Stress, Mechanical Properties and Composition Measurements in Sputtered Thick Alumina Films
- PDF / 977,495 Bytes
- 6 Pages / 414.72 x 648 pts Page_size
- 82 Downloads / 184 Views
STRESS, MECHANICAL PROPERTIES AND COMPOSITION MEASUREMENTS IN SPUTTERED THICK ALUMINA FILMS C. A. Ross' and J. J.Barrese2 2'Komag Inc., 275 S. Hillview Drive, Milpitas, CA 95035 Department of Materials Science and Engineering, Stanford University, Stanford CA 94305 ABSTRACT
Thick r.f.-sputtered alumina is used as an overcoat material in microelectronic applications. The stress in the material is compressive and its magnitude is influenced by the sputtering conditions including the power, gas pressure and r.f. substrate bias. These parameters also affect the deposition rate, stoichiometry and sputter gas (argon) content of the material and its etch rate in hydroxide solutions. Nanoindentation measurements of the elastic modulus and hardness are presented for alumina sputtered under different bias conditions and show that the zero bias material appears to be harder and stiffer than material deposited at -100V bias.
INTRODUCTION Sputtered alumina, of composition approximately A120 3, is used extensively in microelectronic applications, for instance as a dielectric in semiconductor devices or as a thick overcoat on thin film magnetic recording heads. The mechanical properties of the alumina are of particular interest in the latter application because of their possible effect on the behaviour of the permalloy pole pieces of the thin film head. For example, the overcoat may alter the stress state in the pole pieces which affects their magnetic behaviour if the permalloy has a non-zero magnetostriction. The physical properties of the alumina are greatly affected by the sputtering conditions under which the film was deposited. The most commonly varied sputter conditions are the gas pressure, target power, substrate bias and the substrate temperature, as well as the geometry of the sputtering machine and its configuration (r.f. or r.f. magnetron). Several studies have previously been presented which relate certain properties of the films to the sputter conditions. Kennedy (1) described the variation of etch rate, refractive index and argon content of r.f. sputtered alumina and Gardner et al. (2) studied the thermal and mechanical stability on heating and the internal stress and thermal expansion of sputtered alumina. Nowicki (3) measured internal stress, hardness, etch rate and other properties of r.f. magnetron sputtered alumina. Kennedy (4) investigated step coverage of alumina sputtered with different substrate bias over a contoured substrate. In this study we examine r.f sputtered alumina made under a range of substrate bias, target power and gas pressures. We present data for internal stress, etch rate in hydroxide solution, stoichiometry and argon content and compare the results to earlier studies. We describe measurements of elastic modulus and hardness in the films using a Nanoindenter.
EXPERIMENTAL METHODS
Alumina films were sputtered from a 38 cm diameter circular target of sintered alumina of 99.5% typical purity in a planar r.f. sputtering system. The substrates used were 51mm square alumina-titanium carbide
Data Loading...
