Atomic layer epitaxy of silicon by dichlorosilane studied with core level spectroscopy

The chemisorption and reaction of dichlorosilane (SiH2Cl2 with Si(111) and Si( 100) surfaces is investigated with core-level soft x-ray photoelectron spectroscopy employing synchrotron radiation, in order to ascertain the surface chemistry involved in atomic layer epitaxy (ALE). Exposures to 8 kL of SiH2Cl2 were performed as a function of sample temperature in the range from room temperature to 800 °C. At all temperatures, SiH2Cl2 chemisorbs dissociatively forming silicon monochloride surface species. The coverage of monochloride displays a maximum for exposures at —600 °C. Under all conditions studied, larger chlorine coverages are observed on Si(100) than on Si(lll). A Si surface that was first saturated with SiH2Cl2 at 600 °C was subsequently exposed to H2 at 600 °C, and no reaction occurred. These results indicate that recent models for silicon ALE are incorrect. An alternative method for low-temperature ALE of Si is proposed, in which SiH2Cl2 is adsorbed onto Si at 600 °C and Cl is removed via reaction with atomic H. © 1992, American Vacuum Society. All rights reserved.