ELastic Properties of Sputtered Thin Films: Influence of Different Preparation Conditions
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ELASTIC PROPERTIES OF SPUTTERED THIN FILMS: INFLUENCE OF DIFFERENT PREPARATION CONDITIONS
C.E. BOTTANI°, M. ELENA *, M. BEGHI°, G. GHISLOTT'I °, L. GUZMAN MIOTELLO 00, AND P.M. OSSI 0° ** * 00
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° Dip. Ingegneria Nucleare, Politecnico, via Ponzio 34/3, 20133 Milano, Italy Istituto per la Ricerca Scientifica e Tecnologica, 38050 Povo, Italy
Dipartimento di Fisica dell'UniversitY, 38050 Povo (TN), Italy Unit• clNFM, 38050 Povo (TN), Italy.
ABSTRACT This work presents the first results of a study aimed at better understanding the elastic behaviour of hard coatings produced by various techniques. This is important also in view of the need to be able to control the level of internal stresses, particularly in PVD coatings. It is well known that in extreme cases excessive internal stress can lead to complete film destruction. We devote this paper to reactively magnetron sputtered TiN, one of the most widely used compounds. Thin TiN films of different compositions were deposited on Si substrates and characterized by SEM, AES, XRD and Brillouin light scattering.
INTRODUCTION Transition metal nitrides play today an important role in several fields, from barrier layers to wear resistent coatings, from the biomedical sector to optical and decorative applications. In this paper we examine the structural and elastic properties of thin TiN films deposited by reactive DC magnetron sputtering. By varying the nitrogen flow during coating preparation we have been able to obtain different film compositions. Sample characterization has been carried out by scanning electron microscopy, Auger electron spectroscopy, X-ray diffraction. The elastic response of the films has been studied by surface Brillouin light scattering.
EXPERIMENTAL Titanium nitride coatings have been produced in a Leybold-Heraeus Z 700 machine capable of reaching a base pressure of approximately 2x10-5 Pa by using turbomolecular and rotary pumps, in addition to a liquid nitrogen cold trap. Ar flow was kept constant in all experiments, at a value of 125 sccm. Nitrogen flow was varied between 18 and 38 sccm. Total pressure in the vacuum chamber was around 0.9 Pa. All depositions were carried out at room temperature on oriented silicon wafers with typical dimensions of 2x2 cm2 . Film thickness ranged from 120 nim to 1000 rim. SEM examination of the samples was carried out by using a JEOL JSM 6300 apparatus. AES was performed with a PHI model 4200 machine, equipped with a Cylindrical Mirror Analyser; the base pressure was in the 10-8 Pa range; primary electron beam energy and current were 3 keV and 0.6 ltA, respectively. Attention was paid to the overlapping betweea the titanium L3232 and the nitrogen KL23~Auger lines [1, 2, 3, 4]. Structural analysis was performed mainly by a Philips Diffractometer System MPD 1880. CuKa radiation was used, withthe X-ray source operating at 40 keV and 20 mA. In order to have direct information on the elastic properties of our samples down to tenths of a micron scale, we used Brillouin spectroscopy, which is a well establi
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