GaN HEMT Substrate Layout for Back-Gate On-Resistance Stability
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Solution Overview
Problem
The application of a negative voltage to the back surface of the high-side element in a half-bridge circuit with GaN HEMTs increases the on-resistance due to an effective back gate effect when the low-side element is off.
Innovation Solution
A semiconductor device design featuring a substrate with a lattice-shaped first conductive member and nitride semiconductor elements separated by an insulating member, where the source potential is applied through conductive members to stabilize operation, and a field plate effect is applied from the backside to relax the electric field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a half-bridge circuit including two GaN HEMTs is formed on the same wafer, then circuit integration is achieved, but negative voltage applied to the back surface of the high-side element increases on-resistance due to back gate effect
Solution Approach 1:
The substrate surface is divided into multiple regions with different conductive members (first conductive member for high-side element, second conductive member for low-side element). This segmentation allows independent potential control of each element's substrate region, preventing the back gate effect from affecting the high-side element when the low-side element is off.
Solution Approach 2:
Conductive members are used to maintain equipotential regions on the substrate surface beneath each nitride semiconductor element. By keeping the substrate potential constant under the high-side element, the invention eliminates voltage variations that would otherwise cause back gate effects and on-resistance changes.
2Reliability
If conductive members are added to fix substrate potential, then back gate effect is suppressed, but device structure becomes more complex
Solution Approach 1:
The conductive members are integrated with the existing circuit structure, serving dual purposes: they are part of the electrical connection network and simultaneously function as potential-fixing elements to suppress back gate effects. This merging approach adds functionality without proportionally increasing structural complexity.
Solution Approach 2:
The conductive members perform multiple functions: they provide electrical connections for the circuit operation and simultaneously act as equipotential maintaining structures to prevent back gate effects. This multi-functionality reduces the need for additional dedicated components.
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
Suppresses the increase in on-resistance and stabilizes the operation of nitride semiconductor elements by fixing the substrate potential, reducing the impact of back gate effects and enhancing breakdown voltage.
Implementation Method 1
a field plate effect is applied from the backside to relax the electric field
Implementation Method 2
the source potential is applied through conductive members to stabilize operation
Data Source
AI summary
A semiconductor device includes a substrate; a first conductive member located on a portion of a surface of the substrate; a plurality of nitride semiconductor layers located on the substrate and on the first conductive member, the plurality of nitride semiconductor layers being separated from each other; a source electrode located on each of the nitride semiconductor layers; a drain electrode located on each of the nitride semiconductor layers; a gate electrode located on each of the nitride semiconductor layers; and a second conductive member extending between the first conductive member and the source electrode inside each of the nitride semiconductor layers, the second conductive member being electrically connected to the first conductive member and the source electrode.