GAA Gate Cap Layer Layout for Lower Parasitic Capacitance
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Solution Overview
Problem
Integration of gate-all-around (GAA) transistor fabrication is challenging due to the complexity of forming the gate structure around the nanowire, which affects gate control and increases OFF-state current and short-channel effects.
Innovation Solution
A method involving double-patterning or multi-patterning processes is used to form a semiconductor device structure, including the formation of an inverted T-shape gate structure with a cap layer between the gate electrode and spacer layers, reducing parasitic capacitance and enhancing device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional single-patterning lithography is used to form gate structures, then the fabrication process is simple, but the gate control is insufficient and short-channel effects increase
Solution Approach 1:
The fabrication process is divided into multiple patterning steps (double-patterning or multi-patterning) to achieve precise gate structure formation. The gate structure is formed in segments through sequential deposition and etching steps, allowing better control over the final geometry and improved gate-channel coupling.
Solution Approach 2:
The gate structure transitions from a planar configuration to a three-dimensional gate-all-around configuration that surrounds the channel region. This dimensional change enables the gate to control the channel from multiple directions (top and sidewalls), significantly improving gate control and reducing short-channel effects.
2Reliability
If gate-all-around structure is implemented to improve gate control, then gate-channel coupling increases, but fabrication integration becomes challenging
Solution Approach 1:
The gate structure is built up incrementally through preliminary deposition steps, where each layer is prepared and patterned before the next is added. This preliminary action allows complex 3D structures to be constructed from simpler 2D patterns, making the fabrication process more manageable and integrable into existing CMOS processes.
Solution Approach 2:
The gate structure employs a nested configuration where the gate electrode is surrounded by dielectric layers, which are in turn surrounded by spacer structures. This nested arrangement allows multiple functional layers to be integrated in a compact geometry, achieving gate-all-around control while maintaining fabrication feasibility.
3Manufacturing precision
If multi-patterning processes are used to form precise GAA transistor structures, then device performance is enhanced, but manufacturing steps increase
Solution Approach 1:
Multiple patterning steps are merged into a unified fabrication sequence where deposition, etching, and spacer formation operations are combined efficiently. The process integrates gate electrode formation, dielectric deposition, and spacer patterning in a coordinated manner, reducing the overall number of discrete manufacturing steps while maintaining high pattern precision.
Data Source
AI summary
A semiconductor device structure includes nanostructures over a substrate and a gate structure surrounding the nanostructures. The semiconductor device structure also includes spacers over opposite sides of the gate structure over the nanostructures. The semiconductor device structure further includes a first metal layer over the gate structure and a second metal layer over the first metal layer. In addition, the semiconductor device structure includes a first cap layer over the second metal layer. The first cap layer has an extending portion between the second metal layer and the spacers.