A simple approach to form Ge nanocrystals embedded in amorphous Lu ₂ O ₃ high- k gate dielectric by pulsed laser ablation

Abstract

We have successfully developed a novel method to fabricate the memory structure of Ge nanocrystals embedded in amorphous Lu2O3 high-k dielectric using pulsed laser ablation. The mean size and aerial density of the Ge nanocrystals are estimated to be about 9 nm and 7 × 10 11 cm −2 , respectively. Good performances in terms of large memory window and long data retention were observed. Our preparation method is simple, fast and economical.

A Review on Ge Nanocrystals Embedded in SiO2 and High‐k Dielectrics

“…Lu 2 O 3 has a high permittivity of approximately 12 and a large band gap of about 5.5 eV . It is, therefore, an interesting high‐k matrix for the Ge nanocrystals.…”

“…Ge‐rich Lu 2 O 3 films were deposited by PLD . The samples were annealed at 400 °C to activate the phase separation process, which leads to the formation of Ge nanocrystals within an amorphous matrix . It is worth to note that the crystallization temperature of the Ge nanoparticles is much smaller in Lu 2 O 3 than in other high‐k matrices.…”

“…Ge nanocrystals in Lu 2 O 3 were investigated for the use in non‐volatile memory devices and for optical applications . The reported memory window of 1.2 V is relatively small .…”

Formation of Ge Nanocrystals in Lu2O3 High-k Dielectric and its Application in Non-Volatile Memory Device

“…The laser deposition was carried out in a high vacuum system with a background pressure of about -7 10 6 × Torr with the target rotating at about 30 rounds/min and the substrate at room temperature. The wavelength of the excimer laser is 248nm and the laser energy density is around 1.5 J/cm 2 with frequency of 5 Hz.…”

“…Recently, metal-oxide-semiconductor field-effect transistor (MOSFET) memory structures utilizing semiconductor nanocrystals as discrete charge storage nodes have attracted much attention as a potential candidate to replace the conventional floating-gate memory devices for better scaling capabilities. Different high-k dielectric materials have been demonstrated for memory device applications, including HfO 2 [3,4], ZrO 2 [5,6], Al 2 O 3 [6], HfAlO [7,8], and LaAlO 3 [9] and Lu 2 O 3 [10]. Hence recent efforts have focused on the utilization of high-k dielectrics in nanocrystal memory devices to achieve both good retention time and low voltage operation due to the unique band asymmetry in the programming and retention modes [3].…”