Plasma-enhanced chemical vapor deposition

Plasma enhanced chemical vapor deposition (English plasma enhanced chemical vapor deposition, PECVD, . Also Engl plasma -assisted chemical vapor deposition, PACVD, called ) is a special form of the chemical vapor deposition ( CVD), wherein the deposition is assisted by a plasma. The plasma can burn directly from the substrate to be coated ( direct plasma method) or in a separate chamber ( remote plasma method).

Operation

While the CVD dissociation ( breaking up ) of the molecules of the reaction gas by external application of heat and the energy released by the following chemical reactions happen, this task is performed in the PECVD accelerated electrons in the plasma. In addition to the radicals formed in this manner ions generated in a plasma, which cause the film deposition on the substrate together with the radicals. The gas temperature in the plasma increases, as a rule only a few hundred degrees Celsius, which in contrast to CVD also more temperature sensitive materials can be coated.

In the direct plasma method, a strong electric field is applied between the substrate to be coated and a counter-electrode, whereby a plasma is ignited. In the remote plasma method, the plasma is so arranged that it does not have direct contact to the substrate. Advantages are achieved with respect to selective stimulation of individual components of a process gas mixture, and reducing the possibility of plasma damage to the substrate surface by the ion. Disadvantages are possibly the loss of radicals on the distance between the remote plasma and the substrate, and the possibility of gas phase reactions prior to the reactive gas molecules reaching the substrate surface.

Plasmas can also be inductive / capacitive generated by irradiation of an alternating electromagnetic field, which electrodes are superfluous.

Examples

With PECVD can be amorphous silicon, silicon nitride, silicon dioxide and silicon - oxide-nitride- connections and much more precipitate (eg carbon nanotubes ).

Layers of the semiconductor material silicon is made ​​of monosilane and silicon tetrachloride:

Dielectric layers of silicon dioxide can be prepared from, for example, monosilane and nitrogen:

For passivation of silicon nitride layers used can be prepared from mono-silane and nitrogen:

Layers of aluminum, in the switching elements has the function of an electrical conductor, can be prepared from aluminum chloride and hydrogen: