集成电路Cu金属化中的扩散阻挡层

阐述了集成电路Cu互连中的技术难题,重点讨论了Cu的扩散问题,综述了扩散阻挡层的研究发展进程,重点介绍了当今研究较多的难熔金属、难熔金属氮化物及其三元结构阻挡层的最新进展情况。研究表明,阻挡层的阻挡性能与制备工艺、薄膜组分及微观结构密切相关,其失效机制多为高温下阻挡层晶化所产生的晶界为Cu扩散提供了快速通道,掺入Si或其它原子的难熔金属氮化物由于其较高的晶化温度和良好的阻挡性能正成为研究热点。

氮气氛下LTCC基板Cu共烧金属化研究

从PMMA型LTCC素坯膜的制备和PMMA的排胶机理两方面,研究了LTCC基板Cu共烧金属化。结果表明,采用PMMA作为粘结剂的流延浆料具有剪切变稀行为,所得的流延坯膜微观组织均匀,叠压后坯体内部无分层现象。热失重、差热和傅立叶红外光谱联用分析结果表明高纯N_2气氛中PMMA以解聚机理热解,热解后释放的主要产物为丙烯酸甲酯。在高纯N_2气氛中LTCC与Cu共烧后Cu金属化膜平整、致密,连通良好。经测试,基板表面Cu导体方阻小于5mΩ/□。

Characteristic atom occupation patterns of Au_3Cu,AuCu_3,AuCuI and AuCuII based on experimental data of disordered alloys

The potential energies, volumes and electronic structures of characteristic atoms coordinated by neighboring configurations were obtained from the experimental heats of formation and lattice parameters of disordered Au1-xCux alloys. From characteristic atom occupation （CAO） patterns of L12-Au3Cu, L12-AuCu3 and Llo-AuCu compounds, their electronic structures, volumetric and energetic properties were calculated. The CAO pattern of Johasson-Linde（J-L） model shows that the transition AuCuI→AuCulI is an exothermic and volume contraction reaction, which is opposite from experimental phenomena. According to CAO pattern of Guymont-Feutelais-Legendre（G-F-L） model, the AuCulI cell consists of two periodic antidirection （PAD） AuCuI regions and two PAD boundary regions. The equations derived from CAO pattern of G-F-L model can be used to calculate energetic properties, volumetric properties and ordering degrees of the PAD AuCuI region and PAD boundary region, as well as corresponding average properties of the AuCulI phase. The results are consistent with experimental phenomena.

Effect of uniform magnetic field on crystallization of intermetallic compound layers between Cu and liquid SnZn alloys

Crystallization of intermetallic compound layer between Cu and SnZn alloy under uniform magnetic field was studied. The effect of magnetic field density on the growth behavior of the intermetallic layer such as microstructure, crystal orientation and composition was analyzed by scanning electron microscopy, X-ray diffraction and electron-probe microanalysis, respectively. Compared with the intermetallic layer without magnetic field, 0.1 T of magnetic flux density decreases the layer thickness. However, further increasing magnetic flux density promotes the layer growth. Application of magnetic field also changes the crystal orientation of intermetallic layer, but has no obvious influence on the layer composition. This phenomenon can be attributed to the role of thermo-electromagnetic convection and Lorentz force on the Cu dissolution as well as the accumulation of Cu solute at the interface front.

Corrosion and electrochemical behaviors of 7A09 Al-Zn-Mg-Cu alloy in chloride aqueous solution

The corrosion and electrochemical behaviors of 7A09 Al？Zn？Mg？Cu alloy were investigated in 3.5% NaCl （mass fraction） solution using complementary techniques such as scanning electron microscopy （SEM）, metallographic microscopy and electrochemical measurements. The results show that both pitting corrosion from or around the intermetallic particles and intergranular corrosion are observed after the immersion test due to the inhomogeneous nature of the microstructure of the 7A09 alloy. The preferential dissolution of the anodic Cu-depleted zone along grain boundaries is believed to be the possible cause of intergranular corrosion. The passivation and depassivation of this alloy show significant dependence of immersion time, owing to the formation and dissolution of various passive films on the sample surfaces. Furthermore, the corrosion process and corrosion mechanism were also analyzed.

Microstructure and properties of Al/Cu bimetal in liquid-solid compound casting process

A Ni-P coating was deposited on Cu substrate by electroless plating and the Al/Cu bimetal was produced by solid？liquid compound casting technology. The microstructure, mechanical properties and conductivity of Al/Cu joints with different process parameters （bonding temperature and preheating time） were investigated. The results showed that intermetallics formed at the interface and the thickness and variety increased with the increase of bonding temperature and preheating time. The Ni？P interlayer functioned as a diffusion barrier and protective film which effectively reduced the formation of intermetallics. The shear strength and conductivity of Al/Cu bimetal were reduced by increasing the thickness of intermetallics. In particular, the detrimental effect of Al2Cu phase was more obvious compared with the others. The sample preheated at 780 ℃ for 150 s exhibited the maximum shear strength and conductivity of 49.8 MPa and 5.29×10^5 S/cm, respectively.

Microstructural characterization and mechanical properties of aluminum 6061-T6 plates welded with copper insert plate(Al/Cu/Al) using friction stir welding

Friction stir welding was used to join two aluminum 6061-T6 plates with an insert of a pure copper plate(Al/Cu/Al),and then the influence of the copper insert on the joint performance was studied.The dissimilar welding results were also compared with AA 6061 friction stir welds produced without copper insert(Al/Al).Optical and scanning electron microscopes were used for the microstructural observations of the welded samples.X-ray diffraction analysis was used to analyze phase component of the Al/Cu/Al specimen.A defect-free joint was observed for the Al/Cu/Al joint at a rotational speed of 950 r/min and a welding speed of 50 mm/min.Microstructural observation of the weld nugget zone(WNZ)demonstrates the formation of composite-like structure which promotes metallurgical bonding of aluminum and copper.XRD results show the formation of intermetallic compounds(IMCs),such as Al4Cu9 and Al2Cu.Furthermore,it was observed that the hardness of the weld with the Cu insert plate is higher than that of other samples due to more dislocation density and a distinct rise in hardness values was observed due to the presence of IMCs.The ultimate tensile strength of the joint with copper insert plate is higher than that of the other sample due to the strong metallurgical bonding between Al and Cu.

Structure and denitration performance of carbon-based catalysts prepared from Cu-BTC precursor

Using Cu-BTC prepared by hydrothermal method as precursor, carbon-based catalysts were obtained as model materials for low-temperature DeNO_x. These catalysts were characterized by X-ray diffractometry（XRD）, Raman spectroscopy, scanning electron microscopy（SEM） and energy dispersive X-ray spectrometry（EDS）. The results showed that all carbon-based catalysts held the octahedron shape of Cu-BTC in most parts, and they mainly consisted of face-centered cubic copper. CuO_x/C exhibited excellent catalytic activity, and such catalytic activity was further improved with the introduction of Ag. The catalyst with a Cu to Ag mole ratio of 6：1 and an activated temperature of 600 °C showed the best catalytic performance, and its catalytic denitration rate reached 100% at a temperature as low as 235 °C. During the catalytic reaction process, Cu~＋ mainly played a catalytic role.

Effect of intermetallic compound thickness on anisotropy of Al/Cu honeycomb rods fabricated by hydrostatic extrusion process

The effect of intermetallic compound （IMC） thickness on the thermal and mechanical properties of Al/Cu honeycomb rods was investigated. The Al/Cu honeycomb rods were fabricated using repeated hydrostatic extrusions at 200 ℃. During the process, an IMC layer with 1μm in thickness was generated at the Al/Cu interface. Different IMC thicknesses were obtained by post-heat treatment at 420 ℃ for 0.5 to 2 h. The IMC thickness increased to 10.1μm. The IMC layers were identified as Al2Cu （θ）, AlCu （η2）, and Al4Cu9（γ1） phases. The thermal conductivities in the longitudinal direction and cross direction decreased by 11.9% （（268±4.8） to （236±4.4） W/（m·K）） and 10.4% （（210±3.2） to （188±2.8） W/（m＆#183;K））, respectively, with increasing IMC thickness. The ultimate tensile strength and elongation of the Al/Cu honeycomb rod are （103±8.4） MPa and （73±6.2）%, respectively. The ultimate tensile strength increased to （131±6.5） MPa until the IMC thickness reached 7.7μm. It subsequently decreased to （124±3.9） MPa until the IMC thickness reached 10.1μm. The elongation of the Al/Cu honeycomb rod then sharply decreased to （29±2.5）% with increasing IMC thickness.

Preparation of bimetallic nano-composite by dissimilar friction stir welding of copper to aluminum alloy

Butt friction stir welding between pure copper and AA5754 alloy was carried out.Reinforcing SiC nanoparticles were utilized in friction stir welded(FSW)joints to decline the harmful effects of intermetallic compounds.Tensile tests,micro-hardness experiments,scanning electron microscopy and X-ray diffraction analysis were applied to studying the properties of welded joints.The joints with a travel speed of 50 mm/min and a rotation speed of 1000 r/min showed the best results.The presence of nano-sized SiC particles reduced the grain size of aluminum and copper in the stir zone(SZ)from 38.3 and 12.4μm to 12.9 and 5.1μm,respectively.The tensile strength of the joint in the presence of reinforcing SiC nano-particles was~240 MPa,which is~90%of that for the aluminum base.Furthermore,the highest microhardness of the weld zone was significantly increased from HV 160 to HV 320 upon the addition of SiC nano-particles.The results also showed that raising the heat generation in FSW joints increased the amount of Al_(4)Cu_(9) and Al_(2)Cu intermetallic compounds.

Intermetallic phase formation and evolution during homogenization and solution in Al-Zn-Mg-Cu alloys

The effects of major alloy element contents of Zn, Mg, Cu in Al-Zn-Mg-Cu alloys on the formation and evolution of intermetallic phases during casting, homogenization and solution treatment have been investigated through using X-ray diffraction, scanning electron microscopy and differential scanning calorimetry. Experimental results showed that a relatively higher Zn content with lower Mg and Cu contents was beneficial to the formation of MgZn2 phase instead of the A12CuMg phase, which resulted in the unicity of the intermetallics in the A1 matrix, and that the MgZn2 phase was easier for diffusion and dissolution during homogenization and solution than the Al2CuMg phase. Additionally, the results of the first-principles calculations gave support for explaining the experimental phenomena. A larger absolute value of formation enthalpy and a smaller value of binding energy of the MgZn2 phase, as compared with the Al2CuMg phase, give it priority to precipitate during casting and make it easier to re-dissolve during homogenization and solution treatment. What＇s more, higher elastic constants with severe anisotropy of Young＇s modulus make undissolved blocks of AI^CuMg phase act as crack initiation, which degrade the perfor- mance of the materials.

Effects of the laser surface treatment on the mechanical properties of CuZr-based bulk metallic glasses

Surfaces of three types of CuZr-based bulk metallic glasses （BMGs） were modified by laser surface treatment （LST）, and the influence of the treatment on structure and mechanical properties of these alloys was investigated. The phase structure of as-cast and laser-treated samples was characterized by XRD and the morphology of the alloys after fracture was examined by SEM. The compressive plasticity of treated Cu47.sZr47.sAI5 and Cu46.sZr47.sAlsCo~ BMGs can be improved from 0.5% to 2.0% and from 1.2% to 5.7% respectively compared with the as-cast ones, while （Cu0.55Zr0.40Ala05）99Er~ BMG shows insignificant change of plasticity. The improvement in plasticity is attributed to induced crystallization of B2 CuZr phase in the treated sur- face zone of selected metallic glasses.