Advanced Plating Technology for Electronic Devices

However, the use of aluminum alloy as a wiring material has confronted application limitations vis-a-vis the highspeed propagation and the high density integration of the ULSI devices. Recently, there has been much interest in the use of copper wiring in the manufacture of semiconductor devices, since copper has much lower electric resistivity compared with aluminum. The Damascene Process, combining copper electroplating and chemical mechanical polishing (CMP), was announced by IBM in September 1997.1)Since then, copper filling by electroplating has been actively studied.2-6)Features, on the order of submicrons, are now the rule in the semiconductor devices designs. In our previous study, ULSI wiring formation without void and overplate was achieved by controlling the additives in the copper plating bath.7) 2. 1. 2 Influence of additives on filling The compositions and operating conditions of copper electroplating baths are shown in Table 1. A high throwing bath (low copper concentration bath) and a conventional decorative bath (high copper concentration bath) were used as plating solutions. Polyethylene glycol (PEG), bis (3-sulfopropyl) disulfidedisodium (SPS), Janus Green B (JGB) and thiourea (TU) were used as additives. Voids formed in the trenches of additive-free bath since the electric current lines are concentrated on the surface and in the corner of the wafer patterns as shown in Fig. 1. Complete void-free features on the trenches 1 General Introduction Recently, many electronic devices, such as cellular phone, have been required to carry with improving their ability. To miniaturize electronic devices, the connection reliability between ICs and external circuits has become increasingly important. Both electroplating and electroless plating have been applied for the metallization and connection of electronic devices. Recently, the manufacture of electronic components has demanded advanced plating technology, because many devices are becoming smaller and more complicated. In this paper, we will focus mainly on the plating technologies used for the metallization and connection of electronic devices. In metallization, we will discuss: wiring formation by copper plating for semiconductors and PCBs, focusing especially on additives, via-filling by copper electroplating as well as the improvement of adhesion strength between the insulation layer and the deposited metal. In the connection of electronic devices, we will discuss bump formation by electroplating and electroless plating as well as the preparation of anisotropic conductive particles.