• PDF / 524,155 Bytes
• 8 Pages / 420.48 x 639 pts Page_size
• 56 Downloads / 207 Views

DOWNLOAD

REPORT

---

INFLUENCE OF ENERGY DEPOSITED BY ENERGETIC PARTICLE BOMBARDMENT ON THIN FILM CHARACTERISTICS

Harold F. Winters, W. Eckstein,* and H.J. Coufal IBM Research Division, Almaden Research Center, 650 Harry Road, San Jose, California 95120-6099 *Max-.Planck-.Institut fur Plasmaphysik, D-8046 Garching, Munich, Germany

ABSTRACT:

It has been recognized since the 1960's that bombardment of a growing thin film by energetic particles strongly influences film properties. Particle bombardment has generally been accomplished by accelerating ions into the growing film. However, it has also been recognized since the 1960's that energetic particles reflected from the target influence the characteristics of films grown by physical sputtering and many experiments have been interpreted on this basis. A systematic study of the energy reflected from the surface by normally incident, singly charged noble-gas ions on five substrates of different masses has recently been published. This data along with sputter yields from the literature allow estimates to be made which were previously unavailable. The energy reflected from the target is carried away by electrons, sputtered particles and reflected ions (neutrals). The purpose of this paper is to provide basic information which will allow thin film scientists to estimate the influence of various experimental parameters on the amount of energy arriving at the growing film. The energy reflected from the target per sputtered atom will be given as a function of ion mass, target mass, and ion energy. TRIM.SP Monte Carlo calculations will be used to estimate the ratio of the energy carried away by sputtered atoms to that carried away by reflected ions. Calculations will also be used to estimate the average energy of the sputtered atoms as a function of ion mass, substrate mass and ion energy. It will be shown how this information can be used to guide the adjustment of experimental parameters in sputtering environments so as to control film characteristics.

INTRODUCTION

Research accomplished in the 1960's showed that energetic particle bombardment influenced the properties of sputtered films. Frerich [1] showed that sputtered films of niobium were superconducting when exposed to ion bombardment during growth whereas they were not superconducting when grown under similar conditions without ion bombardment. He suggested that ion bombardment lowered the concentration of chemically active gas in the film material. Maissel and Schaible [2] applied a negative bias to films which were grown in a dc, diode sputtering system. This caused the growing films to be bombarded with positive ions. They coined the term "bias sputtering" to describe this procedure and showed that ion bombardment tended to cause the resistivity to decrease toward bulk values. They also suggested that these results indicated that ion bombardment minimized the

Mat. Res. Soc. Symp. Proc. Vol. 236. @1992 Materials Research Society

274

concentration of chemically active gas (oxygen) in the film. Winters and Kay [3] verified this as