IGBT Γ-Shape Mixed Gate Structure for Current Density and SOA
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Solution Overview
Problem
Existing IGBT chips face challenges in balancing current density and short-circuit performance due to the limitations of planar and trench gate structures, which restrict conductivity modulation and affect safe operating areas.
Innovation Solution
The IGBT chip incorporates a Γ-shape mixed gate structure combining both planar and trench gates, with trench gates formed inside the substrate and planar gates on the surface, connected by a shared polycrystalline silicon layer, allowing for enhanced current density and safe operating area without compromising blocking capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a planar gate structure is used, then the manufacturing process is simple and the blocking capability is good, but the channel density is restricted and the conduction voltage drop is high
Solution Approach 1:
The gate structure is segmented into two distinct types: planar gates and trench gates. These segmented gate structures are arranged in different regions of the same IGBT chip, allowing each type to perform its specialized function without interfering with the other. This segmentation enables the chip to simultaneously achieve low manufacturing complexity and low conduction voltage drop.
Solution Approach 2:
Different regions of the IGBT chip are assigned different gate structure qualities: planar gates are used in regions where simple manufacturing and high blocking capability are prioritized, while trench gates are used in regions where low conduction voltage drop and high current density are critical. This local differentiation optimizes overall chip performance.
2Productivity
If a trench gate structure is used, then the cell density is increased and the current density is high, but the short-circuit performance is weakened and the safe operating area is affected
Solution Approach 1:
The chip is segmented into multiple functional regions with different gate structures. Trench gates are concentrated in specific regions to provide high current density, while planar gates are placed in other regions to ensure adequate short-circuit performance. This spatial segmentation allows the chip to achieve high overall current density while maintaining reliability.
Solution Approach 2:
The gate structure parameters (depth, width, doping concentration) are changed and optimized for different operating conditions. Trench gates have parameters optimized for high current density, while planar gates have parameters optimized for short-circuit protection. This parameter differentiation enables the chip to meet both high productivity and high reliability requirements.
3Quantity of substance
If the trench gate density is increased, then the chip saturation current is increased, but the blocking capability is weakened due to electric field crowding at the trench bottoms
Solution Approach 1:
The gate structure is segmented into planar and trench types, with each type occupying specific regions of the chip. This segmentation allows the chip to achieve high saturation current through dense trench gate regions while maintaining adequate blocking capability through planar gate regions, avoiding the electric field crowding problem that would occur if trench gates were uniformly distributed at high density throughout the entire chip.
Data Source
AI summary
An IGBT chip having a Γ-shape mixed gate structure includes a plurality of mixed gate units. Each of the mixed gate units includes a gate region and two active regions located at two sides of the gate region. The gate region includes a trench gate and a planar gate that is located on a surface of the gate region, and the planar gate is connected with the trench gate and formed a Γ-shape mixed structure. In this way, the IGBT chip can have a significantly improved chip density, while retaining features of low power consumption and high current density of the trench gate and a feature of a wide safe operating area of the planar gate.