Partial SOI Power Device Breakdown Voltage via Bonded Wafer
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Solution Overview
Problem
Increasing the thickness of the buried oxide layer in ultra-high voltage (UHV) MOSFET devices to enhance breakdown voltage leads to increased defect densities and reduced manufacturing throughput.
Innovation Solution
A method involving the formation of a bonded wafer with a thinned device wafer and a patterned handle wafer, where the device wafer is thinned from 20 μm to 5 μm and the handle wafer is partially removed below the power device, utilizing dielectric trench isolation and RESURF techniques to improve breakdown voltage and uniform electrostatic potential.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the BOX thickness is increased to increase breakdown voltage, then breakdown voltage is improved, but defect densities increase and manufacturing throughput decreases
Solution Approach 1:
The patent divides the wafer into two separate wafers (first wafer containing the power device, second wafer as handle) that are bonded together. This segmentation allows independent optimization of each wafer's thickness and properties, enabling thin device wafer for high throughput while maintaining adequate total thickness for breakdown voltage requirements through the bonded structure
Solution Approach 2:
The patent embeds the first wafer containing the power device within the bonded wafer structure, where the device wafer is thinned to 5 μm but the overall structure maintains adequate thickness through the handle wafer, achieving both high breakdown voltage and manufacturing efficiency
2Reliability
If the BOX thickness is increased to increase breakdown voltage, then breakdown voltage is improved, but defect densities increase
Solution Approach 1:
By segmenting the wafer into bonded separate wafers, each can be manufactured and processed independently with optimal thickness control. The device wafer can be thinned precisely to 5 μm without compromising overall structural integrity or introducing defects, as the handle wafer provides mechanical support
Solution Approach 2:
The patent changes the critical parameter from BOX layer thickness to device wafer thickness, transitioning from a thick BOX structure to a thinned device wafer structure. This parameter change enables achieving high breakdown voltage through the bonded wafer configuration rather than increasing BOX thickness, thereby reducing defect densities
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 increases the breakdown voltage of UHV MOSFET devices to over 525 V while reducing defect densities and maintaining manufacturing efficiency, as demonstrated by improved electric field distribution and breakdown voltage measurements.
Implementation Method 1
bonding a device wafer to a handle wafer with an intermediate oxide layer
Implementation Method 2
utilizing dielectric trench isolation and RESURF techniques to improve breakdown voltage and uniform electrostatic potential
Implementation Method 3
improved electric field distribution and breakdown voltage measurements
Data Source
AI summary
The present disclosure relates to a method and apparatus to increase breakdown voltage of a semiconductor power device. A bonded wafer is formed by bonding a device wafer to a handle wafer with an intermediate oxide layer. The device wafer is thinned substantially from its original thickness. A power device is formed within the device wafer through a semiconductor fabrication process. The handle wafer is patterned to remove section of the handle wafer below the power device, resulting in a breakdown voltage improvement for the power device as well as a uniform electrostatic potential under reverse biasing conditions of the power device, wherein the breakdown voltage is determined. Other methods and structures are also disclosed.