Isolation Capacitor Structure Using Lower-Bandgap Dielectric
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Solution Overview
Problem
Multi-chip modules face challenges with voltage breakdown due to high electric fields, particularly when using standalone isolation capacitor dies with thick dielectrics, which increase costs and cause wafer bow during manufacturing.
Innovation Solution
The use of a semiconductor device with a lower-bandgap dielectric layer beneath the capacitor plate, which has a bandgap energy less than that of the primary dielectric layer, helps mitigate voltage breakdown by reducing the electric field and eliminating the need for thick dielectrics, thereby reducing manufacturing costs and wafer bow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick dielectric layer is added below the bottom capacitor plate to isolate it from the substrate, then breakdown voltage performance is improved, but manufacturing cost increases and wafer bow occurs during manufacturing
Solution Approach 1:
The patent changes the material parameter (bandgap energy) of the dielectric layer beneath the bottom capacitor plate from high bandgap (e.g., silicon oxide) to low bandgap material. This parameter change allows the structure to achieve adequate breakdown voltage performance without requiring increased thickness, thereby avoiding the manufacturing issues associated with thick dielectric layers.
2Reliability
If a thick dielectric layer is used to provide isolation, then electrical isolation between high and low voltage circuits is improved, but mechanical stress and wafer bow increase
Solution Approach 1:
The patent applies parameter changes by selecting dielectric materials with appropriate bandgap energies for different locations. The low bandgap material beneath the bottom capacitor plate provides sufficient electrical isolation without requiring excessive thickness, thereby reducing the mechanical stress and wafer bow that would result from thick dielectric layers.
Solution Approach 2:
The patent employs a composite dielectric structure with different materials having different bandgap energies in different locations. This composite approach allows optimization of both electrical isolation performance and mechanical properties, avoiding the drawbacks of using uniformly thick dielectric layers throughout the capacitor structure.
3Reliability
If the bandgap energy of the dielectric layer below the capacitor plate is reduced, then breakdown voltage performance is enhanced, but the dielectric strength decreases
Solution Approach 1:
The patent applies local quality by using different dielectric materials with different bandgap energies in different locations within the capacitor structure. Specifically, low bandgap material is used beneath the bottom capacitor plate where it provides breakdown voltage enhancement, while other regions use appropriate dielectric materials for their specific functional requirements. This localized material selection optimizes both breakdown performance and overall dielectric strength.
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 configuration enhances the breakdown voltage performance and reduces mechanical stress, allowing for efficient capacitive isolation between high and low voltage circuits without increasing manufacturing costs or wafer bow issues.
Implementation Method 1
The high voltage can lead to a high electric field on the bottom plate that causes low voltage breakdown of the device
Implementation Method 2
The first and third capacitor plates spaced apart from one another along the third direction to form a second capacitor in series with the first capacitor
Data Source
AI summary
An electronic device includes a first dielectric layer above a semiconductor layer, lower-bandgap dielectric layer above the first dielectric layer, the lower-bandgap dielectric layer having a bandgap energy less than a bandgap energy of the first dielectric layer, a first capacitor plate above the lower-bandgap dielectric layer in a first plane of first and second directions, a second dielectric layer above the first capacitor plate, a second capacitor plate above the second dielectric layer in a second plane of the first and second directions, the first and second capacitor plates spaced apart from one another along a third direction, and a conductive third capacitor plate above the second dielectric layer in the second plane, the third capacitor plate spaced apart from the second capacitor plate in the second plane.