The formation, imaging, and application of thin silicon-dioxide membrane

Abstract

We have successfully formed and separated a very thin silicon-dioxide (SiO 2) film with a thickness of approx. 1 nm. The thin SiO 2 film was chemically grown on Si using a wet chemical treatment which is commonly used in semiconductor manufacturing. Highly selective etching of the underlying Si, through the native oxide, can be achieved using chlorine (Cl 2) gas. Such a unique phenomenon allows the formation and separation of native oxide from the Si surface. The native oxide film, which is suspended at its edges by thick-SiO 2, remains at the original level of the Si surface even after etching. The suspended Si-native oxide membrane is imaged using scanning electron microscopy (SEM). It is presumably the thinnest separated film ever recorded. The ∼1-nm-thickness SiO 2 membrane suspended by thick-SiO 2 can support subsequent film deposition. The sequential processes of native oxide formation on patterned Si, etching the Si by Cl 2 through the native oxide, and film deposition onto the native oxide membrane, can make a cavity in the solid-state substrate. This novel technique of creating a cavity by using a membrane of Si-native oxide can be applied to fabricate 3D micro-systems like pipes, diaphragms, tubes, and wave-guides on the solid-state circuits.