Composite Gate Dielectric for Uniform High-Voltage Transistor Threshold
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Solution Overview
Problem
High-voltage transistors suffer from performance defects due to manufacturing integration with low-voltage transistors, particularly the subthreshold hump effect causing non-uniform threshold voltage and increased subthreshold swing and leakage current at the edges of the channel region.
Innovation Solution
Implementing a composite gate dielectric layer with regions of varying dielectric constants and a composite gate structure with varying work function values to achieve uniform threshold voltage across the channel region, compensating for the subthreshold hump effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-voltage transistors are manufactured using standard integration processes with low-voltage transistors, then manufacturing efficiency is improved, but threshold voltage uniformity deteriorates due to the subthreshold hump effect at channel edges
Solution Approach 1:
The patent applies local quality by creating a composite gate dielectric layer with different dielectric materials in different regions. Specifically, a first dielectric material with higher dielectric constant is placed at channel edges while a second dielectric material with lower dielectric constant is placed at channel centers. This spatial variation in dielectric properties compensates for the subthreshold hump effect at edges without affecting center performance, thereby maintaining threshold voltage uniformity across the entire channel while using standard manufacturing processes.
2Area of moving object
If the transistor size is reduced to improve integration density, then area is improved, but leakage current increases due to enhanced subthreshold swing effects
Solution Approach 1:
The composite gate dielectric structure addresses leakage current by locally modifying the dielectric constant at channel edges where subthreshold swing effects are most pronounced. The higher dielectric constant material at edges provides stronger electric field control, suppressing leakage current in these critical regions. This allows transistor dimensions to be reduced for higher integration density without proportionally increasing leakage, as the edge regions are specifically optimized to maintain low off-state current.
3Device complexity
If a uniform gate dielectric layer is used to simplify manufacturing, then device complexity is reduced, but threshold voltage control precision deteriorates due to non-uniform electric field distribution
Solution Approach 1:
The patent implements local quality through a composite gate dielectric layer comprising multiple dielectric materials with different constants positioned at specific locations. The first dielectric material (higher k-value) is positioned at channel edges while the second dielectric material (lower k-value) is positioned at channel centers. This spatially-resolved approach creates a non-uniform electric field distribution that compensates for the subthreshold hump effect, achieving precise threshold voltage control without requiring complex manufacturing processes.
Solution Approach 2:
The gate dielectric layer employs composite materials by combining multiple dielectric materials with different dielectric constants in a single layer structure. This composite approach allows the structure to exhibit different electrical properties at different locations, with the higher-k material at edges providing enhanced field control and the lower-k material at centers maintaining standard performance, thereby achieving precise threshold voltage control through material composition rather than structural complexity.
Data Source
AI summary
A high-voltage transistor may include a composite gate dielectric layer having multiple regions with different dielectric constant values and/or a composite gate structure having multiple regions of different work function values. The composite dielectric layer having multiple regions with different dielectric constant values and/or the composite gate structure having multiple regions with different work functions increases the threshold voltage uniformity across a channel region of the high-voltage transistor. The increased threshold voltage uniformity may enable a low subthreshold swing and a low subthreshold off-stage current leakage to be achieved for the high-voltage transistor, which increases the operating efficiency of the high-voltage transistor and enables the size of the high-voltage transistor to be reduced without increasing (or with minimal increase to) the subthreshold swing and and/or the subthreshold off-stage current leakage of the high-voltage transistor.