New dopant technique could accelerate next-generation semiconductor manufacturing
Researchers have successfully incorporated dopants into silicon carbide using a cleaner chemical process that eliminates unwanted silicon clusters. The advance clears a major hurdle for adoption in industrial production, though engineers must still solve uniformity challenges across larger manufacturing areas.
Originaltitel: Incorporation of dopants in epitaxial SiC layers grown with fluorinated CVD chemistry
Fluorerad CVD-kemi med SiF4 öppnar vägen för renare SiC-skikt, men dopantkontroll kräver ny förståelse innan tekniken kan industrialiseras. Forskare vid Linköpings universitet demonstrerar att dopering av epitaxiala SiC-lager lyckas med fluorerad CVD-kemi för både n-typ (kvävegasprecursor) och p-typ (aluminium, TMAl). Genom att justera C/Si-förhållandet kan man reglera dopningsnivåer på samma sätt som i konventionell SiC-CVD. Problemet ligger i dopantfördelningen över större ytor — fluorens starka bindningar med både kisel och aluminium förhindrar jämn incorporation. För SiC-tillverkare och leverantörer av epitaxiautrustning är resultaten kritiska: fluorerad CVD eliminerar gasbelagring av silikon men skapar nya utmaningar i processoptimering. Innan kommersiell adoption kan ske måste uniformitetsproblemen lösas, vilket förskjuter tidsplanen för denna nästa-generations CVD-kemi med år.
<p>Fluorinated chemistry in chemical vapor deposition (CVD) of silicon carbide (SiC) with SiF4 as Si precursor has been shown to fully eliminate the formation of silicon clusters in the gas phase, making SiF4 an interesting Si precursor. However, before a fluorinated CVD chemistry can be adopted, the effect of fluorine on the dopant incorporation must be understood since dopant incorporation is of paramount importance in semiconductor manufacturing. Here, the authors present dopant incorporation studies for n-type doping with N using N-2 and p-type doping with Al using TMAl in fluorinated CVD of homoepitaxial SiC. The precursors used were SiF4 as Si precursor and the source of F together with CH4 as C precursor. The authors find that it is possible to control the doping in SiC epitaxial layers when using a fluorinated CVD chemistry for both n- and p-type materials using the C/Si ratio as in standard SiC CVD. However, large area doping uniformity seems to be a challenge for a fluorinated CVD chemistry, most likely due to the very strong Si-F and Al-F bonds. (C) 2017 American Vacuum Society.</p>