Superjunction Power Device Trench Filling with Epitaxial Silicon
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Solution Overview
Problem
Existing semiconductor power device manufacturing methods face challenges in achieving high breakdown voltage and low output resistance while minimizing defectiveness and cycle time, with previous solutions encountering issues such as increased cost, defectiveness, and repeatability problems due to complex epitaxial growth processes and trench filling methods.
Innovation Solution
A method involving the formation of deep trenches in a semiconductor body, partially filling them with epitaxial silicon to create columns with internal cavities, using a controlled epitaxial growth process with a balanced ratio of hydrochloric acid and dichlorosilane to ensure uniform coverage and repeatable results, thereby reducing defectiveness and cycle time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple steps of epitaxial growth are used to increase strip density, then output resistance decreases, but manufacturing complexity and defectiveness increase
Solution Approach 1:
The patent combines multiple epitaxial growth steps into a single continuous growth process. The trench filling is performed in one epitaxial growth step that simultaneously fills multiple trenches while forming the column structures, thereby reducing the total number of growth steps while maintaining the required strip density and output resistance performance
Solution Approach 2:
The patent segments the trench filling process by forming columns in individual trenches through a single epitaxial growth step, where each trench is filled independently but simultaneously with other trenches in the same growth cycle. This segmentation allows complex structures to be created without increasing the number of growth steps
2Reliability
If trenches are filled with dielectric materials, then charge balance is achieved, but thermal stress and manufacturing difficulty increase
Solution Approach 1:
The patent uses epitaxial silicon to fill the trenches, which has the same crystal structure and thermal expansion properties as the surrounding silicon substrate. This homogeneity eliminates thermal stress issues that arise from using dielectric materials with different thermal expansion coefficients, while still achieving the required charge balance for the superjunction structure
Solution Approach 2:
The patent changes the material parameter from dielectric materials to epitaxial silicon, which has matching thermal and mechanical properties with the substrate. This parameter change eliminates thermal stress while maintaining the ability to achieve charge balance through controlled doping during the epitaxial growth process
3Ease of manufacture
If trenches are left empty and sealed, then manufacturing is simplified, but ion implantation complexity increases
Solution Approach 1:
The patent performs preliminary doping during the epitaxial growth process itself, incorporating dopants into the silicon columns as they are formed. This preliminary action eliminates the need for subsequent ion implantation steps to achieve the required charge balance, simplifying the overall manufacturing process while maintaining device performance
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 allows for the efficient production of semiconductor power devices with high breakdown voltage and low output resistance, reducing defectiveness and production costs, while enabling flexible voltage classes by varying trench depth, and improving performance through increased strip density.
Implementation Method 1
forming a first column having a height by partially filling said trench with a semiconductor material via epitaxial growth
Data Source
AI summary
A method for manufacturing a semiconductor power device, comprising the steps of: forming a trench in a semiconductor body having a first type of conductivity; partially filling the trench with semiconductor material via epitaxial growth so as to obtain a first column having a second type of conductivity and having an internal cavity. The epitaxial growth includes simultaneously supplying a gas containing dopant ions of the second type of conductivity, hydrochloric acid HCl in gaseous form and dichlorosilane DCS in gaseous form, so that the ratio between the amount of HCl and the amount of DCS has a value of from 3.5 to 5.5.