In order to fabricate terahertz sources at specific emission frequencies, the THz quantum cascade lasers are devices where emission frequencies can be tuned by varying thickness of quantum well and height of barrier. The THz QCL wafers are grown by using the molecular beam epitaxy (MBE) technique and processed into ridge waveguide structures by using a standard procedure of etching and processing. The technique is enabled for the growth of the ultra-thin semiconductor layers of the nano devices that gives the thickness control of the atomic scale. For high accuracy or design parameters like doping and layer thickness, the single atomic layer on the substrate is deposited in the ultra-high vacuum chamber. The present paper is a study of various components of a standard machine of molecular beam epitaxy techniques which is followed by details of processing of the wafers. In view of the recent advancement in fabrication and processing technology, THz QCLs can advance towards compact devices with improved performance.