HEMT Field Plate Capacitance Reduction via Segmented Mask
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Solution Overview
Problem
The existing field plate configurations in high electron mobility transistors (HEMTs) generate capacitance between the field plate and the gate electrode, leading to deteriorated electrical characteristics due to the insulating film, which needs to be reduced.
Innovation Solution
A method of manufacturing a semiconductor device where a field plate is formed with a specific mask configuration, extending from the side surface of a step to a flat portion on the insulating film, ensuring one end is on the drain electrode side relative to the gate electrode edge, and having a reduced thickness towards the drain electrode, thereby minimizing capacitance between the field plate and the gate electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a field plate is provided on an insulating film covering the gate electrode, then the shielding effect between drain and gate electrodes is improved, but capacitance is generated between the field plate and gate electrode leading to deteriorated electrical characteristics
Solution Approach 1:
The field plate is divided into multiple sections: a first field plate portion extending from the drain electrode to cover the gate electrode, and a second field plate portion extending from the first field plate portion to the insulating film. This segmentation allows the field plate to provide shielding coverage while reducing direct capacitance coupling between the gate electrode and the field plate by introducing intermediate structures and spacing.
Solution Approach 2:
The field plate structure extends in multiple dimensions: laterally to provide coverage, and vertically with varying thickness. The thickness of the field plate is designed to vary, being thicker near the drain electrode and thinner near the gate electrode, creating a gradient structure that reduces capacitance while maintaining shielding effectiveness.
2Object-affected harmful factors
If the field plate extends over the gate electrode to provide shielding, then coupling between drain and gate is reduced, but capacitance between field plate and gate electrode increases
Solution Approach 1:
Different portions of the field plate have different thicknesses and extensions. The first field plate portion has a greater thickness and extends further to provide strong shielding near the drain electrode, while the second field plate portion has a reduced thickness and limited extension to minimize capacitance near the gate electrode. This local variation in structure optimizes both shielding and capacitance reduction.
Solution Approach 2:
The field plate provides partial coverage over the gate electrode rather than complete coverage. The second field plate portion extends only partially from the first field plate portion to the insulating film, providing just enough shielding in the critical region while avoiding excessive extension that would increase capacitance.
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 configuration effectively reduces the capacitance between the field plate and the gate electrode while maintaining the shielding effect between the drain and gate electrodes, improving the electrical characteristics of the HEMT.
Implementation Method 1
depositing a metal material on the insulating film using the resist as a mask to form a field plate
Data Source
AI summary
A method of manufacturing a semiconductor device includes processes of forming a gate electrode, a source electrode, and a drain electrode on a nitride semiconductor layer, forming an insulating film including, on a surface thereof, a step that covers the gate electrode and reflects a shape of the gate electrode, and a flat portion, forming a mask on the insulating film, forming an opening in the mask, the opening including a shape in which a side surface of the step is located on an inner side of the opening and an upper surface end portion of the gate electrode is located on an outer side of the opening, and having an overhang shape extending in a depth direction, and forming a field plate extending from a side surface of the step to the flat portion using the mask.