Monitoring of local and global temperature non-uniformities by means of Therma-Probe and Micro Four-Point Probe metrology

The introduction of millisecond annealing in advanced CMOS process flows turns out to generate considerable temperature variations which can enhance the device dispersion. In the present work we report on the use of inline Therma-Probe (TP) and Micro Four-Point Probe (M4PP) metrology to assess these temperature variations on shallow trench isolation (STI) wafers with and without absorber layer after sub-melt laser anneal (¿
_laser
= 808 nm). By calibrating the DC probe reflectance obtained during TP or the M4PP sheet resistance against the laser peak temperature on a blanket wafer with calibration stripes, the peak temperature variation on the patterned wafer can be determined at a global and local scale. By a direct comparison on the same structures we demonstrate the equivalence of both techniques and validate the contactless TP measurements. We also demonstrate the advantage of the use of absorber layers during laser anneal.