Air-Gap Fin Structure for Leakage Reduction in Bulk Substrates
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Solution Overview
Problem
Current semiconductor devices, such as FinFETs, face challenges with current leakage, particularly due to the high cost and incompatibility of silicon-on-insulator (SOI) configurations with bulk substrates, which are not readily compatible and can lead to electrical and process limitations.
Innovation Solution
A fin structure for semiconductor devices is developed, featuring a first semiconductor material grown epitaxially within a fin recess, a second semiconductor material with a recessed portion, and an air gap located between them, which reduces current leakage. The air gap has a tubular configuration parallel to the direction from the source to the drain region, and the epitaxial growth process includes an extra O2 plasma step to maintain uniformity and prevent excessive oxidation, allowing for symmetrical shovel-shaped SiP bulk layer growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silicon-on-insulator (SOI) configuration is used to reduce current leakage, then current leakage is reduced, but cost increases and compatibility with bulk substrates deteriorates
Solution Approach 1:
The device is segmented into distinct regions: a bulk substrate portion and an SOI portion with air gap. This segmentation allows the device to utilize the cost advantage of bulk substrates while incorporating the low leakage advantage of SOI configuration in specific critical regions, thus resolving the contradiction between cost and leakage reduction.
Solution Approach 2:
The SOI configuration with air gap is applied locally to specific regions where current leakage is most problematic, rather than throughout the entire device. This local application maintains compatibility with bulk substrate manufacturing processes while achieving leakage reduction where most needed.
2Reliability
If air gap is introduced to reduce current leakage, then current leakage is reduced, but device structure complexity increases
Solution Approach 1:
The air gap is created by removing material (taking out) from the substrate to form a recessed portion, rather than adding complex structures. This extraction approach reduces current leakage by creating an insulating air region while adding minimal structural complexity compared to traditional SOI methods.
3Manufacturing precision
If epitaxial growth is performed to grow semiconductor material, then material uniformity is achieved, but oxidation control becomes critical
Solution Approach 1:
The air gap creates an inert/oxidation-free environment for the epitaxial growth interface. By positioning the air gap between the substrate and the epitaxially grown layer, the process eliminates the need for complex oxidation control measures while maintaining material uniformity, as the air gap prevents unwanted oxidation reactions during growth.
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 air gap effectively reduces current leakage by separating the semiconductor materials and maintaining uniform epitaxial growth, enhancing the performance of FinFET devices without the need for costly SOI configurations, thereby improving device reliability and efficiency.
Implementation Method 1
the air gap may reduce current leakage associated with the fin structure
Implementation Method 2
the epitaxial growth process includes an extra O2 plasma step to maintain uniformity and prevent excessive oxidation
Implementation Method 3
the epitaxial growth process includes an extra O2 plasma step
Data Source
AI summary
A fin structure for a semiconductor device, such as a FinFET structure, has first and second semiconductor layers and an air gap between the layers. The second semiconductor layer includes a recessed portion, the air gap is located in the recessed portion, and the recessed portion has an upwardly-opening acute angle in the range from about 10° to about 55°. The air gap may prevent current leakage. A FinFET device may be manufactured by first recessing and then epitaxially re-growing a source/drain fin, with the regrowth starting over a tubular air gap.