Halftone Mask Etching Stopper Layer Material Selection

The patent changes the chemical parameters of the etching process by selecting etching stopper layer materials (silicon oxide, silicon nitride, silicon oxynitride, or metal oxides) that are selectively etchable by wet etching with nitric acid-based solutions. This material selection enables the use of lower-cost wet etching processes while maintaining adequate etching selectivity between layers.

The patent replaces expensive and environmentally harmful fluorine-based etching liquids with nitric acid-based etching liquids that are less harmful to the environment. The nitric acid-based etching solution provides sufficient etching selectivity without generating hazardous fluorine exhaust gases, making the process more environmentally friendly.

The patent simplifies etching liquid management by using nitric acid-based etching liquids instead of fluorine-based liquids. The nitric acid-based solutions are easier to manage, store, and dispose of, eliminating the complex recovery and handling procedures required for fluorine-based etchants.

The patent combines multiple functions into fewer process steps by using an etching stopper layer that provides both the etching stop function and the light shield function. This eliminates the need for separate light shield layer formation and reduces the number of alternating film formation and etching cycles, thereby shortening processing time while maintaining processing accuracy.

The patent segments the mask structure into distinct functional layers: transparent layer, etching stopper layer, and light shield layer. This segmentation allows each layer to be optimized for its specific function and enables efficient manufacturing processes. The etching stopper layer acts as a sacrificial layer that defines the semi-transparent regions, while the light shield layer provides optical shielding, enabling multi-tone patterning without requiring excessively large mask sizes or complex data sets.