A methanol-last chemical treatment is investigated for application as an ultra-clean polysilicon/silicon interface in polysilicon emitter bipolar transistors. It is shown that the interfacial oxide thicknesses after methanol-last and HF treatments are approximately 1-2 and 6Å respectively. Similarly the carbon concentrations at the interface after the two treatments are 6x1012cm-2 and 5x1014cm-2 respectively. The interfacial layer produced after the methanol-last treatment is thin enough to allow complete (100%) epitaxial regrowth of the polysilicon to take place after an anneal of just 120s at 950°C. In contrast, only 0.5% of the polysilicon regrew for an HF-treated control sample even after an anneal of 300s at 950°C.