Laser Closing of Window as a Novel Wafer-Level Hermetic Packaging Technology

We propose a novel method to achieve wafer-level, localized, high-vacuum encapsulation that is fully compatible with CMOS/MEMS processing for the packaging of electronic and MEMS devices and sensors. The same technology can also seal-in any desired chemical atmosphere at a wide range of pressure (including above atmospheric pressure). It is entirely thin film based and therefore does not need precision placement of external parts. The key to this technology is a laser reflow process to seal small windows with metal film. The metal layer will be molten for only nanoseconds during the reflow process and high temperature zone is entirely contained within the sealing layers. The devices being encapsulated remain at room temperature and are completely unaffected. The resulting encapsulation is very rugged and is very forgiving of the surface condition of the wafer, allowing electrical feed throughs to be accomodated easily. Other features include high reliablility, large process margin and very high throughtput. It utilizes standard, proven process technology to achieve high yield and low cost.