Rounded Trench Bottoms in Shielded Power Devices
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current power semiconductor devices face limitations in achieving high breakdown voltage and reliable electrical characteristics due to carrier avalanche and leakage current issues, particularly in trench-shielded structures.
Innovation Solution
The implementation of trench-shielded semiconductor devices with rounded bottom walls and improved dielectric layers, along with p-doped polysilicon trench electrodes, enhances breakdown voltage by effectively shielding mesas from electric potential lines and fields, and the use of optical proximity correction in photomasks for precise trench formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional trench structures are used in power semiconductor devices, then the device complexity is reduced and manufacturing is easier, but the breakdown voltage is limited due to carrier avalanche and leakage current issues
Solution Approach 1:
The patent applies curvature by rounding the bottom corners of the trenches. This spherical/curved geometry at the trench bottom eliminates sharp corners that concentrate electric fields, thereby preventing carrier avalanche and reducing leakage current. The rounded trench bottoms directly increase the breakdown voltage while maintaining the overall trench shield structure.
Solution Approach 2:
The patent implements local quality by applying different characteristics to different parts of the trench structure. Specifically, the trench walls maintain vertical sides for effective field shielding, while the trench bottoms are rounded to prevent avalanche. This localized differentiation optimizes both the shielding function and the breakdown voltage without requiring complete structural redesign.
2Reliability
If trenches with sharp bottom corners are used, then the manufacturing process is simpler, but the electric field concentration causes carrier avalanche and reduces breakdown voltage
Solution Approach 1:
The patent employs curvature transformation by rounding the trench bottom corners. This geometric modification eliminates the sharp corners that cause electric field concentration and carrier avalanche. The rounded shape is achieved through controlled manufacturing processes that can precisely form curved profiles at the trench bottoms.
Solution Approach 2:
The patent changes the geometric parameters of the trench structure by transitioning from sharp corners to rounded corners. This parameter change in the trench profile modifies the electric field distribution, reducing peak field concentrations and preventing avalanche breakdown, thereby increasing the overall breakdown voltage of the device.
3Manufacturing precision
If standard photomasks are used for trench formation, then the manufacturing process is simpler, but the trench formation precision is insufficient for optimal device performance
Solution Approach 1:
The patent applies preliminary action through optical proximity correction (OPC) in the photomask design. The photomask incorporates pre-calculated shape modifications and dimensional adjustments that compensate for optical diffraction and proximity effects during photolithography. This preliminary correction ensures that the final trench dimensions and shapes match the desired specifications, achieving high precision without requiring complex post-processing.
4Reliability
If the dielectric layer quality is poor, then the manufacturing process is faster and simpler, but conductive bridges form in the dielectric layer causing breakdown conditions
Solution Approach 1:
The patent changes the physical and chemical parameters of the dielectric layer formation process to achieve superior quality. This includes optimizing deposition temperature, controlling ambient conditions, and adjusting layer composition to eliminate defects and prevent conductive bridge formation. These parameter optimizations ensure high reliability while maintaining manufacturing efficiency.
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 significantly increases the breakdown voltage and improves the electrical characteristics of power semiconductor devices by effectively managing electric fields and reducing leakage current, leading to enhanced reliability and performance.
Implementation Method 1
pushing away electric potential lines and fields from the device region to increase the breakdown voltage of the device
Implementation Method 2
growing a sacrificial oxide layer on the walls of the initial trenches
Implementation Method 3
due to various processes occurring in the semiconductor material, such as carrier avalanche, the ability to suppress the current flow in the OFF-state fails at a certain level of voltage
Data Source
AI summary
Various structures and methods for improving the performance of trench-shielded power semiconductor devices and the like are described. An exemplary device comprises a semiconductor region having a surface, a first area of the semiconductor region, a well region of a first conductivity type disposed in the semiconductor region and around the first area, and a plurality of trenches extending in a semiconductor region. Each trench haves a first end disposed in a first portion of the well region, a second end disposed in a second portion of the well region, and a middle portion between the first and second ends and disposed in the first area. Each trench further having opposing sidewalls lined with a dielectric layer, and a conductive electrode disposed on at least a portion of the dielectric layer.