Growth of Atomic Layer Deposited Ruthenium and Its Optical Properties at Short Wavelengths Using Ru(EtCp)2 and Oxygen

Abstract

High-density ruthenium (Ru) thin films were deposited using Ru(EtCp)2 (bis(ethylcyclopentadienyl)ruthenium) and oxygen by thermal atomic layer deposition (ALD) and compared to magnetron sputtered (MS) Ru coatings. The ALD Ru film growth and surface roughness show a significant temperature dependence. At temperatures below 200 °C, no deposition was observed on silicon and fused silica substrates. With increasing deposition temperature, the nucleation of Ru starts and leads eventually to fully closed, polycrystalline coatings. The formation of blisters starts at temperatures above 275 °C because of poor adhesion properties, which results in a high surface roughness. The optimum deposition temperature is 250 °C in our tool and leads to rather smooth film surfaces, with roughness values of approximately 3 nm. The ALD Ru thin films have similar morphology compared with MS coatings, e.g., hexagonal polycrystalline structure and high density. Discrepancies of the optical properties can be explained by the higher roughness of ALD films compared to MS coatings. To use ALD Ru for optical applications at short wavelengths (λ = 2–50 nm), further improvement of their film quality is required.

Structure and Electrical Behavior of Hafnium-Praseodymium Oxide Thin Films Grown by Atomic Layer Deposition

“…In nanoelectronics, ruthenium (Ru), as a noble metal with a high work function, has been of interest and studied as an electrode material of dynamic random access memory capacitors [ 37 , 38 , 39 , 40 ] with high permittivity dielectrics and very high capacitance density values [ 37 ]. Ru has also been applied as an electrode material of RS stacks [ 41 , 42 , 43 ].…”

Plasma Enhanced Atomic Layer Deposition of Ruthenium Films Using Ru(EtCp)2 Precursor

“…For example, it acts as a catalyst in Fischer Tropsch [13] and ammonia decomposition reactions [14,15]. Thin ruthenium films are also essential for soft X-ray [16][17][18] and extreme ultraviolet (EUV) optics [18,19]. To a large extent, considerable interest in ruthenium can be explained by comparably low prices for this noble metal.…”

“…A lot of organometallic precursors have been developed for ruthenium deposition [32]. The most frequently used precursors are bis(cyclopentadienyl)ruthenium(II) (or RuCp 2 ) [25,33] and bis(ethylcyclopentadienyl)ruthenium(II) (or Ru(EtCp) 2 ) [8,18,34]. Ru(EtCp) 2 is a relatively inexpensive, commercially available liquid precursor.…”

“…Moreover, a wide variety of co-reactants can be selected for Ru(EtCp) 2 , such as O 2 [6,33], O 3 gases [8], and NH 3 plasma [33]. Using Ru(EtCp) 2 , it is possible to get high density (12.3 g•cm −3 ) [18] ruthenium thin films with low surface roughness (0.9 nm) and low resistivity (up to 16 µOhm•cm) [33].…”

Optical detection of hydrogen diffusion through thin film barrier materials

“…If we assume that transport along grain boundaries is the dominating diffusion mechanism, this justifies the usage of CPd H /dRu as approximation of the concentration gradient over the diffusion pathways through the Ru film. It has been demonstrated that our 7 nm Ru films are above the threshold thickness for polycrystalline growth [40,41]. We therefore expect that diffusion will be dominated by hopping between defects or transport along grain boundaries.…”