Metrology of Warpage in Silicon Wafers Using X-ray Diffraction Mapping

X-ray Diffraction (XRD) mapping is a non-destructive metrology technique that enables the reconstruction of warpage induced on a Silicon wafer through thermo-mechanical stress. Here, we mapped the wafer's warpage using a methodology based on a series of line scans in the x and y directions and at different 90-degree rotations of the same sample. These line scans collect rocking curves from the wafer's surface, recording the diffraction angle (ω) deviated from the Bragg angle due to surface misorientation. The surface warpage reflects in XRD measurements by inducing a difference between the measured diffraction angle and the reference Bragg angle (ω − ω0) and rocking curve broadening (FWHM). By collecting and integrating the rocking curves (RCs) and FWHM broadening from the whole surface and multiple rotations of the wafer, we could generate 3D maps of the surface function f(x) and the angular misorientation (warpage). The warpage exhibits a convex shape, aligning with optical profilometry measurements reported in the literature. The lab-based XRDI has the potential to be developed to map the wafer's warpage in a shorter time and in situ, as can be perfectly performed in Synchrotron radiation source.