Showing papers by "Zhong Chen published in 2004"

High-resolution NMR spectra in inhomogeneous fields via IDEAL (intermolecular dipolar-interaction enhanced all lines) method.

Abstract: Intermolecular double-quantum technique is used to yield high-resolution NMR spectra in inhomogeneous magnetic fields. The method exploits the distant dipolar interactions between the solvent and solute nuclear spins. Chemical shifts, J couplings, multiplicity patterns, and relative areas are retained with the method. Except for a 1.5-fold change in the scale factor of J couplings, other parameters are consistent with those extracted from one-dimensional spectra obtained in a homogeneous field.

Morphology and kinetic study of the interfacial reaction between the Sn-3.5Ag solder and electroless Ni-P metallization

Abstract: This work summarizes the interfacial reaction between lead-free solder Sn-3.5Ag and electrolessly plated Ni-P metallization in terms of morphology and growth kinetics of the intermetallic compounds (IMC). Comparison with pure Ni metallization is made in order to clarify the role of P in the solder reaction. During reflow, the IMCs formed with the Ni-P under-bump metallization (UBM) exist in chunky crystal blocks and small crystal agglomerates, while the ones with the sputtered Ni UBM exhibit uniformly scallop grains with faceted surfaces. The IMC thickness increases with reflow time following approximately a t1/3 power law for both systems. The IMC growth rate is higher with the Ni-P UBM than the Ni UBM. The thickness of the Ni3Sn4 layer increases linearly with the square root of thermal aging time, indicating that the growth of the IMCs is a diffusion-controlled process. The activation energy for Ni3Sn4 growth in solid-state reaction is found to be 110 kJ/mol and 91 kJ/mol for the Ni-P and sputtered Ni UBMs, respectively. Kirkendall voids are detected inside the Ni3P layer in the Sn-3.5Ag/Ni-P system. No such voids are found in the Sn-3.5Ag/Ni system.

Electroless copper deposition as a seed layer on TiSiN barrier

Abstract: Electroless deposition of copper as a seeding technology has received considerable attention in back-end-of-line device fabrication. This work explores the effects of plasma processing parameters such as argon gas flow rate and nitrogen plasma treatment time on the properties of electrolessly plated Cu on TiSiN barrier layers. The barrier film was produced by a low-frequency inductively coupled plasma process. The properties of deposited electroless copper are characterized by x-ray diffraction, four-point resistivity probe, atomic force microscopy, and field emission scanning electron microscope. The required palladium activation time is greatly reduced on TiSiN compared to TiN. In both cases there exists a preferred (111) crystal orientation in Cu film and the intensity ratio of I(111)/I(200) is very close. The Cu grain size is within the range of 23–34 nm for 84 nm thick film. It is found that argon gas flow rate does not have a significant effect on the resistivity of electroless copper film on TiSiN. However, increasing nitrogen plasma treatment time reduces the resistivity of copper film. The roughness of plated Cu layer largely follows the one of the underlying TiSiN. Good surface coverage of electroless Cu seed layer on TiSiN has been achieved in our experiment.