Advances in La-Based High-k Dielectrics for MOS Applications

Abstract

This paper reviews the studies on La-based high-k dielectrics for metal-oxide-semiconductor (MOS) applications in recent years. According to the analyses of the physical and chemical characteristics of La2O3, its hygroscopicity and defects (oxygen vacancies, oxygen interstitials, interface states, and grain boundary states) are the main problems for high-performance devices. Reports show that post-deposition treatments (high temperature, laser), nitrogen incorporation and doping by other high-k material are capable of solving these problems. On the other hand, doping La into other high-k oxides can effectively passivate their oxygen vacancies and improve the threshold voltages of relevant MOS devices, thus improving the device performance. Investigations on MOS devices including non-volatile memory, MOS field-effect transistor, thin-film transistor, and novel devices (FinFET and nanowire-based transistor) suggest that La-based high-k dielectrics have high potential to fulfill the high-performance requirements in future MOS applications.

Boronization: A General Strategy for Rare Earth Oxides with Enhanced High-κ Gate Dielectric Performance

“…These defects will seriously deteriorate film density, moisture resistance, surface morphology, and electrical properties. Generally speaking, the moisture resistance of an oxide depends on both the intrinsic property (characterized by the Gibbs free energy change Δ G in the moisture absorption reaction based on thermodynamic analysis) and external factors (film density and defects such as V O and –OH). − REOs especially the Ln group ones usually show a hygroscopic nature due to the large negative Δ G . The hygroscopic behavior is also severely affected by external factors like defects (e.g., V O and –OH) in the thin film, which is the case for our sol–gel Sc 2 O 3 .…”

“…Rare earth oxides (REOs) have received considerable attention in optical, electronic, biomedical, and sustainable energy fields owing to their unique physical and chemical properties. − REOs are usually in the form of RE 2 O 3 , where RE denotes rare earth elements in the lanthanide group (from La to Lu) plus Sc and Y (Figure S1). One of the most fascinating applications for REOs is that they can be used as high-κ gate dielectrics, which are indispensable for current generation and future electronic devices. − …”

“…The advantages of high-κ REOs are their suitable κ values, relatively large band gaps, high conduction band offset, and excellent thermodynamic properties. − Unfortunately, the serious hygroscopicity and high defect states (e.g., oxygen vacancies, hydroxyls, grain boundary states, and interface states) are the main problems for high-performance REOs-based high-κ dielectrics. − Two mechanisms have been proposed to account for the hygroscopic issue of REOs: the intrinsic factor due to the small lattice energy of most REOs and external factors like defects in REOs. − On the anther hand, most REO thin films are fabricated by capital-intensive vacuum-based technologies like atomic layer deposition (ALD), pulsed laser deposition (PLD), molecular beam epitaxy, and metal–organic chemical vapor deposition (MOCVD). − Recently, solution-processed approaches have been pursued due to their simplicity, low cost, easy control of chemical composition/doping, and scalability. − However, compared with vacuum-based approaches, solution-based high-κ REOs usually contain more defects and hence are more hygroscopic, which severely deteriorate the surface morphologies and electrical performance. − Therefore, it is a great challenge to fabricate high-quality high-κ REOs by solution approaches. It should be mentioned that the fabrication of REOs is immature even by using the vacuum-based techniques compared with other well investigated high-κ oxides (e.g., Al 2 O 3 , HfO 2 , and ZrO 2 ). − Several methods including precursor engineering, postannealing treatments, and doping another high-κ dielectric (e.g., Al 2 O 3 , HfO 2 , and ZrO 2 ) have been developed to enhance the high-κ REO performance. − However, relatively high leakage current, low breakdown electric field, frequency-dependent capacitance characteristics, and poor transistor performance are still observed in the reported high-κ REOs. Furthermore, most previous approaches focus on only one kind of REO...…”

Distinct ρ-based model of silicon N-channel double gate MOSFET

“…During the simulation of proposed device, the analysis on effect of positions on the gate boundary is made. The characteristics of number of three grains connected boundary surfaces depends on ρ value predicted, it is made through the ballistic approach for the defined device gate material of dielectric polycrystalline structure [27], as drift diffusion is constant at boundary of device gate layers, causing the usage of grains with size of 1 nm only. Comparative device parameters considered in this work are shown in Following proposed work achieved simulation results show three grain sizes for ρ=1 u, ρ=3 u, and ρ=5 u, representing two front gate grains and one back gate grain in the location of positions ρ=1 u, ρ=5 u, and position ρ=3 u respectively.…”

Mg:TiO2 alloy thin films based MOS capacitors grown on GaAs substrates

“…Intel has introduced high-k dielectrics for 45 nm CMOS technology to reduce the power feeding. The behaviour of high-k dielectrics like hafnium oxide (HfO2) [2], aluminium oxide (Al2O3) [3], lanthanum oxide (La2O3) [4], zirconium oxide (ZrO2) [5] and titanium dioxide (TiO2) [6,7] deposited on Si substrates have been studied extensively. The issues like leakage current and reliability of the devices were identified to be related to the Si substrate.…”