Effect of Annealing Ambient on the Self-Formation Mechanism of Diffusion Barrier Layers Used in Cu(Ti) Interconnects
Effect of Annealing Ambient on the Self-Formation Mechanism of Diffusion Barrier Layers Used in Cu(Ti) Interconnects
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DOI：
10.1007/s11664-007-0094-8
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发表时间：
2007-04
影响因子：
2.1
通讯作者：
S. Tsukimoto;T. Kabe;K. Ito;M. Murakami
中科院分区：
文献类型：
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作者：
S. Tsukimoto;T. Kabe;K. Ito;M. Murakami
发现低钛浓度的铜(钛)[铜(钛)]薄膜在退火后在薄膜/衬底界面形成了薄的富钛势垒，这被称为阻挡层的自形成。这种铜(钛)合金是用于下一代超大规模集成(ULSI)器件的最佳互连材料之一，这些器件既需要非常薄的阻挡层，也需要低电阻的互连。为了研究退火环境对铜合金电阻率和微观结构的影响，在二氧化硅衬底上制备了铜(7.3at.%Ti)薄膜，并在500℃超高真空(UHV)或含少量杂质氧的Ar气氛中进行了退火处理。薄膜在5 0 0℃超高电压下热处理后，其电阻率没有降低到16μΩ·cm以下。在薄膜中观察到了Cu4Ti金属间化合物的形成，并认为这是导致高电阻率的原因。然而，在随后的Ar中热处理后，这些化合物被发现分解形成表面TiOx和界面势垒层，其电阻率降至3.0TiOx-cm。μΩ-cm。本实验表明，退火过程中氧对钛的反应对界面势垒层的自形成和互连线电阻率的降低起着重要的作用。
Copper (titanium) [Cu(Ti)] films with low titanium (Ti) concentration were found to form thin Ti-rich barrier layers at the film/substrate interfaces after annealing, which is referred to as self-formation of the barrier layers. This Cu(Ti) alloy was one of the best candidates for interconnect materials used in next-generation ultra-large-scale integrated (ULSI) devices that require both very thin barrier layers and low-resistance interconnects. In the present paper, in order to investigate the influences of annealing ambient on resistivity and microstructure of the Cu alloys, the Cu(7.3at.%Ti) films were prepared on the SiO2substrates and annealed at 500°C in ultra-high vacuum (UHV) or argon (Ar) with a small amount of impurity oxygen. After annealing the film at 500°C in UHV, the resistivity was not reduced below 16 μΩ-cm. Intermetallic compounds of Cu4Ti were observed to form in the films and believed to cause the high resistivity. However, after subsequently annealing in Ar, these compounds were found to decompose to form surface TiOxand interfacial barrier layers, and the resistivity was reduced to 3.0 μΩ-cm. The present experiment suggested that oxygen reactive to titanium during annealing played an important role for both self-formation of the interfacial barrier layers and reduction of the interconnect resistivity.