CHARACTERIZATION OF A PECVD WXN PROCESS USING N-2, H-2, AND WF6

A novel plasma-enhanced chemical vapor deposition (PECVD) tungsten nit ride (WxN) process was developed on an Applied Materials Centura(TM) W xZ chamber. Nitrogen (N-2), hydrogen (H-2), and tungsten hexafluoride (WF6) are the active components for this PECVD process. Si substrate e ncroachment by WF6 can be suppressed by a N-2/H-2 plasma pretreatment before WxN deposition. Resistivity of WxN film decreases as H-2/WF6 ra tio increases and deposition temperature rises. A metrology technique using ellipsometry was used to measure the index of refraction and abs orption coefficient to quantify WxN thickness and stoichiometry. Depen ding on W to N ratio and process conditions, the index of refraction, n, at 433 nm was measured between 3.26 and 3.68 and the absorption coe fficient between 2.14 and 3.14. The resistivity of WxN with x = 0.7-2. 2 was measured between 1850 and 240 mu Omega cm on an as-deposited fil m. Step coverage, surface roughness, stress, and impurity content of t he amorphous films will also be reported. Feasibility of the in situ W /WxN stack deposition will be presented with the results to demonstrat e the capability for gate stack application. (C) 1998 Elsevier Science S.A. All rights reserved.