CMOS MOSFET Isolation Structure for Leakage and Latch-Up Control
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Solution Overview
Problem
Current CMOS technologies face challenges with increased current leakage and latch-up issues due to scaling down of device geometries, which leads to difficulties in controlling channel length, junction leakage, and parasitic Metal-Gated-Diode formation, necessitating larger planar areas for isolation and increased die size.
Innovation Solution
A complementary MOSFET structure with cross-shape localized isolation regions, including horizontally and vertically extended isolation regions, is implemented to minimize current leakage and latch-up, using lightly and heavily doped semiconductor regions with a seamless crystalline lattice structure, and metal-containing regions to enhance channel conduction and reduce planar area usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If device geometries are scaled down to advance CMOS technology, then transistor density and integration are improved, but current leakage and latch-up issues worsen
Solution Approach 1:
The patent introduces a cross-shaped isolation structure that extends in multiple dimensions (horizontal and vertical) from the substrate surface. This multi-dimensional isolation approach blocks parasitic current paths that occur when devices are scaled down, effectively addressing leakage and latch-up issues while maintaining high transistor density through compact layout.
Solution Approach 2:
The isolation structure is strategically positioned at specific locations where n+ and p+ regions interface with the substrate, creating localized isolation zones. This targeted approach provides precise control over current leakage paths without requiring global increases in isolation dimensions, thus maintaining device scaling benefits while improving reliability.
2Reliability
If larger planar areas are used for isolation to prevent latch-up, then latch-up immunity is improved, but die size increases
Solution Approach 1:
The cross-shaped isolation structure utilizes vertical extension into the substrate in addition to horizontal spreading, creating a three-dimensional isolation barrier. This multi-dimensional approach provides effective latch-up prevention with a smaller planar footprint compared to traditional two-dimensional isolation schemes, thus reducing die size while maintaining reliability.
Solution Approach 2:
The isolation structure combines multiple materials including silicon substrate, silicon dioxide, and silicon nitride in a composite configuration. This composite material approach provides superior electrical isolation properties and mechanical stability, enabling effective latch-up prevention with optimized material usage and reduced overall isolation area.
Data Source
AI summary
The present invention provides a new complementary MOSFET structure with localized isolations in silicon substrate to reduce leakages and prevent latch-up. The complementary MOSFET structure comprises a semiconductor wafer substrate with a semiconductor surface, a P type MOSFET comprising a first conductive region, a N type MOSFET comprising a second conductive region, and a cross-shape localized isolation region between the P type MOSFET and the N type MOSFET. Wherein, the cross-shape localized isolation region includes a horizontally extended isolation region below the semiconductor surface, and the horizontally extended isolation region contacts to a bottom side of the first conductive region and a bottom side of the second conductive region.