Trench Isolation for Latch-Up Suppression in Bulk CMOS
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Bulk CMOS devices are susceptible to latch-up due to the close proximity of N-channel and P-channel transistors, leading to regenerative feedback and potential catastrophic failure, especially in radiation environments, with existing solutions like epitaxial substrates and guard ring diffusions being costly or complex.
Innovation Solution
The introduction of a semiconductor structure with doped wells and a dielectric-filled trench between them, where the trench's geometry and sidewall spacing are modified to increase carrier recombination velocity and disrupt the continuity of non-monocrystalline semiconductor material, creating an isolation region that limits parasitic transistor action.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If guard ring diffusions are used to suppress latch-up, then latch-up immunity is improved, but manufacturing cost increases and active area is reduced
Solution Approach 1:
The patent replaces expensive guard ring diffusions with a simpler trench isolation structure that uses standard dielectric materials and conventional fabrication processes, significantly reducing manufacturing cost while maintaining latch-up suppression functionality
Solution Approach 2:
The patent extracts the essential function of carrier collection from the complex guard ring diffusion structure and implements it through a simplified trench isolation approach, removing unnecessary structural complexity while preserving the latch-up immunity function
2Reliability
If guard ring diffusions are used to suppress latch-up, then latch-up immunity is improved, but active area is reduced
Solution Approach 1:
The trench isolation structure occupies minimal space compared to extensive guard ring diffusions, preserving maximum active area for functional circuit elements while providing effective latch-up suppression through the dielectric-filled trench
Solution Approach 2:
The patent applies latch-up suppression locally at critical interfaces between N-well and P-substrate using targeted trench isolation, rather than using extensive guard rings across the entire device area, thus maximizing active area utilization
3Reliability
If epitaxial substrates are used to increase latch-up immunity, then latch-up immunity is improved, but production cost and design complexity increase
Solution Approach 1:
The patent extracts the latch-up immunity function from complex epitaxial substrate requirements and implements it through a simpler structure using standard bulk CMOS substrates with trench isolation, reducing both production cost and design complexity
Solution Approach 2:
The patent changes the approach from modifying substrate properties (epitaxial layers) to modifying device structure (trench isolation geometry), allowing standard substrates to achieve enhanced latch-up immunity without increasing design complexity
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 effectively reduces latch-up susceptibility in bulk CMOS devices by impeding minority carrier flow and reducing bipolar gain, thereby enhancing device immunity to latch-up without increasing production costs or complexity.
Implementation Method 1
the trench's geometry and sidewall spacing are modified to increase carrier recombination velocity and disrupt the continuity of non-monocrystalline semiconductor material
Data Source
AI summary
Semiconductor structures and methods for suppressing latch-up in bulk CMOS devices. The semiconductor structure comprises a shaped-modified isolation region that is formed in a trench generally between two doped wells of the substrate in which the bulk CMOS devices are fabricated. The shaped-modified isolation region may comprise a widened dielectric-filled portion of the trench, which may optionally include a nearby damage region, or a narrowed dielectric-filled portion of the trench that partitions a damage region between the two doped wells. Latch-up may also be suppressed by providing a lattice-mismatched layer between the trench base and the dielectric filler in the trench.