FinFET Fabrication via Segmented Hard Mask and Local Doping
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Solution Overview
Problem
Conventional FinFETs face challenges in increasing threshold voltage above a certain level, which affects current drivability and off leakage characteristics, especially when three sides of the fin active region are easily opened, making them unsuitable for high-threshold voltage applications like DRAM.
Innovation Solution
A method involving a triple structure hard mask pattern and selective dry etching to form a fin active region pattern without etching the field oxide layer in the passing gate region, combined with a boron-doped polysilicon gate electrode to increase threshold voltage without degrading off leakage characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the field oxide layer is recessed to form a fin active region pattern, then current drivability is improved, but the field oxide layer is lost in the passing gate region
Solution Approach 1:
The patent divides the fin mask pattern into multiple segments: a first fin mask pattern for defining the fin active region and a second fin mask pattern for protecting the passing gate region. This segmentation allows selective etching of the field oxide layer in different regions, enabling fin formation where needed while preserving the field oxide layer in the passing gate region to maintain proper device characteristics.
2Manufacturing precision
If side doping is performed on the sidewalls of fin active region pattern, then threshold voltage is increased, but off leakage characteristics are degraded
Solution Approach 1:
The patent applies different doping strategies to different regions: side doping is performed on the sidewalls of the fin active region pattern to increase threshold voltage in the channel region, while avoiding doping in the passing gate region to maintain low off leakage characteristics. This local differentiation of doping quality resolves the contradiction between threshold voltage enhancement and off leakage control.
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 prevents field oxide layer loss, enhances current drivability, and maintains low off leakage characteristics, enabling FinFETs to meet high-threshold voltage requirements without degrading device performance.
Implementation Method 1
forming the active region pattern by selectively recessing the device isolation structure formed in the opened region using the hard mask pattern as an etch barrier
Implementation Method 2
side doping 18 may be performed on the sidewalls of fin active region pattern 15B using an ion implantation process under conditions of BF2, 60 keV, 2.0×1013 atoms/cm3
Data Source
AI summary
A method for fabricating a semiconductor device includes forming a device isolation structure in a substrate to define active regions, forming a hard mask pattern to open a region defining an active region pattern and to cover the device isolation structure, forming the active region pattern by selectively recessing the device isolation structure formed in the opened region using the hard mask pattern as an etch barrier, removing the hard mask pattern, forming a gate insulation layer over the substrate to cover at least the active region pattern, and forming a gate electrode over the gate insulation layer to cover at least the active region pattern.