Semiconductor Isolation Ring Structure for Uniform LDMOS Trenches
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Solution Overview
Problem
The existing manufacturing processes for lateral double-diffused metal oxide semiconductor (LDMOS) transistors face challenges in achieving uniform trench widths and depths, leading to asymmetric insulating layers and voids in conductive material deposition, which affect electrical isolation and contact formation.
Innovation Solution
The process involves forming trenches with constant widths at sides and corners to ensure uniform deposition of insulating and conductive materials, using a combination of etching and CMP processes to maintain symmetry and prevent voids, thereby improving the process window for sidewall oxide etching and contact via formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional trench formation processes are used, then manufacturing simplicity is maintained, but trench width and depth uniformity deteriorates leading to asymmetric insulating layers
Solution Approach 1:
The trench formation process is segmented into multiple controlled etching steps with intermediate CMP processes. Each etching step targets specific depth intervals, and CMP processes restore planarity between steps, ensuring uniform trench widths and depths while maintaining process control.
Solution Approach 2:
CMP processes are performed preliminarily between etching steps to restore surface planarity before subsequent etching operations. This preliminary surface preparation ensures that each etching step starts with a uniform surface, leading to consistent trench dimensions throughout the multi-step process.
2Reliability
If asymmetric trenches are formed, then manufacturing simplicity is maintained, but insulating layer symmetry and contact formation quality deteriorate
Solution Approach 1:
The manufacturing process employs periodic alternation between etching operations and CMP processes. Each cycle of etching followed by CMP creates progressively more uniform trenches, ensuring symmetric insulating layers and reliable contact formation through repeated refinement cycles.
Solution Approach 2:
The process incorporates feedback control where CMP operations respond to surface topography changes from previous etching steps. By continuously monitoring and correcting surface planarity between etching steps, the process ensures uniform trench dimensions and symmetric insulating layer deposition.
Data Source
AI summary
A semiconductor structure includes a semiconductor substrate, a transistor, a plurality of isolation structures, and a conductive feature. The transistor is over the semiconductor substrate. The isolation structures are over the semiconductor substrate. The isolation structures define a semiconductor ring of the semiconductor substrate surrounding the transistor. The conductive feature extends vertically in the semiconductor substrate and surrounds the transistor and semiconductor ring. The conductive feature has a rounded corner facing the semiconductor ring from a top view.