Direct chemical vapor deposition growth of tunable HfSiON films by a new precursor combination
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Hafnium silicon oxynitride (HfSiON) films were deposited on 200-mm silicon substrates by low-pressure chemical vapor deposition (LPCVD) from a combination of trisilylamine (TSA) and tetrakis(diethylamido)hafnium(IV) (TDEAH) in the temperature range 450 to 575 °C. A highly volatile and carbon-free silicon precursor TSA was used to deposit HfSiON films for the first time. HfSiON films were deposited in a single step with no need of a post-treatment process for nitrogen incorporation. The film composition was tuned in a wide compositional range, and high growth rates were achieved. NH3 was found to have profound effects on film growth rate, metal ratio (Si% or Hf%), nitrogen incorporation, and carbon residue in the films.
I. INTRODUCTION
High- films will be used to replace SiO2/SiON materials in sub-45 nm nodes as gate dielectrics in semiconductor manufacturing technology. Hafnium silicate has been identified as a promising high- candidate.1,2 In recent years, various types of amido precursors have been used as both Hf and Si sources in chemical vapor deposition (CVD) and atomic layer deposition (ALD) to grow HfSiO (hafnium silicate) or HfO2 films.3 For example, TDMAS [Si(NMe2)4] and TDEAH [Hf(NEt2)4] were used with O2 to deposit HfSiO films with 35 to 60 at.% Si.4 Various Si sources, notably Si(NCO)4, TriDEAS [HSi(NEt 2 ) 3 ], and tetraethylorthosilicate (TEOS), combined with TDEAH, have been shown to incorporate significant levels of carbon that strongly depend on the Si source.5 Hf(OSiButMe2)4(Et2NH) has been recently demonstrated as a single-source precursor providing Si and Hf in the same molecule, but resulting in only around 10% Si; the Si content can be increased to about 18% by use of two separated precursors TDMAH and ButMe2SiOH.6 A variety of other precursors were also studied for the deposition of HfSiO or HfO2 films having different compositions, structures, and properties.7–18 In CVD and ALD processes using such precursors, limited control over film composition has been demonstrated. For example, the combination of TDEAH and TriDEAS yields 20% to 35% Si content {defined as atomic ratio (Si)/[(Si) + (Hf)] × 100%} in films,8,9 that of
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Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2007.0119 1024 J. Mater. Res., Vol. 22, No. 4, Apr 2007 http://journals.cambridge.org Downloaded: 17 Mar 2015
TDMAS and TDEAH yielding up to 35% to 60% Si,4 that of Hf(NMe2)4 and BuMe2SiOH producing 40% Si,19 or that of Si(NC4H8)4 and TDEAH achieving Si up to 70% Si.11 Most of the above Si sources for HfSiO films are liquids at room temperature and are delivered either by bubbling or flash vaporization. Studies have shown that incorporation of nitrogen into HfSiO films can suppress the crystallization of HfO2 in films,20 achieve lower leakage,21 and increase resistance to dopant21 and oxygen penetration during annealing.22 However, without using nitrogen-containing sources such as NH3 or NO, Hf and Si amido precursors usually do not provide enough N incorporation in as-
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