Shielded-Gate Trench MOSFET Contact Structure for Shield Resistance
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Solution Overview
Problem
Conventional semiconductor devices face challenges with high shield resistance, leading to decreased power conversion efficiency and increased switch node ringing, particularly in high-frequency applications, due to inadequate control over shield resistance and capacitance.
Innovation Solution
The introduction of conductive regions that make contact with the shield electrode within the active area of the MOSFET device, allowing for controlled reduction of shield resistance without uniformly increasing device capacitance, achieved by creating recesses in the gate conductor and using insulators to isolate the shield conductor, enabling localized adjustment of shield resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional semiconductor devices are used without additional shield contact structures, then device complexity is low, but shield resistance is high leading to poor power conversion efficiency
Solution Approach 1:
The shield contact structure is segmented into multiple components: a contact opening through the interlayer dielectric, a conductive region filling the opening, and an insulator layer isolating the conductive region from the gate conductor. This segmentation allows the shield resistance to be reduced through multiple localized contact points while maintaining manageable device complexity through modular construction.
Solution Approach 2:
The shield contact is implemented by adding a vertical dimension through the interlayer dielectric layer, creating a three-dimensional contact structure. The conductive region extends vertically from the top surface through the dielectric to contact the shield electrode, enabling resistance reduction without expanding the planar footprint excessively.
2Loss of energy
If shield resistance is reduced by adding more shield contacts, then power conversion efficiency improves, but device complexity increases
Solution Approach 1:
The insulator layer is selectively positioned only at locations where shield contacts are needed, rather than uniformly across the entire device. This local quality approach reduces shield resistance at critical points while maintaining gate conductor continuity in other areas, thereby improving efficiency without proportionally increasing overall device complexity.
Solution Approach 2:
The insulator layer acts as an intermediary element that enables the shield contact structure to function properly. It isolates the conductive region from the gate conductor, preventing short circuits while allowing the shield contact to reduce resistance. This intermediary component resolves the contradiction by enabling resistance reduction without compromising device integrity or excessive complexity.
3Reliability
If recesses are created in the gate conductor to contact the shield electrode, then shield resistance decreases, but manufacturing precision requirements increase
Solution Approach 1:
The contact opening is formed through the interlayer dielectric layer before the conductive region is deposited. This preliminary action establishes the precise location and dimensions of the shield contact interface, allowing subsequent layers to be aligned to this pre-defined structure, thereby reducing the cumulative precision requirements across multiple manufacturing steps.
Solution Approach 2:
The conductive region automatically conforms to the shape of the contact opening and self-aligns with the shield electrode beneath it during the deposition process. This self-service mechanism reduces the need for additional alignment steps and precision adjustments, as the conductive material naturally fills the prepared opening and makes contact with the shield electrode.
Data Source
AI summary
A semiconductor device includes a region of semiconductor material comprising a shielded-gate trench structure. The shielded-gate trench structure includes an active trench, an insulated shield electrode in the lower portion of the active trench, an insulated gate electrode adjacent to the gate dielectric in an upper portion of the active trench, and an inter-pad dielectric (IPD) interposed between the gate electrode and the shield electrode. A conductive region is within the active trench and extends through the gate electrode and the IPD and is electrically connected to the shield electrode. The conductive region is electrically isolated from the gate electrode. The gate electrode comprises a shape that is uninterrupted on at least one side the conductive region in a top view so that the gate electrode.