Investigation of Crystallization Processes from Hafnium Silicate Powders Prepared from an Oxychloride Sol-Gel

• Published in: Journal of the American Ceramic Society 2012-12, Vol.95 (12), p.3985-3991
• Main Authors: McGilvery, Catriona M., De Gendt, Stefan, Payzant, E. Andrew, MacKenzie, Maureen, Craven, Alan J., McComb, David W.
• Format: Article
• Language: English
• Subjects: Amorphous materials; CMOS; Crystallization; Grain boundaries; Hafnium; Hafnium oxide; Reduction; Silicates; Silicon dioxide; Strain; Temperature effects; Transmission electron microscopy
• ISSN: 0002-7820; 1551-2916
• DOI: 10.1111/j.1551-2916.2012.05408.x

Hafnium oxide and silicate materials are now incorporated into working CMOS devices; however, the crystallization mechanism is still poorly understood. In particular, addition of SiO2 to HfO2 has been shown to increase the crystallization temperature of HfO2, hence, allowing it to remain amorphous under current processing conditions. Building on earlier study, we herein, investigate bulk HfxSi1−xO2 samples to determine the effect of SiO2 on the crystallization pathway. Techniques, such as XRD, HTXRD, thermal analysis techniques and TEM are used. It is found that the addition of SiO2 has very little affect on the crystallization path at temperatures below 900°C, but at higher temperatures, a second t‐HfO2 phase nucleates and is stabilized due to the strain of the surrounding amorphous SiO2 material. With an increase in SiO2 content, the temperature at which this nucleation and stabilization occurs is increased. The effect of strain has implications for inhibiting the crystallization of the high‐k layer, reduction of grain boundaries and hence diffusion, reduction of formation of interface layers and the possibility of stabilizing t‐HfO2 rather than m‐HfO2, hence, increasing the dielectric of the layer.