Plasma enhanced CVD of thin films using hexamethyldisiloxane and octamethyltetrasiloxane monomers
|Type:||Article in Proceedings|
|Keywords:||PECVD; HMDSO; OMCTS|
Siloxane polymers prepared by chemical methods are characterized by high flexibility, gas permeability and low surface energy. Due to their properties they find many applications in medicine and other fields. A little bit different group of materials are organosilicon films prepared by plasma enhanced chemical vapor deposition (PECVD) combining chemical and physical approaches. Monomers used in PECVD include usually hexamethyldisiloxane (HMDSO) and tetraethoxysilane (TEOS) often mixed with O$_2$ for deposition of inorganic SiO$_2$-like films. Rarely, some other monomers like octamethyltetrasiloxane (D$_4$) are applied but, in PECVD, their structure is usually not retained because of their substantial dissociation. As a result, highly cross-linked polymers in which a repetition unit is not well defined are deposited. However, it can be modified by using pulsed plasmas in which the processes are driven by energetic electrons and ions during an on-time whereas free radicals and activated surface play an important role in an off-time phase. Changing the on-time and off-time a different retention of monomer structure can be achieved.