Raman Investigation of Stress for Shallow Trench

A trench is used as a storage capacitor in dynamic memory (DRAM) technologies (deep storage trenches), or as an isolation structure in CMOS, bipolar and BiCMOS technologies. But a shallow trench structure has also been shown to be a major factor in substrate defect generation during processing. Such defect generation is directly related to mechanical stresses existing around the trench. This stress can be monitored, using Raman spectroscopy, to a stress resolution of 10MPa and a spatial resolution of 0.2μm. In this paper, a trench structure is designed and fabricated, and the test results for local stresses within the trench are shown to be in good correspondence with theory.