Flash Memory Contact Hole Etching Sidewall Protection
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Solution Overview
Problem
Existing contact-hole plug formation techniques in semiconductor manufacturing lead to a decrease in electrical properties and reliability due to low etching selectivity between silicon oxide materials, resulting in loss of sidewall structures during the etching process.
Innovation Solution
A method involving the formation of a sacrificial sidewall layer and an etching barrier layer with controlled thickness, using materials like silicon nitride and silicon oxynitride, to protect the sidewall structure and enhance etching selectivity, allowing for the formation of a contact-hole plug with improved reliability and electrical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional contact-hole etching process is used, then the etching process can be completed, but the sidewall structure is lost due to low etching selectivity between silicon oxide materials
Solution Approach 1:
A sacrificial sidewall layer made of silicon nitride is introduced as an intermediary protective layer during the contact-hole etching process. This layer is deposited conformally on the sidewalls of the gate structure and hard mask layer, and serves as a mediator that protects the original sidewall structure from being lost during etching. The sacrificial layer can be selectively removed after the contact-hole plug is formed, having fulfilled its protective function.
Solution Approach 2:
The patent employs a composite structure consisting of multiple dielectric layers with different materials (silicon oxide, silicon nitride, silicon oxynitride) to achieve high etching selectivity. Each material layer has distinct etching characteristics that allow the etching process to differentiate between layers, enabling precise formation of contact holes while preserving the sidewall structure. The composite material approach creates a layered architecture where each material serves a specific function in the etching process.
2Reliability
If the sidewall structure is protected during etching, then the electrical properties are improved, but the process complexity increases due to additional layers
Solution Approach 1:
The sacrificial sidewall layer and etching barrier layer are formed in advance before the contact-hole etching process. This preliminary action ensures that the protective structure is already in place when etching begins, preventing sidewall loss without requiring additional steps during the critical etching phase. The layers are deposited conformally on the existing structure, integrating protection into the fabrication sequence rather than adding post-processing complexity.
Solution Approach 2:
The sacrificial sidewall layer is designed to be temporarily present during the etching process and then selectively removed after it has served its protective function. This discarding of the sacrificial layer after use reduces the final device complexity, as the protective layer is not part of the final structure but rather a process aid that is recovered (removed) after completing its mission.
3Manufacturing precision
If high etching selectivity is achieved through material differentiation, then the sidewall structure is preserved, but the manufacturing process becomes more difficult
Solution Approach 1:
The patent utilizes parameter changes in material composition (silicon oxide, silicon nitride, silicon oxynitride) to achieve high etching selectivity. By varying the chemical composition and physical properties of each dielectric layer, the etching process can be tuned to selectively remove specific materials at different rates. This allows the etching process to differentiate between layers based on material parameters rather than requiring complex process controls.
Data Source
AI summary
A method is provided for fabricating a flash memory structure. The method includes providing a substrate; and forming a gate structure and a hard mask layer. The method also includes forming a sidewall structure on side walls of the gate structure and the hard mask layer; and forming an etching barrier layer covering the sidewall structure. In addition, the method includes forming a first dielectric layer; and removing the sidewall structure and the etching barrier layer higher than the first dielectric layer. Moreover, the method includes forming a sacrificial sidewall layer on the side wall of the hard mask layer and above the sidewall structure and the etching barrier layer; and forming a second dielectric layer on the first dielectric layer. Further, the method includes forming a contact hole penetrating through the second dielectric layer and the first dielectric layer; and forming a contact-hole plug in the contact hole.