Identification of annealing temperature for high-$\kappa$-based gate oxides using differential scanning calorimetry

TL;DR

This study uses Differential Scanning Calorimetry to identify optimal annealing temperatures for high-$ppa$ dielectric films, revealing that device degradation is linked to Hf-Silicate formation rather than crystallization.

Contribution

It introduces a thermal analysis approach to determine annealing temperature ranges that improve high-$ppa$ dielectric film performance in MOS technology.

Findings

Crystallization occurs at ~590°C, but does not cause device degradation.

Hf-Silicate formation begins at ~717°C, leading to device degradation.

Optimal annealing temperature avoids Hf-Silicate formation for better device stability.

Abstract

This article identifies the process of crystallization of thin high-$\kappa$ dielectric films and an optimal range of annealing temperature in the field of high-$\kappa$ dielectric-based metal-oxide-semiconductor (MOS) technology for its improved electrical performances. Differential Scanning Calorimetry (DSC) technique is employed to understand the thermal behaviour of thin high-$\kappa$ dielectric films of HfO$_2$, deposited by rf sputtering, on Si. The exothermic trends of the DSC signal and Grazing Incidence X-ray diffraction (GIXRD) data indicate an amorphous to crystalline transition in the high-$\kappa$ film at higher temperature. The enthalpy-temperature variation shows a glass temperature (T$_g$) at $\sim$ 590 $^o$C beyond which an amorphous to m-HfO$_2$ crystalline transition takes place. Further, the Hf-Silicate formation, observed in DSC measurement and corroborated by Fourier transformed Infrared Spectroscopy (FT-IR) studies, indicates that the process of formation of Hf-Silicate begins at $\sim$ 717 $^oC$. High-frequency (HF) capacitance-voltage $(C-V)$ and current density - voltage $(J-V)$ characteristics establish that the crystallization of the film is not the root cause of degradation of the electrical properties of the high-$\kappa$-based MOS devices, rather the device degrades due to formation of interfacial Hf-Silicate.