Mathematical modeling of CMP conditioning process Onemoon Chang a , Hyoungjae Kim b , Kihyun Park a , Boumyoung Park a , Heondeok Seo a , Haedo Jeong c, * a Department of Precision and Mechanical Engineering, Pusan National University, San30 Changjeon-dong, Keumjeong-ku, Pusan 609-735, Republic of Korea b KITECH, Pusan National University, San30 Changjeon-dong, Keumjeong-ku, Pusan 609-735, Republic of Korea c School of Mechanical Engineering, Pusan National University, San30 Changjeon-dong, Keumjeong-ku, Pusan 609-735, Republic of Korea Received 15 July 2006; accepted 27 November 2006 Available online 25 January 2007 Abstract Up to now, the conditioning model with an oscillating conditioner wheel has not been studied. In this paper, kinematic analysis of the conditioning process and mathematical modeling of pad wear while the conditioner wheel oscillates is studied and the results show how the various parameters of the conditioning process influence the pad shape. The conditioning of the polishing pad is one of the most important processes associated with the CMP (Chemical Mechanical Polishing). As the wafer is polished, the surface of the pad can be deteriorated with a reduced polishing rate and reduced planarity due to wear and glazing of the pad. Thus, the polishing pad needs to be conditioned to maintain its effectiveness. In general, the conditioning process is used to regenerate the pad surface by breaking the glazed area of the pad and increase the MRR (Material Removal Rate) and give us longer pad life. However, as the conditioning process continues, the pad shape becomes more and more concave over the whole pad while the conditioner wheel oscillates (Y.Y. Zhou, E.C. Davis, Mat. Sci. Eng. B. 68 (1999), 91–98). It has been shown that the concavity of the polishing pad increases with conditioning time – longer conditioning induces a higher incidence of concavity of the polishing pad. Therefore, the conditioning process is related to the WIWNU (Within Wafer Non-Uniformity). Through this conditioning model, thickness variation of the polishing pad can be predicted. Ó 2006 Elsevier B.V. All rights reserved. Keywords: CMP; Kinematic analysis; Velocity profile; Sliding distance; MRR; Conditioning process 1. Introduction The polishing pad plays a key role in the mechanical aspects of polishing. The abrasive particles have been incorporated into the polishing pad. The surface of the material is polished when the abrasive particle is forced against the surface by the asperity of the pad. The particle is under the force of the asperity, pushing against the sur- face, dragged along by the asperity at the relative velocity of the pad with respect to the wafer [2]. A significant fea- ture of the pad is its asperities on the top of the pad. How- ever, the asperities of the pad will deteriorate during polishing. Gradually, this results in a reduced material removal rate and an increase of the glazed area of the pad. Thus, conditioning process is necessary to regenerate the pad surface by breaking the glazing area of the pad. A variety of pad conditioning methods were developed to stabilize the material removal rate. Abrasive pad condi- tioning using a diamond-impregnated disk wheel is used to be the most effective method [3]. The conditioner consists of diamond grits in a disk wheel which protrude by a given amount. During the polishing, the conditioner wheel oscil- lates on the pad at a high relative velocity and presses into the pad surface under the controlled weight. Similarly, the arm with the conditioner on the end sweeps across the pad surface by means of a stepper motor. If the pad condition- ing was repeated after each wafer was polished, the mate- rial removal rate remained stable for many steps of the CMP process. Therefore, as long as the asperities are con- 0167-9317/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.mee.2006.11.011 * Corresponding author. E-mail address: hdjeong@pusan.ac.kr (H. Jeong). www.elsevier.com/locate/mee Microelectronic Engineering 84 (2007) 577–583