Effect of Tribological Properties of Undoped and Florine-Doped Silicon Di-Oxide Fims on Chemical Mechanical Planarizatio
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EFFECT OF TRIBOLOGICAL PROPERTIES OF UNDOPED AND FLORINE-DOPED SILICON DI-OXIDE FIMS ON CHEMICAL MECHANICAL PLANARIZATION PROCESS A.K. Sikder, S. Thagella., U.C. Bandugilla and Ashok Kumar1 Center for Microelectronics Research 1 Also with Department of Mechanical Engineering University of South Florida, Tampa, FL 33620 ABSTRACT Chemical mechanical planarization (CMP) occurs at an atomic level at the slurry/wafer interface and hence slurries and the interaction of the films and polishing pads play a critical role in the successful implementation of this process. Understanding the tribological properties of a dielectric layer in the CMP process is critical for successful evaluation and implementation of the materials. In this paper, we present the effect of tribological properties of undoped and florine doped silicon dioxide films on their CMP process. A micro-CMP tester was used to study the fundamental aspects of CMP process. We have studied the CMP process of oxides on polyurethane pads (IC1000-B4/SubaIV) with colloidal silica slurry at different conditions. The coefficient of friction (COF) and acoustic emission signal was monitored during process. The COF was measured during the process and was found to varies differently for different samples and with down force and platen roatation. The effects of machine’s parameters on the polishing performance and correlation of physical phenomena with the process has been discussed. I. INTRODUCTION Continued miniaturization of the device dimensions and the related need to interconnect an increasing number of devices on a chip have led to building multilevel interconnection on planarized levels. In chemical mechanical planarization (CMP) very thin materials (≤5 µm) have to be removed very precisely while maintaining the precise control on the remaining thickness. CMP is a tribochemical process involving few basic components. Mechanical wear was accelerated by a chemical reaction, later induced by friction [1]. Planarization of the wafer results from the synergistic action of the mechanical shear forces and the chemical action of the slurry [2]. Many issues, e.g. polishing conditions, pad properties, slurry chemistry and hydrodynamics, and polishing head design, have been addressed by several researchers [3,4-6]. However, a poor understanding of complicated polishing phenomena makes it difficult to achieve local and global uniformity. Different CMP processes attempt to achieve a balance between removal rate and global/local planarization through a combination of solution chemistry, speed, applied pressure, and pad properties [7,8]. Often a change in slurry or operating conditions lead to conflicting performance. There is a great need for a better understanding of all the complex tribological interactions between slurry, polishing pad, carrier film, wafer, polishing head, pad conditioner, etc. Fundamental tribological studies will allow to optimize the pad design, material selection, process pressure, orbital and linear speed, chemical solution, within wafer uniformity, and lo
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