The effect of long-term contact on adhesion force between MEMS silicon surfaces is investigated. A test structure is developed that can initiate the contact between the two surfaces without actuation. Therefore, the surfaces may remain in contact for a long period of time. The contacting surfaces are separated using a thermal actuator and the adhesion force is determined utilizing FEM simulations. Freshly released and long-time stored devices were tested, and their adhesion force is determined. The test results show that the adhesion force for devices in contact for a long time is drastically larger than those with short-term contact. Adhesion force values as large as 2.9 μN for long-term contact and as small as 0.4 μN for fresh contact were measured. The large adhesion force associated with long-term contact is believed to be attributed to the formation of native oxide at contacting nano-asperities and formation of covalent bonds between the surfaces, requiring larger force to break the bonds.

This content is only available via PDF.
You do not currently have access to this content.