Growth of high-k silicon oxynitride thin films by means of a pulsed laser deposition-atomic nitrogen plasma source hybrid system for gate dielectric applications

Abstract

High-k silicon oxynitride (SiOxNy) thin films have been successfully grown by means of a hybrid deposition process based on the combination of the pulsed laser deposition (PLD) plume of silicon species in an oxygen background together with a remote plasma-based atomic nitrogen source (ANS). This pulsed laser deposition-atomic nitrogen source (PLD-ANS) hybrid method is found to be highly effective for further nitrogen incorporation into SiOxNy films. At a laser intensity of 2.5×108 W/cm2 and a deposition temperature (Td) of 300 °C, it was shown that the N content of the SiOxNy films could be controlled over a concentration range as wide as 0–35 at. %, by controlling the partial pressure ratio of N to O2 in the deposition chamber. The structural and dielectric properties of the PLD-ANS SiOxNy films were systematically investigated as a function of their N content. Microstructural analyses revealed that the increasing incorporation of N into the SiOxNy films occurs through the formation of Si–N bonds to the detriment of Si–O ones. Both the dielectric constant (k) and the breakdown field of the SiOxNy thin films are found to increase significantly with N content. At the highest N content (35 at. %), the PLD-ANS films exhibit a high k-value of about 9.5 and a breakdown field as high as 19 MV/cm. It appears that Poole–Frenkel emission with compensation is the most predominant conduction mechanism in the SiOxNy films. By enabling control of the N content during deposition, the PLD-ANS approach provides the means to achieve desirable N profile engineering in the SiOxNy dielectric thin films.