Physical and electrical properties of MOCVD and ALD deposited HfZrO4 gate dielectrics for 32nm CMOS high performance logic SOI technologies

Future scaling of complementary metal oxide semiconductor (CMOS) technology requires high-k (HK) dielectrics with metal gate (MG) electrodes to realize higher gate capacitances and low gate leakage currents [1]. During the last decade the semiconductor industry has spent tremendous effort to find the right material. Hafnium-based dielectrics and particularly HfO2 are considered to be the most promising candidates to replace SiON in high volume manufacturing due to their relatively high dielectric constants, large band gap and conduction band offset to Si and their thermodynamic stability with Si [2-4]. However, compared to SiO2, HfO2 dielectrics suffer from threshold voltage instabilities, mobility degradation, charge trapping as well as reliability degradation [5,6]. Recently HfZrO4 has been shown to be a superior gate dielectric to HfO2 [7-11]. Addition of ZrO2 to HfO2 forming HfZrO4 helps to partially stabilize tetragonal phase being associated with higher kand lower CET values [7]. Besides smaller and more uniform grains, more uniform film quality, tighter leakage distribution, less charge trapping, lower CV hysteresis, lower Dit, higher transconductance and drive currents, reduced SILC and longer product reliability lifetimes have been reported among other things for HfZrO4 compared with HfO2 [7-11]. Simultaneously disadvantages like smaller band gap (~0,4eV) and lower conduction band offsets resulting in increased leakage have been presented as well [7]. Up to now atomic layer deposition (ALD) [7-10] as well as physical vapor deposition (PVD) [11] have been explored to form the HfZrO4 layers. As metal-organic chemical vapor deposition (MOCVD) stands out due to excellent manufacturability and high throughputs, we investigate HfZrO4 dielectrics deposited with MOCVD as well as ALD as high-k gate dielectric for 32nm high performance logic SOI CMOS devices in this work. The physical properties of the HfZrO4 films have been analyzed in detail by atom probe tomography [12,13], Xray photoelectron spectroscopy, Rutherford backscattering spectrometry, time-of-flight secondary ion mass spectrometry, transmission electron microscopy, reflectometry, atomic force microscopy, variable angle spectroscopic ellipsometry as well as high temperature grazing incidence X-ray diffraction. In addition electrical parameters such as gate leakage current, capacitance equivalent thickness, threshold voltage, interface trap density (charge pumping) and performance as well as reliability data have been taken into account to directly compare both deposition methods. All parameters indicate a comparable behavior for MOCVD and ALD. Therefore MOCVD is demonstrated to be a promising alternative to ALD in high volume manufacturing in this work.