ZrCoCe Getter Film Solution for Under Controlled Atmosphere MEMS Packaging

Abstract

Abstract. In order to specifically support the technology trend of increased miniaturization of Micro Electro Mechanical Systems (MEMS) devices, highly porous ZrCoCe non-evaporable getter (NEG) film has been produced by DC magnetron sputtering from a preformed ZrCoCe alloy target. The porous film is composed of columnar crystals, which is further built up with assembled ZrCoCe amorphous or nanocrystalline grains. Gas sorption investigation shows that this film can be activated at low temperature and exhibits excellent stable sorption characteristics. Sorption properties can be further improved with elevating the activation temperatures due to the microstructure modification. The capability of ZrCoCe films withstanding wafer physical or chemical cleaning processes is investigated, indicating their compatibility with MEMS vacuum packaging and the appropriate way to store them. IntroductionDiscrete packages are very critical to assure an excellent hermeticity in many MEMS devices to perform their basic functions properly and to enhance their reliability by keeping these devices away from the harmful external environment [1][2][3][4]. With the technology trend of increased miniaturization of MEMS devices, maintaining the needed vacuum level in such packages for the entire MEMS device life becomes a real technical challenge due to the very high surface to volume ratio [1]. The most common and technically accepted way to maintain a controlled ambient environment in a hermetically sealed MEMS device is to use a NEG capable of chemically absorbing active gasses, such as H 2 O, CO, CO 2 , O 2 , N 2 and H 2 . However, the conventional bulk or sheet getters having the property of high pumping speed even at room temperature, could not be used in these minimizing MEMS devices due to the restricted space [5][6][7]. It is urgently required to develop the highly porous thin-film-type getters with several μm thickness for the applications of MEMS vacuum devices.Ti, Ti-Zr-V, Zr-V-Fe or ZrV 2 are typical NEG film materials, which have been widely studied in sealed-off vacuum technology. Nevertheless, the aforementioned materials may be defined as NEG materials of specific use, and are often described and referred to in patents and technical or commercial bulletins with reference to their use in specific applications [8][9][10]. Zr-Co-rare earth (RE) alloys are specially developed to fulfil some specific integration needs. These alloys are advantageous because they are suitable for general use. they have a relatively low activation temperature 200-500°C, are capable of sorbing a wide variety of gases, and minimize the environmental and safety risks compared with known nonevaporable getter alloys [11].It is known from previous studies that ZrCoRE films have been prepared by RF magnetron sputtering and sorption properties can be improved by optimizing related parameters [12,13]. However, the performance of the above films are too low to fulfil practical applications and mass production. More efficient sorption capacity and higher sta...