Shadow Moire Interferometry Research Articles

Experimental and Theoretical Assessment of Thin Glass Substrate for Low Warpage

This paper compares the warpage after lead-free solder assembly of ultrathin glass and organic substrates for microelectronic packages. Smart mobile devices demand packages to be thinner, which exacerbates warpage, which in turn affects interconnect pitch scaling and reliability. Although low-coefficient-of-thermal-expansion (CTE) organic laminates have been developed to reduce the warpage during assembly, glass substrates offer added benefits of much higher modulus and thermo-mechanical stability, with the potential to reduce warpage beyond low-CTE organic materials. The focus of this paper is on modeling and measurements to quantify the warpage of glass and organic laminates at 100- $\mu \text{m}$ core thickness after thermo-compression bonding at 260 °C peak temperature. In the experiments, four-metal-layer glass substrates were fabricated at the panel level, diced into $18.4 \times 18.4$ -mm2 coupons, 10-mm $\times $ 10- $\text {mm}\,\,\times 630-\mu \text{m}$ silicon dies were thermo-compression bonded, and the warpage of the assembled packages was measured using shadow moire interferometry. In parallel to the experiments, numerical models that account for the viscoplastic behavior of the solder as well as the sequential build-up materials and processes have been developed. The predicted warpage from the models was compared to the experimental measurements. It was seen that the low-CTE glass had lower warpage than the organic core of equivalent CTE, while increasing the CTE of the glass increased the warpage. Also, the underfill fillet size was found to influence the warpage for thin substrate packages, and an optimal fillet size has been identified for minimizing warpage. B-staged and capillary underfill materials were compared and found to have similar warpage values.

Measurement determination of in-plane residual stresses in thin silicon oxide films of different thicknesses by shadow Moire interferometry : Ghaffari, K.; Wang, B.; Danyluk, S. ASNT 1994 Fall Conference and Quality Testing Show, Atlanta Georgia (United States), 19–23 Sep. 1994. pp. 77–78. ASNT (1994) ISBN 1-57117-002-2

Measurement determination of in-plane residual stresses in thin silicon oxide films of different thicknesses by shadow Moire interferometry : Ghaffari, K.; Wang, B.; Danyluk, S. ASNT 1994 Fall Conference and Quality Testing Show, Atlanta Georgia (United States), 19–23 Sep. 1994. pp. 77–78. ASNT (1994) ISBN 1-57117-002-2

The relationship between microstructure and residual stress in YBa 2Cu 3O 7− x

Sol-gel films of YBa 2Cu 3O x (YBCO) were deposited by spray pyrolysis on 10 cm diameter by 0.05 cm thick polycrystalline MgO wafers. The films were deposited in 1 microm increments up to 5 microm and characterized by electrical measurements, optical and electron microscopy, and X-ray diffraction. In plane residual stresses of the films were obtained by a shadow moire interferometry technique. The YBCOMgO interface was characterized by bevel polishing and fluorescence analysis. The films contain substantial in-plane residual stresses as a result of chemical reaction of the YBCO and MgO. Cu diffuses into the MgO so that a substantial amount of Y 2BaCuO 5 phase forms near the interface. The largest tensile stress was 0.96 GPa in a 4 microm thick film. The stresses were highest at the center of the wafer and decreased toward the edge, and the in-plane stresses caused cracks to form. Formation of the 211 phase influenced T c (onset) and T c (zero resistance). The T c onset was 78 to 92 K, and T c (zero resistance) was 15–65 K depending on film thickness.

Residual stress measurement in filament-evaporated aluminium films on single crystal silicon wafers

Shadow Moire interferometry was used to determine the residual stresses in thin, filament-evaporated aluminium films deposited on (100) p-type, 10.16 cm diameter, 0.05 cm thick, circular single crystal silicon wafers. The aluminium film thicknesses ranged from 70 to 780 nm. Benchmark experiments on wafers without aluminium films showed that wafers possess in-plane residual stresses; the centre of the wafer is under tensile stresses of the order of 30 M Pa and these stresses decrease toward the edge of the wafers to approximately 10 M Pa. The deposition of aluminium films increases these tensile residual stresses by 3 to 15 M Pa depending on the film thickness. The increase in the stress is attributed to the stresses in the films.

Residual stresses of thin, short rectangular plates

The analysis of the residual stresses in thin, short rectangular plates is presented. The analysis is used in conjunction with a shadow Moire interferometry technique by which residual stresses are obtained over a large spatial area from a strain measurement. The technique and analysis are applied to a residual stress measurement of polycrystalline silicon sheet grown by the edge-defined film growth technique.