Henri Chevrel

Plasma-enhanced atomic layer deposition of Co using Co（MeCp）2 precursor

Abstract Cobalt (Co) thermal or plasma enhanced atomic layer deposition (PE-ALD) was investigated using a novel metal organic precursor, Co(MeCp) 2 , and NH 3 or H 2 or their plasma as a reactant. The growth characteristics, electrical and microstructural properties were investigated. Especially, PE-ALD produced Co thin films at low growth temperature down to 100 °C. Interestingly, the low temperature growth of Co films showed the formation of columnar structure at substrate temperature below 300 °C. The growth characteristics and films properties of PE-ALD Co using bis(η-methylcyclopentadienyl) Co(II) (Co(MeCp) 2 ) was compared with those of PE-ALD Co using other Cp based metal organic precursors, bis-cyclopentadienyl cobalt (II) (CoCp 2 ) and cyclopentadienyl isopropyl acetamidinato-cobalt (Co(CpAMD)).

Influence of reflow atmosphere on SAC305 solder joints

Electronic assembly technology is in the transition from traditional tin-lead to lead-free. In comparison with Sn-Pb solders, high melting point and poor wettability of the lead-free solders lead to great challenge to present electronic assembly technologies. Inert nitrogen atmosphere can both widen the process window of reflow and improve the mechanical reliability of solder joints. The focus of this study is to investigate the effect of reflow atmosphere on the reflow process and solder joint reliability of lead-free solders (SAC305). Board level reflow in various kinds of atmospheres and microstructural characterization of the solder joint were carried out to demonstrate the influence of controllable atmosphere on the reflow quality of the lead-free solder joints. The SAC305 solder joint fabricated in 1000 ppm O2 exhibited a good surface morphology and an interface with very small pores. Surface finish of the solder pad was found to have a great influence on the as-reflowed solder joints.

Solar cell lifetime evaluation of using different Si-based precursor gases, SiH 4 and SiF 4

In amorphous silicon (a-Si), Si atoms are not all bonded to 4 other silicon atomes in an ordered manner. and this leads to the formation of defects such as Si dangling bonds.H2 used in the a-Si:H film deposition process passivate the dangling bonds by forming Si-H bonds, thus reducing the defect density. However H* in thin hydrogeneited a-Si films is very reactive especially under light exposure and can successfully break Si-Si bonds to create Si-H and a Si* dangling bond. In turn this defects can trap the electron-holes pairs leading to the degradation of cell efficiency. This is believed to be one of the main reasons for the so-called Staebler-Wronski (S-W) effect.[1–4] In our current study, we add SiF4 (Tetrafluorosilane) as an additive gas during the amorphous silicon film deposition process using SiH4. SiF4 is used as an additive to incorporate small controlled amounts of [F] in the amorphous film, which may stabilize the free dandling bond and may decrease the Staebler-Wronski effect. The effects on complete cell performance parameters, such as the cell efficiency, filling factor, Jsc, Voc and light-soaking degradation results are also included in this study.

OPTIMIZED WELDING OF STAINLESS STEEL TUBINGS FOR CORROSION FREE EXPOSURE TO HBR GAS

Hydrogen bromide gas phase corrosion of welded 316L electropolished stainless steel tubings to be used for the distribution of ultra clean gases has been investigated by using two techniques: one is leaching of the corroded tubings and subsequent chemical analysis of the dissolved metallic elements, the other one is bromine penetration depth at the stainless steel surface by Auger spectroscopy. These test procedures were applied to optimize the back shielding gas used for orbital welding of such tubings. A correlation is found between the oxygen concentration in the back shielding gas and the gas phase corrosion. Purified argon as back shielding gas insures best corrosion resistance due to the minimum thickness of superficial iron oxide, and maximal chromium concentration underlying the top iron/manganese oxide layer. Tubings made of stainless steel containing very small concentration of manganese exhibit lower level of corrosion. A corrosion enhancement mechanism by manganese is proposed.