A new approach to fabricating hemispherical cavity arrays on silicon (Si) substrate using laser-assisted nanoimprinting of self-assembled particles is presented. A monolayer of silica particles, with different diameters of 0.30 and 0.97 µm, was deposited on a Si substrate by self-assembly. A quartz plate was tightly placed on the sample surface to firmly sandwich the self-assembled nanoparticle monolayer. The silica particles were imprinted into Si substrates after laser irradiation (KrF excimer laser, λ = 248 nm) on the quartz/nanoparticle/Si structure with a single pulse. Ultrasonic cleaning and hydrofluoric acid (HF) solution were used to remove the silica particles in the sample surface. Hemispherical cavities were formed on the substrate surface. The influence of laser fluence and particle size on the structuring of the surface has been investigated. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were performed to observe the dimensions of the cavities. One-dimensional thermal calculation was employed to calculate the thermal effects in this process.

A high-quality thin gate oxide for application in Si/SiGe heterostructure PMOSFETs is prepared by nanometre silicon wet oxidation at 750 • C by taking full advantage of the peculiar phase in polysilicon thermal oxidation. The combination of low temperature and a short processing time prevents strain relaxation and Ge outdiffusion in the compressively strained SiGe channel. Its structural stability and interface quality are studied by x-ray double-crystal diffraction. Results of C-V characteristics and breakdown measurements indicate that the gate oxide exhibits a low fixed oxide charge density and a high dielectric breakdown field. Employing this gate oxide, Si/SiGe PMOSFETs with good output characteristics have been successfully fabricated.