Polishing of optoelectronic components made of monocrystalline silicon carbide

Material removal rate in polishing anisotropic monocrystalline materials for optoelectronics

“…It is based on a cluster model of frictional wear of solids and a physical statistical model of formation of debris particles and their removal from the workpiece surface [16][17][18][19][20]. The calculation of workpiece material removal rate Q in polishing involves the use of machining process parameters (the workpiece to pad contact pressure, the velocities of the workpiece and pad relative motions, the contact area between the workpiece and the polishing pad, the contact temperatures) and characteristics of the workpiece material and polishing pow der (the thermal conductivity coefficient of the workpiece material, the debris particle surface area, the mean size of polishing powder grains) and is carried out by the formula [1,3] …”

“…is the dimen sionless parameter; λ is the thermal conductivity coefficient of the workpiece material; T is the contact tem perature; p is the nominal workpiece to pad contact pressure; u is the velocity of the workpiece and pad rela tive motions [1,3,16,17,20]. The number of the ith debris particles on the surface area S i during the contact between the polishing grain and the workpiece surface t c = d/u was determined, in view of their distribution over the surface areas, by the formula ,…”

“…Considering that the unit event of surface wear is represented as a transition of the cluster from the bound state to the free one, the outcome of transitions between equidistantly located energy levels is the formation of debris particles whose surface areas can take on some discrete values and the surface area of the ith debris par ticle is given by S i = S 0 (i + 1) [1,3] ( ; N is the number of samples; S 0 is the minimum cluster surface area that depends on the workpiece material structure and the number of molecular fragments ξ). The most probable value of the debris particle surface area is determined, in view of the Poisson distribution, by the for mula .…”

“…Natural frequencies of sapphire molecular fragments, which were found by Raman spectra and IR absorption spectra, have the following values: ω 01 = 10.8 × 10 13 s -1 (573 cm -1 ), 12.1 × 10 13 s -1 (642 cm -1 ), and 14.1 × 10 13 s -1 (748 cm -1 ) [22,25]. Natural frequencies of molecular frag ments of the cBN polishing powder: ω 02 = 19.9 × 10 13 s -1 (1056 cm -1 ), 20.7 × 10 13 s -1 (1100 cm -1 ), and 24.6 × 10 13 s -1 (1304 cm -1 ) [3,26].…”

“…Polishing is also carried out through several operations-coarse polishing, prepolishing, polishing, and nanopolishing-using suspen sions of diamond powders and polishing powders [2][3]. In diamond-abrasive finishing of precision surfaces of components and substrates of monocrystalline sapphire, silicon carbide, semiconductor nitrides, optical ceramics, and other crystalline materials the high form accuracy and very low surface roughness should be achieved in a time stable manner and with a high removal rate [4][5][6].…”