Semiconductor Body Extension Region for Depth Breakdown Voltage
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Solution Overview
Problem
Existing semiconductor devices, such as BiC-DMOS transistors, face limitations in achieving high breakdown voltage in the depth direction due to the n-type body region having the same potential as the n-type buried region, which restricts the increase of breakdown voltage between the drain region and the buried region.
Innovation Solution
A body extension region of a first conductivity type is separated from a buried region by an isolation region of a second conductivity type and is in contact with a drift region, with specific portions of the body extension region located closer to the drain region and the surface than the element isolation insulating film, enhancing the breakdown voltage in the depth direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the n-type body region has substantially the same potential as the n-type buried region, then the device structure is simplified, but the breakdown voltage in the depth direction between the drain region and the n-type buried region cannot be increased
Solution Approach 1:
The body region is segmented into a body extension region and a body region, with the body extension region separated from the buried region by an isolation region. This segmentation allows the body extension region to have a different potential from the buried region, enabling increased breakdown voltage while maintaining structural organization.
Solution Approach 2:
An isolation region of opposite conductivity type is introduced as an intermediary between the body extension region and the buried region. This isolation region electrically separates the two regions, allowing independent potential control of the body extension region while maintaining physical proximity for electrical contact with the drift region.
2Reliability
If the body extension region is separated from the buried region by an isolation region, then the breakdown voltage in the depth direction is increased, but the device complexity increases
Solution Approach 1:
The isolation region is localized specifically between the body extension region and the buried region, rather than throughout the entire device. This localized approach increases breakdown voltage where needed while minimizing the overall impact on device complexity and fabrication processes.
Solution Approach 2:
The body extension region extends in the depth direction toward the second surface, utilizing the vertical dimension to achieve electrical contact with the drift region while being separated from the buried region. This dimensional approach allows breakdown voltage enhancement without significantly increasing lateral device complexity.
3Reliability
If the first portion of the body extension region is located closer to the drain region and the second surface, then the breakdown voltage is enhanced, but the manufacturing precision requirements increase
Solution Approach 1:
The body extension region is formed with its first portion extending toward the drain region and second surface in advance, during the epitaxial growth or implantation process. This preliminary positioning establishes the optimal geometry for breakdown voltage enhancement before subsequent fabrication steps, reducing the need for precise adjustments later in the manufacturing process.
Data Source
AI summary
The n-type body extension region BER is separated from the n+ buried region BL by the p-type impurity region PIR and is in contact with the p-type drift region DFT1. At the end of the n-type body extension region BER closest to the p+ drain region DC, the first portion FP of the n-type body extension region BER located closest to the second surface SS is located closer to the p+ drain region DC than the second portion SP of the n-type body extension region BER located at the first surface FS, and is located closer to the second surface SS than the bottom surface BS of the element isolation insulating film SIS.