Stiction-free release etch with anhydrous HF/water vapor processes

In today's MEMS fabrication, stiction remains one of the fundamental manufacturability challenges. A major step towards eliminating stiction problems is the use of a gas-phase process for the beam release. To date, an anhydrous HF/water vapor MEMS release process has been in production for two years with excellent repeatability and reliability. This stiction-free anhydrous HF/water vapor MEMS release process for accelerometers has been further characterized to determine and solve manufacturing challenges associated with the differences between aqueous-based and vapor-phase release processes. Detailed process characterization to further understand material compatibility with the HF/water vapor release process has been investigated. Various films such as oxides and nitrides of silicon, photoresist, and metals such as gold and aluminum have been characterized for their compatibility with the anhydrous HF/water vapor MEMS release process. Initial results with wafer dicing films are promising as these films show little degradation during extended vapor-phase release processes. The resistance of the wafer dicing films to the anhydrous HF/water vapor process makes it possible to complete the sacrificial oxide release process after substrates have been diced.