Segmented Field Plate Structure for Transistor Gate-Drain Capacitance Reduction
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Solution Overview
Problem
Conventional transistor designs face challenges in reducing gate-to-drain capacitance, which affects performance and gain, due to manufacturing complexities and increased costs associated with implementing field plates as additional metal layers.
Innovation Solution
A segmented field plate design is implemented in a single metal layer between the transistor's gate and source or drain structures, forming fingers to connect with contact pads, simplifying fabrication and reducing capacitance, while allowing thermal measurements through notches or gaps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a field plate is implemented as an additional metal layer over the transistor device, then the gate-to-drain capacitance is reduced and breakdown voltage is increased, but the device complexity and manufacturing process are complicated, increasing overall device cost
Solution Approach 1:
The field plate is merged with the gate metallization layer, forming a continuous conductive structure that combines the gate and field plate functions into a single layer. This eliminates the need for an additional metal layer while maintaining the field plate's ability to increase breakdown voltage and reduce gate-to-drain capacitance.
Solution Approach 2:
The gate metallization layer is designed to serve dual functions: as the gate electrode for voltage application and as the field plate for electric field control. This multi-functionality approach allows the same structure to provide both transistor gating and field plate effects without requiring separate dedicated structures.
2Reliability
If a field plate is implemented as an additional metal layer over the transistor device, then the gate-to-drain capacitance is reduced, but the manufacturing process is complicated, increasing overall device cost
Solution Approach 1:
The field plate functionality is combined with the existing gate metallization layer, eliminating the need for an additional metal deposition and patterning step. This merging approach maintains the capacitance reduction benefit while simplifying the manufacturing process by using the already-formed gate layer.
Solution Approach 2:
The gate metallization layer is designed to perform both gate control and field plate functions simultaneously. This multi-functional design reduces the total number of manufacturing steps required, as the same layer provides both electrical gating and electric field management without requiring separate processing sequences.
3Ease of manufacture
If the field plate is formed as a single metal layer between gate and source structures, then the manufacturing process is simplified and device cost is reduced, but the field plate effectiveness may be compromised
Solution Approach 1:
The field plate structure is segmented into multiple regions within the single metal layer, including a first region extending from the gate structure and a second region extending from the source structure. These segments are electrically connected through the conductive layer, providing distributed field control that maintains effectiveness while using a single manufacturing layer.
Solution Approach 2:
The field plate is extended in the lateral dimension rather than using multiple stacked layers. By spreading the field plate functionality across a larger area in the plane of the single metal layer, the structure maintains its field control effectiveness without requiring vertical stacking of multiple metal layers.
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 approach improves transistor performance, particularly at RF frequencies, by reducing gate-to-source or gate-to-drain capacitance, simplifying the manufacturing process, and enabling cost-effective production with enhanced thermal measurement capabilities.
Implementation Method 1
the field plate operates to increase the breakdown voltage and reduce the inter-electrode capacitance of the transistor by redistributing the electric field at the gate edge of the transistor such that the gate-drain voltage is dropped across the dielectric layer instead of the semiconductor surface
Implementation Method 2
The conductor is electrically isolated from the substrate of the transistor by a dielectric or insulative layer
Data Source
AI summary
A device includes a transistor formed over a substrate. The transistor includes a source structure, a drain structure, and a gate structure. A dielectric layer is formed over the transistor, and a plurality of vias are electrically connected to the source structure. A metal layer is formed over the dielectric layer. The metal layer includes a field plate over the gate structure, a plurality of contact pads over each via, and a plurality of fingers interconnecting each one of the plurality of contact pads to the field plate.