Control of interfacial oxide using a novel cluster tool technology

Improved control over the undesired oxidation of crystalline silicon surfaces during the steps preceding the polysilicon deposition process can be obtained through clustering of the final oxide removal step with the deposition. Experimental results indicate that the resistance of polysilicon contact structures can be reduced by using a clustered HF-vapor etch/polysilicon deposition sequence in place of conventional wet HF etching followed by polysilicon deposition. Such a process has been shown to reduce the resistance of 0.65 micrometer contacts by 40% relative to that of conventional processing. This improvement is a result of inhibiting the growth of native oxide and is attributed primarily to improved ambient control during the lending step at the beginning of the LPCVD process. Interactions between the settings of the HF-vapor etch process were found to further impact the process. Subsequent tests using polysilicon emitter transistors showed that the cluster tool process sequence resulted in better reproducibility of transistor gain and emitter resistance relative to the conventional process. Details of these experiments are reported