金属半导体接触界面的调制研究

【作者】 于浩；

【导师】 蒋玉龙；

【作者基本信息】 复旦大学 ， 微电子学与固体电子学， 2013， 硕士

【摘要】 随着集成电路向着不断微缩化的方向发展,对具有高迁移率的半导体材料的研究日益密切。然而,由于工艺原理等方面的差异,新型高迁移率半导体材料的应用还存在着诸多困难,而金半接触结构即是诸多困难之一。因而,如何解决新型高迁移率半导体的金半接触问题显得尤为重要。锗与(110)晶向硅衬底皆为具有应用前景的高迁移率半导体材料,本论文着重研究在这两种衬底上金半接触界面特性的调制。单晶锗的电子和空穴迁移率皆高于传统硅衬底。然而,锗半导体表面存在着严重的费米能级钉扎问题,该问题不仅严重影响锗NMOSFET器件的反型工作性能,还导致金属与n型锗之间过高的接触电阻。对于弱化锗表面费米能级钉扎问题,在锗表面生长超薄介质层是目前非常有效的方法。本论文中尝试在Al/n-Ge接触中以O2或NH3远程等离子体表面处理制备超薄Ge02或者GeON界面层解除费米能级钉扎。电学测试结果表明GeON超薄层解钉扎成功,而Ge02超薄层解钉扎失效,引入GeO2超薄层的Al/n-Ge接触势垒高度值与无界面层的直接接触情况相似。通过XTEM照片以及SIMS测试的观察发现,Ge02超薄层厚度异常,局部出现Al的扩散渗透,破坏了GeO2的完整性与平整度,进而引起了解钉扎失败。Si(110)衬底具有高的空穴迁移率,但Si(110)衬底上的镍硅工艺研究还十分有限。过去的研究表明,引入Ti元素可以提高Si(100)衬底上镍硅的平整度和热稳定性并可以降低接触漏电。本论文分别以T覆盖层、Ti中间层或NiTi共溅射的形式引入Ti元素研究Si(110)衬底上镍硅生长的特性。分析表明,Ti元素对于Si(110)上镍硅的影响与Si(100)类似。引入T覆盖层的样品在350～400℃的温度开始产生低阻的NiSi相,但600℃以上电阻急剧上升,NiSi相并未消失。而引入Ti中间层或NiTi共溅射样品在所观察的退火温度下,未生成NiSi相,在500℃以上开始形成阻值较低的NiSi2相,该相在高达800℃的退火温度下仍保持稳定。另外,XTEM和SAED测试结果表明,Si(110)衬底上的NiTi共溅射样品,在600℃快速热退火后可以生长出高外延质量的NiSi2薄膜。更多还原

【Abstract】 With the integrated circuits developing towards the trend of scaling down in the recent decades, the traditional silicon based devices have approached its physical limits. The research on the novel high mobility semiconductor material is therefore intensified. However, the physical principle and processing technology of novel semiconducot candidates suffer great diffenrence from zhe conventional silicon based knowledge and experience, inducing several serious problems. Among them, the metal semiconductor contacts issue a most important one. Germanium and Si(110) substrates are both promising high mobility semiconductor materials.This thesis focused on the modulation of interfacial properties of these two kinds of contacts.The electron and hole mobility of germanium are both much higher than those of silicon. However, the germanium semiconductor suffers from severe problem of surface Fermi level pinning, which will constrain the performance of germanium based nMOSFET and introduce high contact resistance in the metal n-type germanium contacts. To solve the problem of surface Fermi level pinning, the introduction of ultrathin dielectric layer at the surface of germanium is for now the most effective method. In this thesis, we investigated the depinning effects of plasma induced GeO2and GeON layers in the Al/n-Ge contacts. With the electrical tests, we found the GeON layer successfully depinned the Fermi level while the GeO2layer failed. With XTEM photos and SIMS tests, we confirmed that the failure of GeO2layer as depinning layer is due to the local penetration of aluminium into the ultrathin GeO2layer, which destropys the integrity and morphology of the layer.Si(110) exhibits higher hole mobility, while the knowledge of nickel silicide on Si(110) has not been fully discussed. The introduction of Ti into nickel silicide on Si(100) has been confirmed to enhance the thermal stability and reduce the leakage current of silicide contact. In this thesis, the influence of Ti capping layer, Ti interlayer and NiTi co-doping on nickel silicide on Si(110) will be discussed. The result showed that the introduction of Ti element on nickel silicide on both Si(110) and Si(100) has similar effects. The samples with Ti capping layer exhibit low-resistance NiSi phase with350～400℃RTP, and the resistance grows rapidly with RTP temperature increasing higher than600℃. The introduction of Ti interlayer and the NiTi co-doping samples exhibit similar properties. NiSi phase could not be detected at any RTP temperature in these samples, while stable NiSi2phase expitaxially formed with RTP temperature higher than500℃, which is rather thermally stable even at800℃. In addition, XTEM photos and SAED tests showed, the NiTi co-doping samples on Si(110) have very highly qualified exipixially grown NiSi2thin film.更多还原