Metal/Ge Contact And Ge SB-MOSFET Electrical Characteristics Simulation And Ni Ge/Ge Contact Experimental Study

As the development speed of Moore's Law gradually slows down,the continuous reduction of MOSFET feature size faces many physical limitations,such as the sharp increase in series resistance between source and drain.For this reason,Schottky barrier source-drain MOSFET(SB-MOSFET)came into being,which can significantly reduce the parasitic resistance of the source and drain regions.On the other hand,high-mobility channel materials(Ge and III-V compound semiconductors)are expected to replace silicon as the substrate material for CMOS devices and become an international research hotspot.However,due to the higher interface state density of Ge and metal contact,a“Fermi pinning”effect will occur,which partially offsets the advantages of SB-MOSFET.Based on this,in this paper the Silvaco TCAD simulation software is used to first analyze the influence of the Schottky barrier height on the on/off current of the metal-semiconductor contact and its switching ratio.Then,the Ni Ge/Ge metal-semiconductor junction,the influence of thermal annealing on its contact characteristics was studied.Finally,the electrical characteristics of Ge and Ge OI SB-MOSFETs were simulated and analyzed using Silvaco software.First,Silvaco software is used to analyze the influence of different electronic Schottky barrier heights(e SBH)on the electrical characteristics of metal/n-Ge contacts and metal/p-Ge contacts.The results show that for the metal/n-Ge contact,the higher the e SBH,the smaller the off-state current of the Schottky diode;for the metal/p-Ge contact,as the e SBH increases,it exhibits an ohmic-like contact characteristic.On this basis,the influence of different substrate doping concentrations on metal/n-Ge and metal/p-Ge is further analyzed,and it is found that the higher the doping concentration,the on-state and off-state currents of the metal/n-Ge contact are both As for the metal/p-Ge contact,the higher the doping concentration,the more obvious the ohmic contact characteristics;the analysis of the alloy depth shows that as the alloy depth increases,the off-state current increases.Based on the above simulation structure,the Ni Ge/Ge metal-semiconductor junction was prepared experimentally,and the influence of different annealing temperatures and different doping concentrations on the contact characteristics of Ni Ge/n-Ge,Ni Ge/p-Ge and the back-to-back connection of the two was analyzed.The e SBHextracted from the current density-voltage(J-V)curve shows that the annealing temperature can adjust the Schottky barrier height of Ni Ge/Ge contact,and it is consistent with the simulation trend.As the substrate doping concentration increases,for Ni Ge/n-Ge contacts,the rectification characteristics of Schottky diodes deteriorate,and both on-state current and off-state current increase;for Ni Ge/p-Ge contacts,the more the contact resistance decreases,the more obvious the ohmic contact characteristics.Combined with the on-state and off-state characteristics of SB-MOSFET,the appropriate substrate concentration is determined to be1×10¹⁴cm^-3 and the optimal annealing temperature is 450°C.Finally,Silvaco was used to simulate the SB-MOSFET.Under the appropriate substrate concentration determined above,for the e SBH valuesextracted at different annealing temperatures for Ni Ge/n-Ge contacts,the influence on the electrical characteristics of the SB-MOSFET is analyzed,and then the e SBH which was extracted from 450°C value is verified.Then the influence of the source-drain Ni Ge alloy depth(T_{Ni Ge})on the electrical characteristics of the SB-MOSFET is analyzed,and it is found that the device performance is the best when T_{Ni Ge}=10nm.On this basis,the electrical performance of Ge and Ge OI-based SB-MOSFETs are compared.The results show that the off-state current of the latter is reduced by about three orders of magnitude compared with the former.From this,the influence of the thickness of the Ge layer(T_Ge)in Ge OI on the electrical performance is further analyzed.It is concluded that when T_Ge=10nm,the channel is fully consumed.At the end,excellent electrical properties of the device can be obtained.These simulation analysis results have a guiding role in the design and preparation of actual SB-MOSFET.