VERY LOW DEFECT REMOTE HYDROGEN PLASMA CLEAN OF SI(100) FOR HOMOEPITAXY

We discuss a remote hydrogen plasma cleaning technique which is effective at removing carbon, nitrogen and oxygen from a silicon surface that has been pretreated with a wet chemical clean and a final dilute HF dip. It has been found that for best results, air exposure of the wafer after the HF dip must be minimized, as the ability of the H plasma clean to remove oxygen seems to be reduced on wafers which have been exposed to air for several hours. The atomic H supplied by the clean also results in different hydrogen terminated surface reconstructions depending on the substrate temperature. We observe a (1 × 1) RHEED pattern at clean temperatures below 190° C which is believed to be due to disordered silicon monohydride and dihydride termination, a (3 × 1) pattern between 200 and 280° C, corresponding to ordered monohydride and dihydride coverage, transitioning to a (2 × 1) pattern around 300° C due to monohydride termination. A dilute HF dip produces a (1 × 1) pattern due to disordered (3 × 1) cells, i.e. disordered monohydride and dihydride coverage. The passivating effects of the dilute HF dip and of the remote hydrogen plasma clean have also been discussed. The two processes have been found to result in similar hydrogen coverage of the wafer surface which in turn results in similar surface passivation. Both the dilute HF dip and the in situ remote H plasma clean have been found to protect the wafer from contamination for up to 15 min in ambient air and for an indefinite period under vacuum. © 1990 The Mineral,Metal & Materials Society,Inc.