The influence of oxygen on single contact resistance studied by electron energy loss spectroscopy

Electron energy loss spectroscopy (EELS) on 16M dynamic random access memor y (DRAM) device structures is used to study locally the diffusion of oxygen in the physically vapor deposited (PVD)-Ti chemical vapor deposition (CVD) -TiN tungsten liner films. These results are correlated to the electrical c ontact resistance of 1000 tungsten contact chains on Nf silicon areas depen ding on different titanium thickness at the bottom of the contact hole and on the use of a liner anneal around 600 degrees C. It is shown that the loc al diffusion of oxygen tracked with the EEL spectroscopy is consistent with Auger analysis on blanked films and can explain the different electrical r esults of the 16 M DRAM devices. From this explanation it can be concluded that for a microelectronic processing application the use of CVD-TiN as the barrier in tungsten plug application with an air break between the PVD-Ti and CVD-TiN deposition is only acceptable if enough titanium is available t o buffer the oxygen from the native titanium oxide. (C) 1999 The Electroche mical Society. S0013-4651(98)12-018-9. All rights reserved.