Stacked Forksheet FET Gate Isolation for Selective Metal Replacement
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Solution Overview
Problem
In semiconductor technology, particularly for stacked forksheet FETs, it is challenging to remove the first metal gate electrode from the top FET without affecting the first metal gate electrode of the bottom FET, due to the lack of a physical barrier in the existing processes.
Innovation Solution
A frontside gate cut structure is introduced to physically isolate the bottom FET from the top FET, allowing for the removal of the first metal gate electrode from the top FET without impacting the bottom FET. This structure provides a physical barrier for the removal process, enabling the formation of a second metal gate electrode in the top FET's area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If no physical barrier is introduced, then the manufacturing process is simpler, but the first metal gate electrode cannot be selectively removed from the top FET without affecting the bottom FET
Solution Approach 1:
The gate electrode structure is segmented into top and bottom FET regions by introducing a gate cut structure. This segmentation allows the first metal gate electrode to be selectively removed from the top FET while preserving it in the bottom FET, enabling independent gate control for each FET type.
Solution Approach 2:
A gate cut structure is introduced as an intermediary element between the top and bottom FETs. This intermediate structure physically separates the gate electrodes, allowing selective removal and independent management of gate electrodes in different FET regions without directly modifying the FET structures themselves.
2Adaptability or versatility
If a frontside gate cut structure is introduced to isolate top and bottom FETs, then selective removal of metal gate electrodes is enabled, but the device structure becomes more complex
Solution Approach 1:
The device is segmented into distinct top and bottom FET regions using a gate cut structure. This segmentation enables independent gate electrode management where different metal gate electrodes can be formed for NFET and PFET without requiring completely separate device structures.
Solution Approach 2:
The gate cut structure serves multiple functions: it physically isolates the gate electrodes, enables selective removal processes, and allows different metal gate materials to be deposited for different FET types. This multi-functionality reduces the need for additional specialized structures.
3Adaptability or versatility
If the first metal gate electrode is removed from the top FET, then a second metal gate electrode can be formed, but the process becomes more time-consuming without a physical barrier
Solution Approach 1:
The gate cut structure is formed in advance before the metal gate electrode deposition and removal processes. This preliminary action creates the physical barrier that enables selective removal and replacement of gate electrodes in subsequent processing steps, saving time by avoiding the need to create isolation structures after metal deposition.
Solution Approach 2:
The gate electrode system is segmented into removable top gate and permanent bottom gate regions. This segmentation allows the top FET's first metal gate electrode to be selectively removed and replaced with a second metal gate electrode, while the bottom FET's gate electrode remains intact, enabling differentiated gate material optimization.
Data Source
AI summary
A semiconductor structure including a stacked forksheet FET is provided. The semiconductor structure includes a frontside gate cut structure that physically isolates a bottom forksheet FET from a top forksheet FET. The frontside gate cut structure provides a physical barrier that allows for a first metal gate electrode to be removed from the top forksheet FET without negatively impacting (i.e., removing) the first metal gate electrode of the bottom FET. After removal of the first metal gate electrode from the top forksheet FET, a second metal gate electrode can be formed in the area of the top forksheet FET which was previously occupied by the first metal gate electrode.