Self-Aligned GaN Field Plates for Breakdown and Capacitance Control
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Solution Overview
Problem
There is a need for semiconductor devices, particularly gallium nitride (GaN) devices, with field plates to reduce gate-drain feedback capacitance and increase breakdown voltage in high-frequency transistors.
Innovation Solution
A method of fabricating a semiconductor device that includes depositing electrically conductive material over a dielectric layer on a semiconductive substrate. The method forms first, second, and third conductive elements above the channel region, with the second conductive element between the first and third. A field plate interconnect is formed by creating apertures in dielectric layers and depositing electrically conductive material to contact the conductive elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If field plates are added to reduce gate-drain feedback capacitance and increase breakdown voltage, then device performance is improved, but device complexity increases
Solution Approach 1:
The field plate structure is merged with the gate electrode, forming an integrated gate-field plate assembly. The field plate is electrically connected to the gate through a conductive path, allowing both the gate control function and the field plate function (reducing feedback capacitance and increasing breakdown voltage) to be achieved within a unified structure, thereby improving reliability without proportionally increasing device complexity
Solution Approach 2:
The gate electrode serves multiple functions: it provides the primary gate control function for the transistor and simultaneously acts as part of the field plate structure that reduces gate-drain feedback capacitance and increases breakdown voltage. This multi-functionality approach allows a single structure to address multiple performance requirements, improving reliability while minimizing the increase in device complexity
2Reliability
If field plates are added to reduce gate-drain feedback capacitance and increase breakdown voltage, then device performance is improved, but manufacturing complexity increases
Solution Approach 1:
The field plate structure is formed during the same fabrication process steps as the gate electrode, using preliminary patterning and deposition. The conductive material for both the gate and field plate is deposited and patterned in advance, before final device assembly, which simplifies the manufacturing process by avoiding additional complex steps
Solution Approach 2:
The fabrication process for the gate electrode and field plate is merged into a single integrated process flow. The same conductive material deposition and patterning steps that create the gate electrode also create the field plate structure, reducing the total number of manufacturing steps and simplifying production while achieving the desired performance improvements
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
The fabricated semiconductor device provides an electrically conductive path between current terminals via the channel region, enhancing breakdown voltage and reducing gate-drain feedback capacitance, thus improving the performance of high-frequency transistors.
Implementation Method 1
The control electrode extends within the first aperture and is configured to be electrically coupled to the channel region
Implementation Method 2
The first electrode extension and the field electrode are each formed from the same electrically conductive material
Data Source
AI summary
Placement of a field plate in a field-effect transistor is optimized by using multiple dielectric layers such that a first end of field plate is separated from a channel region of the transistor by a first set of one or more distinct dielectric material layers. A second end of the field plate overlies the channel region and a control electrode from which it is separated by the first set of dielectric layers and one or more additional dielectric layers. Relative positioning of the control electrode and the field plate are determined by a single processing step such that the field plate is self-aligned to the control electrode in order to reduce variations in transistor performance associated with manufacturing process variations.