Process, Structure and Properties of CrN Coatings deposited using Modulated Pulse Power (MPP) Sputtering

Transcription

1 Process, Structure and Properties of CrN Coatings deposited using Modulated Pulse Power (MPP) Sputtering Jianliang Lin, John J. Moore, Zhili Wu, Brajendra Mishra Advanced Coatings and Surface Engineering Laboratory, Colorado School of Mines, Golden, CO, USA William.D Sproul Reactive Sputtering, INC, San Marcos, California, USA. Roman Chistyakov, Bassam Abraham Zpulser, LLC, MA, USA

2 Content Introduction of MPP technology MPP system in ACSEL MPP sputtered CrN coatings (Compared v.s. continuous dc and pulsed dc sputtered CrN coatings) Structure and properties Oxidation resistance Summary

3 MPP Technology High power pulse magnetron sputtering technique Multi-step DC pulse First step ignition of low power discharge Second step low power discharge Third step transient stage from low power discharge to high power discharge Forth step- high power discharge 3 4 Voltage 1 2 Weakly Ionized Plasma Strongly Ionized Plasma Power Current The micro pulses within the pulse segments offer the flexibility to stable the plasma and control the voltage, current, and power

4 MPP Technology Why Modulated Pulse Power (MPP) magnetron sputtering? High ionization degree of metal species Very high deposition rates (for both metal and insulating films) Deposition of dense and uniform films Easy scaling up (has moderate peak powers) Influencing film properties and structure by modulated pulse parameters Deposition Rate [nm/min] M PP Cr D C Cr The increase rate of the deposition rate in M PP changes near W /cm 2 dc Dc Cr Average Target Power Density [W /cm 2 ] MPP MPP Cr

5 MPP System in ACSEL MPP system and EQP plasma analyzer Zpulser MPP generator Unbalanced magnetrons (100 mm x 280 mm) Closed magnetic configuration Closed Magnetic field Hiden electrostatic quadrupole plasma mass spectrometer (EQP) N S Cr S 14 cm N Al N S EQP

6 MPP CrN Coatings (compared with dc and pulsed dc): Structure and properties of MPP CrN coatings synthesized at various f N2. Deposition of layered CrN coating using modulated pulse shapes Oxidation behavior of typical MPP, dc and PMS CrN coating

7 Deposition and Pulsing Parameter MPP CrN coatings: Working pressure: 5 mtorr Pulse period: 1.5 ms The repetition rate: 30 Hz Substrate bias: floating V on /V off =16/6 us DC and Pulsed DC CrN coatings: Target power: 1kW Working pressure: 2 mtorr Pulse parameter: 100 khz and 50% duty cycle Substrate bias: -50 V DC bias Power Voltage Current P ave = 4.15~4.29 kw I peak = A V ave = V Increased with the increase of N 2 percentages

8 GIXRD of MPP CrN coatings Deposited at Different f N2 CrN(111) CrN(200) f N2 60% CrN(220) 50% c-crn Intensity [CPS] Cr 2 N(111) 40% 30% Cr 2 N(112) Cr2 N(300) β Cr 2 N+c-CrN β Cr 2 N 20% β Cr 2 N+Cr(N) Cr(N) 10% Cr(N):bcc Cr doped with N Diffraction Angle [2-Theta] Similar phase changes observed in dc and PMS

9 Microstructure Comparison (DcMS, PMS, MPP) DcMS PMS MPP f N2 =20-30% (h-cr 2 N) f N2 =50-60% ( c-crn) Zone-T columnar grains High density and fine grains High density and fine grains

10 Hardness and Young s Modulus MPP CrN coatings Dc and PMS CrN coatings 32 Cr+Cr 2 N Cr 2 N CrN+Cr 2 N CrN Hardness [GPa] Hardness Young's modulus Young's Modulus [GPa] Hardness [GPa] dc magnetron sputtering pulsed at 100 khz and 5.0 us Nitrogen Flow Rate Percentage [%] N 2 Percentages [%] Floating substrate bias -50 V dc substrate bias

11 Pin-on-disc test (3 N, 40 rpm, 5000 cycles, 1mm WC-Co ball) Wear Resistance Coefficient of Friction MPP CrN coatings (Floating bias) dc CrN coatings (-50V bias) PMS CrN coatings (-50V bias) Nitrogen Flow Rate Percentage [%] The COF is lower in the MPP CrN coatings than in dc and PMS CrN coatings.

12 MPP CrN Coatings (compared with dc and pulsed dc): Structure and properties of MPP CrN coatings synthesized at various f N2. Deposition of layered CrN coating using modulated pulse shapes Oxidation behavior of typical MPP, dc and PMS CrN coatings

13 Using Two Pulse Shapes Working pressure: 5 mtorr Nitrogen flow rate percentage: 40% Two pulse shapes alternating (see the figures below) Substrate bias: floating A A 700 µs (6/6), 100 Hz rep rate Duration: 1S and 3S 1500 µs (6/10), 30 Hz rep rate Duration: 1S and 2S

14 Two pulse shapes with 2~3s duration 700 µs (6/6), 100 Hz rep rate 1500 µs (6/10), 30 Hz rep rate P ave =0.8 kw Duration: 3S P ave =3.5 kw Duration: 2S Dense structure with fine grains Properties: Hardness: ±1.796GPa Young s Modulus: ±7.260GPa H/E ratio: COF: Increased H/E ratio compared to the single pulse coating (about 0.75 at 40% N 2 ), however, the deposition rate is lower in the modulus pulsed coatings

15 Two pulse shapes with 1s Duration 700 µs (6/6), 100 Hz rep rate P ave =0.8 kw Duration: 1S 1500 µs (6/10), 30 Hz rep rate P ave =3.5 kw Duration: 1S Denser structure with finer grains Properties: Hardness: ±1.615GPa Young s Modulus: ±11.87GPa H/E ratio: COF: 0.25 COF MPP CrN coating (11) 0.8 COF(ave)= Cycles

16 MPP CrN Coatings (compared with dc and pulsed dc): Structure and properties of MPP CrN coatings synthesized at various f N2. Deposition of layered CrN coating using modulated pulse in MPP Oxidation behavior of typical MPP, dc and PMS CrN coatings The coatings are near stochimetric concentrations (N/Cr=0.90~0.95); Annealed in ambient air from o C for one hour.

17 Annealed at 900 o C for 1hr Green: O Red: N dc CrN Cr 2 O 3 layer (500nm) Pulsed dc CrN Cr 2 O 3 layer ( nm) Significant N loss Cr 2 O 3 layer (300nm) MPP CrN Almost no porous region

18 Annealed at 1000 o C for 1hr Green: O Red: N dc CrN Cr 2 O 3 layer (2500nm) Significant N loss Pulsed dc CrN Cr 2 O 3 layer (2000nm) Cr 2 O 3 layer (1000nm) MPP CrN Almost no porous region

19 Summary The evolution of the crystal phases in MPP CrN coatings with increasing the f N2 is in consistence with dc and PMS CrN coatings. However, the MPP CrN coatings prepared at a floating substrate bias exhibited denser microstructure, comparable hardness and improved wear resistance to dc sputtered CrN coatings synthesized using -50 V dc substrate bias. In addition, the MPP CrN coatings deposited using multiple pulse shapes exhibit further improved H/E ratio and wear resistance, where a low COF of 0.25 has been identified. MPP CrN coatings showed significant improvements in the oxidation resistance in the temperature range of o C, which is probably because of its high density and low residual stress.

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