AVS 51st International Symposium
    Dielectrics Thursday Sessions
       Session DI+PS-ThA

Paper DI+PS-ThA9
Preparation and Properties of Clean Si@sub 3@N@sub 4@ Surfaces

Thursday, November 18, 2004, 4:40 pm, Room 304B

Session: Oxides on Semiconductors
Presenter: V.M. Bermudez, Naval Research Laboratory
Authors: V.M. Bermudez, Naval Research Laboratory
F.K. Perkins, Naval Research Laboratory
Correspondent: Click to Email
Si@sub 3@N@sub 4@ is an important material for use in electronic devices. Thin films of Si@sub 3@N@sub 4@ are used as passivation layers and diffusion barriers in IC's and as protective coatings in disk drives. However, the basic surface science of Si@sub 3@N@sub 4@ films has been impeded by the difficulty in obtaining a clean and undamaged surface. In this work, in-situ chemical methods for preparing atomically clean surfaces of Si@sub 3@N@sub 4@ thin films in UHV have been studied using XPS, UPS, ELS and AES. Prior to UHV studies, the thin films (grown ex situ on Si(100) by LPCVD) were characterized by IR reflection-absorption spectroscopy which showed them to be stoichiometric with a low H content. A two-step process consisting of annealing in a flux of NH@sub 3@ vapor to remove C and vapor deposition of Si (followed by thermal desorption) to remove O is found to be an effective cleaning procedure. Other potential cleaning methods, such as annealing in UHV without in- situ chemical treatment or annealing in a flux of H atoms, were considered and found to be only partly effective. The clean surfaces are disordered, as seen in LEED, but show no evidence of Si-Si bonding (which would indicate N vacancies) in the Si LVV AES or in surface-sensitive Si 2p XPS. Evidence for surface- related features is seen in the N 1s XPS and in ELS data in the region of valence excitations; however, no indication of occupied surface states near the valence band maximum is seen in UPS. Preliminary results for O@sub 2@ chemisorption show adsorbate- induced features in the band gap and also evidence for a reduction in the negative surface potential due to electron traps present on the clean surface.