Gas Cluster Ion Beam Conversion of Dummy Fins in FinFET Fabrication
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Solution Overview
Problem
In finFET manufacturing, removing dummy fins leads to fin density variation and challenges in subsequent processes, such as replacement metal gate, and does not adequately prevent fin merging, resulting in decreased circuit density and increased integrated circuit size.
Innovation Solution
Converting semiconductor fins into dielectric fins using a gas cluster ion beam process, which applies a high-energy gas phase atomic cluster beam to convert exposed fins into insulating materials like silicon nitride or oxide, thereby maintaining fin density and preventing unwanted merging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dummy fins are removed from the semiconductor structure, then fin density variation occurs and fin merging is not adequately prevented, but manufacturing complexity and circuit size increase
Solution Approach 1:
The patent changes the material parameter of selected fins by converting them from semiconductor material to dielectric material through gas cluster ion beam processing. This parameter change allows the fins to maintain their physical presence for density uniformity while providing electrical isolation to prevent merging, resolving the contradiction between reliability and manufacturing complexity
Solution Approach 2:
The patent converts the potentially harmful effect of having extra fins (which cause density variation and merging) into a beneficial feature by transforming them into dielectric material. These same fins now serve as both density-fillers and isolation barriers, turning what was a problem into a solution
2Reliability
If dummy fins are removed to prevent merging, then fin density uniformity improves, but circuit density decreases and integrated circuit size increases
Solution Approach 1:
The patent changes the material parameter of selected fins from semiconductor to dielectric, allowing them to maintain their physical presence for circuit density while providing electrical isolation to prevent merging. This resolves the contradiction by making the fins electrically inactive but physically present
3Reliability
If gas cluster ion beam is applied to convert fins to dielectric, then fin density is maintained and merging is prevented, but processing time and energy consumption increase
Solution Approach 1:
The gas cluster ion beam conversion is performed as a preliminary action before subsequent processing steps. By converting the fins to dielectric material early in the process, the patent prevents the need for later removal or modification steps, actually reducing total processing time despite the initial conversion step
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 maintains fin density, prevents fin merging, and increases circuit density, improving the uniformity of topography and yield in downstream processing steps, particularly beneficial for SRAM applications.
Implementation Method 1
applying a gas cluster ion beam to the unmasked fins to convert the unmasked fins into dielectric fins
Implementation Method 2
applying ion implantation to the unmasked fins to convert the unmasked fins into dielectric fins
Data Source
AI summary
FinFET structures with dielectric fins and methods of fabrication are disclosed. A gas cluster ion beam (GCIB) tool is used to apply an ion beam to exposed fins, which converts the fins from a semiconductor material such as silicon, to a dielectric such as silicon nitride or silicon oxide. Unlike some prior art techniques, where some fins are removed prior to fin merging, in embodiments of the present invention, fins are not removed. Instead, semiconductor (silicon) fins are converted to dielectric (nitride/oxide) fins where it is desirable to have isolation between groups of fins that comprise various finFET devices on an integrated circuit (IC).