Abstract
Silicon carbide (SiC) devices have become one of the key research directions in the field of power electronics. However, due to the limitation of the SiC wafer growth process and processing capacity, SiC devices, such as SiC MOSFET (Metal-oxide-semiconductor Field-effect Transistor), are facing the problems of high cost and unsatisfied performance. To improve the precise machinability of single-crystal SiC wafer, this paper proposed a new hybrid process. Firstly, we developed an ultrasonic vibration-assisted device, by which ultrasonic-assisted lapping and ultrasonic-assisted CMP (chemical mechanical polishing) for SiC wafer were fulfilled. Secondly, a novel three-step ultrasonic-assisted precise machining route was proposed. In the first step, ultrasonic lapping using a cast iron disc was conducted, which quickly removed large surface damages with a high MRR (material removal rate) of 10.93 μm/min. In the second step, ultrasonic lapping using a copper disc was conducted, which reduced the residual surface defects with a high MRR of 6.11 μm/min. In the third step, ultrasonic CMP using a polyurethane pad was conducted, which achieved a smooth and less damaged surface with an MRR of 1.44 μm/h. These results suggest that the ultrasonic-assisted hybrid process can improve the precise machinability of SiC, which will hopefully achieve high-efficiency and ultra-precision machining.
Highlights
In recent years, silicon carbide (SiC) devices have become one of the key research directions in the field of power electronics
MOSFET is a key element in modern microelectronics, which is widely used in highly integrated CMOS (Complementary Metal Oxide Semiconductor) and high-power devices
In addition to analyzing the above surface creation results, the material removal rates of the lapping experiments were calculated according to Equation (2)
Summary
Silicon carbide (SiC) devices have become one of the key research directions in the field of power electronics. Electrochemical mechanical polishing (ECMP) [8,9], plasma-assisted polishing [10,11], UV (ultraviolet) photocatalytic-assisted polishing [12,13], laser-induced assisted polishing [14,15], and Fenton oxidation-assisted polishing [16] were included In essence, these methods improved the oxidation corrosion performance of SiC by different external energies, which made the material easy to be removed. The surface quality after ECMP did not satisfy the requirements for electronic devices [19] It is well-known that ultrasonic-assisted technology has beneficial effects in fabrication [20]. This paper proposed a new hybrid process, which combined ultrasonicassisted lapping with ultrasonic-assisted CMP, to further improve the precise machinability of single-crystal SiC. An ideal surface with improved MRR was achieved
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