Interlayer Dielectric CMP

Seike Y, Lee FI, Takaoka M, Miyachi K, Amari M, Doi T, Philipossian A. Development of a pad conditioning process for interlayer dielectric CMP using high-pressure micro jet technology. J Electrochem Soc 2006 153(3) G223-G228. 

I. Ali and S. Roy, Pad conditioning in interlayer dielectric CMP, Solid State Technol, June 1997. 

The most commonly implemented and extensively investigated CMP steps are the preparation of planar premetal dielectrics (PMD) and interlayer dielectrics (ILD) films on wafer. Together they are labeled as oxide CMP, as they both use the same materials that are based on silicon dioxide. Both processes share the integration concerns in deposition, planarity, and defectivity. 

Chemical Mechanical Planarization (CMP) plays an important role in today s microelectronics industry. With its ability to achieve global planarization, its universality (material insensitivity), its applicability to multimaterial surfaces, and its relative cost-effectiveness, CMP is the ideal planarizing medium for the interlayered dielectrics and metal films used in silicon integrated circuit fabrication. But although the past decade has seen unprecedented research and development into CMP, there has been no single-source reference to this rapidly emerging technology - until now. 

Chapters 1 and 2 introduce the CMP process and historical motivations. The present status of CMP is discussed in Chapter 2, which focuses on establishing the need of advanced metallization schemes and planarization. There are a large number of variables that control the process these are discussed in Chapter 3. Chapter 4 presents the science of CMP— mechanical and chemical concepts important in understanding the CMP fundamentals. The CMP of the Si02 films, the most commonly used insulator interlayer dielectric, is discussed in Chapter 5. Chapters 6 and 7 cover the CMP of the two most studied metals, W and Cu, respectively. Chapter 8 examines the applicability of CMP to new materials, e.g., Al, polymers, and Si3N4 photoresists. Finally, Chapter 9 covers post-CMP cleaning science and technology. 

Interlayer dielectric (ILD) CMP typically uses a fumed silica slurry dispersed in an aqueous medium at a pH near 11 Fumed silica is a widely adapted abrasive for ILD CMP because of its inexpensive price, high purity, and colloidal stability. However, fumed silica is difficult to disperse in an aqueous system, and it is difficult to control powder processing because of the large specific surface area of 90 15 mVg, making it very reactive. ILD CMP slurry was prepared at pH 11 to accelerate the chemical attack on the deposited PETEOS film on the wafer surface. But silica particles dispersed in aqueous media are partially dissolved at pH 11. Consequently the removal rate decreased and microscratches were generated on the wafer surface due to agglomeration of silica particles as surface potentials decreased. ... 

CMP remains hampered by systematic and random interlayered dielectric (ILD) thickness variation at the wafer and die level. Pattern dependencies within the die, in particular, have been of concern for both manufacturability and product design. 

FIG. 27 (Top) Schematic representation of chemical-mechanical polishing (CMP) process. (From http //www.el.utwente.nl/tdm/mmd/projects/polish/index.html.) (Bottom) Review of tungsten CMP (a) silica (interlayer dielectric) is etched, (b) tungsten is deposited onto silica ILD, and (c) CMP is applied to remove excessive tungsten layer and other levels are built on this level (multilevel metallization). (From Ref. 90.)... 

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