There are several types of hard masks, each with specific applications and properties: - Single-layer hard masks: Consist of a single material layer, such as SiO2 or Si3N4. They are simple to apply but may have limited etch selectivity. - Multi-layer hard masks: Combine different materials to enhance etch selectivity and process compatibility. For example, a layer of SiO2 may be combined with a metal layer to improve performance. - Organic hard masks: Made from organic materials, these are less common but can offer unique properties for specific applications.
