Super Junction MOSFET Structure Without Deep Trench Etching
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Solution Overview
Problem
Conventional super junction power devices face challenges with mechanical stress, defects, and uniformity issues due to deep trench etching, leading to increased complexity, cost, and reduced yield and reliability, as well as inefficient termination voltage withstand structures that occupy more area in high voltage devices.
Innovation Solution
A method involving the formation of epitaxial layers with floating islands and pillars of specific conductivity types, using a super junction mask to implant dopants, which simplifies the process, reduces costs, and enhances breakdown voltage while minimizing on-state resistance and termination area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If deep trench etching and filling process is used to form super junction, then breakdown voltage is improved, but mechanical stress and defects increase leading to reduced reliability
Solution Approach 1:
The patent extracts and eliminates the deep trench etching step from the super junction formation process. Instead of etching deep trenches and filling them, the invention uses a simplified doping process that achieves the same charge sharing effect without creating mechanical stress and defects associated with deep trench structures.
Solution Approach 2:
The patent replaces the mechanical deep trench etching and filling system with a chemical doping system. The super junction structure is formed through selective doping of the drift region rather than through physical trench formation, thereby eliminating mechanical stress and manufacturing defects.
2Ease of manufacture
If deep trench etching is performed, then super junction structure is formed, but manufacturing complexity and cost increase
Solution Approach 1:
The patent removes the complex deep trench etching and filling steps from the manufacturing process. The super junction structure is achieved through a simpler selective doping process that reduces the number of manufacturing steps and associated complexity.
Solution Approach 2:
The patent changes the formation mechanism from physical trench etching to chemical doping. By altering the fundamental approach from mechanical removal and refilling to selective dopant introduction, the process complexity and manufacturing difficulty are significantly reduced.
3Area of stationary object
If conventional termination structures are used, then voltage withstand capability is improved, but device area increases
Solution Approach 1:
The patent makes the super junction structure in the cell region serve multiple functions: it provides both the low on-resistance benefit in the active area and extends voltage withstand capability to the termination region. The same floating doping structures that reduce Ron in the cell region also enhance BV in the termination region, eliminating the need for separate termination structures.
Solution Approach 2:
The patent merges the function of the cell region super junction with the termination region voltage withstand structure. By extending the floating doping structures into the termination region, the invention combines the low-resistance benefit and high-voltage capability into a single integrated structure, reducing overall device area.
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 improves breakdown voltage, decreases Miller and input capacitance, and reduces the on-state resistance of VDMOSFET devices, while also serving as a voltage divider to optimize termination voltage withstand structures and reduce the overall area of high voltage devices.
Implementation Method 1
formed by a deep trench etching process and a filling process in an epitaxial layer or formed by multiple steps of an epitaxial process and an implantation of doping in the epitaxial layer so as to increase BV due to charge sharing effect
Data Source
AI summary
The present invention provides a power device with super junction structure (or referred to as super junction power device) and a method of making the same. A floating island of a second conductivity type of a cell region, a floating island of the second conductivity type of a termination region, a pillar of the second conductivity type of the cell region and a pillar of the second conductivity type of the termination region may be formed through adding a super junction mask (or reticle) after forming the epitaxial layer of a first conductivity type, through a well mask (or reticle) before or after forming a well of the second conductivity type, and through a contact mask (or reticle) before or after forming a contact structure. Therefore, the process is simple, the cost is low and yield and reliability are high. A breakdown voltage (or referred to as withstand or blocking voltage) may be raised as a result of the charge sharing effect of the floating island of the second conductivity type and the pillar of the second conductivity type in the cell region and both Miller capacitance and input capacitance can be decreased. An on-state resistance can be decreased due to a higher doping level of the epitaxial layer of a first conductivity type allowed to use without degrading the breakdown voltage. A withstand (or blocking) voltage in the termination region may be raised, an area thereof may be reduced, and a whole area of a high voltage device may be decreased because of the floating island of the second conductivity type and the pillar of the second conductivity type of the termination region.