Memory Characteristics of Atomic-Layer-Deposited High-κ HfAlO Nanocrystal Capacitors

Abstract

The memory characteristics of atomic-layer-deposited high-HfAlO nanocrystals in a p-Si/SiO 2 /͓HfO 2 /Al 2 O 3 ͔/Al 2 O 3 /platinum structure have been investigated. After the annealing treatment, the high-HfAlO nanocrystals with a small diameter of Ͻ10 nm and high density of Ͼ5 ϫ 10 11 cm 2 have been observed by high-resolution transmission electron microscopy. A large hysteresis memory window of ϳ10.4 V has been obtained. The high-HfAlO nanocrystal memory capacitor with a small capacitance equivalent thickness of ϳ8.5 ± 0.5 nm shows a small leakage current density of ϳ22 A cm 2 at a gate voltage of −16 V. A large memory window of ϳ8 V has also been observed after 10 5 s of retention, due to the charge confinement in the high-HfAlO multilayer nanocrystals.Nanocrystal-based floating gate memory devices have recently attracted much attention due to their potential in the semiconductor industry to overcome the limitations of the polycrystalline-siliconoxide-͓silicon-nitride͔-oxide-silicon ͑SONOS͒ memory. 1,2 To enhance the performance of memory devices, it is important to keep the charge tightly trapped to avoid the charge loss problem of the SONOS memory devices. The high-charge-trapping layers have been reported by several research groups for nonvolatile memory device applications. 3-6 A lot of work has also been reported on nanocrystal floating gate memory devices with different materials, such as Si, 7-9 Ge, 10 SiGe, 11 high-, 12,13 and metal 14-20 for the next generation of nanoscale nonvolatile memory device applications. It is a challenging issue to obtain highly reproducible memory devices with a large memory window, high spatial density, and small size with narrow size distribution of the nanocrystals. We want to solve this common problem using high-nanocrystals formed by atomic layer deposition ͑ALD͒, which has not yet been reported. In this paper, nanoscale memory capacitors with high-HfAlO nanocrystals formed by ALD have been investigated. A large memory window of ⌬V Ϸ 10.4 V, small size of Ͻ10 nm, and high reproducibility of the high-HfAlO nanocrystals have been observed in a p-Si/SiO 2 /͓HfO 2 /Al 2 O 3 ͔/Al 2 O 3 /platinum structure for nanoscale high-performance flash memory device applications. A pure Al 2 O 3 charge-trapping memory device has also been fabricated for comparison.p-Type Si͑100͒ wafers with a resistivity of 15-25 ⍀ cm were cleaned by the RCA process. After cleaning the Si wafers, a tunneling oxide ͑SiO 2 ͒ with a thickness of 3 nm was grown by the rapid thermal oxide system at a substrate temperature of 1000°C for 20 s. Then, the high-HfO 2 ͑ϳ1.2 nm͒/Al 2 O 3 ͑ϳ0.8 nm͒ nanolaminate layers with five periods were grown by ALD. Then, a blocking oxide ͑high-Al 2 O 3 ͒ with a thickness of ϳ10 nm was deposited by ALD. A pure Al 2 O 3 film with a thickness of ϳ20 nm was also deposited on SiO 2 ͑3 nm͒/p-Si substrate by ALD for comparison. The precursor temperatures were 185°C for hafnium tetrachloride ͑HfCl 4 ͒ and 23°C for trimethylaluminium ͓Al͑CH 3 ͒ 3 ͔. The oxidant gas for the Hf and Al...

Characteristics of Gadolinium Oxide Nanocrystal Memory with Optimized Rapid Thermal Annealing

“…1,3,4 To achieve the fast write/ erase and long retention time simultaneously, metal NC memories are presented to engineer the depth of the potential well at storage nodes. Heavy metals, 4-7 silicide, 8,9 nitrided-metal, 10 and metal-oxide 11,12 are NC memories used as storage nodes. Compared with the semiconductor NC memories, metal counterparts exhibit a higher density of states around the Fermi level, stronger coupling with the conduction channel, a wider range of available work functions, and smaller energy perturbation due to carrier confinement.…”

High-Efficiency Silicon Inverted Pyramid-Based Passivated Emitter and Rear Cells

“…Importantly, the effective minority lifetime of annealed samples after 100 s of illumination are 230 μs and 150 μs, respectively, much higher than 126 μs and 48 μs before illumination, demonstrating a very clear light-enhanced c-Si surface passivation of Al 2 O 3 /SiN x layers. The charge trapping effect during light soaking [25][26][27][28] could be one of the main mechanisms for the light-enhanced c-Si surface passivation of Al 2 O 3 /SiN x films. As Al 2 O 3 films are reported to have a negative fixed charge density [29][30][31][32], some of the excess electrons generated by light were likely to be injected or tunneled into trap states in the inner Al 2 O 3 film, resulting in an increased level of fieldeffect passivation.…”

Physical and Memory Characteristics of Atomic-Layer-Deposited High-κ Hafnium–Aluminum-Oxide Nanocrystal Capacitors with Iridium-Oxide Metal Gate

“…The details of the deposition of high-HfO 2 and Al 2 O 3 films can be found elsewhere. 15,19) To form high-HfAlO nanocrystals and improve the charge storage characteristics, postdeposition annealing (PDA) was carried out in the temperature range from 700 to 900 C for 1 min in N 2 ambient. After annealing, the high-HfAlO nanocrystals are formed owing to the diffusion of HfO 2 and Al 2 O 3 films.…”

“…Recently, high-charge trapping layers such as hafnium-oxide (HfO 2 ), aluminum-oxide (Al 2 O 3 ), zirconium-oxide (ZrO 2 ), tantalumoxide (Ta 2 O 5 ), and HfAlO films in a polycrystalline siliconoxide-(silicon-nitride)-oxide-silicon (SONOS) memory structure have been reported by several groups. [15][16][17][18][19][20] Hfbased high-films have a great potential as gate dielectrics as well as in nonvolatile memory applications. To overcome the integration and scaling problems to meet the ITRS requirements, high-nanocrystal memories with advantages including good scalability, high speed with a low P/E voltage operation, and good nonvolatility with reproducibility are an alternative solution for the next generation of nanoscale nonvolatile memory device applications.…”