Here we report the development of the primary nanometrology capacity at the National Metrology Institute of Brazil (INMETRO). An interference microscope of the Linnik type has been developed and subjected to optimization and characterization studies. The recording of the fringes is done by an automated CCD system with 2 possible processing approaches: interferometric pattern processing and the phase stepping technique. Current progress in the development of the hardware and software adequate for sub- nanometer resolution of the instrument is reported. A study of systematical errors of the interference microscope has been performed. The instrument is aimed for international key comparisons of step height standards.