TY - JOUR
T1 - Seamless fill of deep trenches by chemical vapor deposition
T2 - Use of a molecular growth inhibitor to eliminate pinch-off
AU - Talukdar, Tushar K.
AU - Girolami, Gregory S.
AU - Abelson, John R.
N1 - Funding Information:
The authors gratefully acknowledge support from SRC (Contract No. 2015-IN-2607); Sumeng Liu and Brian Trinh in the group of G.S.G. for precursor supply. G.S.G. acknowledges support from the National Science Foundation (NSF) (Grant No. CHE 16-65191). The authors also thank Bart van Schravendijk of Novellus Systems (now Lam Research Corporation) for supplying the SiN microtrench substrates as part of an earlier project. The ex situ materials characterization was carried out in the Center for Microanalysis of Materials at the Frederick Seitz Materials Research Laboratory, University of Illinois.
PY - 2019/3/1
Y1 - 2019/3/1
N2 - Attempts to fill deep trenches by chemical vapor deposition often result in a "bread-loaf" profile, an overhang near the trench opening that arises whenever the growth rate is slightly higher near the opening than deeper in the feature. Continued growth leads to premature pinch-off at the opening, which leaves an undesirable void or seam along the centerline. Bread-loaf profiles can form even under superconformal growth conditions, as the authors recently found for the growth of HfO 2 from the precursor tetrakis(dimethylamino)hafnium and a forward-directed flux of H 2 O coreactant. The current paper describes a method that can reduce or eliminate the bread-loaf problem: addition of an isotropic flow of a reactant that inhibits growth near the trench opening but leaves the growth rate unchanged deeper in the trench. A Markov chain model for ballistic transport of the inhibitor inside trenches is developed to account for this behavior: the model reveals that suppression of a bread-loaf profile is best accomplished with growth inhibitors that have a high sticking probability (>0.1 per wall collision) and that are consumed during growth. Four molecules are investigated as potential inhibitors during HfO 2 growth: tris(dimethylamino)silane, 3DMAS; methoxytrimethylsilane, MOTMS; hexafluoroacetylacetone, H(hfac); and acetylacetone, H(acac). The molecules 3DMAS and MOTMS inhibit growth but do so everywhere. As a result, they improve conformality, but are unable to eliminate the bread-loaf profile. In contrast, relatively small partial pressures (fluxes) of H(hfac) or H(acac) strongly inhibit HfO 2 growth and do so selectively on the upper substrate surface and near trench openings. In conjunction with the use of a forward-directed water flux that affords superconformal growth, the use of H(hfac) or H(acac) enables seamless fill of HfO 2 in trenches with aspect ratios as large as 10.
AB - Attempts to fill deep trenches by chemical vapor deposition often result in a "bread-loaf" profile, an overhang near the trench opening that arises whenever the growth rate is slightly higher near the opening than deeper in the feature. Continued growth leads to premature pinch-off at the opening, which leaves an undesirable void or seam along the centerline. Bread-loaf profiles can form even under superconformal growth conditions, as the authors recently found for the growth of HfO 2 from the precursor tetrakis(dimethylamino)hafnium and a forward-directed flux of H 2 O coreactant. The current paper describes a method that can reduce or eliminate the bread-loaf problem: addition of an isotropic flow of a reactant that inhibits growth near the trench opening but leaves the growth rate unchanged deeper in the trench. A Markov chain model for ballistic transport of the inhibitor inside trenches is developed to account for this behavior: the model reveals that suppression of a bread-loaf profile is best accomplished with growth inhibitors that have a high sticking probability (>0.1 per wall collision) and that are consumed during growth. Four molecules are investigated as potential inhibitors during HfO 2 growth: tris(dimethylamino)silane, 3DMAS; methoxytrimethylsilane, MOTMS; hexafluoroacetylacetone, H(hfac); and acetylacetone, H(acac). The molecules 3DMAS and MOTMS inhibit growth but do so everywhere. As a result, they improve conformality, but are unable to eliminate the bread-loaf profile. In contrast, relatively small partial pressures (fluxes) of H(hfac) or H(acac) strongly inhibit HfO 2 growth and do so selectively on the upper substrate surface and near trench openings. In conjunction with the use of a forward-directed water flux that affords superconformal growth, the use of H(hfac) or H(acac) enables seamless fill of HfO 2 in trenches with aspect ratios as large as 10.
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U2 - 10.1116/1.5068684
DO - 10.1116/1.5068684
M3 - Article
AN - SCOPUS:85060641275
VL - 37
JO - Journal of Vacuum Science and Technology A
JF - Journal of Vacuum Science and Technology A
SN - 0734-2101
IS - 2
M1 - 021509
ER -