Vertical Protrusion Hard Mask for Precise Metal Gate Etch-Back
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Solution Overview
Problem
The challenge in semiconductor manufacturing is the lack of selectivity between salicide and metal gates during the etch-back process, which complicates the production of semiconductor devices.
Innovation Solution
A self-aligned method is employed to form a hard mask on the top of a vertical structure using a dielectric layer as a stop layer, protecting underlying layers during metal gate etch-back processes, particularly in vertical gate-all-around (VGAA) procedures, utilizing materials like Ti or TiN for salicide metal and Si, SiGe, III-V compounds for the source, channel, and drain layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional etch-back process is used without selective protection, then the metal gate can be removed, but the salicide layer is also damaged due to lack of selectivity
Solution Approach 1:
The patent segments the protective structure into multiple functional layers: a first dielectric layer forming a hard mask at the top surface, and a second dielectric layer providing lateral protection on sidewalls. This segmentation allows each layer to perform its specific protective function during the etch-back process, preventing damage to the salicide layer while enabling precise metal gate removal.
Solution Approach 2:
The patent applies preliminary action by forming the hard mask and protective dielectric layers before the etch-back process begins. These protective structures are pre-configured to protect the salicide layer during subsequent etching operations, ensuring that the protection is in place before any damage can occur.
2Reliability
If a hard mask is formed on the vertical structure, then underlying layers are protected during etch-back, but the device structure becomes more complex
Solution Approach 1:
The dielectric layers serve multiple functions: they act as hard masks during etching, provide lateral protection on sidewalls, and can be selectively removed after protecting the salicide layer. This multi-functionality reduces the need for separate protective structures, thereby limiting the increase in device complexity while maintaining high reliability.
Solution Approach 2:
The protective dielectric layers are self-aligned to the vertical structure, with the first dielectric layer forming naturally at the top surface and the second dielectric layer conformally coating the sidewalls. This self-alignment reduces the need for additional alignment steps and complex patterning processes, limiting the increase in manufacturing complexity.
Data Source
AI summary
According to an exemplary embodiment, a method of forming a vertical device is provided. The method includes: providing a protrusion over a substrate; forming an etch stop layer over the protrusion; laterally etching a sidewall of the etch stop layer; forming an insulating layer over the etch stop layer; forming a film layer over the insulating layer and the etch stop layer; performing chemical mechanical polishing on the film layer and exposing the etch stop layer; etching a portion of the etch stop layer to expose a top surface of the protrusion; forming an oxide layer over the protrusion and the film layer; and performing chemical mechanical polishing on the oxide layer and exposing the film layer.