Self-Aligned Slotted AccuFET Structure for High Power Density
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Solution Overview
Problem
Conventional manufacturing technologies face challenges in achieving a high power density with minimized parasitic bipolar actions for vertical semiconductor power devices, particularly at smaller cell pitches, which weakens device structure and prevents high UIS ratings due to increased parasitic bipolar current gain and resistance in the body region.
Innovation Solution
A self-aligned slotted AccuFET device structure is developed with polysilicon stick-up gates and nitride gate caps to define and align slots, reducing cell pitch and eliminating parasitic bipolar latch-up, while using standard foundry processes for manufacturing, and incorporating Schottky, oxide, or doped polysilicon slots for different applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the cell pitch of trench-DMOS devices is reduced to achieve higher power density, then the power density increases, but the device structure is weakened due to increased parasitic bipolar actions
Solution Approach 1:
The gate structure is segmented into a trench gate portion extending into the semiconductor substrate and a stick-up gate portion extending above the substrate surface. This segmentation allows the trench gate to provide effective channel control while the stick-up gate portion enables formation of body contacts with low resistance, thereby reducing parasitic bipolar actions and maintaining device structure strength even at reduced cell pitches
Solution Approach 2:
The gate structure transitions from a conventional planar configuration to a three-dimensional structure with components in both vertical and lateral dimensions. The trench gate extends vertically into the substrate while the stick-up gate extends above the surface, creating a multi-dimensional architecture that simultaneously achieves small cell pitch and low parasitic bipolar actions
2Productivity
If the cell pitch is reduced to increase power density, then more devices can be integrated, but it becomes difficult to form effective body contact with low resistance due to smaller dimensions available for contact areas
Solution Approach 1:
The gate is divided into two functional segments: the trench gate portion that provides channel control and the stick-up gate portion that serves as a platform for body contact formation. This segmentation decouples the functions of channel control and body contact, allowing effective body contact formation even at reduced cell pitches where conventional approaches would fail
Solution Approach 2:
The stick-up gate portion acts as an intermediary structure between the trench gate and the body contact. It provides a raised platform that enables formation of body contacts with sufficient area for low resistance, bridging the gap between the reduced cell pitch requirement and the need for adequate contact dimensions
3Productivity
If the cell pitch is reduced, then higher power density is achieved, but the resistance of the body region increases resulting in increased parasitic bipolar current gain
Solution Approach 1:
By segmenting the gate into trench and stick-up portions, the invention enables formation of effective body contacts that reduce body region resistance. This lowers the parasitic bipolar current gain while maintaining the reduced cell pitch necessary for high power density
Solution Approach 2:
The stick-up gate structure, which adds vertical dimension and complexity to the device, inadvertently provides a solution to the parasitic bipolar problem by enabling low-resistance body contacts. The structural complexity is converted into a benefit that reduces harmful parasitic effects
Data Source
AI summary
This invention discloses a semiconductor power device disposed in a semiconductor substrate. The semiconductor power device includes trenched gates each having a stick-up gate segment extended above a top surface of the semiconductor substrate surrounded by sidewall spacers. The semiconductor power device further includes slots opened aligned with the sidewall spacers substantially parallel to the trenched gates. The stick-up gate segment further includes a cap composed of an insulation material surrounded by the sidewall spacers. A layer of barrier metal covers a top surface of the cap and over the sidewall spacers and extends above a top surface of the slots. The slots are filled with a gate material same as the gate segment for functioning as additional gate electrodes for providing a depletion layer extends toward the trenched gates whereby a drift region between the slots and the trenched gate is fully depleted at a gate-to-drain voltage Vgs=0 volt.