The use of cross-section haze measurements to monitor Laser Spike Anneal (LSA) stage alignment

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In complex integrated circuits, transistor elements are essential circuit elements that determine the overall performance of the semiconductor device. Improvements in the performance of transistor devices leads to differently doped regions that are formed in the semiconductor substrate. For high performance transistors, very shallow dopant junctions are in contact with the source/drain regions and partially beneath the gate electrode in the semiconductor substrate. Activation of the dopants in these junctions, as well as dopants in deep source/drain regions, can be achieved using a very fast laser heating process known as laser spike annealing (LSA).The Laser Spike Anneal (LSA) process has stringent quality requirements. On the one hand, temperature-stable annealing must be guaranteed, which requires stable operation of the laser (e.g., energy density, beam profile). Accurate positioning of the wafer in the LSA process tool is also important. Should the wafer be misaligned, the laser may go beyond the edge die and make contact with the bevel, resulting in a high risk of wafer breakage. In addition, correct and stable alignment enables annealing with significantly smaller edge exclusions.The integrated SURFmonitor™ feature of the KLA Surfscan® SP5, a defect inspection system for blanket wafers, was utilized successfully to highlight the variation of the LSA process performance.The study will focus on ensuring correct positioning of the wafer during the anneal process. Monitoring the stability of the annealing process is well known and is only mentioned here in passing.