Rotary polisher

FIGURE 3.10 Schematic illustration of key working components in a rotary polisher. 

Show that for a rotary polisher, if the pad rotation rate is Qp, the wafer rotation rate is Qw, and the separation between the pad center and wafer center is c, then the relative sliding velocity between the wafer and the pad is... 

Polishing the mounted clinkers can be accomplished in as short a time as three minutes on the rotary polisher or four to eight minutes with the Minimet , using 0.3 pm alumina on Texmet and isopropyl alcohol or propylene glycol. The writer prefers to... 

Many CMP processes are performed on single wafer rotary polishers. The wafer is held top surface down in a rotating wafer carrier and is pressed against a rotating polymer pad on which a chemically active slurry is dispensed. The removal rates of various materials depend on the applied pressure, the kinematics, and on the chemistry and particle content of the slurry. Different materials and combinations of materials on the wafer surface require different slurries in order to achieve the desired removal rate, rate selectivity between exposed materials, and the desired uniformity, surface quality, and defect count. The material properties and surface stmcture of the pad also affect the latter three measures. Pads and slurries are therefore critical elements of the process and together constitute a large fraction of the cost of IC manufacturing (Moinpour, 2007, p. 27). 

Filters are used only at specific places in the purification of water. Sand filters are used as a final polishing step or prior to a membrane or ion-exchange process, and vacuum rotary-drum filters are used for dewatering sludges. 

A sample of monomer ( 50 g) was placed in a 100-ml round bottomed flask, which was attached to a rotary evaporator. The flask was heated to 150°C with the aid of an oil bath while stirring under vacuum (0.20 mmHg). The monomer was stirred and heated under vacuum for a period of 45 min to 1 h in order to simultaneously degas and B-stage the monomer. The B-staged monomer was then held under nitrogen and poured into a preheated mold, which consisted of two polished aluminum plates (6 x 6 x 1/2 in.) with a three-sided 1/8-in. thick Teflon spacer between the two plates. The spacer was cut from a 6 x 6 x 1/8 in. 

Kiil, S., Weinell, C.E., Pedersen, M.S., Dam-Johansen, K. Analysis of elf-Polishing Antifouling Paints Using Rotary Experiments and Mathematical Modelling. Ind. Eng. Chem. Res. 40(2001), 3906-3920. 

Production loading tools should be hardened (60 Rockwell C is common). The die should be ground, honed, and lapped or polished to an 8 or 16 rms micro-inch finish. Some claim better results if the final operation involves longitudinal rather than rotary motion... 

Typically, both the wafer carrier and platen are rotated in the same direction. A downforce is applied while the wafer carrier and platen are rotated on their own axes coc and co, respectively. The polishing slurry is dispensed from a tube located at the center of the pad, and as the platen rotates the slurry is transported between the wafer and the pad [3-6]. In addition to the rotary platform, an orbital design has also been implemented (Fig. 3.3) [2]. The operating principle for the orbital design is similar to the rotary platform, except that the polishing head and table are in orbital motion to each other. In addition, the slurry is usually delivered through the pad. 

Figure 3.7 shows a brief history of polishing practice. Although the rotary table type is one of the most popular polishers, many other types of polishers have been introduced by several manufactures over the years. Each type has its own characteristic features [22]. 

FIGURE 3.7 Schematic illustration of different types of polishers rotary with multitable and multihead (1), small head (2), small table (3), linear motion type (4), fixed abrasive type (5), and grinding t5 pe (6). 

When chemical reactions are involved in a process, it is important to know the reaction temperature. In the model described here, reactions at a point on the wafer surface are assumed to be driven by temperature excursions due to contact by passing pad asperities. This is known as flash heating. In systems in which there is dry sliding contact between two rough surfaces, it is known that flash temperatures at asperity contacts can be much higher than the average temperatures of the workpieces involved. In CMP, however, the contact is lubricated and cooled by the slurry, and this needs to be taken into account. In the case of polishing on a rotary tool, it is possible to derive a simple estimate of the mean reaction temperature, and it is this that we use in the chemical part of the two-step model. 

FIGURE 13.7 Removal rate and HDP-CVD oxide/Sl3N4 selectivity versus (down-force) X (table rpm) obtained on a rotary-type polisher using high-selectivity slurry. 

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