Nitridation of Hafnium Silicate Thin Films

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D7.5.1

Nitridation of Hafnium Silicate Thin Films Hood Chatham, Yoshi Senzaki, Jeff Bailey, and Wesley Nieveen1 Aviza Technology, Inc., 440 Kings Village Road, Scotts Valley, CA 95066, U.S.A. 1 Charles Evans and Associates/Evans Analytical Group, 810 Kifer Road, Sunnyvale, CA, 94086, U.S.A.

ABSTRACT

We discuss the nitridation of ALD-deposited hafnium silicate films by exposure to atomic nitrogen generated in a remote nitrogen plasma. Nitrogen concentration [N] as measured by Xray photoelectron spectroscopy (XPS) is determined as a function of the nitridation temperature and other process conditions. Nitrogen concentrations up to 13.7 atomic % were achieved.

INTRODUCTION

High quality gate dielectrics with higher dielectric constant to replace SiO2 are required to meet future device requirements as the integrated circuit device scale decreases. Conventional SiO2 gate dielectrics suffer from leakage and reliability deficiencies as the silicon oxide thickness decreases below 18 Å. Acceptable high-k gate dielectric materials must be thermally stable with Si and provide good electrical properties. Metal oxides such as HfO2, ZrO2, and the silicate form of these materials have been studied as promising alternatives to SiO2 [1], with the hafnium-based materials being the leading candidates. HfSiON is of particular interest as it remains amorphous and shows no leakage current degradation or increase in EOT (equivalent oxide thickness) even after annealing at 1100°C in an inert gas [2]. Atomic layer deposition (ALD) has been previously discussed as a method of depositing high-k materials. We have developed an atomic layer deposition (ALD)-based HfxSi1-xO2 (x = 0.1 to 1) process using volatile liquid precursors at temperatures ≤ 400°C [3]. The use of ozone allows us to process at low temperatures and provides good electrical properties [4]. Post deposition exposure of these films to atomic nitrogen produced in a remote nitrogen plasma results in high levels of nitrogen incorporation at low nitridation temperatures. Previously, we reported achieving 18.7 atomic % N by post deposition NH3 nitridation at 800°C [3]. In this paper, we discuss the nitridation of ALD-deposited hafnium silicate films by remote nitrogen plasma nitridation. Nitrogen concentration [N] as measured by X-ray photoelectron spectroscopy (XPS) is determined as a function of the nitridation temperature and other process conditions. We report the achievement of 13.7 atomic % N by post deposition exposure of HfSiO films to atomic N from a remote nitrogen plasma at 350 and 450°C wafer temperature.

D7.5.2

EXPERIMENTAL An AVIZA Technology Pantheon system was used to deposit thin Hf0.5Si0.5O2 high-k films onto 200 mm diameter p-type Si (100) wafers. Volatile metal-organic liquid precursors were used for the hafnium silicate film deposition. Ozone was used as an oxygen source for the metal oxide films. Ellipsometry (49 points with 3 mm edge exclusion) was used to measure film thickness. Film composition was determined by Rutherford backscattering spectroscopy.