Adam Proszynski

Stress development during evaporation of Cu and Ag on Silicon

This work presents results of stress measurements during deposition of thin silver and copper films on 100 µm Si substrate. The stress in thin films has been determined by means of an optical system for the measurement of samples curvature. This system was applied in situ in a high vacuum deposition system. For Ag films the stress occurring during deposition goes from a low compressive value to tensile for thickness less than 30 nm and to compressive above this. For Cu films we observe tensile stress for thickness less 20 nm and above 50 nm. The same general trend of stress evolution with thickness is present in all cases at initial stage. There is the same growth mode for Cu and Ag because of the similar shapes of stress curves for thickness lower than 30 nm The behavior of stress evolution was explained by island nucleation and growth, island coalescence and continuous film growth. The difference in the stress evolution above 30 nm is caused by the fact that silver may be less sensitive than copper to adsorption of impurities. Adsorbed contamination inhibits compressive stress increase generated by grain boundary and defects remaining in the film.

Stress development during thin film growth and its modification under ion irradiation

The paper presents the results of average stress measurements during deposition of thin copper and silver films and during ion irradiation of molybdenum thin films. Deposition chamber and ion implanter were equipped with the same optical systems for radius of curvature measurement (scanning technique). The average stress in the 92 nm total thick Cu/Ag/Cu/Ag system on 100 μm Si substrate during deposition at room temperature is reported. Deposition process was intermitted after each material. The non-continuous changes of the stress are interpreted as differences in temperature of the sample in different deposition stages. High residual stresses up to 3 GPa were evidenced in the Mo thin films deposited on Si substrate with RF sputtering. During ion implantation with Kr and Ar ions stress relaxation effect of Mo thin films was observed. Kr ion irradiation of the silicon substrate without a film was additionally performed. After the irradiation (total dose 1.4 x 10 15 ions/cm 2 ), the implanted region of the silicon wafer was under compressive stress. A stress maximum was evidenced for a dose of 1 x 10 14 ions/cm 2 .

The Characteristic of the Multilayer Thin Films by X-Ray Reflectometry Method

The X-ray reflectometry (XR), as a non-destructive method, is a powerful tool in obtaining information about parameters of thin films such as thickness, average density and interface roughness. In this paper Cu/Au, Au/Cu and Cu/Ag multilayer thin films (where the total thickness is less then 1000Å) are presented. The multilayer films are obtained by thermal evaporation in a UHV system, on the silicon substrate. The experimental XR curves contained critical angle and classical Kiessig’s fringes. For these materials the density (), the thickness () and interface roughness () information for every layer separately were calculated. The experimental reflectometry curves were analyzed using the WinGixa programme X’Pert software. The values of layer density show that they are reached in neighbor density and it is connected with the creation of the Cu-Au or Ag-Cu interlayer reached into Cu, Au or Ag, respectively. The analysis of roughness show that there are comparable to roughness of substrate only for 2-3 first layers. Further the roughness of Cu, Au, Ag layers are increasing. The comparison of results show that increasing of Ag an Au roughness is bigger than Cu.

Stresses in Multilayer Systems: Test of the sin2Ψ Method

The sin 2 Ψ method based on the asymmetric X-ray diffraction is widely used to determine stresses in thin films. However, application of this method to multilayered thin films is not straightforward. In this work the authors present experimental asymmetric X-ray diffraction maps obtained for Cu/Ni and Au/Ni multilayered systems. They also describe the model based on a Monte Carlo simulation for calculating the X-ray diffraction profiles from multilayers.