Asymmetric Source Zone in Superjunction Transition Region
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Solution Overview
Problem
Superjunction semiconductor devices face challenges in improving switching characteristics, particularly in managing charge carrier diffusion and parasitic BJT activation during voltage transitions, which can lead to increased thermal energy and potential device damage.
Innovation Solution
Incorporating an asymmetric second source zone in the transition region of the semiconductor device, electrically connected to the load electrode, which reduces charge carrier plasma density and prevents parasitic BJT activation by ensuring a negative voltage drop along the second pn junction, thereby enhancing commutation and avalanche breakdown handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If charge carriers are injected into the semiconductor die during reverse-biased state, then the blocking voltage capability is maintained, but the injected charge carriers increase plasma density which can activate parasitic BJT and cause thermal damage during voltage transition
Solution Approach 1:
The patent implements an asymmetric source zone configuration where source zones are present only on one side of the contact structure in the transition region, creating an asymmetric doping profile. This asymmetry generates a directional electric field that actively repels minority charge carriers (holes) from accumulating in the transition region, thereby preventing parasitic BJT activation while maintaining the blocking voltage capability through the superjunction structure.
Solution Approach 2:
The asymmetric source zone configuration establishes a preventive electric field barrier before voltage transitions occur. This preliminary anti-action repels charge carriers from entering the transition region during reverse-biased state, preventing the harmful accumulation of plasma density that would otherwise lead to parasitic BJT activation and thermal damage during commutation events.
2Reliability
If dopant concentrations are increased in the superjunction structure to improve blocking capability, then the blocking voltage is enhanced, but the on-state resistance increases
Solution Approach 1:
The patent utilizes the superjunction structure with alternating n-type and p-type columns, changing the doping parameter distribution vertically and laterally. This parameter change enables high dopant concentrations to be achieved in the superjunction regions for blocking voltage enhancement, while the asymmetric source zone configuration locally modifies the doping profile to reduce on-state resistance by preventing charge carrier accumulation and facilitating current flow during conduction state.
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
The asymmetric source zone design decreases maximum hole density by over 10% and prevents parasitic BJT activation, improving device reliability and reducing the risk of thermal damage during voltage changes and commutation events.
Implementation Method 1
prevents parasitic BJT activation by ensuring a negative voltage drop along the second pn junction
Implementation Method 2
In a reverse-biased state charge carriers injected into the semiconductor die diffuse into a termination region of the semiconductor die
Data Source
AI summary
A semiconductor device includes a transistor cell region and a transition region. The transistor cell region includes a first portion of a super junction structure and a first contact structure electrically connecting a first load electrode with first source zones of transistor cells. The first source zones are formed on opposite sides of the first contact structure. The transition region directly adjoins to the transistor cell region and includes a second portion of the super junction structure and a second contact structure electrically connecting the first load electrode with a second source zone. The second source zone is formed only at a side of the second contact structure oriented to the transistor cell region.