Effect of Molecular Structure of Scavengers on Copper Diffusion Deterrence in Low k Film
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0949-C03-09
Effect of Molecular Structure of Scavengers on Copper Diffusion Deterrence in Low k Film Yutaka Nomura1, Daisuke Ryuzaki2, and Mitsumasa Koyanagi3 1 Research & Development Center, Hitachi Chemical Co., Ltd., Hitachi-shi, 317-8555, Japan 2 Central Research Laboratory, Hitachi, Ltd., kokubunji-shi, 185-8601, Japan 3 Department of Bioengeering and Robotics, Tohoku University, Sendai-shi, 980-8579, Japan
ABSTRACT Low k material with high deterrence ability of copper diffusion has been proposed to reduce the effective electrical resistance of copper wirings. Providing organic low k material with deterrence ability was attempted by adding a chemical agent that chemically combines with copper. The insulation lifetime of the low k film with benzotriazole (BTA) as the copper scavenger was about two orders of magnitude higher than that of BTA-free low k film, at the practical electric field strength of 0.1 MV/cm. The copper diffusion deterrence ability was clearly dependent on the ability of the copper scavenger. INTRODUCTION The signal delay at multilevel interconnections is dependent on the product (RC time constant) of the wiring resistance (R) and the capacitance (C) between wirings [1]. In order to reduce R and C between wirings, the application of new materials to the multilevel interlayer is considered to be positive. The wiring metal has been changed from aluminum to copper due to its lower resistance [2]. The interlayer dielectric is going to adopt new organic dielectric materials having lower dielectric constant than SiO2. However, further miniaturization of the design rule will make the wiring trench occupied by the barrier metal having higher resistance than copper [3]. As a result, the effective resistance of the wiring will rise and the advantage of copper wiring will be diminished. This study aims at establishing a new technology that enables the reduction of signal delay depending on interlayer, in order to realize higher operation speed and higher integration of ULSIs. The technology will reduce the effective wiring resistance by using low k material with high deterrence ability of copper diffusion. The barrier metal with high resistance in not necessary, if the low k material shows high deterrence ability of copper diffusion. Providing high copper diffusion deterrence ability with low k material was developed by the addition of a copper scavenger. Copper scavengers (the agents chemically combining with copper) chemical combine with copper) were screened from the non-ionic compounds that did not raise the dielectric constant of the low k film by their addition. Specifically, triazole derivatives were selected since they are known as copper anticorrosive. First, we investigated the validity of this concept by using BTA as the copper scavenger. Copper diffusion deterrence ability of the materials was mainly evaluated from time dependent dielectric breakdown (TDDB) [4]. Next, the dominant factor influencing the ability was investigated by comparing copper scavengers with different scavenging abilit
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