Study of enhanced DC and analog/radio frequency performance of a vertical super-thin body FET by high-k gate dielectrics

摘要

This article reports the DC and analog/radio frequency (RF) response of anewly invented device called vertical super-thin body (VSTB) FET towardshigh-k (Si_3N_4/HfO_2) and low-k (SiO_2) gate dielectrics in conjunctI_(on) with thescaling effect through a well-calibrated Sentaurus TCAD tool. At channellength (L_G) of 20 nm, compared to SiO_2, Si_3N_4 improves various DC parameterssuch as off-state leakage current (I_(off)), on-current (I_(on)), on-to-off currentratio (I_(on)/I_(off) ratio), subthreshold swing (SS), and drain-induced-barrierlowering(DIBL) by 77.15%, 26.2%, one order of magnitude, 15.78%, and 36.2%,respectively. On the other hand, a higher improvement is seen in all these DCparameters for the HfO_2 gate dielectric (I_(off), I_(on), I_(on)/I_(off) ratio, SS, DIBLimproves respectively by 91.8%, 41.57%, two orders of magnitude, 28.28%, and62.71%). The underlying physics behind such excellent improvement isexplained by the device off-state energy band diagram, electrostatic potential,and channel electron density profile for each dielectric. Further, for all the gatedielectrics considered, the device characteristics were studied for a wide rangeof L_G from 10 to 50 nm to reveal the scaling impact on the device performance.Irrespective of the gate dielectric material, the device exhibits excellent performanceat L_G = 10 nm, which in turn indicates to the brilliant scalability of thisnew device. Besides, although Si_3N_4 and HfO_2 increase gate capacitance (C_(gg))/gate-drain capacitance (C_(gd)), due to the extremely low values of C_(gg)/C_(gd),enhanced unit gain cut-off frequency, and gain-bandwidth-product is achieved.In additI_(on), the increased transconductance (g_m) of the device applying Si_3N_4/HfO_2 gate dielectric leads to a higher peak value of TGF, intrinsic gain, TFP,GFP, and GTFP. This study intends to expand the fundamental knowledgeabout such a new device as a VSTB FET and hence, aims to be utilized in thefuture research of this novel device.