Optjmizatjon of magnetron sputuer-depositjon process of thin fjlm - PowerPoint PPT Presentation

Optjmizatjon of magnetron sputuer-depositjon process of thin fjlm coatjngs on a moving cylindrical substrate PhD. Student Seminar 07/04/2016 Thomas LE COZ Supervisors : A. Lacoste M. Mantel A. Bes C. Vachey

Outline Context → Why do we want to coat wire ? → Scientjfjc issues Employed technology → Main specifjcatjons of reactjve sputuering in an inverted cylindrical magnetron (ICM) Commercial magnetron → Characterizatjon of the fjrst used commercial magnetron Ugitech made magnetron → Characterizatjon of the magnetron designed by the company Conclusions and Forthcoming work 07/04/2016 PhD. Seminar - LE COZ T. 2

Context Wide amount of stainless steel wire used in many fjelds : → Architecture → Urbanizatjon → Art → Cold heading → Automotjve … 07/04/2016 PhD. Seminar - LE COZ T. 3

Context Scientjfjc issues Sizing the system for : Consideratjons : → Fast roll-to-roll process → Geometry → Uniform coatjngs → Electric → High quality coatjngs → Magnetjc → Thermal 07/04/2016 PhD. Seminar - LE COZ T. 4

Employed technology Physical Vapor Depositjon (PVD) Water cooling Cathode Cathode Substrate V plasma V substrate Target e - Plasma bulk V e - E Ar Ar + + e - Substrate V cathode Cathode sheath Substrate holder Anodic sheath (anode) → Ionizatjon of argon atoms by surrounding → Potentjal drop in the sheath accelerates electrons the ions used to sputuer the target 07/04/2016 PhD. Seminar - LE COZ T. 5

Employed technology Magnetron sputuering → Plasma close to the target → High density (10 10 – 10 11 cm -3 ) → Low pressure (0.1 Pa) → Race tracks leading to non- homogeneous coatjngs Repulsive wall Inverted cylindrical confjguratjon → Conformal geometry B Cathode / Target → No loss of matuer on the walls Anode / substrate 07/04/2016 PhD. Seminar - LE COZ T. 6

Employed technology Reactjve sputuering Poisonned mode → Argon plasma → Nitrogen as reactjve gas → Titanium target Stoechiometry (x=1) → Formatjon of TiN x on target and substrate → Instability of the stoechiometric Metalic mode point Lindberg et al., « Reactjve depositjon of nitrides and oxides using a twin- cathode inverted cylindrical magnetron », Surface and Coatjngs Technology 133-134 (2000) 484-488. 07/04/2016 PhD. Seminar - LE COZ T. 7

Employed technology Reactjve sputuering → Sputuering yield depends on the material 07/04/2016 PhD. Seminar - LE COZ T. 8

Commercial magnetron Geometry Sofu iron Insulator Target Gas inlet Cathode : - Diameter : 5 cm - Length : 2*10 cm 5 cm 10 cm Substrate : - Diameter : 2 mm - Grounded Pumping Magnet (NdFeB) Water cooling Substrate → Two isolated targets for RF sputuering – we use DC sputuering 07/04/2016 PhD. Seminar - LE COZ T. 9

Commercial magnetron Magnetjc confjguratjon → 4 rings of 30 magnets → heterogeneity of the magnetjc fjeld → two racetracks per target → consumptjon of the targets : 30 % → Necessity of homogeneous magnetjc fjeld Unit : T 07/04/2016 PhD. Seminar - LE COZ T. 10

Commercial magnetron Magnetjc confjguratjon → Two ways to get a homogeneous magnetjc fjeld : - increase the diameter of the magnetjc rings - use a coil 0.038 T Magnetjc fjeld intensity on the target surface Unit : T 07/04/2016 PhD. Seminar - LE COZ T. 11

Commercial magnetron Unit : T Magnetjc confjguratjon → Two ways to get a homogeneous magnetjc fjeld : - increase the diameter of the magnetjc rings - use a coil Magnetjc fjeld intensity on the target surface 07/04/2016 PhD. Seminar - LE COZ T. 12

Commercial magnetron Magnetjc confjguratjon → Electron leakage leading to the creeping and breaking of the wire 400 Substrate temperature (°C) 36 Electrons 30 300 V A = 0 V Power (W) 24 18 200 12 6 100 0 Atoms Ions Sec. Therm. Total 0 Species -30 -20 -10 0 10 20 30 Species contributjons to the heat load of the substrate Ofg-axis positjon (cm) → Substrate to repulsive potentjal 07/04/2016 PhD. Seminar - LE COZ T. 13

Commercial magnetron Magnetjc confjguratjon Schematjc of the depositjon chamber and pyrometric setup → Decrease of the substrate temperature → Modifjcatjon of the spatjal distributjon of the plasma 07/04/2016 PhD. Seminar - LE COZ T. 14

Commercial magnetron Magnetjc confjguratjon → Plasma characterizatjon through Langmuir probe measurements. V A = 0 V V A = 30 V I pb (mA) Positjon (cm) Positjon along the cathode axis (cm) Current (mA) V f Saturation Current (mA) ionique V p Probe potentjal (V) V pb (V) Probe potentjal (V) Distributjon of the Langmuir characteristjcs within the magnetron → Spatjal redistributjon of the plasma with the variatjons of the anode potentjal 07/04/2016 PhD. Seminar - LE COZ T. 15

Commercial magnetron Magnetjc confjguratjon No data because of a lack of collected current → More energetjc electrons when polarizing and electron density slightly superior → Betuer ionizatjon but spatjal redistributjon of the plasma 07/04/2016 PhD. Seminar - LE COZ T. 16

Commercial magnetron V A = 30 V Infmuence of the anode potentjal 1600 Ti - N2↗ (30 1400 V) Ti - N2↘ (30 1200 V) Ti Relatve intensity (a.u.) C Ti - N2↗ (0 V) 1000 Ti - N2↘ (0 V) 800 Acier 600 400 ASTAR pictures made by S. Grosso, SIMaP 200 0 V A = 0 V 0 1 2 3 4 5 6 V A = 0 V Nitrogen fmow(sccm) Ti → Hysteresis shifued to higher nitrogen fmows Acier → Grain size variatjon due to temperature → Difgusion of iron in the tjtanium coatjng EDX characterizatjon made by S. Grosso, SIMaP 07/04/2016 PhD. Seminar - LE COZ T. 17

Commercial magnetron Infmuence of the anode potentjal → Depositjon rate ≈ 60 nm/min Distance : D Distance : D’ Cible Cible Heart-shaped pulverizatjon → Depositjon profjle is changed due to plasma redistributjon Substrat Substrat 07/04/2016 PhD. Seminar - LE COZ T. 18

Commercial magnetron Operatjng parameters 250 350 300 200 Target voltage (V) 250 LPM (mm) 150 200 1000 W 4 500 W 150 100 5 10 100 mTorr 20 50 J i ∝ (V T ) 12 50 50 100 0 0 0 3 6 9 12 15 0 2 4 6 8 10 12 2 ) Current density (mA/cm Pressure (mTorr) Alexandru Todoran, « Magnetron sputuering in inverted cylindrical confjguratjon : 3D depositoin on moving substrate », thèse 2014 → J T α (V T ) 12 → Minimal turn-on pressure : 5 mTorr → Mean free path at 5 mTorr ≈ 25 mm = Distance cathode-target → Maximal operatjng power : 1000 W (by constructjon) 07/04/2016 PhD. Seminar - LE COZ T. 19

Commercial magnetron Operatjng parameters 1600 Ti - N2↗ (30 1 2 3 1400 V) → 1 : under-stoechiometric Relatjve intensity (a.u.) Ti - N2↘ (30 1200 V) → 2 : stoechiometric 1000 N - N2↗ (30 → 3 : over-stoechiometric V) 800 600 400 1 200 0 0 1 2 3 4 5 6 2 270 265 3 Cathode potentjal (V) 260 255 250 245 240 → More collisions due to the increase of species N2↗ (30 235 V) density leading to faster thermalizatjon 230 225 0 1 2 3 4 5 6 Nitrogen fmow (sccm) 07/04/2016 PhD. Seminar - LE COZ T. 20

Commercial magnetron Intermediate conclusion → Necessity of homogeneous magnetjc fjeld → Control of the substrate temperature by polarizing auxiliary electrodes … → … which infmuences the plasma distributjon within the reactjon chamber → Low depositjon rate → Power input limited → Unstable conditjons for stoechiometric coatjngs 07/04/2016 PhD. Seminar - LE COZ T. 21

Ugitech’s magnetron Magnetjc confjguratjon Bz (G) 150 Ofg-axis positjon (cm) → Non homogeneity of the magnetjc fjeld close to the target. 07/04/2016 PhD. Seminar - LE COZ T. 22 Unit : G

Ugitech’s magnetron Magnetjc confjguratjon Racetracks 0 0,8 28,2 29 1,8 4 5,5 9 10 11 13,5 17 19,5 21 22 24,5 25,5 30 Magnets Gas Gas 160 0 V - 30 s 140 Substrate temperature (°C) 120 Racetracks 100 80 → 5 racetracks 60 40 → 6 electrons leakage zones 20 → Target consumptjon: 36 % 0 -20 -15 -10 -5 0 5 10 15 20 07/04/2016 PhD. Seminar - LE COZ T. 23 Ofg-axis (cm)

Ugitech’s magnetron Operatjng parameters Hysteresis curves for difgerent target currents →Higher sputuering for higher current → Hysteresis for low nitrogen fmows →Increase of the ionizatjon rate 07/04/2016 PhD. Seminar - LE COZ T. 24

Ugitech’s magnetron Operatjng parameters Ugitech’s cathode Commercial cathode Ofg-axis positjon (cm) Depositjon rate as a functjon of the positjon in the cathode → Mean depositjon rate : 100 nm/min against 60 nm/min in commercial cathode → Heterogeneous thickness → Polarizatjon infmuences spatjal plasma distributjon 07/04/2016 PhD. Seminar - LE COZ T. 25

Ugitech’s magnetron Titanium nitride coatjngs Coated wire made in reactjve mode under 30 V of polarizatjon, 5 min statjc depositjon 1.2 1 → Oxygen contaminatjon 0.8 → Gold yellow is TiN 0.6 0.4 → Blue is TiN x O y 0.2 0 N / Ti O/Ti Ugi1– coté Ugi1 - Bosse Ugi1– centre Ratjo of nitrogen and oxygen concentratjons with respect to the colors on the wire 07/04/2016 PhD. Seminar - LE COZ T. 26