| AVS 54th International Symposium | |
| Electronic Materials and Processing | Friday Sessions |
| Session EM-FrM |
| Session: | Hf-based Dielectrics and Their Interfaces |
| Presenter: | M. Sawkar, University of California at Los Angeles |
| Authors: | J.R. Liu, University of California at Los Angeles R.M. Martin, University of California at Los Angeles M. Sawkar, University of California at Los Angeles J.P. Chang, University of California at Los Angeles |
| Correspondent: | Click to Email |
Pseudo-binary (HfO2)x(SiO2)1-x has attracted much attention due to the interesting possibility of combining the high breakdown field of SiO2 (Eg = 9 eV) and high dielectric constant (22~25) of HfO2 in a complex material to keep a relatively high dielectric constant and a low leakage current.1,2 In this work, (HfO2)x(SiO2)1-x composite films were deposited from hafnium tetra-tert-butoxides (HTB) and tetraethylorthosilicate (TEOS) precursors by using an plasma-enhanced atomic layer deposition (PEALD) process. The film thickness increased almost linearly with increasing number of precursor-oxygen plasma cycles. An optimal control over the final composition was achieved by setting the deposition cycles of HfO2 and SiO2. Fourier Transform Infrared spectroscopy (FTIR) and x-ray photoelectron spectroscopy (XPS) analysis showed that the composite films were fully oxidized. The Si-O-Hf bonds were formed in the PEALD deposited composite films. The band gap determined from the XPS O 1s plasmon loss spectrum increased from 5.6 to 5.98 eV with increasing the Si content in the as-deposited films, and it increased slightly after the composite films were annealed at 600 and 900oC, respectively. Time-of-flight static secondary ion mass spectrometry (TOF-SSIMS) depth profiles showed that Hf is almost uniformly distributed throughout the films, and Hf and O exhibited a sharp decay at the Si interfacial substrate. Some Hf presence at the interface with Si could be attributed to ion beam-induced mixing of Hf into the interfacial layer. The low carbon content in these films, which is confirmed by XPS, resulted from the ambient surface contamination. The as-deposited and annealed films at 900oC were determined to be amorphous by x-ray diffraction (XRD), suggesting that the introduction of SiO2 into HfO2 matrix prevented crystallization and kept the film amorphous at high temperature. The as-deposited (HfO2)x(SiO2)1-x composite films showed superior electrical properties, including dielectric constants from 5.3 to 11.5 and leakage current density several orders of magnitude lower than that of SiO2 at the same equivalent oxide thickness.
1 R. M. Wallace and G. Wilk, MRS Bulletin, 192, 27 (2002).
2 R. Puthenkovilakam, M. Sawkar, and J. P. Chang, Appl. Phys. Lett., 202902, 86 (2005).