Vertical Device Hard Masking for Salicide-Selective 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 developed to form a hard mask of a dielectric layer over vertical structures, protecting underlying layers and facilitating the etch-back process, particularly in vertical gate-all-around (VGAA) procedures, allowing for less stringent lithography requirements and easy removal of the hard mask.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional etch-back process is used without a hard mask, then the process is simple, but there is no selectivity between salicide and metal gates causing manufacturing complications
Solution Approach 1:
A hard mask layer is formed over the metal gate structure before the etch-back process begins. This preliminary action provides the necessary selectivity during etching, allowing the metal gate to be removed while protecting the salicide contact regions. The hard mask is subsequently removed after serving its protective function.
Solution Approach 2:
The hard mask layer acts as an intermediary protective layer between the etchant and the underlying structures. It enables selective etching by being removable under specific conditions while protecting the salicide regions during the metal gate removal process, thus mediating the interaction between the etchant and the device structures.
2Reliability
If a hard mask is formed over vertical structures, then protection of underlying layers is improved, but the device structure becomes more complex
Solution Approach 1:
The hard mask is formed preliminarily over the vertical structures before critical etching operations. This preliminary protective layer ensures that underlying layers are protected during subsequent processing steps. After the protective function is fulfilled, the hard mask is removed, returning the structure to its original state without permanent complexity.
Solution Approach 2:
The hard mask is introduced as a temporary protective element that is discarded after serving its protective function. This allows the underlying layers to be protected during critical operations, and then the hard mask is removed entirely, leaving no permanent structural complexity in the final device.
3Manufacturing precision
If self-aligned method is used to form hard mask, then lithography requirements are less stringent, but additional process steps are required
Solution Approach 1:
The hard mask is formed using a self-aligned method where the mask material is deposited conformally over the vertical structures, and then planarized to a flat top surface. This preliminary self-alignment eliminates the need for additional lithography alignment steps, reducing lithography precision requirements while maintaining manufacturing efficiency.
Solution Approach 2:
The self-aligned hard mask formation process uses the vertical structures themselves to define the mask pattern, eliminating the need for separate lithography alignment operations. The conformal deposition and planarization steps automatically align the hard mask with the underlying structures, allowing the process to self-align without additional lithography steps.
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.