GaN Power Device Field Plate Optimization for TDDB
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Solution Overview
Problem
Power semiconductor devices with BPOA layouts face reliability issues due to high electric field peaks in dielectric layers, particularly during high temperature and high field operations, leading to time-dependent dielectric breakdown (TDDB), which is exacerbated by the lower thermal conductivity of GaN and self-heating effects.
Innovation Solution
The solution involves optimizing the dimensions of field plates in power semiconductor devices, varying them based on the presence or type of bonding pads above active areas to reduce electric field peaks within dielectric layers, using a configuration where field plates have different dimensions in NPOA, SPOA, and DPOA regions, and extending field plates beyond bonding pad edges to minimize peak electric fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If bonding pads are positioned directly over active areas (BPOA layout), then current density is improved, but electric field peaks increase causing time-dependent dielectric breakdown
Solution Approach 1:
The field plate structure implements local quality by having different dimensions in different regions: wider sections positioned under bonding pads (SPOA/DPOA areas) and narrower sections in non-pad areas (NPOA). This localized dimensional variation allows the structure to provide enhanced field control specifically where bonding pads create high electric field peaks, while maintaining appropriate current density distribution across the active area.
Solution Approach 2:
The invention applies parameter changes by varying the field plate width dimension as a function of position. The field plate width is increased in regions underlying bonding pads where electric field peaks occur, and reduced in regions without bonding pads. This continuous or discrete parameter variation optimizes both the electric field distribution and current density, resolving the contradiction between productivity and reliability.
2Strength
If GaN material is used for high critical electric field, then breakdown voltage is improved, but thermal conductivity decreases causing self-heating effects
Solution Approach 1:
The optimized field plate structure acts as an intermediary element that mediates between the high electric field requirements and thermal management needs. By strategically positioning wider field plate sections under bonding pads, the structure provides localized field control that reduces peak electric fields without requiring changes to the GaN material itself, thereby maintaining the high critical electric field advantage while mitigating self-heating effects through improved field distribution.
Data Source
AI summary
A power semiconductor device and method for making same are disclosed. The device includes a source bonding pad and a drain bonding pad, a drain metallization structure including a drain field plate connected to the drain bonding pad, and a source metallization structure comprising a source field plate connected to the source bonding pad. At least a portion of at least one of the bonding pads is situated directly over an active area. A dimension of at least one of the field plates varies depending upon the structure adjacent to the field plate.