HfO₂ and Hf_1–xSi_xO₂ Thin Films Grown by Metal‐Organic CVD Using Tetrakis(diethylamido)hafnium

Abstract

Pure tetrakis(diethylamido)hafnium (Hf(NEt 2 ) 4 ) has been synthesized as a precursor for depositing Hf-compound films. Hf(NEt 2 ) 4 is liquid at room temperature and has sufficient vapor pressure (0.1 Torr at 80°C) for the CVD of hafnium dioxide (HfO 2 ) and hafnium silicate (Hf 1-x Si x O 2 ). It is stable, not pyrophoric in air, and reacts violently with water. HfO 2 films were grown by low-pressure (LP)CVD using a Hf(NEt 2 ) 4 /O 2 gas mixture. Although nitrogen atoms tended to remain in the grown films, stoichiometric polycrystalline HfO 2 films with few residual impurities and good step coverage were deposited. By introducing a silicon precursor (such as tris(diethylamino)silane ((NEt 2 ) 3 SiH), tetraisocyanatosilane (Si(NCO) 4 ), or tetraethoxysilane (Si(OEt) 4 )) during HfO 2 LPCVD, amorphous hafnium silicate films were obtained. The amount of residual carbon and nitrogen in the Hf 1-x Si x O 2 was affected by the type of Si precursor used. High-purity Hf 1-x Si x O 2 films were deposited when Si(OEt) 4 was used as the silicon source.

Growth of HfO2 by Liquid Injection MOCVD and ALD Using New Hafnium‐Cyclopentadienyl Precursors

“…Clearer differences between the precursors were seen in the growth rates of HfO 2 Figure 3. For self-limiting growth in ALD, the oxide growth per cycle would be expected to increase with increasing injected precursor volume until surface-saturation is achieved, [41] at which point the growth rate should become constant.…”

“…Both compounds were synthesized by the reaction of [(MeCp) 2 HfMe 2 ] and an excess of the appropriate alcohol; 2-propanol and 1-methoxy-2-methyl-2-propanol. The complexes were fully characterized by elemental microanalysis, 1 H and 13 C{ 1 H} NMR spectroscopy, and IR spectroscopy.…”

“…Although the nitrate complex [Hf(NO 3 ) 4 ] has been used for the MOCVD of high-purity HfO 2 films, [10,11] concerns about the stability of anhydrous metal nitrates may restrict its application. Since the initial studies by Bastianini et al [12] 4 ] have been extensively investigated, [2,[13][14][15][16] but they are highly airand moisture-sensitive, making them difficult to handle and use, especially in solution-based liquid injection MOCVD applications. [17] The Hf alkoxides, [Hf(O i Pr) 4 ], [18] and more frequently [Hf(O t Bu) 4 ] [19][20][21][22] have also been used widely in MOCVD, but these four-coordinate unsaturated complexes are highly reactive and moisture-sensitive, with a short shelf-life and a tendency to block the MOCVD reactor inlet lines.…”

“…and has been used for the MOCVD of HfO 2 in the absence of an added oxygen source. [27] Organometallic precursors have been used less frequently than alkoxides or alkylamides for the MOCVD of Group IVB oxides, although [Cp 2 ZrMe 2 ] and [(MeCp) 2 ZrMe 2 ] have been investigated, and gave ZrO 2 films with varying levels of carbon contamination, depending on growth conditions. [28] A variety of precursors have also been investigated for the ALD of HfO 2 .…”

“…[1][2][3][4] This is due to the relatively high permittivity of HfO 2 (k = 16-19 for the monoclinic phase) compared to SiO 2 (k~3.9), its high bandgap (5.7 eV), high band offset, and high thermal stability on Si. HfO 2 is also a promising high-k dielectric oxide for use in metal-insulator-metal (MIM) capacitor applications.…”