Film Densification Furnace

Film densification and wafer degassing both prepare a wafer's existing films for whatever comes next, rather than changing the pattern or adding new material — densification bakes a deposited film into a denser, more stable final form, and degassing drives absorbed moisture and trapped gas out of films and surfaces before they can cause problems in a later vacuum or high-temperature step.

Densification matters most for films deposited at low temperature, since low-temperature growth is exactly what leaves a film porous in the first place. A film grown at lower temperature to limit thermal budget — a spin-on dielectric, certain low-temperature CVD oxides — often forms with more porosity and weaker bonding than a high-temperature-grown equivalent, because the growing film doesn't have enough thermal energy during deposition to fully rearrange into its most compact structure. A separate densification bake afterward supplies that missing thermal energy on its own schedule, collapsing porosity and improving the film's density, etch resistance, and moisture uptake without forcing the deposition step itself to run hotter than the rest of the process allows.

Degassing exists because a wafer that outgasses inside a vacuum chamber contaminates every process running in that chamber, not just the wafer carrying the moisture. Trapped moisture or gas in a film releases when the wafer hits vacuum and elevated temperature, and that released gas doesn't stay localized — it raises the chamber's background pressure and can redeposit as contamination on the very wafer it came from, or linger to affect the next wafer processed in the same chamber. A dedicated degas step run before the wafer ever enters a sensitive vacuum process removes that risk at the source, rather than letting the process chamber discover the contamination the hard way.

Densification and degassing are both quiet, easy-to-overlook steps that exist purely to prevent specific downstream failures — porosity-driven reliability problems in one case, vacuum contamination in the other — and skipping either doesn't produce an obviously bad wafer immediately, just a problem that shows up later and somewhere else in the flow.