Dual-photoresist complementary lithography technique consisting of inorganic oxide photoresist and organic photoresist is applied to produce the submicron pit array patterns on a sapphire surface. The oxide photoresist is patterned by direct laser writing, and the developed pit size decreases to a smaller value than the laser spot size due to the thermal lithography. The oxide photoresist possesses strong etching resistance against oxygen plasma but shows no resistance against chlorine plasma. During the ion-coupled-plasma reactive-ion-etching process, chlorine plasma is a necessary component to etch the sapphire. Moreover, the characteristics of organic resist are opposite those of oxide photoresist and possess moderate resistance against chlorine plasma but no resistance against oxygen plasma. The thermal and developing characteristics of oxide photoresist are reported in this study. The dependence of laser power on the developed mark sizes and morphologies is examined by atomic force microscopy. The temperature distribution on the photoresist structure during the laser writing is simulated, and the thermal lithography concept is introduced to explain the effect of power on the developed oxide mark width. Images of patterned pit array on a commercial 4-inch-diameter sapphire substrate are also shown.
Dual photoresist complimentary lithography technique consisting of inorganic oxide photoresist and organic photoresist is applied to produce the sub-micro pit patterns on a sapphire surface. The oxide photoresist is patterned by the direct laser writing and the developed mark size decreases to a smaller value than the laser spot size due to the thermal lithography. The small developed pit diameter is one of the advantages using oxide photoresist. The oxide photoresist possesses strong etching resistance against the oxygen plasma but shows no resistance against the chlorine plasma. The chlorine plasma is a necessary component to etch the sapphire during the ion-coupled-plasma reactive-ion-etching process because of sapphire’s mechanical hardness and chemical stability. However, the characteristics of organic resist SU8 are opposite to that of oxide photoresist and possess moderate resistance against chlorine plasma but show no resistance to oxygen plasma. The thermal and developing characteristics of oxide photoresist are reported here. The dependence of the laser power on the developed mark sizes and morphologies is illustrated by atomic force microscopy. The temperature distribution on the photoresist structure during the laser writing is simulated. Images of patterned pits on the large commercial sapphire substrates are also shown.
Ceramics are commonly used as substrates in electrically insulated integrated circuit, printed circuit board, and lightemitting
diode industries because of their excellent dielectric and thermal properties. However, brittle materials (e.q.,
ceramic alumina, sapphire, glass, and silicon wafer) are difficult to fabricate using wheel tools. Laser material processes
are preferred over traditional methods because they allow noncontact processing, avoid tool wear problems, and achieve
high speed, high accuracy, and high resolution. Laser material processes also exhibit minimal residual thermal effects
and residual stress. This study investigated the laser drilling of Al2O3 ceramic material (with a thickness of 380 μm and
hole diameters of 200, 300, and 500 μm, respectively) by using a laser milling method. The macro- and micro-hole
milling performance depended on various parameters including the galvanometric scan speed and milling time. A 3D
confocal laser scanning microscope and a field-emission scanning electron microscope were used to measure the surface
morphology, taper angle, and melted residual height of the machined surface after laser milling. The edge quality and
roundness of laser milling were also observed using image-processing edge-detection technology.
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