drain and channel regions. A gate is formed over the channel region. In some embodiments, the STI structures and the strips of material facilitate the formation of transistors having a high breakdown voltage.