Title. Depositing Aluminium Oxide to study reactive magnetron sputtering

Transcription

1 Title to study reactive magnetron sputtering Leroy W.P. 1, Li X.Y. 2, Mahieu S. 1, Depla D. 1, De Gryse R. 1 1 Department of Solid State Sciences, Ghent University, Krijgslaan 281/S1, 9 Gent, Belgium 2 Department of Physics, Taiyuan University of Technology, 24 Taiyuan, China contact: Wouter.Leroy@UGent.be Leoben - 6 December 27

2 Rotating cylindrical magnetron 1 Main difference/advantage to planar magnetrons: position of the race track on the target surface changes with time higher target consumption target surface processes happening outside the race track also have an influence on the target poisoning mechanism

3 Discharge voltage during sputtering 2 Al -target No rotation of the target metallic mode: high voltage poisoned mode: low voltage critical point on removal: 1.5 sccm critical point on addition: 2.1 sccm

4 Sputter cleaning experiment 3 No rotation Exp. A Exp. B 2 sccm Ar 2.5 sccm O 2 (poisoned mode) 2 min at constant current (.4A) No rotation 2 sccm Ar 1.8 sccm O 2 (metallic mode) O 2 OFF Discharge OFF Pumping O 2 away (ca. 5s) 7.5 RPM.3 Pa Ar No O 2 Constant current (.4A) Voltage registration from start of rotation 2 min at constant current (.4A) time

5 Discharge voltage ifo time 4 Both go back to full metallic mode after a certain, but different time Different peak heights Exp. A sccm discharge voltage (V) Exp. B sccm time (s) 4 5

6 Exp. A sccm O 2 in detail 5 Discharge Voltage (V) Discharge Voltage (V) Time (s) Time (s) Repetition of 4 peaks Tops and Bottoms are gradually increasing 6 65

7 Discharge Voltage (V) Exp. B 1.8 sccm O 2 in detail 6 1 Discharge Voltage (V) Time (s) Repetition of 4 peaks Some of the Tops (n 1) are always at high voltage Bottoms gradually increase 55 Time (s) 6 65

8 Comparison of Sequence sccm O sccm O 2 peak 1 peak 2 peak 3 peak 4 round 13 peak 1 peak 2 peak 3 peak 4 round 11 round 29 round 27 discharge voltage (V) 25 round 9 round 7 round 5 round 3 round 1 discharge voltage (V) 25 round 25 round 23 round 21 round 19 round 17 round 15 round 13 round 11 round 9 round 7 round time (s) time (s) where do the peaks and the difference in peaks originate from?

9 both preconditioned spots in the race track Target Positions 8 one preconditioned spot in the race track both preconditioned spots out of the race track

10 Correlation position peak sccm O sccm O 2 pre-conditioned spots: poisoned mode pre-conditioned spots: metallic mode voltage for position 1: starting from low (poisoned) going to high ifo time voltage for position 1: always high (metallic) peak 1 peak 2 peak 3 peak 4 peak 1 peak 2 peak 3 peak 4 r o u n d 1 3 ro un d 29 3 discharge voltage (V) 2 5 r o u n d 1 1 r o u n d 9 r o u n d 7 r o u n d 5 r o u n d 3 r o u n d 1 3 discharge voltage (V) 2 5 ro und 27 ro und 25 ro und 23 ro und 21 ro und 19 ro und 17 ro und 15 ro un d 13 r ou nd 11 r oun d 9 ro un d 7 ro un d ti m e ( s ) ti m e (s ) 6 8 1

11 Other peaks? sccm O sccm O 2 peak 1 peak 2 peak 3 peak 4 rou nd 1 3 peak 1 peak 2 peak 3 peak 4 3 rou nd ro un d 29 ro und 27 discharge voltage (V) 2 5 rou nd 9 r oun d 7 r oun d 5 r oun d 3 r oun d 1 discharge voltage (V) 2 5 ro und 25 ro und 23 ro und 21 ro und 19 ro und 17 ro und 15 ro un d 13 rou nd 11 roun d 9 ro un d 7 ro un d tim e (s ) tim e (s ) Peaks 2, 3 & 4 all start in poisoned mode Peaks 3 take less time to return to metallic mode than peaks 2/4 Behavior of peaks 2/4 is very different for different O 2 flows

12 Difference in peaks 2/ sccm O sccm O 2 discharge voltage (V) round number peak1 peak2 (peak4) peak3 discharge voltage (V) round number Behavior of peaks 2/4 is very different for different O 2 flows peak1 peak2 (peak4) peak3 Takes more time for peaks 2/4 to go to metallic mode in case of 1.8sccm O 2 Models say: race track and other parts of the target should be more severely oxidized in case of 2.5 sccm O 2

13 Rotating cylindrical magnetron 12 Main difference/advantage to planar magnetrons: position of the race track on the target surface changes with time higher target consumption target surface processes happening outside the race track also have an influence on the target poisoning mechanism deposition of material on the target?

14 Deposition experiment 13 Stationary Target.3 Pa,.4A, 2sccm Ar 1h sputtering Si-samples pasted on the target surface Afterwards: thickness of the layer which is deposited on the Si-samples, is measured

15 Thickness of deposition 14 race track There is deposition on the target! Peaks 2, 3 & 4 all start in poisoned mode The closer the position to the stationary race track, the thicker the layer Opposite to the stationary race track, there is only a very thin layer

16 Correlation position peaks 3 15 Positions with relatively thinnest compound layer Positions with relatively thickest compound layer Peaks 3 take less time to return to metallic mode than peaks 2/4

17 Correlation position peaks 2/ sccm O sccm O 2 Target sputtered in poisoned mode Low deposition rate Thin compound layer on the target Target sputtered in metallic mode High deposition rate Thick compound layer on the target It takes more time for peaks 2/4 to go to metallic mode for targets pre-conditioned in 1.8sccm O 2 than for targets preconditioned in 2.5sccm O 2 Behavior of peaks 2/4 is very different for different O2 flows

18 Conclusion 17 The behaviours of the discharge voltage in the sputter cleaning experiments are very different for an Al cylindrical target previously oxidized in oxygen flow of 2.5 sccm and 1.8 sccm. The difference can not be explained by chemisorption, implantation and knock-on which are believed to be the target poisoning mechanism for a planar target. The experimental results can be understood by including compound deposition on the target as an extra mechanism for the target poisoning.

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