Trench Gate FET Layout for Parasitic Bipolar Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing field effect transistors (FETs) face challenges in optimizing area-specific on-state resistance (RonxA) while ensuring reliability, particularly due to trade-offs with avalanche breakdown behavior.
Innovation Solution
The FET design incorporates a trench gate structure with a body contact region arranged such that the vertical or lateral distances between the body contact and source regions are optimized, reducing voltage drop and suppressing parasitic bipolar transistor triggering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If device geometries are shrunk to reduce costs and increase device functionalities per unit area, then productivity and area utilization are improved, but reliability deteriorates due to avalanche breakdown behavior
Solution Approach 1:
The body contact region is segmented into multiple doping zones with different conductivity types and concentrations. This segmentation allows different regions to perform different functions: some regions suppress parasitic bipolar transistors while others maintain low on-state resistance, thus resolving the contradiction between reliability and productivity
Solution Approach 2:
Different regions of the body contact are assigned different doping characteristics. Regions adjacent to the trench gate have specific doping profiles to suppress parasitic effects, while other regions are optimized for conductivity. This local differentiation enables simultaneous achievement of high reliability and high device density
2Reliability
If area-specific on-state resistance is reduced to improve device performance, then conductivity is improved, but reliability deteriorates due to increased parasitic bipolar transistor triggering
Solution Approach 1:
The body contact structure is designed with preliminary anti-action against parasitic bipolar transistor formation. By strategically placing doping regions with opposite conductivity types in specific locations, the design preemptively suppresses parasitic transistor triggering before it can occur during device operation, thus maintaining reliability while allowing optimized on-state resistance
Solution Approach 2:
Intermediate doping regions are introduced as mediators between the source/drain regions and the body contact. These intermediate regions with controlled doping profiles act as buffers that prevent parasitic bipolar transistor formation while maintaining electrical connectivity, thus resolving the contradiction between low on-state resistance and high reliability
Data Source
AI summary
A FET includes a transistor cell which includes: a source region at a first surface of a semiconductor substrate; a drain region spaced along a first lateral direction from the source region; a trench gate structure arranged, along the first lateral direction, between the source and drain regions; a body region adjoining the trench gate structure; and a body contact region. At least one of the following conditions is satisfied: a first vertical distance from the body contact region bottom side to a vertical reference level at the first surface is larger than a second vertical distance from the source region bottom side to the vertical reference level; and a first lateral distance from an edge of the body contact region to a lateral reference level at the drain region is smaller than a second lateral distance from an edge of the source region to the lateral reference level.