Area-Selective Atomic Layer Deposition of Platinum on YSZ Substrates Using Microcontact Printed SAMs

Abstract

Using ͑methylcyclopentadienyl͒trimethylplatinum ͑MeCpPtMe 3 ͒ and oxygen as precursors, Pt has been deposited by atomic layer deposition ͑ALD͒ on the surfaces of yttria-stabilized zirconia ͑YSZ͒, a solid oxide electrolyte, as well as on oxide-covered silicon. Ex situ analyses have been carried out to examine the properties of both as-deposited and postannealed Pt films. X-ray photoelectron spectroscopy measurements demonstrate that there are no detectable impurities in the as-deposited Pt films, and four-point probe measurements show that the resistivity for a 30.2 nm film is as low as 18.3 ⍀ cm. The use of area-selective ALD to deposit patterned Pt has also been investigated. By coating these same substrates with octadecyltrichlorosilane ͑ODTS͒ selfassembled monolayers ͑SAMs͒, Pt ALD can be successfully blocked. Furthermore, it is shown that by transferring the ODTS SAMs to the substrates by microcontact printing ͑CP͒ using patterned stamps, platinum thin films are grown selectively on the SAM-free surface regions. Features with sizes as small as 2 m have been deposited by this combined ALD-CP method; the resolution is limited by the printed pattern and, likely, can be achieved at dimensions significantly smaller than a micrometer.

Remote Plasma ALD of Platinum and Platinum Oxide Films

“…Pt growth on these substrates could only be achieved by using a higher O 2 pressure ͑Ͼ0.8 mbar͒ as also typically used in the literature. 1,3 On the contrary, remote plasma ALD of Pt ͑0.5 s O 2 plasma͒ leads to immediate growth without a substantial nucleation delay. From the ellipsometry measurements, which have a reduced accuracy in the first 1-2 nm, it is concluded that growth per cycle is constant after the first 50 cycles.…”

“…8 Material properties.-As shown in Table I both the remote plasma and thermal ALD process result in very similar material properties for the Pt films. In both cases high density ͑ϳ21 g/cm 3 ͒, low resistivity ͑ϳ15 ⍀ cm͒, and high purity Pt films were deposited. The density and resistivity for these ϳ30 nm thick films are close to the bulk values of 21.4 g/cm 3 and 10.8 ⍀ cm, and they are similar to the values reported for thermal ALD of Pt.…”

“…MeCpPtMe 3 precursor ͑98%, Sigma-Aldrich͒, heated to 70°C, was vapor drawn into the chamber. The substrates were heated to 100-300°C ͑precursor decomposition starts above 310°C͒, 3 while the reactor walls were kept at a temperature of 75°C.…”

“…[1][2][3][4][5][6][7] While being less investigated, platinum oxide is of interest because of its optical properties and because PtO x can be ͑locally͒ reduced to Pt. [8][9][10] In the research efforts toward the applications of these films deposited by ALD, nucleation properties, material quality, and process temperature window are of key importance.…”

“…2,3 This process relies on the dissociative chemisorption of O 2 on the Pt surface for oxidative decomposition of the precursor ligands. 11,12 For PtO x only one ALD process has been reported, to the best of our knowledge.…”