Mechanical stress monitoring sensor for 3-d module during manufacturing and operation

In three-dimensional packaging module which have been used in electronic equipment, the size of partial interconnections and total structure have been continuously miniaturized for improving the performance of the products. Due to the fluctuation of the mechanical properties of the component materials and the drop impact towards the fragile modules during manufacturing and operation, the final residual stress varies easily in a chip of the 3-D structure. Both the static and dynamic changes of the stress distribution induce the variation of the performance of electronic devices and the degradation of their long-term reliability. It is, therefore, important to control and optimize the residual stress quantitatively. In this study, a stress sensor which can monitor the change of the local residual stress in 3-D module was developed by applying the piezoresistance effect of single-crystalline silicon. The sensor was embedded in a silicon chip, and it can measure the periodic stress in a silicon chip assembled by area-arrayed bump structure. The impact stress during the manufacturing process was successfully monitored by using this sensor. It was also confirmed that the effective amplitude of the impact stress varies drastically depending on the mechanical properties of the stacked thin films.