Abstract
To realize the processing demands of the sapphire wafer surface with scratch-free and nano-scale roughness by mechanical polishing, a novel flexible polishing plate was developed by using soft unsaturated resin. The surface characteristics, material removal rate, and residual stress of the sapphire wafer after the flexible polishing process have been compared with those of the sapphire wafer after the rigid polishing process. Both theoretical and simulation analysis results show that the abrasive particles in the flexible polishing exhibit an apparent yielding effect during the polishing course, which contributes to the achievement of plastic flow removal for the wafer surface. The experimental results show that the surface roughness and subsurface damage of the sapphire wafer polished by the flexible polishing process can be decreased by 18.7% and 57.3%, respectively, compared with those of the sapphire wafer polished by the rigid polishing process.
Highlights
With the development of light-emitting diodes (LEDs), single crystal wafers have been given much attention
It can be noticed that the atomic force microscope (AFM) image of the pre-machined sapphire wafer surface shows a large number of deep scratches on the wafer surface, which has a gloomy color in the AFM image
All this illustrates that the surface roughness polished by the flexible polishing plate is smoother than that polished by rigid polishing, which means that the wafer processed by the relatively soft polishing plate is helpful to reduce its surface roughness
Summary
With the development of light-emitting diodes (LEDs), single crystal wafers have been given much attention. Zhou et al studied the influence of different abrasive sizes on the material removal rate (MRR) and surface roughness of the sapphire wafer and proved that the superior polished surface quality can be obtained after polishing with smaller particle size.[11]. The high processing efficiency can be achieved by using fixed abrasive during sapphire wafer polishing,[16–18] a larger number of surface and sub-surface damages needs to be decreased With this in mind, flexible polishing has been reported as an ideal approach to satisfy the processing demands with scratch-free and nano-scale roughness for wafer manufacturing. Lu et al used sol–gel technology to disperse ultra-fine abrasive evenly in sodium alginate solution and solidified with Ca2+ solution to form a semi-fixed polishing plate for the mechanical polishing of single-crystal sapphire, single-crystal silicon carbide, and other photoelectric wafer materials to achieve nano-scale surface roughness.[21–23]. The surface characteristics, residual stress, MRR, and the wear debris produced during the processing, together with the yielding depth of abrasive particles, are analyzed
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