Stress-induced dislocations in silicon integrated circuits

Many of the processes used in the fabrication of silicon integrated circuits lead to the development of stress in the silicon substrate. Given enough stress, the substrate will yield by generating dislocations. We examine the formation of stress-induced dislocations in integrated circuit structures. Examples are presented from bipolar and MOS-based integrated circuit structures that were created during developmental studies. The underlying causes of oxidation-induced stress and the effect on such stress of varying oxidation conditions are discussed. The knowledge thus gained is used to explain dislocation generation during the formation of a shallow-trench isolation structure. The importance of ion-implantation processes in nucleating dislocations is illustrated using structures formed by a deep-trench isolation process and a process used to form a trench capacitor in a DRAM cell. The effect of device layout geometry on dislocation generation is also examined. We show how TEM observations can be used to provide more information than solely identifying those process conditions under which dislocations are generated. By combining TEM observations with stress analysis, we show how the sources of stress responsible for dislocation movement can be identified.