【作者】 黄敏；

【导师】 王红斌； 易勇； 何智兵； 刘艳松；

【作者基本信息】 西南科技大学 ， 材料科学与工程， 2022， 硕士

【摘要】 铜(Cu)、钽(Ta)薄膜是集成电路互联结构中应用广泛、稳定性和可靠性强的功能材料。Cu薄膜具有优异的延展性、热稳定性、抗电迁移性和电爆性能,在半导体、电爆、新能源、光电、装饰等方面具有广阔应用前景。稳定α-Ta薄膜具有较好的延展性和低电阻率,与铜无不良反应,是一种潜在的铜/硅或铜/二氧化硅互扩散阻挡层,并被广泛用于集成电路、枪管保护涂层、耐磨耐腐蚀、机械应用等。Cu、Ta薄膜结构、取向、形貌以及性能通过制备技术和工艺参数进行调控,这对于金属薄膜的应用发展有极其重要意义,这也成为我们研究的重点。本文采用直流磁控溅射(DCMS)和高功率脉冲磁控溅射(Hi PIMS)耦合的溅射技术,即DC/Hi PIMS共溅射技术,在单晶Si表面制备金属Cu、Ta及Cu-Ta薄膜。通过控制直流功率、基底偏压等参数开展有关金属Cu、Ta及Cu-Ta薄膜的结构、形貌和性能等研究。采用掠入射X射线衍射(GI-XRD)系统分析薄膜的结构和取向。使用场发射扫描电镜(FE-SEM)、白光干涉仪、原子力显微镜(AFM)等表征薄膜的表面、断面形貌和粗糙度,并检测Cu-Ta薄膜中铜层的断面元素。利用连续刚度模式下纳米压痕测试法表征Cu、Ta薄膜的力学性能。采用四探针法分别表征Cu、Ta薄膜的电阻率值。研究结果表明:(1)DC/Hi PIMS共溅射Cu薄膜的结构和性能受衬底负偏压(0?-100 V)的影响。随着负偏压增加,薄膜晶粒尺寸先减小后增加,硬度增加,择优取向强度和电阻率降低。高负偏压下,较高离子能量使铜薄膜择优取向改变,致密性和硬度较大,粗糙度和电阻率较低。与Hi PIMS薄膜相比,高负偏压下共溅射铜薄膜的硬度更高,电阻率更低。Hi PIMS参与和负偏压共同决定了溅射铜离子通量和能量,主导铜薄膜的结构和性能。(2)不同直流功率对Ta薄膜的结构和性能控制具有重要作用。DC/Hi PIMS共溅射过程中,Ta离子与中性粒子比与DCMS溅射功率相关。该共溅射技术避免不稳定电弧放电,并提高了沉积速率。与纯DCMS相比,共溅射可直接制备纯α-Ta薄膜,α-Ta薄膜粗糙度更低、致密性更好、硬度更高。因此,DC/Hi PIMS共溅射可一步法制备晶粒极其细小、致密、均匀的纯α-Ta薄膜,其表面光滑(3.22 nm),电阻率低(38.98μΩ·cm),硬度高(17.64 GPa)。(3)Cu-Ta薄膜的制备。100nm厚度的共溅射Ta薄膜为混合相结构(α+β),具有致密均匀且细小晶粒。在Ta薄膜表面制备1μm Cu薄膜并退火(200℃和600℃)发现,低温退火时(200℃)共溅射Ta薄膜表面的Cu薄膜具有结晶度高、晶粒细小、致密均匀和表面光滑等特点,且未有Ta、Si向铜中扩散。高温退火时(600℃),共溅射Ta薄膜发生相变,再结晶现象导致Cu薄膜表面颗粒尺寸较大且突兀,增加表面粗糙度。在SEM元素分析中,Cu层检测到Ta、Si元素,但XRD结果表明未发生Ta、Si向Cu层中扩散。综上,该结果为继续探索Ta薄膜在阻挡Cu、Si互扩散作用中做出重要建设性意义。据上述研究,通过DC/Hi PIMS共溅射方法在不同工艺参数下制备Cu、Ta薄膜可有效实现薄膜结构控制和性能改善。所制备的Cu、Ta薄膜均具有致密均匀结构、优异力学和电学性能。另外,共溅射Ta薄膜在低温下可有效阻止Cu/Si互扩散,有望满足在半导体超大规模集成电路中的需求。更多还原

【Abstract】 Copper(Cu)and tantalum(Ta)films are widely used functional materials with strong stability and reliability in the interconnection structure of integrated circuits.Cu has excellent characteristics: ductility,thermal stability,electromigration resistance,electrical explosion performance and low resistivity,which has superior application prospects in semiconductor,electrical explosion,new energy,photoelectric,decoration and so on.Ta film with excellent physical and chemical properties is used as a classy interdiffusion barrier between copper and silicon or silicon dioxide.Stable α-Ta at high temperature with good ductility and low resistivity has no adverse reaction with Cu,which is widely used in integrated circuit,gun barrel protective coating,wear resistance and corrosion resistance.The structure,orientation,morphology and properties of Cu and Ta fioms are regulated by preparation technology and process parameters.It is of great significance for the application and development of metal films and has also become the focus of our research.In the paper,DC magnetron sputtering(DCMS)and high power pulsed magnetron sputtering(Hi PIMS)were combined as DC / Hi PIMS co-sputtering to prepared Cu films,Ta films and Cu-Ta films on Si surface.Cu,Ta and Cu-Ta films with structures,morphologies and properties were explored by regulating DC power,substrate bias,and compared with pure DCMS and Hi PIMS.The structure and orientation all films were studied by grazing incidence X-ray diffraction(GI-XRD).Field emission scanning electron microscope(FE-SEM),white light interferometer and atomic force microscope(AFM)were used to characterize the morphology and roughness of all films,as well as the section elements of Cu layer in Cu-Ta films by EDS.The hardness of Cu and Ta films were revealed by nano indentation test in continuous stiffness mode.The resistivity of Cu film and Ta film were promulgated by four probe resistivity test.The results showed that:(1)The structure and properties of DC/Hi PIMS co-sputtered Cu films at different substrate negative bias voltages(0～-100 V)were tremendously effects.With the increase of negative bias voltage,the grain size first decreased and then increased,the hardness increased,the preferred orientation strength and resistivity decreased.Under high negative bias voltage,the preferred orientation was changed.And the films were with higher compactness and hardness,lower roughness and resistivity because of higher ion energy.Compared with Hi PIMS films,the co-sputtered copper films had higher hardness and lower resistivity under high negative bias.The flux and energy of sputtered copper ions were determined by Hi PIMS participation and negative bias jointly,and dominated the structure and properties of copper films.(2)Different DC power played an important role in controlling the structure and properties of Ta films.The results showed that the ratio of Ta ion to neutral particle in DC/Hi PIMS co-sputtering was closely related to DC power.The unstable arc discharge was averted and the deposition rate was improved in co-sputtering.The α-Ta films deposited by co-sputtering had lower roughness,better compactness and hardness than that of DCMS films.Therefore,the fine grains,smooth surface roughness(3.22nm)and low resistivity(38.98 μ Ω · cm),high hardness(17.64GPa)of pure α-Ta films produced by one-step method in DC/Hi PIMS co-sputtering were achieved.(3)Preparation of Cu-Ta films.Ta films with dense,uniform and fine grains deposited by DC/Hi PIMS co-sputtering were a mixed phase structure(α+β)at a thickness of 100 nm.Cu-Ta films were annealed at 200 ℃ and 600 ℃ after Cu films prepared on the Ta films surface.It was found that the high crystallinity,fine and dense grains,smooth surface of Cu films at low temperature(200 ℃)were found.And there was no Ta and Si diffusion in Cu layer.At high temperature(600 ℃),the phase transformation of co-sputtered Ta film occurred.The abrupt particles with large size on Cu layer in Cu-Ta films were formed for recrystallization,which leads the roughness increase and Ta and Si diffusion in Cu layer.Ta and Si elements in Cu layer were detected by EDS,while no similar phenomenons were found in XRD results.Thus,the results were of great constructive significance for continuing to explore Ta films as Cu/Si diffusion barrier.Above all,the structure control and performance improvement of Cu and Ta films can be effectively realized by DC/Hi PIMS co-sputtering.There were compact and uniform structure,and excellent mechanical and electrical properties for the Cu and Ta films in DC/Hi PIMS co-sputtering.In addition,Cu/Si interdiffusion can effectively prevented by the co-sputtered Ta films at low temperature,which is expected to meet the needs of very large scale integration(VLSI).更多还原