====== Fabricating SNSPDs ======

Fabrication based on Nb(Ti)N

===== Film deposition =====
^ Group ^ Year ^ Publication ^ Process ^ Recipe ^ Notes ^
| Karl K. Berggren et al. \\ **NbN** | 2009 | {[Dauler:2009]} | DC magnetron sputtering | Sapphire, 800C, 8 mTorr, with 100 sccm Ar, 5 sccm N<sub>2</sub> | Parameters varied: deposition time, substrate material and deposition pressure. \\ Deposition time strongly influences the yield. (Pg 60,61) |
| :::  | 2015 | {[Najafi.Dane.ea:2015]} | DC magnetron sputtering | as above | Solvent cleaning exposure to an oxygen plasma (20% 0<sub>2</sub> in He) 100 W for 3 min |
| :::  | 2017 | {[Zhu:2017]} | DC magnetron sputtering | AlN, 840C, Ar, N<sub>2</sub> 26.5sccm, 8sccm, 2.5mTorr | Sheet resistance goal between 500-530 Ohm/sq |
| Jeff F. Young \\ **NbTiN** | 2017 | {[Yan:2017]} | DC magnetron sputtering | STAR Cryoelectronics Inc. Commercial | |
| Robert Hadfield \\ **NbTiN** | <2017 | {[Kirkwood:2017} | DC magnetron sputtering | STAR Cryoelectronics Inc. Commercial | |
| :::  | 2017 | {[Banerjee:2017]} | DC magnetron sputtering | Own developed | |
===== Lithography =====
^ Group ^ Year ^ Publication ^ Resist ^ Recipe ^ Notes ^
| Karl K. Berggren et al. \\ **NbN** | -- | -- | -- | -- |
| Jeff F. Young . \\ **NbTiN** | 2017 | {[Yan:2017]}  |ZEP520A (past shelf life) (Positive resist) (markers) | 500nm, 180C 3 min, o-xylene | Preparation: DI water, 2min US, Acetone, 2min US, IPA, 2min US. N2 dry, 100C dehydration for 1 min|
| ::: | ::: | ::: | (negative resist)(meander) | 150nm, 180C 3 min | ::: |
| Wolfram Pernice . \\ **NbN** | 2018 | {[Munzberg.Vetter.ea:2018]}  | HSQ |  | Cover the NbN with a SiO2 layer to protect against oxidation and as adhesion promoter for HSQ.|
===== Pattern transfer =====
All of the groups in literature use a dry etching process to transfer the pattern on the film.

^ Group ^ Year ^ Publication ^ Process Gases ^ Recipe ^ Notes ^
| Karl K. Berggren \\ **NbN** | <2015 | {[Dauler:2009]}, {[Yang:2005]} | CF<sub>4</sub> | 10mTorr, 15sccm CF<sub>4</sub>, 100W RF power | |
| :::  | 2015 | {[Najafi.Mower.ea:2015]}, {[Najafi.Dane.ea:2015]}, {[Najafi:2015]} | CF<sub>4</sub>| 50W | rest of recipe not mentioned. |
| :::  | 2017 | {[Zhu:2017]} | CF<sub>4</sub>, He| 10mTorr, He, CF4, 7sccm, 15sccm, 50W | Cleaning etch before with CF<sub>4</sub> and O<sub>2</sub>. Over-etching reduces device yield. |
| Jeff F. Young \\ **NbTiN** | 2017 | {[Yan:2017]} | CF<sub>4</sub>, O<sub>2</sub> | 30mTorr, 15sccm CF<sub>4</sub>, 2 sccm O<sub>2</sub>, 50W RF power | No saturating results seen. |
| Robert Hadfield \\ **NbTiN** | 2017 | {[Kirkwood:2017]} | CF<sub>4</sub> | 30mTorr, 50sccm CF<sub>4</sub>, 80W RF power | Not sure about the quality of the detectors |
| Wolfram Pernice . \\ **NbN** | 2018 | {[Munzberg.Vetter.ea:2018]}  | Fluorine based |  | Cover the NbN with a SiO2 layer to protect against oxidation and as adhesion promoter for HSQ.|
===== Characterization =====
The different techniques for Film characterization given by different groups.
^ Group ^ Method ^ Publication ^ Notes ^
| Karl K. Berggren \\ **NbN** | $R_\mathrm{RT} / R_\mathrm{20K} $ | {[Zhu:2017]} | Comparing the value at RT vs just above Transition temperature allows to investigate impurities. Good Films had on the order of 0.84 |
| ::: | $\Delta T_C$ | {[Zhu:2017]} | Difference between the temperature of 10% of $R_\mathrm{20K}$ and 90% of $R_\mathrm{20K}$. Good Films had approx 1.8K|
| ::: | $T_C$ | {[Zhu:2017]} | Resistance below $50\% ~ R_\mathrm{20K}$|


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