SiO2/Ta界面反应及其对铜扩散的影响

利用磁控溅射方法在表面有SiO2层的Si基片上溅射Ta/NiFe薄膜,采用X射线光电子能谱(XPS)研究了SiO2/Ta界面以及Ta5Si3标准样品,并进行计算机谱图拟合分析.实验结果表明在制备态下在SiO2/Ta界面处发生了热力学上有利的化学反应:37Ta+15SiO2=5Ta5Si3+6Ta2O5,界面处形成更稳定的化合物新相Ta5Si3、Ta2O5.在采用Ta作阻挡层的ULSI铜互连结构中这些反应产物可能有利于对Cu扩散的阻挡.     

SiO2/Ta界面反应及其对铜扩散的影响

利用磁控溅射方法在表面有SiO2层的Si基片上溅射Ta/NiFe薄膜,采用X射线光电子能谱(XPS)研究了SiO2/Ta界面以及Ta5Si3标准样品,并进行计算机谱图拟合分析.实验结果表明在制备态下在SiO2/Ta界面处发生了热力学上有利的化学反应:37Ta+15SiO2=5Ta5Si3+6Ta2O5,界面处形成更稳定的化合物新相Ta5Si3、Ta2O5.在采用Ta作阻挡层的ULSI铜互连结构中这些反应产物可能有利于对Cu扩散的阻挡.     

Cu/Zr-Si-N/Si金属化系统制备及退火气氛对其热稳定性的影响

采用磁控溅射法在n型〈111〉晶向的Si衬底上形成了Zr-Si-N薄膜及Cu/Zr-Si-N/Si金属化系统.将Cu/Zr-Si-N/Si金属化系统样品分别在真空及H2/N2(体积比为1∶9)气氛中800℃退火1h.对Zr-Si-N 薄膜和退火后的金属化系统样品进行X射线衍射、X射线光电子能谱、扫描电镜、薄层电阻率及俄歇电子能谱测试与分析.结果表明,Zr-Si-N阻挡层是以ZrN晶体与非晶相Si3N4或其他Si-N化合物的复合结构形式存在.经过两种气氛退火后的样品均没有发生阻挡层失效,但与真空退火相比,H2/N2退火气氛由于不存在残余O2的作用而表现出较低的Cu膜薄层电阻率及较好的Cu/Zr-Si-N/Si界面状态.     

Cu/Zr-Si-N/Si金属化系统制备及退火气氛对其热稳定性的影响

采用磁控溅射法在n型〈111〉晶向的Si衬底上形成了Zr-Si-N薄膜及Cu/Zr-Si-N/Si金属化系统.将Cu/Zr-Si-N/Si金属化系统样品分别在真空及H2/N2(体积比为1∶9)气氛中800℃退火1h.对Zr-Si-N薄膜和退火后的金属化系统样品进行X射线衍射、X射线光电子能谱、扫描电镜、薄层电阻率及俄歇电子能谱测试与分析.结果表明,Zr-Si-N阻挡层是以ZrN晶体与非晶相Si3N4或其他Si-N化合物的复合结构形式存在.经过两种气氛退火后的样品均没有发生阻挡层失效,但与真空退火相比,H2/N2退火气氛由于不存在残余O2的作用而表现出较低的Cu膜薄层电阻率及较好的Cu/Zr-Si-N/Si界面状态.     

磁控溅射的TaN薄膜的扩散阻挡性能

用反应磁控溅射方法在SiO2/Si(100)衬底和Cu薄膜间溅射一层TaN阻挡层,测试不同N气分压及热处理温度下Cu/TaN/SiO2/Si薄膜的显微结构和电阻特性.同时利用微细加工技术加工了镂空的Cu互连叉指测试结构,研究了TaN薄膜在镂空的铜互连结构中的扩散阻挡性能.结果发现,在退火温度不超过400 ℃时,薄膜电阻率均低于80μΩ·cm,而当溅射N分压超过10%,退火温度超过400℃时,薄膜电阻率很快上升.低N气分压下(≤10%)溅射时,即使退火温度达到600 ℃,薄膜电阻基本不变.     

氧化钒薄膜的制备及电致开关特性的研究

采用反应溅射法,室温下,在Cu/Ti/SiO2/Si衬底上制备了氧化钒(VOx)薄膜,并对薄膜进行450℃、30min的真空退火处理.采用X-射线衍射(XRD)、原子力显微镜(AFM)对薄膜的结晶取向和表面形貌进行了表征,通过半导体参数分析仪对薄膜的电开关特性进行测试,并利用导电原子力显微镜(CAFM)对VOx薄膜的导...     

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.     

Si间隔层对Al(1wt.%Si)/Zr极紫外多层膜热稳定的作用研究

为了提升Al/Zr多层膜的热稳定性,采用直流磁控溅射方法制备了18个带有不同厚度Si间隔层的Al(1 wt.%Si)/Zr多层膜,并将这些样品分别进行了不同温度(100~500 ℃)的真空退火,退火时间为1 h.利用X射线掠入射反射(GIXR)和X射线衍射(XRD)的方法来研究Si间隔层对Al/Zr多层膜热稳定性的作用.GIXR测量结果表明:随着Si间隔层厚度的增大,Al膜层的粗糙度减小,而Zr膜层的粗糙度增大;XRD测量结果表明:Al和Zr膜层粗糙度的变化是由于退火后膜层中晶粒尺寸不同造成的.相比于没有Si间隔层的Al/Zr多层膜,引入厚度为0.6 nm的Si间隔层可以有效提升Al/Zr多层膜的热稳定性.     

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。     

Effects of Substrate Materials on Self-Formation of Ti-Rich Interface Layers in Cu(Ti) Alloy Films

In our previous studies, thin Ti-rich layers were found to uniformly cover SiO₂/Si substrate surfaces at the interface with Cu(Ti) alloy films after annealing at elevated temperature. These Ti-rich layers were also found to prevent intermixing between the Cu(Ti) alloy films and the substrate, resulting in a simple barrier formation technique, called “self-formation of the diffusion barrier,” which is attractive for fabrication of ultra-large scale integrated (ULSI) interconnect structures. In the present study, to understand the mechanism of self-formation of the Ti-rich barrier layers on the substrate surface, the effects of SiO₂/Si, SiN/SiO₂/Si and NaCl substrate materials on the interfacial microstructure were investigated. The microstructures were analyzed by transmission electron microscopy (TEM) and secondary ion mass spectrometry (SIMS), and correlated with the electrical properties of the Cu(Ti) interconnects. It was concluded that the chemical reaction of Ti with the substrate materials was essential for the self-formation of the Ti-rich layers.     

Formation of Ti diffusion barrier layers in Thin Cu(Ti) alloy films

In order to study a formation mechanism of thin Ti-rich layers formed on the surfaces of Cu(Ti) wires after annealing at elevated temperatures, the 300-nm-thick Cu(Ti) alloy films with Ti concentration of 1.3 at.% or 2.9 at.% were prepared on the SiO₂/Si substrates by a co-sputter deposition technique. The electrical resistivity and microstructural analysis of these alloy films were carried out before and after annealing at 400°C. The Ti-rich layers with thickness of ∼15 nm were observed to form uniformly both at the film surface and the substrate interfaces in the Cu(2.9at.%Ti) films after annealing (which we call the self-formation of the layers) using Rutherford backscattering spectrometry (RBS) and transmission electron microscopy (TEM). Both the resistivities and the microstructures of these Cu(Ti) films were found to depend strongly on the Ti concentrations. The resistivities of the films decreased upon annealing due to segregation of the supersaturated Ti solutes in the alloy films to both the top and bottom of the films. These Ti layers had excellent thermal stability and would be applicable to the self-formed diffusion barrier in Cu interconnects of highly integrated devices. The selection rules of the alloy elements for the barrier self-formation were proposed based on the present results.     

Characterization of Self-Formed Ti-Rich Interface Layers in Cu(Ti)/Low-k Samples

In our previous studies, thin Ti-rich diffusion barrier layers were found to be formed at the interface between Cu(Ti) films and SiO₂/Si substrates after annealing at elevated temperatures. This technique was called self-formation of the diffusion barrier, and is attractive for fabrication of ultralarge-scale integrated (ULSI) interconnects. In the present study, we investigated the applicability of this technique to Cu(Ti) alloy films which were deposited on low dielectric constant (low-k) materials (SiO _x C _y ), SiCO, and SiCN dielectric layers, which are potential dielectric layers for future ULSI Si devices. The microstructures were analyzed by transmission electron microscopy (TEM) and secondary-ion mass spectrometry (SIMS), and correlated with the electrical properties of the Cu(Ti) films. It was concluded that the Ti-rich interface layers were formed in all the Cu(Ti)/dielectric-layer samples. The primary factor to control the composition of the self-formed Ti-rich interface layers was the C concentration in the dielectric layers rather than the enthalpy of formation of the Ti compounds (TiC, TiSi, and TiN). Crystalline TiC was formed on the dielectric layers with a C concentration higher than 17 at.%.     

Rutherford Backscattering Spectrometry Analysis of Self-Formed Ti-Rich Interface Layer Growth in Cu(Ti)/Low-<Emphasis Type="Italic">k</Emphasis> Samples

A new fabrication technique to prepare ultrathin barrier layers for nanoscale Cu wires was proposed in our previous studies. Ti-rich layers formed at Cu(Ti)/dielectric layer interfaces consisted of crystalline TiC or TiSi and amorphous Ti oxides. The primary control factor for the Ti-rich interface layer composition was C concentration in the dielectric layers rather than the formation enthalpy of the Ti compounds. To investigate Ti-rich interface layer growth in Cu(Ti)/dielectric layer samples annealed in ultrahigh vacuum, Rutherford backscattering spectrometry (RBS) was employed in the present study. Ti peaks were obtained only at the interfaces for all samples. Molar amounts of Ti atoms segregated to the interfaces (n) were estimated from Ti peak areas. Log n values were proportional to log t values. Slopes were similar for all samples, suggesting similar growth mechanisms. The activation energy (E) for Ti atoms reacting with the dielectric layers containing carbon (except SiO₂) tended to decrease with decreasing C concentration (decreasing k), while those for the SiO₂ layers were much higher. Reaction rate coefficients [Z · exp(−E/RT)] were insensitive to C concentration in the dielectric layers. These factors lead to the conclusion that growth of the Ti-rich interface layers is controlled by chemical reactions, represented by the Z and E values, of the Ti atoms with the dielectric layers, although there are a few diffusion processes possible.     

The effects of boron in the Cu(B)/Ti/SiO<Subscript>2</Subscript> system on the Cu-Ti reaction,resistivity, and diffusion barrier properties

The behavior of boron in Cu(4.8at.%B)/Ti/SiO₂ was investigated as a function of temperature, and its influences on the Cu-Ti interaction, resistivity, and diffusion barrier properties were also studied. The results showed the formation of a titanium boride layer at the Cu-Ti interface, after heating the Cu(B)/Ti/SiO₂ at 400°C and higher, effectively served as a barrier for the Cu and Ti diffusion, and significantly enhanced the Cu (111) texture. The resistivity dropped from 16.3 to 2.33 μΩ-cm after heating at 600°C, and continued to decrease up to 800°C. As a result, the Cu, in the form of B(O)_x/Cu/TiB₂/Ti(O)_x/SiO₂ multilayers, obtained by heating the Cu(B)/Ti/SiO₂, showed high thermal stability with low resistivity and, thus, can be used as interconnections in advanced integrated circuits. Since the Cu, in the form of B(O)_x/Cu/TiB₂/Ti(O)_x/SiO₂ multilayers, obtained by heating the Cu(B)/Ti/SiO₂, showed high thermal stability with low resistivity, it can be used as interconnections in advanced integrated circuits.     

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。     

Sputtered Ru-Ti, Ru-N and Ru-Ti-N films as Cu diffusion barrier

Ultrathin Ru-Ti alloy, Ru-N and Ru-Ti-N films were fabricated as diffusion barriers to Cu metallization. The thermal stability, phase formation, surface morphology and atomic depth profile of the Cu/Ru-Ti(10 nm)/Si, Cu/Ru-N(10 nm)/Si and Cu/Ru-Ti-N(10 nm)/Si structures after annealing at different temperatures were investigated. Comparing to the single Ru layer, both N doping and Ti alloying improve the thermal stability and diffusion barrier properties to Cu. The Cu on the Ru-Ti layer has better morphology than Cu on the Ru-N layer, while the Ru-Ti-N layer has the best thermal stability and has great potential to be applied as a single layer diffusion barrier.     

TEM investigation of Ti and Ti/Al bilayer as alternative diffusion barriers for Cu metallization for SAW device applications

The thermal stability of Ti and Ti/Al thin barrier layers for Cu metallizations of surface acoustic wave (SAW) devices has been investigated by resistance measurements and analytical transmission electron microscopy (TEM) using energy dispersive analysis (EDX), energy filtered analysis (EFTEM) within a temperature range between RT and 300 °C. Due to the strong increase of the sheet resistance of the sample containing the Ti/Al-barrier, structural changes in the Al layer lead to a failure at 300 °C, whereas the other sample containing Ti only as a barrier layer did not show any obvious structural changes.     

Cu contact on NiSi substrate with a Ta/TaN barrier stack

The thermal and electrical stabilities of Cu contact on NiSi substrate with and without a Ta/TaN barrier stack in between were investigated. Four-point probe (FPP), X-ray diffraction (XRD), scanning electron microscopy (SEM), depth-profiling X-ray photoelectron spectroscopy (XPS), and Schottky barrier height (SBH) measurement were carried out to characterize the diffusion barrier properties. The SBH measurement provides a very sensitive method to characterize the diffusion barrier properties for the copper contact on NiSi/Si. The results show that the Ta/TaN stack can be both thermally and electrically stable after annealing at 450 °C for 30 min and it will have a potential application as a diffusion barrier for Cu contact on NiSi.     

Cu contact on NiSi/Si with thin Ru/TaN barrier

Thin Ru(5 nm)/TaN(15 nm) bi-layer was sputtered on the NiSi/Si substrate as a diffusion barrier in the copper contact structure. The barrier properties were investigated through X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), energy dispersive X-ray (EDX) and electrical measurement. The whole Cu/Ru/TaN/NiSi/Si structure has a good thermal stability until after annealing at 450 °C. The Schottky barrier measurement shows that the leakage current increases after 450 °C annealing and after 500 °C annealing the barrier fails. Failure mechanism of the barrier stack is discussed.