Two-temperature technique for plasma-enhanced chemical vapour deposition growth of silicon-nitride on InP

Abstract

The high mobility and saturated drift velocity of electrons in InP make the insulator/InP structure very attractive for high speed circuit applications. Despite this potential, however, a number of troubling problems, such as high density of interface states, formation of poor dielectrics, electrical instability and lack of reproducibility, remain to be solved. The established deposition methods can not satisfy simultaneously the requirements for low density of interface states and good dielectric properties of insulator [1]. The newly proposed twotemperature deposition technique offers a possible way of solving this problem [2]. In this method, a thin interracial layer is formed at a low temperature, then the bulk insulator is deposited at a higher temperature. The value of this technique has been proven for the SiO2/Si system. To the best of our knowledge, however, the application of this technique to insulator/III-V semiconductor has not been reported. In this letter, we report on the results of the two-temperature technique applied to form an SIN,/ InP structure, where SiN, was produced by the plasma-enhanced chemical vapour deposition (PECVD) method. The electrical properties were characterized by multifrequency capacitancevoltage ( C V ) measurements, 1 MHz conductance-voltage ( G V ) measurements and quasi-static C V measurements. The optimum deposition temperature was found to be about 200 °C for the first thin SiN, deposition. The substrates employed in this study were undoped n-type (n--~ 5.0 x 1015 cm -3) (100) InP wafers (Nippon Mining Co.). The wafers were first cleaned in a standard organic solution (trichloroethylene, acetone and methanol). To remove any native oxide on the surface, they were then etched with acid solution (H2SO4:H202:H20 = 3:1:1) for 60 s. After rinsing in deionized water, they were dried by N2 gas blow. After blowing, the SiN, deposition process was initiated immediately in the PECVD chamber. The PECVD apparatus used was designed inhouse and the reactor was a capacitivelycoupled hot wall type [3]. Silicon nitride films were deposited from the gas mixture of dilute silane (5% Sill 4 in N2), ammonia (99.999%) and nitrogen