Global planarization

Electric chemical polish (ECP) and electric chemical mechanical polish (ECMP) [53] have been developed as promising methods for global planarization of LSI fabrication and abrasive-free polish. 

To meet these requirements, a local and global planarization technique for the disk substrates becomes neces-... 

Among numerous planarization technologies, CMP provides a global planarization of topography with a low post-planarization slope [97,98]. It can also dramatically reduce topographical variations to a degree not possible with any other planarizing process [97,99,100]. 

At first, the plated NiP layer of aluminum alloy substrate is oxidized to form an oxide film on the surface, which may be softer [ 122,123] or more friable, and hence is easier to be removed than the NiP layer. Then the oxide Him is worn away by Si02 abrasive particles and is dissolved in the acidic slurry, or both. The protruding region is removed faster than the recessed region [ 124], resulting in global planarization of the substrate surface. The role of the lubricant is to improve the mobility of the slurry and reduce the excessive friction... 

All of these approaches are intended to address global planarization issues. We close this section with a brief note about an alternative approach that focuses on achieving planarization at the die level. The distributed polish head [37], extends the concept of hydrostatic pressure by integrating polish blocks in the carrier design to minimize the locally the spatial variation in the polish. As shown in Fig. 9, each polish block makes contact with several die, each of which may contain regions of high and low pattern density. 

Several contending technologies are presently being used to achieve local and global planarizations that include spin on deposition (SOD), reflow of boron phosphorous silicate glass (BPSG), spin etch planarization (SEP), reactive ion etching and etch back (RIE EB), spin on deposition and etch back... 

SOD + EB), and CMP. Among all these techniques, CMP is the only one that can offer excellent local and global planarities at the same time. More specifically, CMP can yield local planarization of features in the order of tens of microns and near-global planarization as far as tens of millimeters [5,20]. 

Ganguly U, Krusius IP. Novel compensation chemical metal polishing for low dishing and high global planarity for ultra-planar die applications in micro-optics and micro-electro-mechanical systems. Thin Solid Films 2004 460 306-314. 

CMP comes next. Its goal is to planarize and pattern the oxide [14]. The CMP step is discussed in more detail in the following two chapters. It should be mentioned here that CMP is not the only option for planarization. More cost-effective solutions have been studied and used, such as multilayer resist processes and spin-on glass in combination with RIE (Fig. 12.4). However, the obtained global planarity for such non-CMP processes is inferior to CMP planarity. They are therefore more suitable for ILD planarization than for STI... 

Boyd JM, Ellul JP. A one-step shallow trench global planarization process using chemical mechanical polishing. ECS Proc 1996 95-5 290. 

Fischer E, Gabric Z, Neureither B, Spindler O, GraBl T. Global planarization by selective deposition of ozone/TEOS. VMIC Conference Proceedings 1995. p 247-253. 

Table 1.2 lists several advantages of CMP. These are discussed again in Chapter 2. The most important advantage is that CMP achieves global planarization which is essential in building... 

Figure 2.2 Degrees of surface planarity (a) unplanarized, fl)) surface smoothing, (c) local planarization, and (d) global planarization.

The requirement for global planarity results as circuit dimensions are extended into the sub-0.5 pm regime. Lithography tools require high numerical aperture lenses to print the sub-0.5 pm... 

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