High Voltage Transistor Field Structure with Conduction Units
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Solution Overview
Problem
High voltage transistor devices face challenges in achieving optimal breakdown voltages due to burdensome gate-to-drain capacitance and increased fabrication costs associated with existing field plate formation methods, which either worsen switching losses or require additional processing steps.
Innovation Solution
A high voltage transistor device with a field structure incorporating vertically elongated conduction units made from conductive material, formed concurrently with metal contacts or vias, which reduces parasitic capacitance and fabrication costs by allowing for a low-cost method of fabrication and flexible design configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If field plates are formed by extending conductive gate material from gate electrode towards drift region, then breakdown voltage capability is improved, but gate-to-drain capacitance increases and switching losses worsen
Solution Approach 1:
The invention extracts the field plate function from the gate electrode structure by forming separate field plates in the inter-level dielectric layer. This separation removes the field plate from direct electrical connection to the gate electrode, thereby reducing gate-to-drain capacitance and switching losses while maintaining breakdown voltage enhancement through the field plate's electric field modulation effect in the drift region.
2Loss of energy
If separate field plates are patterned to reduce gate-to-drain capacitance, then switching losses are reduced, but fabrication complexity increases due to additional processing steps
Solution Approach 1:
The invention merges the field plate formation process with the existing contact/via fabrication process. Both field plates and contacts/vias are formed concurrently by filling openings in the inter-level dielectric layer with conductive material in a single processing step, eliminating additional masks and process steps while achieving reduced gate-to-drain capacitance and switching losses.
3Loss of energy
If non-gate materials are used for field plate formation, then gate-to-drain capacitance is reduced, but fabrication cost increases due to additional processing steps
Solution Approach 1:
The invention makes the conductive material filling process universal by using the same material and process for both field plates and contacts/vias. This multi-functional approach allows a single conductive material deposition and filling process to serve multiple purposes: forming field plates for voltage enhancement, forming contacts for electrical connection, and forming vias for inter-layer connectivity, thereby reducing fabrication cost while achieving low gate-to-drain 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
The use of discrete conduction units enhances breakdown voltage capability and reduces parasitic capacitance, providing a cost-effective and efficient solution for high voltage transistor devices by integrating with existing CMOS fabrication processes without additional masks or steps.
Implementation Method 1
Field plates are conductive elements, which are placed over a channel region to enhance the performance of a high voltage transistor device by manipulating electric fields (e.g., reducing peak electric fields) generated by a gate electrode
Implementation Method 2
The at least one conduction unit is disposed over the drift region and vertically extends from the dielectric layer to a top surface of the first ILD layer... reduces parasitic capacitance
Data Source
AI summary
The present disclosure relates to a high voltage transistor device having a field structure that includes at least one conduction unit, and a method of formation. In some embodiments, the high voltage transistor device has a gate electrode disposed over a substrate between a source region and a drain region located within the substrate. A dielectric layer laterally extends from over the gate electrode to over a drift region between the gate electrode and the drain region. A field structure is located within the first ILD layer. The field structure includes a conduction unit having a vertically elongated shape and vertically extending from a top surface of the dielectric layer and a top surface of the first ILD layer.