Choel-hwyi Bae

Effects of remote plasma pre-oxidation of Si substrates on the characteristics of ALD-deposited HfO2 gate dielectrics

We investigated the physical and electrical characteristics of a HfO 2 /ultrathin SiO 2 (∼0.5 nm)/Si structure grown by a remote plasma atomic layer deposition (RPALD). The HF-cleaned Si substrate was oxidized by a remote plasma oxidation (RPO) process and yielded a ∼0.5 nm thick SiO 2 layer. HfO 2 films were deposited on both H-terminated and RPO-treated Si substrates by the RPALD. During HfO 2 film deposition, the RPO-treated sample showed more effectively retarded formation of initial Hf silicate layers than the sample on H-terminated Si. RPO treatment also improves electrical properties including hysteresis, effective fixed oxide charge density (Q f,eff ) and equivalent oxide thickness (EOT).

Characteristics of Metal–Oxide–Semiconductor Field-Effect Transistors with HfO2/SiO2/Si and HfO2/SiOxNy/Si Stack Structures Formed by Remote Plasma Technique

Thin SiO2 and SiOxNy layers were grown on Si substrates using remote plasma oxidation and nitridation, respectively, to use as buffer layers prior to HfO2 deposition. Subsequently, HfO2 films were grown on these buffer layers by remote plasma atomic layer deposition (RPALD). The SiO2 and SiOxNy buffer layers suppressed the growth of Hf silicate at the interface during HfO2 deposition, suppressed the increase in total oxide capacitance, and induced the decrease in effective fixed oxide charge density. Metal–oxide–semiconductor field-effect transistors (MOSFETs) with buffer layers exhibited a higher drain current (Id) and effective carrier mobility (µeff) than those without buffer layers. The incorporated N atoms in SiO2 buffer layer reduced both Id and µeff of MOSFETs due to the increase of defect charge in the interfacial region, compared to SiO2 buffer layer including no N atom.

Remote Plasma Atomic Layer Deposition of HfO2 Thin Films Using the Alkoxide Precursor Hf ( mp ) 4

Hafnium 3-methyl-3-pentoxide precursor, Hf(mp) 4 , was newly synthesized as an alkoxide precursor and used to deposit HfO 2 films by remote plasma atomic layer deposition (ALD). The characteristics of the HfO 2 films were compared with the films deposited using tetrakis(diethylamido)hafnium [Hf(NEt 2 ) 4 ] which is used frequently for ALD processes. The HfO 2 films deposited with the Hf(mp) 4 had a well-controlled rate of deposition at low temperatures and maintained a low amount of carbon contamination. In addition, the HfO 2 films deposited by using Hf(mp) 4 exhibited a higher phase transition temperature and lower leakage current densities than those of HfO 2 films deposited using Hf(NEt 2 ) 4 .

SRAM stability design comprehending 14nm FinFET reliability

Importance of low voltage operation of SRAM in mobile application is ever increasing for longer battery life. SRAM occupies a significant portion of the total area and power for the SOC ICs (>10-30MByte used in AP/CPUs). For the operation of SRAM at low voltage, proper noise margin for read, disturb and write operation is important since noise margin reduces with technology scaling and low voltage operation. Previously, we presented a method on SRAM Vmin design and characterization before and after High Temperature Operating Life (HTOL) stress test [1-3]. In this work, we extend our method to account for end-of-life aging into statistical SRAM cell design with Z-score method on 14nm FinFET technology. Excellent Vmin behavior at both time0 and EOL satisfying 10yrs was demonstrated at the product level.