AbstractA novel direct local deposition approach was developed for the deposition of platinum nanostructures that combines the material quality and the thickness control of atomic layer deposition (ALD) with the patterning capability of electron beam induced deposition (EBID). ALD is a thin film deposition technique based on sequential self-limiting half-reactions, whereas EBID is a direct-write local deposition technique that relies on electron beam induced decomposition of a precursor. Due to its excellent electrical properties Pt is an interesting material for many nanoprototyping applications such as adding electrical contacts to nanodevices. The approach chosen in this work consists of seed layer deposition by EBID followed by area-selective ALD growth. The thermal ALD process of Pt from (CH3)CpPt(CH3)3 precursor and O2 gas was extensively characterized by using in situ spectroscopic ellipsometry (SE). This process turned out to be suitable for the combinatorial EBID-ALD approach, since the thermal ALD growth could only be initiated on catalytic active Pt seed layers in case a low O2 pressure was employed. In addition, a new plasma-assisted ALD process using (CH3)CpPt(CH3)3 precursor and O2 plasma was developed which offered several merits compared to the thermal ALD process such as a reduced growth delay, the possibility to deposit high-purity Pt at low substrate temperatures, and the ability to deposit PtO2. A part of the work focused on obtaining a fundamental understanding of the reaction mechanisms of the ALD processes and of the mechanism of selective ALD growth on EBID seed layer material. The thermal ALD growth was found to start selectively on an EBID seed layer of only a few nanometers thick, which demonstrates the feasibility of the combinatorial EBID-ALD approach for the deposition of local Pt structures. A method for thickness determination of microscale deposits was developed based on energy dispersive X-rays spectroscopy (EDX) which was used to characterize the dependence of the ALD growth on the seed layer properties. It was established that the deposits have a uniform thickness and a high purity value (>93%), whereas the method has the potential to achieve sub-10 nm lateral dimensions. Especially the high-purity of the Pt nanostructures that can be achieved with this novel approach is a major improvement compared to the 16 at.% purity that can be obtained by the EBID process of Pt to date.
|Date of Award||30 Apr 2009|
|Supervisor||Harm C.M. Knoops (Supervisor 1), J.J.L. Mulders (External coach) & W.M.M. (Erwin) Kessels (Supervisor 2)|
Atomic layer deposition of Pt and its combination with electron beam induced deposition for the fabrication of nanostructures
Mackus, A. J. M. (Author). 30 Apr 2009
Student thesis: Master