Electroless deposition of Co(W) thin films

Thin films of cobalt that contain small amounts of tungsten [Co(W)] were deposited by the electroless process. Those films do not contain either phosphorus or boron which are included in most electroless cobalt films processes. The deposition bath for Co(W) thin films include Co ions, tungstate ions as a source for tungsten, di-methyl-amine-borane (DMAB) complex as a reducing agent, ammonium hydrate as a complexing agent, acetic acid for buffering and surfactants. Co(W) layers were deposited on two types of seed layers: (a) thin sputtered cobalt or copper films on 100 nm SiO₂/Si and (b) bare silicon wafers activated by an aqueous Pd/PdCl₂ solution. The deposited layer thickness range was 40–1000 nm with deposition rate at 90 °C and pH 9 of 7 nm/s for both Pd activated Si and sputtered Co seed, and 5 nm/s for the sputtered Cu seed. Lowering the temperature to 70 °C lowered the deposition rate to 0.7 nm/s for the Pd activated Si. The deposited layers were bright coloured, uniform, and with low defect density under visual inspection. The thin films composition was found to be Cobalt with 3–4 at.% tungsten for all types of seed layers. The Co(W) thin films specific resistivity was in the range of 60–90 μΩ cm. Finally we present the thin film morphology as it was characterized using atomic force microscopy and scanning electron microscopy.     

Enhancement of Cu nucleation in Cu-MOCVD by Pd sputtering pretreatment

Cu electroplating which emerges as a viable Cu filling technique for damascene processing relies on the presence of a smooth and continuous Cu seed layer. Metal organic chemical vapor deposition (MOCVD) may be the most promising technique to deposit the Cu seed layer. Plasma pretreatment is widely used as a precleaning technique which is essential for the enhancement of Cu nucleation in Cu-MOCVD. New pretreatment techniques which can replace plasma pretreatments are proposed in this paper. Pd sputtering, Pd–HF dipping or Pd-CVD pretreatment will possibly enhance Cu nucleation significantly if it is conducted on barrier metal films prior to Cu-MOCVD. It was found that Pd sputtering is more effective in enhancing Cu nucleation than direct plasma H₂ precleaning. Pd sputtering pretreatment is effective for a variety of barrier metals including Ta, TiN, TaN and TaSiN. The mechanism through which Cu nucleation is enhanced may be as follows: a thin Pd buffer layer formed by sputtering shields the barrier metal substrate surface with adsorbed oxygen atoms making Cu nucleation difficult and provides preferred sites for Cu nucleation.     

Grain nucleation and texture analysis of electroless copper deposition on a palladium seed layer

Electroless copper grains were deposited on a Pd seed layer under varying bath conditions. The seed layer was determined to have a (111) texture using grazing incident x-ray (GIX) diffraction. Multiple nucleation sites in the grain boundaries were imaged using a scanning tunneling microscope. Continual copper growth produced row-like structures. The texture of the electrolessly deposited copper (ED-Cu) grains were determined to be (111). No radial grain orientation for the Pd seed layer or the ED-Cu thin film was detected using GIX diffraction. Atomic force microscope images indicated continual Cu nucleation throughout the deposition process. PdH was formed as a by-product of the electroless deposition process, and detected by x-ray diffraction.     

The reliability of wire bonding using Ag and Al

The combination of aluminum (Al) and silver (Ag) for wire bonding is long established: aluminum (Al) heavy wire bonding on silver (Ag) metallization, such as pastes consisting of Ag as main component or comprising Ag alloys, was first established in the 1970s and was widely discussed (particularly in terms of reliability under high temperature and relative humidity) until the 1990s. Recently, discussion of the Ag/Al material system has reemerged in the literature, albeit within the context of a new bonding approach – thermosonic (TS) ball/wedge (B/W) bonding with Ag or Ag alloy wires, instead of gold (Au) or copper (Cu) wires, on Al-metallized chips. Several forms of Ag wire are currently being evaluated, including pure Ag, Ag alloys and a preliminary version of a palladium (Pd) -coated Ag. The present paper bridges the gap in the literature between the two bonding approaches by reviewing reliability studies for both Ag-on-Al and Al-on-Ag bonding.     

深亚微米集成电路工艺中铜金属互联技术

本文介绍了铜互联技术在深亚微米半导体工艺中的应用,重点介绍了铜金属互联技术中的关键工艺,包括在器件中采用铜金属互联线以降低互联延迟,大马士革（Damascene）结构微细加工工艺,物理汽相淀积（PVD）技术制备铜扩散阻挡层（Barrier）和铜子晶层（Cu-seed）,铜金属层化学电镀技术（Electroplating）,对铜金属互联工艺集成方面的要点也作了一些探讨。     

Evaluation of the corrosion performance of Cu–Al intermetallic compounds and the effect of Pd addition

Copper wire has become a mainstream bonding material in fine-pitch applications due to the rising cost of gold wire. In recent years, palladium-coated copper (Pd–Cu) wire is being increasingly used to overcome some constraints posed by pure Cu wire. During wire bonding with aluminum bond pads, different intermetallic compound (IMC) phases that have been identified at the bond interface are typically CuAl₂, CuAl and Cu₉Al₄. However, the corrosion susceptibility of these IMCs has not been investigated. This paper compares the electrical impedance and corrosion performance of the three types of Cu–Al IMCs in an acidic chloride medium by employing electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. The analysis of the potentiodynamic polarization results was performed using Tafel extrapolation. A comparison was made with pure Cu and Al. The effect of Pd alloy on the IMC corrosion performance has also been studied. Among the three Cu–Al IMCs, Cu₉Al₄ was observed to have the largest corrosion rate followed by CuAl₂ and CuAl. For the metals, Cu was observed to have the lowest corrosion rate and Al is the most easily corroded. The addition of Pd of up to 10 wt.% replacement of the Cu in the alloys slightly improves the corrosion resistance of the metals and IMCs.     

镉掺杂氧化亚铜薄膜的制备及其光电性能

采用一步水热法制备镉掺杂的Cu2O薄膜(Cd/Cu2O),分别探讨了制备过程中CuSO4浓度、NaOH浓度、反应时间、反应温度和CdSO4浓度对Cu2O和Cd/Cu2O薄膜光电性能的影响。结果表明,当反应釜中CuSO4浓度为0.114 2 mol/L、NaOH浓度为0.028 6 mol/L、反应时间为8 h、反应温度为90℃、CdSO4浓度分别为0 mol/L和0.571 4μmol/L时,可在基底Cu片上分别获得光电压为0.366 7 V的Cu2O样品和光电压为0.460 2 V的Cd/Cu2O薄膜样品。紫外可见吸收光谱(UV-Vis)、X射线衍射(XRD)图谱、扫描电子显微镜(SEM)和能谱仪(EDS)表征结果显示,Cu2O的禁带宽度为2.1 eV,而Cd/Cu2O的禁带宽度最小达到1.8 eV;Cd/Cu2O的择优生长面为(111)面,其衍射峰强度比Cu2O明显增强;Cd/Cu2O样品表面与Cu2O对比变得光滑,粒径由Cu2O的1.0~3.0μm减小到Cd/Cu2O的0.3~0.9μm。     

Influence of Deposition Parameters on the Morphology, Structural, and Optical Properties of ZnSe Nanocrystalline Thin Films

Zinc selenide (ZnSe) nanocrystalline thin films were prepared by using chemical bath deposition at different ammonia concentrations and different deposition temperatures. The structural and optical properties of ZnSe nanocrystalline thin films were investigated as a function of the ammonia concentration in precursors or the deposition temperature using scanning electron microscopy, energy-dispersive spectrometry, x-ray diffraction measurements, and ultraviolet (UV)–visible spectrophotometry measurements. The results reveal that the ZnSe thin films are composed of a large number of uniform spherical particles. Each spherical particle contains several nanocrystals 5 nm to 7 nm in crystallite size. An increase in both the average diameter of the spherical particles and the crystallite size of the nanocrystals occurs with an increase in ammonia concentration and/or deposition temperature. The Se/Zn atom ratios in the ZnSe thin films increase and the optical band gaps, E _g, of the ZnSe thin films decrease with an increase in ammonia concentration or deposition temperature. The kinetics and reaction mechanism of the ZnSe nanocrystalline thin films during deposition are discussed.     

The effect of introducing Al ions in cationic deposition bath on as-prepared PbS thin film through SILAR deposition method

Undoped and Al doped lead sulfide (PbS) thin films were grown on soda lime glass substrates by Successive Ionic Layer Adsorption and Reaction (SILAR) deposition method. Al content in aqueous cationic solution was varied by adding 0.5–2% of aluminum nitrate in step of 0.5. The characterization of the film was carried out using X-ray diffraction, scanning electron microscopy, and optical and electrical measurement techniques. X-ray diffraction analysis revealed that both the undoped and doped films were polycrystalline and exhibited galena type cubic structure with average crystallite size in the range of 15.5–30.9 nm. The compositional analysis results indicated that Pb, S and Al were present in the samples. Optical studies revealed prominent blue-shift in the absorption edge of as-deposited samples upon doping as compared to that of bulk PbS and this shift was due to a quantum confinement effect. The room temperature conductivity of the PbS thin films was in the range of 1.343×10⁻⁷–1.009×10⁻⁶ (Ω cm)⁻¹for doped samples and 5.172×10⁻⁸ for undoped PbS thin film sample. The optical band gap energy has inverse relation with grain size and electrical conductivity is closely related to structural parameters like grain size, crystallinity and microstrain. The estimated lattice parameter, grain size, optical band gaps and electrical properties were correlated with Al concentration in the cationic solution.     

Effects of Cu/Al intermetallic compound (IMC) on copper wire and aluminum pad bondability

Copper wire bonding is an alternative interconnection technology that serves as a viable, and cost saving alternative to gold wire bonding. Its excellent mechanical and electrical characteristics attract the high-speed, power management devices and fine-pitch applications. Copper wire bonding can be a potentially alternative interconnection technology along with flip chip interconnection. However, the growth of Cu/Al intermetallic compound (IMC) at the copper wire and aluminum interface can induce a mechanical failure and increase a potential contact resistance. In this study, the copper wire bonded chip samples were annealed at the temperature range from 150/spl deg/C to 300/spl deg/C for 2 to 250 h, respectively. The formation of Cu/Al IMC was observed and the activation energy of Cu/Al IMC growth was obtained from an Arrhenius plot (ln (growth rate) versus 1/T). The obtained activation energy was 26Kcal/mol and the behavior of IMC growth was very sensitive to the annealing temperature. To investigate the effects of IMC formation on the copper wire bondability on Al pad, ball shear tests were performed on annealed samples. For as-bonded samples, ball shear strength ranged from 240-260gf, and ball shear strength changed as a function of annealing times. For annealed samples, fracture mode changed from adhesive failure at Cu/Al interface to IMC layer or Cu wire itself. The IMC growth and the diffusion rate of aluminum and copper were closely related to failure mode changes. Micro-XRD was performed on fractured pads and balls to identify the phases of IMC and their effects on the ball bonding strength. From XRD results, it was confirmed that the major IMC was /spl gamma/-Cu/sub 9/Al/sub 4/ and it provided a strong bondability.     

脉冲激光沉积Al/Ag掺杂功能梯度薄膜

为了寻找制备梯度金属薄膜的新方法和新工艺,采用脉冲准分子激光扫描沉积技术,在Si(100)单晶衬底上沉积了Al/Ag掺杂功能梯度薄膜,并采用SEM和XPS对制备的薄膜进行了微观分析。分析结果表明,运用合适的激光参数和辅助放电,在沉积温度300℃时,制备出了Al/Ag组分比近似为5:1的掺杂梯度薄膜。该实验方法说明,利用脉冲激光与金属掺杂靶相互作用沉积梯度金属薄膜是可行的。     

Plastic deformation and interfacial sliding in Al and Cu thin film: Si substrate systems due to thermal cycling

As a result of the large difference in thermal expansion coefficients between metal and Si, high stresses can develop in thin metallic films attached to Si substrates in microelectronic devices during thermal excursions experienced in processing steps or during usage. These stresses may induce plastic deformation of the thin films accompanied by creep and interfacial sliding, and have a pronounced effect on the reliability of microelectronic devices and components. Even though various methods have been proposed to study thermal stress, methodologies for studying plastic deformation of thin films are not well established. Here, we report the results of a study of plastic deformation and interfacial sliding of thin Al and Cu films on Si substrates during thermal cycling. Cross-sectional profiles of pattern-grown Al and Cu films of nominally 250 nm thickness were measured before and after thermal cycling by employing an atomic force microscope. Through statistical analysis, the size changes of the thin films induced by thermal cycling were determined. Finite element (FE) analyses were conducted to compute the stress and strain states within the thin film and at the interface, and the results were utilized to interpret the atomic force microscopy (AFM) observations. Experiments revealed that, following thermal cycling, Al films expanded relative to the Si substrate, whereas Cu films shrank, resulting in an alteration of the film-footprint on the substrate in both cases. Based on the FE calculations, this was attributed to net inelastic deformation of the thin films via creep and yielding, with the deformation being accommodated at the interface by diffusion-controlled interfacial sliding.     

Atomic layer chemical vapour deposition of copper

Copper films with (1 1 1) texture are of crucial importance in integrated circuit interconnects. We have deposited strongly (1 1 1)-textured thin films of copper by atomic layer deposition (ALD) using [2,2,6,6-tetramethyl-3,5-heptadionato] Cu(II), Cu(thd)₂, as the precursor. The dependence of the microstructure of the films on ALD conditions, such as the number of ALD cycles and the deposition temperature was studied by X-ray diffraction, scanning electron microscopy (SEM), and transmission electron microscopy. Analysis of (1 1 1)-textured films shows the presence of twin planes in the copper grains throughout the films. SEM shows a labyrinthine structure of highly connected, large grains developing as film thickness increases. This leads to low resistivity and suggests high resistance to electromigration.     

Texture evolutions of ionized metal plasma Cu seed layers on tantalum nitride barriers

Ionized metal plasma (IMP) was a favorable method for the deposition of thin barrier and seed layers due to its sufficient bottom coverage in high aspect ratio features. In this study, the texture evolution of IMP copper (Cu) seed layers on IMP tantalum nitride barriers deposited by various nitrogen flow rates were investigated. The (111)/(200) ratio of the Cu seeds was found to relate to the grain size of the tantalum nitride substrates. A proposed model revealed that the surface energy reduction of the Cu deposition was a main factor to determine the (111)/(200) ratio of the Cu seeds.     

GaN/Al_2O_3(0001)的匹配机制及氮化的作用

在Ａｌ２Ｏ３（０００１）衬底上用ＭＯＣＶＤ（金属有机物气相沉积）方法进行了ＧａＮ的外延生长，通过Ｘ射线衍射（同步辐射源）研究了ＧａＮ和Ａｌ２Ｏ３（０００１）的匹配关系。结果表明，经充分氮化的衬底上，ＧａＮ以单一的匹配方式沿［０００１］方向生长；在Ａｌ２Ｏ３（０００１）衬底未经氮化或氮化不充分时，不同程度地出现了其它三种绕〈１１２０〉晶带轴倾斜一定角度的匹配位向。指出了ＧａＮ／Ａｌ２Ｏ３（０００１）的几种匹配方式的晶体学规律。ＧａＮ绕〈１１２０〉晶带轴倾斜的匹配方式是其外延生长过程中降低和Ａｌ２Ｏ３（０００１）的晶格失配、释放界面应变的重要机制之一。     

Impact of Al in Cu alloy interconnects on electro and stress migration reliabilities

The reliability of Cu interconnects was successfully improved by applying a CuAl alloy seed. However, the effect of additive Al on the reliability is not fully understood. In order to reveal the reliability improvement mechanism, Cu films using CuAl alloy seed were investigated in detail. As stress induced voiding (SIV) as well as electromigration is caused by migration of vacancies and/or Cu atoms, the measured activation energy value of electromigration using CuAl indicates that the fast diffusion paths are Cu grain boundaries. The analysis using high lateral resolution scanning type secondary ion mass spectrometry (nano-SIMS) clarifies that additive Al in ECP-Cu film is mainly localized at grain boundaries. Furthermore, positron annihilation was used to probe vacancy-type defects in Cu films. The CuAl films before recrystallization contain larger and higher density vacancy-type defects. Whereas, the recrystallized CuAl films after annealing above 250 °C contain smaller and lower density defects. Furthermore, CuAl films with annealing above 350 °C contain less Al inside the grains. These results represent that Al atoms in Cu films with annealing above 350 °C are exhausted from inside grains to the grain boundaries, and the spewed Al atoms existing at Cu grain boundary effectively prevents the diffusion of Cu and/or vacancies.     

异质诱导生长的酞菁铜薄膜晶体管的研究

因酞菁薄膜平面具有多电子共轭大π键结构,本文采用异质诱导的方式对酞菁薄膜的生长特性进行了改善研究。采用高掺杂硅为栅极,氧化硅为绝缘层,生长α-四噻吩或p-六联苯薄膜为异质诱导层,制备了酞菁铜有机薄膜晶体管。利用原子力显微镜研究薄膜生长特性,并对比研究了2种诱导层对薄膜晶体管性能的影响。实验结果表明:α-四噻吩上生长的酞菁铜薄膜,形貌呈片状,而p-六联苯上生长的酞菁铜薄膜,形貌呈针状,均与单层酞菁铜棒状形貌不同。同时,α-四噻吩与p-六联苯薄膜上生长酞菁铜后,两者晶体管电性能都有不同程度的提高,均比单层酞菁铜提高了1~2个数量级,表明α-四噻吩或p-六联苯对酞菁铜薄膜均有诱导效应,可以获得高性能的有机薄膜晶体管。     

Growth and Properties of Hybrid Organic‐Inorganic Metalcone Films Using Molecular Layer Deposition Techniques

Molecular layer deposition (MLD) is a useful technique for fabricating hybrid organic‐inorganic thin films. MLD allows for the growth of ultrathin and conformal films using sequential, self‐limiting reactions. This article focuses on the MLD of hybrid organic‐inorganic films grown using metal precursors and various organic alcohols that yield metal alkoxide films. This family of metal alkoxides can be described as “metalcones”. Many metalcones are possible, such as the “alucones” and “zincones” based on the reaction of trimethylaluminum and diethylzinc, respectively, with various organic diols such as ethylene glycol. Alloys of the various metalcones with their parent metal oxide atomic layer deposition (ALD) films can also be fabricated that have an organic‐inorganic composition that can be adjusted by controlling the relative number of ALD and MLD cycles. These metalcone alloys have tunable chemical, optical, mechanical, and electrical properties that may be useful for designing various functional films. The metalcone hybrid organic‐inorganic materials offer a new tool set for engineering thin film properties.     

有机胺碱对硅通孔铜膜化学机械抛光的影响

有机胺碱可与铜离子反应且产物在碱性条件下溶于水,这为硅通孔(TSV)铜膜的碱性化学机械抛光(CMP)提供了有利条件.研究了大分子有机胺碱对铜膜化学机械抛光的影响.首先测试了不同体积分数有机胺碱对碱性抛光液中磨料粒径和Zeta电位的影响,然后在直径3英寸(1英寸=2.54 cm)铜片上模拟了不同体积分数有机胺碱对铜去除速率的影响.实验结果表明:有机胺碱对抛光液中磨料粒径和Zeta电位没有影响;随着有机胺碱体积分数的增加,铜的去除速率先快速增加,达到一峰值后趋于稳定,最后略有下降;当有机胺碱的体积分数为5％时,TSV图形片铜膜去除速率达到最高值2.1tμm/min,剩余铜膜总厚度差减小到1.321 76 nm,实现了纳米级的化学机械抛光.     

Al2O3陶瓷表面的准分子激光活化沉积金属Cu技术

本文研究了通过ＸｅＣｌ准分子激光照射Ａｌ２Ｏ３陶瓷表面后,使其表面沉积金属Ｃｕ的技术,实验结果表明,Ａｌ２Ｏ３试样浸入Ｃｕ２ＳＯ４溶液后,金属Ｃｕ膜只沉积于激光照射区。经准分子激光照射,Ａｌ２Ｏ３表面结构的变化和Ａｌ富集区的产生是金属Ｃｕ沉积的主要原因。