Chemical Vapor Deposition of Ru and Its Application in (Ba,Sr)TiO₃ Capacitors for Future Dynamic Random Access Memories

Abstract

Ru films were fabricated by chemical vapor deposition using Ru(C 5 H 5 ) 2 and O 2 . The deposition of Ru film was controlled by the surface reaction kinetics as the rate limiting step with activation energy of 2.48 eV below 250 • C and by the mass transport process above 250 • C. Ru films had a polycrystalline structure and showed low resistivity of about 12 µ cm. Ru films deposited at 230 • C showed excellent step coverage. We applied Ru films prepared by chemical vapor deposition to the bottom electrode of a Ba 0.25 Sr 0.75 TiO 3 capacitor and obtained good electrical characteristics.

Ruthenium Thin Films Grown by Atomic Layer Deposition

“…Increased surface roughness with increasing deposition temperature and film thickness has also been reported for ruthenium films grown by CVD. [2] The results from the TOF-ERDA indicated that the films were very pure. The impurity content of the ruthenium films grown at temperatures of 300 C, 350 C, and 400 C is shown in Table 1.…”

“…CVD is preferred in applications where high conformality of the films is needed. Precursors such as RuCp 2 [2,16,17] (Cp = cyclopentadienyl), Ru(acac) 3 [17,18] (acac = acetylacetonate), Ru-(thd) 3 [19] (thd = 2,2,6,6-tetramethyl-3,5-heptanedionate), Ru(hfb)(CO) 4 [20] (hfb = hexafluoro-2-butyne), and Ru 3 -(CO) 12 [17] are, for example, available for the CVD of ruthenium thin films. However, these precursors are not ideal for CVD due to their high melting points.…”

“…The deposited ruthenium metal itself is not oxidized during the process. Oxygen-containing gas mixtures are commonly used oxidants in respective CVD processes, [2,19,21,22] and thus they might also work in ALD even though, in ALD oxide studies, oxygen has been found to be too inert to react with most of the metal precursors. [26] For the ruthenium precursor, sufficient thermal stability and high reactivity with oxygen are the most critical requisites.…”

Ruthenium Films Deposited by Liquid‐Delivery MOCVD Using Bis(ethylcyclopentadienyl)ruthenium with Toluene as the Solvent

“…Although the deposition of Ru films by MOCVD is documented in the literature, [7,[9][10][11][12][13][14][15][16][17][18][19][20] the development of an MOCVD process for large-scale manufacture is primarily restricted by the availability of a suitable precursor, which needs to be highly volatile, thermally stable, and inexpensive. For example, it was reported [9] that Ru films prepared using bis(cyclopentadienyl)ruthenium (Ru(Cp) 2 ) showed low resistivity, small tensile stress, and excellent step coverage.…”

Effects of an Added Iodine Source (C2H5I) on Ru Metal–Organic Chemical Vapor Deposition

“…New high-dielectric constant materials, such as tantalum pentoxide (Ta 2 O 5 ), [1,2] and barium strontium titanate [(Ba,Sr)TiO 3 ], [3,4] are expected to be used as capacitor materials for gigabit-generation dynamic random access memory (DRAM) devices. Ru is used as an electrode for these dielectric materials due to its dry etchability and high conductivity under oxidizing conditions.…”