MOSFET Power Device with Clamping Diode for Reliability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current power management systems for portable electronic devices face challenges in miniaturization and cost due to the high product cost associated with integrating power switches and control circuitry on a common substrate, particularly at higher power ranges, and struggle with high-frequency switching due to parasitic impedances and reliability issues related to hot carrier injection.
Innovation Solution
The integration of MOSFET power devices with a clamping diode structure on a silicon substrate, using a buried well and field plate configuration to control electric field distribution and reduce gate-to-drain capacitance, along with a BiCMOS process on SOI substrates, enables monolithic integration of power switches and drivers, enhancing reliability and switching performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If power switches and control circuitry are integrated on a common substrate, then device miniaturization is achieved, but product cost increases due to large die area allocation to power switches
Solution Approach 1:
The power switch device is divided into multiple fingers, with each finger being a separate conductive structure. This segmentation allows the power switch area to be distributed across the substrate, reducing the concentration of die area required for the power switch while maintaining the same total switching area. The multiple fingers are interleaved with control circuitry, enabling better space utilization and reducing the overall device footprint without increasing unit cost.
Solution Approach 2:
The invention transitions from a planar layout to a three-dimensional interleaved structure where power switch fingers and control circuitry are stacked in alternating layers. This vertical arrangement allows both power switches and control circuitry to occupy the same horizontal footprint, effectively reducing the total die area required while maintaining full functionality of both components.
2Productivity
If power switches are allocated large die area, then switching performance is improved, but product cost increases
Solution Approach 1:
The power switch is segmented into multiple fingers that can be independently optimized. Each finger provides a portion of the total switching area, and their combined effect achieves the required switching performance. This segmentation allows the switching area to be distributed more efficiently across the substrate, reducing the concentrated die area requirement while maintaining overall switching capability.
Solution Approach 2:
The substrate serves multiple functions simultaneously: it hosts both power switch fingers and control circuitry, acts as an interconnection medium, and provides mechanical support. This multi-functionality reduces the need for separate dedicated areas for each function, thereby reducing total die area while maintaining switching performance.
3Reliability
If conventional power management systems are used, then reliability is maintained, but hot carrier injection and parasitic impedances reduce long-term reliability
Solution Approach 1:
The harmful effect of hot carrier injection is extracted and isolated by positioning the breakdown avalanche region away from the gate oxide interface. The clamping diode structure captures and contains the high-energy carriers in a dedicated region, preventing them from injecting into the gate oxide and degrading the transistor over time.
Solution Approach 2:
A clamping diode is introduced as an intermediary element between the power switch and the control circuitry. This diode with its specific breakdown voltage acts as a protective mediator that limits voltage spikes and captures hot carriers, preventing them from reaching and damaging the gate oxide of the transistor.
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 reduces the physical size and cost of power management systems, increases operating frequency, and improves long-term reliability by minimizing hot carrier injection and parasitic impedances, enabling efficient power management across a wider power range.
Implementation Method 1
a shielding structure including a field plate configured to control an electric field distribution along a top oxide interface away from an edge of the gate nearest the drain terminal
Implementation Method 2
position a breakdown avalanche region between the buried well and the drain terminal
Data Source
AI summary
A metal-oxide-semiconductor field-effect transistor (MOSFET) power device includes an active region formed on a bulk semiconductor substrate, the active region having a first conductivity type formed on at least a portion of the bulk semiconductor substrate. A first terminal is formed on an upper surface of the structure and electrically connects with at least one other region having the first conductivity type formed in the active region. A buried well having a second conductivity type is formed in the active region and is coupled with a second terminal formed on the upper surface of the structure. The buried well and the active region form a clamping diode which positions a breakdown avalanche region between the buried well and the first terminal. A breakdown voltage of at least one of the power devices is a function of characteristics of the buried well.