Investigation Of Device Level MEMS Vacuum Fusion Packaging

During the development of MEMS, the ratio of the packaging cost to its total system cost in the whole MEMS devices is increasing due to its difficulty in packaging. The vacuum packaging is still the challenge of MEMS packaging. China still needs to break through the key technology of MEMS vacuum packaging, therefore vacuum packaging cannot be realized in China and there are no resources available. For the reasons above, the national 863 program approved the program of"Low Cost & High Yield MEMS Vacuum Packaging Based on the Metal Packaging", with the hope to bring the break through to vacuum packaging.In order to conduct vacuum packaging, vacuum should be measured in a very small space in the MEMS devices first. This thesis presents a method using the theory of resistance of quartz oscillator change with the pressure change in the circumstance and evaluates some factors which influence the vacuum measurement. Bubble test and helium bomb test are used to detect the leak rate of the MEMS devices.By comparing all the methods of vacuum packaging in and abroad and aimed the situation of our country, this thesis proposes fusing welding packaging to achieve device level MEMS vacuum packaging. Based on the vacuum fusion welding instrument, this thesis investigates the process of current metal packages. The theoretical analysis and long time vacuum measurement after vacuum packaging show that the current metal packages cannot maintain long time vacuum maintenance.In order to make the long term credible vacuum maintenance, this thesis designs MEMS packages for the vacuum packaging and has done a great deal of experiment work. This thesis investigates the influence on vacuum packaging of coating metal and provides the coating metal with appropriate thickness. Many experiment show the yield rate of finished products is more than 90%. Strength experiment has been conducted. The theoretical calculation and measurement provide the theoretical life of MEMS devices after vacuum packaging. The accelerated test of a set of devices provides the time of vacuum maintenance. The results of two calculation methods of theoretical life are almost identical which shows the feasibility of long time vacuum maintenance.