Nitride FET Field Plate Charge Dissipation via Auxiliary Region
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Solution Overview
Problem
Field plates in nitride semiconductor FETs can accumulate excessive charges during processing, leading to electrostatic discharge and short circuits between the field plate and gate electrode, rendering the device inoperable due to their electrical isolation from conductive materials.
Innovation Solution
The field plate is electrically connected to the auxiliary active region through an opening in the insulating film, allowing charges to be discharged into the semiconductor stack, preventing accumulation and reducing the risk of short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the field plate is formed by metal evaporation and lift-off process, then the field plate can be independently formed on the insulating film, but charges accumulate excessively in the field plate causing electrostatic discharge and short circuit
Solution Approach 1:
The field plate is merged with the source electrode by forming them as a single integrated structure. The source electrode is extended to overlap with the gate electrode, eliminating the need for a separate field plate structure. This integration ensures electrical continuity and prevents charge accumulation while maintaining the field modulation function.
Solution Approach 2:
The source electrode is given dual functionality: it serves both as the electrical contact for the source region and as the field plate structure that modulates the electric field near the gate electrode. This multi-functionality eliminates the separate field plate component while preserving its essential role in preventing current collapse and suppressing coupling.
2Object-generated harmful factors
If the field plate is electrically isolated on the insulating film, then the field plate can suppress coupling between drain and gate, but charges cannot be discharged causing arc discharge to gate electrode
Solution Approach 1:
The field plate function is merged into the source electrode structure. The source electrode is extended laterally to overlap with the gate electrode, creating an integrated structure that provides both electrical connection and field modulation. This eliminates the isolated field plate that accumulates charges while maintaining the coupling suppression function.
Solution Approach 2:
The insulating film serves as an intermediary that allows the source electrode to overlap with the gate electrode spatially while maintaining electrical isolation where needed. The insulating film enables the field modulation function while the direct connection to the source electrode provides the charge dissipation path.
3Ease of manufacture
If solvent jet spray is used to remove residual metals, then the lift-off process is effective, but friction accumulates charges in the field plate excessively
Solution Approach 1:
The field plate and source electrode are formed as a single integrated structure through direct deposition and patterning, eliminating the need for a separate lift-off process. This integration removes the field plate from the lift-off process entirely, preventing charge accumulation during solvent spray while maintaining manufacturing effectiveness.
Solution Approach 2:
The source electrode and field plate structure are formed simultaneously in a single deposition and patterning step, before any lift-off process is needed. This preliminary integration eliminates the subsequent lift-off step that would otherwise cause charge accumulation during solvent removal.
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 prevents excessive charge accumulation in the field plate, reducing the likelihood of arced discharges and maintaining device functionality by ensuring charges are dissipated, thereby enhancing the reliability and operational stability of the FET.
Implementation Method 1
A FET primarily made of nitride semiconductor materials often provides a field plate partially overlapping with a gate electrode interposing an insulating film therebetween to moderate field strength induced in an edge of the gate electrode
Implementation Method 2
The field plate may also suppress reduction in a drain current due to, what is called, current collapse inherently attributed to a nitride semiconductor device
Implementation Method 3
A field plate may further show a function to suppress coupling between a drain electrode and a gate electrode
Implementation Method 4
when the lift-off process to remove the residual metals left on the mask uses a jet spray of solvents against the mask, the solvents sprayed onto the field plate may cause a friction and accumulate charges in the field plate
Implementation Method 5
Excessively accumulated charges sometimes cause arc discharge against the gate electrode to make a short circuit thereto
Data Source
AI summary
A semiconductor device type of field effect transistor (FET) primarily made of nitride semiconductor materials is disclosed. The FET includes a nitride semiconductor stack providing primary and auxiliary active regions and an inactive region surrounding the active regions; electrodes of a source, a drain, and a gate; an insulating film covering the electrodes and the semiconductor stack; and a field plate on the insulating film. A feature of the FET of the invention is that the field plate is electrically in contact with the auxiliary active region through the opening provided in the insulating film.