Thermal stabilization of device quality films deposited at low temperatures

Abstract

The effects of postdeposition furnace annealing, at temperatures typical of metal–oxide semiconductor (MOS) fabrication processes, on gate oxides formed by remote plasma-enhanced chemical vapor deposition (remote PECVD) are discussed. SiO2 films were prepared by (1) remote PECVD at substrate temperatures of 200 and 400 °C, and (2) by thermal oxidation of silicon at temperatures from 850 to 1150 °C. Postdeposition thermal processing was carried out in industrial-type diffusion furnaces in both N2/O2 and N2/H2 ambients over a temperature range of 400–1050 °C. Film properties were studied by infrared spectroscopy, ellipsometry, and by measurements of capacitance voltage (C–V) characteristics in MOS device structures. Postdeposition thermal processing at temperatures of 400 °C and above was shown to modify both the structure and electrical properties of deposited SiO2 films. It is shown that changes in the as-deposited film properties occur by two different relaxation mechanisms, one of which is operative in the temperature range up to 750 °C and the other from 750 to 1050 °C, and both of which are different from the viscoelastic relaxation process observed in thermally grown SiO2.

Physical properties of high pressure reactively sputtered hafnium oxide

“…We attribute this band to the formation of an interfacial SiO 2 layer between the HfO 2 film and the Si-substrate during the deposition. The presence of silicon suboxides near the Si/SiO 2 interface [23] and/or the fact that Hf-O bonds are longer than the Si-O bonds [24] may be responsible for the strain in this layer. A minimum in the area of this band was observed for the films deposited at 1.2 mbar, suggesting a minimum in the thickness of the SiO 2 interfacial layer.…”

Hafnium oxide thin films deposited by high pressure reactive sputtering in atmosphere formed with different Ar/O2 ratios

“…In this case, the maximum shifts to 1072 cm À1 . The shift to lower wave numbers with respect to the maximum of thermally grown SiO 2 (1074.5 cm À1 ) is normally related to strain in the SiO 2 film [5]. The polycrystalline structure of the HfO 2 films deposited with oxygen-containing atmosphere may be responsible of the higher strain in the SiO 2 interfacial layer [6].…”

Electrical properties of high-pressure reactive sputtered thin hafnium oxide high-kgate dielectrics

“…So, FTIR measurements can be used to check the crystalline structure of HfO 2 films. Figure 2 also shows an absorption band between 1200 and 1000 cm −1 characteristic of an asymmetric stretching vibration of the SiO 4 unit [24]. We attribute these bands to the formation of an interfacial SiO 2 layer between the HfO 2 film and the Si substrate during the deposition.…”