XeF2 Vapor-phase Etching
XeF2 vapor-phase etching is a powerful etching technique for microelectronics fabrication.
The chemical reaction of silicon etching process using XeF2 vapor is as follows.
2XeF2 + Si → 2Xe (g) + SiF4 (g)
Silicon surface reacts with XeF2, and forms byproduct molecule of SiF4.
This non-plasma etching process shows unlimited etch selectivity of silicon against other materials such as photoresist, metals (Al, Ni, Cr) and compound semiconductor (GaAs, ZnO, PZT). The main application of this process is isotropic silicon etching for MEMS structure release such as cantilevers.
XeF2 Etch System
The SAMCO VPE-4F is a Xenon Difluoride (XeF2 ) etch system which is designed primarily for the etching of silicon sacrificial layers in the processing of self-standing MEMS devices. This isotropic etch process shows high etch selectivity of silicon against PDMS, parylene, SU8, silicon dioxide (SiO2) and silicon nitride (SiNx).
The etch process is completely dry, and eliminates the stiction problems that occur during conventional wet etching process. In addition, the space efficient design makes the system ideal for desktop use in research and development.
SAMCO’s XeF2 Etch System is designed to offer repeatable release etch solutions for MEMS devices.
Main Unit : 400(W) x 600(D) x 430(H) mm
– minimizes space requirements
– no physical damage and charging caused by plasma discharge
Complete Dry Process
– prevents stiction damage which can be seen in wet etch process
– eiminates the need for pre-processing and post-processing that are required with wet process
Pulsing of the Gas Flow
– enables easy control of the etch rate and the gas consumption rate
MEMS spiral structure after Si sacrificial layer etching
1 μm gap was formed using Si sacrificial layer etching and , and movable parylene structure was released.
Photo courtesy of Aoyagi lab at Kansai University