Defect and Diffusion Forum Vols. 230-232

Abstract: This paper presents a template-based vision system to detect and classify the nonuniformaties that appear on the semiconductor wafer surfaces. Design goals include detection of flaws and correlation of defect features based on semiconductor industry expert’s knowledge. The die pattern is generated and kept as the reference beforehand from the experts in the semiconductor industry. The system is capable of identifying the defects on the wafers after die sawing. Each unique defect structure is defined as an object. Objects are grouped into user-defined categories such as chipping, metallization peel off, silicon dust contamination, etc., after die sawing and micro-crack, scratch, ink dot being washed off, bridging, etc., from the wafer. This paper also describes the vision system in terms of its hardware modules, as well as the image processing algorithms utilized to perform the functions.

Abstract: A new model is developed for the Staebler-Wronski effect (SWE) in intrinsic a-Si:H. In this model, non-radiative recombination of the photogenerated carriers occurs at a weak bond close to a SiHHSi configuration, which allows a local creation of defect of the SiHD type. This defect can be annihilated by mobile hydrogen atom that has been emitted from an other distant SiHD defect as a result of non-radiative recombination at this defect site. In this study we have considered illumination intensities in the moderate and intense illumination range. In both cases, the proposed model reproduces many experimental features of the SWE known in the literature.

Abstract: The defects created in GaAs and AlxGa1-xAs epitaxial layers by impurity-free disordering (IFD) were studied by deep level transient spectroscopy (DLTS) and capacitance-voltage (C-V)measurements. IFD introduces three electron traps S1 (EC – 0.23 eV), S2* (EC – 0.53 eV), and S4 (EC – 0.74 eV) in n-type GaAs. We propose that S1 is a defect that may involve As-clustering or a complex of arsenic interstitials, Asi, and the arsenic-antisite, AsGa. S2* is the superposition of two defects, which may be VGa-related, while S4 is identified as the defect EL2. The same set of defects is created in impurity-free disordered n-type AlxGa1-xAs, but with the defects either pinned relative to the conduction band or the Fermi level. In contrast to disordering in n-type GaAs, IFD of p-type GaAs results in the pronounced atomic relocation of impurities, including Zn and Cu, in the nearsurface region of the disordered layer. The redistribution of these fast diffusers poses serious constraints regarding the application of IFD to the band gap engineering of doped GaAs-based heterostructures for optoelectronic devices application. However, we will demonstrate that this impurity segregation effect can be minimized. The discussion takes a critical look at the technological viability of impurity-free disordering for the integration of GaAs-based optoelectronic devices.