Mumbai University > Electronics Engineering > Sem 8 > MEMS Technology

Marks: 2M

Spin-On is a process to put down layer of dielectric insulators and organic materials.

The equipment is simple, requiring a variable speed spinning table with appropriate safety screens.

A nozzle dispense the material as a liquid solution in the center of the wafer. Then Spinning the substrate at speeds of 500 to 5000 rpm for 30 to 60 seconds spreads the material to a uniform thickness.

Photoresists and polyimides are common organic materials that can be spun on a wafer with thickness typically between 0.5 and 20 µm, though some special purpose resists such as epoxy based SU-8 can exceed 200 µm.

Thic (5-100µm) spin-on glass (SOG ) has the ability to uniformly coat surfaces and smooth are underlying topographical variations, effectively planarizing surface features.

Thin (0.1 – 0.5 µm) SOG was used in IC as an interlayer dielectric between metals for high speed electrical interconnects , but its electrical properties are poor compared to thermal or CVD SiO2.

Spin-On Glass are available in different forms as siloxane or silicate-based.

Silicate-based allows water absorption into the film, resulting in higher relative dielectric constant and a tendency to crack and after deposition, the layer is densified at a temp.