LOW-TEMPERATURE IN-SITU CLEANING OF SILICON(100) SURFACE BY ELECTRON-CYCLOTRON-RESONANCE HYDROGEN PLASMA

Low-temperature, defect-free, in situ cleaning of silicon prior to homoepitaxy is successfully developed by an electron cyclotron resonance hydrogen plasma treatment in an ultrahigh vacuum chamber. The plasma potential distribution was measured by a Langmuir probe method to understand the effect of the substrate dc bias during hydrogen plasma cleaning. It changes from downhill to uphill distribution as the dc bias changes from a negative to a positive value, which leads to a decrease in the ion number density arriving at the substrate and results in the complete suppression of the defect formation in the Si substrate. In situ hydrogen plasma cleaned Si wafer always resulted in higher quality epilayers than ones cleaned only by so-called hydrogen passivation after the HF dip. We found that there is a critical dose of the hydrogen ions during in situ plasma cleaning beyond which crystalline defects are observed in the Si substrate, subsequently leading to the poor crystallinity of the epilayers. The dose of the hydrogen ions during plasma cleaning can be effectively controlled by the substrate dc bias, the microwave power, the magnet current, and the cleaning time.