含Cu硅基铁电电容器集成过程中Ni-Al阻挡层的研究
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摘要
寻找性能良好的阻挡层来抑制Cu的扩散一直是Cu互连技术的关键,因此,研究阻挡层的失效机理对于提高互连可靠性具有重要的意义。采用射频磁控溅射技术构架Cu／Ni-Al／SiO2／Si、Cu／Ni-Al／Si、Cu／Ta／Ni-Al／Si异质结,并进行高真空退火.利用x射线衍射(XRD)、四探针电阻测试仪、原子力显微镜(AFM)和透射电子显微镜(TEM)对样品微结构、输运性质、表面形貌和界面进行了分析表征。结果表明,在750℃的高温退火后Cu/Ni-Al/SiO2/Si和Cu/Ni-Al/Si异质结内没有明显的反应和互扩散发生,Cu/Ta/Ni-Al/Si在高达800℃退火后仍然没有硅铜化合物出现,退火过程中Ni-Al一直保持非晶状态。超薄的Ni-Al(4.5 nm)和Ta(3 nm)／Ni-Al(3 nm)阻挡层表现出了良好的阻挡效果。
从Fick第二定律和扩散方程入手,通过计算扩散激活能来研究Ni-Al的阻挡性能。Cu在Ni-Al中具有较大的扩散激活能(2.9 eV),表明Ni-Al对Cu的扩散起到了良好的阻挡效果。阻挡层微结构是影响Cu互连阻挡层性能的关键因素,非晶结构没有晶界存在,不能为Cu提供快速扩散路径。
采用溶胶-凝胶(Sol-Gel)法在Cu／Ni-Al／Si异质结基础上集成Lao.5Sr0.5CoO3(LSCO) /Pb(ZrxTi1-x)O3(PZT)/La0.5Sr0.5CoO3(LSCO)铁电电容器。利用铁电测试仪对其铁电性能进行了研究,结果发现电容器有良好的电滞回线、较高的极化强度(28μC／cm2)、较小的矫顽电压(1.6 V)和较小的漏电流密度(104 A／cm2)。
It is crucial to find an appropriate diffusion barrier for Cu interconnection technology; therefore, it is very important for investigating the failure mechanism of the barrier layer in order to increase its reliability. The Cu/Ni-Al/SiO2/Si, Cu/Ni-Al/Si, and Cu/Ta/Ni-Al/Si heterostructure are prepared at room temperature by magnetron sputtering method and annealed in an ultra-high vacuum system. Sheet resistance, x-ray diffraction, atomic force microscopy and high resolution transmission electron microscopy are used to study the microstructures, transport properties, surface morphology and interfaces of the samples. It is found that no obvious reactions or interdiffusion occur in the Cu/Ni-Al/SiO2/Si and Cu/Ni-Al/Si samples annealed at 750℃, and no Cu silicide is observed for Cu/Ta/Ni-Al/Si samples annealed at 800℃. All the Ni-Al film of the samples keep amorphous. Both the Ni-Al(5 nm) and the Ta (3 nm)/Ni-Al (3 nm) bilayer films are excellent diffusion barrier for Cu metallization.
Based on the diffusion equation and fick's second law, we calculated the activation energy to study the barrier properties. Ea for Ni-Al film is 2.9 eV, indicating Ni-Al film has good barrier property. The microstructure of the barrier materials impacts the performance of the barrier layer for Cu diffusion barrier. Amorphous Ni-Al film can be used as good barrier layer since it lacks grain boundaries, which can act as the high diffusivity path.
La0.5 Sr0.5CoO3 (LSCO)/Pb(ZrxTi1-x)O3 (PZT)/La0.5Sr0.5CoO3 (LSCO) ferroelectric capacitor has been integrated on Cu/Ni-Al/Si substrate by combining Sol-Gel and magnetron sputtering methods. Ferroelectric properties are studied by a ferroelectric tester. It is found that the hysteresis loop is well saturated at 12V. Moreover, the capacitor has low coercive voltage, high remnant polarization, low leakage current density.
从Fick第二定律和扩散方程入手,通过计算扩散激活能来研究Ni-Al的阻挡性能。Cu在Ni-Al中具有较大的扩散激活能(2.9 eV),表明Ni-Al对Cu的扩散起到了良好的阻挡效果。阻挡层微结构是影响Cu互连阻挡层性能的关键因素,非晶结构没有晶界存在,不能为Cu提供快速扩散路径。
采用溶胶-凝胶(Sol-Gel)法在Cu／Ni-Al／Si异质结基础上集成Lao.5Sr0.5CoO3(LSCO) /Pb(ZrxTi1-x)O3(PZT)/La0.5Sr0.5CoO3(LSCO)铁电电容器。利用铁电测试仪对其铁电性能进行了研究,结果发现电容器有良好的电滞回线、较高的极化强度(28μC／cm2)、较小的矫顽电压(1.6 V)和较小的漏电流密度(104 A／cm2)。
It is crucial to find an appropriate diffusion barrier for Cu interconnection technology; therefore, it is very important for investigating the failure mechanism of the barrier layer in order to increase its reliability. The Cu/Ni-Al/SiO2/Si, Cu/Ni-Al/Si, and Cu/Ta/Ni-Al/Si heterostructure are prepared at room temperature by magnetron sputtering method and annealed in an ultra-high vacuum system. Sheet resistance, x-ray diffraction, atomic force microscopy and high resolution transmission electron microscopy are used to study the microstructures, transport properties, surface morphology and interfaces of the samples. It is found that no obvious reactions or interdiffusion occur in the Cu/Ni-Al/SiO2/Si and Cu/Ni-Al/Si samples annealed at 750℃, and no Cu silicide is observed for Cu/Ta/Ni-Al/Si samples annealed at 800℃. All the Ni-Al film of the samples keep amorphous. Both the Ni-Al(5 nm) and the Ta (3 nm)/Ni-Al (3 nm) bilayer films are excellent diffusion barrier for Cu metallization.
Based on the diffusion equation and fick's second law, we calculated the activation energy to study the barrier properties. Ea for Ni-Al film is 2.9 eV, indicating Ni-Al film has good barrier property. The microstructure of the barrier materials impacts the performance of the barrier layer for Cu diffusion barrier. Amorphous Ni-Al film can be used as good barrier layer since it lacks grain boundaries, which can act as the high diffusivity path.
La0.5 Sr0.5CoO3 (LSCO)/Pb(ZrxTi1-x)O3 (PZT)/La0.5Sr0.5CoO3 (LSCO) ferroelectric capacitor has been integrated on Cu/Ni-Al/Si substrate by combining Sol-Gel and magnetron sputtering methods. Ferroelectric properties are studied by a ferroelectric tester. It is found that the hysteresis loop is well saturated at 12V. Moreover, the capacitor has low coercive voltage, high remnant polarization, low leakage current density.
引文
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[7]P.Heng at al, International Symposium on VLSI TSA,1995, p.164.
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