Growth of high-quality relaxed SiGe films with an intermediate Si layer for strained Sin-MOSFETs

Abstract

An intermediate Si layer in Si 1-x Ge x film, replacing the conventionally compositional graded buffer layer, was used to fabricate a relaxed SiGe substrate of high quality. The intermediate Si layer changes the relaxation mechanism of the SiGe thin film via the generation of {3 1 1} dislocation loops. The {3 1 1} dislocation loops are formed in the intermediate Si layer to prompt a state of relaxation in the SiGe overlayer, provide the defects for trapping of threading dislocations (TDs) and leave a SiGe top layer with low dislocation density. For the SiGe/Si/SiGe samples, the residual strain and TDs on the top SiGe layer are independent of the SiGe underlayer thickness. With a 700 nm thick Si 0.8 Ge 0.2 overlayer, such a Si 0.8 Ge 0.2 /Si/Si 0.8 Ge 0.2 heterostructure with a smooth surface has a TD density of 8.9 × 10 5 cm −2 and 3% residual strain. Owing to the different main relaxation mechanisms in SiGe films, the surface root mean square roughness of this relaxed buffer with a low density of surface pits was measured to be about 3 nm, which is lower than that of the sample without any intermediate Si layer (13 nm). Relaxation of the SiGe overlayer depends on the thickness of the intermediate Si layer. Optimization on relaxation in the SiGe/Si/SiGe structure with an intermediate Si layer of 50 nm is done. Strained Si n-channel metal-oxide-semiconductor field effect transistors with various buffer layers were fabricated and examined. The effective electron mobility for the strained Si device with this novel substrate technology was found to be 80% higher than that of the Si control device. The SiGe thin films with the intermediate Si layer serve as good candidates for high-speed strained Si devices. The global strain in the Si channel with a SiGe/Si/SiGe buffer is still beneficial for short channel devices.

Oxidation of RuAl and NiAl Thin Films: Evolution of Surface Morphology and Electrical Resistance

“…The roughness of the cosputtered films was not measured, but from the crosssectional TEM images, it is expected to be slightly higher than that of the annealed multilayer films. The film deposition was not optimized in order to decrease the roughness further, but even without optimization, these values are less than what is seen in the literature for SiGe films (1.8-5.4 nm rms) [55], [56]. Annealing of the multilayer samples prior to oxidation caused no significant change in the rms roughness for a multilayer with a 33-nm wavelength.…”

Processos alternativos para micro e nanotecnologia

“…Quando combinamos o silício e o germânio, o transistor pode funcionar mais rapidamente, podendo assim, criar circuitos de alta frequência [75][76][77][78][79]. Atualmente os filmes de silício germânio obtidos por epitaxia estão sendo altamente empregados como camadas relaxadas sobre substratos de silício em dispositivos MOS, na região de fonte e dreno e também em transistores bipolares.…”