ON HIGH POWER IMPULSE MAGNETRON SPUTTERING
ON HIGH POWER IMPULSE MAGNETRON SPUTTERING ON HIGH POWER IMPULSE MAGNETRON SPUTTERING
elative intensity of Ar [a.u.] 9 6 3 0 Ti - HiPIMS Cu - HiPIMS dual-HiPIMS hybrid-dual-HiPIMS dual-HiPIMS: f = 100 Hz T a = 100 s T d = 15 s HF discharge: f = 94 kHz T a = 3 s T d = 7 s p = 3.0 Pa = 811.5 nm (Ar) 0 100 200 300 time [ s] relative intensity Ti [a.u] 7 Ti - HiPIMS Cu - HiPIMS 6 5 4 3 2 1 0 Ti, hybrid-DH Ti, DH Cu, hybrid-DH Cu, DH dual-HiPIMS: f = 100 Hz T a = 100 s T d = 15 s HF discharge: f = 94 kHz T a = 3 s T d = 7 s p = 3.0 Pa = 327.4 nm (Cu) = 453.3 nm (Ti) 0 100 200 300 time [ s] 22 19 15 11 7 4 0 relative intensity Cu [a.u.] Fig. 3.7: Time resolved optical emission measurements of Ar line λ Ar = 811.5 nm. Fig. 3.8: Time resolved optical emission measurements of λ Cu = 327.4 nm and λ Ti = 453.3 nm. the electrons. In this way the deposition rate on the substrate is reduced and the anode can be contaminated (covered) by the cathode material [VII]. Hence, some fraction of Ti vapour is deposited on the inactive Cu anode during the Ti-HiPIMS pulse and it has to be sputtered first at the beginning of the (second) Cu-HiPIMS pulse (and vice-versa for reversed polarity of Ti-Cu electrodes). The second source of the emission observed might be represented by ions still persisting in the cathode vicinity from previous pulse when it served as anode (see the explanation given above). A more probable explanation is the first one, based on target contamination. The reasons are as follows: A well-pronounced emission of different materials at the beginning of HiPIMS pulses is observable only for dual-HiPIMS mode despite the fact that the intensity of Cu emission at the beginning of the Ti pulse is much lower, see Fig.3.8 (this effect corresponds with the low sensitivity of the iCCD chip which is needed for measurement of massive sputtering during the Cu-HiPIMS pulse). When the hybrid dual- HiPIMS discharge is operated, the emission of only Ti is observed during Cu-HiPIMS. The absence of Cu emission at the beginning of the Ti-HiPIMS pulse is caused by the operation of an MF-discharge in the idle time of HiPIMS pulses which provides a "cleaning effect". To study the discharge expansion dynamics and target contamination, the fast optical emission imaging was employed [IV,VIII]. Images for both Ti-driven (right side of images) and Cu-driven (left side of images) discharges in hybrid-dual-HiPIMS configuration are shown in Fig.3.9. The total light emission 5 is presented in Fig.3.9. The Ti-pulse is ignited first (T a =0µs) and the emission in the vicinity of Ti target is immediately detected. This 5 Measurements with optical filters for particular (Ar, Ar + , Ti, Ti + , Cu, Cu + ) wavelengths were also done to verify the origin of imaged light emission. The function of automatic iCCD chip sensitivity adjustment was activated during all recording of time-resolved image sequences since the emission intensity dynamically varies in time. In other words, the iCCD chip sensitivity was adjusted automatically by the gain (G=1-255) of the amplifier to obtain optimal images. 24
A G = 233 T = 13 s Ti-HiPIMS pulse B G = 31 T = 64 s Ti-HiPIMS pulse C G = 255 T = 109 s HiPIMS pulse delay D G = 240 T = 123 s Cu-HiPIMS pulse D G = 180 T = 171 s Cu-HiPIMS pulse E G = 255 T = 276 s Ti-MF pulse F G = 255 T = 280 s Cu-MF pulse Fig. 3.9: Time resolved images of Ti-Cu hybrid-dual- HiPIMS discharge. Images: A and B - Ti HiPIMS pulse (0 - 100µs), C - delay between pulses (100 - 115µs), D and E-Cu HiPIMS pulse (115 - 215µs), F-MF pulse of Ti, G - MF pulse of Cu (MF driven in the idle time of HiPIMS). Ti magnetron is shown on the right and Cu on the left-hand side of images, respectively. The gain of iCCD amplifier G was automatically varied in range 0 - 255. light is mostly produced by Ar ∗ (verified by measurements with optical filters and measurements with OES). However, after a few microseconds, T a ∼1-3µs, visible emission in neighborhood of Cu electrode is observed as well. It becomes more pronounced in the vicinity of Cu-target and creates well-defined bond between Cu (anode) and Ti (cathode), Fig.3.9 A. This effect is due to magnetic (reversed polarity of magnets) and electric (anode-cathode) confinements. Electrons, repelled from the cathode ϕ Ti ≃-800V (Fig.2.6), move along the magnetic field line towards the anode, due to |ϕ Ti - ϕ Cu | ∼ 800 V, and cause electron impact ionization of Ar gas. Apparent bonding between electrodes is somewhat similar to the edge of a virtual tubular-like anode of dual magnetron system. However, bounding between sputtering sources, represented by emission of Ar ∗ and Ar + , between electrodes disappears after full propagation of the Ti-HiPIMS pulse, see Fig.3.9 B. This is not true because the emission of sputtered Ti gradually exceeds the intensity of Ar ∗ and Ar + lines and the sensitivity of iCCD chip is automatically decreased. After 25- 30µs, massive sputtering of Ti is dominant and a larger cloud is formed nearby Ti target. The cloud, formed mainly by neutral Ti and Ar (with some fraction of Ar + and Ti + ), propagates downwards with a speed roughly about 2-3mm/µs. Measured speed some- 25
- Page 1 and 2: University of South Bohemia Faculty
- Page 3: Acknowledgements I am happy that I
- Page 6 and 7: Preface Plasma physics and plasma b
- Page 8 and 9: lished in the same year. Such expan
- Page 10 and 11: So far, no official definition of H
- Page 12 and 13: the cathode voltage [48, 49]. The s
- Page 14 and 15: 2. HiPIMS power supplies and discha
- Page 16 and 17: For dc-MS discharges, n takes on hi
- Page 18 and 19: 100 s V Ti HiPIMS V MF pulsed C p R
- Page 20 and 21: cathode (Cu) relative to the ground
- Page 22 and 23: scale. The Electron Energy Probabil
- Page 24 and 25: collision frequency. For such a hig
- Page 26 and 27: high energy electrons dominate in b
- Page 30 and 31: what corresponds with the diffusion
- Page 32 and 33: estimated from the model can be dem
- Page 34 and 35: energy [eV] 20 10 0 Ti-HiPIMS ON Cu
- Page 36 and 37: On the other hand, the presence of
- Page 38 and 39: To be more specific, let suppose th
- Page 40 and 41: Despite relatively large error the
- Page 42 and 43: can be obtained from amorphous TiO
- Page 44 and 45: Fig.4.4 presents band-gap energy E
- Page 46 and 47: thermal instability [147-151], and
- Page 48 and 49: Thus it is assumed that x-ray amorp
- Page 50 and 51: Table 4.2: Cu domain sizes [nm] cal
- Page 52 and 53: and dual-MS in not total, but that
- Page 54 and 55: a high diffusion rate of copper spe
- Page 56 and 57: 2 1.8 1.6 AFM data A log−normal:
- Page 58 and 59: mass of clusters m CM [amu] Q 4x10
- Page 60 and 61: References [1] R. Hippler, H. Kerst
- Page 62 and 63: [80] S.A. Voronin, G.C.B. Clarke, M
- Page 64 and 65: [165] B. Holmberg, Acta Chemica Sca
A<br />
G = 233<br />
T = 13 s<br />
Ti-HiPIMS pulse<br />
B<br />
G = 31<br />
T = 64 s<br />
Ti-HiPIMS pulse<br />
C<br />
G = 255<br />
T = 109 s<br />
HiPIMS pulse delay<br />
D<br />
G = 240<br />
T = 123 s<br />
Cu-HiPIMS pulse<br />
D<br />
G = 180<br />
T = 171 s<br />
Cu-HiPIMS pulse<br />
E<br />
G = 255<br />
T = 276 s<br />
Ti-MF pulse<br />
F<br />
G = 255<br />
T = 280 s<br />
Cu-MF pulse<br />
Fig. 3.9: Time resolved images of Ti-Cu hybrid-dual-<br />
HiPIMS discharge. Images: A and B - Ti HiPIMS pulse<br />
(0 - 100µs), C - delay between pulses (100 - 115µs), D and<br />
E-Cu HiPIMS pulse (115 - 215µs), F-MF pulse of Ti, G -<br />
MF pulse of Cu (MF driven in the idle time of HiPIMS). Ti<br />
magnetron is shown on the right and Cu on the left-hand<br />
side of images, respectively. The gain of iCCD amplifier G<br />
was automatically varied in range 0 - 255.<br />
light is mostly produced by Ar ∗<br />
(verified by measurements with<br />
optical filters and measurements<br />
with OES). However, after a few<br />
microseconds, T a ∼1-3µs, visible<br />
emission in neighborhood of Cu<br />
electrode is observed as well. It<br />
becomes more pronounced in the<br />
vicinity of Cu-target and creates<br />
well-defined bond between Cu (anode)<br />
and Ti (cathode), Fig.3.9 A.<br />
This effect is due to magnetic<br />
(reversed polarity of magnets)<br />
and electric (anode-cathode) confinements.<br />
Electrons, repelled<br />
from the cathode ϕ Ti ≃-800V<br />
(Fig.2.6), move along the magnetic<br />
field line towards the anode, due<br />
to |ϕ Ti - ϕ Cu | ∼ 800 V, and cause<br />
electron impact ionization of Ar<br />
gas. Apparent bonding between<br />
electrodes is somewhat similar to<br />
the edge of a virtual tubular-like<br />
anode of dual magnetron system.<br />
However, bounding between<br />
sputtering sources, represented by<br />
emission of Ar ∗ and Ar + , between<br />
electrodes disappears after<br />
full propagation of the Ti-HiPIMS<br />
pulse, see Fig.3.9 B. This is not<br />
true because the emission of sputtered<br />
Ti gradually exceeds the intensity<br />
of Ar ∗ and Ar + lines and<br />
the sensitivity of iCCD chip is automatically<br />
decreased. After 25-<br />
30µs, massive sputtering of Ti is<br />
dominant and a larger cloud is<br />
formed nearby Ti target. The<br />
cloud, formed mainly by neutral<br />
Ti and Ar (with some fraction of<br />
Ar + and Ti + ), propagates downwards<br />
with a speed roughly about<br />
2-3mm/µs. Measured speed some-<br />
25
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