标题: 评估铼膜与含氧铼膜应用于铜金属化之扩散阻障层特性研究
Evaluation of Re and Re(O) as Diffusion Barrier for Cu Metallization on Si/SiO2 Substrats
作者: 沈俊宏
Jiun-Hung Shen
张立
Li Chang
材料科学与工程学系
关键字: 铜金属化制程;扩散阻障层;铼;含氧铼膜;溅镀
公开日期: 2000
摘要: 在未来超大型积体电路元件中,铜导线因其具有更佳的导电性及抗电致迁移的能力而将取代铝导线,但铜极容易扩散进入矽基材,为克服此一问题,必须在矽与铜之间寻求一具有低电阻系数、高热稳定性及良好界面附着性的扩散阻障层。本实验主要是在探讨以Re与Re(O)薄膜做为铜与矽之间扩散阻障层的反应,由扩散、相变化的观点来讨论其变化。所采用的镀膜结构如下:
Cu (100 nm) / Re (50 nm) / SiO2 (20nm) / Si
Cu (100 nm) / Re (20 nm) / SiO2 (20nm) / Si.
Cu (100 nm) / Re(O)-4%O2 (20 nm) / SiO2 (20nm) / Si
Cu (100 nm) / Re(O)-1%O2 (20 nm) / SiO2 (20nm) / Si
铜膜及阻障层以溅镀法沉积。对试片做300~800℃/ 30分钟的氮气气氛退火处理,以四点探针量测片电阻,扫瞄式电子显微镜(SEM)用来观察铜膜表面型态,欧杰电子能谱仪(AES)做成分纵深分析,X光绕射仪(XRD)做相的鉴定,并利用穿透式电子显微镜(TEM)做镀膜截面的观察,分析各层结构的变化。
研究结果显示这几种不同的结构在退火后有不同的行为,Cu (100 nm) / Re (50 nm) / SiO2 (20nm) / Si结构与Cu (100 nm) / Re(O)-4%O2 (20 nm) / SiO2 (20nm) / Si结构在800 ℃/30分钟退火后片电阻值明显上升,Cu (100 nm) / Re (20 nm) / SiO2 (20nm) / Si.结构在750 ℃/30分钟退火后片电阻值有明显的上升,Cu (100 nm) / Re(O)-1%O2 (20 nm) / SiO2 (20nm) / Si在700 ℃/30分钟退火后片电阻值开始上升,其造成电阻上升的原因为表面铜膜产生球化不连续的结团所导致。比对XRD、AES、TEM的结果,各结构在退火温度750 ℃以上,阻障层与铜膜并无产生反应,显示阻障层仍能维持其热稳定性。
由实验结果可知Cu / Re / SiO2 / Si 结构与Cu / Re(O) / SiO2 / Si皆具有低电阻、高热稳定性,其镀膜结构变化将于本文中讨论。
In future ULSI devices copper will replace aluminum as the conducting metal due to their better conductivity and superior resistance to electromigration. The difficulty is that copper diffuses with extreme ease into silicon and this cannot be tolerated. The problem to be solved here is to find a diffusion barrier between copper and silicon which should have low resistivity, high thermal stability, and good adhesion with copper and substrate.
In this study, we investigated the diffusion barrier properties of Re and Re(O) thin films for Cu metallization in ULSI circuit devices. The following structures , Cu (100 nm) / Re (50 nm) / SiO2 (20nm) / Si, Cu (100 nm) / Re (20 nm) / SiO2 (20nm) / Si, Cu (100 nm) / Re(O)-4%O2 (20 nm) / SiO2 (20nm) / Si, Cu (100 nm) / Re(O)-1%O2 (20 nm) / SiO2 (20nm) / Si, were deposited by DC sputtering. Annealing was carried out in nitrogen at temperatures ranging from 300 to 800 ℃ for 30 min. Sheet resistances were measured by a four-point probe method. Copper surface morphplogy was inspected by scanning electron microscopy. Auger electron spectroscopy was used to evaluate the inter-diffusion across the interfaces by the compositional depth profile. The phase identification was performed by XRD. The microstructure was investigated by cross-sectional transmission electron microscopy with X-ray energy dispersive spectroscopy.
Sheet resistance measurement and microstructural characterization show that these structures have different behaviors after annealing. The sheet resistance of Cu (100 nm) / Re (50 nm) / SiO2 (20nm) / Si and Cu (100 nm) / Re(O)-4%O2 (20 nm) / SiO2 (20nm) / Si increased steeply after 800 ℃/30 min annealing. The sheet resistance of Cu (100 nm) / Re (20 nm) / SiO2 (20nm) / Si and Cu (100 nm) / Re(O)-1%O2 (20 nm) / SiO2 (20nm) / Si increased after annealing at 750 ℃ and 700 ℃ respectively. The resistance increase was due to the spheroidization of Cu thin film. The results of XRD, AES, and TEM analyses indicated all barriers remains stable up to 750 ℃/30 min annealing.
From these results, the both structures of Cu / Re / SiO2 / Si and Cu / Re(O) / SiO2 / Si have low resistivity, high thermal stability. The difference between all structures will be discussed.
URI: http://140.113.39.130/cdrfb3/record/nctu/#NT890159040
http://hdl.handle.net/11536/66663
显示于类别:Thesis