Oxide Isolation Structure for Smoother LDMOS Junction Corners
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Solution Overview
Problem
Sharp corners at the junction between the field oxide layer and shallow trench isolation region in LDMOS devices reduce breakdown voltage and increase the risk of breakdown, affecting device performance.
Innovation Solution
A manufacturing method that forms a semiconductor device with a smooth junction between the horizontal and vertical oxide layers by etching the vertical oxide layer to reduce its height and oxidizing the exposed surfaces to eliminate sharp corners, ensuring a uniform thickness of the field oxide layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional manufacturing process forms the field oxide layer and shallow trench isolation region, then the device structure is completed, but sharp corners are formed at the junction which reduce breakdown voltage and increase breakdown risk
Solution Approach 1:
The patent applies preliminary action by performing a first etching process on the vertical oxide layer before the field oxide layer is fully formed. This pre-etching creates a recessed structure that prevents sharp corner formation during subsequent oxidation processes, thereby improving junction smoothness and preventing future breakdown issues
Solution Approach 2:
The patent implements curvature by rounding the corners at the junction between the field oxide layer and shallow trench isolation region through controlled etching and oxidation processes. This creates a smooth, curved transition instead of sharp corners, eliminating stress concentration points and improving breakdown voltage
2Manufacturing precision
If the vertical oxide layer is etched to reduce its height, then the junction smoothness is improved, but additional process steps are required
Solution Approach 1:
The patent merges multiple functions into the etching process: the first etching process simultaneously reduces the vertical oxide layer height, creates the recessed structure for smooth junctions, and prepares the surface for subsequent oxidation. This consolidation improves oxide layer uniformity while minimizing the increase in process complexity
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 enhances breakdown voltage and reduces the risk of charge accumulation, improving the performance and reliability of the semiconductor device.
Implementation Method 1
etching the vertical oxide layer to reduce its height and expose side surfaces of the trench
Implementation Method 2
oxidizing the exposed surfaces to form a smooth corner
Data Source
AI summary
A method of manufacturing a semiconductor device having a combination structure of a horizontal oxide layer structure and a vertical oxide layer structure, can include: etching from an upper surface of the semiconductor substrate to inside of the semiconductor substrate to form a trench; depositing oxides in the trench to form the vertical oxide layer structure; etching the vertical oxide layer structure from an upper surface thereof to decrease height of the vertical oxide layer structure, and to make a top surface of the vertical oxide layer structure be below the upper surface of the semiconductor substrate, in order to expose side surfaces of the trench; and forming, by an oxidation process, the horizontal oxide layer structure to cover part of the upper surface of the semiconductor substrate and the upper surface of the vertical oxide layer structure.