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MEMS Advanced Materials and Fabrication Methods - Nat. Aca. Press Part 9

Tham khảo tài liệu 'mems advanced materials and fabrication methods - nat. aca. press part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Microelectromechanical Systems Advanced Materials and Fabrication Methods 1997 http www.nap.edu openbook 0309059801 html 43.html copyright 1997 2000 The National Academy of Sciences all rights reserved ASSEMBLY PACKAGING AND TESTING 43 is a good deal of engineering know-how in the electronics sensors and actuators industries. The sections below briefly describe some of the issues involved. Handling Issues In many cases MEMS contain moving parts that are fragile and that may not be protected through the standard IC-wafer passivation step. Because of their vulnerability extra care must be taken with them. For placement IC dice can be handled by vacuum pickups that attach to the top surface of the chip. But vacuum pickups may be unacceptable for MEMS dice because of their generally nonplanar surfaces. Some manufacturers have found ways of using conventional handling equipment for MEMS chips by modifying it to account for specific MEMS sensitivities. Dicing For components that are bulk micromachined the deepetching techniques used as part of the process can sometimes be used to partially or fully separate an individual die from the wafer during the machining process. Another technique that can be used with some devices is bonding an additional wafer or wafers to the first micromachined wafer and then separating the protected sandwiched structures. Many structures that are bulk micromachined cannot be handled in these ways however and other techniques must be found for separating dice without damaging or rupturing sensitive structures e.g. diaphragms or inadvertently depositing silicon particulates in around or under sensitive structures. There are similar problems with parts that are surface micromachined which has encouraged efforts to encapsulate mechanical parts locally prior to separating the wafer into dice. Four generic approaches to dicing MEMS wafers have been used. The first approach is to cover the structure with a permanent cap e.g. Motorola uses this .