Highly (111) Oriented Al Thin Films by Ion-Plating Method Using Discharge Plasma
- PDF / 447,008 Bytes
- 6 Pages / 595 x 842 pts (A4) Page_size
- 23 Downloads / 180 Views
Highly (111) Oriented Al Thin Films by Ion-Plating Method Using Discharge Plasma Shin Masui, Kimio Kinoshita, Susumu Sakuragi and Toshio Kudo Sumitomo Heavy Industries, Ltd. 63-30 Yuuhigaoka, Hiratsuka, Kanagawa 254-0806, Japan. Shinji Takayama Dept. of Systems and Control Engineering, Hosei University, 3-7-2 Kajinocho, Koganei, Tokyo 184-8584, Japan. ABSTRACT Application to aluminum deposition using ion-plating method is described. This method has several superior features for generating highly (111) orientation. The origin of this orientation and surface roughness are discussed in connection with a kinetic energy of the ions. The film properties thus made were compared with those of a conventional sputtered film. The higher (111) oriented film showed high resistance against hillock formation even after annealing at high temperatures. An effect of a plasma cleaning of substrate surface was confirmed to be quite helpful for promotion of (111) preferred orientation. INTRODUCTION It is interesting that sputtering (SP) and ion-plating (IP), which are categorized in the same PVD process, produce quite different film properties. SP deposition is the most industrially successful method because of easy-handling and practically high productivity. However, in respect of film properties, the SP film tends to have columnar structure at low substrate temperature [1] and this leads to some undesirable characteristics such as void formation. The effect of texture and grain structure on electromigration was reported [2], where films with a preferred orientation have been shown to have a resistance against not only void but also hillock formation. These preferred orientation are generally pursued with a help of some kind of underlayers for aluminum films [3,4]. To get highly oriented films without underlayers, it is important to activate a surface migration. This is achievable to a large extent by heating a substrate although this process is often unacceptable in production. Instead of heating a substrate, surface migration can be also enhanced by increasing the kinetic energy of evaporated atoms. Based on this concept, IP method is a suitable way to promote surface migration so that evaporated atoms can easily get a sufficient kinetic energy. This report shows a novel IP method using a plasma gun, which creates a high density DC arc plasma, to obtain superior properties of Al thin films. APPARATUS The basic IP system is illustrated in Fig. 1. A high density Ar plasma (electron density 1011-1012 cm-3 at a discharge current of 100A) generated by a plasma gun is extracted into the chamber and flows to the hearths which are the anodes of this system. The plasma gun has two intermediate electrodes which create pressure gradient. This pressure gradient protects a cathode from a damage due to the energetic ion bombardment [5]. The hearths consist of two parts. One is the main hearth and another is a ring-shaped supplemental hearth located around the main hearth. In order to guide the plasma beam to both hearths as less losses as possible
Data Loading...
