There is an increasingly demand for higher performing e-beam lithography machines. An important user requirement is the beam stability, this is dened for the short and long term. This thesis focuses on improving the beam stability with the use of a new metrology design. The e-beam machine has the potential to real-time correct for all correctly measured mechanical displacements, which makes the metrology a powerful tool in ensuring high beam stability. In the current system the main contributors to displacement measurement errors are vibrations and thermal drift present on/in the metrology system. These measurement errors decrease the beam stability. The proposed metrology design makes use of a differential displacement measurement between the electron optical column and the stage. This makes the displacement measurement almost insensitive to vibrations and thermal drift. The short term beam stability is improved from <5 nm to <3.5 nm and the long term stability is improved from <50 nm to <9 nm.