The long-term outcome of 1390 children with acute lymphoblastic leukemia (ALL), treated in two successive clinical trials (Taiwan Pediatric Oncology Group (TPOG)-ALL-97 and TPOG-ALL-2002) between 1997 and 2007, is reported. The event-free survival improved significantly (P ¼ 0.0004) over this period, 69.3±1.9% in 1997-2001 to 77.4±1.7% in 2002-2007. A randomized trial in TPOG-97 testing L-asparaginase versus epidoxorubicin in combination with vincristine and prednisolone for remission induction in standard-risk (SR; low-risk) patients yielded similar outcomes. Another randomized trial, in TPOG-2002, showed that for SR patients, two reinduction courses did not improve long-term outcome over one course. Decreasing use of prophylactic cranial irradiation in the period 1997-2008 was not associated with increased rates of CNS relapse, prompting complete omission of prophylactic cranial irradiation from TPOG protocols, beginning in 2009. Decreased use of etoposide and cranial irradiation likely contributed to the low incidence of second cancers. High-risk B-lineage ALL, T-cell, CD10 negativity, t(9;22), infant, and higher leukocyte count were consistently adverse factors, whereas hyperdiploidy 450 was a consistently favorable factor. Higher leukocyte count and t(9;22) retained prognostic significance in both TPOG-97 and TPOG-2002 by multivariate analysis. Although long-term outcome in TPOG clinical trials is comparable with results being reported worldwide, the persistent strength of certain prognostic variables and the lower frequencies of favorable outcome predictors, such as ETV6-RUNX1 and hyperdiploidy 450, in Taiwanese children warrant renewed effort to cure a higher proportion of patients while preserving their quality of life.

Ru-Ta and Ru thin films ͑ϳ15 nm in thickness͒ as diffusion barrier for Cu metallization on SiO 2 /Si and Si substrates are studied. Experimental results show that the Ru-Ta film exhibits amorphous structure until annealing at 700°C, whereas the Ru film crystallizes in as-deposited and annealed states. Sheet resistances of Cu/Ru and Cu/Ru-Ta stacking layers increase after annealing at 500 and 700°C, respectively, regardless of whether the substrate is SiO 2 /Si or Si. Increase in resistance is concurrent with the formation of Ru 2 Si 3 and Cu 3 Si when Cu/barrier stacks are deposited on Si substrate. Increase in resistance for Cu/barrier stacks deposited on SiO 2 /Si substrate is related to the diffusion of Cu through the crystallized barrier to the underlayers. Furthermore, current-voltage measurement also reveals that the Cu/Ru-Ta metallization has a lower leakage current than the Cu/Ru system. The failure mechanism and the effectiveness of Ta addition on barrier performance are discussed.Copper ͑Cu͒ interconnection has been widely used in ultralargescale integration devices because of its favorable electrical conductivity ͑1.67 ⍀ cm͒ and superior resistance to electromigration. 1 However, the major drawback of Cu interconnection is that Cu is a fast diffusion species in Si 2 as well as SiO 2 . 3 It is necessary to interpose a diffusion barrier between Cu and its underlayer to prevent devices from deteriorating interdiffusion and/or reaction. After the barrier deposition, a Cu-seed layer is deposited to ensure the bottom-up filling of electrochemical plating Cu for dual-damascene structure. However, the conventional copper liner ͑Cu-seed/Ta/TaN trilayer configuration͒ encounters scaling difficulty at the 45 or 32 nm node, where an ultrathin diffusion barrier ͑Ͻ5 nm͒ is needed to scale down the interconnection dimensions and maintain a low effective resistivity ͑ eff Ϸ 2.2 ⍀ cm͒. 4 Therefore, direct Cu electrodeposition on the diffusion barrier is extremely desirable to optimize the overall integration by consolidating the Cu-seed/Ta/TaN trilayer liner.Ruthenium ͑Ru͒ is a potential candidate for the Cu diffusion barrier and may also serve as a seed layer for Cu electroplating. Ru is an inert metal with a lower electrical resistivity ͑bulk = 7.6 ⍀ cm͒ than that of Ta ͑bulk = 13 ⍀ cm͒ or TaN film ͑ = 229 ⍀ cm͒ 5 and shows negligible solubility with Cu even after annealing at 900°C. 6 More importantly, it has been demonstrated that conformal Cu electroplating can be done directly on Ru. 7 Kim et al. 8 reported that the Ru film with preferred ͑001͒ crystal orientation enhances Cu wettability, because it has a low lattice misfit with the Cu͑111͒ plane. Josell et al. 9 demonstrated that superfilling of fine trenches by direct copper electrodeposition onto a ruthenium barrier could be achieved. However, pure Ru may not be a good diffusion barrier, because a 15 nm Ru film can prevent Cu diffusion in the Cu/Ru/Si system after annealing at 450°C for 10 min but fails after annealing at 550°C. 10 In order to improve the bar...

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ABSTRACT:In this work, fluorine-containing copolyimides were synthesized from 6FDA dianhydride and different ratios of BisAAF and PPD diamines. Properties, such as composition, viscosity, dielectric constant, glass-transition temperature, thermal decomposition temperature, tensile characteristics, and transmittance, were investigated by using elemental analysis, viscometry, Fourier transform infrared spectrometry, differential scanning calorimetry, a thermogravimetric analyzer, a tensile tester, and UV-visible spectrophotometry. After curing at 300°C for 1 h, imidization was observed, as indicated the appearance of an absorption peak of the carbonyl of the imide at 1780 cm Ϫ1 (CAO asymmetry stretching). The inherent viscosity increased with an increasing PPD mole fraction, from 0.40 dL/g of pure 6FDA-BisAAF to 0.84 dL/g of pure 6FDA-PPD. The dielectric constant decreased with increasing fluorine content. The glass-transition temperature increased with an increasing PPD mole fraction; the values increased from 317°C with pure 6FDA-BisAAF polyimide to 364°C with pure 6FDA-PPD polyimide. The 5% weight loss temperature (T d ) of the copolyimides was around 530°C in air and 540°C in a nitrogen atmosphere. The tensile modulus and tensile strength gradually increased with an increasing PPD molar fraction. The transmittance of 6FDA-BisAAF-PPD copolyimides was greater than 90% at wavelengths above 500 nm.

Sputtered Ru and Ru-C films 5 nm thick are employed in the Cu/barrier/SiO 2 /Si system, and their performances as the diffusion barrier as well as the seed layer for direct Cu electroplating are investigated in parallel. Based on the sheet resistance measurement and energy dispersive X-ray line profiles, the 5 nm Ru-C film can retard the diffusion of Cu after a prolonged ͑30 min͒ annealing up to 700°C, while the Ru film is an effective barrier up to only 400°C. Direct electroplating of Cu is successfully carried out on both Ru and Ru-C films, which proves that Ru-C is a Cu seed layer in addition to being a robust diffusion barrier. The microstructural characteristics of ultrathin Ru and Ru-C films are also examined, indicating that the superior barrier performance of the 5 nm Ru-C film is associated with its inferior crystallinity and resistance to agglomeration at elevated temperatures.