CMP Requirements in Comparison with IC Fabrication

The advancements of microelectronics with its increasing device performance and decreasing structure dimensions, which recently fell below the 100-nm mark, follow the path given by Moore s law. In contrast, microfabrication deals with a broad range of structure dimensions between submicrometers and millimeters [7]. The main developments in CMP are traditionally connected to those in advanced IC manufacturing. In recent years, however, the CMP equipment and consumable communities have also paid close attention to microfabrication. It is recognized that MEMS-specific CMP processes require dedicated consumables [8] and optimized tool sets [9] due to their diversity in structure dimension and materials to be processed. 

The differences and similarities in the requirements of CMP for microelectronics manufacturing and microfabrication are summarized in Table 14.1. This comparison gives an overview of the parameters relevant to CMP and is intended to serve as a guideline for CMP practitioners, consumable suppliers, equipment manufacturers, and others. Polishing tools and consumable sets capable of handling MEMS-specific tasks will be discussed at the end of this section. The following is a list of these terms for comparison. 

Layers Typical materials for which CMP processes originally have been developed for microelectronic applications include various types of silicon dioxide such as thermal oxide, TEOS, HDP, BPSG, and other B- or P-doped oxide films. These films are used for various isolation purposes including interlevel dielectric (ILD), intermetal dielectric (IMD), or shallow trench isolation (STI). In addition, n- or p-doped poly-Si, which is a semiconducting material used as capacitor electrode material for DRAMS or gate electrode for MOS applications (CMOS as well as power MOS devices), also has to be polished. Metals for which CMP processes have emerged over the last 10-15 years are W for vertical interconnects (vias) and most importantly Cu as a low-resistivity replacement for aluminum interconnects, employed in the damascene or dual-damascene processing scheme. Other metals that are required for future nonvolatile memories are noble metals like Pt or Ir for which CMP processes have been explored. 

Microfabrication to a large extent relies on microelectronic processing technologies. Therefore, all aforementioned materials have found their way into various microsystem applications. Beyond that, other metals to be planarized like Ni or alloys like NiFe are regularly used for applications such as hard-disk drives. In microfabrication, the spectrum of materials is extended by including 

Layers Various Si02, poly-Si, W, Cu, noble metals Various Si02, poly-Si, Si, various metals, ceramics, polymers Great variety Upcoming materials PZT, magnetic alloys 

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