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-degrees-C. At all temperatures, SiH2Cl2 chemisorbs dissociatively forming silicon monochloride surface species. The coverage of monochloride displays a maximum for exposures at approximately 600-degrees-C. Under all conditions studied, larger chlorine coverages are observed on Si(100) than on Si(111). A Si surface that was first saturated with SiH2Cl2 at 600-degrees-C was subsequently exposed to H-2 at 600-degrees-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-degrees-C and Cl is removed via reaction with atomic H.