Floating-Liner Isolation Trenches for High-Voltage Transistors
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Solution Overview
Problem
Current memory devices face challenges in achieving optimal breakdown voltage and transistor voltage modulation due to limitations in isolation trench width and depth, which affect the performance of memory arrays, especially in high-voltage operations.
Innovation Solution
Incorporating a floating liner in the isolation trench between transistors, which is doped with a semiconductor material, enhances the breakdown voltage and allows for narrower trench widths and reduced depths, improving voltage modulation and transistor performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the isolation trench width and depth are increased to achieve optimal breakdown voltage, then the breakdown voltage improves, but the transistor voltage modulation deteriorates
Solution Approach 1:
The isolation trench is segmented into multiple functional regions: a first portion filled with dielectric material and a second portion filled with doped polysilicon. This segmentation allows each region to contribute differently to the overall performance, with the dielectric providing isolation and the doped polysilicon enhancing breakdown voltage while maintaining voltage modulation capability.
Solution Approach 2:
The isolation trench employs a composite structure combining dielectric material and doped polysilicon. This composite approach leverages the high breakdown voltage characteristics of doped polysilicon while maintaining the electrical isolation properties of the dielectric, thereby resolving the contradiction between achieving high breakdown voltage and maintaining good voltage modulation.
2Ease of operation
If the isolation trench width is reduced to improve transistor voltage modulation, then the voltage modulation improves, but the breakdown voltage deteriorates
Solution Approach 1:
By dividing the isolation trench into distinct segments with different materials, the design achieves narrow overall width for good voltage modulation while the doped polysilicon segment provides enhanced breakdown voltage protection, preventing the deterioration that would normally occur with reduced width.
Solution Approach 2:
Different regions of the isolation trench are assigned different material qualities: the dielectric region provides isolation and the doped polysilicon region provides high breakdown voltage. This local differentiation allows the narrow trench to maintain both good voltage modulation and adequate breakdown voltage.
3Reliability
If the isolation trench depth is increased to achieve optimal breakdown voltage, then the breakdown voltage improves, but the manufacturing complexity increases
Solution Approach 1:
The invention changes the material parameter (using doped polysilicon instead of pure dielectric) in the deeper portion of the trench, allowing for reduced overall depth while maintaining breakdown voltage. The doped polysilicon's superior electrical properties enable shallower trench designs compared to conventional dielectric-only approaches.
Solution Approach 2:
The composite filling structure with doped polysilicon in the second portion enables achievement of optimal breakdown voltage with reduced trench depth, thereby lowering manufacturing complexity while maintaining reliability.
4Ease of manufacture
If conventional dielectric material is used in the isolation trench, then the manufacturing process is simple, but the breakdown voltage is insufficient
Solution Approach 1:
The isolation trench uses a composite structure where doped polysilicon replaces part of the conventional dielectric material. This substitution maintains manufacturing feasibility through standard semiconductor processes while dramatically improving breakdown voltage characteristics.
Solution Approach 2:
The invention changes the material parameter from pure dielectric to doped polysilicon in the second portion of the trench, transforming the electrical properties to achieve higher breakdown voltage while keeping the manufacturing process within existing technological capabilities.
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 inclusion of a floating liner significantly increases breakdown voltage and enables more efficient transistor operation, particularly beneficial for high-voltage applications like NAND memory arrays, by allowing narrower isolation trenches and improved voltage modulation.
Implementation Method 1
it has been discovered that the formation of a doped polysilicon liner in an isolation trench can increase breakdown voltage
Implementation Method 2
improve voltage modulation with respect to adjacent transistors
Data Source
AI summary
Apparatus and methods are disclosed, including transistors, semiconductor devices and systems. Example semiconductor devices and methods include isolation trenches between transistors that include a floating liner. Floating liner examples enable trench widths that scale smaller than trenches that do not include floating liners. This allows increases in device density without sacrificing electronic properties of devise shown.