Liquid Ejection Head Dual Protective Films for Silicon Protection

The patent applies preliminary cleaning actions (O2 plasma treatment, UV irradiation, or ozone treatment) to the silicon substrate before forming the protective film. This preliminary action removes organic residues and contaminants from the substrate surface, ensuring that when the protective film is subsequently formed, it adheres properly without peeling. The cleaning is performed in advance to prevent contamination issues that would otherwise compromise the protective film's effectiveness.

Instead of etching the protective film to remove contamination (the conventional approach), the patent inverts the sequence: it first cleans the substrate surface using plasma or UV treatment, then forms the protective film on the already-cleaned surface. This inversion ensures that the protective film is formed on a contamination-free surface, eliminating the need to etch it away later, and thus preserving bonding strength while achieving thorough contamination removal.

The patent segments the protective film into two distinct layers: a first protective film (such as silicon oxide or silicon nitride) formed directly on the silicon substrate, and a second protective film (such as silicon carbide) formed on top of the first film. This segmentation allows each layer to serve specific functions - the first layer provides strong substrate adhesion while the second layer provides enhanced chemical resistance and coverage. The segmented structure eliminates peeling phenomena while maintaining manufacturing feasibility through sequential deposition processes.