Stepped-Trench Normally Off HEMT Gate Structure Against DIBL
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Solution Overview
Problem
High-electron-mobility transistors (HEMTs) of the normally on type face the issue of drain-induced barrier lowering (DIBL) phenomenon, leading to premature turning-on and increased leakage current at low drain-to-source voltages, which is not effectively addressed in existing solutions.
Innovation Solution
A HEMT transistor design featuring a semiconductor heterostructure with a trench and a conductive gate region coated by a dielectric material, where the trench is laterally delimited by a lateral structure forming a step, reducing the electrical field and preventing DIBL by distributing it evenly along the edges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a HEMT transistor is designed with a conventional gate structure, then the device can operate in normally off type, but the drain-induced barrier lowering (DIBL) phenomenon causes increased leakage current and premature turning-on
Solution Approach 1:
The gate structure is segmented into multiple gates positioned at different depths within the trench. The first gate is located at a first depth and the second gate is located at a second depth greater than the first depth, creating a multi-level gate configuration that segments the electrical field distribution and reduces DIBL effects
Solution Approach 2:
The invention transitions from a conventional single-plane gate structure to a three-dimensional multi-depth gate structure within the trench. By positioning gates at different vertical depths, the solution adds a depth dimension to the gate configuration, enabling better control of the electrical field distribution and reducing leakage current
2Ease of manufacture
If the trench structure is simplified without lateral structures, then manufacturing is easier, but the electrical field is not evenly distributed leading to DIBL phenomenon
Solution Approach 1:
The lateral structure is formed during the trench fabrication process itself, rather than as a separate subsequent step. The trench is etched with built-in lateral structures that define the trench boundaries and provide electrical field management, integrating the field distribution function into the primary fabrication process
Data Source
AI summary
A method forms an HEMT transistor of the normally off type, including: a semiconductor heterostructure, which comprises at least one first layer and one second layer, the second layer being set on top of the first layer; a trench, which extends through the second layer and a portion of the first layer; a gate region of conductive material, which extends in the trench; and a dielectric region, which extends in the trench, coats the gate region, and contacts the semiconductor heterostructure. A part of the trench is delimited laterally by a lateral structure that forms at least one first step. The semiconductor heterostructure forms a first edge and a second edge of the first step, the first edge being formed by the first layer.