Charge-Balanced Epitaxial Region for Low-Resistance Power Semiconductors
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Solution Overview
Problem
Conventional semiconductor devices face a trade-off between high breakdown voltage and low on-state resistance, as increasing breakdown voltage leads to higher on-state resistance and vice versa, and existing fabrication methods for charge balance regions are costly and prone to defects.
Innovation Solution
The method involves forming recessed features in the semiconductor device and using atomic layer deposition (ALD) to conformally coat the surfaces with a film of opposite conductivity type, allowing dopant out-diffusion during thermal processing to create a charge balance region, which increases doping density without increasing breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the breakdown voltage is increased by incorporating a thicker and lower doped drift region, then the breakdown voltage is improved, but the on-state resistance increases
Solution Approach 1:
The patent applies local quality by creating a charge balance region with specific doping characteristics in a localized area of the drift region. This region has a different doping concentration and type compared to the surrounding drift region, allowing it to provide localized charge compensation that reduces on-state resistance without affecting the overall breakdown voltage characteristics of the device.
Solution Approach 2:
The patent changes the doping parameters (concentration and type) in the charge balance region to achieve the desired effect. By introducing a region with opposite polarity doping (e.g., p-type doping in an n-type drift region), the patent modifies the electrical parameters locally to reduce on-state resistance while preserving the high breakdown voltage property of the main drift region.
2Object-affected harmful factors
If the doping density in the drift region is increased to reduce on-state resistance, then the on-state resistance is improved, but the breakdown voltage decreases
Solution Approach 1:
Instead of uniformly increasing doping density throughout the drift region, the patent applies local quality by creating a distinct charge balance region with elevated doping density only in specific areas. This localized approach allows the device to benefit from reduced on-state resistance in the charged region while the rest of the drift region maintains its low doping density and high breakdown voltage characteristics.
Solution Approach 2:
The patent segments the drift region into multiple zones with different doping characteristics: a main drift region with low doping density for high breakdown voltage, and a charge balance region with higher doping density for reduced on-state resistance. This segmentation allows each region to optimize its function independently, resolving the contradiction between the two opposing requirements.
3Reliability
If conventional methods are used to fabricate charge balance structures, then the charge balance region is formed, but the manufacturing cost increases and defects occur
Solution Approach 1:
The patent employs self-service by utilizing the natural out-diffusion process of dopant atoms from the implantation region during thermal processing. Instead of requiring complex additional steps to form the charge balance region, the method allows the dopant to naturally diffuse out of the implantation site and into the drift region during standard thermal processing steps, thereby forming the charge balance structure automatically as part of the existing manufacturing flow.
Solution Approach 2:
The patent applies preliminary action by performing ion implantation to introduce dopant atoms into the drift region before the thermal processing step. This preliminary doping action positions the dopant atoms in the implantation region, and subsequent thermal processing causes them to out-diffuse and form the charge balance region. This approach integrates the charge balance formation into the existing manufacturing sequence without requiring separate dedicated process steps.
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 allows for reduced on-state resistance while maintaining high breakdown voltage, improving device performance and scalability, and is more cost-effective and defect-free compared to traditional methods.
Implementation Method 1
performing thermal processing such that at least a portion of dopant in the film deposited on the surfaces of the recessed features out-diffuses from the recessed features and forms a charge balance region in the epitaxial layer
Data Source
Figure 1A~1B
Figure 2~3
Figure 4
AI summary
A method of forming a charge balance region in an active semiconductor device includes: forming an epitaxial region including material of a first conductivity type on an upper surface of a substrate of the semiconductor device; forming multiple recessed features at least partially through the epitaxial region; depositing an insulating film and a second insulating film comprising material of a second conductivity type on a bottom and/or sidewalls of the recessed features using atomic layer deposition, wherein a net static charge is present at the interface between these two insulating layers; and performing thermal processing such that a charge balance region in then epitaxial regiion is formed following the contour of the recessed features..