Deposition, characterization, and device application of amorphous carbon and amorphous silicon films.

摘要

The purpose of this work is to develop an expertise of deposition of amorphous carbon (a-C) films, especially diamond-like carbon (DLC) films using various deposition systems, and to acquire better understandings of this material by various characterization techniques, and finally to study the feasibility of using this material as a new dielectric for Metal-to-Metal antifuse devices lo solve the switching problem of the amorphous silicon (a-Si) antifuses.;In this work, we report successful deposition of DLC films using a microwave electron cyclotron resonance (ECR) plasma system. We found that a-C:H films deposited without rf biasing are soft and polymer-like and have higher band gaps. DLC films can only be produced under a negative self-bias induced by the rf biasing. The band gap of the film decreases with the increase in rf power, and with the decrease in deposition pressure. This shows that the properties of the films depend mainly on the ion bombardment energy.;For a more in-depth investigation of amorphous carbon, a-C:H and its alloys (a-C:H,N,F) deposited using an rf plasma enhanced chemical vapor deposition (PECVD) system at the University of Arkansas were used. We have used infrared (IR), optical absorption, and continuous (cw) and time resolved photoluminescence (PL) to characterize these materials. We have calculated the normal mode vibrational frequencies of nitrogen and fluorine related modes using simple valence force field method. We also studied the effects of nitrogen and fluorine on the film's properties. Our optical absorption and PL data support the cluster model proposed by Robertson that a-C:H contains both sp;For this work, a-C:H and its alloys (a-C:H,N,F) were employed as potential dielectrics for the Metal-to-Metal antifuse development. We found that these new antifuses have several characteristics superior to a-Si antifuses including lower values of OFF-state leakage current, ON-state resistance, dielectric constant and breakdown voltage. Most importantly, these new antifuses do not show ON-OFF switching which is observed in a-Si antifuses. Finally a phase transition model is proposed to explain the breakdown mechanism and ON-state reliability in amorphous carbon antifuses.