Transistor Extension Regions With Alternating Conductivity Strips
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Solution Overview
Problem
Transistors with high breakdown voltages often require multiple doping steps, leading to increased fabrication costs and inconsistent breakdown voltage levels, as a single doping step may optimize for one transistor but result in inadequate breakdown voltage for another, necessitating compromises that reduce maximum breakdown voltage performance.
Innovation Solution
The formation of transistors with extension regions featuring alternating strips of differing conductivity types, where n-type and p-type strips are concurrently doped during the same processing step, allowing for enhanced breakdown voltage performance without additional processing steps, by creating a plurality of p-n junctions that shift the doping curve to higher levels, enabling a single doping level to achieve sufficient breakdown voltage for multiple transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple doping steps are used to optimize breakdown voltage for different transistors, then each transistor can achieve its optimal breakdown voltage, but fabrication costs increase due to additional processing steps
Solution Approach 1:
The patent applies local quality by creating alternating n-type and p-type strips within the extension region, where different local areas have different doping types. This allows the structure to achieve higher breakdown voltage through multiple p-n junctions while using a single doping step process, resolving the contradiction between reliability and ease of manufacture
Solution Approach 2:
The extension region uses composite doping structure with alternating n-type and p-type strips, creating a composite material system that combines the benefits of different conductivity types in a single region. This composite structure enables high breakdown voltage without requiring multiple separate doping steps
2Ease of manufacture
If a single doping level is used for all transistors, then fabrication costs are reduced, but breakdown voltage performance is compromised for transistors that require higher breakdown voltage
Solution Approach 1:
The extension region is segmented into alternating n-type and p-type strips, creating multiple discrete doping regions within a single continuous structure. This segmentation allows the single doping step to create multiple p-n junctions that collectively provide the high breakdown voltage needed, resolving the contradiction between ease of manufacture and reliability
Solution Approach 2:
The patent changes the doping parameter from a uniform single doping level to alternating doping types (n-type and p-type) within the same extension region. This parameter change enables the structure to achieve higher breakdown voltage through multiple junctions while maintaining a single doping step process
3Reliability
If the doping is adjusted to a compromise level, then all transistors have sufficient breakdown voltage, but the maximum breakdown voltage performance is reduced
Solution Approach 1:
The patent adds a dimensional aspect by creating alternating strips in the extension region, transforming a one-dimensional doping profile into a multi-layered alternating structure. This dimensional change creates multiple p-n junctions that enhance breakdown voltage without requiring compromise doping levels
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 allows for a single doping level to achieve peak breakdown voltage across multiple transistors, reducing fabrication costs and ensuring consistent performance by shifting the doping curve to higher levels through the creation of lateral electric fields in the p-type strips between n-type strips, thereby enhancing depletion in the extension regions.
Implementation Method 1
by creating a plurality of p-n junctions that shift the doping curve to higher levels, enabling a single doping level to achieve sufficient breakdown voltage for multiple transistors
Implementation Method 2
thereby enhancing depletion in the extension regions
Data Source
AI summary
A transistor includes a gate dielectric over a semiconductor having a first conductivity type, a control gate over the gate dielectric, source and drain regions having a second conductivity type in the semiconductor having the first conductivity type, and strips having the second conductivity type within the semiconductor having the first conductivity type and interposed between the control gate and at least one of the source and drain regions.