Deposition of HfO[sub 2] Thin Films in HfI[sub 4]-Based Processes

Abstract

This study describes deposition of HfO 2 thin films by chemical vapor deposition ͑CVD͒ and atomic layer deposition ͑ALD͒ using HfI 4 as the metal precursor. The layer-by-layer growth was also studied in real time with a quartz crystal microbalance. In ALD, the deposition rate was independent of the growth temperature, whereas in CVD, an exponential rate increase was observed. Monoclinic HfO 2 was deposited on MgO and poly-Si substrates in a wide temperature range, and the choice of substrate had a strong influence on the orientation of the films. Epitaxial growth of HfO 2 was observed on MgO͑001͒ substrates at 400-500°C in the ALD process and at 500-600°C in the CVD process. The electrical characterization showed that the crystallinity of the films had a stronger influence on the dielectric constant than did the film thickness.

Characterization of HfO2 films deposited on 4H-SiC by atomic layer deposition

“…13 The well-known ALD process of HfO 2 is also described elsewhere. 10 Two different deposition series of HfO 2 were done. The goal of the first run was to obtain the deposition parameters on Si samples while the goal of the second run was to test the dielectric performance on SiC samples and diodes.…”

“…10 Although the peak visible at a 2⌰ value of 34.6°can be assigned to the ͗020͘ plane of the monoclinic phase ͑marked with an M in Fig. 3͒, 14 the other much more pronounced peak at a 2⌰ value of 44.8°w ould fit best for a ͗211͘ plane of the orthorhombic phase ͑marked with an O in Fig.…”

“…8,9 Publications that describe films obtained from iodine and water vapor between 200 and 300°C, as in our experiments, show in the range of 10-20 and a critical breakdown field in the range of 2.5-7 MV/cm. 8,10 Due to the relatively low HfO 2 band gap of 6 eV 11 compared to 4H-SiC, electron injection from SiC into the dielectric may occur. One suggestion to prevent this is to introduce a thin SiO 2 layer as a buffer between the SiC and the high insulator in order to provide large enough band offsets for the conduction ͑2.7 eV͒ and valence ͑2.9 eV͒ bands, and also to reduce the density of SiC interface states.…”

CVD of Epitaxial SnO2 Films by the SnI4/O2 Precursor Combination

“…Previously, metal iodides in combination with O 2 have been used to deposit the corresponding metal oxides by CVD, e.g., TiI 4 , [15] BiI 3 , [16] TaI 5 , [17] ZrI 4 , [18] and HfI 4 . [19] It has been shown, for these metal iodide processes, that the resulting films have no, or very low, contamination from the precursor compared to CVD processes based on metal±organic precursors or metal chlorides. This is due to the fact that many of these metals form interstitial carbides, and that metal iodides are less thermodynamically stable than the corresponding metal chlorides and hence decompose more easily at the surface.…”

ALD of Hafnium Dioxide Thin Films Using the New Alkoxide Precursor Hafnium 3-Methyl-3-pentoxide, Hf(mp)4

“…A number of hafnium compounds have been studied, however, there still exist many problems in their use as ALD precursors for HfO 2 thin films. For instance, hafnium halides, HfCl 4 [7][8][9] and HfI 4 , [8][9][10] are solids with high melting points. Although they showed excellent self-limiting ALD growth characteristics, the use of these precursors results in halogen contamination, [7] which can cause serious problems in microelectronic applications.…”