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

摘要

Hafnium oxide and silicate materials are now incorporated into working CMOS devices; however, the crystallization mechanism is still poorly understood. In particular, addition of SiO_2 to HfO_2 has been shown to increase the crystallization temperature of HfO_2, hence, allowing it to remain amorphous under current processing conditions. Building on earlier study, we herein, investigate bulk Hf_xSi_(1-x)O_2 samples to determine the effect of SiO_2 on the crystallization pathway. Techniques, such as XRD, HTXRD, thermal analysis techniques and TEM are used. It is found that the addition of SiO_2 has very little affect on the crystallization path at temperatures below 900℃, but at higher temperatures, a second f-Hf'O_2 phase nucleates and is stabilized due to the strain of the surrounding amorphous SiO_2 material. With an increase in SiO_2 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-HfO_2 rather than m-HfO_2, hence, increasing the dielectric of the layer.