High Power Pulse Plasma Generators (HPPMS/HIPIMS/MPP) for Material Processing Applications. Zond, Inc / Zpulser, LLC. Mansfield, MA 02048 USA
Magnetron Sputtering Magnetron sputtering is a widely used PVD (Physical Vapor Deposition) technique to deposit thin films. This technique is based on the generation of a low pressure magnetically enhanced glow discharge magnetron discharge. J D J D Sputtering target surface B B J φ J φ - azimuthally rotating current density due to Hall effect (v E/B =(ExB)/B 2 ), J D - discharge current density running perpendicular to the magnetic field lines I(t) = {1+ γ SS (E)}I i 2
Magnetron Sputtered Films Columnar structure High stress Poor adhesion Low hardness Low level of ionization of sputtered target material Cr Ti Ta Ti Cr Cr 3
Magnetron Sputtering How to increase metal ion flux near the substrate? Unbalanced magnetron Special design HCM Secondary discharge between sputtering target and substrate Electrical bias on the substrate in order to control energy from the gas and sputtered target material atoms (DC bias, RF bias, Pulsed bias). More ions flux bias, Less ions flux bias, Usually bias voltage ~ -(20 200) V 4
Voltage Current Characteristic for DC Magnetron I d I d ~ β( U d ) n 40 A P = 20 kw (200 mm Wafer) Magnetron 0 300 V 500 V 700 V DC magnetron sputtering P ~ 10 100 W/cm 2, low level of ionization (low discharge current I d ) To increase level of ionization increase discharge current High Voltage High Current High Power Short Pulse High power pulse magnetron sputtering P ~ 0.3-10 kw/cm 2 U d -1000V, I d 1000 A Pulse duration ~ 50-200 µs Duty cycle 1-10 % U d 5
High Power Pulse Magnetron Sputtering High Power Pulse Magnetron Sputtering is a relatively new technology. First paper was published in 1995, second in 1996, third in1999. This is the most cost effective way to generate metal ions during the sputtering process. High level of ionization can be obtained at target power density in the range of 0.3 3 kw/cm 2 depends on applications Duty cycle of the pulse power generator usually is in the range of 5-20%. Typical Pulse duration ~ 50-200 µs 6
High Power Pulse Magnetron Sputtering (HPPMS/HIPIMS). Modulated Pulse Power (MPP) HPPMS HIPIMS MPP(1) MPP(2)
MPP Plasma Generator (Zpulser Solo) Output voltage pulse shape Circuit diagram for Zpulser Solo
Voltage waveforms after solid state switch (IGBT) before transformer +600 V Switch closed t, µs -600 V Switch open 600 V > Vch > 300 V 9
Voltage waveforms after transformer before diodes bridge +1200 V t, µs -1200 V 10
ton Voltage waveforms after diodes bridge toff t, µs -1200 V T T = (ton + toff) f = 1/(ton + toff) micro pulse Voltage waveform after LC circuit, output voltage -1100 V PULSE T Vout = βd D = ton/(ton + toff) 3µs< ton <18µs 6µs< toff <50µs f is in the range of 10-62.5 khz 11
Micro pulse frequency and micro pulse width modulations +1200 V t, µs micro pulse V output t, µs V output pulse consists of train of micro pulses 12
HIPIMS (HPPMS) and MPP (Modulated pulse power) HIPIMS MPP Pulse duration 50-200 µs? Rectangular voltage pulse Max voltage (1000-2000) V? Max Peak power 3 MW? Average Power 20 kw? Pulse duration 100-3000 µs Multistage voltage pulse Max voltage -1100 V Max Peak power 0.6 MW Average Power 22 kw Voltage oscillations 13
Arc in HIPIMS/HPPMS In HIPIMS the ignition voltage is equal to discharge voltage!!! Arc in HIPIMS can happened in the ignition stage or in high power stage t V MPP controls the ignition stage and high power stage ( long medium power instead of short high power) 14
Micro pulse frequency and micro pulse width modulations for control output voltage pulse 6 34 6 34 10 10 10 10 12 10 14 10 14 10 14 t, µs +1200 V micro pulses t, µs ~(100 500) µs pre-ionization High Peak Power 1 st rise time V1 V output pulse consists of train of micro pulses 2 nd rise time V2 15
Micro pulse frequency and micro pulse width modulations for control output voltage pulse 6 34 6 34 8 10 11 10 12 10 14 10 14 10 14 t, µs +1200 V micro pulses ~(100 500) µs pre-ionization t, µs High Peak Power V output pulse consists of train of micro pulses V2 16
High Power Pulse Magnetron Sputtering, Zpulser Solo Plasma Generator (2) 200 A 200 A (1) (2) Yellow line discharge voltage, blue line discharge current, Cr target (500 cm2) 17
Voltage Pulse Shapes (Zpulser Solo) (1) (2) (3) (4) (5) Yellow line voltage, blue linecurrent (1) (3) Cr target (80 cm2) (4) (5) Resistive load 18
Plasma Photo in dc and MPP sputtering (Colorado School of Mine-ACSEL) Conventional dc Magnetron Sputtering operated at 1.5 kw MPP TM sputtering P ave =1.5 kw MPP TM sputtering P ave =2.7 kw MPP TM sputtering P ave =3.5 kw MPP TM sputtering P ave =4.09 kw
MPP, Ta sputtering process Bias = -30 V Bias = - 30 V MPP Intensity, counts/sec DC 140 OES Ta+ Ta+ 120 100 Ta+ 80 60 40 20 0 200 250 300 Wavelength λ, nm 350
CONCLUSION 1. Zpulser plasma generator Solo/ Axia generates multistage negative voltage pulse with controllable voltage rise, duration and amplitude. 2. Zpulser plasma generator Solo/ Axia generates voltage pulse with voltage oscillations with frequency 10-62.5 khz. And amplitude 5-30 %. 3. The presence of voltage oscillations enhance plasma stability and ionization. 4. Voltage oscillations induced by specific operation of the Zpulser plasma generator. 5. The presence of the voltage oscillations is beneficial for ionization and plasma stability. 6. The separation of ignition voltage and discharge voltage significantly reduces amount of Arcs particular for reactive sputtering. 21
HIPIMS/HPPMS Plasma Generator (Zpulser Cyprium) Output voltage pulse shape Circuit diagram for Zpulser Cyperium
ton Voltage waveforms after diodes bridge toff t, µs -1200 V T T = (ton + toff) f = 1/(ton + toff) micro pulse Voltage waveform after LC circuit, output voltage pulse -1100 V T PULSE Voutput = βd D = ton/(ton + toff) 3µs< ton <18µs 6µs< toff <1000µs f is in the range of 10-62.5 khz 23
Voltage waveform after LC circuit, output voltage pulse + V Voffset > 0 V t + V -1100 V T Voffset < 0V PULSE Voutput = βd D = ton/(ton + toff) t 3µs< ton <18µs 6µs< toff <1000µs f is in the range of 10-62.5 khz 24
Magnetron Discharge Afterglow (1) T e, N e T afterglow T (duty cycle) T T afterglow ~ 10 50 µs T (duty cycle) ~ 10000 µs t, µs T (duty cycle) >> T afterglow (HPPMS, HIPIMS) T (duty cycle) T afterglow? 200 µs 200 µs U = 2000 V U = 2000 V 25
T e, N e Magnetron Discharge Afterglow (2) T (duty cycle) T afterglow? T (duty cycle) ~ 5-500 µs? T afterglow t, µs U = 2000 V U = 2000 V 26
Cyprium Pulse Plasma Generator (3) 1. New High Power Pulse Plasma Generator was developed. 2. Pulse duration (voltage oscillation) is in the range of 5-20 µs. 3. Output voltage up to 1700 V, peak power 1.2 MW. 4. Voltage oscillations amplitude (40-100 %), control of rise time, fall time and frequency. ID, A VD, V 27
Plasma Generator (4) (Cyprium plasma generator) Vd Id -1100 V 28
Voltage and Current Waveforms for Cu Discharge (1) (Cyprium plasma generator) I,(A) U, (V) 25 µs f2 f1 Influence of voltage oscillations frequency on discharge current (f1 = 12241 khz, f2 = 41667 khz) 29
Voltage and Current Waveforms for Cu Discharge (2) (Cyprium plasma generator) 1050 A 150 A -800 V I d = I d (frequency, khz) Zond/Zpulser
Voltage Current Characteristic for Cu Discharge. (Cyprium plasma generator) Discharge Current, A 500 400 300 200 100 0 f2 f1 0 500 1000 1500 2000 Ppeak = 540 kw (~ 7 kw/cm 2 ) Discharge Voltage, V (f1 = 12241 khz, f2 = 41667 khz) 31
Voltage and Current Waveforms for C Discharge (Solo and Cyprium plasma generators) ~30 A ~200 A ~800 V ~520 V (1) Solo plasma generator (2) Cyperium plasma generator Deposition Rate ~ 7.5 µm/hour (1250 Å/min), P average = 5kW, Hardness ~ 40 GPa (different conditions) 32
Voltage and Current Wave forms for single oscillation 200 A -1000 V - 1700 V Zond/Zpulser
Ar = 100 sccm O2 = 0 sccm Reactive Sputtering of Al 2 O 3 films (Cyprium plasma generator) ~ 100 A ~900 V Intensity, counts/sec 200 150 100 50 Al + 390.06 nm Al 394.4 nm O2 = 0 sccm 0 390 395 400 λ, nm Al 396.15 nm O2 = 8 sccm O2= 14 sccm Ar = 100 sccm O2 = 8 sccm ~100 A ~800 V Ar = 100 sccm O2 = 15 sccm ~ 140 A ~760 V P peak ~105 kw (1.5 kw/cm 2 ) V peak ~ - 760 V I peak ~ 140 A Deposition rate ~13 µm/hour
CONCLUSION (1) 1. Zpulser plasma generator Cyperium generates multi frequency negative voltage oscillations with controllable voltage rise, duration and amplitude in one pulse. 2. Zpulser plasma generator Cyperium generates voltage pulse with voltage oscillations with frequency 10-62.5 khz. And amplitude 30-100 %. 3. The presence of the voltage oscillations is beneficial for ionization and plasma stability. 4. Maximum output voltage 1700 V, current 550 800 A, average power 22 kw. Perfect for high power pulse reactive nitride/ oxide magnetron sputtering processes 35
CONCLUSIONS (2) 1. High Power Pulse Magnetron Technology the most cost effective method to generate ions. 2. Three different high power pulse plasma generators: Thank you for your attention 36