Hydrogen Plasma Modification Study Of Metal/SiC Contact Interface

SiC has wide application in the field of high temperature, high frequency, high power and radioresistance because of its excellent physical and electronic characteristics, such as wide band gap, high breakdown electrical field and high thermal conductivity. But when it is used to devices, the quality of contacts between SiC and metal determines performance and realiability of devices, including Ohmic and Schottky contacts, so reaserch on metal/SiC contacts is of great interest. Schottky barrier is one of the key factors which determines the contact characteristic, and through adjusting it we can improve the contact performance.Based on classical metal-semiconductor contact barrier formation theory and key parameters of 4H-SiC, we construct the metal/4H-SiC barrier model to direct process improvements of contacts and help to evaluate modification results. In this model, the relation between Schottky barrier and interface density is clearfied, and it is found that in different field of metal workfunction, Schottky barrier height varies with interface states density in two kind of opposite trend:when metal workfunction is smaller than the key point, barrier drops as interface states decreases; when it is larger than the key point, this trend get reversed. We explained the phynominen using energy-band diagrams.Hydrogen plasma is used to treat Si-surface of 4H-SiC before Pt deposited on Si-surface and Ti deposited on C-surface. We usedⅠ-Ⅴand XPS mearments to analyze treated samples compared to those not treated. Results ofⅠ-Ⅴreveals the rectifying style obviously enhanced after hydrogen plasma treated and the barrier height raised from 1.25V to 1.73V, the interface states dcrease from 1.2×1013cm-2eV-1 to 1.6×1012cm-2eV-1. Results of XPS reveals Si2p spectrum moves after treatment and surface states reduced from 2.6×1013cm-2eV-1 to 1×1013cm-2eV-1.From the research results, it can be seen that hydrogen plasma treatment is a kind of effective surface treatment approach for SiC. By this mean we can reduce surface states density to adjust the barrier height of Pt/4H-SiC, and finally improve the rectifying characteristics.