Vertical Gate Hard Mask for Selective Metal Gate Etch-Back
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Solution Overview
Problem
The challenge in manufacturing semiconductor devices is the lack of selectivity between salicide and metal gates during the etch-back process, which complicates the fabrication of metal gates.
Innovation Solution
A self-aligned method is employed to form a hard mask on top of a vertical structure as a stop layer, protecting underlying layers during subsequent processes such as forming and patterning work function metal layers or metal gate layers. This method requires less stringent lithography processes and can be implemented in vertical gate-all-around (VGAA) procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional etch-back process is used for metal gates, then manufacturing process can be simplified, but selectivity between salicide and metal gates is lost causing fabrication complications
Solution Approach 1:
The patent segments the gate structure into distinct components: a salicide layer and a separate metal gate layer. This segmentation allows selective etching of the metal gate layer while preserving the salicide layer, resolving the selectivity issue. The hard mask is also segmented to provide differential protection during etching processes.
Solution Approach 2:
The patent introduces a hard mask as an intermediary layer between the salicide and metal gate layers. This hard mask serves as a protective mediator during etch-back processes, enabling selective removal of the metal gate layer while protecting the underlying salicide layer, thus achieving the required selectivity.
2Ease of manufacture
If self-aligned method is used to form hard mask, then lithography process stringency is reduced, but additional process steps are required
Solution Approach 1:
The patent employs preliminary action by forming the hard mask layer and patterning it using self-aligned lithography before the metal gate deposition. This preliminary patterning establishes the gate structure boundaries in advance, allowing subsequent metal gate formation to be precisely positioned without requiring high-stringency lithography, thus reducing overall lithography demands.
Solution Approach 2:
The patent merges multiple functions into the hard mask layer: it serves as a protective layer during etching, a patterning template for self-aligned lithography, and a structural element defining the gate geometry. This consolidation reduces the need for separate process steps and simplifies the overall manufacturing flow despite the added hard mask formation step.
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.