Laterally Confined Large-Grained Poly-GeSi Films: Crystallization and Dopant Activation Using Green Laser

Abstract

This paper reports crystallization with a pulsed Yb:YAG thin disk laser (λ = 515 nm) of amorphous Ge 0.85 Si 0.15 films approximately 100 nm thick, on silicon wafers with thermal oxide. Pre-patterned lines were employed to steer the crystallization and to form confined large grains. In total, 64% of the grains were longer than 2 μm, among them 40% were reaching 8-35 μm in length. These values, orders of magnitude larger than the layer thickness, were a result of so-called super-lateral growth. The grains were laterally confined within a 3 μm wide space. The crystallization led to a substantial residual tensile stress with a strain of 3.4%. Green-laser activation of BF 2 + , As + and P + implants was studied in amorphous and polycrystalline Ge 0.85 Si 0.15 films and led to successful dopant activation with resistivity values in the range of 5-20 m -cm achieved for all the implants.

Materials and integration schemes for above-IC integrated optics

“…In recent work [6] we showed the merits of green-laser GeSi crystallization for the formation of large crystal grains (much larger than the film thickness, see figure 2) and excellent impurity activation at low substrate temperatures. Following this approach, photodetectors with good signal to noise ratio may be fabricated with responsivity in the near-infrared spectral range, suitable for wavelength division multiplexing (WDMA) applications.…”

“…In this article we present investigations towards the integration of optical functions on top of CMOS. Materials for light detection as well as waveguiding are studied, expanding on our earlier publications [6,7]. We further present and compare integration schemes for these materials in the Above-IC context.…”

Fabrication and properties of GeSi and SiON layers for above-IC integrated optics

“…The process window was determined by systematically varying the process parameters (laser beam width, pulse energy, pulse overlap) and physical analysis of the samples, mostly by scanning electron microscopy, electron backscatter diffraction (EBSD) and sheet resistance measurements, as detailed in [12]. A typical EBSD image of the obtained polycrystalline material is shown in Fig.…”

“…Integrated light sources are beyond the scope of the present article. In this paper, materials for light detection as well as waveguiding are studied, expanding on our earlier publications [12,13]. This article provides additional background information and presents new data to support the choices made in process optimization.…”