Langmuir, Vol.33, No.22, 5371-5377, 2017
Direct Dopant Patterning by a Remote Monolayer Doping Enabled by a Monolayer Fragmentation Study
The development of new doping methods extending beyond the traditional and well-established techniques is desired to match the rapid advances made in semiconductor processing methods and nanostructure synthesis in numerous emerging applications, including the doping of 3D architectures. To address this, monolayer doping (MLD) and monolayer contact doping (MLCD) methods were recently introduced. The monolayer doping methods enable separation of the doping process of nanostructures from the synthesis step, hence it is also termed ex-situ doping. Here we present a new ex-situ monolayer doping method termed remote monolayer doping (R-MLD). The non-contact doping method is based on the thermal fragmentation of dopant containing monolayers and evaporation processes taking place during annealing of the un-capped monolayer dopant source positioned in proximity, however, without making physical contact with the target semiconductor surface. We present a two-step anneal procedure that allows the study of the dopant monolayer fragmentation and evaporation stages and quantification of the doping levels obtained during each of the steps. We demonstrate the application of R-MLD for achieving large scale, direct patterning of silicon substrates with sharp doping profiles. The direct dopant patterning is obtained without applying lithographic processing steps to the target substrate. The non-contact doping process, monolayer decomposition and fragment evaporation were studied by thermogravimetric analysis coupled with mass spectrometry (TGA-MS), and sheet resistance measurements. The doped patterns were characterized by scanning electron microscopy (SEM), scanning capacitance microscopy (SCM) and time of flight secondary ion mass spectroscopy.