Prodyut Majumder

Investigation on the diffusion barrier properties of sputtered Mo∕W–N thin films in Cu interconnects

Mo∕W–N bilayer thin film structures deposited on Si using sputtering have been studied as a copper diffusion barrier. The thermal stability of the barrier structure after annealing Cu∕Mo∕W–N∕⟨Si⟩ samples in N2 for 5min is studied using x-ray diffraction (XRD), scanning electron microscopy/energy dispersive spectroscopy, and four point probe measurements. The failure of the barrier structure is indicated by the abrupt increase in sheet resistance value and the formation of Cu3Si phase as probed by XRD. Our results suggest that the Mo (5nm)∕W–N (5nm) barrier is stable and can prevent the formation of Cu3Si at least up to 775°C.

Atomic Layer Deposition of Y2O3 Films on Silicon Using Tris(ethylcyclopentadienyl) Yttrium Precursor and Water Vapor

Yttrium oxide films are deposited on silicon using a new precursor, tris(ethylcyclopentadienyl) yttrium with water vapor as the oxidizer, by means of atomic layer deposition (ALD). Film growth kinetics has been examined under different reactor conditions, and growth saturation is evident from precursor dosage dependence. The film thickness increases linearly with the number of deposition cycles, yielding a growth rate of 1.7 ± 0.1 A/cycle at optimal ALD conditions. Increasing the reactor temperature from 200 to 400°C shows gradual increase in growth rate, with a narrow temperature plateau in the range of 250-285°C. X-ray photoelectron spectral analysis of Y 2 O 3 films indicates the film to be stoichiometric with no evidence of carbon contamination, whereas glancing incidence X-ray diffraction data of as-deposited Y 2 O 3 suggests the film structure to be polycrystalline.

Structural phase transformation of Y2O3 doped HfO2 films grown on Si using atomic layer deposition

HfO2 and Y2O3 films, along with Y2O3-doped HfO2 composite films, have been deposited on Si by means of atomic layer deposition (ALD) using tetrakis(diethylamino)hafnium and tris(ethylcyclopentadienyl)yttrium with water vapor as the oxidizer. The growth rate and structural properties of these films have been investigated by spectral ellipsometry, grazing incidence x-ray diffraction, and x-ray photoelectron spectroscopy (XPS). The film growth temperature dependence of both HfO2 and Y2O3 films indicate overlapping ALD windows in the 250–285°C region, which is critical for ALD of Y2O3-doped HfO2 films. The composition of such films is controlled by altering precursor cycle ratios, and XPS analyses of the resulting films indicate strong correlation between the precursor cycle ratio and the film composition. From structural analyses, the as-deposited HfO2 was found to be amorphous but after annealing at 600°C or higher, it became monoclinic. In contrast, all Y2O3 films whether annealed or not had evidence of cu...

Atomic Layer Deposited Ultrathin HfO2 and Al2O3 Films as Diffusion Barriers in Copper Interconnects

Atomic layer deposited ultrathin HfO 2 and Al 2 O 3 films were studied as diffusion barriers between Cu and Si substrate. The thermal stability of 3 nm thick HfO 2 and Al 2 O 3 films was investigated after annealing at different temperatures for 5 min in N 2 . X-ray diffraction analyses and sheet resistance measurements suggest that both barrier films were thermally stable and the formation of Cu 3 Si started to take place only after annealing at high temperatures. Specifically, our results show that 3 nm thick HfO 2 and Al 2 O 3 diffusion barriers break down after annealing in N 2 at 700 and 750°C, respectively.

Reactively Sputtered Mo–V Nitride Thin Films as Ternary Diffusion Barriers for Copper Metallization

The effectiveness and performance of Mo-based ternary nitride films as copper diffusion barriers were investigated. Thermally stable Mo-V nitride thin diffusion barrier layers were deposited using radio frequency reactive magnetron sputtering and their barrier capability was evaluated and studied. Cu/Mo-V nitride/Si structures were fabricated and annealed at different temperatures. The agglomeration of Cu and the formation of Cu 3 Si due to high-temperature annealing were probed using scanning electron microscopy/energy-dispersive X-ray spectroscopy. The drastic increase in sheet resistance after annealing at 800°C was found to take place due to the formation of highly resistive Cu 3 Si, also evident from X-ray diffraction patterns. The formation of inverted pyramidal structure of Cu 3 Si at the interface penetrated into the Si substrate corroborated the breakdown of the barrier layer at 800°C. Our results suggest that an 8 nm thick Mo-V nitride barrier can effectively prevent the formation of Cu 3 Si up to high annealing temperatures.

Composition–Structure–Dielectric Property of Yttrium-Doped Hafnium Oxide Films Deposited by Atomic Layer Deposition

Sequential atomic layer deposition was used to deposit yttrium-doped hafnium oxide films with variable yttrium content using tris(ethylcyclopentadienyl) yttrium and tetrakis(diethylamino) hafnium as metal precursors and water vapor as the oxidizer. The structure and electrical properties of the resulting films were analyzed after different postdeposition annealing conditions to assess composition-structure-dielectric property relationships. The 2.5-100% yttrium-doped films annealed above 600°C for 5 min consistently yielded cubic-HfO 2 structures. However, there was a strong compositional effect on the dielectric constant, which maximized at ∼14% yttrium content. The films studied had a leakage current density of 10 -5 A/cm 2 or less at 1 V.

Evaluation and Testing of Organometallic Precursor for Copper Direct-Write

A capillary bridge printing technique has been used to deposit copper interconnects using homogeneous solutions of a Cu(II) precursor in a series of low boiling primary alcohols. The rheological properties of the solutions have been measured first to determine their printability. The as-printed lines with subsequent annealing at relatively low temperatures (∼200 °C), in order to evaporate the volatile solvents and facilitate dissociation of the precursor deposit, produced conducting interconnects. The precursor has been demonstrated to be self-reducing and requires no reducing environment (e.g. H 2 ) thus making the interconnect formation easier. Moreover, successful decomposition of the precursor into metallic Cu at such low temperatures holds promise for applications involving flexible polymer substrates.