Orbital polishers

Fig. 19. Scratches on a wafer caused by fall-off of diamond grit from an end effector for (a) a rotating polisher and (b) an orbiting polisher.

A small quantity of molybdenum disulphide powder, preferably between 1 m and 10 particle size, is then placed on the surface and rubbed smoothly into it with a soft cloth, using a firm orbital polishing action. Alternatively the powder can be placed on a cloth or impregnated into a piece of synthetic sponge and applied in... 

Orbital motion offers the capability of achieving high relative velocities without sacrificing tool footprint. This point is especially important as the semiconductor industry prepares to make the transition to 300-mm wafers. Several CMP tool concepts have been developed based on orbital motion. Some orbit the carrier while rotating the platen [13]. Others orbit the polishing pad while rotating the carrier [14]. Another design involves orbital (as well as arbitrary nonrotational) motion on a fixed polish pad [15]. 

Every available inch was filled with instruments a barometer, a globe, an armillary sphere to demonstrate the Copemican system by which the planets revolve round the sun in circles, an air pump, a microscope, and a telescope. On the table in the center was an orrery, a model of the sun and planets supported by wires with a mechanism underneath to turn each in its individual orbit. The machine had been made by a true craftsman, every tiny part polished and balanced to perfection. The beams of light cast by these... 

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. 

Gitis et al. [21] demonstrated the effectiveness of a novel noninvasive instrument called PadProbe , developed by CETR Inc., in monitoring pad surface quality and pad life. PadProbe can be installed on rotational, orbital, and linear type CMP polishers (refer to Fig. 4.10). This sensor can monitor pad surface friction and wear in situ during the conditioning process. The only requirement is that the sensor should be in direct contact with the pad surface. 

The idea of LCAO MO is motivated by the fact that the molecular orbital should consist of spatial sections (atomic orbitals), because in a molecule in the vicinity of a given atom, an electron should be described by an atomic orbital of this atom. The essence of the LCAO approach is Just the connection (unification) of such sections. But only some AOs are important in practice. This means that the main effort of constructing MOs is connected to precise shaping and polishing, by inclusion of more and more of the necessary AOs. ... 

Copernlcan astronomy The system of astronomy that was proposed by the Polish astronomer Nicolaus Copernicus in his book De revolutionibus orbium coelestium, which was published in the month of his death (in 1543) and first seen by him on his deathbed. It used some elements of Ptolemaic astronomy, but rejected the notion, then current, that the earth was a staUonary body at the centre of the universe. Instead, Copernicus proposed the apparently unlikely concept that the sun was at the centre of the universe and that the earth travelled in a circular orbit about it. In addition Copernicus revived the idea that the movement of the sun and the fixed stars was due to the daily axial rotation of the earth. Galileo s attempts, some 70 years later, to convince the Catholic church that in spite of scriptural authority to the contrary, the Copemican system was correct, met with such stem resistance that De revolutionibus was placed on the church s list of forbidden books, where it remained until 1835. 

Coparnlcus, Nicolaus (Mikolaj Kopernik 1473-1543) Polish astronomer, who studied mathematics and optics. By 1514 he had formulated his proposal that the planets, including the earth, orbit the sim in circular paths, although it was not formally published until the year he died. This refutation of an earth-centred universe raised hostile opposition from the church as well as from other astronomers. 

The German X-ray satellite telescope ROSAT was placed in orbit in 1990. It is equipped with a four-mirror system of parabolic and hyperbolic Zerodur cylinders nested into one another (see Fig. 4.66). The inner surfaces of these reflectors were ground and polished by Carl Zeiss, Germany. The residual surface roughness is less than 0.2 nm RMS. An angular resolution of 3.3 arc seconds was achieved for the telescope due to the precise fabrication and mounting of the mirrors. 

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