铜布线工艺中阻挡层钽膜的研究

从钽膜质量的角度研究了用溅射方法在硅衬底上得到的 60 nm钽膜对铜硅互扩散的阻挡效果 ,钽膜的质量通过对硅衬底的表面处理以及钽膜的淀积速率来控制。研究发现 ,适当的硅衬底表面处理对钽膜是否能产生良好的防扩散能力起着关键的作用。本研究还得到了能有效阻挡铜硅接触的钽膜的淀积速率。     

金属与导电材料

Y2000-62562-182 0103555铜工艺(含5篇论文)=Cu process[会,英]//Proceed-ings of the IEEE 2000 International Interconnect Tech-nology Conference.—182～196(ZC)本部分有关铜工艺的5篇文章讨论了采用 DC 和脉冲反向工艺的电化学淀积 Cu 膜的间隙填充后的薄膜特性与表面剖面,化学汽相淀积铜薄膜淀积,室温电镀铜的显微结构,铜金属化用反应溅射 TaNx 层的扩散阻挡层的评价,以及先进铜互连应用的电镀后现场快速退火工艺。     

Cu金属化系统双扩散阻挡层的研究

采用二次离子质谱仪(SIMS)测试了SiON和Ta双层扩散阻挡层及Ta扩散阻挡层的阻挡性能;采用X射线衍射仪(XRD)测量了沉积态有Ta阻挡层和无阻挡层Cu膜的晶体学取向结构;利用电子薄膜应力测试仪测量了具有双层阻挡层Cu膜的应力分布状况。测试结果表明,双阻挡层中Ta黏附层有效地将Cu附着于Si基片上,并对Cu具有一定的阻挡效果,而SiON层则有效地阻止了Cu向SiO2中的扩散。与Ta阻挡层相比,双阻挡层具有较好阻挡性能。有Ta阻挡层的Cu膜的{111}织构明显强于无阻挡层的Cu膜。离子注氮后,薄膜样品应力平均值为206MPa;而电镀Cu膜后,样品应力平均值为-661.7MPa。     

超薄W-Si-N 作为铜与硅之间的扩散阻挡层

研究了W-Si-N三元化合物对铜的扩散阻挡特性.在Si(100)衬底上用离子束溅射方法淀积W-Si-N,Cu/W-Si-N薄膜,样品经过高纯氮气保护下的快速热退火,用俄歇电子能谱原子深度分布与X射线衍射以及电流-电压特性测试等方法研究了W-Si-N薄层的热稳定性与对铜的阻挡特性.实验分析表明W-Si-N三元化合物具有较佳的热稳定性,在800℃仍保持非晶态,当W-Si-N薄层的厚度仅为6nm时,仍能有效地阻挡铜扩散.     

超薄W-Si-N作为铜与硅之间的扩散阻挡层

研究了W- Si- N三元化合物对铜的扩散阻挡特性.在Si ( 10 0 )衬底上用离子束溅射方法淀积W- Si- N ,Cu/W- Si- N薄膜,样品经过高纯氮气保护下的快速热退火,用俄歇电子能谱原子深度分布与X射线衍射以及电流-电压特性测试等方法研究了W- Si- N薄层的热稳定性与对铜的阻挡特性.实验分析表明W- Si- N三元化合物具有较佳的热稳定性,在80 0℃仍保持非晶态,当W- Si- N薄层的厚度仅为6nm时,仍能有效地阻挡铜扩散     

超薄Ru/TaN双层薄膜作为无籽晶铜互连扩散阻挡层

研究了钌(Ru)/氮化钽(TaN)双层结构对铜的扩散阻挡特性,在Si(100)衬底上用离子束溅射的方法沉积了超薄Ru/TaN以及Cu/Ru/TaN薄膜,在高纯氮气保护下对样品进行快速热退火,用X射线衍射、四探针以及电流-时间测试等表征手段研究了Ru/TaN双层结构薄膜的热稳定性和对铜的扩散阻挡特性.同时还对Ru/TaN结构上的铜进行了直接电镀.实验结果表明Ru/TaN双层结构具有优良的热稳定性和扩散阻挡特性,在无籽晶铜互连工艺中有较好的应用前景.     

超薄Ru/TaN双层薄膜作为无籽晶铜互连扩散阻挡层

研究了钌(Ru)/氮化钽(TaN)双层结构对铜的扩散阻挡特性,在Si(100)衬底上用离子束溅射的方法沉积了超薄Ru/TaN以及Cu/Ru/TaN薄膜,在高纯氮气保护下对样品进行快速热退火,用X射线衍射、四探针以及电流-时间测试等表征手段研究了Ru/TaN双层结构薄膜的热稳定性和对铜的扩散阻挡特性.同时还对Ru/TaN结构上的铜进行了直接电镀.实验结果表明Ru/TaN双层结构具有优良的热稳定性和扩散阻挡特性,在无籽晶铜互连工艺中有较好的应用前景.     

Cu金属化系统双扩散阻挡层的研究

采用二次离子质谱仪（SIMSl测试了SiON和Ta双层扩散阻挡层及Ta扩散阻挡层的阻挡性能;采用X射线衍射仪（XRD）测量了沉积态有Ta阻挡层和无阻挡层Cu膜的晶体学取向结构;利用电子薄膜应力测试仪测量了具有双层阻挡层Cu膜的应力分布状况。测试结果表明,双阻挡层中Ta黏附层有效地将Cu附着于Si基片上,并对Cu具有一定的阻挡效果,而SiON层则有效地阻止了Cu向SiO2中的扩散。与Ta阻挡层相比,双阻挡层具有较好阻挡性能。有Ta阻挡层的Cu膜的（111）织构明显强于无阻挡层的Cu膜。离子注氮后,薄膜样品应力平均值为206MPa;而电镀Cu膜后,样品应力平均值为-661．7MPa。     

超薄Ru/TaN双层薄膜作为无籽晶铜互连扩散阻挡层

研究了钌（Ru) /氮化钽（TaN）双层结构对铜的扩散阻挡特性，在Si (100）衬底上用离子束溅射的方法沉积了超薄Ru/TaN以及Cu/Ru/TaN薄膜，在高纯氮气保护下对样品进行快速热退火，用X射线衍射、四探针以及电流-时间测试等表征手段研究了Ru/TaN双层结构薄膜的热稳定性和对铜的扩散阻挡特性. 同时还对Ru/TaN结构上的铜进行了直接电镀. 实验结果表明Ru/TaN双层结构具有优良的热稳定性和扩散阻挡特性,在无籽晶铜互连工艺中有较好的应用前景.     

一种低成本的硅垂直互连技术

采用KOH刻蚀工艺制作硅垂直互连用通孔,淀积SiO2作为硅垂直互连的电绝缘层,溅射Ti和Cu分别作为Cu互连线的黏附层/扩散阻挡层和电镀种子层.电镀10μm厚的Cu作为硅垂直互连的导电层.为实现金属布线的图形化,在已有垂直互连的硅片上试验了干膜光刻工艺.采用化学镀工艺,在Cu互连线上沉积150～200 nm厚的NiMoP薄膜作为防止Cu腐蚀和Cu向其上层介质扩散的覆盖层.高温退火验证了Ti阻挡层和NiMoP覆盖层的可靠性.     

Enhancing the reliability of n-p junction diodes using plasma treated tantalum barrier film

The properties of Ta barrier films treated with various plasma nitridations have been investigated by Cu/barrier/Si. An amorphous layer is formed on Ta barrier film after plasma treatments. The thickness of the amorphous layer is about 3 nm. Plasma treated Ta films possess better barrier performance than sputtered Ta and TaN films. It is attributed to the formation of a new amorphous layer on Ta surface after the plasma treatment. Cu/Ta(N,H)/Ta (10 nm)/Si remained stable after annealing at 750 °C. Ta(N,H)/Ta possesses the best thermal stability and excellent electrical properties. Cu/Ta/n⁺-p and Cu/Ta(N,O)/Ta/n⁺-p diodes resulted in large reverse-bias junction leakage current after annealing at 500 °C and 600 °C, respectively. On the other hand, Ta(N,H)/Ta and Ta(N)/Ta diffusion barriers improve the thermal stability of junction diodes to 650 °C. Ta(N,H)/Ta barrier film possesses lowest resistivity among Ta, Ta(N,O)/Ta, and Ta(N)/Ta films. Hydrogen plays an important role in enhancement of barrier properties. It is believed that hydrogen not only induces amorphization on Ta, but also eliminates the oxygen in the film. It is believed that the enhancement of ability against the copper diffusion is due to the combined effects of the hydrogen reaction and nitridation.     

Structure–Diffusion Relationship of Magnetron-Sputtered WTi Barriers Used in Indium Interconnections

Tungsten-titanium (WTi) thin films are known as potential adhesion promoters and diffusion barriers. The barrier efficiency of WTi thin films against indium (In) diffusion was experimentally studied by x-ray diffraction (XRD) measurements during in situ annealing. Specific multilayered samples were designed to estimate the diffusion barrier properties using the Ni/In system. These diffusion samples were made up of a 100-nm-thick WTi layer prepared by magnetron sputtering from an alloyed target (W:Ti ≈ 70:30 at.%), sandwiched between Ni and Au/In layers. WTi film microstructures were observed to depend on the working pressure. Diffusion barrier breakdown was monitored upon annealing by the formation of intermetallic compounds (IMC) (intermixing between Ni and In). Annealing was performed at temperatures of 573 K, 623 K, and 673 K (homologous temperatures $T/T_{\rm m}^{\rm In} \simeq 1.34, 1.45$ , and 1.57, respectively) and under primary vacuum. The diffusion coefficients of In in WTi were determined. The correlation between WTi film microstructure and diffusion barrier efficiency was established. Better diffusion barrier performance was obtained for WTi films with dense microstructure associated with a compressive residual stress state. Hence, tuning the sputtering conditions allows significant improvement of barrier performance against diffusion through a change of the film microstructure.     

Influence of low-k dry etch chemistries on the properties of copper and a Ta-based diffusion barrier

In this study, the film properties of Cu and a Ta-based diffusion barrier deposited on organic polymer and SSQ-based low-k materials with subtractive porosity were investigated. Emphasis was put on the effects of exposure of the low-k materials to the dry etch plasmas prior to metal deposition. The metal film properties were influenced by the type of the dry etch plasma chemistry used and by the porosity of the low-k material. Thermal desorption spectra (TDS) obtained during annealing of these metal films revealed an increased amount of species with m/e 44, attributed to CO₂, and H₂O desorbing from the Cu film at high temperatures. The TDS data for the Ta film did not contain such high temperature desorption peaks for these species mentioned. Surface morphology of the Cu and Ta films observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM) also showed a poor wetting of the metal films on the porous low-k materials that have been dry etch plasma treated.     

The performance of GaAs power MESFET’s using backside copper metallization

The performance of GaAs power MESFET’s using backside copper metallization has been evaluated. 10 nm Ta metal was used as the diffusion barrier between GaAs and Cu for copper film metallization in this study. Microstructural characterization shows that the Cu/Ta films with GaAs remained stable up to 400 °C, indicating that Ta is a good diffusion barrier for Cu in GaAs MESFET’s. A copper metallized 6 mm power MESFET was thermal stressed to test the device stability. After annealing at 200 °C for 3 h, the devices showed very little degradation in power performance, and the thermal resistance of the device was 65 °C mm/W with 1.4 W/mm DC input power. Results in this study demonstrate that the feasibility of using Cu/Ta films for the backside metallization of GaAs power devices with stable electrical and thermal characteristics.     

ULSI Cu互连CoSiN扩散阻挡薄膜的研究

CoSiN薄膜可以作为超大规模集成电路Cu布线互连材料使用。利用磁控溅射技术制备了CoSiN/Cu/CoSiN/SiO2/Si薄膜,利用四探针测试仪、薄膜测厚仪、原子力显微镜、X射线光电子能谱仪等来检测多层膜电阻率、薄膜厚度、表面形貌、元素含量及价态等。考察亚45 nm级工艺条件下CoSiN薄膜对Cu的扩散阻挡性能。实验结果表明,在氩气气氛条件下经500℃,30 min热退火处理后多层膜的电阻率和成分没有发生明显变化,CoSiN薄膜能够保持良好的铜扩散阻挡性能;经600℃,30 min热退火处理后,Cu大量出现在表面,CoSiN薄膜对Cu失去扩散阻挡性能。     

离子束溅射氧化钽薄膜光学特性的热处理效应

主要研究了离子束溅射制备的氧化钽薄膜在大气氛围下热处理对其光学特性的影响规律。实验中热处理温度范围的选择为150~550℃,间隔为200℃。研究中分别采用介电常数的Cody-Lorentz色散模型和振子模型对氧化钽薄膜的能带特性（1~4 eV）和红外波段（400~4 000 cm-1）的微结构振动特性进行了表征。研究结果表明,在150℃和350℃之间出现热处理温度转折点,即热处理温度高于此值时消光系数增加。Urbach能量的变化与消光系数趋势相同,而禁带宽度的变化与消光系数恰好相反。通过红外微结构振动特性分析,薄膜中仍存在亚氧化物的化学计量缺陷。     

Evaluation of DC-sputtered Glassy TaCoN Thin Film for Copper Metallization

The failure mechanism of the TaCoN barrier for copper metallization was examined using films by direct current (dc) magnetron reactive sputtering at various nitrogen flow rates. The as-deposited TaCoN films had a glassy structure and were free from intermetallic compounds. Optimizing the nitrogen flow rate during sputtering maximized the thermal stability of the Si/Ta_66.8Co_11.4N_21.8/Cu metallization system up to an annealing temperature of 750°C when the film was deposited using a nitrogen flow rate of 1 sccm, as revealed by using X-ray diffraction, a scanning electron microscope, a four-point probe and a transmission electron microscope. Structural analysis indicated that the failure mechanisms of the studied Si/TaCoN/Cu stacked films involved the initial dissociation of the barrier layer that was annealed at a specific temperature, and the subsequent formation of diffusion paths along which the copper penetrates through the TaCoN barrier layer to react with underlying Si. The high formation temperature of the Cu₃Si phase demonstrated that the studied film was highly stable, indicating that the TaCoN thin film is highly promising for use as a diffusion barrier for Cu metallization.     

TaCN growth with PDMAT and H2/Ar plasma by plasma enhanced atomic layer deposition

TaCN films were deposited using atomic layer deposition (ALD) using PDMAT and H₂/Ar plasma. Calculations based on density functional theory (DFT) indicate a high energy barrier and a low reaction energy for reducing the +5 Ta oxidation state in the PDMAT precursor by using pure H radicals. Through the assistance of Ar radicals, low resistivity of TaCN films of 230 μΩ cm could be deposited by using H₂/Ar plasma. By employing in situ X-ray diffraction during annealing, the activation energy for Cu diffusion through the TaCN barrier was evaluated at 1.6 eV.     

Electroless CoWP as a Diffusion Barrier between Electroless Copper and Silicon

In this work, an electroless CoWP film deposited on a silicon substrate as a diffusion barrier for electroless Cu and silicon has been studied. Four different Cu 120 nm/CoWP/Si stacked samples with 30, 60, 75, and 100 nm electroless CoWP films were prepared and annealed in a rapid thermal annealing (RTA) furnace at 300°C to 800°C for 5 min. The failure behavior of the electroless CoWP film in the Cu/CoWP/Si sample and the effect of CoWP film thickness on the diffusion barrier properties have been investigated by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and sheet resistance measurements. The composition of the electroless CoWP films was 89.4 at.% Co, 2.4 at.% W, and 8.2 at.% P, as determined by energy dispersive X-ray spectrometer (EDS). A 30 nm electroless CoWP film can prevent copper penetration up to 500°C, and a 75 nm electroless CoWP film can survive at least up to 600°C. Therefore, increasing the thickness of electroless CoWP films effectively increases the failure temperature of the Cu/CoWP/Si samples. The observations of SEM and TEM show that interdiffusion of the copper and cobalt causes the failure of the electroless CoWP diffusion barriers in Cu/CoWP/Si during thermal annealing.     

多靶磁控共溅射纳米Ta-Al-N薄膜的阻挡性能研究

采用磁控反应共溅射方法制备了纳米Ta-Al-N薄膜,并原位制备了Cu/Ta-Al-N薄膜,对薄膜进行了热处理。用四探针测试仪、X射线衍射仪(XRD)、扫描电镜(SEM)、原子力显微镜(AFM)以及台阶仪等研究了退火对薄膜结构及阻挡性能的影响。结果表明,Ta-Al-N薄膜具有优良的热稳定性,保持非晶态且能对Cu有效阻挡的温度可达800°C;同时发现在900°C退火5 min后,薄膜开始晶化,在Cu/Ta-Al-N/Si界面处生成了Cu3Si等相,表明此时Ta-Al-N薄膜阻挡层开始失效。