Deposition of HfO2, Gd2O3 and PrOx by Liquid Injection ALD Techniques

Abstract

Thin films of hafnium oxide (HfO 2 ), gadolinium oxide (Gd 2 O 3 ), and praseodymium oxide (PrO x ) have been deposited by liquid injection atomic layer deposition (ALD) and for comparison, have also been deposited by ªthermalº metal-organic (MO) CVD using the same reactor. The ALD-grown films were deposited on Si(100) over a range of substrate temperatures (150±450 C) using alternate pulses of [Hf(mmp) 4 ], [Gd(mmp) 3 ], or [Pr(mmp) 3 ] (mmp = OCMe 2 CH 2 OMe) and water vapor. X-ray diffraction (XRD) analysis showed that as-grown films of HfO 2 were amorphous, but these crystallized into the monoclinic phase after annealing in air at 800 C. XRD analysis showed that as-grown Gd 2 O 3 and PrO x films had some degree of crystallinity. Residual carbon (0.8±3.3 at.-%) was detected in the HfO 2 and PrO x films by Auger electron spectroscopy (AES), but not in the Gd 2 O 3 films. The self-limiting behavior of the precursors was investigated at 225 C by varying the volume of precursor injected during each ALD cycle and, in each case, oxide growth was not fully self-limiting. We propose a mechanism for this involving b-hydride elimination of the mmp group, and also propose some general mechanistic principles which may influence the growth of oxides by ALD using other precursors.

Structural and optical properties of lanthanide oxides grown by atomic layer deposition (Ln = Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb)

“…For the 15 lowest deposition temperatures, 200-225 °C, the spectra do not exhibit any distinct peaks. For Nd, Ho, Er and Yb, the first clear set of absorption peaks at low temperature changes to a different set at 300, 300, 275 and 250 °C, respectively.…”

“…This is reasonable since the absorptions originate from forbidden f-f transitions and depend on the local environment around the lanthanide cations. The optical absorption spectra of these films are thus a good probe for the local symmetry around the 15 lanthanide ions. However, the absorptions are weak so high sensitive measurements are required.…”

“…Optical absorption measurements were done on a Shimadzu UV-3600 photospectrometer. SEM analysis was performed on a FEI 15 Nova NanoSEM 650.…”

“…Among the lanthanide oxides and precursors studied in this work, Nd 9 and Er 10 have previously 30 been investigated in the temperature range 200 -450 °C, Yb 11 at 250 -400 °C, while for Sm, Eu, Dy, Ho, Tm 8 , and Tb 12 only data at 300 °C are available. The use of alternative precursors has been investigated [13][14][15][16][17][18][19][20] . Ternary oxides and nanolaminates containing lanthanides have been deposited both by using the β- 35 diketonate chelates Ln(thd) 3 (Hthd = 2,2,6,6-tetramethyl-3,5-heptanedione) 9,12,[21][22][23][24][25][26] and alternative [27][28][29] precursors.…”

MOCVD and ALD of High‐k Dielectric Oxides Using Alkoxide Precursors

“…[100] As Gd 2 O 3 is the only stable stoichiometry of gadolinium oxide, the O/Gd ratios of 1.7-2.0 indicate that the films contain excess oxygen (expected O:Gd ratio in Gd 2 O 3 = 1.5). Significantly, carbon was absent from all of the films at the estimated AES detection limit of < 0.5 at.-%.…”