Mechanical characterization in failure strength of silicon dice

The trend in die size decrease of the microelectronics circuits has been driven by modern IC manufacturing technology. Due to its brittle nature, high stresses induced in the die due to packaging, assembly and reliability test could result in detrimental fracture in the die. Due to its large diameter and thin layer, determination of the fracture strength of a silicon wafer would be difficult. Thus it is more applicable for silicon strength to be characterized at die level. This paper discusses the approach for the characterization of silicon die failure strength employing a simple three-point bending test, thereby providing a better understanding of the stress accumulated in the die before failure. The effects of die thickness, die size and backgrinding patterns on the die stress have been investigated. The results showed that the die strength is largely dependent on its geometry and damages due to wafer processes (surface/edge defects and backgrinding pattern). A set of thickness dependent threshold stress values for die failure has been obtained for wafers that have undergone mechanical grinding. The determined failure stress values would be useful for solving future die failure problems encountered in new packaging and process development work.