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| =Niobium Nitride=
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| Niobium–titanium (Nb‑Ti) is a ductile, readily machinable alloy that merges niobium’s superconductivity with titanium’s strength, yielding a rigid, corrosion‑resistant material valued in cryogenic and high‑field environments.
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| Thin films are produced chiefly by magnetron sputtering, where the Nb/Ti ratio and post‑anneal determine phase purity, resistivity, and the superconducting critical temperature (≈ 9.2 K for near‑eutectic compositions).
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| In microelectronics, Nb‑Ti can act as a robust diffusion barrier, gate or contact metal, and mechanically compliant liner. Yet, its signature role is as a superconductor: kilometer-length multifilament Nb-Ti wires carry mega-ampere currents in MRI scanners, particle-accelerator magnets, and experimental fusion coils under magnetic fields approaching 10 T.
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| Ultrathin Nb‑Ti nanowires serve in superconducting nanowire single‑photon detectors, kinetic‑inductance detectors, and low‑loss microwave resonators, while Nb‑Ti/Al bilayers enable Josephson junctions and rapid single‑flux‑quantum circuits.
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| The alloy’s radiation tolerance, thermal stability, and moderate atomic number support cryogenic beam‑line components and X‑ray filters, and its biocompatibility and wear resistance extend its usefulness to medical implants and protective MEMS coatings, underscoring Nb‑Ti’s versatility wherever robust, easily processed superconducting or barrier films are required.
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| ==Sputter deposition of Niobium Nitride==
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| Users can deposit NbTi in either the Sputter-System (Lesker) or the Sputter-System Metal-Nitride(PC3) (Preferable option)
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| * [[Specific Process Knowledge/Thin film deposition/Depositionof NbTi/Deposition of NbTi in Sputter-System Metal-Nitride PC3/|Deposition of NbTi in Sputter-System Metal-Nitride(PC3)]]
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| ==Comparison of sputter systems for alloy deposition==
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| ![[Specific_Process_Knowledge/Thin_film_deposition/Cluster-based_multi-chamber_high_vacuum_sputtering_deposition_system|Sputter-System Metal-Nitride(PC3)]]
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| ![[Specific Process Knowledge/Thin film deposition/Lesker|Lesker sputter system]]
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| !Generel description
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| *DC/Pulsed DC
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| *HIPIMS (high-power impulse magnetron sputtering) (require 3-inch target)
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| *DC sputtering (not tested)
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| !Stoichiometry
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| *NbTi (Sputter-System Metal-Nitride(PC3))
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| NbTi 67/33 At.% (4" target)
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| *Unknown
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| !Film thickness
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| *Limited by process time.
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| *Deposition rate (0.67 nm/s) likely faster than Sputter-System (Lesker)
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| *Limited by process time.
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| *Deposition rate unknown
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| !Process temperature
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| *Up to 600 °C
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| *Up to 400 °C
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| !Step coverage
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| *Some step coverage possible
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| *Some step coverage possible but amount unknown
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| !Film quality
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| *Deposition on one side of the substrate
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| *Properties including tunable stoichiometry (requires process development)
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| *Deposition on one side of the substrate
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| *Unknown quality
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| *Likely O-contamination
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| !Batch size
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| *Many smaller samples
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| *Up to 10*100 mm or 150 mm wafers
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| *Several smaller samples
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| *1-several 50 mm wafers
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| *1*100 mm wafers
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| *1*150 mm wafer
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| !'''Allowed materials'''
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| *Almost any as long as they do not outgas and are not very toxic, see cross-contamination sheets
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| *Almost any as long as they do not outgas and are not very toxic, see cross-contamination sheets
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| <!--
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| Deposition of Silicon Nitride can be done with either LPCVD (Low Pressure Chemical Vapor Deposition) or PECVD (Plasma Enhanced Chemical Vapor Deposition).
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| ==Deposition of Silicon Nitride using LPCVD==
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| LPCVD silicon nitride can be deposited in a [[Specific Process Knowledge/Thin film deposition/B2 Furnace LPCVD Nitride|LPCVD nitride furnace]]. DTU Nanolab has two LPCVD nitride furnaces: A new furnace (installed in 2008) for deposition of stoichiometric nitride on 4" or on 6" wafers and an older furnace (installed in 1995) for deposition of stoichiometric nitride and low stress nitride on 4" wafers.
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| The LPCVD nitride deposition is a batch process, meaning that nitride can be deposited on a batch of up to 15 wafers (in the old nitride furnace) or 25 wafers (in the new nitride furnace) at a time. The deposition takes place at temperatures of 780-845 degrees Celsius and at a pressure of 120-200 mTorr. The LPCVD silicon nitride has a good step coverage, and the film thickness is very uniform over the wafers. On the furnaces there are standard processes for deposition of stoichiometric nitride (Si<sub>3</sub>N<sub>4</sub>) and for deposition of low stress nitride (SRN) (only on the old nitride furnace).
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| *[[/Deposition of Silicon Nitride using LPCVD|Deposition of Silicon Nitride using LPCVD]]
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| ==Deposition of Silicon Nitride using PECVD==
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| PECVD nitride and oxynitride can be deposited in one of the [[Specific Process Knowledge/Thin film deposition/PECVD|PECVD]] systems at DTU Nanolab. You can run 1-3 wafers on several smaller chips at a time depending on which one of the PECVD's you use. The deposition takes place at 300 degrees Celsius. This can be of importance for some applications, but it gives a less dense film compared to LPCVD nitride, and the stoichiometry is on the following form: Si<sub>x</sub>N<sub>y</sub>O<sub>z</sub>H<sub>v</sub>. The step coverage and the thickness uniformity of the film are not as good as for the LPCVD nitride. In one of our PECVD systems (PECVD3) we allow small amounts of metal on the wafers entering the system; this is not allowed in the LPCVD furnace and in the clean PECVD (PECVD1). We also have a PECVD for deposition on III-V materials (PECVD2).
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| *[[/Deposition of Silicon Nitride using PECVD|Deposition of Silicon Nitride using PECVD]] - ''or oxynitride''
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| ==Comparison of LPCVD and PECVD for silicon nitride deposition==
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| {| border="1" cellspacing="0" cellpadding="3" align="center"
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| !
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| ! [[Specific Process Knowledge/Thin film deposition/Furnace LPCVD Nitride|LPCVD]]
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| ! [[Specific Process Knowledge/Thin film deposition/PECVD|PECVD]]
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| | Stoichiometry
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| *Si<sub>3</sub>N<sub>4</sub>
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| *SRN (only old nitride furnace, only 4" wafers)
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| Si<sub>3</sub>N<sub>4</sub>: Stoichiometric nitride
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| SRN: Silicon rich nitride (low stress nitride)
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| *Si<sub>x</sub>N<sub>y</sub>H<sub>z</sub>
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| *Si<sub>x</sub>O<sub>y</sub>N<sub>z</sub>H<sub>v</sub>
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| Silicon nitride can be doped with boron, phosphorus or germanium
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| |Film thickness
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| *Si<sub>3</sub>N<sub>4</sub>: ~50 Å - ~1400 Å
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| *SRN: ~50 Å - ~2800 Å
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| Thicker nitride layers can be deposited over more runs
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| *~40 nm - 10 µm
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| |Process temperature
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| *780 <sup>o</sup>C - 845 <sup>o</sup>C
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| *300 <sup>o</sup>C
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| |Step coverage
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| *Good
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| *Less good
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| |Film quality
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| *Deposition on both sides of the substrate
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| *Dense film
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| *Few defects
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| *Deposition on one side of the substrate
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| *Less dense film
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| *Incorporation of hydrogen in the film
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| |Batch size
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| Old nitride furnace:
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| *1-17 4" wafers per run
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| New nitride furnace:
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| *1-25 4" or 6" wafers per run
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| *1-3 4" wafers or one 6" wafer or many smaller chips per run
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| | Substrate materials allowed
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| *Silicon wafers (new wafers or RCA cleaned wafers)
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| **with layers of silicon oxide or silicon (oxy)nitride (RCA cleaned)
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| **from furnaces in stack A or B in cleanroom 2
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| *Pure quartz (fused silica) wafers (RCA cleaned)
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| *Silicon wafers
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| **with layers of silicon oxide or silicon (oxy)nitride
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| *Quartz wafers
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| *Small amounts of metal < 5% of the wafer coverage (ONLY in PECVD3!)
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| | Etch rate in 80 <sup>o</sup>C KOH
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| |Expected <1 Å/min
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| |Dependent on recipe: ~1-10 Å/min
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| | Etch rate in BHF
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| |Very low
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| |Very high compared to the etch rate of LPCVD nitride
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