Tri-Layer STI Liner With Al2O3 Dipole for Nanosheet Leakage
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Solution Overview
Problem
Sub-sheet leakage in n-type nanosheet FETs is caused by positive parasitic charges formed within the nitride liner and at the interface between the nitride and oxide liners, which distorts current-voltage behavior and negatively affects performance and reliability.
Innovation Solution
A tri-layer shallow trench isolation (STI) liner is formed with an aluminum oxide layer between the oxide and nitride layers, creating a dipole effect that neutralizes positive charges, reducing sub-sheet leakage without increasing leakage in p-type nanosheet FETs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a nitride liner is used in the shallow trench isolation region, then the structural integrity and protection of the nanosheet fin is improved, but positive parasitic charges are generated within the nitride liner and at its interface with the oxide liner, causing sub-sheet leakage in n-type nanosheet FETs
Solution Approach 1:
An aluminum oxide layer is introduced as an intermediary between the silicon oxide liner and the silicon nitride liner. This intermediate layer creates a dipole effect that generates negative charges to neutralize the positive parasitic charges formed in the nitride liner, thereby eliminating sub-sheet leakage while preserving the protective function of the nitride liner
Solution Approach 2:
The invention changes the physical and chemical parameters of the liner structure by introducing a specific material (aluminum oxide) with particular properties (dipole moment) between existing layers. This parameter change transforms the charge distribution characteristics of the liner stack, converting the harmful positive charge accumulation into a neutralized state
2Reliability
If the tri-layer STI liner is implemented to neutralize positive charges, then sub-sheet leakage in n-type nanosheet FETs is reduced, but the device complexity and manufacturing process steps increase
Solution Approach 1:
The liner structure is segmented into three distinct functional layers: the first oxide liner (silicon oxide) for interface protection, the second oxide liner (aluminum oxide) for charge neutralization, and the third liner (silicon nitride) for structural integrity. This segmentation allows each layer to perform its specific function independently, achieving reliable leakage reduction through a systematic division of responsibilities
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 tri-layer STI liner effectively cancels positive charges within the nitride liner and at its interface with the oxide liner, reducing sub-sheet leakage in n-type nanosheet FETs while maintaining performance in p-type nanosheet FETs, thus enhancing the reliability and density of nanosheet FETs.
Implementation Method 1
the second liner is made of a second oxide material that creates a dipole effect for neutralizing positive charges within the third liner and positive charges between the third liner and the first liner
Data Source
AI summary
A semiconductor structure includes a plurality of fins on a semiconductor substrate, the plurality of fins including an alternating sequence of a first nanosheet made of epitaxially grown silicon and a second nanosheet made of epitaxially grown silicon germanium, and a shallow trench isolation region within the semiconductor substrate adjacent to the plurality of fins. The shallow trench isolation region including a recess within the substrate filled with a first liner, a second liner directly above the first liner, a third liner directly above the second liner, and a dielectric material directly above the third liner. The first liner is made of a first oxide material, the third liner is made of a nitride material, and the second liner is made of a second oxide material that creates a dipole effect for neutralizing positive charges within the third liner and positive charges between the third liner and the first liner.