Specific CMP consumables requirements

Removal rate selectivity, that is, the ratio between the rate of the main material and that of underlying, exposed layers, plays an increasingly important role. Especially when thick layers on top of thin layers have to be planarized with low erosion, as in the case of poly-Si on gate oxide for power MOS or metal on barrier films for, e.g., MEMS, highly selective slurries are required. Comparable to recent developments for More Moore devices, ceria-based slurries or slurries with tailored additives have to be employed. 

As a result of the strongly varying selectivity requirements, the consumables manufacturers have developed sets of proprietary additives, which allow the designing of slurries for very specihc applications. Slurries for poly-Si CMP with a high selectivity of 100 1 to Si02 or SiN are likewise available hke slurries for Si02 CMP with a high selectivity to Si or poly-Si. These tunable slurries are available with silica or with cetia abrasive particles. 

Cu CMP slurries for through sihcon vias (TSVs) with very high removal rates and high selectivity to oxides like TEOS have been developed with silica abrasive particles as well as so-called particle-free slurries (e.g. Reactive Liquid from Dow Chemicals). Cu barrier slurries with tunable selectivity to TaN and tetraethylorthosilicate (TEOS) 

As indicated in the previous sections, CMP has found many applications in the manufacturing of More than Moore devices. In this chapter, examples will be discussed where polishing processes have to be employed for the manufacturing of power devices, MEMS and MOEMS chips, and micro-displays. The described applications are exemplary and do not claim completeness. Wafer bonding will be covered with examples from the fields of stacked devices and wafer-level packaging (WLP), while TSVs will be treated in more depth in a separate chapter in this book. 

In this chapter, two types of power devices will be discussed, which use CMP in their manufacturing flow, the power MOSFET and IGBT. They are designed to handle voltages up to 1000 V or even larger and can control currents up to several hundred amperes. Both types of devices are fabricated in large scale and can be found in 

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