Atomic layer deposition of hafnium oxide on germanium substrates

Abstract

Germanium combined with highdielectrics has recently been put forth by the semiconductor industry as potential replacement for planar silicon transistors, which are unlikely to accommodate the severe scaling requirements for sub-45-nm generations. Therefore, we have studied the atomic layer deposition ͑ALD͒ of HfO 2 high-dielectric layers on HF-cleaned Ge substrates. In this contribution, we describe the HfO 2 growth characteristics, HfO 2 bulk properties, and Ge interface. Substrate-enhanced HfO 2 growth occurs: the growth per cycle is larger in the first reaction cycles than the steady growth per cycle of 0.04 nm. The enhanced growth goes together with island growth, indicating that more than a monolayer coverage of HfO 2 is required for a closed film. A closed HfO 2 layer is achieved after depositing 4-5 HfO 2 monolayers, corresponding to about 25 ALD reaction cycles. Cross-sectional transmission electron microscopy images show that HfO 2 layers thinner than 3 nm are amorphous as deposited, while local epitaxial crystallization has occurred in thicker HfO 2 films. Other HfO 2 bulk properties are similar for Ge and Si substrates. According to this physical characterization study, HfO 2 can be used in Ge-based devices as a gate oxide with physical thickness scaled down to 1.6 nm.

Atomic Layer Deposition of High-k Dielectric Layers on Ge and III-V MOS Channels

“…For the O 3 based process, the intermixing decreases slightly when decreasing the ALD temperature from 300 to 225°C. The presence of GeO x in the high-κ layer indicates that reactions other than the conventional ligand exchange reactions must contribute during ALD on GeO 2 , as suggested previously for HfCl 4 /H 2 O ALD on 0.3 nm GeO x by considering the first reaction cycle (27). …”

“…Still, such small concentrations of Ge in the high-κ layer can affect the ECS Transactions, 16 (10) 671-685 (2008) electrical properties. Note that TOFSIMS cannot determine the oxidation state of Ge in the high-κ layer, but most likely it is present in an oxidized state and not as Ge 0 , as TOFSIMS demonstrated previously that HfCl 4 /H 2 O ALD on HF cleaned Ge substrates results in an abrupt Ge/HfO 2 transition (27). First principles calculations demonstrated that the formation of Ge-O bonds or Hf-O-Ge bonds at or near the interface does not introduce interface states to the Ge energy band-gap (28,29).…”

Perpendicular magnetic anisotropy of Co\Pt bilayers on ALD HfO2

“…A forming gas anneal at 420 C for 20 min is applied to passivate dangling bonds, after which 2.5 nm of amorphous 29 wet ALD HfO 2 is deposited at 300 C in an ASM Polygon 8300 reactor. The samples a)…”

Atomic Layer Deposition of High Quality HfO2Using In-Situ Formed Hydrophilic Oxide as an Interfacial Layer

“…and R. L. Puurunen, etc. explored the ALD nucleation of ZrO 2 , Al 2 O 3 , TiO 2 and HfO 2 on Si surface, and proved that comparing to nucleation on SiO 2 surface, nucleation on H-terminated Si surface is characterized by non-uniformity, island-like morphology, poor metal oxide qualities, and metal diffusion at high temperature.4-11 Plus, underlying SiO 2 would grow at the Si/metal oxide interface at moderate temperature, which is harmful to the scaling of MOS devices.12,13 This has been proved by infrared spectroscopy.14 There are also researches on nucleation of HfO 2 on Si (110) and Si (111), 15 and Ge surface, 16,17 which is a potential substrate material with high mobility. L. In this work, we report an ALD-based in-situ formation of SiO 2 interfacial layer using one cycle of ozone and water.…”

“…14 There are also researches on nucleation of HfO 2 on Si (110) and Si (111), 15 and Ge surface, 16,17 which is a potential substrate material with high mobility. L. In this work, we report an ALD-based in-situ formation of SiO 2 interfacial layer using one cycle of ozone and water.…”