Mitsubishi Electric Corporation announced this week that it has developed a prototype multi-wire electrical discharge processing technology to cut very hard four inch square polycrystalline silicon carbide (SiC) ingots into 40 pieces at once. The technology is expected to improve both the productivity of SiC slicing and the effective use of SiC material. Mitsubishi Electric aims to market its multi-wire electrical discharge slicer by fiscal 2015.
SiC is expected to be used increasingly in power semiconductors due to its superior energy-saving and CO2 emissions-reduction properties compared to silicon. Additionally, SiC, along with GaN, zinc oxide (ZnO) and silicon (Si) substrates are considered as the future LED substrates, thanks to low lattice mismatches.
The prevalence of SiC in the semiconductor industry has grown over the past few years, as Si substrates are relatively cheap and benefit from the long process history of semiconductor manufacturing on Si. Currently, Cree is producing epi-wafers using a SiC substrate.
Until now, sliced wafers have been produced through multi-wire saw with diamond particles because SiC is the third hardest compound on earth, but this method requires lengthy machining time and large kerf widths. The new parallel multi-wire electrical discharge machining method utilizes Mitsubishi Electric’s proven electrical discharge technology for difficult-to-cut material, and employs a dedicated power supply specially developed for SiC.
Key technologies of Mitsubishi Electric’s electrical discharge technology
Mitsubishi Electric’s electrical discharge technology provides a method of simultaneously cutting of SiC ingots into 40 pieces. Forty wire electrodes with a diameter of 0.1 mm aligned at 0.6mm intervals are rotated to cut 40 slices at once, improving productivity. The non-contact, thermal process-wire electrical discharge method slices faster and at closer intervals compared to contact cutting (220 micro meters or less cut at a speed of 80 micro meters per minute). More wafer slices extracted per SiC ingot for improved efficiency.
The power supply dedicated to SiC slice processing allows for simultaneous wire cuts with even energy enabled by 40 electrically independent power feed contacts to wire electrodes. The power supply also means uninterrupted processing with even very thing (0.1mm) wire electrodes, thanks to a newly developed high-frequency power supply tailored to the characteristics of SiC material.