materials ALD films
Figure 8,SEM of Pt-ALD films (cross- section of thickness and particle-size measurement)
2) increasing oxidation with the ligands of the chemisorbed precursor on the surface; and 3) increasing Pt nucleation by extra plasma energy. Pt particle-size at 50 and 100 cycles on different
metal oxide surfaces (SiO2, Al2O3 and HfO2) deposited at 300°C by thermal and remote plasma ALD also is shown in Table 2. It was found that the
Pt particle-size on HfO2 was quite big, 3.7 nm for 50 cycles and 5.6 nm for 100 cycles as compared to 1.6 nm and 2.1 nm on Si, respectively. Studies
found that high work function metals such as Pt show instability in oxygen-deficient conditions. [19] As is well known, Pt ALD process relies on the
dissociative chemisorption of O2 on the Pt surface for oxidative decomposition of the precursor ligands. [17, 18] Therefore the absorbed oxygen on surface of oxides might be a controlling step for the initial step of the Pt ALD process.
Considering Fermi level pinning in terms of oxygen vacancies, these appear to exist in sizable amounts
in HfO2 film, [20] which is named high temperature oxygen ion conductor and allows oxygen transport
across the HfO2 layer. [21, 22]. The remote plasma enhanced ALD Pt films showed bigger Pt particle-
size and a short nucleation delay on HfO2 films. Both active atomic O species generated from oxygen plasma and their absorption and diffusion
on the HfO2 surface resulted in increasing growth rate of Pt layers on the HfO2 by plasma-ALD. Conclusions
Figure 9,Growth rate and resistivity of Pt plasma-ALD layers on various
oxides.HfO2 is shown the highest growth rate and the lowest resistivity of
them.It is believed that surface functionalisation by plasma-ALD and rich- absorbed oxygen radicals on HfO2 surface are the reasons
18
www.siliconsemiconductor.net Issue III 2012
Platinum films were deposited by both remote plasma and thermal atomic layer deposition (ALD) using methylcyclopentadienyl- trimethyl platinum
(MeCpPtMe3) and O2 as precursors on oxide materials. The ALD Pt-films deposited were
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40