Comparison of Chemical Vapor Deposited Hafnium Dioxide and Silicon Doped Hafnium Dioxide using either O 2 , N 2 O, H 2 O
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Comparison of Chemical Vapor Deposited Hafnium Dioxide and Silicon Doped Hafnium Dioxide using either O2, N2O, H2O, O2 plasma, or N2O plasma, and Hf (IV) t-butoxide Harish B. Bhandari, Ping Chen, and Tonya M. Klein Department of Chemical Engineering, The University of Alabama, Tuscaloosa, AL 35487, USA
ABSTRACT Hafnium oxide (HfO2) and silicon containing hafnium oxide (HfSixOy) thin films were deposited by thermal and plasma enhanced chemical vapor deposition (PECVD) using Hf (IV) tbutoxide and either O2, N2O, H2O, O2 plasma or N2O plasma as an oxygen source. Silane, 2% in He, was added to the reactant gas mixture to incorporate Si. Deposition rate and composition dependence on substrate temperature was studied and the deposited films were annealed in air for 30 min at 1100ºC to observe changes in crystallinity and composition. Silicon incorporation was higher for H2O deposited HfSixOy films (5 at.%) than O2 and N2O deposited films (2 at.%) and had a lower deposition rate. Arrhenius plots reveal a non-simplistic reaction scheme since higher temperatures result in lower deposition rates due to precursor desorption. XRD indicate that as-deposited films using H2O are amorphous while O2 and N2O deposited films are microcrystalline with a monoclinic phase.
INTRODUCTION Rapid downscaling of complimentary metal oxide semiconductor (CMOS) devices has resulted in the development of alternative high dielectric materials to replace SiO2 as the gate insulator [1]. Among the metal oxides being investigated, hafnium dioxide (k~25) and hafnium silicate (k~ 8-15) have received considerable attention owing to their high dielectric constants, low interface state density, and high thermal stability [1-3]. Plasma enhanced metal organic chemical vapor deposition (PECVD) and atomic layer deposition (ALD) are attractive alternatives to physical vapor deposited (PVD) high dielectric deposited films because of the ability to control the deposition chemistry as well the conformality and thickness uniformity [47]. To achieve gate oxides of high reliability it is necessary to identify optimal precursors and deposition conditions. HfO2 and HfSixOy films were deposited using plasma and thermal CVD using either an O2 plasma, N2O plasma, O2, N2O or H2O at substrate temperatures of 275 ºC, 360 ºC and 425 ºC. XPS, XRD and ellipsometry were used to characterize the films before and after annealing to 1100ºC in air.
EXPERIMENT N-type, antimony doped, 0.005-0.03 Ω-cm resistivity, Si (100) substrates were dipped in 50:1 HF buffered oxide etchant solution for 2 mins before the deposition process to remove native oxide. Deposition was carried out in a cold wall plasma enhanced chemical vapor
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deposition reactor with base and deposition pressure of 5*10-7 Torr and 1 Torr respectively. The substrates were introduced through a load-lock chamber and placed on a heater stage in the PECVD reactor. The substrates were heated from the bottom using six 500 W halogen bulbs controlled with a PID controller and a type k thermocouple. The hafnium m
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