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

Abstract

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.

In-Operando X-ray diffraction imaging of thermal strains in fully packaged silicon devices

“…This was confirmed by a sequence of section topographs (see below) in which the wafer was scanned across a narrow slit. Unlike the heavily warped wafers of references [8], [9] and [10], there was only about 50m movement of the narrow diffracted image on the detector placed at a distance of 190mm. This indicated that the sample was flat to within about 5 arc seconds across its 1mm length throughout the powering procedure.…”

“…Such a method is used for the B16 beamline pco4000 CCD camera, manufactured by PCO AG of Kelheim, Germany, which has 4008 × 2672 pixels, 14bit dynamic range and where we chose the scintillator and optical magnification to give a 1m pixel size on the camera. Further details can be found in references [8,9] and [10]. All experiments were undertaken in standard multi-bunch mode with machine current of 300mA.…”

“…The thin die are subject to warpage when packaged and this has been found to be particularly problematic in multiple chips stacks with through-silicon via interconnection [5]. However, the reduction in package thickness has enabled non-destructive transmission X-ray Diffraction Imaging (XRDI) techniques [6,7] to be employed to map quantitatively the wafer distortions [8,9] and under stressed operating conditions [10].…”

X‐Ray Topography—More than Nice Pictures

“…The angular resolution for the misorientation in a crystal, the warpage of a wafer or any electronic device is about 0.003°± 0.001°. [69,72,73] The angular deviations can be interpreted on the other hand as strain and again by using Hook's law (Equation 3) the related stress can be calculated with maximum values in the order of magnitude of some tens of MPa.…”

“…As a last example the fast and nondestructive metrology for packaged electronic devices will be given. The so called B-spline X-Ray diffraction imaging (B-XRDI) is proposed also for in operando studies by the group of McNally [69,70,71,72] and transferred to laboratory sources by Tanner et al [73,74] The strength of X-ray topography in material research will be demonstrated in the following by example of mainly electronic materials, which can be easily transferred to other crystalline materials too.…”