Dynamics of a pulsed DC discharge used for plasma-assisted chemical vapor deposition - a case study for titanium nitride deposition

An investigation of the development of a pulsed DC discharge used for plasm a-assisted chemical vapor deposition (PACVD) of titanium nitride was carrie d out in order to understand non-uniform depositions in larger PACVD system s. The temporal and spatial evolution of the plasma light emission was stud ied by a video camera. The time evolution of the plasma potential was studi ed by a single Langmuir probe and the discharge current by a current probe. In the presence of TiCl4 for formation of the discharge across the reactor is slow, reaching some parts of the reactor with substantial delay. Our exp eriments show that the development of the discharge depends on the geometry of the cathode, which includes loading and placement of the substrates, ga s mixture and waveform of the voltage supplied. The slow spreading of the d ischarge across the surface of the cathode, on which the substrates are pla ced, leads to a non-uniformity of plasma power density in front of the cath ode as well as to a spatially varying exposure time of the surface to the p lasma. The experiments revealed that the slow spreading of the discharge ca n be solved by measures which provide sufficient voltage for the cathode fa ll across the entire cathode surface whereby high average discharge All rig hts reserved. currents have to be avoided. (C) 1999 Published by Elsevier S cience S.A.