Research On Modulation Of Metal Semiconductor Interface

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.