Y.K Lee

The impact of layer thickness of IMP-deposited tantalum nitride films on integrity of Cu/TaN/SiO2/Si multilayer structure

Abstract This work concentrates on the diffusion barrier stability of very thin tantalum nitride films with different thickness (10, 20 and 30 nm) sputter-deposited on silicon dioxide in the Cu/TaN/SiO2/Si multiplayer structure. The impact of varying layer thickness and influence of post deposition annealing on the crystal structure, resistivity, intermixing and reactions at the interfaces were studied by using resistivity analyses, X-ray diffraction, scanning electron microscopy and Rutherford backscattering spectrometry. The results revealed that the thinner the film thickness of tantalum nitride, the more severe the reactions at the interface of copper–tantalum nitride and consumed more conductive Cu. Accelerated grain growth and/or agglomerations were also observed in all Cu surfaces. All the structures show a similar degradation process and were found to be stable up to 450°C for 35 min.

Interfacial reactions and failure mechanism of Cu/Ta/SiO2/Si multilayer structure in thermal annealing

The integrity of Cu/Ta/SiO2/Si multilayer structure under nitrogen thermal annealing has been examined by sheet resistance measurement, X-ray diffraction, scanning electron microscopy, secondary ion mass spectroscopy, Rutherford backscattering spectrometry and cross-section transmission electron microscopy analysis. According to electrical measurement it was found that Ta diffusion barrier could preserve the integrity of the Cu/Ta/SiO2/Si structure up to 650 8 Ci n N 2 for 35 min. There are two causes by which the Cu/Ta/SiO2/Si structure became degraded. One is the out diffusion Ta atoms towards the Cu film. The other factor is the formation of Cu, Ta and Cu � /Ta oxide. Hence, Cu penetration is not the only reason to cause the failure; oxidation, phase transformation and interfacial reactions are also associated problems during thermal annealing. # 2002 Elsevier Science B.V. All rights reserved.

Study of diffusion barrier properties of ionized metal plasma (IMP) deposited tantalum (Ta) between Cu and SiO2

Abstract The diffusion barrier properties of ionized metal plasma (IMP) deposited Ta between Cu and SiO 2 have been investigated in the Cu (200 nm)/Ta (30 nm)/SiO 2 (250 nm)/Si multi-layer structure. The IMP-Ta thin film shows better Cu diffusion barrier properties than CVD (chemical vapor deposition) and conventional PVD (physical vapor deposition) deposited Ta film. The thermal stability was evaluated by electrical measurement and X-ray diffraction (XRD) analysis. As a main part of thermal stability studies, the atomic intermixing, new compound formation and phase transitions in the test structure were also studied. Furthermore, a failure mechanism was also examined by XRD, scanning electron microscopy (SEM), secondary ion mass spectroscopy (SIMS) and Rutherford backscattering spectroscopy (RBS) in conjunction with electrical measurements. The 30 nm thick IMP-Ta was found to be stable up to 650°C for 35 min.

Behaviour of ionized metal plasma deposited Ta diffusion barrier between Cu and SiO2

This work investigated the diffusion barrier properties of ionized metal plasma (IMP) deposited Ta between Cu and SiO2. When Cu and Ta layers were formed by IMP sputtering, it was found that the Cu has the equilibrium f.c.c. structure with the grain size of 80 nm whereas Ta is in a metalstable tetragonal (β-Ta) form with a grain size of around 10 nm. With the help of sheet resistance measurement, X-ray diffraction, cross-section transmission electron microscope analysis, Rutherford backscattering spectroscopy, secondary ion mass spectroscopy, and scanning electron microscopy, the Ta barrier layer was observed to fail at temperature above 650°C due to the reactions among Cu, Ta and O and formation of CuxTayOz. The phase transformation of β-Ta into the stable phase (α-Ta), in the presence of Cu was encountered when annealing the sample at above 800°C. The role of oxygen was also found to be important in the phase transformation, in the reactions and it seems to have a strong effect on the thermal stability of the barrier layer.

High density diffusion barrier of ionized metal plasma deposited Ti in Al–0.5%Cu/Ti/SiO2/Si structure

The Ti layer deposited by ionized metal plasma deposition technique and the reacted region between Ti and Al–0.5%Cu, in Al–0.5%Cu/Ti/SiO2/Si structure, were characterized by scanning transmission electron microscopy (STEM) and Rutherford backscattering spectroscopy (RBS). The results indicate that the Ti layer with a column-like structure grew epitaxially in the close-packed [001] direction. This growth mechanism resulted in a high-density Ti layer in Al–0.5%Cu/Ti/SiO2/Si structure. This epitaxially grown Ti layer has anisotropic diffusion properties that can retard the diffusion of Al across the Ti layer in the initial stage of high temperature Al sputtering or reflow processes. But the column-like Ti crystals recrystallized during further processing, altered the [001] alignment of the crystals to cause the interdiffusion of Ti and Al. The reactions between Ti and Al took place subsequently and formed the intemetallic Al3Ti, Al5Ti2, TiAl, and Ti3Al layers from the surface inwards. As the diffusion of Al ...

Study of diffusion barrier properties of ternary alloy (TixAlyNz) in Cu/TixAlyNz/SiO2/Si thin film structure

Abstract The effects of aluminum (Al) incorporation on the performance of a titanium nitride (TiN) diffusion barrier were investigated up to the temperature of 1000°C in the Cu/TixAlyNz/SiO2/Si structure. The thermal stability of the structure was evaluated by using four-point probe, X-ray diffraction, and Rutherford Backscattering Spectroscopy. The Cu/TixAlyNz/SiO2/Si system retained its structure up to 1000°C. The incorporation of Al into the TixNy film modified the microstructure of the TixNy film, especially the microstructure of grain boundaries in which oxide and nitride compounds of Al and Ti were formed during thermal annealing. As a result, the fast pathways for copper (Cu) diffusion were effectively blocked by these compounds and the stability of the barrier performance was enhanced up to 1000°C.

Comparative analysis and study of ionized metal plasma (IMP)-Cu and chemical vapor deposition (CVD)-Cu on diffusion barrier properties of IMP-TaN on SiO2

Comparative study of ionized metal plasma (IMP)-Cu and chemical vapor deposition (CVD)-Cu on diffusion barrier properties of IMP-Tantalum nitride (TaN) has been investigated in the Cu(200 nm)/TaN(30 nm)/SiO2(250 nm)/Si multi-layer structure. IMP-TaN thin film shows a better metallurgical and thermal stability with IMP-Cu than CVD-Cu thin film not due to lower concentration of oxygen and carbon in Cu film, but due to the smaller grain size and lower roughness of IMP-Cu microstructure. The thermal stability was evaluated by electrical measurements, X-ray diffraction (XRD) and RBS. As a main part of the studies, the atomic intermixing, new compound formation, and phase transitions in the test structure were also studied. For the comparison of IMP and CVD deposited Cu and their effect on the IMP-TaN diffusion barrier, atomic force microscopy (AFM), SIMS, XRD and Rutherford backscattering spectroscopy (RBS) were employed in conjunction with electrical measurements.

Properties of electroplated copper thin film and its interfacial reactions in the EPCu/IMPCu/IMPTaN/SiO2/Si multilayer structure

Abstract The properties of electroplated copper (Cu) film on a thin seed layer of ionized metal plasma deposited Cu have been investigated as a function of annealing temperatures together with the diffusion barrier performance in the EPCu/IMPCu/IMPTaN/SiO 2 /Si multi-layer structure. The growth morphology of electroplated Cu film on ionized metal plasma deposited Cu seed layer was found to be more uniform and gave lower root mean square values (∼13.76 nm), resulting in a lower resistivity (1.72 μΩ cm) of electroplated Cu film. Annealing at temperatures of higher than 750°C resulted in slightly higher sheet resistance, larger grain sizes and rougher surface. Scanning Electron Microscopy images showed that the agglomeration of electroplated Cu film occurred only at annealing temperatures higher than 850°C. During annealing, the electroplated Cu grains grew normally and their sizes increased to about five times larger than the thickness of the electroplated Cu film but the (111) preferred orientation was maintained up to 950°C. Furthermore, the interfacial reactions between Cu film layer and ionized metal plasma deposited Tantalum nitride (TaN) diffusion barrier were also detected at annealing temperatures of higher than 750°C.

Diffusion barrier properties of ionized metal plasma deposited tantalum nitride thin films between copper and silicon dioxide

Tantalum nitride thin films with different thickness are sputtered deposited on silicon dioxide in the Cu/TaN/SiO2/Si multiplayer structure. Using resistivity analyses, X-ray diffraction, scanning electron microscopy and Rutherford backscattering spectroscopy, this work examines the impact of varying layer thickness on the crystal structure, resistivity, intermixing and reactions at the interfaces before and after annealing. The thinner the film thickness of TaN, the severe the reactions at the interface of Cu/TaN and consumed more conductive Cu. All the structures shown similar degradation process, and were found to be stable up to 500°C for 35 min. Accelerated grain growth and agglomeration were also observed after annealing temperature higher than 550°C at all Cu surfaces of the samples.

Study on SiNx passivated Cu/Ta/SiO2/Si multilayer structure

Silicon nitride (SiNx) thin film layers were deposited on Cu/Ta/SiO2/Si multilayer structures by Plasma Enhanced Chemical Vapor Deposition at the temperature 285°C. The influence of post deposition thermal annealing treatments on the micro-structural, compositional and thermal stability study of SiNx/Cu/Ta/SiO2/Si multilayer structure was studied and compared with unpassivated, Cu/Ta/SiO2/Si multilayer structure. It was found that after SiNx passivation, the formation of Cu2O and Ta2O5 was significantly reduced and the structure becomes more stable than unpassivated one. The reaction between Cu, Ta and O was not found in this SiNx/Cu/Ta/SiO2/Si multiplayer structure but the out diffusion of Ta to the Cu surface was unable to be suppressed. The Ta barrier was observed to fail at temperatures above 750°C due to the formation of TaxNy, at the interface of SiNx/Cu.