Super-junction MOSFET IPD Topography Correction
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Solution Overview
Problem
The reliability of super-junction power MOSFETs is limited by the inter-poly dielectric (IPD) layer, which experiences high leakage and low breakdown voltage due to topography issues and field crowding, affecting the performance and long-term reliability of the devices.
Innovation Solution
The method integrates oxide redeposition and etch-back processes into the manufacturing flow to improve the topography of the IPD layer, reducing fang regions and field crowding, thereby enhancing the breakdown voltage and reducing leakage without requiring additional photolithography or processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional IPD formation process is used, then manufacturing process is simple, but IPD layer has high leakage and low breakdown voltage due to topography issues and field crowding
Solution Approach 1:
The patent applies preliminary action by forming a first oxide layer on the trench sidewalls before depositing the shield electrode, then performing selective removal and redeposition. This preliminary oxide layer formation and subsequent processing steps prepare the surface topology in advance to prevent field crowding and improve IPD quality, resolving the contradiction between simple manufacturing and high reliability.
Solution Approach 2:
The patent changes physical and chemical parameters of the oxide layer through multiple processing steps: forming the first oxide layer, selectively removing portions, redepositing oxide material, and forming the second oxide layer with different thicknesses in different regions. These parameter changes eliminate fang regions and field crowding, improving IPD breakdown voltage without significantly complicating the manufacturing process.
2Reliability
If additional photolithography or processes are used to improve IPD topography, then IPD quality improves, but manufacturing complexity and cost increase
Solution Approach 1:
The patent merges multiple functions into the existing manufacturing process flow. The oxide layer formation, shield electrode deposition, and topography correction steps are integrated into the standard IPD fabrication sequence without requiring separate photolithography processes. This combining approach improves IPD quality while maintaining manufacturing simplicity.
Solution Approach 2:
The patent employs self-service by using the oxide deposition and removal processes to automatically correct topography issues. The selective removal of oxide portions and subsequent redeposition naturally eliminates fang regions and field crowding without requiring additional intervention or complex processing steps, improving IPD quality while keeping the manufacturing process straightforward.
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 results in improved breakdown voltage and reduced leakage for the inter-poly dielectric layer, enhancing the reliability and performance of super-junction power MOSFETs by eliminating fang regions and field crowding, with no need for extra masks or photolithography steps.
Implementation Method 1
forming a first oxide layer along first sidewalls of the first trench
Implementation Method 2
forming a gate dielectric over the first top surface of the first shield electrode
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A method for manufacturing a super-junction MOSFET entails forming a recessed shield electrode in a trench in a semiconductor layer of a substrate, the trench being lined with a first oxide layer. When the electrically conductive material forming the shield electrode is removed to recess the shield electrode, the first oxide layer on sidewalls of the trench is exposed. Removal of the first oxide layer from the sidewalls and from shield sidewalls of the electrode produces openings at a top part of the shield sidewalls. A second oxide layer is formed over the shield electrode and fills the openings. Part of the second oxide layer is removed to expose a top surface of the shield electrode. A gate dielectric is formed over the top surface of the shield electrode and conductive material is deposited over the gate dielectric in the trench to form a gate electrode of the MOSFET.