Formation of ZrO2 thin films by thermal oxidation of sputtered Zr on Si and SiC substrates
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Date
2009
Authors
Tedi Kurniawan
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Abstract
ZrO2 thin films for gate dielectric application has been formed on Si and SiC
substrates using a combination of metal sputtering and thermal oxidation process.
Effects of oxidation temperature (500-800oC), oxidation time (5-60 min) and sputtering
time (30-120 s) have been studied on p- or n-type Si substrate. Meanwhile, effects of
annealing temperature (600-900o) in Ar ambient were studied on n-type 4H-SiC
substrate. Sputtering process has been conducted by regulating base pressure, working
pressure and DC power at 4.4x10-5 Torr, 3~6x10-3 Torr and 250 Watt. Meanwhile, for
oxidation and annealing process, Ar and O2 flow rate were maintained at 150 ml/min.
The effects of oxidation temperature and oxidation time have been studied by oxidizing
15-s sputtered Zr on p-type Si. High resolution transmission electron microscopy
(HRTEM) and Fourier transform infrared spectroscopy (FTIR) analyses showed that 3.5
nm ZrO2 and 3.5 nm interfacial layers (IL) in a mixture of SiOx and ZrxSiyOz were
formed from oxidation at 500oC in 60 min. Furthermore, time-of-flight secondary ion
mass spectroscopy (ToF-SIMS) profiles show that ZrxSiyOz formed after 15 min
oxidation time and interface of ZrO2/IL contain Si-rich composition. Improvement in
leakage current density (J), voltage breakdown (VB) and electric field breakdown (EB)
properties have been shown by 15-60 min oxidation samples, with the optimum value
has been reached by 30-min oxidized sample. Oxide dielectric constant (k) from this
work ranges from 4.2 to 5.3. Observation on the effects of sputtering time on n-type Si
was conducted after oxidation at 500oC in 15 min. Blistering phenomenon was observed
at 90 and 120-s sputtered samples, while 60-s sputtered Zr has better electrical
properties compared with the others. k value from this work ranges from 9.4 to 18.
Observation on the effects of annealing temperature on n-type 4H-SiC substrate has
been conducted after 60-s sputtered Zr oxidized at 500oC in 15 min. Annealing process
has reduced J as high as 2 order of magnitude. On the other hand, VB and EB have also
been reduced. k value from this work ranges from 22 to 80.
Description
Master
Keywords
Materials & Minerals Resources Engineering , Thin films , Thermal oxidation