Vapour pressure measurement of zirconium chloride and hafnium chloride by the transpiration technique

Tangri, R.P.; Bose, D. N.

doi:10.1016/0040-6031(94)80224-6

Cited by 10 publications

(7 citation statements)

References 4 publications

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“…HfCl 4 has a vapor pressure of 6 Torr at 203 °C and 1214 Torr at 329 °C. 35,36 However, the Hf-containing etch products are not detected until >450 °C, above the melting point of HfCl 4 at 432 °C. If HfCl 4 was formed on the surface, then HfCl 4 should be volatilized at temperatures much lower than 450 °C.…”

Section: Resultsmentioning

confidence: 99%

“…Comparison between the Si ligand-exchange products and the Hf-containing etch products reveals that ligand exchange can occur at low temperature, but the Hf-containing etch products are not observed until much higher temperatures. HfCl 4 has a vapor pressure of 6 Torr at 203 °C and 1214 Torr at 329 °C. , However, the Hf-containing etch products are not detected until >450 °C, above the melting point of HfCl 4 at 432 °C. If HfCl 4 was formed on the surface, then HfCl 4 should be volatilized at temperatures much lower than 450 °C.…”

Section: Resultsmentioning

confidence: 99%

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Spontaneous Etching of Metal Fluorides Using Ligand-Exchange Reactions: Landscape Revealed by Mass Spectrometry

et al. 2021

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Thermal atomic layer etching (ALE) can be performed using sequential reactions based on surface modification followed by volatile release of the modified surface layer. Surface modification can be accomplished using fluorination. Volatile release can then be achieved using precursors that undergo ligand-exchange reactions with the fluorinated surface layer. Metal fluorides can be employed to model the fluorinated surface layer. The ligand-exchange reaction between the precursor and the metal fluoride can lead to spontaneous etching of the metal fluoride. A new reactor with in situ quadrupole mass spectrometry (QMS) was constructed to observe the volatile etch products from the reaction of ligand-exchange precursors with metal fluoride powders. The metal fluoride powders were AlF3, HfF4, GaF3, InF3, and SnF4. The ligand-exchange precursors were Al(CH3)3, SiCl4, and TiCl4. A variety of studies were conducted including Al(CH3)3 + AlF3, SiCl4 + HfF4, SiCl4 + InF3, TiCl4 + SnF4, Al(CH3)3 + GaF3, and SiCl4 + AlF3. The temperature-dependent in situ QMS studies revealed the many possibilities that occur during the ligand-exchange reaction of precursors with metal fluoride powders. Various categories of behavior were observed from these studies: (i) Ligand exchange occurs at low temperature, but metal etch products from the substrate are not observed until high temperature. (ii) Ligand-exchange and metal etch products from the substrate are observed at similar temperatures. (iii) Ligand exchange occurs, but no metal etch products from the substrate are observed up to a limiting temperature. Knowledge of these possibilities for the ligand-exchange reaction between precursors and metal fluoride powders during spontaneous etching helps to further the understanding of thermal ALE.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Spontaneous Etching of Metal Fluorides Using Ligand-Exchange Reactions: Landscape Revealed by Mass Spectrometry

et al. 2021

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“…ZrCl 4 and HfCl 4 both have similar vapor pressures at and above the onset temperatures for ligand exchange. ZrCl 4 has a vapor pressure of 1 Torr at 180 °C . HfCl 4 has a vapor pressure of 1 Torr at 170 °C .…”

Section: Resultsmentioning

confidence: 66%

“…ZrCl 4 has a vapor pressure of 1 Torr at 180 °C. 41 HfCl 4 has a vapor pressure of 1 Torr at 170 °C. 41 Similar onset temperatures for the metal etch products are expected if the products have comparable vapor pressures.…”

Section: 3c Zrfmentioning

confidence: 99%

Effectiveness of Different Ligands on Silane Precursors for Ligand Exchange to Etch Metal Fluorides

et al. 2022

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Metal fluorides can be spontaneously etched by ligand-exchange reactions. During these reactions, the exchange of ligands between the incoming precursor and the metal fluoride leads to the volatilization of the metal fluoride. These ligand-exchange reactions are important in many thermal atomic layer etching (ALE) processes. To test the effectiveness of different ligands for ligand exchange, the spontaneous etching of metal fluorides by silane precursors containing different ligands was investigated using in situ quadrupole mass spectrometry (QMS). The homoleptic and heteroleptic silane precursors were SiCl4, SiCl2(CH3)2, SiCl(CH3)2H, and Si(CH3)4. These silane precursors provide Cl, CH3, or H ligands for the ligand-exchange reaction. The metal fluorides were GaF3, InF3, ZnF2, ZrF4, HfF4, and SnF4. The QMS results showed that F/Cl ligand exchange was observed for all the metal fluorides with chlorine-containing silane precursors. In addition, all the volatile metal etch products were metal chlorides, namely, GaCl3, InCl3, ZnCl2, ZrCl4, HfCl4, and SnCl4. No metal methyl complexes were detected as volatile metal etch products indicating no F/CH3 exchange. For SiCl(CH3)2H as the silane precursor, the observation of SiF2(CH3)2 indicated that F/H exchange is also possible in addition to F/Cl exchange. For the various metal fluorides, the dominance of the F/Cl exchange led to nearly equivalent onset temperatures for ligand exchange and for etching to yield metal chlorides. Thermochemical calculations of the ligand-exchange reactions also predicted the formation of metal chlorides. All F/Cl exchanges were the most thermodynamically favorable as demonstrated by their negative changes in Gibbs free energy (ΔG). These experimental and theoretical results provide guidelines for designing precursors for thermal ALE processes.

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“…The source was held in a custom-made box furnace at 140−175 °C, and the piping was heated 10 °C hotter than the source. A known volume in the gas line was used to quantify the precursor flux, where vapor pressure saturation is assumed . Water was delivered to the reactor through a leak valve either with background dosing or using a directional dosing tube.…”

Section: Methodsmentioning

confidence: 99%

Adsorption and Reaction of HfCl₄ with H₂O-Terminated Si(100)-2 × 1

et al. 2008

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A combined experimental and density functional theory study has been performed to investigate the bonding arrangements, saturation coverage, and factors that limit the saturation coverage for the adsorption of HfCl4(g) on a water-terminated Si(100)-2 × 1 surface. Experiments with X-ray photoelectron spectroscopy, Rutherford backscattering spectrometry, and reflection high-energy electron diffraction show that adsorption occurs at hydroxyl sites and forms an atomically abrupt metal−oxide/semiconductor interface. The saturation Hf coverage is measured at (2.0 ± 0.2) × 1014/cm2, which is approximately 2/3 of the available hydroxyl sites. Density functional theory calculations of various configurations of adsorbed OHfCl3 fragments show a strong interaction between the adsorbed fragment and neighboring hydroxyls. On the basis of the density functional theory calculations, a random adsorption model has been constructed to model the adsorption of H2O(g) on Si(100)-2 × 1 and the adsorption of HfCl4(g) on the H2O−Si(100)-2 × 1 surface. The model predicts a saturation coverage of (2.05 ± 0.05) × 1014 Hf/cm2, which is close to the experimental data. The main factor that limits the reactant coverage is found to be a preferred reaction at two hydroxyl sites. The surface is made up of roughly equal numbers of OHfCl3 and (O)2HfCl2 adsorbates. The extension of the results to adsorption and reaction on SiO2 is discussed.

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Vapour pressure measurement of zirconium chloride and hafnium chloride by the transpiration technique

Cited by 10 publications

References 4 publications

Spontaneous Etching of Metal Fluorides Using Ligand-Exchange Reactions: Landscape Revealed by Mass Spectrometry

Spontaneous Etching of Metal Fluorides Using Ligand-Exchange Reactions: Landscape Revealed by Mass Spectrometry

Effectiveness of Different Ligands on Silane Precursors for Ligand Exchange to Etch Metal Fluorides

Adsorption and Reaction of HfCl₄ with H₂O-Terminated Si(100)-2 × 1

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Vapour pressure measurement of zirconium chloride and hafnium chloride by the transpiration technique

Cited by 10 publications

References 4 publications

Spontaneous Etching of Metal Fluorides Using Ligand-Exchange Reactions: Landscape Revealed by Mass Spectrometry

Spontaneous Etching of Metal Fluorides Using Ligand-Exchange Reactions: Landscape Revealed by Mass Spectrometry

Effectiveness of Different Ligands on Silane Precursors for Ligand Exchange to Etch Metal Fluorides

Adsorption and Reaction of HfCl4 with H2O-Terminated Si(100)-2 × 1

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Adsorption and Reaction of HfCl₄ with H₂O-Terminated Si(100)-2 × 1