Measurement of the silicon dioxide concentration in hafnium silicate gate dielectrics with a total reflection X-ray fluorescence spectroscopy

Abstract

As complementary metal oxide semiconductor devices continue to scale along the rapid pace of Moore’s law, gate dielectric materials with significantly higher dielectric constant (k=10–25) are being evaluated as replacements for conventional silicon dioxide, SiO2 (k=3.9), and silicon oxynitride. This allows for the introduction of a physically thicker film with lower leakage current and with capacitance equivalent to a thinner (1.0 nm and below) SiO2 layer (Schlom and Haeni, 2002; Wilk et al., 2001; Kingon et al., 2001). Although binary metal oxide films such as HfO2 and ZrO2 exhibit higher permittivity than their corresponding silicates and aluminates, alloyed with various molecular percents of SiO2 or Al2O3, respectively, they are compromised by lower onset of crystallization temperature which contributes a higher degree of interfacial microroughness and increased gate leakage current due to dislocations and oxygen vacancies generated along grain boundaries. Accordingly, development of hafnium silicate has been the subject of intense investigation as an advanced gate dielectric thin film designed to meet the device manufacturing requirements of thermal stability in direct contact with substrate silicon and metal gate electrode materials. In this paper, we present results corresponding to the utilization of total reflection X-ray fluorescence spectroscopy (TXRF) as a quick, accurate, nondestructive technique for hafnium silicate composition determination based on detection of the Hf:Si ratio of (HfO2)x(SiO2)1−x, where x varies over the range 0.2–1.0.