Balance of power delivered

Views:
 
     
 

Presentation Description

Presented at RSD2011: International Conference on Reactive Sputtering Deposition, December 8-9, 2011 Linköping, Sweden. Bipolar pulsed reactive sputtering is a useful technique for deposition of dielectric films like Al2O3. The power balance of both magnetrons is important, as it can influence both the film thickness homogeneity of and film composition. Two two-inch magnetrons have been used with Al targets in Ar/O2 gas mixture for rea ... Shared on http://www.vacuumcoating.info

Comments

Presentation Transcript

Balance of power delivered to magnetrons in bipolar pulsed sputtering of aluminum oxide in high frequency mode and HIPIMS : 

Balance of power delivered to magnetrons in bipolar pulsed sputtering of aluminum oxide in high frequency mode and HIPIMS Stanislav Kadlec and Jiří Vyskočil HVM Plasma Ltd. Prague, Czech Republic 12/15/2011 1 RSD 2011

Bipolar magnetron sputtering : 

Bipolar magnetron sputtering Useful for reactive sputter deposition of dielectric layers Solves disappearing anode problems Strongly reduces arcing 12/15/2011 RSD 2011 2

Motivation : 

Motivation Bipolar pulsed reactive sputtering is a useful technique for deposition of dielectric films like Al2O3. The power balance of both magnetrons can influence film thickness homogeneity film composition Information on the power balance is important 12/15/2011 3 RSD 2011

Equipment : 

Equipment Sputtering system Flexilab HVM design Three 2-inch magnetrons with shutters DC, pulsed or RF sputtering RF or DC biased substrate holder (20 – 450°C) Load- lock Turbopump 230l/s 12/15/2011 4 RSD 2011

Devices : 

Devices 5kW DC Power supply Hüttinger MP5 bipolar pulsing unit MAGPULS BP 1000/100/200 Current peak rated up to 200A Frequency up to 100kHz ON and OFF times 2µs to 100 ms Oscilloscope Tektronix TDS2024B Differential Voltage probe P5200A AC current probe P6021 DC/AC current probe A622 Total pressure gauge 10 Pa Pfeifer CMR 375 12/15/2011 5 RSD 2011

Electric Wiring : 

Electric Wiring 12/15/2011 RSD 2011 6 5kW DC MP5 Pulse Generator - UDC + Mag1 Mag2 Switch U1 (V) I (A) U1 (V)

Pulsed sputtering with Magpuls power supply : 

Pulsed sputtering with Magpuls power supply Two Al Targets Equal B field Unequal B field Ar + O2 gas mixture Power typically 200 to 400W Voltages 300 to 700 V Power or voltage regulation on DC Power supply Hüttinger MP5 Bipolar operation – 2 Al cathodes 12/15/2011 7 RSD 2011

Operation regimes : 

Operation regimes High-frequency regime frequency range 10 to 100 kHz high on-times (5-50µs) low off-times. (2-20µs) The peak current below 1A (at 250W average power) HIPIMS regime low frequency range 1 to 10 kHz short on-times (10-100µs) high off-times (100-500µs) The peak current up to 10 A (at 250W average power) peak power density about 350 W/cm2 (entire target area) 12/15/2011 RSD 2011 8

High-frequency regime Hysteresis : 

High-frequency regime Hysteresis 12/15/2011 RSD 2011 9 Stable reactive working point in transition mode by voltage regulation PowerRegulation ↓ Hysteresis Metallic Reactive Transition

Power balance : 

Power balance Relative ON time 1: ON1/(ON1 + ON2) Relative Power 1:P1 / (P1 + P2) Powers P1, P1 are obtained by integration from osciloscopic data: 12/15/2011 RSD 2011 10 Effects of relative ON time

High-frequency regime Power Balance : 

High-frequency regime Power Balance 12/15/2011 RSD 2011 11 Pure Metallic Mode – Ar sputteringON1 + ON2 = 40µs, OFF1=OFF2 = 5µs, T=50µs Approx. equal increase asON Time Ratio

High-frequency regime Power Balance with O2 : 

High-frequency regime Power Balance with O2 12/15/2011 RSD 2011 12 Near transition mode power gets more balanced Closest power balance ON1 = 22µs, ON2 = 18µs, OFF1=OFF2 = 5µs

Pulse shapes HIPIMS : 

Ar sputtering 350W, OFF1 = OFF2 = 275µs T=600µs Pulse shapes HIPIMS 12/15/2011 RSD 2011 13

Current shapes HIPIMS : 

Current shapes HIPIMS Ar sputtering 350W, as function of ON1 time (µs) total ON1+ON2 = 50 µs OFF1 = OFF2 = 275 µs 12/15/2011 RSD 2011 14

Power balance : 

Power balance 12/15/2011 15 RSD 2011 Ar sputtering 350W, as function of ON1 time (µs) total ON1+ON2 = 50 µs OFF1 = OFF2 = 275 µs Power increase faster than ON Time Ratio Unequal Power at balanced ON Times

Current shapes reactive HIPIMS : 

Current shapes reactive HIPIMS Ar +O2 sputtering , U=650V, as function of ON1 time (µs) total ON1+ON2 = 50 µs OFF1 = OFF2 = 275 µs 12/15/2011 RSD 2011 16

Power balance : 

Power balance 12/15/2011 17 RSD 2011 Ar +O2 sputtering , U=650V, as function of ON1 time (µs) total ON1+ON2 = 50 µs OFF1 = OFF2 = 275 µs Slower Power Increase than ON Time Ratio Point of Equal Power is shiftedON Times

Reactive HIPIMS : 

Reactive HIPIMS 12/15/2011 RSD 2011 18 Ar +O2 sputtering 350W ON1= 30µs , ON2 = 20µs OFF1 = OFF2 = 275 µs Metallic Mode Transition Mode Closest power balance in transition mode Worse power balance in metallic mode than in pure Ar

Two unequally strong magnetrons : 

Two unequally strong magnetrons 12/15/2011 RSD 2011 19 Reactive mode more power in the weaker magnetron 1.2A Metallic mode More power in the stronger magnetron 0.48A

Equalizing the power balance : 

Equalizing the power balance Negative feedback on the power balance in the transition regime: When one magnetron has less power → it gets more oxidized→ faster current rise → finally better power balance The negative feedback seems to be stronger for HIPIMS than for the high-frequency regime The reason may be plasma re-ignition with longer delay in case of HIPIMS. 12/15/2011 20 RSD 2011

Summary : 

Summary Balance of power delivered to both magnetrons in reactive bipolar sputtering depends on The on-times of both magnetrons The oxygen partial pressure The frequency regime With symmetrical pulsing, higher current and power is often observed in one magnetron (due to slight difference in the magnetic field strength) The resulting unequal power dissipation can be compensated by unequal ratio of on-times. The Al – O2 system has a tendency to equalize the power balance in the transition mode, especially in the HIPIMS regime. 12/15/2011 21 RSD 2011

authorStream Live Help