Wednesday, August 11, 2010

LSA experimental setup and conduction.

They used bare silicon wafers as the starting substrate. The wafers were processed through the laser anneal tool prior to inspection. Firstly, one wafer was wafer at six different temperatures at and around the process center line T°C (T-75°, T-50°, T-25°, T, T+25°, and T+50°); this minimized the effects of incoming wafer qualty on the final surface morphology. 
Wafer Schematics

Fig. 2 shows the anneal splits above. Subsequent LSA experiments utilized one wafer with one or two process conditions to verify whether this characterization is reproducibile, and for further understanding of the variations in the annealing process.

They measured the samples via KLA-Tencor’s Surfscan SP2 unpatterned wafer inspection
system. The scans were done under normal (perpendicular) incidence in high-throughput mode–the optimal scan condition for slip line detection and other shallow defects because of their defect scattering characteristics. Also, they obtained surface morphology information from the haze scattering detected on the SP2 by analyzing the so-called SURFimage (don't know what this). The SURFimage haze maps provided local surface information at pixel-level resolution and sub-nm vertical resolution. The resulting data is presented in 192-bit greyscale for clear visualization of surface variation. Each anneal zone had its haze data obtained through a newly developed capability (developed in-house) that enables local data extraction, analysis, and defect binning of local surface scattering signals using user-defined parameters. From this analysis, they correlated the results to LSA process conditions. Lastly, the authors conducted further corroboration by Scanning electron microscope.