Cu/Cu(Ge,Zr)/SiO_2/Si多层膜界面可控反应及热稳定性研究

CONTROLLED REACTION ON INTERFACE OF Cu/Cu(Ge,Zr)/SiO_2/Si MULTILAYER FILM AND ITS THERMAL STABILITY

利用多靶磁控溅射技术在SiO_2/Si基体上沉积Cu/Cu(Ge,Zr)多层薄膜,采用四探针仪(FPPT),X射线衍射仪(XRD),高分辨透射电镜(HRTEM),X射线光电子能谱(XPS)和原位纳米电子束探针能谱(EDS)表征多层薄膜退火前后电阻率、微观结构和界面成分的演变及行为.结果表明,在低温退火阶段(<200℃),Cu(Ge,Zr)膜层中Ge与Cu选择性反应形成低阻Cu_3Ge相,有效抑制Cu与Si的早期扩散;在高温下(>450℃),Zr原子在Cu_3Ge/SiO_2界面析出并与SiO_2层进一步反应形成稳定非晶ZrOx/ZrSiyOx化合物.Cu(Ge,Zr)薄膜中异质原子及与相邻膜层间分步选择性自反应合成高热稳Cu_3Ge/ZrO_x/ZrSi_yO_x复合阻挡层,使Cu/Cu(Ge,Zr)/SiO_2/Si多层膜具有高热稳定性.

A selLformation barrier method using CuX （X=Mn, Ti, Zr, Ru, RuN, WN, Ge, etc.） alloys with various concentration solutes has been extensively investigated to meet the requirements of low sheet resistivity, ultra thin and high thermal stability for Cu metallization. However, intolerable reactions would take place at the interface of the Cu alloy layer and Si02/Si layer before the processing temperature reaches high enough to drive the mass migration of alloy elements to interface. In fact, the reaction of Cu alloy layer with SiO2/Si layer is almost unavoidable due to that Cu diffuses very fast in Si substrate below 200℃. Among those Cu-based alloys, CuGe alloy system has received particularattention because Cu can directly react with Ge below 150 ℃ and forms c-Cu3Ge films which exhibit a remarkable resistivity （5.5 μΩ.cm）, and the CuaGe films also possess high oxidation resistance and interface bonding performance, so can be used as a good diffusion barrier for Cu as well. However, two major problems prevent it from being put into practice. The first is that the mutual diffusion occures between the Cu3Ge films and the Si substrates above 400 ℃, and lead to a notable increase in resistivity. The second one is that the germanide film degrades morphologically at 350 ℃. Therefore, according to the deficiencies existing in these Cu based alloys, the main objective of the present research aims at taking advantage of the selective reaction characteristic of Cu, Ge and Zr elements to achieve a controlled interface reaction behavior of Cu/Cu（Ge, Zr）/SiO2/Si multilayer. The multilayer structure was characterized by FPPT, XRD, TEM, XPS and EDS. The results showed that the reaction sequence of the atoms in Cu（Ge, Zr） films and adjacent layers affected the thermal stability of Cu/Cu（Ge, Zr）/SiO2/Si multilayer structure. Under the temperature of 200 ℃, Ge atoms reacted selectively with Cu film and produced e-Cu3Ge phase which exhibitted a remarkably low metallic resistivity, and the CuaGe phase could be used as a good diffusion barrier. With further increasing annealing temperature （above 450 ℃）, Zr atoms precipitated at the interface or grain boundary of CuaGe layer and reacted with silicon oxide further to form stable and ultra--thin amorphous ZrOx/ZrSiyOx compounds. So the CuaGe layer combined with the amorphous ZrOx/ZrSiyOx compounds provided superior barrier DroDerties in reducing Cu diffusion into Si at high annealed temperature.