FinFET Isolation Material Formation for Leakage Current Control
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Solution Overview
Problem
In FinFET semiconductor devices, preventing leakage currents underneath the fin structures, known as 'punch through' leakage currents, is challenging due to difficulties in achieving accurate doping profiles and controlling dopant diffusion during thermal processes, which can compromise circuit performance and interfere with the benefits of stressed channel regions.
Innovation Solution
The method involves forming an initial fin structure, covering it with etch stop material, creating a sacrificial gate structure, and performing etching processes to define a replacement gate cavity while maintaining the etch stop material, which helps in forming a final fin structure and channel cavity filled with insulating material to reduce leakage currents without deterring from the benefits of stressed materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If doping processes are used to prevent punch through leakage currents, then leakage current reduction is achieved, but manufacturing precision deteriorates due to difficulties in achieving accurate doping profiles and controlling dopant diffusion
Solution Approach 1:
The patent divides the channel region into multiple segments by forming isolated fin structures separated by trenches filled with isolation material. This segmentation prevents the continuous channel that causes punch-through leakage, eliminating the need for precise doping profiles to control leakage currents.
Solution Approach 2:
The patent extracts the channel region from direct contact with the substrate by removing substrate material in trench regions and filling with isolation material. This extraction creates physical isolation between adjacent fins, preventing leakage paths without requiring precise dopant diffusion control.
2Reliability
If isolation material is formed to prevent punch through leakage, then leakage current is reduced, but device complexity increases due to additional etching and filling processes
Solution Approach 1:
The patent merges the isolation structure formation with the existing fin formation process. The same etching steps that define the fins also define the isolation trenches, and the isolation material filling is integrated into the existing process flow, reducing overall process complexity.
Solution Approach 2:
The isolation material serves multiple functions: it provides electrical isolation to prevent punch-through leakage, defines the fin structure geometry, and serves as a mechanical support structure. This multi-functionality reduces the need for separate dedicated isolation processes.
3Speed
If channel length is decreased to improve switching speed, then operating speed increases, but short channel effects worsen making it difficult to inhibit electrical potential interference between source and drain
Solution Approach 1:
The patent transitions from planar FET geometry to three-dimensional FinFET structures with vertical fins extending from the substrate. This dimensional change increases the effective channel width without increasing the footprint, and the vertical fin structure provides better gate control over the channel, suppressing short-channel effects even at reduced channel lengths.
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 effectively reduces punch through leakage currents while maintaining the electrical performance enhancements provided by stressed channel regions, improving the overall performance of FinFET devices by accurately positioning isolation material and controlling dopant distribution.
Implementation Method 1
covering a top surface and a portion of the sidewalls of the initial fin structure with etch stop material
Implementation Method 2
performing at least one etching process through the replacement gate cavity to remove a portion of the initial fin structure positioned under the replacement gate cavity
Implementation Method 3
substantially filling the channel cavity with an insulating material
Data Source
AI summary
One method disclosed includes, among other things, forming an initial fin, covering a top surface and a portion of the sidewalls of the initial fin structure with etch stop material, forming a sacrificial gate structure above and around the initial fin structure, forming a sidewall spacer adjacent the sacrificial gate structure, performing at least one process operation to remove the sacrificial gate structure and thereby define a replacement gate cavity, performing at least one etching process through the replacement gate cavity to remove a portion of the initial fin structure so as to thereby define a final fin structure and a channel cavity positioned below the final fin structure, and substantially filling the channel cavity with an insulating material.