MEMS Retroreflector Fabrication and Packaging
- Optical MEMS,
- corner cube retroreflector (CCR),
- hermetic packaging,
- flip chip bonding
Integration of 3-D devices, IC or MEMS, often requires a handle wafer which is removed before final packaging of the devices. This process usually uses lapping, chemical etch or high temperature heating to de-bond the handle wafer. A new technique to release a Pyrex handle wafer using laser ablation is presented. Pulsed energy, from a 248nm excimer laser is delivered transparently through the Pyrex handle wafer. This causes delamination of the bonded silicon structures from the handle wafer. This technique offers fast throughput at chip and wafer levels and protects the fragile and delicate active devices from harsh physical, chemicals and potential thermal stresses. We present a method wherein the handle wafer used in 3-D assembly of a MEMS device was released using laser micromachining. A Pyrex handle wafer rigidly supports anisotropically etched, through-silicon wafer, vertical mirrors during thermo-compression bonding to active MEMS parts. After this first thermo-compression bond, the Pyrex handle wafer was lifted off using laser ablation, leaving clearance for additional bond steps, which includes additional components and a package frame. Multiple Au-Au thermo-compression bonds of vertical surfaces onto a single MEMS chip were performed, to assemble and package 3-D MEMS devices.
- T. D. Sands, "Excimer laser lift-off for packaging and integration of GaN-based light-emitting devices," Proceedings of SPIE Vol. 4977, 2003.
- C. K. Wong,et al, "A wafer level packaging for pressure sensors MEMS," Micro System Technologies, pp. 123-130, 2003.
- .Y. L. Ramseyet al“Packaging micromechanical devices,” U.S. Patent 6,603,182, August 5, 2003.
- K. A. Peterson, et al“Sealed symmetric multilayered microelectronic device package with integral windows,” U.S Patent 6,489,670, December 3, 2002.
- S. Samson et al, "Fabrication Processes for Packaged Optical MEMS Devices," 2005 ICMENS Conference, July 24-27, Banff, Canada.
- L. Zhou et al“Corner-cube retroreflector based on structure-assisted assembly for free-space optical communication,” Journal of Micromechanics and Microengineering, Vol. 12, pp. 233-242, 2003.
- W. Wanget al"Small form factor microsensor system using optical MEMS for passive optical digital communications (PODC)," Proceedings. of SPIE, Vol. 6556, pp. 1-10, Orlando, 2007.
- S. Kediaet al“Total internal reflection-based free space optical communication system”, Journal of Microelectromechanical Systems 24 (5), 1632-1641
- Andrew S. Holmes,“Laser fabrication and assembly processes for MEMS”, SPIE proceedings in laser applications in Microelectronic and Optoelectronic Manufacturing VI; Volume 4274 (2001)
- Pethig et al, “Development of biofactory-on-a-chip technology using excimer laser micromachining”, J. Micromech. Microeng.8 , pp. 57-63, 1998.
- D.C. Sheridan et al, “Demonstration of Deep (80μm) RIE Etching of SiC for MEMS and MMIC Applications,” in Proc. Int. Conf. on Silicon Carbide and Related Materials 1999, pp. 1053–1056.
- L. Jiang and R. Cheung, "Fabrication of SiC microelectromechanical systems using one-step dry etching," J. Vac. Sci. Tech. B, Vol. 6, Issue 21, pp. 2998-3001, 2003.International Journal For Research In Electronics & Electrical EngineeringISSN: 2208-2735Volume-4 | Issue-4 | March, 20187