EUV Mask Blank Reflective Layer Protection Process
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Solution Overview
Problem
In EUV exposure technology for semiconductor production, the protective layer in mask blanks often becomes contaminated with foreign particles, leading to voids that compromise the protective function and risk damage to the reflective layer during etching, causing phase defects and deteriorating mask quality.
Innovation Solution
A process involving the formation of a reflective layer, a first protective layer, cleaning to expose the reflective layer, and a second protective layer to cover the exposed areas, ensuring the reflective layer is protected during etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective layer is formed on the reflective layer to prevent damage during etching, then the reflective layer is protected from etching damage, but foreign particles contaminate the protective layer creating voids that compromise the protective function
Solution Approach 1:
The protective layer is divided into multiple layers (first protective layer and second protective layer) with different functions. The first protective layer serves as the primary etching stop layer, while the second protective layer fills defects and provides additional protection, ensuring complete coverage even when the first layer contains voids from foreign particle removal
Solution Approach 2:
A first protective layer is formed on the reflective layer before cleaning to remove foreign particles. This preliminary protective layer prevents direct exposure of the reflective layer to damage during the cleaning process, allowing safe removal of contaminants that would otherwise create harmful voids
2Manufacturing precision
If foreign particles are removed from the protective layer by cleaning, then the protective layer quality is improved, but voids remain at portions where foreign particles existed compromising the etching stop function
Solution Approach 1:
The second protective layer is formed to fill and cover the voids created by foreign particle removal in the first protective layer. This additional layer acts as a cushioning backup, ensuring that the etching stop function is maintained even where the first layer has defects
Solution Approach 2:
The protective structure uses composite material layers with different properties. The first protective layer provides the primary etching stop function, while the second protective layer compensates for defects and provides redundant protection, creating a composite structure that combines the advantages of both layers
Data Source
AI summary
A process for producing a reflective element for a mask blank, of which a reflective layer is hardly damaged at the time of etching treatment of an absorber layer. A process for producing a reflective element for a mask blank, which comprises (1) a step of forming a reflective layer on a first surface of a substrate, (2) a step of forming a first protective layer on the reflective layer, (3) a step of cleaning the substrate to form an exposed part of the reflective layer, which is not covered with the first protective layer, and (4) a step of forming a second protective layer on the first surface of the substrate to cover the exposed part of the reflective layer with the second protective layer.