FinFET Trench Isolation via Multi-Stepped Fin Cutting
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Solution Overview
Problem
Conventional FinFET fabrication faces challenges in improving current FinFET structures, particularly in achieving reliable isolation and preventing etching issues during fin cutting processes.
Innovation Solution
A semiconductor device and method involving a multi-stepped fin cut process to form trenches with depths smaller than the width of fin structures, using organic dielectric layers and progressive removal of dummy fin structures to enhance isolation and prevent etching issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fin cutting processes are used, then fabrication simplicity is maintained, but isolation reliability is insufficient and etching issues occur
Solution Approach 1:
The fin cutting process is divided into multiple sequential steps: first forming a trench to a first depth, then performing a second fin cut to a second depth greater than the first depth. This segmentation allows each etching step to be controlled independently, improving isolation reliability while managing process complexity through systematic breakdown of the fabrication process.
Solution Approach 2:
A trench is formed to a first depth before the actual fin cutting to a second depth. This preliminary trench formation creates a controlled etching path that prevents etching issues during the subsequent fin removal, ensuring reliable isolation while maintaining manageable process complexity through pre-planned process sequencing.
2Reliability
If trench depth is increased to improve isolation, then isolation effectiveness improves, but risk of collapsing and over-etching increases
Solution Approach 1:
The etching process is segmented into two distinct depth levels: a first trench depth and a second fin cut depth. By controlling the first trench to a shallower depth and then performing the second fin cut to a greater depth with proper spacing, the process achieves effective isolation while preventing the trench walls from collapsing or experiencing over-etching that would occur with a single deep etch.
Solution Approach 2:
The first trench acts as a cushioning structure formed before the second fin cut. This preliminary trench provides a buffer zone that prevents direct stress concentration and over-etching during the deeper second fin cut, thereby preventing collapsing and over-etching risks while maintaining isolation effectiveness.
3Reliability
If dummy fin structures are completely removed to form trenches, then isolation is improved, but etching control becomes difficult
Solution Approach 1:
The removal of dummy fin structures is segmented into controlled steps: first forming a trench at a first depth, then performing a second fin cut at a second depth. This segmentation maintains etching control by using the first trench as a reference and barrier, preventing uncontrolled over-etching while still achieving complete removal for improved isolation quality.
Solution Approach 2:
The first trench is formed as a preliminary structure before the second fin cut that completely removes dummy fins. This preliminary action establishes controlled etching boundaries and provides a reference depth, maintaining manufacturing precision while enabling complete dummy fin removal for superior isolation.
Data Source
AI summary
A semiconductor device and a method of fabricating the same, the semiconductor device includes a substrate, a plurality of fin shaped structures, a first trench and at least one bump. The substrate has a base. The fin shaped structures protrude from the base of the substrate. The first trench recesses from the base of the substrate and has a depth being smaller than a width of each of the fin shaped structures. The at least one bump is disposed on a surface of the first trench.