Nondestructive X-ray diffraction measurement of warpage in silicon dies embedded in integrated circuit packages.

Transmission X-ray diffraction imaging in both monochromatic and white beam section mode has been used to measure quantitatively the displacement and warpage stress in encapsulated silicon devices. The displacement dependence with position on the die was found to agree well with that predicted from a simple model of warpage stress. For uQFN microcontrollers, glued only at the corners, the measured misorientation contours are consistent with those predicted using finite element analysis. The absolute displacement, measured along a line through the die centre, was comparable to that reported independently by high-resolution X-ray diffraction and optical interferometry of similar samples. It is demonstrated that the precision is greater than the spread of values found in randomly selected batches of commercial devices, making the techniques viable for industrial inspection purposes.

The relationship between interface structure, conformality and perpendicular anisotropy in CoPd multilayers.

The relationship between the interface structure and perpendicular anisotropy in sputtered Co/Pd multilayers has been investigated using grazing incidence x-ray scattering and vibrating sample magnetometry. Using fits to a self-affine fractal model of the interfaces, the variation in in-plane correlation length, fractal parameter and conformality has been determined as a function of the number of repeats in the Co/Pd bilayers. As the number of interfaces rises, the roughness becomes predominantly non-conformal and the in-plane length scale associated with the roughness increases as a power law with multilayer thickness. It is suggested that the loss of conformality, characterized by a relatively short out-of-plane correlation length, may be the cause of the reduction in anisotropy energy per interface observed for high numbers of bilayer repeats. There is a weak association between fractal parameter and interface anisotropy; a reduction in the fractal dimension of the interface appears to result in a higher surface anisotropy.

Experimental evidence for electron channeling in Fe /Aau (100) superlattices.

We present transport and structural data from epitaxial (100) and (111) Au/Fe superlattices grown by molecular beam epitaxy. From their analysis, we conclude that an electron channeling mechanism, due to strong specular reflection of the minority spin carrier at the Au/Fe interfaces, is responsible for the high conductivity in the (100) superlattices.