Deep Trench Epitaxial Filling with In Situ HCl Etching
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Solution Overview
Problem
Existing methods for manufacturing semiconductor power devices with charge-balance structures face challenges in achieving uniform filling of deep trenches with high aspect ratios, leading to residual defects and increased manufacturing costs and complexity.
Innovation Solution
A process involving a sequence of epitaxial growth substeps with modulated gas flow ratios of hydrochloric acid to dichlorosilane, combined with in situ etching, to achieve uniform and defect-free filling of deep trenches, using hydrochloric acid to modulate growth rates and prevent void formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multi-step epitaxial growth with separate etching steps is used to fill deep trenches, then trench filling can be achieved, but the manufacturing process becomes complex and costly
Solution Approach 1:
The patent combines the epitaxial growth and etching steps into a single integrated process. Hydrochloric acid is introduced during the epitaxial growth step to simultaneously perform growth modulation and etching of overgrown portions, eliminating the need for separate etching steps and reducing manufacturing complexity while maintaining trench filling precision
Solution Approach 2:
The patent implements continuous trench filling through a single uninterrupted epitaxial growth step with in-situ etching. The growth process continues until complete trench filling is achieved, with hydrochloric acid continuously modulating the growth rate and removing excess material, thereby maintaining continuous useful action without intermittent separate processing steps
2Reliability
If high density of elementary strips is used to increase charge concentration, then breakdown voltage and output resistance improve, but the number of epitaxial growth steps increases leading to higher costs and defects
Solution Approach 1:
The patent changes the chemical parameters of the epitaxial growth process by introducing hydrochloric acid to the reaction environment. This modifies the growth rate dynamics and enables single-step filling of deep trenches, thereby achieving high charge concentration structures without increasing the number of growth steps, thus maintaining productivity while improving device reliability
3Speed
If epitaxial growth rate decreases with depth in trenches, then surface growth is fast, but voids remain in deep portions of trenches
Solution Approach 1:
The patent introduces hydrochloric acid as an intermediary substance during epitaxial growth. The acid diffuses into the trench and etches the grown material, creating a feedback mechanism that accelerates growth at the trench bottom where material accumulates. This intermediary enables uniform filling by compensating for the natural growth rate decrease with depth, ensuring complete trench filling without voids
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 process ensures complete and uniform filling of deep trenches, reducing defects and manufacturing costs, while maintaining low conduction resistance and improving electrical characteristics of semiconductor devices.
Implementation Method 1
the chemical-etching action of hydrochloric acid on silicon, to which I have added the flow of a dopant species
Implementation Method 2
uniform epitaxial filling free from voids of the deep trenches with monocrystalline silicon
Implementation Method 3
within the reaction environment for the epitaxial growth an appropriate chemical-etching agent mixed to the source gas used for the epitaxial growth
Data Source
Figure 1~2
Figure 3a~3c
Figure 3d~3f
AI summary
A process for manufacturing a semiconductor device (10; 10') envisages the steps of: providing a semiconductor material body (2) having at least one deep trench (4) that extends through said body of semiconductor material starting from a top surface (2a) thereof; and filling the deep trench (4) via an epitaxial growth of semiconductor material, thereby forming a columnar structure (8) within the body of semiconductor material (2). The manufacturing process further envisages the step of modulating the epitaxial growth by means of a concurrent chemical etching of the semiconductor material that is undergoing epitaxial growth so as to obtain a compact filling free from voids of the deep trench (4); in particular, a flow of etching gas is introduced into the same reaction environment as that of the epitaxial growth, wherein a flow of source gas is supplied for the same epitaxial growth.