Processing and Properties of Ferroelectric Pb(Zr,Ti)O 3 /Silicon Carbide Field-Effect Transistor

Abstract

Metal-ferroelectric-(insulator)-semiconductor MF(I)S structures have been fabricated and the properties of pulsed laser-deposited PZT/Al 2 O 3 gate stacks have been studied on n-and p-type 4H-SiC. Among several polytypes of SiC, 4H-SiC is considered as the most attractive one because of its wider bandgap (E g ∼ = 3.2 eV) as well as higher and more isotropic bulk mobility than other polytypes. Single PZT phase without a preferred orientation was confirmed by x-ray diffraction. The interface trap densities N IT , fixed oxide charges Q F , and trapped oxide charges Q HY have been estimated by C-V curves with and without photo-illuminated measurements at room temperature. It is found that the charge injection from SiC is the dominant mechanism for C-V hysteresis. Importantly, with PZT/Al 2 O 3 gate stacks, superior C-V characteristics with negligible sweep rate dependence and negligible time dependence under the applied bias were obtained compared to PZT directly deposited on SiC. The MFIS structures exhibited very stable capacitance-voltage C-V loops with low conductance (<0.1 mS/cm 2 , tan δ ∼ 0.0007 at 400 kHz) and memory window as wide as 10 V, when 5 nm-thick Al 2 O 3 was used as a high bandgap (E g ∼ 9 eV) barrier buffer layer between PZT (E g ∼ 3.5 eV) and SiC (E g ∼ 3.2 eV). The structures have shown excellent electrical properties promising for the gate stacks as the SiC field-effect transistors (FETs). Depletion mode transistors were prepared by forming a Pb(Zr 0.52 Ti 0.48 )O 3 /Al 2 O 3 gate stack on 4H-SiC. Based on this structure, ferroelectric Pb(Zr,Ti)O 3 (PZT) thin films have been integrated on 4H-silicon carbide (SiC) in a SiC field-effect transistor process. Nonvolatile operation of ferroelectric-gate field-effect transistors in silicon carbide (SiC) is demonstrated. 1221 1222 SANG-MO KOO et al.

Deposition and characterization of high-K (Ca,Sr)ZrO3 thin films using sol-gel technique

“…The most common of these are simple metal oxides such as TiO 2 [22][23][24][25][26], Ta 2 O 5 [27][28][29][30][31][32][33][34][35][36][37][38], Al 2 O 3 [39][40][41][42], ZrO 2 [43][44][45][46] and HfO 2 [47][48][49][50][51][52]. Ferroelectric materials such as PZT (lead zirconate titanate) [53,54] have also been suggested as gate dielectrics. A summary of the appropriate materials properties for the selection of materials for gate dielectric applications will be discussed in the next section.…”