Super-junction Device Trench Segmentation for Breakdown Voltage
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Solution Overview
Problem
Current fabrication methods for super-junction devices are complex, costly, and suffer from poor repeatability and productivity, particularly due to limitations in forming alternating P-type and N-type semiconductor films, which affect the device's breakdown voltage and on-resistance.
Innovation Solution
A super-junction device is fabricated using a heavily doped substrate with alternating epitaxial layers and trenches, where oxide films and polysilicon layers are used to form sandwich structures with controlled doping concentrations, reducing process complexity and cost, and enhancing the device's performance by minimizing gate-drain parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the epitaxial silicon filling approach is used to form P-type and N-type films, then the device can achieve high breakdown voltage, but the process becomes complex, time-consuming, and costly
Solution Approach 1:
The device is divided into repeating unit structures, each containing alternating P-type and N-type films formed by segmented trench filling. This segmentation allows standardized processing steps to be repeated efficiently across the wafer, reducing overall process complexity while maintaining high breakdown voltage performance through consistent film formation in each unit cell.
Solution Approach 2:
Trenches are pre-formed in the epitaxial layer before filling with doped silicon. This preliminary action defines the precise locations and dimensions of P-type and N-type regions, enabling subsequent filling operations to proceed systematically. The pre-defined trench structure ensures proper film placement and thickness control, simplifying the overall fabrication process while achieving the required breakdown voltage characteristics.
2Ease of manufacture
If tilted ion implantation is used to form P-type and N-type films, then the device structure can be created, but the method suffers from poor stability and repeatability
Solution Approach 1:
The patent replaces the mechanical tilted ion implantation process with a chemical vapor deposition (CVD) filling process. Instead of physically implanting ions at specific angles, the method uses chemical reactions to deposit doped silicon into pre-formed trenches. This substitution eliminates the stability and repeatability issues associated with tilted implantation while maintaining the ability to create the required P-type and N-type film structures with precise control over doping concentration and film uniformity.
3Manufacturing precision
If deeper trenches are formed to achieve desired film depth, then the device performance improves, but the epitaxial silicon filling process takes longer and becomes more difficult
Solution Approach 1:
The patent controls film depth by adjusting key process parameters including trench depth, doping concentration of the filling silicon, and CVD deposition conditions. By changing these parameters, the method achieves precise control over the depth and properties of P-type and N-type films without requiring excessively deep trenches. This parameter optimization maintains manufacturing precision while significantly improving production efficiency compared to filling extremely deep trenches.
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 method simplifies the formation of semiconductor films with desired doping concentrations, improves repeatability and productivity, reduces the size of the termination structure, and enhances the device's performance by reducing gate-drain parasitic capacitance and sustaining high voltage.
Implementation Method 1
an oxide film in each of the plurality of first trenches
Implementation Method 2
a pair of first films having the first type of conductivity on both sides of each of the plurality of first trenches, thereby forming a sandwich structure
Data Source
AI summary
A super-junction device including a unit region is disclosed. The unit region includes a heavily doped substrate; a first epitaxial layer over the heavily doped substrate; a second epitaxial layer over the first epitaxial layer; a plurality of first trenches in the second epitaxial layer; an oxide film in each of the plurality of first trenches; and a pair of first films on both sides of each of the plurality of first trenches, thereby forming a sandwich structure between every two adjacent ones of the plurality of first trenches, the sandwich structure including two first films and a second film sandwiched therebetween, the second film being formed of a portion of the second epitaxial layer between the two first films of a sandwich structure. A method of forming a super-junction device is also disclosed.