Seed layer in the sputtering material plays a key role as the "glue".

The seed layer plays an important role in the sputtering process, which is a technique commonly used in the preparation of thin metal films. The seed layer is an extremely thin metal film, usually between a few nanometers and tens of nanometers thick, that is applied to the surface of the substrate as the starting point for the metal film.

The seed layer has the following main functions in the sputtering process:

Increase Adhesion: The seed layer provides a good adhesion surface to ensure that the subsequent sputtered metal film adheres firmly to the substrate. It forms a smooth interface on the substrate surface, which helps reduce defects and interfacial stresses and improves the adhesion and structural stability of the metal film.

Provide nucleation formation: The seed layer usually has good crystallinity and can be used as a nucleus to help the crystalline growth of metal thin films. This is important to obtain high quality, near single crystal metal films.

Homogenization layer thickness: The homogeneity of the seed layer is essential for the uniform growth of the metal film in the subsequent sputtering process. It provides a uniform starting point, allowing the metal film to grow in a uniform manner over the entire substrate surface, avoiding thickness variations or discontinuities.

Improved conductivity: Certain seed layer materials have inherently good conductivity and can improve the conductivity of the entire metal film structure. This is critical in many applications, such as electronic components and solar cells. Commonly used seed layer materials include nickel (Ni), chromium (Cr), titanium (Ti), titanium alloys (e.g. TiN), etc. The selection of the appropriate seed layer material depends on the properties of the desired metal film, process conditions and application requirements.