Development of intelligent pad and application to analysis of pressure distribution on polishing pad in CMP process
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Development of intelligent pad and application to analysis of pressure distribution on polishing pad in CMP process Masaharu Kinoshita1, Jaehong Park1 and Haedo Jeong 2 1
Nitta Haas Incorporated, 3-17-1, Kannabidai, Kyotanabe-shi, Kyoto 610-0333, Japan.
2
Pusan National University, San30, Jangjeon-dong, Gumgjung-gu, Busan 609-735, Korea
ABSTRACT Most of polishing conditions are not consistent during the polishing process such as pressure, velocity, temperature, pad surface asperity and slurry flow which determine the CMP performance. Traditionally, these parameters are detected by various monitoring methods on CMP polisher. This study introduces a new concept of intelligent pad system with multiple sensors and peripheral devices such as memory, CPU, battery, transmitter and so on. The main functions of the intelligent pad are sensing the change of major parameters and data processing in real-time during the polishing process. The developed intelligent pad has nine points of embedded pressure sensor and makes data processing, saving, and transmitting in real-time. Experimentally, the intelligent pad system was evaluated to understand carrier behavior and pressure distribution. Finally, the analysis of pressure distribution using the intelligent pad turned out a useful method to understand the polishing head behavior and the polishing profile. INTRODUCTION Polishing pad is one of the important consumables of chemical mechanical polishing (CMP) system which plays roles of adding pressure to wafer, transferring slurry to wafer and removing materials away. This study has been started to create value to conventional pad by developing an intelligent pad with new functions. These new functions will help to understand many phenomena during CMP process and to give lots of process information (Fig. 1). One of the CMP phenomena, pressure distribution under the wafer has been reported. Fig.2 shows research examples on pressure distribution in terms of flow dynamics and kinematics. Runnels introduced a tribological model to figure out the pressure distribution under different contact modes[1]. Tharkurta suggested the slurry film model which included slurry seeps down and pad surface bends due to pressure[2]. Kim suggested the uneven pressure distribution resulting from polishing kinematics[3]. When considering based on the previous models, the pressure distribution is generated from slurry flow, pad property, and polisher kinematics which affect the polishing performance, especially removal profile. In order to verify the pressure distribution scientifically, authors developed a pressure sensor embedded pad as a prototype to find the usefulness and possibility of the intelligent pad. Conventional CMP carrier has membrane and retainer ring, and its motion can be changed by the process condition. Ideal carrier motion and pressure should not be changed during the process, however real ones are changed and make the polishing quality deteriorated because of unstable
wafer contact condition. Therefore, it is required to demonstra
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