Tapered Embedded Epitaxial Films in Superjunction MOSFETs
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Solution Overview
Problem
Current vertical power MOSFETs with superjunction structures face limitations in optimizing on-resistance while maintaining high withstand voltage, requiring improvements in structure and manufacturing methods to enhance performance.
Innovation Solution
The implementation of a semiconductor device with alternately arranged p-type and n-type pillars, featuring tapered embedded semiconductor films on the trench sides, and a trench fill process using the Bosch process and hydrogen annealing to form a high aspect ratio trench with controlled impurity concentration, allowing for reduced on-resistance and increased withstand voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a superjunction structure is used to reduce on-resistance, then electrical conductivity is improved, but manufacturing precision becomes more difficult to control
Solution Approach 1:
The patent applies parameter changes by systematically varying the impurity concentration gradients in the tapered embedded semiconductor films. The concentration is designed to be higher at the bottom and lower at the top, creating an optimized electrical profile that reduces on-resistance while the gradual transition eases manufacturing control requirements
Solution Approach 2:
The patent implements local quality by creating spatially varying impurity concentrations within the embedded semiconductor films. Different regions of the film have different impurity concentrations, with higher concentrations at the bottom and lower concentrations at the top, allowing optimized electrical properties in different locations
2Ease of manufacture
If tapered embedded semiconductor films are formed on trench sides, then manufacturing flexibility is improved, but process complexity increases
Solution Approach 1:
The patent applies preliminary action by forming the tapered embedded semiconductor films on the trench sidewalls before filling the trench interior. This sequence allows the tapered structures to be created while the trench is still accessible, simplifying the formation of complex geometries compared to attempting to create them after trench closure
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 effectively reduces on-resistance while maintaining high withstand voltage, providing a larger margin for impurity concentration variations and improving product yield by allowing for better controllability and reduced defects.
Implementation Method 1
a tapered embedded semiconductor film having the second conductivity type is disposed on a side face of each of the first trenches
Implementation Method 2
hydrogen annealing to form a high aspect ratio trench with controlled impurity concentration
Data Source
AI summary
Properties of a semiconductor device are improved. A semiconductor device having a superjunction structure, in which p-type column regions and n-type column regions are periodically arranged, is configured as follows. Each n-type column region has a vertical section including an n-type epitaxial layer located between trenches and a tapered embedded n-type epitaxial film disposed on a side face of the trench. Each p-type column region includes an embedded p-type epitaxial film disposed within the trench. The tapered embedded n-type epitaxial film is thus provided on the sidewall of the trench in which the p-type column region is to be disposed, thereby the p-type column region is allowed to have an inverted trapezoidal shape, leading to an increase in margin for a variation in concentration of a p-type impurity in the p-type column region. On resistance can be reduced by lateral diffusion of an n-type impurity (for example, As).