Advances in SiC Substrates for Power and Energy Applications
Since 2006, Dow Corning has executed several internal projects and DoD sponsored programs to develop manufacturing capability to produce 76-100 mm diameter 4H-SiC epiwafer products and qualify these products for power semiconductor applications. Over this period Dow Corning has leveraged its vertical materials integration capability to create a commercial SiC substrate supply chain based on the application of unique chemistries and materials integration strategies. Inherent to this effort are focus on specific product metric improvements to address the key materials issues specifically limiting the full performance advantages of SiC devices. Priorities included micropipes, epitaxy defects, carrier lifetime, crystal dislocations and thick epitaxy.
This paper will review the progress in product development of 4H-SiC substrates at Dow Corning. Thru continuous improvement efforts, epiwafer substrates of diameter 76-100 mm are now commercially available with micropipe defect density <0.1/cm2 and screw dislocation densities <2000/cm2. Wafer shape performance is consistent with the performance of silicon substrates and lithography technology. Epitaxial film substrates are produced in volume manufacturing with film thickness up to 25 um, in R&D with film thickness to 100 um, and with defect free area >85%. The epiwafers consistently exhibit basal plane defect density between 0-20/cm2 and carrier lifetimes on the order of microseconds. These metrics are key to realizing the performance of SiC in both unipolar and bipolar semiconductor devices.
This paper will also present examples of the use of epitaxial substrates in the fabrication of power diodes and transistors, such as Schottky diodes, JBS diodes, PiN diodes and bipolar junction transistors. State of the art device performance approaching the theoretical limits of SiC semiconductors have been achieved across the voltage range 1-5 kV. Collectively, the industry wide advances in SiC substrate quality are now such that costs of semiconductor devices based on SiC can become competitive with silicon power devices and establish the foothold for next generation power semiconductor technologies addressing the global industry energy roadmaps.
[Authors acknowledge support in part by ONR (Dr. P. Maki) and ARL (Dr. B. Geil).]