Floating Guard Rings for Semiconductor Breakdown Voltage

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Solution Overview

Problem

Semiconductor devices face premature voltage breakdown due to electric field crowding at their edges, limiting their resistance vs. breakdown voltage performance, and existing edge termination techniques are inadequate in maintaining optimal breakdown voltage.

Innovation Solution

The use of multiple floating guard rings with optimized spacing and positioning, fabricated simultaneously with other semiconductor features, to alleviate electric field crowding and maximize breakdown voltage, while also allowing for precise control and reduced processing steps.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional edge termination techniques (moat etch, surface implantation, single floating guard rings, bevel edge, field plate terminations) are used, then electric field crowding at device edges is partially alleviated, but breakdown voltage remains limited and device resistance vs. breakdown voltage performance is suboptimal

Engineering Contradiction:

Improvebreakdown voltageVSAvoidedge termination structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent divides the edge termination structure into multiple discrete floating guard rings arranged in a specific pattern around the device edge, rather than using a single continuous termination structure. This segmentation allows each ring to independently manage electric field distribution, achieving superior breakdown voltage (exceeding 1000V) while maintaining manageable structural complexity

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent combines multiple termination techniques into a composite structure: floating guard rings are integrated with dielectric materials and conductive layers to create a multi-material edge termination system. This composite approach optimizes both electrical performance (breakdown voltage >1000V) and structural feasibility

Inventive Principle:

Principle #40Composite materials

2Manufacturing precision

If multiple processing steps and implantations are used for fabricating edge termination structures, then precise control of guard ring positioning and dimensions is achieved, but manufacturing complexity and cost increase

Engineering Contradiction:

Improveguard ring positioning precisionVSAvoidfabrication process simplicity

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent merges the fabrication of floating guard rings with the formation of other semiconductor features such as source pillars into a single integrated process. This consolidation achieves precise guard ring positioning (within micrometer accuracy) while reducing the total number of separate fabrication steps, thereby simplifying manufacturing without sacrificing precision

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent performs preliminary patterning and doping actions during earlier fabrication stages, establishing guard ring positions and structures before final device assembly. This preliminary action ensures precise positioning is achieved through cumulative process control rather than requiring complex final-step adjustments

Inventive Principle:

Principle #10Preliminary action

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 minimizes device resistance, expands application ranges, improves efficiency, increases switching frequency, reduces failures, and simplifies fabrication, resulting in higher yields and lower costs by optimizing breakdown voltage and reducing processing complexity.

Implementation Method 1

alleviating electric field crowding, optimally spreading the electric field, and yielding a breakdown voltage that is close to the material's limit

Methodology Applied

Scientific EffectElectric field distribution: Electric Field

Data Source

PatentUS8110494B1Systems and methods for maximizing breakdown voltage in semiconductor devices

Publication Date: 2012.02.07 NORTHROP GRUMMAN SYSTEMS CORP

AI summary

Systems and methods for maximizing the breakdown voltage of a semiconductor device are described. In a multiple floating guard ring design, the spacing between two consecutive sets of floating guard rings may increase with their distance from the main junction while maintaining depletion region overlap, thereby alleviating crowding and optimally spreading the electric field leading to a breakdown voltage that is close to the intrinsic material limit. In another exemplary embodiment, fabrication of floating guard rings simultaneously with the formation of another semiconductor feature allows precise positioning of the first floating guard ring with respect to the edge of a main junction, as well as precise control of floating guard ring widths and spacings. In yet another exemplary embodiment, design of the vertical separation between doped regions of a semiconductor device adjusts the device's gate-to-source breakdown voltage without affecting the device's pinch-off voltage.